Ackerman Et Al. (2013) - Alkaline Carb Metasomatism NEBavaria Xenol JPet

Alkaline and Carbonate-rich Melt Metasomatismand Melting of Subcontinental LithosphericMantle: Evidence from Mantle Xenoliths,NE Bavaria, Bohemian Massif

LUKA¤ S› ACKERMAN1,2*, PETR S› PAC› EK3,4, TOMA¤ S› MAGNA2,JAROMI¤ R ULRYCH1, MARTIN SVOJTKA1, ERNST HEGNER5 ANDKADOSA BALOGH6

1INSTITUTE OF GEOLOGY v.v.i., ACADEMY OF SCIENCES OF THE CZECH REPUBLIC, ROZVOJOVA¤ 269, CZ-165 00,

PRAGUE 6, CZECH REPUBLIC2CZECH GEOLOGICAL SURVEY, KLA¤ ROV 3, CZ-118 21 PRAGUE 1, CZECH REPUBLIC3INSTITUTE OF GEOPHYSICS v.v.i., ACADEMY OF SCIENCES OF THE CZECH REPUBLIC, BOC› NI¤ II, CZ-141 34, PRAGUE 4,

CZECH REPUBLIC4INSTITUTE OF EARTH PHYSICS, MASARYK UNIVERSITY, TVRDE¤ HO 12, CZ-602 00, BRNO, CZECH REPUBLIC5DEPARTMENT OF EARTH AND ENVIRONMENTAL SCIENCES, UNIVERSITA« T MU« NCHEN, THERESIENSTRA�E 41,

D-80333MU« NCHEN, GERMANY6INSTITUTE OF NUCLEAR RESEARCH, HUNGARIAN ACADEMY OF SCIENCES, BEMTE¤ R 18/C, DEBRECEN H-4026,

HUNGARY

RECEIVED JANUARY 29, 2013; ACCEPTED SEPTEMBER 20, 2013

Peridotite xenoliths hosted by Cenozoic basanite lava flows

(21·2^23·5 Ma) occur at several localities in the western continu-

ation of the Ohr› e/Eger rift (Central European Volcanic Province)in NE Bavaria, Bohemian Massif. Detailed petrography, major

and trace element compositions of whole-rock samples and selected

mineral phases as well as Sr^Nd^Li isotopic compositions for a

suite of mantle xenoliths from Zinst, Hirschentanz and Teichelberg

document variable degrees of partial melting and metasomatism.

Melting models based on whole-rock major element composition and

Cr# of spinel indicate �6^30% melting in the spinel stability

field. Subsequent metasomatism by alkaline and carbonate-rich

melts resulted in modal and cryptic metasomatism, expressed by the

presence of carbonate-bearing silicate melt pockets with complex sec-

ondary mineral assemblages and by enrichment in light rare earth

elements, Li, Rb, U, Pb, high field strength elements and P.The car-

bonate is most probably associated with fractionation of the Na-rich

silicate melt. High P contents, variable but low to negative d7Livalues from þ2·5 to �9·7ø, coupled with 87Sr/86Sr ratios between

�0·7032 and �0·7041 may reflect a significant contribution

of recycled crustal material such as eclogite in the infiltrating

melts responsible for metasomatism, although the Li isotope

compositions may reflect kinetic modifications through diffusion.

The trace element geochemistry of clinopyroxene, carbonate and

melt pockets suggests that clinopyroxene plays a very important role

in fractionation of the rare earth elements, high field strength elem-

ents and Sr, whereas carbonate does not host large quantities of in-

compatible trace elements except for Sr, Ba and, to a lesser extent,

Th and U.

KEY WORDS: peridotite; metasomatism; subcontinental lithosphere;

Sr^Nd^Li isotopes; microstructure

*Corresponding author. Telephone: þ420-233087240. Fax:þ420-220922670. E-mail address: [email protected]

� The Author 2013. Published by Oxford University Press. Allrights reserved. For Permissions, please e-mail: [email protected]

JOURNALOFPETROLOGY VOLUME 0 NUMBER 0 PAGES1^37 2013 doi:10.1093/petrology/egt059

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I NTRODUCTIONPeridotite xenoliths in volcanic rocks provide importantclues to the structural and chemical characteristics of thesubcontinental lithospheric mantle. A number of studieshave shown that the upper mantle sampled by spinel andgarnet peridotite xenoliths is variably enriched in incom-patible trace elements caused by infiltration of originallymelt-depleted peridotites by melts or fluids of differentcomposition, including those with basaltic and carbonatiticaffinities (e.g. Frey & Green, 1974; Menzies &Hawkesworth, 1987; Yaxley et al., 1991; Ionov et al., 1993;Downes, 2001; Pearson et al., 2004). Such mantle enrich-ment (metasomatism or mantle refertilization) may resultin precipitation of secondary clinopyroxene, amphibole,mica or apatite that are enriched in incompatible traceelements (e.g. Ionov et al.,1993,1997; Gregoire et al., 2000b).Cenozoic alkaline anorogenic volcanism forms several

important centres across Europe (Lustrino & Wilson,2007), including those in Spain (Iberia, Canary Islands,Madeira), France (Massif Central), Italy (e.g. Veneto vol-canic province, Sardinia), Germany (e.g. Kaiserstuhl,Eifel, Vogelsberg), the Czech Republic (e.g. C› eske¤Str› edohor› |¤ Mts., Doupovske¤ Hory volcanic complex),Slovakia, Hungary (Pannonian Basin), Serbia, Bulgariaand Macedonia (Rhodope Massif). In western and centralEurope, volcanic activity is associated with the develop-ment of the European Cenozoic Rift System (ECRIS)forming the Western and Central European VolcanicProvince (CEVP), which stretches from the MassifCentral in France through the Vosges and Schwarzwald(Black Forest) and Rhenish Massif to the BohemianMassif and Lower Silesia (Wilson & Downes, 1991;Lustrino & Wilson, 2007). The NE^SW-trending Ohr› e/Eger Rift system in the Bohemian Massif represents theeasternmost part of the continent-scale rift system withinthe CEVP (Fig. 1). Volcanic rocks from the Ohr› e riftsystem contain abundant mantle xenoliths, which recordmantle depletion by partial melting and subsequent enrich-ment by infiltration of basaltic melts at upper mantle con-ditions (Ackerman et al., 2007, 2012; Geissler et al., 2007;Puziewicz et al., 2011) and during exhumation in the hostbasalts (Puziewicz et al., 2011).Cenozoic volcanic rocks in the Upper Palatinate and

Upper Franconia volcanic fields (NE Bavaria, Germany)commonly contain mantle xenoliths. Some of these exhibitunique, fine-grained symplectites after garnet, recording acomplex history of interaction between garnet peridotiteand melts or fluids both prior to entrainment of the xeno-liths and during their ascent (S› pac› ek et al., 2013). Here, wepresent detailed petrographic descriptions, major andtrace element compositions of whole-rock samples andsingle minerals, and Sr^Nd^Li isotopic compositions for asuite of mantle xenoliths from Zinst, Hirschentanz andTeichelberg to assess the conditions of the origin and

history of the ambient subcontinental lithospheric mantle.The major and trace element data and Sr^Nd^Li isotopiccompositions and K^Ar ages for the host basalts are usedto discuss the possible relationship between the xenolithsand their host basalts. Our data suggest variable meltingdegrees in the spinel stability field and subsequent enrich-ment of the mantle protolith by alkali-rich melts resultingin both cryptic as well as modal metasomatism, the latterbeing evidenced by the presence of carbonate-bearingmelt pockets in some xenoliths. We argue that the sourceof the infiltrating melts is most probably mantle peridotite,but some contribution from recycled crustal material suchas eclogite is also possible.

GEOLOGICAL SETT ING ANDSTUDIED LOCAL IT I ESThe Bohemian Massif represents the largest relic of theEuropeanVariscan belt formed during the Devonian con-vergence and Carboniferous collision of Gondwana, Laur-ussia and intervening microplates (Franke, 2000; Matte,2001). This terrane collage is recorded in the mantle litho-sphere by domains with different seismic anisotropy (e.g.Babus› ka et al., 2008; Babus› ka & Plomerova¤ , 2010) correlat-ing with the major tectonic units of the BohemianMassifçthe Moldanubian, Tepla¤ ^Barrandian and Sax-othuringian units (e.g. Franke, 1989; Matte et al., 1990).Cenozoic volcanic rocks in the Bohemian Massif are

concentrated along major fault zones (grabens), formingone of the most prominent regions of the CEVP (Fig. 1).The western part of the Bohemian Massif, comprisingUpper Palatinate (NE Bavaria) and adjacent Saxony, rep-resents a prominent neotectonic mobile zone within centralEurope located at the junction of two volcano-tectoniczones, the Ohr› e Rift and the Cheb^Domaz› lice Graben(Ulrych et al., 2000). The southernmost part of the Ohr› eRift structure between the Doupovske¤ hory Mts. and theCheb Basin continuing up to the Franconian Line is char-acterized by abundant volcanic rocks, mostly of the basan-ite^olivine nephelinite series (Ulrych et al., 1999) of LateOligocene to Early Miocene age (29^19 Ma; Ulrych et al.,1999). Rare Plio-Pleistocene volcanism (2·0^0·26 Ma;Ulrych et al., 2011) of olivine melilitite to olivine nepheliniteoccurs at the junction of the Ohr› e and Cheb^Domaz› liceGrabens.The continuation of the Ohr› e Rift SWof the Cheb Basin

towards NE Bavaria lacks the asymmetric geometry withtwo marginal faults that is characteristic of its centralpart. The position of the Moho discontinuity and thicknessof the lithosphere in this area have been estimated at26^31km and �90 km, respectively (Geissler et al., 2007;Babus› ka et al., 2009). The Zinst locality (Zinster Kuppe:28·8 Ma, Todt & Lippolt, 1975; 25·6 Ma, Horn &Rohrmu« ller, 2005) comprises a basaltic volcanic breccia

JOURNAL OF PETROLOGY VOLUME 0 NUMBER 0 MONTH 2013

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and a relic nepheline basanite lava flow. These basanitestypically contain abundant peridotite xenoliths rangingfrom 3 to 10 cm in diameter, rarely up to 30 cm (Hucken-holz & Kunzmann, 1993). No pyroxenite or lower crustalxenoliths have been reported from this locality. TheHirschentanz Hill locality is the conduit of a 25m thicknepheline basanite lava sheet. Abundant xenoliths of peri-dotite as well as crustal xenoliths, mostly granitic in com-position, are present (Huckenholz & Kunzmann, 1993).Both the geology of Teichelberg Hill as well as the overallpetrographic and geochemical characteristics of the peri-dotite xenoliths are similar to those of Zinst (So« llner,1960).

ANALYT ICAL METHODSWhole-rock major element analyses were performed at theFaculty of Science, Charles University, Prague, by conven-tional wet chemical techniques. The accuracy and externalprecision of the method has been assessed by analysis ofperidotite PCC-1 (USGS) reference material and hasbeen reported by Ackerman et al. (2007).Whole-rock traceelement analyses were performed by inductively coupledplasma mass spectrometry (ICP-MS) using an Element 2sector field system (Thermo-Finnigan) housed at theInstitute of Geology v.v.i., Academy of Sciences CR,Prague. The precision of the analyses was better than 5%

Fig. 1. (a) Map showing the location of Variscan basement terranes and Neogene to Quaternary volcanism in western and central Europe[RH, Rhenohercynian; S, Saxothuringian; M, Moldanubian; modified from Franke (1989) andWilson & Downes (1991)]. (b) Simplified geolo-gical map of the Ohr› e/Eger Rift (modified from Christensen et al., 2001) showing the location of the studied localities in NE Bavaria (Zinst,Hirschentanz,Teichelberg).

ACKERMAN et al. MANTLE XENOLITHS, NE BAVARIA

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for all analyzed elements. Accuracy was monitored by re-peated analyses of UB-N reference material, which yieldsan average precision better than 15% relative (Supplemen-tary Data Table 1; supplementary material is available fordownloading at http://www.petrology.oxfordjournals.org)for all elements with respect to reference values (Govin-daraju, 1989).Trace element concentrations in clinopyroxene, carbon-

ate and quench melt were determined by laser ablation(LA)-ICP-MS at the Institute of Geology v.v.i., Academyof Sciences CR, using an Element 2 ICP-MS systemcoupled with a UP-213 NdYAG LA system (New WaveResearch), with analytical conditions as outlined byAckerman et al. (2012). The laser was fired at a repetitionrate of 20Hz and an output energy of 6^7 J cm^2. Linearlaser raster patterns of 100mm in length and with35^55 mm beam size were used for the analysis. The datawere calibrated against an external standard of syntheticsilicate glass, NIST SRM 612, using the recommendedvalues of Jochum et al. (2011) to calculate absolute concentra-tions of trace elements in the analysed grains.The accuracyof the analyses (Supplementary Data Table 2) was moni-tored by analysing soda-lime float glass NIST 1830 (0·1wt% Al2O3) compared with the published values of Flem &Be¤ dard (2002), Flem et al. (2002) and Berends-Monteroet al. (2006). The relative standard deviation (% RSD)ranged between 3 and 15% for all elements except Tm, Pband Ta, which had much poorer reproducibility (up to60%). The time-resolved signal data were processed usingthe Glitter software (van Achterbergh et al., 2001).Major element analyses of mineral phases in most of the

samples were carried out using a Cameca SX 100 electronmicroprobe coupled with wavelength-dispersive spectrom-etry (WDS) at the Institute of Geology v.v.i., Academy ofSciences CR, Prague, at an accelerating voltage of 15 kV,beam current of 20 nA, and a 2 mm beam. Synthetic andnatural mineral phases were used as standards for corres-ponding elements. Some samples were analysed also by aCameca SX 100 electron microprobe at the MasarykUniversity, Brno, using conditions described by S› pac› eket al. (2013).The Sr^Nd isotopic analyses of clinopyroxene separates

and host basalts were performed at the Universita« tMu« nchen according to the procedures outlined by Hegneret al. (1995). Prior to the analyses, the clinopyroxene separ-ates were leached at �708C in 6M HCl for 1h and subse-quently in 6M HNO3 for 1 h to remove possible grainboundary components. The 143Nd/144Nd and 87Sr/86Srratios of the clinopyroxene separates from peridotites weremeasured on a Triton thermal ionization mass spectrom-eter (ThermoFisher) in static data collection mode. TheJNd-1 standard yielded 143Nd/144Nd¼ 0·512095�8 andthe NIST 987 reference material yielded 87Sr/86Sr¼0·710246� 8. Strontium and Nd isotopic compositions of

the whole-rock basalt samples were measured on anupgraded MAT 261 in dynamic triple mass collectionmode. During these measurements, the JNd-1 standardyielded 143Nd/144Nd¼ 0·512113�8 normalized to146Nd/144Nd¼ 0·7219 (Wasserburg et al., 1981). The refer-ence materials NIST 987 and BCR-1 yielded 87Sr/86Sr of0·710224�10 and 0·704988�7, respectively (normalizedto 86Sr/88Sr¼ 0·1194). The long-term reproducibility of Srand Nd isotopic ratios for the reference materials mea-sured on both instruments overlaps, therefore no add-itional inter-laboratory instrumental bias correctionwas applied. The eNd values were calculated with theparameters of Bouvier et al. (2008) with present-day147Sm/144Nd¼ 0·1960 and 143Nd/144Nd¼ 0·512630 for thechondritic uniform reservoir (CHUR).The analytical procedures for lithium (Li) isolation and

purification by means of cation-exchange chromatographywere performed at the Czech Geological Survey and fol-lowed methods outlined by Magna et al. (2004, 2006).Lithium isotopic compositions were measured with aNeptune multiple-collector (MC)-ICP-MS system housedat the Czech Geological Survey, Prague, Czech Republic,using L4 and H4 Faraday cups for simultaneous collectionof 6Li and 7Li, respectively. Bracketing with the L-SVEC(Flesch et al.,1973) reference solution was applied to correctfor instrumental mass bias (Magna et al., 2004). The inter-national reference rock materials JP-1 (peridotite; GSJ),BHVO-2 (basalt) and DTS-2B (dunite; both USGS) wereused to monitor the precision and accuracy of the analyt-ical procedure. Their resulting d7Li values were 3·81�0·39ø (n¼ 5), 4·51�0·08ø (n¼ 4) and 7·39� 0·10ø(n¼ 3), respectively; d7Li is calculated as d7Li (ø)¼(7Li/6Lisample/

7Li/6LiL-SVEC ^ 1)� 1000 and all errors aregiven as 2s. A replicate measurement of JP-1, comprisingnew dissolution, full analytical procedure and isotopemeasurement yielded d7Li of 3·74� 0·34ø (n¼ 4). Thesedata are in full agreement with published values (Zacket al., 2003; Magna et al., 2006, 2008; Penniston-Dorlandet al., 2012).K^Ar dating was carried out at the Institute of Nuclear

Research of the Hungarian Academy of Sciences,Debrecen, Hungary, using procedures described byBalogh (1985). In brief, samples were crushed to �0·3^0·1mm and split into two parts: one part was used for Ardetermination and the other was pulverized for K abun-dance determination. Argon concentration was deter-mined after Ar extraction by high-frequency inductionheating in a vacuum system at 1300^15008C. Prior to gasextraction, a 38Ar spike was introduced into the extractionline. Argon isotopic composition was measured on a 908deflection, 150mm radius magnetic sector-type mass spec-trometer at the Institute of Nuclear Research. The concen-tration of K was determined by flame photometry.Potassium and Ar abundance determinations were


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calibrated against inter-laboratory standards LP-6, HD-B1and Asia 1/65 as well as atmospheric Ar. The error (1s) ofthe K^Ar determinations is based on the long-term instru-ment stability. A 3% error was assigned to the K concen-tration, including a 1% uncertainty of the standards. Theerror of the 38Ar spike was 2% whereas the error of themeasured isotopic ratios was 1%, including a possible frac-tionation in the extraction line. Data handling and plot-ting were performed using the GCDkit software(Janous› ek et al., 2006).

MANTLE XENOLITHSTexture and modal compositionThe xenoliths from Zinst, Hirschentanz and Teichelberg(mostly 3^10 cm in diameter) are dominated by coarse-granular varieties with millimetre-sized grains. The tex-tures are rarely well equilibrated, with olivine displayinga non-unimodal grain-size distribution and variable grainshapes. Rare transitions to high-strain, porphyroclastictextures in some xenoliths suggest late deformation. Somecoarser-grained xenolith types host unusual, high aspectratio tabular grains of olivine with straight crystal faces.The coarse-grained, complex symplectitic intergrowths ofpyroxene with spinel, frequently observed at other local-ities in the Bohemian Massif (e.g. Medaris et al., 1999;Matusiak-Malek et al., 2010), are mostly absent. However,a specific group of xenoliths from Zinst hosts other typesof plagioclase-bearing spinel^pyroxene symplectites withmuch smaller grain size, complex structures and severalstructurally distinct concentric zones. These symplectiteswere described in detail by S› pac› ek et al. (2013) and inter-preted as pseudomorphs after garnet, indicating a complexpressure^temperature and chemical evolution. In thisstudy, only one sample of this type (ZIN14) is included.The xenolith samples studied can be grouped into three

main textural types based on their olivine grain-size distri-bution and grain shape (Fig. 2, Table 1), as follows.Type 1 peridotites with equigranular to weakly inequi-

granular olivine of average grain size �1^2mm in diam-eter (10ZIN1-6, ZIN11, ZIN14, ZIN19, ZINx5, HIR3-6,HIR16; Fig. 2a). Samples with strain-free olivine predomin-ate over those with moderately strained olivine. Olivinetypically exhibits irregular, curvilinear grain boundaries.Samples with partly equilibrated grain boundaries(straight boundaries and 1208 triple junctions in somegrains) are rare. Sample ZIN14 containing fine-grainedspheroidal spinel^pyroxene symplectite with interstitialplagioclase hosted in pyroxene-rich domains (0·5^2mmlarge) is classified as a Type 1a xenolith. Coarse-grainedsymplectitic intergrowth of pyroxene with spinel wasfound in a single sample from Zinst (10ZIN1,Type 1b).Type 2 peridotites show abundant, small (0·2^0·5mm),

strain-free olivine neoblasts at grain boundaries oflarger (1^5mm), weakly to moderately strained grains of

olivine, and strain-free grains of pyroxene (porphyroclastictypes; ZIN9 and ZINx2; Fig. 2b). In these samples, micro-structural relations suggest that the olivine neoblasts wereformed by grain-size reduction by dynamic recrystalliza-tion and later probably affected by a static growth.

Fig. 2. Photomicrographs showing the typical textures of the NEBavaria mantle xenoliths. (a) Type 1, medium-grained, equigranularto slightly inequigranular lherzolite with curved olivine^olivine andlobate orthopyroxene grain boundaries (sample HIR 6). (b) Type 2,‘porphyroclastic’ texture with finer olivine neoblasts in grain bound-ary regions of coarser, strained phases (sample ZIN9). (c) Type 3,medium-grained lherzolite with preferentially elongated tabular oliv-ine grains (sample ZINx8). Grains with lobate boundaries areorthopyroxene.


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Type 3 peridotites contain high-aspect ratio strain-freetabular grains of olivine with semi-planar-parallel faces.In samples TEI2B and ZIN27 both tabular grains andmoderately strained grains with irregular or curvilineargrain boundaries are present (Fig. 2c). In contrast, sampleZINx8 contains only strain-free grains. The aspect ratio ofthe tabular grains is typically 3^4 and exceeds a value offive in some strained grains. Strong shape-preferred orien-tation is observed in equigranular (1^2mm) samplesZIN27 and ZINx8, whereas in inequigranular sampleTEI2B randomly oriented tabular grains, up to 2·5 cm insize, are hosted in a finer-grained (0·5^5mm) matrix.Neither amphibole nor phlogopite was observed in the

samples, which is consistent with previous observations onmantle xenoliths from the BohemianMassif (e.g. Ackermanet al.,2007;Matusiak-Malek et al.,2010; Puziewicz et al.,2011).Whole-rock major element compositions were inverted

using the least-squares inversion method of Albare' de(1995) to four-phase, Ol^Opx^Cpx^Spl modal compos-itions, using their average mineral compositions in thegiven sample (Table 1). However, for samples ZIN11 and

ZIN14 relatively large errors are expected, taking into ac-count the presence of carbonate-bearing melt pockets andanorthite-bearing symplectites. In general, the modal com-position of the xenoliths from the three studied localitiesis broadly similar. Of the 20 samples studied, 13 are spinellherzolites with variable (�6^13wt %) clinopyroxene con-tents, whereas six samples are harzburgites or transitionalharzburgite^lherzolite (�3^6wt % clinopyroxene); onesample (ZIN27) exhibits a transitional compositionbetween dunite and wehrlite (Fig. 3). Spinel contents in allsamples are low and olivine and clinopyroxene abundancesare negatively correlated.

Melt pocketsIn addition to the primary mineral assemblages, manysamples host a significant amount of variably shapedpatches filled by aggregates of finely crystallized mineralsand glass, clearly formed by quenching of a liquid phase,hereafter referred to as ‘melt pockets’. These features,described briefly by S› pac› ek et al. (2013), occur as eithervariably shaped, up to several millimetres diameter,rounded domains hosted in peridotite, or irregular patches

Table 1: Summary of main petrographic features and modal compositions of NE Bavaria mantle xenoliths

Sample Locality Textural

type

Carbonate-bearing

melt pockets

Lithology Bulk modal composition (wt %) Bulk Mg#

ol opx cpx sp

10ZIN1 Zinst 1b – lherzolite/harzburgite 80 13 6 1 91·4

10ZIN2 Zinst 1 – lherzolite 80 12 7 1 91·1

10ZIN3 Zinst 1 – harzburgite 84 12 3 1 91·2


10ZIN5 Zinst 1 – harzburgite/lherzolite 81 15 4 51 91·1


ZIN9 Zinst 2 – lherzolite 63 25 11 1 90·5

ZIN11 Zinst 1 x lherzolite 67 18 12 3 89·8

ZIN14* Zinst 1a x lherzolite 55 29 13 3 87·0

ZIN19 Zinst 1 – lherzolite/harzburgite 80 14 6 51 91·7

ZIN27 Zinst 3 – dunite–wehrlite 89 2 7 2 90·7

ZINx2 Zinst 2 – lherzolite 72 16 10 2 89·8

ZINx5 Zinst 1 – lherzolite/harzburgite 86 8 5 1 91·8

ZINx8 Zinst 3 – lherzolite/harzburgite 76 19 5 51 91·2

HIR3 Hirschentanz 1 – lherzolite 60 27 12 1 91·2

HIR4 Hirschentanz 1 – lherzolite/harzburgite 82 10 6 2 91·4



HIR16 Hirschentanz 1 – lherzolite/harzburgite 79 15 6 51 91·1

TEI2B Teichelberg 3 x lherzolite/harzburgite 82 11 5 2 91·1

GPS coordinates for the studied localities: Zinst 49854’08"N, 11856’35"E; Hirschentanz 49859’26"N, 12811’56"E;Teichelberg 49857’21"N, 12809’57"E. ol, olivine; opx, orthopyroxene; cpx, clinopyroxene; sp, spinel. (See text for explan-ation of textural types.) Bulk Mg#¼ 100[Mg/(Mgþ Fetot)].*Sample ZIN14 contains garnet pseudomorphs (S› pac› ek et al., 2013).


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in fine-grained symplectites after garnet, or grain bound-ary veinlets. Whereas some of these pockets are clearlylinked to the host basanite, some other, less abundant pock-ets are apparently isolated, located far from xenolith mar-gins and without feeder channels. The two types ofpockets with different structural and chemical features arevery similar to those described by Zinngrebe & Foley(1995) from Eifel mantle xenoliths. Similar to the classifica-tion scheme used by those researchers, the former type ofpockets clearly associated with the host basanite are herereferred to as Type I and the latter, which represent thefocus of this study, asType II.Based on their composition, two main varieties of the

Type II pockets can be distinguished: (1) carbonate-freesilicate melt pockets, which are most common; (2) rela-tively rare composite carbonate^silicate pockets. Thesetwo varieties of pockets are described separately below,but many features of the silicate domains are commonto both varieties as, for example, documented by back-scattered electron (BSE) images of the compositepockets in Fig. 4.

Silicate pockets

The silicate melt pockets have a glassy appearance underthe optical microscope. Scanning electron microscope(SEM) and cathodoluminescence (CL) images reveal thepresence of small (55 mm) feldspar grains with slight com-positional zoning within a micrometre-sized quench,which sometimes dominates the pockets. The local pres-ence of strictly amorphous glass was not tested, but seemsto be likely, based on compositions and substructure.Small (typically 3^30 mm) grains of clinopyroxene(cpx 2), and sometimes olivine (ol 2) and spinel are oftenclearly visible within an apparently homogeneous matrix.

These grains are mostly rounded, oval-shaped or vermicu-lar (Fig. 4b, c and f). In the case of clinopyroxene, thesmall grains are sometimes linked to relics of larger grains(if present) with undulating margins and complicated em-bayments, sometimes clearly derived from resorbed pri-mary clinopyroxene (Fig. 4c). Orthopyroxene also exhibitsundulating boundaries when in contact with the meltpockets, but it is not usually associated with a largenumber of small isolated grains in the matrix comparedwith clinopyroxene (Fig. 4b). Spongy or sieve-texturedspinel clusters are often found within the fine-grainedquench, often exhibiting homogeneous cores, representingprimary spinel grains (Fig. 4d^f). Larger, euhedral micro-phenocrysts are usually absent in carbonate-free pockets.

Carbonate^silicate pockets

The composite carbonate^silicate pockets often exhibit amore or less well-developed core^rim structure with a car-bonate zone in the core and a silicate zone forming therim (e.g. Fig. 4a and e). In addition to pocket cores, car-bonate is present in variable amounts as small irregulardomains within the silicate zone (Fig. 4a^f). The silicatezone is sometimes reduced to a thin film forming the mar-gins of pockets, but is always present. The structure of thesilicate zone is similar to that in carbonate-free pocketsconsidering its fine-grained quench with feldspar andoften small rounded grains of clinopyroxene and olivineas well as the sieve- or spongy-textured spinel. Unlike inmost carbonate-free pockets, some composite pockets con-tain larger subhedral to euhedral phenocrysts of olivine orclinopyroxene as well as other less common phases thatare hosted in the fine-grained matrix (Fig. 4d^f). The car-bonate zone is dominated by a very fine-grained aggregateof carbonate grains with a grain size below the resolutionof the optical microscope. The fine-grained carbonatehosts euhedral or subhedral microphenocrysts of olivine,clinopyroxene, orthopyroxene and feldspar, and subsidiaryphases apparently isolated or growing from walls of thezone (Fig. 4b and d^f). It is evident from BSE and CLimages that the composition of the carbonate often variessignificantly, both between two neighbouring pockets andwithin a single pocket (Fig. 4a, b and d).In this study, three samples containing melt pockets

were analyzed in detail, representing the three main typesof carbonate^silicate pocket, as follows.Spinel lherzolite sample ZIN14 hosts 50^800mm diam-

eter irregular pockets (Fig. 4a) in fine-grained orthopyrox-ene^spinel symplectites pseudomorphing garnet (S› pac› eket al., 2013). The carbonate zone that dominates in somepockets hosts olivine crystals with well-developed crystalfaces growing from the margin of the silicate zone. Thesilicate zone is devoid of phenocrystsçonly partlyresorbed pyroxene and spinel are present (Fig. 4b and c).Small-scale intermingling of carbonate domains with thesilicate zone in complex geometrical relations is common.

Fig. 3. Ternary Ol^Opx^Cpx diagram showing the modal compos-itions of the NE Bavarian mantle xenoliths.


7

Fig. 4. Back-scattered electron (BSE) images showing the morphology of the silicate^carbonate melt pockets. ol, olivine; opx, orthopyroxene;cpx, clinopyroxene; spl, spinel; afs, alkali feldspar; cb, carbonate; ilm, ilmenite; ap, apatite; quench, fine-grained aggregate with quenched crys-tals of feldspar and small grains of cpx and ol, possibly containing glass. (a) Complexly shaped chain of pockets with alternating silicate and car-bonate zones hosted in fine-grained orthopyroxene^spinel symplectite pseudomorphing garnet, sample ZIN14. Part of the pocket is outlinedfor clarity. (b) Detail of melt pocket in orthopyroxene^spinel symplectite, sample ZIN14 (modified from S› pac› ek et al., 2013). Noteworthy featuresare the euhedral olivine and intimate association of carbonate with quenched silicate melt, and the compositional difference of the carbonatesindicated by their different BSE greyscale in (a) and (b). (c) Melt pocket located at the margin of a primary clinopyroxene grain, sampleZIN14. The partly resorbed pyroxene and related small rounded grains in a glassy matrix should be noted. (d) Melt pocket in sample TEI2B.The similar structure and mineral composition of the phenocrysts (cpx, Mg-ilm) in both carbonate (upper left) and silicate (lower right)zones should be noted. (e) Carbonate-dominated core of a spheroidal melt pocket in sample ZIN11. The drusy arrangement of feldspar crystals,euhedral microphenocrysts of cpx and irregular grains of quartz in microcrystalline carbonate matrix should be noted. (f) Detail of a meltpocket in ZIN11. The sieve-textured reaction rim of primary spinel and association of carbonate domains with apatite and Mg-ilmeniteshould be noted.

(continued)


8

Lherzolite sample TEI2B hosts41mm diameter, simplepockets (Fig. 4d). The imaged pocket has a non-concentricstructure with a dominant silicate zone. Both the carbon-ate and silicate zones host subhedral phenocrysts of clino-pyroxene (cpx 2çpartly skeletal) and needle-shapedilmenite. Spinel exhibits sieve-textured reaction rimswhen in contact with the pocket.Sample ZIN11 (a lherzolite with a large number of

grain-boundary silicate and carbonate veinlets and fluidor melt inclusions) hosts 3^6mm diameter spheroidalpockets with dominant silicate zones and well-developedcarbonate cores (Fig. 4e). The silicate zone hosts numerouslarger, subhedral phenocrysts of olivine and rare ilmeniteand zoned spinel with a sieve-textured reaction rim in afine-grained matrix. Small, rounded clinopyroxene grains(cpx 2) are common in the matrix, similar to sampleZIN14 and the carbonate-free pockets described above.Carbonate hosts euhedral microphenocrysts of clinopyrox-ene and zoned needle-shaped orthopyroxene (opx 2,Fig. 4e), ilmenite (Ilm), rutile, apatite (Ap; sometimeswith quasi-spherical habit), crichtonite group (Ti^Zr-richoxide) minerals (C-rich), and irregular quartz (Qtz)grains. One particular large carbonate pocket has ageode-like appearance with radially oriented crystals ofalkali feldspar growing from its margin (Fig. 4e).

Whole-rock major and trace elementgeochemistryThe major element compositions of the studied xenolithsare presented inTable 2. Except for two carbonate-bearingxenoliths (ZIN11, ZIN14), the major element composition ofall the samples is characteristic of a variably melt-depleted

mantle assemblage with Mg# between 89·8 and 91·7,Al2O3 contents between 0·89 and 1·95wt %, low TiO2

contents of 0·01^0·14wt % and variable but high Cr con-tents between �1320 and 3970 ppm. The ZIN27 dunite^wehrlite differs from the other samples in having a lowSiO2 content of 40·7wt %. A negative correlation is ap-parent between MgO and SiO2, Al2O3, CaO and Na2Ofor most samples (Fig. 5). This feature has also been recog-nized in other mantle-derived rocks worldwide (Bodinier& Godard, 2004; Pearson et al., 2004) including those sam-pling the European subcontinental lithospheric mantle(Downes, 2001). In contrast, all NE Bavarian xenoliths arevariably enriched in P2O5 (0·02^0·29wt %; Table 2)when compared with the primitive upper mantle (PUM,0·02wt %; McDonough & Sun, 1995). Two carbonate-bearing xenoliths (ZIN11, ZIN14) exhibit lower Mg#s of89·8 and 87·0, respectively, and have the highest Al2O3

(�2·7wt %), CaO and Na2O contents (3·2^4·0 and0·29^0·57wt %, respectively) of the whole xenolith suiteat a given SiO2 content. With the exception of one refrac-tory harzburgite (10ZIN3), the Ca/Al ratios for the xenolithsuite vary from 1·3 to 2·5; thus, they are higher than thatof PUM (�1·1; McDonough & Sun, 1995). The K2O con-tents of the xenolith suite are rather low (50·10 wt %)except for sample ZIN11with 0·26wt %.Trace element concentrations in whole-rock samples are

presented in Table 2 and their primitive-mantle normal-ized distributions are shown in Fig. 6. All NE Bavariaxenoliths show slight to large enrichments in the light rareearth elements (LREE) relative to heavy REE (HREE),with PUM-normalized LaN/YbN ratios between 2·9 and23. The highest REE contents are found in the carbonate-

Fig. 4. Continued


9

Table 2: Whole-rock major and trace element compositions of NE Bavaria mantle xenoliths

Sample: 10ZIN1 10ZIN2 10ZIN3 10ZIN4 10ZIN5 10ZIN6 ZIN9 ZIN11 ZIN14 ZIN19

Rock: lherz lherz harz lherz lherz lherz lherz lherz lherz lherz

wt %

SiO2 42·36 42·74 42·18 43·54 42·76 42·91 44·26 42·14 43·92 42·48

TiO2 0·01 0·02 0·06 0·06 0·03 0·07 0·04 0·18 0·10 0·09

Al2O3 1·18 1·19 1·11 1·95 1·08 1·49 1·89 2·75 2·69 0·89

Fe2O3 2·08 2·07 1·69 1·79 1·92 2·06 2·43 2·36 3·94 1·88

FeO 5·52 5·78 6·28 5·83 6·09 5·99 5·32 5·73 5·93 5·48

MnO 0·12 0·11 0·11 0·11 0·11 0·12 0·11 0·12 0·12 0·12

MgO 44·17 43·69 45·45 40·84 44·65 41·37 39·94 38·95 35·47 44·34

CaO 1·37 1·78 0·85 2·85 1·17 2·37 2·36 3·22 4·04 1·28

Na2O 0·10 0·13 0·01 0·32 0·13 0·17 0·08 0·57 0·29 0·06

K2O 0·03 0·04 0·04 0·10 0·09 0·07 0·01 0·26 0·04 0·01

P2O5 0·02 0·03 0·24 0·04 0·03 0·06 0·17 0·26 0·18 0·25

H2O– 0·46 0·54 0·44 0·48 0·48 0·42 0·60 0·54 0·52 0·65

H2Oþ 0·08 0·75 0·24 0·53 0·21 0·43 1·54 0·94 1·11 1·20

CO2 2·20 0·75 0·95 1·11 0·96 1·97 0·44 1·12 1·12 0·58

Total 99·70 99·62 99·65 99·55 99·71 99·50 99·19 99·14 99·47 99·31

ppm

Cr 1323 2226 2349 2275 1427 2698 2208 3267 2676 1901

Ni 2361 2208 2298 1907 2201 1955 1797 1630 1333 1812

Rb 1·8 1·9 1·7 2·2 2·4 3·6 3·7 6·4 0·6 2·4

Sr 13 27 29 44 16 141 30 113 114 32

Y 0·21 0·27 0·34 0·69 0·22 0·46 0·78 1·74 0·43 0·60

Zr 3·1 3·7 5·6 11 3·8 9·3 21 19 9·7 12

Nb 1·2 1·6 1·3 2·3 1·2 3·9 1·8 4·8 0·51 2·2

Cs 0·052 0·033 0·056 0·071 0·085 0·197 0·013 0·025 0·007 0·013

La 0·541 0·208 0·687 1·30 0·488 1·55 0·531 3·12 0·383 1·16

Ce 1·13 0·763 1·45 3·02 1·06 2·83 1·33 6·17 0·907 2·56

Pr 0·099 0·114 0·151 0·370 0·113 0·290 0·194 0·695 0·111 0·287

Nd 0·353 0·580 0·609 1·63 0·462 1·11 0·99 2·79 0·515 1·21

Sm 0·051 0·126 0·117 0·318 0·082 0·186 0·240 0·530 0·122 0·244

Eu 0·017 0·038 0·045 0·102 0·025 0·061 0·082 0·186 0·046 0·083

Gd 0·058 0·105 0·123 0·301 0·085 0·199 0·228 0·573 0·127 0·259

Tb 0·006 0·014 0·017 0·040 0·011 0·024 0·035 0·079 0·020 0·036

Dy 0·029 0·064 0·081 0·174 0·051 0·105 0·182 0·387 0·104 0·163

Ho 0·005 0·011 0·015 0·030 0·009 0·018 0·034 0·072 0·020 0·028

Er 0·020 0·033 0·042 0·086 0·030 0·055 0·105 0·215 0·058 0·080

Tm 0·003 0·005 0·006 0·010 0·004 0·007 0·015 0·027 0·007 0·010

Yb 0·022 0·031 0·035 0·065 0·030 0·045 0·102 0·181 0·052 0·061

Lu 0·005 0·005 0·005 0·009 0·005 0·007 0·017 0·027 0·008 0·009

Hf 0·08 0·07 0·13 0·31 0·08 0·21 0·43 0·42 0·27 0·28

Ta 0·03 0·06 0·09 0·39 0·08 0·32 0·14 0·31 0·04 0·14

Pb 1·2 b.d. 1·3 0·6 2·0 2·3 0·64 0·49 0·22 0·34

Th 0·071 0·039 0·115 0·125 0·085 0·101 0·058 0·175 0·054 0·066

U 0·065 0·088 0·065 0·110 0·092 0·231 0·135 0·136 0·023 0·059

Mg# 91·4 91·1 91·2 90·7 91·1 90·4 90·5 89·8 87·0 91·7

(continued)


10

Table 2: Continued

Sample: ZIN27 ZINx2 ZINx5 ZINx8 HIR3 HIR4 HIR5 HIR6 HIR16 TEI2B

Rock: dun–wehr lherz harz harz lherz lherz lherz lherz lherz lherz

wt %

SiO2 40·74 43·34 42·16 43·84 44·81 41·74 43·92 42·43 42·38 42·16

TiO2 0·10 0·05 0·06 0·08 0·03 0·09 0·04 0·14 0·08 0·07

Al2O3 0·91 1·54 0·96 1·36 1·86 1·16 1·57 1·56 0·94 1·35

Fe2O3 1·98 2·94 1·74 1·87 2·12 1·78 1·99 2·03 2·43 1·91

FeO 6·41 5·80 5·78 5·66 4·99 5·99 5·62 5·69 5·46 5·96

MnO 0·12 0·11 0·12 0·12 0·11 0·12 0·12 0·12 0·12 0·12

MgO 44·96 41·85 45·86 42·92 40·14 45·04 39·91 42·47 43·79 43·97

CaO 1·48 1·98 1·12 1·29 2·74 1·29 2·92 2·46 1·06 1·33

Na2O 0·14 0·15 0·13 0·09 0·10 0·12 0·05 0·22 0·15 0·09

K2O 0·07 0·07 0·09 0·06 0·01 0·02 0·01 0·05 0·09 0·02

P2O5 0·19 0·17 0·16 0·29 0·17 0·29 0·15 0·16 0·17 0·17

H2O– 0·58 0·30 0·28 0·42 0·34 0·31 0·37 0·32 0·62 0·45

H2Oþ 0·98 0·86 0·69 1·06 1·54 0·86 1·82 1·05 1·45 1·04

CO2 0·68 0·22 0·32 0·30 0·35 0·40 0·81 0·68 0·41 0·47

Total 99·34 99·38 99·47 99·36 99·31 99·21 99·30 99·38 99·15 99·11

ppm

Cr 2307 2363 1719 2134 2876 3462 2108 1456 1821 3971

Ni 1895 1771 1834 1768 1673 1787 1746 1788 1751 1892

Rb 2·4 1·5 2·1 1·5 2·3 3·5 1·7 2·5 3·0 1·6

Sr 30 11 12 20 28 66 111 101 57 22

Y 0·29 0·24 0·14 0·37 0·35 0·62 0·28 1·3 0·88 0·42

Zr 5·7 2·9 3·7 6·0 2·5 8·7 5·1 19 11 9·6

Nb 2·1 0·20 0·61 0·84 2·0 3·7 0·95 5·7 4·9 2·1

Cs 0·02 0·024 0·019 0·024 0·020 0·028 0·019 0·020 0·026 0·048

La 1·11 0·253 0·487 0·985 0·529 1·842 0·489 2·972 2·548 0·671

Ce 2·31 1·19 1·04 2·33 1·53 3·51 1·38 6·51 5·89 1·53

Pr 0·269 0·114 0·121 0·290 0·171 0·360 0·175 0·777 0·657 0·195

Nd 1·12 0·498 0·492 1·28 0·666 1·38 0·698 3·16 2·51 0·91

Sm 0·219 0·112 0·096 0·269 0·119 0·239 0·100 0·570 0·404 0·196

Eu 0·074 0·043 0·036 0·095 0·035 0·080 0·028 0·182 0·150 0·063

Gd 0·239 0·132 0·108 0·278 0·117 0·255 0·107 0·581 0·426 0·189

Tb 0·039 0·027 0·022 0·046 0·014 0·032 0·014 0·074 0·050 0·026

Dy 0·152 0·113 0·072 0·183 0·068 0·148 0·062 0·334 0·210 0·117

Ho 0·032 0·027 0·018 0·038 0·014 0·026 0·013 0·059 0·037 0·020

Er 0·08 0·067 0·042 0·098 0·046 0·078 0·043 0·172 0·112 0·057

Tm 0·015 0·014 0·011 0·018 0·007 0·010 0·006 0·020 0·013 0·007

Yb 0·062 0·06 0·04 0·088 0·047 0·065 0·043 0·132 0·085 0·045

Lu 0·018 0·018 0·015 0·023 0·007 0·010 0·008 0·020 0·013 0·007

Hf 0·15 0·08 0·09 0·16 0·04 0·19 0·11 0·41 0·23 0·23

Ta 0·18 0·01 0·04 0·06 0·14 0·23 0·06 0·38 0·24 0·14

Pb 0·63 0·75 0·47 1·1 2·2 0·52 2·0 0·51 0·49 0·35

Th 0·064 0·032 0·045 0·146 0·047 0·153 0·062 0·127 0·141 0·050

U 0·080 0·034 0·051 0·172 0·073 0·088 0·066 0·305 0·167 0·118

Mg# 90·7 89·8 91·8 91·2 91·2 91·4 90·6 91·0 91·1 91·1

lherz, lherzolite; harz, harzburgite; dun, dunite; wehr, wehrlite; Mg#¼ 100[Mg/(Mgþ Fetot)]; b.d.,below detection limit.


11

Fig. 5. Whole-rock major element variations of MgO (wt %) vs SiO2,TiO2, Al2O3, CaO, Na2O and P2O5 (wt %) in NE Bavarian xenoliths.The primitive mantle composition (McDonough & Sun, 1995) is shown by an asterisk. Continuous-line black and grey arrows represent thebatch melting trends of Niu (1997) and Herzberg (2004), respectively. The dashed line represents a fractional melting trend from Niu (1997).


12

Fig. 6. Primitive-mantle normalized REE and trace element patterns for bulk xenolith samples. Normalizing values from McDonough & Sun(1995).


13

bearing lherzolite ZIN11 (Fig. 6). Some of the samples withlow total REE contents tend to have U-shaped REE pat-terns, but none of the samples exhibit apparent Eu anoma-lies. In addition, distinct enrichments in the large ionlithophile elements (LILEçRb, Cs), Sr, Pb and U are re-corded in the peridotite samples (Fig. 6). Uranium and Thare strongly fractionated from each other (UN/ThN¼1·7^9·6, mean 5·2) with the lowest value found in carbonate-bearing xenolith ZIN11.With the exception of two samples(ZINx2, ZINx5), the xenoliths show significant Nb^Ta en-richment and Zr^Hf depletion relative to PUM.Zirconium/Hf ratios are moderately fractionated (ZrN/HfN¼ 0·97^1·7, mean 1·2) whereas NbN/TaN ratios varygreatly between 0·33 and 2·3 (Fig. 7).

Mineral chemistryThe major mineral phases in the NE Bavarian xenolithsuite comprise olivine, orthopyroxene, Cr-diopside andspinel. These mineral phases are homogeneous at theintra-grain (core to rim) and inter-grain scale; their repre-sentative compositions are given in Table 3. The mineralchemistry of the symplectite-bearing xenoliths has been re-ported by S› pac› ek et al. (2013); only data for sample ZIN14are given in this study.Olivine (ol 1 and ol 2) exhibits similar, Mg-rich compos-

itions with Mg# (100[Mg/(MgþFetot)]) values rangingfrom 90·2 to 91·7, with the lowest Mg# found in carbon-ate-bearing xenoliths ZIN11 and ZIN14.Orthopyroxene (opx 1) is magnesian with Mg#

between 90·7 and 91·9, and Al2O3 and Cr2O3 contentsshowing a large variation between 2·0^4·8wt % and0·33^0·78wt %, respectively. Most orthopyroxene grainshave lowTiO2 contents50·10wt %. However, several sam-ples (ZIN11, ZIN19, ZIN27, ZINx8 and HIR16) have vari-able, and higher, TiO2 concentrations between 0·13 and0·23wt %.Clinopyroxene occurs in two textural varietiesçpri-

mary clinopyroxene (cpx 1), which occurs in the peridotitematrix, and secondary clinopyroxene, which occurswithin the carbonate-bearing melt pockets (cpx 2). TheMg# of cpx 1 (Cr-diopside) varies from 89·6 to 92·5,with Al2O3 contents varying from 2·7 to 6·2wt %, Cr2O3

contents from 0·4 to 2·8wt % and Na2O contents from0·5 to 1·8wt %. In contrast, cpx 2 is augite with a highAl2O3 content of 6·1^11wt % and highly variable CaOand Na2O contents of 12·6^22·7wt % and 0·74^3·2wt %,respectively (Table 4). Additionally, it is strongly enrichedinTiO2 (up to 7·0wt %; Table 3). The variations betweenMg# and Al, Ti (a.p.f.u.) for cpx 1 and cpx 2 are shownin Fig. 8.Spinel compositions exhibit significant variations in

Mg# from 68·3 to 79·5 and Cr# (100[Cr/(CrþAl)])from 19·3 to 52·1, plotting within the olivine^spinel mantlearray (OSMA; Arai, 1994; Fig. 9).

Representative analyses of the principal mineral phaseswithin carbonate-bearing pockets from samples ZIN11,ZIN14 and TEI2B are listed in Table 4. Carbonatesfrom samples ZIN11 and ZIN14 have variable MgOcontents ranging from 1·7 to 18·9wt %, corresponding to4·1^43·9mol % of the magnesite component (100[Mg/(MgþFeþCa)]), whereas that from the melt pocketwithin sample TEI2B has a generally lower magnesitecomponent of 0·5^17·4mol %.Interstitial quenched melt in the melt pockets shows a

broad range of compositions between samples, but alsowithin a single sample. In ZIN11 and ZIN14, it has anintermediate composition with SiO2 and CaO contents of53·0^58·2wt % and 8·5^10·5wt %, respectively, and lowTiO2 of50·23wt %. However, that from ZIN14 is signifi-cantly enriched in MgO (7·2wt %). The quenched melt

Fig. 7. ZrN/HfN vs NbN/TaN andThN vs UN/ThN for the NE Bavariaxenoliths. The large high field strength element (Zr, Hf, Nb,Ta) frac-tionation and overall U enrichment should be noted.


14

in theTEI2B melt pocket is richer inTiO2 (0·95wt %) andNa2O (15·7wt %), but significantly poorer in CaO(0·34wt %). The homogeneous quench (glass) from thesame pocket is even richer inTiO2 (1·49wt %) and yields

low totals (�95wt %), which may indicate modest concen-trations of volatile components such as H2O and/or CO2.Both types of quench inTEI2B melt pocket have elevatedP2O5 contents of 0·20^0·28wt %.

Table 3: Representative major element composition (wt %) of olivine, orthopyroxene, clinopyroxene and

spinel from NE Bavaria mantle xenoliths

Olivine


SiO2 41·26 41·20 41·11 40·95 40·93 40·85 41·24 40·59 41·23 41·18

FeO 8·53 8·76 8·43 9·05 9·00 9·31 8·39 9·52 9·26 8·27

MnO 0·14 0·13 0·10 0·13 0·13 0·15 0·14 0·17 0·14 0·12

MgO 49·48 49·09 49·48 48·96 49·02 48·94 49·60 49·24 49·42 49·75

CaO 0·01 0·07 0·08 0·08 0·07 0·07 0·08 0·12 0·09 0·08

NiO 0·39 0·35 0·39 0·39 0·39 0·39 0·40 0·38 0·38 0·40

Total 99·80 99·60 99·59 99·56 99·54 99·70 99·86 100·02 100·52 99·80

Mg# 91·2 90·9 91·3 90·6 90·7 90·4 91·3 90·2 90·7 91·5

Olivine


SiO2 41·28 41·32 41·35 41·48 41·02 40·97 41·15 41·03 41·30 41·31

FeO 8·72 8·69 8·07 9·44 8·44 8·54 8·89 8·35 8·61 8·31

MnO 0·11 0·14 0·11 0·11 0·11 0·13 0·12 0·12 0·12 0·11

MgO 49·49 49·28 49·85 47·98 50·07 50·06 49·57 50·13 49·86 49·98

CaO 0·07 0·08 0·09 0·10 0·07 0·01 0·08 0·07 0·08 0·06

NiO 0·39 0·39 0·37 0·35 0·41 0·41 0·42 0·41 0·38 0·41

Total 100·07 99·91 99·94 99·46 100·13 100·12 100·24 100·11 100·36 100·27

Mg# 91·0 91·0 91·7 90·1 91·4 91·3 90·9 91·5 91·2 91·5

Orthopyroxene


SiO2 56·87 55·74 55·75 55·06 55·62 55·76 55·54 55·52 55·86 56·26

TiO2 0·01 0·01 0·12 0·04 0·02 0·05 0·03 0·16 0·10 0·23

Al2O3 2·01 3·45 3·08 4·24 3·37 2·97 4·03 4·82 4·77 2·81

Cr2O3 0·33 0·56 0·78 0·60 0·61 0·52 0·60 0·60 0·61 0·77

FeO 5·85 5·62 5·27 5·77 5·81 5·91 5·38 5·81 5·94 5·25

MnO 0·13 0·11 0·10 0·11 0·16 0·13 0·10 0·17 0·14 0·06

MgO 34·31 32·98 33·17 32·68 33·09 33·13 33·03 31·92 32·45 33·47

CaO 0·27 0·77 0·96 0·89 0·84 0·82 0·88 0·97 0·93 1·02

Na2O 0·01 0·08 0·10 0·08 0·05 0·08 0·20 0·14 0·17 0·12

Total 99·80 99·33 99·35 99·47 99·55 99·38 99·78 100·12 100·95 99·99

Mg# 91·3 91·3 91·8 91·0 91·0 90·9 91·6 90·7 90·7 91·9

(continued)


15

Table 3: Continued

Orthopyroxene


SiO2 56·05 55·44 55·98 56·42 55·64 56·50 55·48 55·78 55·19 56·49

TiO2 0·13 0·09 0·10 0·20 0·02 0·05 0·03 0·01 0·16 0·05

Al2O3 2·78 4·05 3·21 3·09 3·53 2·08 3·61 3·31 4·23 2·61

Cr2O3 0·75 0·66 0·77 0·77 0·61 0·51 0·69 0·64 0·74 0·61

FeO 5·43 5·63 5·23 5·64 5·33 5·79 5·81 5·31 5·53 5·32

MnO 0·11 0·11 0·10 0·06 0·12 0·14 0·12 0·11 0·11 0·12

MgO 33·52 32·95 33·26 32·44 33·62 34·27 33·27 33·88 32·83 33·99

CaO 0·95 0·87 1·05 0·99 0·87 0·65 0·96 0·83 1·00 0·82

Na2O 0·10 0·10 0·15 0·10 0·05 0·02 0·05 0·07 0·16 0·10

Total 99·82 99·90 99·86 99·71 99·79 100·01 100·02 99·94 99·95 100·11

Mg# 91·7 91·3 91·9 91·1 91·8 91·3 91·1 91·9 91·4 91·9

Clinopyroxene


SiO2 52·96 53·02 – 52·18 52·39 52·33 52·92 52·66 53·41 52·80

TiO2 b.d. 0·03 – 0·16 0·06 0·17 0·09 0·45 0·30 0·54

Al2O3 3·27 4·04 – 5·40 3·56 4·29 4·94 6·18 5·65 3·90

Cr2O3 0·37 0·90 – 1·08 0·92 1·31 1·04 1·12 1·08 1·51

FeO 2·96 2·79 – 2·94 2·83 3·05 2·86 3·20 3·01 2·82

MnO 0·06 0·07 – 0·06 0·08 0·07 0·09 0·09 0·08 0·04

MgO 18·09 16·39 – 16·12 16·90 16·27 16·57 15·52 16·03 16·86

CaO 21·51 21·31 – 20·37 21·98 21·00 19·75 19·30 20·32 19·66

Na2O 0·54 1·23 – 1·43 0·73 1·34 1·37 1·78 1·31 1·39

Total 99·74 99·78 – 99·73 99·46 99·83 99·74 99·74 101·20 99·52

Mg# 91·6 91·3 – 90·7 91·4 90·5 91·2 89·6 89·6 91·4

Clinopyroxene


SiO2 52·97 52·70 53·10 53·24 53·08 53·00 52·74 53·10 52·39 52·76

TiO2 0·33 0·30 0·25 0·52 0·05 0·12 0·06 0·02 0·47 0·25

Al2O3 3·96 5·18 4·39 4·26 3·69 2·73 3·70 3·88 5·62 4·98

Cr2O3 1·53 1·14 2·78 1·23 0·86 1·18 2·88 1·05 1·28 2·00

FeO 2·71 2·96 1·59 3·00 2·61 2·57 0·94 2·63 3·09 2·79

MnO 0·02 0·08 0·07 0·02 0·07 0·02 17·33 0·06 0·07 0·05

MgO 16·80 16·20 16·95 16·46 17·28 17·76 0·05 16·99 16·27 15·92

CaO 19·83 19·45 19·05 19·69 21·05 20·89 21·13 20·80 18·81 18·57

Na2O 1·34 1·40 1·44 1·49 0·82 0·66 0·62 1·05 1·60 2·08

Total 99·48 99·39 99·61 99·91 99·50 98·92 99·45 99·58 99·61 99·38

Mg# 91·7 90·7 91·6 90·7 92·2 92·5 91·5 92·0 90·4 91·1

(continued)


16

Feldspar has a highly variable composition. In sampleZIN11, alkali feldspar (Ab67An5Or28) is predominant andis accompanied by rare plagioclase (Ab61An35Or4), occur-ring mostly in silicate pockets. Feldspar in ZIN14 meltpockets is similar in composition (Ab54An44Or2) to plagio-clase from ZIN11. In contrast, feldspar in the silicatequench within melt pockets in sample TEI2B (fspþquench; Fig. 4d) is almost pure albite in composition(Ab95An3Or2) and has a higher TiO2 content of 2·1wt %.Needle-shaped opx 2 grains (Fig. 4e) hosted by carbonatein ZIN11 have significantly lower Mg# of 83·3 comparedwith opx 1with Mg# of 90·7.

Apatite contains �0·55wt % Cl and 3·70^3·84 wt % F.Crichtonite has the composition of loveringite with 2·7^4·1wt % CaO, 11·5^12·3wt % Cr2O3 and 3·7^5·5wt %ZrO2 (Table 4).

Trace element geochemistry ofclinopyroxene, carbonate and meltPrimary clinopyroxene (cpx 1) in four spinel lherzolites(10ZIN2, 10ZIN5, ZINx2, HIR6) and secondary clinopyr-oxene (cpx 2), carbonate and quenched melt from threecarbonate-bearing lherzolite samples (ZIN11, ZIN14,TEI2B) were analysed for their trace element

Table 3: Continued

Spinel


TiO2 0·01 0·04 0·53 0·15 0·10 0·36 0·08 0·35 0·17 1·32

Al2O3 35·97 37·26 29·88 45·31 35·79 34·80 42·73 44·42 49·37 24·67

Cr2O3 29·55 29·24 37·07 21·88 29·75 32·49 24·66 21·92 17·58 39·95

V2O3 0·13 0·10 0·13 0·13 0·20 0·17 0·09 0·09 0·10 0·22

FeO 17·24 14·63 14·68 13·01 16·36 14·87 12·85 13·36 12·55 16·71

MnO b.d. b.d. b.d. b.d. b.d. b.d. b.d. 0·14 0·14 b.d.

MgO 16·21 17·57 16·77 18·76 17·09 16·93 18·91 19·22 20·28 16·52

CaO b.d. 0·03 0·01 b.d. 0·01 0·01 b.d. 0·01 b.d. b.d.

ZnO 0·09 0·10 0·05 0·06 0·10 0·09 0·09 0·05 0·10 0·08

NiO 0·21 0·25 0·25 0·31 0·29 0·29 0·31 0·32 0·35 0·25

Total 99·42 99·30 99·37 99·60 99·68 100·00 99·71 99·71 100·62 99·74

Mg# 69·7 74·8 73·6 76·8 73·2 72·7 78·1 72·0 74·2 74·0

Cr# 35·5 34·7 45·4 24·5 35·8 38·5 27·9 24·5 19·3 52·1

Spinel


TiO2 0·72 0·28 0·44 0·95 0·07 0·12 0·09 0·01 0·44 0·56

Al2O3 27·17 42·71 31·01 28·47 38·47 28·27 35·99 36·53 40·83 32·40

Cr2O3 39·53 23·79 35·91 36·27 28·62 37·37 29·88 30·67 25·18 34·27

V2O3 0·16 0·11 0·15 0·15 0·09 0·19 0·15 0·10 0·11 0·16

FeO 15·65 13·12 15·31 17·83 13·73 17·93 15·34 14·54 13·39 14·71

MnO b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d.

MgO 16·32 18·94 17·07 15·87 18·39 15·31 17·77 17·57 19·12 17·18

CaO b.d. b.d. 0·01 b.d. b.d. b.d. b.d. 0·01 b.d. 0·01

ZnO 0·09 0·07 0·04 0·08 0·08 0·23 0·08 0·10 0·09 0·07

NiO 0·24 0·32 0·25 0·24 0·29 0·16 0·29 0·29 0·28 0·26

Total 99·87 99·34 100·18 99·86 99·74 99·57 99·58 99·91 99·45 99·60

Mg# 72·4 78·4 74·0 70·2 77·3 68·3 75·7 74·8 79·5 74·5

Cr# 49·4 27·2 43·7 46·1 33·3 47·0 35·8 36·0 29·3 41·5

b.d., below detection limit; Mg#¼ 100[Mg/(Mgþ Fe)]; Cr#¼ 100Cr/(CrþAl)].


17

Table4:

Representativemineralanalyses(wt%)ofcarbonate-bearingpocketswithinsamplesZIN

11,ZIN

14andTEI2B

Sam

ple:

ZIN11

ZIN14

TEI2B

Mineral:

Cpx2

Opx2

Ol2

Afs

Pl

Quen

chCb

Cb

IlmCrich

Ap

Cpx2

Ol2

Pl

Quen

chCb

Cb

Cb

Cpx2

Pl

Quen

chQuen

chCb

Cb

Cb

SiO

242·80

56·52

41·28

66·95

58·89

58·23

n.a.

n.a.

0·06

0·07

0·21

49·89

40·55

57·84

52·98

0·06

0·03

0·03

47·72

57·89

57·35

57·09

n.a.

n.a.

n.a.

TiO

26·97

0·39

n.a.

0·23

n.a.

0·22

n.a.

n.a.

70·27

66·93

n.a.

0·72

n.a.

n.a.

0·23

n.a.

n.a.

n.a.

3·52

2·07

0·95

1·49

n.a.

n.a.

n.a.

Al 2O3

10·96

0·06

n.a.

19·68

25·99

25·59

n.a.

n.a.

1·37

0·73

b.d.

10·21

n.a.

26·91

22·62

0·02

0·00

0·02

6·12

23·53

26·00

22·97

n.a.

n.a.

n.a.

Cr 2O3

1·29

0·05

n.a.

n.a.

n.a.

0·05

n.a.

n.a.

2·24

11·94

n.a.

0·38

n.a.

n.a.

0·19

n.a.

n.a.

n.a.

1·02

0·69

0·03

b.d.

n.a.

n.a.

n.a.

FeO

tot

3·15

10·78

9·72

0·06

0·22

0·32

b.d.

0·04

9·70

6·54

0·16

4·15

11·22

0·14

1·90

0·25

0·10

0·07

3·27

0·01

0·47

0·46

6·72

0·21

0·39

MnO

0·08

0·27

0·20

b.d.

n.a.

0·03

0·02

b.d.

0·13

0·10

0·07

0·26

0·40

n.a.

0·11

0·02

0·06

b.d.

0·04

0·14

0·04

0·02

0·47

0·03

0·08

MgO

15·81

30·14

50·19

b.d.

n.a.

0·10

1·65

1 ·81

12·94

4·19

0·39

16·34

47·55

n.a.

7·18

14·18

18·91

4·31

14·11

0·01

0·10

0·11

6·99

0·20

0·21

CaO

12·61

1·77

0·25

0·96

7·56

8·46

53·20

52·87

0·52

3·40

54·30

17·54

0·20

9·31

10·49

38·06

33·53

50·26

22·67

0·89

0·34

0·80

40·98

51·32

50·86

Na 2O

3·20

0·05

n.a.

7·87

7·29

6·75

n.a.

n.a.

n.a.

n.a.

0·09

0·82

n.a.

6·24

3·72

n.a.

n.a.

n.a.

0·74

13·97

15·72

11·67

n.a.

n.a.

n.a.

K2O

1·07

b.d.

n.a.

4·97

0·75

0·64

n.a.

n.a.

n.a.

n.a.

n.a.

b.d.

n.a.

0·42

0·23

n.a.

n.a.

n.a.

b.d.

0·40

0·74

0·30

n.a.

n.a.

n.a.

BaO

0·10

n.a.

n.a.

0·05

0·02

b.d.

n.a.

n.a.

n.a.

n.a.

n.a.

b.d.

n.a.

0·04

0·01

n.a.

0·03

0·02

n.a.

n.a.

b.d.

0·06

n.a.

n.a.

n.a.

SrO

0·04

n.a.

n.a.

b.d.

0·09

b.d.

n.a.

n.a.

n.a.

n.a.

0·04

0·07

n.a.

0·12

0·02

0·05

0·12

0·04

n.a.

n.a.

b.d.

0·16

n.a.

n.a.

n.a.

ZnO

0·08

n.a.

n.a.

n.a.

n.a.

b.d.

n.a.

n.a.

0·05

b.d.

n.a.

0·09

n.a.

n.a.

0·02

0·03

0·01

0·05

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

V2O3

0·16

n.a.

n.a.

n.a.

n.a.

b.d.

n.a.

n.a.

0·98

2·68

n.a.

b.d.

n.a.

n.a.

b.d.

n.a.

n.a.

n.a.

0·20

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

P2O5

n.a.

n.a.

n.a.

n.a.

n.a.

0·03

0·08

0·09

n.a.

n.a.

41·04

n.a.

n.a.

0·08

n.a.

0·07

0·02

0·09

n.a.

n.a.

0·20

0·28

n.a.

n.a.

n.a.

Cl

n.a.

n.a.

n.a.

n.a.

n.a.

b.d.

n.a.

n.a.

n.a.

n.a.

0·55

n.a.

n.a.

n.a.

b.d.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Fn.a.

n.a.

n.a.

n.a.

n.a.

b.d.

n.a.

n.a.

n.a.

n.a.

3·84

n.a.

n.a.

n.a.

b.d.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Nb2O5

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0·24

0·22

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Sc 2O3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0·11

0·04

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

ZrO

2n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

1·25

4·40

0·72

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

WO3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0·13

b.d.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Y2O3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0·06

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

La 2O3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0·06

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Ce 2O3

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

0·25

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

n.a.

Total

98·32

100·02

101·64

100·77

100·81

100·42

54·95

54·77

99·97

101·24

101·79

100·47

99·92

101·10

99·68

52·73

52·81

54·90

99·40

99·58

101·74

94·91

55·15

51·76

51·53

Mg#

89·9

83·3

90·2

n.d.

n.d.

n.d.

100·0

98·7

n.a.

n.d.

n.a.

87·5

90·2

n.d.

n.d.

99·0

99·7

99·2

88·4

n.d.

n.d.

n.d.

65·0

62·6

49·2

Mag

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

4·1

4·5

n.a.

n.d.

n.a.

n.d.

n.d.

n.d.

n.d.

34·1

44·0

10·7

n.d.

n.d.

n.d.

n.d.

17·4

0·5

0·6

Cpx2,

clinopyroxeneII;Ol2,

olivine2;

Afs,alkalifeldspar;Pl,plagioclase;

Cb,carbonate;

Ilm,ilm

enite;

Crich

,crichtonite;

Ap,ap

atite;

n.a.,notan

alyzed

;n.d.,not

determined

;b.d.,

below

detectionlim

it;Quen

ch,quen

ched

melt;

Mg#¼100[Mg/(MgþFe)];

Mag¼100[Mg/(MgþFeþCa)].


18

concentrations by LA-ICP-MS (Table 5). With the excep-tion of ZIN14, the primitive mantle-normalized REE andincompatible trace element patterns of cpx 1 in all samplesare similar (Fig. 10). Despite the fact that some samples ex-hibit convex-upward REE patterns with LaN/SmN andSmN/YbN ratios of 0·5^0·7 and 1·7^6·8, respectively, theREE distribution in clinopyroxenes generally is similar tothat in their corresponding whole-rocks. On the otherhand, the clinopyroxenes are significantly depleted in Rb,Pb and U when compared with the whole-rocks, suggest-ing that these elements reside in some as yet unidentifiedphase and/or at grain boundaries enriched in these elem-ents (e.g. Zindler & Jagoutz, 1988; Eggins et al., 1998;Hiraga et al., 2004; Harvey et al., 2012). Clinopyroxene 1 inZIN14 exhibits a peculiar sinusoidal REE pattern withhigher HREE contents than in the other analysed clino-pyroxenes (Fig. 10). Clinopyroxene 2, present specificallyin melt-bearing domains, was successfully analysed onlyin lherzolite TEI2B (Table 5), where it forms small

idiomorphic grains (5100 mm) within the carbonate-bear-ing melt pocket (Fig. 4d). All analysed grains in thispocket (average of three grains inTable 5) are strongly en-riched in incompatible trace elements, in particularLREE, Sr, Nb and Ba, with the highest total trace elementconcentrations among all the analysed minerals, but sig-nificant depletion in Pb, Zr, and Hf (Fig. 10).The REE abundances in the carbonates in lherzolites

ZIN11, ZIN14 and TEI2B are very low and mostly belowthe detection limit, with the exception of La, Ce, Pr andNd in ZIN14 and TEI2B. Strontium and Ba contents incarbonates from ZIN11 and ZIN14 are higher than in thecoexisting cpx 2 and vary in the range 143^187 ppm and7·5^9·0 ppm, respectively. In comparison, carbonate fromsample TEI2B (Fig. 4d) is strongly enriched in Sr(1065 ppm) and Ba (769 ppm). These contents are similarto those reported from carbonates found in mantle xeno-liths from Spitsbergen and Mongolia (Ionov, 1998) butsignificantly lower than those of carbonates found inKerguelen mantle xenoliths (Moine et al., 2004). Quenchedmelt in the carbonate-bearing pocket in TEI2B exhibitsan LREE-enriched REE pattern (Fig. 10) with LaN/YbNof �41and is strongly enriched in Rb (54 ppm) and HFSE.

87Sr/86Sr and 143Nd/144Nd variations inclinopyroxeneThe measured Nd^Sr isotope compositions of four(10ZIN2, 10ZIN5, ZINx2, HIR6) clinopyroxene separatesfrom Zinst and Hirschentanz xenoliths are listed inTable 6 and plotted in Fig. 11. The 143Nd/144Nd ratios dis-play a limited range between 0·512813 and 0·512928, whichcorresponds to present-day eNd values ofþ 3·9 toþ 5·8. In

Fig. 8. Compositional variations in primary (cpx 1) and secondary(cpx 2) clinopyroxene from the NE Bavarian xenolith suite. (a)Variation of Mg# vs Ti content (a.p.f.u.). (b) Variation of Mg# vsAl content (a.p.f.u.).

Fig. 9. Variation of Mg# in olivine and Cr# in spinel for the NEBavaria xenoliths. OSMA (olivine^spinel mantle array) from Arai(1994).


19

three samples, the Nd composition is paralleled by87Sr/86Sr ratios from 0·70321 to 0·7035, not much differentfrom the Nd^Sr isotopic composition of the host basalts(Fig. 11). In contrast, lherzolite 10ZIN5 has a much moreradiogenic 87Sr/86Sr composition of 0·70414, at an eNd simi-lar to those of the other cpx samples and host basalts (Fig.11). The Sr^Nd isotope compositions overlap the range re-ported for spinel peridotite xenoliths sampled by theCenozoic volcanism of the ECRIS (see Downes, 2001, andreferences therein).With the exception of 10ZIN5, the Sr^Nd isotopic compositions of samples from this studybroadly resemble that of the assumed plume material(Wilson & Downes, 1991) and ambient upwelling mantle(Hoernle et al., 1995) involved in the genesis of the CEVP.

However, the NE Bavarian xenoliths studied here do notshow the vertical array of 87Sr/86Sr and 143Nd/144Nd ratiosreported for other Cenozoic mantle peridotite and pyrox-enite xenoliths from the Bohemian Massif (Ackermanet al., 2007, 2012).

Lithium systematicsWhole-rock Li contents as well as Li isotopic compositionsin the NE Bavaria peridotite xenolith suite are listed inTable 7 and plotted in Fig. 12.The samples show no to mod-est Li enrichment (1·4^5·8 ppm) compared with pristinemodally non-metasomatized mantle xenoliths (in generalbetween �1·2 and �2·0 ppm Li; Seitz & Woodland, 2000;Magna et al., 2006; Jeffcoate et al., 2007; Magna et al.,

Table 5: Trace element compositions of clinopyroxenes, carbonates and melt from NE Bavaria

mantle xenoliths

Sample: 10ZIN2 10ZIN5 ZINx2 HIR6 ZIN11 ZIN11 ZIN14 ZIN14 TEI2B TEI2B TEI2B TEI2B

Mineral: Cpx 1 Cpx 1 Cpx 1 Cpx 1 Cpx 1 Cb Cpx 1 Cb Cpx 1 Cpx 2 Cb Melt

ppm

Li 20 33 11 1·2 16 b.d. 18 b.d. 32 1·4 b.d. b.d.

Rb 50·006 0·02 50·005 50·005 0·46 0·07 0·3 b.d. 0·09 0·86 0·10 54

Sr 242 129 91 339 122 187 62 143 163 411 1065 167

Y 6·3 3·9 7·1 5·0 10 b.d. 14 1·3 11 33 50·02 1·9

Zr 26 5·5 23 16 47 1·5 13 4·2 90 218 0·21 33

Nb 2·1 1·1 1·4 0·82 2·1 0·37 1·1 0·92 2·7 19 b.d. 42

Ba 0·078 0·043 0·10 0·15 5·4 7·5 2·5 9 0·25 35 769 119

La 2·6 1·7 2·9 9·3 5·3 b.d. 3·8 0·62 5·3 32 0·14 8·6

Ce 14 8·0 11 26 13 b.d. 7·1 0·74 22 73 0·15 14

Pr 3·1 1·8 1·7 3·8 1·8 b.d. 0·86 0·17 4·2 13 0·024 1·4

Nd 16 8·6 7·5 16 7·6 b.d. 3·4 0·60 22 65 b.d. 4·8

Sm 3·5 1·6 1·7 2·5 1·9 b.d. 1·2 b.d. 5·5 14 b.d. 0·68

Eu 1·1 0·45 0·58 0·70 0·70 b.d. 0·51 b.d. 1·8 4·0 0·46 0·24

Gd 2·6 1·1 1·7 1·8 2·0 b.d. 1·9 b.d. 4·0 12 b.d. 0·79

Tb 0·31 0·13 0·26 0·22 0·32 b.d. 0·40 b.d. 0·55 1·5 b.d. 0·070

Dy 1·5 0·73 1·5 1·1 1·9 b.d. 2·6 b.d. 2·5 7·9 b.d. 0·36

Ho 0·25 0·15 0·29 0·19 0·40 b.d. 0·61 b.d. 0·43 1·3 b.d. 0·070

Er 0·64 0·44 0·74 0·51 1·0 b.d. 1·6 b.d. 0·9 3·2 b.d. 0·18

Tm 0·080 0·064 0·095 0·069 0·16 b.d. 0·25 b.d. 0·13 0·37 b.d. 0·029

Yb 0·56 0·45 0·60 0·50 0·99 b.d. 1·4 b.d. 0·7 2·2 b.d. 0·14

Lu 0·082 0·067 0·079 0·079 0·15 b.d. 0·21 b.d. 0·12 0·29 b.d. 0·027

Hf 0·35 0·18 0·82 0·54 1·3 b.d. 0·50 b.d. 2·4 5·7 b.d. 0·50

Ta 0·19 0·12 0·25 0·13 0·34 b.d. 0·14 b.d. 0·58 3·6 b.d. 3·0

Pb 0·11 0·12 0·06 0·12 0·44 0·123 0·30 1·0 0·17 0·14 0·14 0·25

Th 0·055 0·11 0·045 0·22 0·53 b.d. 1·0 b.d. 0·23 1·1 0·053 1·8

U 0·008 0·019 0·009 0·031 0·15 0·11 0·14 0·26 0·072 0·11 0·023 0·28

n.a., not analyzed; b.d., below detection limit; Cpx 1, primary clinopyroxene 1; Cpx 2, secondaryclinopyroxene 2; Cb, carbonate.


20

2008; Pogge von Strandmann et al., 2011; Fig. 12). This is inagreement with other studies of metasomatically over-printed mantle xenoliths (e.g. Rudnick & Ionov, 2007;Aulbach et al., 2008; Zhang et al., 2010; Tang et al., 2011; Suet al., 2012; Fig. 12). Peridotites from Hirschentanzshow less variability in Li abundance (1·4^2·9 ppm) andd7Li (^2·5 to 2·5ø) compared with those from Zinst(1·5^5·8 ppm Li; d7Li from �9·7 to 1·2ø). Lithium

abundances do not correlate with modal contents of oliv-ine, orthopyroxene or clinopyroxene, suggesting both thenegligible influence of mineralogy on Li distribution andthe absence of a principal carrier phase of Li in the suite.This conclusion is reinforced by the observation that, forexample, samples 10ZIN5 and ZIN19 differ by �2 ppm Lidespite their lherzolitic affinity, with near-identical modalcompositions, whereas similar Li contents are found inlherzolites HIR3 and HIR4 with very distinct modal min-eral assemblages. Similarly, Li abundances do not correlatewith either major or trace element contents in the wholesuite, suggesting decoupling of Li from the other traceelements during secondary processes. The presence of asecondary carbonate component in three lherzolitesZIN11, ZIN14 and TEI2B imparts insignificant and/ornon-systematic changes to Li contents, suggesting low Liabundance in carbonates.Lithium isotope compositions show a huge departure to-

wards low d7Li compared with pristine mantle xenoliths(Magna et al., 2006, 2008; Jeffcoate et al., 2007; Pogge vonStrandmann et al., 2011; Fig. 12). Interestingly, d7Li valuescorrelate positively with modal olivine in the Hirschentanzand Teichelberg samples but are negatively correlated forthe Zinst locality (Fig. 13a), whereas the opposite isobserved for d7Li vs modal clinopyroxene and ortho-pyroxene in the respective localities (not shown). Thevulnerability of d7Li to post-magmatic modification inclinopyroxene, olivine and, to a lesser extent, orthopyrox-ene has been recognized (e.g. Seitz et al., 2004; Rudnick &Ionov, 2007; Zhang et al., 2010; Su et al., 2012). d7Li valuesdo not vary in any systematic way with other indices ofmagmatic fractionation (e.g. Zr/Hf, La/Sm) and/or fluidactivity (e.g. Sr/Y, Rb/Nb) and may thus be regardedas an independent parameter of metasomatic processes.However, whole-rock d7Li values correlate negativelywith Li/Yb (Fig. 13b), which itself shows an extremerange between 18 and 143 in the whole suite and isfar higher than Li/Yb variability in metasomatized (540;e.g. Brooker et al., 2004; Ionov & Seitz, 2008; Pogge vonStrandmann et al., 2011) and pristine mantle xenoliths

Table 6: Rb^Sr and Sm^Nd concentrations and isotopic data for clinopyroxenes from NE Bavaria mantle xenoliths

Sample Rb (ppm) Sr (ppm) 87Rb/86Sr 87Sr/86Sr(m) Sm (ppm) Nd (ppm) 147Sm/144Nd 143Nd/144Nd(m) eNd

10ZIN2 0·02 129 0·0004 0·703208� 7 1·6 8·6 0·11 0·512858� 8 þ4·4

10ZIN5 50·005 339 n.d. 0·704139� 7 2·5 16 0·095 0·512831� 6 þ3·9

ZINx2 50·006 242 n.d. 0·703234� 7 3·5 16 0·13 0·512928� 8 þ5·8

HIR6 50·005 91 n.d. 0·703470� 7 1·7 7·5 0·14 0·512813� 7 þ3·6

Rb, Sr, Sm and Nd concentrations were determined by ICP-MS; m, measured ratio; error given as 2sm; eNd correspondsto the measured ratio using for CHUR 143Nd/144Nd¼ 0·512630 and 147Sm/144Nd¼ 0·1960 (Bouvier et al., 2008); n.d., notdetermined.

Fig. 10. Primitive-mantle normalized REE and trace element pat-terns for primary clinopyroxene (cpx 1), secondary clinopyroxene(cpx 2) and melt. Normalizing values fromMcDonough & Sun (1995).


21

(3^6; e.g. Magna et al., 2008; Pogge von Strandmann et al.,2011) as well as melt derivatives of the upper mantle (Li/Yb generally54; Ryan & Langmuir, 1987).

HOST BASALTSHost basalts from Zinst, Hirschentanz and Teichelberg arebasanitic in composition following the classification of LeMaitre (2002), with SiO2¼39·5^44·0wt %, Na2OþK2O¼ 3·5^3·8wt % and Mg# between 77·9 and 78·4(Table 8). Potassium^Ar dating yields indistinguishableages of 21·2�1·1Ma (Zinst), 23·5�1·2 Ma (Hirschentanz)and 22·1�1·1Ma (Teichelberg) (Table 9). These ages, how-ever, are significantly younger than previously reportedK^Ar determinations of 28·8�1·8 Ma and 25·6�1·0 Mafor Zinst (Todt & Lippolt, 1975; Horn & Rohrmu« ller,2005).Trace element concentrations and Sr^Nd^Li isotopicdata for the host basalts are reported inTables 7, 8 and 10.All rocks are similarly enriched in LREE (LaN/YbN¼17·2^24·5), LILE,Th and U relative to the primitivemantle, coupled with depletions in Pb, Zr and Hf. The ini-tial Sr^Nd isotopic composition of the host basalts is uni-form, with initial 87Sr/86Sr ranging from 0·7033 to 0·7035and 143Nd/144Nd between 0·51280 and 0·51283,

corresponding to eNd from þ4·0 to þ4·6. These data aresimilar to those for other Cenozoic volcanic rocks of theBohemian Massif (Lustrino & Wilson, 2007; Ulrych et al.,2011). The Li isotopic composition (þ2·3 to þ4·2ø) iswithin the range of other intra-plate alkaline volcanicrocks from central Europe (Magna & Rapprich, 2012) aswell as from other localities (Ryan & Kyle, 2004; Halamaet al., 2007, 2008; Hamelin et al., 2009). However, the d7Liof the host basalts appears to be shifted towards highervalues relative to the average d7Li of the xenoliths, similarto what was reported for Cenozoic alkaline basalts in cen-tral Asia hosting frequent peridotite xenoliths (Magnaet al., 2008).

DISCUSS IONPartial melting in the mantle source ofthe xenolith samplesThere are several lines of evidence that the xenolith suite(except for ZIN11 and ZIN14) experienced prior melt ex-traction: (1) negative correlation between Mg# and Alcontent in primary clinopyroxene (Fig. 8a); (2) negativecorrelation between some major oxides (e.g. SiO2, Al2O3,CaO) and MgO whole-rock contents (Fig. 5); (3) high

Fig. 11. Measured 87Sr/86Sr vs 143Nd/144Nd and eNd values for clinopyroxene from NE Bavarian mantle xenoliths together with the compositionof the host basalts (dark grey field). Light grey field represents the composition of CEVP basalts (data sources: Alibert et al., 1983, 1987;Blusztajn & Hart, 1989; Bendl et al., 1993; Ulrych et al., 1998, 2000, 2002; Lustrino & Wilson, 2007); the medium-grey field indicates the isotopiccomposition of peridotite and pyroxenite xenoliths from the Cenozoic volcanic rocks of the Bohemian Massif (Ackerman et al., 2007, 2012).BSE, present-day Bulk Silicate Earth composition; DMM, Depleted MORB Mantle composition (Workman & Hart, 2005).


22

Mg# of olivine and pyroxenes; (4) lower HREE contentsin whole-rock samples compared with primitive mantle(Fig. 6). On the other hand, the absence of a correlation be-tween whole-rock TiO2, Na2O and MgO contents, clino-pyroxene modal abundance and whole-rock Cr#, andonly weak positive correlation between Mg# of olivineand Cr# of spinel (r¼ 0·69; Fig. 9) suggests some perturb-ation of major element systematics and possible clinopyrox-ene addition during later stages of metasomatism. Anegative correlation between SiO2, CaO, Al2O3 and MgOin peridotites (Fig. 5) is usually ascribed to variable degreesof partial melting, implying preferential melting of clino-pyroxene and spinel (e.g. Frey & Green, 1974; Mysen &Kushiro, 1977; Frey & Prinz, 1978). However, whereas thecompositional trends of CaO vs MgO fit well the batchmelting model of Niu (1997), compositional trends in ourxenolith suite exhibit lower contents of SiO2 and Al2O3 fora given MgO than would be expected from the model com-positions of Niu (1997) and Herzberg (2004).Partial melting degrees (F) can be estimated using the

major element and modal composition of the whole-rock

(Niu, 1997; Herzberg, 2004; Walter, 2004), Cr# in spinel(Hellebrand et al., 2001, 2005) or trace element (REE, Y)composition of clinopyroxene (Johnson et al., 1990;Norman, 1998). However, calculations based on the traceelement composition of clinopyroxene clearly yield toolow F, which is not consistent with the whole-rock majorelement and modal composition. This is probably due toREE, Y or cpx addition during metasomatism and/or ahigh proportion of Yb and Y hosted by orthopyroxene(e.g. McDonough et al., 1992; Eggins et al., 1998). A morerobust estimate of the amount of melt depletion should beobtained from the major element (MgO, SiO2, Al2O3)and modal composition of the xenoliths (except forsamples ZIN11 and ZIN14 with whole-rock major elementcompositions strongly affected by metasomatism) and theexperimental grids of Herzberg (2004) and Walter (2004)for spinel or garnet peridotite. Using this approach, theNE Bavaria xenoliths define trends consistent with awide range of partial melting degrees from F �15 to 30%(Figs 14 and 15) with the highest calculated F for thecpx-poor xenoliths. Similar results (F �6^26%) can beobtained using the calculation of Niu (1997) based onwhole-rock MgO contents (Table 11). Alternatively, partialmelting degrees for spinel peridotites can be estimatedfrom Cr# in spinel (Hellebrand et al., 2001). Using a mod-ified version of this calibration (Hellebrand et al., 2005),partial melting degrees of �8 to �18% can be inferred forall xenoliths.

Origin of melt pocketsThe origin of glass- or melt-bearing pockets and/or vein-lets enclosed in mantle xenoliths remains a matter ofdebate. The following processes have been identified ascrucial for the formation of melt pockets: breakdown ofamphibole or mica (e.g. Frey & Green, 1974; Neumann &Wulff-Pedersen et al., 1997; Yaxley et al., 1997; Yaxley &Kamenetsky, 1999), breakdown of orthopyroxene andspinel (Dautria et al., 1992), reaction of peridotite withmigrating melts and fluids in the upper mantle (e.g.Ionov et al., 1994; Zinngrebe & Foley, 1995; Neumann &Wulff-Pedersen, 1997; Schiano et al., 1998; Ishimaru &Arai, 2009), or late intrusion of the host magma into thexenoliths (e.g. Klu« gel, 1998, 2001; Miller et al., 2012).The formation of silicate and carbonate^silicate melt

pockets in the xenoliths from NE Bavaria was discussed inbrief by S› pac› ek et al. (2013), who studied the origin of un-usual fine-grained opx^spl^pl symplectites pseudomorph-ing garnet. Type II pockets are hosted preferentially inthese symplectites and in some cases there is clear struc-tural evidence that these are older than bothType I pock-ets and the veinlets in the proximity of the symplectites.Based on the textural features, mineralogy and bulk chem-istry of the melt pockets, S› pac› ek et al. (2013) suggested thatwhereas the veinlets andType I pockets are probably asso-ciated with melt intrusion from the host basanite, it is

Table 7: Lithium concentrations and isotopic compositions

of NE Bavaria mantle xenoliths and their host basalts

Sample Lithology Li (ppm) d7Li (ø) 2s

10ZIN1 lherzolite 2·70 –3·45 0·19

10ZIN2 lherzolite 2·48 –3·11 0·16

10ZIN3 harzburgite 3·03 –3·24 0·20

10ZIN4 lherzolite 2·47 0·07 0·36

10ZIN5 harzburgite 4·29 –4·37 0·53

10ZIN6 lherzolite 3·39 –2·02 0·26

ZIN9 lherzolite 3·43 –1·34 0·25


ZIN14 lherzolite 1·50 1·16 0·25


ZIN27 dunite–wehrlite 5·18 –8·01 0·18

ZINx2 lherzolite 2·67 –3·75 0·13



HIR3 lherzolite 1·69 –2·52 0·08

HIR4 lherzolite 1·80 2·28 0·17

HIR5 lherzolite 1·41 –0·73 0·25



TEI2B lherzolite 2·48 1·33 0·13

B-10 Zinst basanite 6·0 2·31 0·45

B-9 Hirschentanz basanite 6·1 3·18 0·30

B-11 Teichelberg basanite 5·8 4·22 0·13


23

difficult to explain theType II pockets by metasomatic re-action with the xenolith-entraining magma.The generally high Na content and a local presence of

carbonate in the Type II pockets requires a chemicallyopen system. On the other hand, in terms of the high con-tents of Si and Al, usually lowTi, and much higher Na2O/K2O (�10 to �26 compared with �3^4 in the host basan-ite) (Table 4), the quenched silicate melts differ signifi-cantly from the host basanite itself (Table 8) or from anyproducts expected to result from reaction between the pri-mary phases and significant volume of basanite. At thesame time, the absence of relict amphibole or mica andlow K contents in the quenched melt are factors againstany significant contribution of OH-bearing minerals to itsorigin. Therefore, similar to many previous studies ofmelt pockets in mantle xenoliths (e.g. Ionov et al., 1994;Zinngrebe & Foley, 1995; Neumann & Wulff-Pedersen,1997, 2001; Neumann et al., 2002; Rampone et al., 1997),we suggest that the Type II melt pockets most probablyrecord an older metasomatic reaction, which pre-datedthe infiltration of the host magma and took place in themantle. The highly variable composition of the quenchedmelt in all the pockets suggests that its formation is notcontrolled by fractional crystallization only (e.g. Ionov

et al., 1994). Structural evidence for the resorption andmetasomatic reaction of primary phases (clinopyroxene,spinel; Fig. 4c, d and f) suggests reaction of the primaryperidotite (devoid of hydrous phases) with percolatingmelts.The mineralogy and bulk composition of the pocketsindicate that these melts had a high Na content, low Kcontent and were CO2-bearing. Based on the structuralposition of theType II pockets (or domains of metasomaticmelting) within the external parts of very unstable sym-plectites, S› pac› ek et al. (2013) suggested that this metasom-atic event occurred immediately after the onset of high-temperature breakdown of relict garnet in the protolith ofthe peridotites and probably shortly before the eruption ofthe Zinst basanite.The mineralogy and mineral chemistry of the melt

pockets found in the three samples selected for detailedstudy reveal some important similarities as well as differ-ences. Whereas the melt pockets in samples ZIN14 andTEI2B contain a similar mineral association (cpx2/ol2þ cbþplgþmeltþ spl2� ilm), the melt pockets inZIN11 exhibit a more complex mineral association ofcbþ ol/cpx2þ afsþmelt� ap� ilm� crich, resulting inthe prominent K and LREE enrichment in the latter(Table 2). This is most easily explained by an additional

Fig. 12. The d7Li vs Li variation in NE Bavaria mantle xenoliths (symbols as in Fig. 3). Data for other xenoliths worldwide are also plotted; onlymeasured whole-rock values were considered and no d7Li values reconstructed from analyses of individual mineral phases were included. Datesources: Mongolia, Magna et al. (2006, 2008) and Pogge von Strandmann et al. (2011); Vitim, Avacha, Ionov & Seitz (2008), Halama et al.(2009) and Pogge von Strandmann et al. (2011); Tok, Pogge von Strandmann et al. (2011); Zabargad, Brooker et al. (2004); Gakkel Ridge, Gaoet al. (2011); South Korea, Kil (2010). Two whole-rock analyses with high d7Li values from Zabargad (Brooker et al., 2004) are indicated witharrows, as they plot outside the range of the figure.


24

overprint of an older metasomatic association by later,post-entrainment metasomatic reaction with the mobilecomponents of the host basanite infiltrating into thexenolith.

Alkaline and carbonate-rich meltmetasomatismMantle metasomatism by percolating melts or fluids ofvarious compositions represents the key process of mantleenrichment (e.g. Frey & Green, 1974; Menzies & Hawkes-worth, 1987; Downes, 2001). This includes metasomatismby (alkaline) basaltic melts (e.g. Bodinier et al., 1990;Zanetti et al., 1996; Witt-Eickschen et al., 1998; Ionov et al.,1999; Coltorti et al., 2007; Gregoire et al., 2009, 2010),

Table 8: Whole-rock major and trace element

compositions of host basalts

Sample: B-10 B-9 B-11

Rock: Basanite Basanite Basanite

Locality: Zinst Hirschentanz Teichelberg

wt %

SiO2 43·95 41·48 39·46

TiO2 1·75 2·12 2·57

Al2O3 10·86 10·98 10·90

Fe2O3 4·30 5·20 6·07

FeO 7·36 7·28 6·92

MnO 0·18 0·19 0·20

MgO 14·99 14·38 13·84

CaO 10·77 11·28 12·62

Na2O 2·82 2·79 2·71

K2O 0·71 0·89 1·10

P2O5 0·59 0·75 0·83

H2O– 0·35 0·46 0·52

H2Oþ 0·96 1·36 1·58

CO2 0·24 0·63 0·28

Total 99·83 99·79 99·60

ppm

Sc 22 23 25

Rb 23 34 26

Sr 754 922 993

Y 20 22 23

Zr 192 259 286

Nb 64 77 98

Cs 0·48 0·95 0·69

Ba 455 523 571

La 42 52 66

Ce 82 101 123

Pr 10 12 15

Nd 40 51 58

Sm 7·6 9·3 10

Eu 2·5 2·9 3·1

Gd 7·6 8·9 9·8

Tb 1·0 1·2 1·2

Dy 4·7 5·3 5·4

Ho 0·8 0·9 0·9

Er 2·3 2·5 2·6

Tm 0·26 0·28 0·29

Yb 1·7 1·7 1·8

Lu 0·23 0·25 0·26

Hf 4·5 5·9 6·6

Ta 6·9 5·5 7·8

Pb 2·6 2·2 2·6

Th 5·7 5·7 7·4

U 1·3 1·6 1·7

Fig. 13. (a) d7Li vs modal olivine in the NE Bavaria xenolith suite(symbols as in Fig. 3). (b) d7Li vs Li/Yb in NE Bavaria peridotitescompared with other localities. Data sources as in Fig. 12. Yb datafrom Stosch et al. (1986), Brooker et al. (2004), Ionov et al. (2005, 2006),Kil (2007; Yb in cpx only), Liu et al. (2008; Yb in cpx only), Magnaet al. (2008), Halama et al. (2009) and Ionov (2010). PM, primitivemantle, Li/Yb from Jagoutz et al. (1979) (see main text for d7Li in theprimitive mantle).


25

alkaline or Fe^Ti-rich fluids or melts (e.g. Ionov, 1998;Gregoire et al., 2000a; Kalfoun et al., 2002), carbonatiticmelts (e.g. Yaxley et al., 1991; Ionov et al., 1993; Rudnicket al., 1993; Coltorti et al., 1999; Gorring & Kay, 2000) andsubduction-related fluids or melts (e.g. Zanetti et al., 1999;Gregoire et al., 2001; Coltorti et al., 2007; Yoshikawa et al.,2010).The xenolith suite in this study shows similar, distinct

signs of pervasive melt infiltration resulting in modal(melt pockets) and cryptic metasomatism. The evidenceincludes LREE, Li, Rb, U, Nb, Ta, Pb and P enrichmentsin all xenolith samples, variable d7Li values from þ2·5 to�9·7ø and the presence of carbonate-bearing silicatemelt pockets in some xenoliths. The mineralogy and min-eral chemistry of the melt pockets in the xenolith suiteand the whole-rock major and trace element data supportoverprinting of the xenoliths by Na^P^CO2-rich metasom-atic agents and may suggest a combination of alkaline andcarbonatitic melt metasomatism. However, the geochem-ical data show no simple correlation between the extent ofmetasomatism, such as CaO/Al2O3 or Mg#, and incom-patible trace element enrichment and indicators of alkalineand carbonatitic metasomatism (e.g. Ti/Eu vs LaN/YbN;Coltorti et al., 1999). This may, in part, be due to the fact

that alkaline and carbonatitic metasomatism often resultsin contrasting metasomatic effects (e.g. Ti enrichment foralkaline melts vsTi depletion usually observed in carbona-titic melt metasomatism; Bizimis et al., 2003), trace elementfractionation during melt percolation (e.g. Navon &Stolper, 1987) and/or modal metasomatism resulting in theformation of new phases such as cpx 2, carbonate, apatiteand Ti^Zr oxides within melt pockets (e.g. Neumannet al., 2000, 2002).Alkali-rich silicate melts typically have elevated CO2

contents (Brey & Green, 1976), probably reflecting anorigin by low-degree melting of a carbonated peridotiticsource (e.g. Edgar, 1987, and references therein).Interaction of such melts with peridotite usually results inthe precipitation of K-rich hydrous phases such as amphi-bole or mica, coupled with LREE^HFSE enrichment andlower Mg# values in the peridotites (Dawson & Smith,1982; Hawkesworth et al., 1984; Menzies & Hawkesworth,1987; Bodinier et al., 1988; Fabries et al., 1989; Harte &Hawkesworth, 1989; Wulff-Pedersen et al., 1996; Ionovet al., 1997; Gregoire et al., 2000b; Puziewicz et al., 2011).This would be in agreement with the overall LREE en-richment observed in the NE Bavaria xenoliths (Fig. 6)and lower Mg# of the whole-rocks and mineral phases,coupled with elevated HFSE contents in most samples.However, except for sample ZIN11, which contains meltpockets with predominant alkali feldspar, the K enrich-ment is only minor, expressed by low K2O contents inwhole-rocks and the presence of Na-rich plagioclasewithin the melt pockets in samples ZIN14 andTEI2B.On the other hand, the elevated whole-rock Ca/Al ratios,

coupled with LREE and LILE enrichment and Zr^Hfand U^Th fractionation, as well as the abundance of apa-tite, are often considered as characteristic signatures of car-bonatitic metasomatism (Yaxley et al., 1991, 1998; Hauriet al., 1993; Ionov et al., 1993, 1994; Rudnick et al., 1993;Coltorti et al., 1999; Lenoir et al., 2000). All these signaturescan also be recognized in the NE Bavaria xenolith suite(Table 2, Figs 6 and 7) together with the presence of

Table 10: Rb^Sr and Sm^Nd concentrations and isotopic data for xenolith-hosting basalt samples from Zinst, Hirschentanz

andTeichelberg, NE Bavaria, Bohemian Massif

Sample Locality Age

(Ma)

Rb

(ppm)

Sr

(ppm)

87Rb/86Sr 87Sr/86Sr(m) 87Sr/86Sr(t) Sm

(ppm)

Nd

(ppm)

147Sm/144Nd 143Nd/144Nd(m) 143Nd/144Nd(t) eNd(t)

B-10 Zinst 21·2 23 754 0·088 0·703479� 9 0·703454 7·6 40 0·1151 0·512827� 11 0·512811 þ4·1

B-9 Hirschentanz 23·5 34 922 0·107 0·703465� 9 0·703425 9·3 51 0·1114 0·512828� 9 0·512811 þ4·1

B-11 Teichelberg 22·1 26 993 0·076 0·703337� 10 0·703316 10 58 0·1055 0·512856� 9 0·512841 þ4·7

Rb, Sr, Sm and Nd concentrations were determined by ICP-MS; m, measured ratio; error given as 2sm; eNd correspondsto the measured ratio using for CHUR 143Nd/144Nd¼ 0·512630 and 147Sm/144Nd¼ 0·1960 (Bouvier et al., 2008).

Table 9: Results of K^Ar ages for NE Bavaria volcanic

rocks

Sample Locality K (%) 40Ar(rad)

(cm3 STP g–1)

40Ar(rad)

(%)

Age

(Ma)

1s

B-10 Zinst 0·658 5·454� 10–7 32·7 21·2 1·1

B-9 Hirschentanz 0·782 7·201� 10–7 32·7 23·5 1·2

B-11 Teichelberg 0·963 8·315� 10–7 37·9 22·1 1·1


26

carbonate within melt pockets in samples ZIN14 andTEI2B and the more complex cbþ ol/cpx2þmelt� ap� ilm� crich mineral assemblage found in sample ZIN11.Except for the presence of Ti-rich phases, the mineralogyof the melt pockets in sample ZIN11 is similar to thatdescribed from Svalbard mantle xenoliths (Amundsenet al., 1987; Ionov et al., 1993) interpreted as a product ofmantle metasomatism by carbonate-rich fluids (Ionovet al., 1993, 1996). Although these three xenoliths could beconsidered as products of carbonatitic metasomatism,their low whole-rock Mg# values, overall enrichment inHFSE and the presence of cpx2 in carbonate-bearing meltpockets significantly enriched in TiO2 (up to 7·0wt %)are factors against simple interaction between peridotiteand a pure carbonatitic melt, because such a melt is mark-edly depleted in HFSE as a result of preferential partition-ing into residual pargasite, clinopyroxene, and ilmenite(Green & Wallace, 1988). The clear association of carbon-ate^apatite with alkaline melt pockets, the presence oflarge (up to 1mm) carbonate pockets hosted in silicatemelt pockets and the low REE contents in the carbonates(Table 5) compared with quenched carbonatitic melts(e.g. Moine et al., 2004) are features strongly in favourof the carbonate occurrence being connected with mag-matic fractionation of an alkaline and/or alkali^carbonatemelt (e.g. Giuliani et al., 2012). Such a conclusion is inagreement with the occurrence of wehrlite and apatite-bearing clinopyroxenites in the nearby area, interpretedas the products of alkaline^carbonatitic melts (Geissleret al., 2007).

The incompatible element composition of the alkalinesilicate melt invading the peridotites cannot be calculatedfrom the composition of the clinopyroxene and Dcpx/melt,because the clinopyroxene does not represent the onlyphase contributing to the trace element budget (seebelow). On the other hand, owing to the clear modal meta-somatism in some xenoliths, the composition of the melthas been inferred from the complex mineralogy and chem-ical composition of the melt pockets. It has been shownabove that the melt pockets have compositions differentfrom those of the host basalts, indicating an origin by meltinfiltration at upper mantle conditions. The compositionof the silicate melt quench (intermediate SiO2 contents of50·9^59·0wt % andTiO2/Al2O350·07) most probably re-flects reaction between an infiltrating alkali basaltic meltand peridotite (Neumann & Wulff-Pedersen, 1997) ratherthan a primary melt composition. Its alkali-rich compos-ition (Na2OþK2O up to 9·6wt %), coupled with the pres-ence of plagioclase (ZIN14, TEI2B) or alkali feldspar

Fig. 15. Whole-rock major element variations of FeO (wt %) vs SiO2,Al2O3 and MgO (wt %) for NE Bavaria xenoliths. Batch melt extrac-tion curves for 1, 2, 3, 5 and 7GPa melting of primitive mantle(McDonough & Sun, 1995) adopted fromWalter (2004).

Fig. 14. Melt extraction estimates for the NE Bavaria xenoliths basedon whole-rock major element composition (MgO, Al2O3, SiO2). Themelt extraction curves at 1 and 2GPa were constructed using the ex-perimental data of Herzberg (2004). Figure adopted from Harveyet al. (2012).


27

(ZIN11) and Al�Na-rich cpx 2 within the pockets are fea-tures strongly in favour of reaction between peridotite andalkali-rich basaltic melt. The trace element compositionsof cpx 2 and the quenched melt (Fig. 10) provide more de-tails on the incompatible element composition of this infil-trating melt, which was apparently strongly enriched inREE (up to 229 ppm total REE in cpx 2) and Zr^Nb, butsignificantly depleted in U,Th and Pb. The absence of hy-drous metasomatic phases such as amphibole and/or micain our xenolith suite points to high CO2/H2O ratios in theinfiltrating alkaline melt, which is in agreement with ex-perimental studies (Green & Wallace, 1988). ElevatedCO2 contents in the garnet peridotite sources of basaltsfrom the Ohr› e/Eger Rift were suggested by Haase &Renno (2008). Further evidence for elevated CO2 contentsin the upper mantle of the western part of the rift is pro-vided by CO2-rich gas emanations with 3He/4He and d13Ccompositions implying their derivation from the mantle(Weinlich et al., 1999). Fractionation of such a CO2-bearingsilicate melt will result in increasing CO2 contents andCO2/SiO2 ratio in the residual melt, which would lead to

the separation of an immiscible CO2-rich melt or fluid(Schiano & Clocciatti, 1994; Schiano et al., 1994; Harveyet al., 2010) and precipitation of carbonate and quartz, asobserved in sample ZIN11. Additionally, very high F andCl contents in apatite (3·84 and 0·55wt %, respectively)point to elevated contents of these elements in the infiltrat-ing melt.

The source of the infiltrating melts:evidence for a recycled component?The mantle source of the magmatism within the majorpart of the Ohr› e/Eger Rift has been evaluated based onthe compositions of volcanic rocks occurring within therift and on its shoulders (Haase & Renno, 2008). At leastthree mantle source components can be distinguishedusing Sr^Nd^Pb isotopic data and incompatible traceelement systematics.Volcanic rocks in the western continu-ation of the rift, including the Zinst, Hirschentanz andTeichelberg localities, show considerable enrichment in in-compatible elements, suggesting either lower degrees ofpartial melting and/or enriched mantle sources, repre-sented by amphibole-bearing mantle peridotite (Haase &Renno, 2008). Although the peridotites investigated hereprovide no evidence for the presence of either amphiboleor low degrees of partial melting, we do see evidence foran enriched mantle source. We argue below that this en-richment may be the result of recycled (subducted) crustallithologies within the upper mantle column.The NE Bavarian xenoliths occur in volcanic rocks that

intruded the Saxothuringian tectonic unit of the BohemianMassif, the evolution of which is closely connected witheastward subduction of oceanic crust (Saxothuringianocean) beneath the Tepla¤ ^Barrandian unit during Devon-ian^Carboniferous times (Franke, 2000; Konopa¤ sek &Schulmann, 2005; Schulmann et al., 2009). Relics of oceaniccrust preserved as eclogites and metabasites are wide-spread within the Saxothuringian terrane (e.g. Stosch &Lugmair, 1990; Schma« dicke et al., 1992). The xenolith-bear-ing localities are close to the Saxothuringian^Moldanu-bian terrane boundary and a triple junction of the mantlelithosphere domains that are characterized by differentseismic anisotropy (Babus› ka & Plomerova¤ , 2010). However,there is no direct evidence for a different chemical compos-ition of these domains (e.g. Haase & Renno, 2008). Thetrace element and isotopic similarity between the primitiveCenozoic basalts of the Bohemian Massif and Permo-Car-boniferous volcanic rocks from the same area led Ulrychet al. (2002) to propose that their HIMU-like mantlesource already existed in Permian times and was formedby Devonian subduction-related metasomatism of themantle lithosphere.The importance of pyroxenite and/or eclogite in the gen-

eration of basalt magmas was discussed by Hirschmann& Stolper (1996) and Sobolev et al. (2007), who suggestedthe involvement of �2^20 vol. % of recycled crust (eclogite

Table 11: Calculated partial melting degrees for NE

Bavaria mantle xenoliths

Sample Locality Lithology Cpx mode

(vol. %)

F (%)1 F (%)2

10ZIN1 Zinst lherzolite/harzburgite 6 14 20

10ZIN2 Zinst lherzolite 7 14 19

10ZIN3 Zinst harzburgite/lherzolite 3 17 24


10ZIN5 Zinst harzburgite/lherzolite 4 14 22


ZIN9 Zinst lherzolite 11 12 6

ZIN11 Zinst lherzolite 12 11 n.d.

ZIN14 Zinst lherzolite 13 8 n.d.

ZIN19 Zinst lherzolite 6 18 21

ZIN27 Zinst dunite–wehrlite 7 18 23

ZINx2 Zinst lherzolite 10 12 13

ZINx5 Zinst lherzolite/harzburgite 5 16 26

ZINx8 Zinst lherzolite/harzburgite 5 17 16

HIR3 Hirschentanz lherzolite 12 14 7




HIR16 Hirschentanz lherzolite/harzburgite 6 12 19

TEI2B Teichelberg lherzolite/harzburgite 5 16 19

1Degree of partial melting based on Cr# of spinel(Hellebrand et al., 2001, 2005).2Degree of partial melting based on whole-rock MgO con-tent (Niu, 1997).n.d. not determined.


28

or pyroxenite) during mantle melting. Melting experi-ments on carbonated eclogite (Hammouda, 2003; Das-gupta et al., 2004; Yaxley & Brey, 2004) suggest thateclogite will melt preferentially over peridotite, and thatmelting of a mixed peridotite^eclogite source can producealkali basalts with variable Mg#s that are lower thanthose of typical peridotite-derived melts (Kogiso &Hirschmann, 2006). Such melts can, in turn, be responsiblefor metasomatism that will lower the Mg#, as is apparentin some of the peridotites from this study (e.g. ZIN11,ZIN14). A similar scenario was suggested for Fe-rich peri-dotites from Calatrava, Spain (Bianchini et al., 2010),which contain carbonate-bearing melt pockets with com-positions almost identical to those of the NE Bavaria xeno-liths. Further support for recycled material in the sourceof infiltrating melts may be provided by high P contentsin the whole-rocks (0·02^0·29wt % P2O5; Table 2) com-pared with primitive mantle values. Although some ofthese high P contents can be explained by the occurrenceof apatite within melt pockets in some xenoliths, they canalso be connected with the presence of discrete P-bearingglasses interpreted as percolating melts originating frompartial melting of subducted sedimentary material byRosenbaum et al. (1997).The Sr^Nd^Li isotopic systematics represent powerful

tools for tracing recycled components (e.g. Medaris et al.,1995; Ishikawa et al., 2007; Penniston-Dorland et al., 2010;Melchiorre et al., 2011; Zeng et al., 2011). The relatively high87Sr/86Sr ratios between �0·7033 and 0·7035 at143Nd/144Nd of �0·51281^0·51284 in volcanic rocks fromZinst, Hirschentanz and Teichelberg (Table 10) are similarto those reported by Haase & Renno (2008), which thoseresearchers interpreted to reflect mixing between twomantle components with similar Nd isotopic composition,but variable Sr isotopic ratios between �0·7032 and0·7036.Whereas the clinopyroxenes from the mantle xeno-liths have Nd isotope compositions similar to those of thehost basalts and other xenoliths from the CEVP, harzburg-ite 10ZIN5 from Zinst has a significantly more radiogenic87Sr/86Sr of �0·7041 (Fig. 11). Despite the limited amountof data, the radiogenic 87Sr/86Sr in 10ZIN5 coupled with a143Nd/144Nd similar to that of the host basalts and threeother lherzolites analyzed for their Sr^Nd isotopic com-positions (10ZIN2, ZINx2, HIR6) may provide evidencefor selective overprinting of the Sr in the Zinst samples bySr-rich melts or fluids derived from a subducting slab and/or the presence of recycled material in the source of themelts.Most of the xenoliths in this study are variably enriched

in Li compared with the primitive mantle, with substantialenrichments in clinopyroxene (up to 33 ppm; Table 5) sug-gesting significant Li addition from the infiltrating melt.The large variations in d7Li (þ2·5 to �9·7ø) are similarto those reported for peridotites metasomatized by

subducted crustal materials (Zhang et al., 2010), and formantle xenoliths that have interacted with Na-carbonatiticmelts (Su et al., 2012). The low d7Li values in the NEBavaria xenoliths are paralleled by high to extreme Li/Ybratios (18^143; Fig. 13b) that are fairly uncommon formantle xenoliths worldwide and far from the Li/Yb of�4·5 estimated for the terrestrial upper mantle (Jagoutzet al., 1979). These high Li/Yb ratios appear to result fromslight Li enrichment (�2^3� pristine mantle Li abun-dance; Ryan & Langmuir, 1987) coupled with largeYb de-pletion (in general50·09 ppm), probably caused by largedegrees of melting that exhausted a substantial proportionof the HREE. Similarly lowYb contents have been foundin Avacha spinel harzburgites (Ionov, 2010) with Li/Ybranging from 38 to 109 but with largely normal mantled7Li values (Ionov & Seitz, 2008; Pogge von Strandmannet al., 2011). The larger range in both d7Li and Li/Yb forthe Zinst suite relative to the Hirschentanz^Teichelbergsuite appears to be related to a greater extent of physicaldisturbance in the former suite, as supported by petro-graphic evidence. This, coupled with non-uniform correl-ation between d7Li and Al2O3, may hint at differentprocesses controlling the d7Li variations and may implyeasier invasion of metasomatizing fluids into the Zinstsuite of xenoliths.Two alternatives may be assessed to explain the observed

extreme variation of Li isotope compositions in mantlexenoliths toward negative values: (1) mixing with a low-d7Li reservoir and/or overprinting by low-d7Li fluids ormelts; (2) kinetic fractionation during ingress of Li. Bothalternatives must be considered equal, or they may evenbe combined. Recent Os isotope data for NE Bavariaxenoliths appear to provide some support for a contribu-tion of recycled crustal material in the percolating melts(Ackerman et al., 2013). The mechanism of kinetic isotopefractionation cannot be evaluated with the current datasetbecause of the lack of relevant in situ data; further studiesare required to resolve this.(1) Low d7Li values have been reported for rocks such as

granulites (d7Li as low as �18ø; Teng et al., 2008) andeclogites (d7Li as low as �22ø; Zack et al., 2003;Marschall et al., 2007; Halama et al., 2011). In parallel, alow-d7Li crustal reservoir has been advocated by Hamelinet al. (2009) in the petrogenesis of evolved alkaline volcanicrocks (benmoreites, trachytes) from the Massif Centraland explained by assimilation of an isotopically lightlower crustal component, such as a metapelite. However,melting of even a small portion of such a metapeliticsource could not reproduce the major and trace elementvariations as well as the very low d7Li observed in the NEBavaria xenoliths (see Qiu et al., 2011). Lithium contents ingranulites (523 ppm, but usually below 5 ppm; Teng et al.,2008) and garnet-bearing metapelites (511ppm; Qiu et al.,2011) are too low to explain the observed enrichment in


29

clinopyroxene; granulites or their melts will also probablyhave different trace element characteristics (e.g. Bea &Montero, 1999; Janous› ek et al., 2004). Tang et al. (2012) havesuggested that eclogites could be the ultimate source ofthe low-d7Li melt or fluid that metasomatized peridotitexenoliths from the North China Craton whereas Su et al.(2012) have advocated carbonatite melts as the low-d7Licomponent. Secondary carbonate probably has very lowLi contents; the ZIN11, ZIN14 and TEI2B carbonates areindeed highly depleted in Li (Table 5). To a certain extent,this may disqualify carbonate metasomatism as a sourceof elevated Li concentrations. Moreover, those sampleswith abundant carbonate do not show a systematic d7Libias from the other NE Bavaria xenoliths. The presence ofeclogitic lithologies in the mantle beneath the BohemianMassif may be assigned to Devonian^Carboniferous sub-duction of Saxothuringian lithosphere (e.g. Schulmannet al., 2009). A simplified binary-mixing scenario betweenpristine mantle and a nearby Mu« nchberg eclogite isplotted in Fig. 12. Preferential melting of Li-rich eclogitescould account for the observed negative [Li]^d7Li vari-ation and the apparent scatter could easily be explainedby non-uniform Li abundance and variable d7Li signaturein clinopyroxene. Such heterogeneous distribution of Liisotopes has been observed in many examples (e.g. Zacket al., 2003; Nishio et al., 2004; Rudnick & Ionov, 2007;Tang et al., 2011). We note that clinopyroxene from pristineperidotites usually has d7Li higher than olivine and ortho-pyroxene (Magna et al., 2006; Jeffcoate et al., 2007).However, the absence of a correlation between Li contents,degree of metasomatism (e.g. Ca/Al) and d7Li, as well asrather low Li/Yb ratios in eclogites, are all factors againstsimple mixing of peridotite with infiltrating melts.(2) Kinetic effects have been observed to severely modify

the intrinsic intra-mineral Li isotope systematics of clino-pyroxene and orthopyroxene from peridotite mantle xeno-liths (e.g. Lundstrom et al., 2005; Jeffcoate et al., 2007;Rudnick & Ionov, 2007; Aulbach et al., 2008; Ionov &Seitz, 2008; Aulbach & Rudnick, 2009). It is important tostress that clinopyroxene, in particular, inherits very lowd7Li values through faster 6Li diffusion, whereas olivine ismore resistant to diffusive modification (Jeffcoate et al.,2007; Parkinson et al., 2007; Rudnick & Ionov, 2007). Thesuperior speed of 6Li in diffusion has been evidenced innatural mantle settings by newly formed melt pockets co-existing with clinopyroxene that is isotopically light rela-tive to that coexisting with melting olivine (Magna et al.,2008). High Li contents associated with low d7Li in clino-pyroxene are often considered a hallmark of diffusive in-gress of light Li (Rudnick & Ionov, 2007; Tang et al., 2011).We stress that Li contents in cpx1 and cpx2 from the NEBavaria suite (Table 5) are not uniformly high, neither areperidotites with high-Li clinopyroxene associated withlow bulk d7Li values. Nevertheless, it is still conceivable

that part of the variation can be explained by recent diffu-sive influx of Li from the surrounding melt (see Aulbachet al., 2008); further detailed investigations are required toresolve this.It is interesting to note that mantle xenoliths always have

lower d7Li than their respective host alkali basalts (seeMagna et al., 2008). This can be illustrated by comparingthe average Li content and Li-isotope composition of xeno-lith samples with the lowest Li/Yb and d7Li values in therespective host basanites, which are clearly off by41·6ø.A similar difference of �4ø has been recorded betweenmoderately LREE-depleted spinel lherzolite and its hostbasalt from Atsagin Dush, Mongolia (Magna et al., 2008).It may be feasible for Li isotopes to kinetically exchangebetween an alkali basaltic melt and peridotite over a shorttime interval en route to the surface (Lundstrom et al.,2005; Aulbach et al., 2008); however, we cannot evaluatethese observations with the results of Rudnick & Ionov(2007) owing to the lack of whole-rock xenolith data intheir study, although they envisaged infiltration of Lifrom the host basalt.

Constraints on trace element distributionwithin mineralsMass-balance calculations show that four analysed clino-pyroxenes (10ZIN2, ZINx2, ZIN14 and TEI2B) host mostof the REE and Y. In contrast, clinopyroxenes from sam-ples 10ZIN5, HIR6 and ZIN11 host only up to 40^70% ofthe middle rare earth elements (MREE), HREE and Y,and less than 40% of La and Ce. With regard to HFSE,clinopyroxenes can account for variable proportions be-tween 20^30% (10ZIN5, HIR6) and 70^100% of the totalHFSE inventory (10ZIN2, ZIN11, ZIN14, ZINx2, TEI2B).Except for sample ZIN14, in which the clinopyroxene isstrongly enriched in Th and U (Table 5), clinopyroxenehosts only a small fraction of the bulk-rock Th and Ubudget (530% Th and510% U).The Sr budget is variablycontrolled by clinopyroxene (10^80%), with the lowestvalues calculated for samples with abundant carbonates(ZIN11, ZIN14). This is in agreement with our trace elem-ent analyses of carbonate, suggesting that it plays only alimited role as a host of incompatible trace elements,except for Sr, Ba and, to a lesser extent, Th and U. On theother hand, Sr and Ba can be largely accommodated infeldspar (e.g. Gregoire et al., 2000a). The very low Rb con-centrations in cpx1 (�0·5 ppm) compared with highwhole-rock Rb contents (1·9^2·5 ppm) suggest that, forthe samples with carbonate-bearing pockets (ZIN11,ZIN14, TEI2B), Rb distribution is controlled solely by thepresence of feldspar and/or Rb-rich silicate melt (e.g.TEI2B with 54 ppm Rb; Table 5). For samples without sec-ondary melt pockets (Table 1), it is likely that Rb is hostedin some as yet unidentified phase(s) and/or grain bound-ary component (e.g. Bedini & Bodinier, 1999). Very lowPb contents detected in clinopyroxenes compared with


30

whole-rocks suggest only a limited role (520% of total Pbbudget) for clinopyroxene in Pb partitioning among min-eral phases. Gregoire et al. (2000b) argued that olivine cancontrol the Pb budget in the upper mantle. However, wesuggest that mantle sulphides, occasionally present in thexenolith suite, may control Pb owing to the capability ofsulphide to concentrate up to several parts per million ofPb (Hart & Gaetani, 2006; Burton et al., 2012; L.Ackerman, unpublished data).

CONCLUSIONSPeridotite mantle xenoliths from Zinst, Hirschentanz, andTeichelberg (NE Bavaria, Bohemian Massif) are hosted inCenozoic basanite lava flows (21·2^23·5 Ma), forming partof the Central European Volcanic Province. Whole-rockmajor element variations and spinel chemistry suggestvariable (�6^30%) degrees of melt extraction from theirprotolith in the spinel stability field and subsequent perva-sive enrichment by alkaline and carbonate-rich melts thatresulted in modal and cryptic metasomatism.The evidenceincludes progressive Li, LREE, Rb, U, Pb, HFSE and Penrichment and the presence of carbonate-bearing silicatemelt pockets. The clear association of carbonate and apa-tite with alkaline melt pockets and the presence of largedomains with carbonate within some of the silicate meltpockets strongly suggest that the carbonate occurrence isconnected with the fractionation of an alkaline silicatemelt and/or alkali^carbonate melt, rather than represent-ing metasomatism by a pure carbonatitic melt.

The Sr^Nd^Li isotopic systematics with variable87Sr/86Sr ratios between �0·7032 and 0·7041 and signifi-cantly negative d7Li values down to �9·7ø may indicatean important contribution of recycled crustal materialsuch as eclogite in the infiltrating melts. This might be con-nected with the geodynamic setting of the host basaltsthat intruded the Saxothuringian basement terrane, theevolution of which was closely connected with eastwarddipping subduction of oceanic lithosphere (Saxothuringianocean) during Devonian^Carboniferous times. Alterna-tively, kinetic diffusive fractionation could have played animportant role in 7Li/6Li modifications with predominantenrichment in light Li isotope compositions in those xeno-liths whose protoliths were most severely deformed byprevious tectonic events.The trace element geochemistry of clinopyroxene, car-

bonate, and silicate melt pockets implies that clinopyrox-ene controls most of the MREEþHREE, HFSE and, to alesser extent, also the LREE and Sr whole-rock budgets.Carbonate plays only a subordinate role as a host of incom-patible trace elements, except for Sr, Ba and, to a lesserextent, Th and U. In contrast, Rb distribution can be con-trolled by the presence of feldspar and/or Rb-rich silicatemelt in melt pocket-bearing xenoliths.

ACKNOWLEDGEMENTSWe thankVlasta Bo« hmova¤ for microprobe analyses, S› a¤ rkaMatous› kova¤ for whole-rock ICP-MS analyses, JanaD› uris› ova¤ for help with LA-ICP-MS analyses, Jitka

Fig. 16. Whole-rock trace element composition of melt pocket-bearing samples (ZIN11, ZIN14,TEI2B) and the host basalts.


31

M|¤kova¤ and Vladislav Chrastny¤ for maintenance of theclean lab and MC-ICP-MS facility, and Vojte› ch Janous› ekfor helpful discussions. Detailed reviews by Jason Harvey,Roberta Rudnick and an anonymous reviewer helped toimprove the paper significantly.

FUNDINGThis research was supported by the projects 205/09/1170,P210/12/1990 and P210/12/0573 (Czech Science Foundation)and the Scientific Programme CEZ: AV0Z30130516 andRVO67985831 of the Institute of Geology v.v.i., Academyof Sciences of the Czech Republic.

SUPPLEMENTARY DATASupplementary data for this paper are available at Journalof Petrology online.

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