Petrology and geochemistry of granulite xenoliths beneath...

Mineralogy and Petrology (2005) 85: 269–290DOI 10.1007/s00710-005-0090-8

Petrology and geochemistry of granulitexenoliths beneath the Nograd-GomorVolcanic Field, Carpathian-PannonianRegion (N-Hungary===S-Slovakia)

I. Kovacs� and C. Szabo

Department of Petrology and Geochemistry, Lithosphere FluidResearch Lab, E€ootv€oos University, Hungary

Received July 16, 2004; revised version accepted April 12, 2005Published online October 12, 2005; # Springer-Verlag 2005Editorial handling: K. St€uuwe

Summary

Abundant upper mantle and rare lower crustal xenoliths have been found in the Plio-Pleistocene alkali basalts of the N�oograd-G€oom€oor Volcanic Field, situated in thenorthern Pannonian Basin, on the border between northern Hungary and southernSlovakia. A few lower crustal granulite xenoliths have been found in a small basalticpyroclastic cone at Baglyask}oo. The mafic granulite xenoliths are plagioclase-bearinghornblende clinopyroxenites, plagioclase-bearing clinopyroxene hornblendites, andplagioclase-bearing clinopyroxenites. They contain unusual symplectites, composedof spinel, feldspar and clinopyroxene. These symplectites are interpreted as the prod-uct of garnet breakdown. Following the breakdown reaction, the symplectite un-derwent in situ partial melting. Mineral constituents of these granulite xenoliths havechemical compositions similar to those of other granulite xenoliths worldwide. How-ever, a distinctive positive Pb and Ce anomaly in mineral constituents of these gran-ulites is characteristic.

Granulite xenoliths from the N�oograd-G€oom€oor Volcanic Field must have experiencedgranulite facies metamorphism at pressures that correspond to the ‘original’ thickness ofthe crust (>1.1 GPa; >�30 km), whereas the breakdown reaction of garnet and subse-quent melting and recrystallization of clinopyroxenes in the symplectites happened atshallower depths close to the present-day MOHO (0.6–0.7 GPa; �16–19 km).

� Present address: Research School of Earth Sciences, Australian National University,Australia

Introduction

Ultramafic xenoliths hosted in alkali basalts and kimberlites provide significantevidence about physical and chemical processes of the deeper part of the litho-sphere (Nixon, 1987; Downes, 2001). A wide compositional range of xenolithsoccurs in the N�oograd-G€oom€oor Volcanic Field (NG), situated in northern Hungary=southern Slovakia on the northern side of the Pannonian Basin. This gives a greatopportunity to study the entire lithospheric section and reveal the potential con-nection with the geodynamic evolution of the area, with special respect to theMiocene rifting events, which provide an excellent geodynamic frame to fit inthe information that has been obtained from the xenoliths.

Basic petrologic studies have been already performed by Szab�oo and Taylor (1994)and Huraiova and Konecny (1994) on the Type-I xenoliths (i.e. peridotites represent-ing residual mantle material showing textural and geochemical evidence for a com-plex history in the sense of Frey and Prinz (1978)) indicating mantle events such asmantle veining and metasomatism during the evolution of the subcontinental litho-spheric mantle beneath the region. Type-II xenoliths (i.e. pyroxene-rich mantle rocksthat are either the results of metasomatic alteration of Type-I xenoliths or crystal-lization of melts in the mantle (Frey and Prinz, 1978)) have been also described indetail by Hurai et al. (1998) and Kovacs et al. (2004). These rocks, referred also ascumulate series, are the results of underplating of mafic igneous magmas and thesubsequent metasomatic processes prior to the host alkaline basaltic volcanism. How-ever, granulite xenoliths from the area have not yet been reported.

Granulite xenoliths provide information on the evolution and geochemistry of thelower continental crust. There are several lines of evidence that indicate that theyoriginate directly from the lower crust: 1) The mineralogy and estimated P-T equili-bration conditions correspond to appropriate lower crustal depths (0.6 to <1.4 GPa)(Griffin and O’Reilly, 1987); 2) The primitive composition of the host and the presenceof upper mantle peridotite xenoliths in the same vent indicate that the host magmaerupted quickly from great depth; 3) Decompression features, such as preferentialmelting of mafic phases (Padovani and Carter, 1977) and kelyphite formation on rimsand in cracks in garnets also indicate a rapid ascent of the xenoliths (Garvie andRobinson, 1984); 4) Finally, isotopic homogenization of minerals yields ages equalto the eruption age of the host basalt (Rudnick, 1992). However, granulite xenolithsshow clear differences from granulite terrains such as more mafic composition andelevated equilibrium pressure (greater depth of origin) (Bohlen, 1991; Rudnick, 1992).

Granulite xenoliths have already been extensively studied in the Bakony-Balaton Highland Volcanic Field (BBH; Fig. 1) of the central Pannonian Basin(e.g., Embey-Isztin et al., 1989, 2003; T€oor€ook, 1995; Dobosi et al., 2003; D�eegiand T€oor€ook, 2004). The N�oograd-G€oom€oor (NG) granulite xenoliths provide uniqueinsight into the evolution and nature of the lower crust beneath the northernedge of the Pannonian Basin, whereas the Bakony-Balaton Highland localityprovides information about the central part of the region (Fig. 1). We have carriedout the first detailed petrographic and geochemical study on the granulite xeno-liths from the Baglyask}oo cone (Fig. 1). We will show that, according to formationof symplectites, textural features, mineral assemblages and geochemical character-istics of the xenoliths, they underwent granulite facies metamorphism and then

270 I. Kovacs and C. Szab�oo

Fig. 1. Simplified geological sketch map of the Carpathian-Pannonian Region where theN�oograd-G€oom€oor Volcanic Field (NGVF) is highlighted. Location of the granulite xenoliths(Baglyask}oo) is indicated in the enlarged map of the NG (BBHVF Bakony-Balaton HighlandVolcanic Field, ETBVF Eastern Transylvanian Basin Volcanic Field, LHPVF LittleHungarian Plain Volcanic Field, SBVF Styrian Basin Volcanic Field)

Petrology and geochemistry of granulite xenoliths 271

reequilibrated at lower pressure, probably in response to crustal thinning duringbasin formation in the Miocene. Furthermore, these granulite xenoliths containunusual symplectites, which play a key-role in reconstructing the metamorphicevolution of the lower crust.

Geological setting and sampling

Xenolith-bearing Neogene to Quaternary alkali basalts and their pyroclastic de-posits are distributed sporadically within the Carpathian-Pannonian Region. Theyoccur in the Eastern Transylvanian Basin, Bakony-Balaton Highland, LittleHungarian Plain, Styrian Basin, and at N�oograd-G€oom€oor (Fig. 1) (e.g., Embey-Isztinet al., 1989, 2001; Kurat et al., 1991; Downes et al., 1992; Szab�oo and Taylor, 1994;Vaselli et al., 1995, 1996; Bali et al., 2002; Szab�oo et al., 1995, 2004 and referencestherein). The basement of the N�oograd-G€oom€oor volcanic field comprises the Gemericand Veporic units, which consist mostly of low- to medium-grade metamorphicrocks (Koroknai et al., 2001). In the cover sequence Tertiary sediments and volca-nic rocks such as Plio-Pleistocene alkali basalts and their pyroclasts and minorMiocene andesites occur (Fig. 1). The andesites are thought to be associated withsubduction of the European plate beneath the Carpathian-Pannonian Region (Szab�ooet al., 1992; Harangi et al., 2001). The alkali basalt volcanic activity is post-extensional (Embey-Isztin et al., 1993) and its magmas brought a great variety ofxenoliths to the surface.

We have sampled five relatively fresh xenoliths from the pyroclastic cone ofBaglyask}oo (Fig. 1) and, after detailed petrographic study, we chose the three leastaltered and largest (3–5 cm in size) xenoliths (NGB04, NBG10, and NBG12) forfurther studies. Based on their modal composition these xenoliths are mafic gran-ulites, becasue they contain feldspar and the proportion of mafic minerals is above30 vol% (in sense of http:==www.bgs.ac.uk=SCMR=). The three selected xenolithswere studied texturally with an optical microscope. Electron microprobe analyseswere performed on the constituent minerals of two xenoliths (NGB04, NBG10).LA-ICP-MS analysis on clinopyroxene, amphibole and feldspar were also appliedto these two xenoliths.

Petrography

The studied mafic xenoliths are composed of clinopyroxene, amphibole and subor-dinate plagioclase and spinel. On a petrographic basis, they are plagioclase-bearing

Table 1. Modal composition of the NG granulite xenoliths

Modal assemblages Symplectites Rocks

sp-cpx sp-pl-cpx

NBG04 cpxþ ampþ spþ plþ gl þ þ plagioclase-bearing hornblende clinopyroxeniteNBG10 cpxþ ampþ spþ plþ gl þ þ plagioclase-bearing hornblende clinopyroxeniteNBG12 cpxþ ampþ spþ plþ gl � þ plagioclase-bearing hornblende clinopyroxenite

cpx clinopyroxene, amp amphibole, sp spinel, pl plagioclase, gl former glass


Fig. 2. Photomicrographs of fabrics and textural features in the NG granulite xenoliths.Photos were taken in plane-polarized light. a Zoned clinopyroxene: cpx-I in the center iscolorless, the surrounding darker overgrowth is cpx-II. Space among clinopyroxenes wasfilled with glass now altered to zeolites (indicated on the photomicrograph as matrix).b Dark amphibole (amp-I) patches in cpx-I. Light amp-II can be recognized as overgrowthon amp-I in the middle of the photomicrograph. c Symplectite after garnet. Sp-I can befound in the center of the symplectite where it is surrounded by pl-IB, pl-II and then cpx-II.d Cpx-II with sp-II octahedral inclusions. e Irregular pl-IB surrounded by pl-II in symplec-tite. Pl-II contains a large number of fluid and silicate-melt inclusions. amp-I first gen-eration of amphiboles, amp-II second generation of amphiboles, cpx-I first generation ofclinopyroxenes, cpx-II second generation of clinopyroxenes, pl-IA plagioclase of thegranulite’s groundmass, pl-IB plagioclases originated from garnet breakdown, pl-II secondgeneration of plagioclases, sp-I first generation of spinel, sp-II second generation of spinel,matrix former glass (zeoliteþ limoniteþ carbonate)


hornblende clinopyroxenites, plagioclase-bearing clinopyroxene hornblendites,and plagioclase-bearing clinopyroxenites. Their modal composition is shown inTable 1. Particular attention was given to the spinel-feldspar-clinopyroxenesymplectites that are keys for understanding the evolution of the granulite xenolithsand hence of the lower crust. Two groups of clinopyroxenes can be distinguished ineach xenolith. Clinopyroxene I (cpx-I) is slightly green and euhedral, varying from1 mm to 2.5 mm in diameter and comprises almost the whole xenolith (Fig. 2a).Amphibole (amp-I) (see below) patches are common in cpx-I (Fig. 2b). The sym-plectites are characterized by brown subhedral clinopyroxene II (cpx-II) of smallsize (250–600 mm) (Fig. 2c). Small, octahedral spinel (sp-II) inclusions often occurwithin them (Fig. 2d). Cpx-II, however, also occurs as an overgrowth on cpx-I(Fig. 2a). Amp-I is coarse-grained, similar to cpx-I, its size is between 1.5 and2 mm and it has a subhedral to euhedral shape. This amphibole often occurs assome tens of micron-sized patches in cpx-I (Fig. 2b). Amp-II is transparent andcontains no inclusions. It can be found as overgrowth either on cpx-I or on amp-I,with an average thickness of 40–50 mm (Fig. 2b). Spinel also occurs as two types.Sp-I exhibits large grain size (0.5–1.5 mm), irregular grain boundaries, grass greencolor with black rims and anhedral shape. The sp-I can be found in the middle ofthe symplectites where it is surrounded by plagioclase (pl-IB, pl-II) or cpx-II(Fig. 2c). Sp-II occurs in cpx-II as small (20–40 mm) octahedral inclusions.Plagioclase-I is anhedral and 0.5–0.75 mm in size. It can be found both in thevicinity of sp-I (pl-IB) and also as a major constituent of the granulite matrix,where it shows a size of 1.0–1.5 cm (pl-IA). Pl-II often occurs on the edge ofpl-IA (Fig. 2c) and of pl-IB in the symplectites (Fig. 2e), and contains large numberof fluid and silicate-melt inclusions. The latter ones occur as worm-like forms,causing spongy textures in the plagioclase (pl-II) (Fig. 2e).

We carried out a detailed petrographic study on the spinel-feldspar-clinopy-roxene symplectites by calculating their modal composition. The symplectites showsharp borders towards the enclosing large cpx-I and amp-I grains (Fig. 2c). Forthis calculation only minerals inside the symplectites were taken into consideration(i.e. sp-I, cpx-II, pl-IB, pl-II). Former glass in the symplectites is present as anassemblage of spherical zeoliteþ carbonateþ subordinate limonite. Sp-II wasexcluded from the calculation due to its small size and minor modal importance.At least 400 points were counted for each calculation (Table 2). In the symplectites,

Table 2. Modal composition (vol%) of symplectites in the NG garnulite xenoliths

NBG12 NBG04 NBG10

Phases I II III I II III IV V I II III IV

sp 47 55 9 19 24 32 14 8 4 25 26 10pl-IB, pl-II 7 12 41cpx 38 33 73 39 28 37 41 30 30 40 33 50gl 15 12 18 43 48 31 38 49 25 35 41 40

sp spinel, fdp feldspar, cpx clinopyroxene, gl former glass (composed of zeolite, carbonateand limonite)


the amount of cpx-II, sp-I and pl-II varies from 28 to 78 vol%, from 4 to 47 vol%,and from 7 to 41 vol%, respectively. The amount of altered glass can reach40 vol%.

Geochemistry

Analytical techniques

Phase compositions were determined using a Cameca SX50 electron microprobe atthe Department of Geological Sciences, University of Tennessee, Knoxville. Oper-ating conditions were: accelerating voltage of 15 kV and a filament current of100 mA; beam current was 30 nA for pyroxene, spinel and titanite, and 20 nA foramphibole and plagioclase. The beam size was 5 mm for pyroxene, spinel andtitanite, and 3 mm for amphibole and plagioclase. Counting times were 20 s forall elements. Standard ZAF corrections were applied.

The trace element content of minerals was analyzed by Laser-Ablation Induc-tively Coupled Plasma Mass Spectrometry at the University of Bristol (LA-ICP-MS, VG Elemental Plasma Quad 3). The laser system was used in pulse mode witha frequency of 10 Hz and energy of about 0.1–0.15 mJ=pulse. The laser beam was20 mm wide. The spots for analysis were selected under an optical microscope. TheNIST 610 glass was applied as the external standard and the CaO-content inminerals as the internal standard for yield calculations.

Major element chemistry of minerals

Both groups of clinopyroxenes were analyzed and the average chemical composi-tions of each group are shown in Table 3. Cpx-I is diopside, based on IMA nomen-clature (Morimoto et al., 1988), with 48.6–52.3 wt% SiO2, 2.77–6.68 wt% Al2O3

and 0.46–1.86 wt% TiO2. Its mg-values (Mg=(MgþFetot)) are 0.76–0.78. Cpx-IIis also diopside, but with significantly lower SiO2 content (43.0–43.7 wt%),mg-value (0.73–0.76), higher Al2O3 (11.7–11.9 wt%) and TiO2 contents(2.88–3.69 wt%). Cpx-I has higher proportions of Wo and lower En end memberscompared to those of cpx-II. However, cpx-II shows a wider compositional rangethan cpx-I in Fig. 3. The outer zones of cpx-II are enriched in Al2O3, Na2O, andTiO2 and depleted in MgO.

Clinopyroxenes in granulite xenoliths from the BBH (Embey-Isztin et al., 2003)and Kerguelen Plateau (Gregoire et al., 1998) show compositional similaritiesto cpx-I of the studied xenoliths, whereas clinopyroxenes from granulites ofArkhangelsk differ significantly, particularly, in Na2O (Markwick and Downes,2000). Furthermore, cpx-I is compositionally similar to those in the NG cumulatexenoliths (Kovacs et al., 2004) and corundum-bearing mafic rocks of the HoromanComplex. However, this latter example has clinopyroxenes enriched in MgO(Morishita and Arai, 2001) (Fig. 3).

Both types of amphiboles (amp-I, amp-II) were analyzed by microprobe (Table 3).Amp I is pargasite, whereas amp-II is kaersutite, based on the IMA nomencla-ture (Leake et al., 1997). Amp-I contains 38.9–41.5 wt% SiO2, 2.92–3.70 wt%TiO2, and 11.2–11.9 wt% MgO. Amp II contains 36.4 wt% SiO2, 5.38 wt% TiO2


Tab

le3

.A

vera

ge

majo

rel

emen

tco

mposi

tion

of

min

eral

const

ituen

tsin

the

NG

gra

nuli

texe

noli

ths

(giv

enin

wt%

)

Min

eral

sC

linopyro

xen

eA

mphib

ole

Fel

dsp

arS

pin

elT

itan

ite

Sam

ple

NB

G0

4N

BG

10

NB

G0

4N

BG

10

NB

G0

4N

BG

10

NB

G0

4N

BG

10

NB

G0

4N

BG

10

cpx

-II

cpx

-Icp

x-I

Icp

x-I

amp

-II

amp

-Iam

p-I

pl-

IIp

l-IA

pl-

IBp

l-II

pl-

IAp

l-IB

sp-I

Isp

-Isp

-II

sp-I

Nu

mb

ero

fan

aly

ses:

31

13

23

93

19

52

45

14

76

15

10

81

2

SiO

24

3.7

48

.94

3.0

50

.43

6.4

39

.33

8.9

48

.15

4.1

47

.75

4.3

0.3

70

.03

0.5

40

.03

30

.73

0.5

TiO

22.8

81.3

93.6

90.8

05.3

83.7

02.9

2n.a

.n.a

.n.a

.n.a

.0.5

00.1

90.6

40.2

438.3

37.4

Al 2

O3

11

.76

.14

11

.94

.91

16

.91

5.5

17

.23

2.7

29

.13

3.8

27

.85

7.3

59

.55

8.1

59

.81

.08

1.6

4C

r 2O

30.0

20.0

30.0

30.0

30.0

00.0

10.1

1n.a

.n.a

.n.a

.n.a

.0.1

00.1

50.0

40.0

70.0

50.0

2F

eO*

7.1

46

.28

6.2

66

.90

12

.71

1.6

12

.20

.48

0.0

50

.37

0.8

22

3.0

26

.12

2.8

27

.70

.37

0.4

4M

nO

0.4

70.1

00.1

00.1

40.1

20.1

50.1

7n.a

.n.a

.n.a

.n.a

.0.2

10.3

60.2

00.3

70.0

70.0

2M

gO

10.8

12.7

10.9

12.5

10.5

11.7

11.2

n.a

.n.a

.n.a

.n.a

.14.1

10.4

15.8

11.0

0.0

10.0

4C

aO2

2.0

22

.92

3.0

23

.21

2.0

11

.91

2.0

15

.71

0.9

16

.19

.84

0.2

20

.01

0.3

40

.01

28

.22

8.6

Na 2

O0

.57

0.7

50

.58

0.9

92

.44

2.8

62

.60

2.3

25

.09

2.2

94

.64

n.a

.n

.a.

n.a

.n

.a.

n.a

.n

.a.

K2O

n.a

.n

.a.

n.a

.n

.a.

1.0

80

.93

1.3

10

.20

0.1

70

.17

1.1

9n

.a.

n.a

.n

.a.

n.a

.n

.a.

n.a

.Z

nO

n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.0.2

70.9

30.1

70.9

90.0

60.0

3S

rOn

.a.

n.a

.n

.a.

n.a

.n

.a.

n.a

.n

.a.

0.4

0n

.a.

0.2

10

.26

n.a

.n

.a.

n.a

.n

.a.

n.a

.n

.a.

BaO

n.a

.n

.a.

n.a

.n

.a.

n.a

.n

.a.

n.a

.0

.09

n.a

.0

.03

0.0

4n

.a.

n.a

.n

.a.

n.a

.n

.a.

n.a

.F

n.a

.n.a

.n.a

.n.a

.0.1

20.0

90.2

4n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.C

ln.a

.n.a

.n.a

.n.a

.0.0

40.0

50.0

7n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.n.a

.

To

tal

99

.32

99

.11

99

.52

99

.81

97

.63

97

.69

98

.94

10

0.0

09

9.3

81

00

.71

98

.92

96

.01

97

.65

98

.68

10

0.1

69

8.8

59

8.8

8

� To

tal

iro

nis

exp

ress

edas

FeO

,n

.a.

no

tan

aly

zed

and 10.5 wt% MgO. For comparison, amphiboles in granulite xenoliths fromBakony-Balaton Highland (Embey-Isztin et al., 2003), Kerguelen Plateau (Gregoireet al., 1998), San Francisco Volcanic Field (Chen and Arculus, 1995) andN�oograd-G€oom€oor cumulates (Kovacs et al., 2004) were also tested in diagrams ofLeake et al. (1997) (not shown). These amphiboles have pargasitic compositionsimilar to those of amp-I in the N�oograd-G€oom€oor granulites. Both the KerguelenPlateau and San Francisco Volcanic Field are localities of well-studied lower crust-al, mafic granulite xenoliths containing a wide variety of protoliths; these provide a

Fig. 3. Compositions of clinopyroxenes from the NG granulite xenoliths in Harkervariation diagrams. For comparison, composition of clinopyroxenes from lower crustalgarnet-bearing granulite xenoliths from the Bakony-Balaton Highland (BBH; Embey-Isztinet al., 2003), Kerguelen Plateau (Gregoire et al., 1998), Arkhangelsk (Marckwick andDownes, 2000) as well as corundum-bearing mafic rocks of the Horoman Complex(Morishita and Arai, 2001), and the NG cumulate xenoliths (Kovacs et al., 2004) are alsoshown. Compositions of clinopyroxene phenocrysts (Dobosi and Jenner, 1999; Szab�oo,unpublished) in the host basaltic rocks are also plotted

I. Kovacs and C. Szab�oo: Petrology and geochemistry of granulite xenoliths 277

reliable basis for comparison and help in identifying the protolith of the studiedgranulite xenoliths.

Both pl-IA and pl-IB are andesine (An�36), whereas pl-II is bytownite (An�78)(Table 3). Compositions of feldspars in the NG granulite xenoliths in the Ab-An-Ortriangle are similar to characteristic fields for the San Francisco Volcanic Fieldgranulite and cumulate xenoliths (not shown, Chen and Arculus, 1995). Pl-II dis-plays wider compositional range and contains a higher An-content. Pl-IA and pl-IBfall into the granulite field, whereas pl-II is in the cumulate field of the San FranciscoVolcanic Field granulite xenoliths. Feldspar of the BBH granulite xenoliths(Embey-Isztin et al., 2003) shows similar composition; however most have some-what higher albite content. Xenoliths from Kerguelen Plateau (Gregoire et al., 1998)have feldspars similar to those of the NG granulites. However feldspars from themafic rocks of the Horoman Complex (Morishita and Arai, 2001) are highlyenriched in anorthite component (An90) (Table 3).

Both sp-I and sp-II show compositions between hercynite and spinel end-mem-bers (Table 3). However, systematic differences can be recognized in their compo-sition: sp-I has lower MgO (10.4–11.0 wt%) and higher FeO (26.1–27.7 wt%) andZnO (0.93–0.99 wt%) than sp-II (MgO (14.1–15.8 wt%), FeO (22.8–23.0 wt%)and ZnO (0.17–0.27 wt%)).

Titanite occurs often as tiny crystals (down to 10 mm) within cpx-II. Thesecrystals were only recognized by electron microprobe analysis (Table 3).

Trace element geochemistry of minerals

The average trace element composition of clinopyroxenes is summarized inTable 4. Chondrite-normalized REE patterns reveal that cpx-I in both analyzedgranulite xenoliths shows lower REE values than that of cpx-II. All REE patternsare convex-upward showing slight enrichment in MREE (Fig. 4a). Both types ofclinopyroxene in the NBG10 xenolith (Fig. 4a) have a positive Ce anomaly. Thecpx-II has almost the same pattern as those of the NG cumulate xenoliths (Kovacset al., 2004). Primitive mantle normalized trace element patterns, besides showingthe similar behavior of both types of clinopyroxenes including a remarkable nega-tive Nb anomaly, have distinctive positive U and Pb anomalies, and indicate thepresence of some LIL elements (Rb, Ba and Th) in both types of clinopyroxenesfrom NBG10 (Kovacs et al., 2004) (Fig. 4b).

Average trace element composition of amp-I is shown in Table 4. Because of itssmall size (40–50 mm), amp-II was not measured. Amp-I in the two analyzedgranulite xenoliths displays chondrite-normalized REE pattern similar to those ofthe coexisting clinopyroxenes; it is convex-upward with slight enrichment inMREE, except Gd (Fig. 4c). However, amphiboles in NBG10 have a strong posi-tive Ce anomaly, whereas those in NBG04 are rather enriched in Yb and Lu.Primitive mantle normalized pattern of amp-I in both analyzed granulite xenolithsdisplays a significant positive Pb-anomaly (Fig. 4d). Distribution of the trace ele-ments falls within the field of those amphiboles in the NG cumulate series (Kovacset al., 2004) (Fig. 4d).

Average REE compositions of plagioclases are given in Table 4. There isno significant difference between pl-IB and pl-II, which could be partly due to


the low lateral resolution (20 mm) of the LA-ICP-MS analyses. Most of theMREE and all HREE are below detection limit in pl-II. However, it is clearthat pl-II has elevated contents of LREE and Eu, and is distinctively enrichedin Ce relative to pl-IB. Plagioclases of the cumulate series (Kovacs et al.,2004) are akin to those in the studied xenoliths, except for their enrichmentin Eu.

Table 4. Average trace element composition of mineral constituents in the NG granulitexenoliths (given in ppm)

Sample NBG04 NBG10 NBG04 NBG10 NBG10

cpx-II cpx-I cpx-II cpx-Iamp-I amp-I

pl-II pl-I

Number of analyses

6 7 4 5 2 3 3 2

P 52.4 45.6 551.2 206.6 94.5 211.8 553 407Sc 83.8 48.3 62.8 55.0 41.2 43.1 9.6 3.3Cr 16.8 18.1 129.2 52.2 82.5 154.7 249 104Co 27.5 26.9 28.2 30.4 41.14 54.1 19.2 2.4Ni 31.2 25.3 36.7 28.3 90.75 63.5 n.a. n.a.Rb n.d. n.d. 5.86 2.15 4.03 10.70 11.29 4.83Sr 64.9 48.6 83.7 53.8 228.9 140.1 1867 1084Y 16.9 5.4 24.7 7.7 13.5 16.2 1.5 1.2Zr 50.9 46.5 74.6 70.0 39.3 70.5 23.2 15.6Nb 0.3 0.1 1.2 0.2 8.5 7.9 2.0 0.3Cs n.a. n.a. n.a. n.a. n.d. 0.21 1.90 0.52Ba n.d. n.d. 32.7 9.9 186.5 156.0 216.1 105.3La 1.9 1.2 4.8 2.2 2.5 3.5 4.9 2.4Ce 7.3 3.9 41.4 12.0 8.2 110.8 292.4 76.8Pr 1.6 0.7 2.7 0.9 1.4 1.8 0.7 0.3Nd 9.9 4.1 15.8 5.4 14.3 9.9 3.5 1.2Sm 3.6 1.5 5.6 1.7 3.5 3.3 n.d. 0.5Eu 1.6 0.5 2.4 0.6 1.5 1.3 0.6 0.4Gd 4.8 1.3 5.5 1.6 2.5 3.4 n.d. 0.6Tb 0.8 0.2 0.9 0.3 1.1 0.7 n.d. 0.1Dy 4.5 1.4 5.7 1.6 6.2 3.8 n.d. 0.7Ho 0.9 0.2 1.0 0.3 1.0 0.6 n.d. 0.1Er 1.9 0.6 2.6 0.8 1.7 1.3 n.d. 0.4Tm 0.2 0.1 0.3 0.1 0.2 0.2 n.d. n.d.Yb 1.4 0.7 1.9 0.7 2.6 1.1 n.d. n.d.Lu 0.2 0.1 0.3 0.2 0.4 0.2 n.d. 0.1Hf 2.5 1.9 3.1 2.5 2.7 2.5 n.d. 0.4Ta n.d. n.d. 0.3 n.d. 0.9 0.4 n.d. n.d.Pb 0.9 0.3 5.9 3.8 2.2 3.4 26.4 3.6Th n.d. n.d. 0.4 0.2 0.3 0.4 2.0 0.4U n.d. n.d. 0.2 0.1 n.d. 0.1 0.2 0.1

n.a. not analyzed, n.d. not detected


Discussion

Protolith of the studied xenoliths

Based on modal composition, textural features, and major element geochemistry ofthe early generation of minerals (cpx-I, pl-IA), the studied NG granulite xenolithsresemble those of the other lower crust garnet granulite xenoliths around the world(e.g., Bakony-Balaton Highland, Kerguelen Plateau and San Francisco VolcanicField) (Figs. 3, 4). Generally, it is proposed for protoliths of garnet granulites thatthey have originated from mafic rocks, which were crystallized or emplaced intothe lower crust (Downes, 1993). The two most common ways of emplacing maficbodies into the lower crust are the processes of subduction and underplating(Rudnick, 1992). Underplating is an important way of crustal thickening and isaccompanied by the formation of cumulate bodies at the crust-mantle boundary(Furlong and Fountain, 1986). Granulites originate from cumulate bodies viareheating and subsequent isobaric cooling where only recrystallization of the orig-inal rocks takes place (Bohlen, 1991; Franceschelli et al., 2002). The heat is

Fig. 4. Chondrite (Nakamura, 1974) and primitive mantle normalized (Sun andMcDonough, 1989) rare earth element (a, c) and trace element (b, d) distribution of bothclinopyroxenes and amphiboles, respectively, in the NG granulite xenoliths. For compar-ison, compositions of clinopyroxenes from the NG cumulate xenoliths (Kovacs et al., 2004)are also shown


commonly derived from episodic magmatic influxes at the crust-mantle boundary(Bohlen, 1991). If this is the case beneath the NG at the time of underplating thenthe primary igneous minerals should preserve their pristine geochemical nature.However, in case of significant chemical deviation between granulites and commonlower crustal igneous mafic rocks (cumulates) we should assume that the systemcould have been open. It indicates infiltration of fluids=melts or extraction of meltsduring the metamorphic evolution of granulites.

In order to reveal the nature of the probable protoliths, we compare the geo-chemical features of the NG granulite to the NG cumulate series formed by under-plating. Taking into consideration the La=Lu ratio against mg# of clinopyroxenes(not shown), the majority of the cpx-I in the NG granulite series has basically thesame mg-values, however considerably lower (from 1=3 to 1=2) La=Lu ratios thanthose of the cumulate series. This suggests a less depleted and may be more prim-itive nature of the cumulates. It could also imply that melt extraction happenedduring the metamorphic evolution of granulites, which is responsible for theirlower La=Lu ratios. This is in agreement with the presence of former volcanicglass that has already been decomposed to secondary minerals. However, basedon the modal proportion of these secondary minerals, which roughly correspondsto that of the former glass, the degree of partial melting may have been small(0.4%). Thus, small degree of partial melting can account for the unchangedmg-values comparing to igneous cumulates. Presumably, only considerably higherdegrees of melting could result in higher mg-values of the residual granulite.To conclude, assuming that the principal geochemical features of early minerals(cpx-I, pl-IA) were inherited during metamorphism as Franceschelli et al. (2002)and Yu et al. (2003) pointed out, the protolith of the NG granulites could have beenmafic rocks chemically similar to NG cumulates (Figs. 3, 4). Similarly, Gregoireet al. (1998) and Sachs and Hansteen (2000) imply that the mafic granulites ofthe Eifel Volcanic Field and the Kerguelen Plateau are the product of magmaticunderplating.

However, it is still ambiguous whether the bodies of the suspected mafic pro-tolith were the result of igneous underplating or were dragged down to the depth ofthe lower crust by subduction. Embey-Isztin et al. (2003) proposed that the sourceof the Bakony-Balaton Highland granulites beneath the central Pannonian Basincould be the remnants of a subducted oceanic slab, which suffered high-grademetamorphism probably during the Alpine orogeny. The NG granulite xenolithsalso show several geochemical features in common with the Bakony-Balaton High-land granulite xenoliths (Fig. 3).

Metasomatism

Both fabrics (Fig. 2b) and geochemical features (Fig. 4) of amp-I in the granulitexenoliths resemble those of the cumulate xenoliths and Type-I xenoliths of the NG.Amp-I in granulites even occurs as patches and tiny lamellae in clinopyroxenes(Fig. 2b), which is a clear evidence for transformation of clinopyroxene to amphi-bole driven by metasomatic alteration. Amp-I in the NG granulite xenoliths dis-plays positive Ba, Nb, Ce and Pb and negative Th and Zr anomalies. Apart from Ceand Pb, this is in good agreement with those values of the NG cumulate series


(Kovacs et al., 2004). The positive Pb anomaly could be the result of crustalcontamination. The anomaly was inherited from cpx-I, which also exhibits a con-siderable positive Pb anomaly. Thus, we infer a metasomatic origin for amphibolesimilar to that of cumulate and Type-I xenoliths proposed by Szab�oo and Taylor(1994) and Kovacs et al. (2004), respectively. For this reason, the positive Pbanomaly is attributed to the original composition of the granulites (i.e. protolith),rather than to the variation in composition of the metasomatic agent. Kovacs et al.(2004) pointed out that the slab-derived melts and fluids played an important rolein the refertilization of the lithospheric mantle. Szab�oo et al. (1996) also cameto a similar conclusion from studies of silicate melt inclusions and melt pocketsin the NG Type-I xenoliths. It is a plausible assumption that the same metasomaticalteration also affected the lower crust. The composition and large-scale formationof amphiboles is strong evidence for pervasive metasomatism in the mantle wedgeassociated with Miocene subduction beneath the outer Carpathian arc (Szab�oo et al.,1992; Kovacs et al., 2004).

Composition of the symplectites

One of the principal goals of this paper is to describe the process that formed thesymplectites. Spherical shape and systematic textural setting of minerals (Fig. 2c)in the symplectites suggest that they formed by breakdown and subsequent meltingof a former mineral, which was in equilibrium with cpx-I and pl-IA. According tothe available data, similar symplectites usually originate from either the breakdownreaction of garnet (in garnet clinopyroxenites) (T€oor€ook, 1995; Sachs and Hansteen,2000; D�eegi and T€oor€ook, 2004) or corundum (in veined peridotite) (Morishita andArai, 2001).

Bulk chemical composition of the studied symplectites cannot be preciselydetermined because there is no preserved volcanic glass (its vol% is 12–48 vol%,Table 2), which brings a large uncertainty in our approximation. Also, it is not clearif the system was closed during melting. We can assess the decomposed mineral bycomparing the composition of the present mineral constituents (mostly sp-I, pl-IB,cpx-II) to those in similar textural and petrologic setting. However, some of theseminerals (cpx-II and partially pl-IB) are recrystallized from the melt of thesymplectites, therefore these are not perfectly identical to the former symplectitepyroxenes (virtual opx�, cpx�, Fig. 5). Mineral assemblages after garnet break-down in granulite xenoliths were previously studied by T€oor€ook (1995) and D�eegi andT€oor€ook (2004) in the BBH, and by Sachs and Hansteen (2000) in the Eifel VolcanicField (EVF). T€oor€ook (1995) and D�eegi and T€oor€ook (2004) carried out a detailed studyon symplectite formed after garnet in granulites of the BBH and pointed out thatthe symplectite is composed of fine-grained Al-rich orthopyroxene, spinel andanorthite. However, both chemical composition and size of the symplectite miner-als (�10 mm) are slightly different from those of the studied NG ones. Spinels insymplectites of the BBH have higher MgO content (20.0 wt%) and plagioclasereflects elevated CaO content (approx. 18 wt%), and orthopyroxene is frequent.

Sachs and Hansteen (2000) found spinel-feldspar-clinopyroxene and spinel-clinopyroxene assemblages in clinopyroxenite xenoliths from alkaline basalts ofthe EVF similar to the NG symplectites (Sachs and Hansteen (2000) used the term


clinopyroxenites for xenoliths studied, which could also be called granulites basedon the characteristic textures and mineral assemblages (http:==www.bgs.ac.uk=SCMR=)). The differences are the followings: the Eifel symplectites were not affectedby melting and sometimes contain orthopyroxene. Chemical composition of mineralconstituents of the symplectites agrees well with the studied NG ones. Spinelcontains 57.6 wt% Al2O3, 27.7 wt% FeO and 12.5 wt% MgO, which is quite similarto the sp-I in the NG granulite xenoliths (Table 3). Plagioclase is also similar tothose in NG granulites (pl-IB) by having 34.1 wt% of Al2O3 and 17.5 wt% of FeOcontent (Table 3). Sachs and Hansteen (2000) pointed out that spinel-feldspar-clinopyroxene and spinel-clinopyroxene assemblages in the Eifel clinopyroxenitexenoliths originated from garnet or garnetþ clinopyroxene, according to the fol-lowing reactions under lower crustal conditions:

garnet þ clinopyroxene 1 ¼ clinopyroxene 2 þ hercynite þ plagioclase ð1Þ

garnet ¼ orthopyroxene þ hercynite þ plagioclase ð2Þ

Fig. 5. Schematic evolution of the symplectites in the NG granulites (see text for details)


We believe that symplectites in the NG granulites could have also been formed byeither reaction (Fig. 5). The remaining differences in mineralogy and mineralchemistry, among the studied and other symplectites in similar granulite xenoliths(see above), can be explained by subsequent melting, which may be responsible forthe lack of the former orthopyroxene (opx�; hypothetical orthopyroxene). Exten-sive melting (discussed in detail below) consumed this mineral (on a lesser extentalso the cpx�, hypothetical clinopyroxene), thus, they cannot be traced in thepresent assemblages of symplectites (Fig. 5). Lack of the hypothetical opx� isfurther supported by Faure et al. (2001) who proposed that melting in an Al-richenvironment under lower crustal P-T conditions triggers transformation of ortho-pyroxene to clinopyroxenes due to incorporation of Al into the orthopyroxenestructure.

Melting process

The NG granulite xenoliths display evidence of melting and subsequent recrystal-lization of minerals (Fig. 2a–e). We assume that the host basalt or any other relatedmelt could provide enough heat to cause partial melting in the granulite, thereforean assessment of the potential effect of the host basalt on the chemistry of theresulting melt is necessary. The amount of melt in the spinel-feldspar-clinopyrox-ene symplectites is significant, reaching up to 40 vol% (Table 2, Fig. 2c). Based onpetrographic evidence, sp-I in the center of the symplectites has a resorbed, irreg-ular boundary (Fig. 2c) indicating that melting affected the sp-I. Pl-II near sp-Ishows several worm-like silicate-melt inclusions as clear evidence for melting,which mostly affected the edge of pl-IB in the symplectites (Fig. 2c, e). Pl-II isenriched in anorthite, indicating that the pl-II resulted from melt extraction frompl-IB (Fig. 4). Thus, it can be excluded that host basalt affected the composition ofthe newly formed plagioclase (pl-II) during melting, because if this were the case,we should see enrichment in Na due to the alkaline character of the host basalt.

Cpx-II is euhedral, has rhomboidal transect and contains octahedral sp-II inclu-sions (Fig. 2c, d). All these features support that cpx-II and sp-II crystallizeddirectly from the melt, which was formed from pl-IB, sp-I and probably from cpx�and opx� as explained in the previous section (Fig. 5). Cpx-II is zoned, and enrich-ment of Ti, Fe, Al and depletion of Mg can be seen towards the rim (Fig. 3).Furthermore, the compositional trend connecting the fields of cpx-I and cpx-IIpoints in a direction distinct from the fields of phenocrysts in the host basalt.Therefore, a chemical effect of the host basalt can be also excluded (Fig. 3).Gradual enrichment of incompatible major elements towards the edges in cpx-II(Fig. 3) also indicates continuous crystallization from melt. This trend would notbe present if the basaltic host could have buffered the composition of the melt (i.e.both infiltration of the host basalt and chemical diffusion from the basalt areinsignificant).

Newly crystallized amp-II can also be observed as an overgrowth on olderamphiboles (amp-I) and clinopyroxenes (cpx-I) (Fig. 2b). Amp-II shows chemicalvariations toward the rim with increasing contents of Al2O3, TiO2 and FeOsupporting crystallization of amp-II directly from the melt in the symplectites(Table 3).


To conclude, the melting event particularly affected the spinel-plagioclase-clinopyroxene symplectites, which resulted mostly in melting of pl-IB, sp-I, thesuspected opx� or=and cpx�, and the subsequent crystallization of gl-I (i.e. themelt) that resulted in formation of sp-II, cpx-II, amp-II and gl-II, respectively(Fig. 5). Differences in composition of these late minerals and those in the ground-mass of the host basalt indicate that the host basalt did not influence chemically themelting and crystallization process (Fig. 3). We propose that melting was an in situprocess. This is verified by the fact that the host basalt chemically had no effect onthe melt composition in the symplectites and the cpx-I is relatively depleted inincompatible trace elements (Fig. 4, Table 3). Geobarometric calculations andpreservation of concentric symplectites confirm that melting could have happenedat greater depth (6–7 kbar, see details in the next section).

Metamorphic evolution of granulite xenoliths

To better understand the processes that have occurred in the lower crust beneath theNG, equilibrium temperature and pressure have been estimated using mineralequilibria and geothermobarometry. Assuming that garnet (i.e. former mineral ofthe symplecites) was present in the studied granulite xenoliths at peak meta-morphic conditions, the P-T conditions can be assessed. Minimum equilibriumtemperature is in the range of 900–1030 �C, based on the equilibrium mineralassemblages in granulites (spinelþ clinopyroxeneþ pargasiteþ plagioclaseþmelt)after Springer (1992). Taking this temperature range, the NG granulite xenoliths,containing garnet, cpx-I and pl-IA, had experienced at least 1.1 GPa pressure (cor-responding to a minimum depth of 30 km) because this is the lower limit wheregarnet crystallizes in mafic rocks during granulite facies metamorphism (Gregoireet al., 1998) (Fig. 6).

The geobarometer of Nimis (1995) is suitable for igneous clinopyroxenes,hence we used it to estimate the formation pressure of the cpx-II formedfrom melt as discussed above. The calculation provides a pressure of 0.6–0.7(�0.2) GPa, which corresponds to 16–19 (�5.4) km depth, assuming that the lowercrust has an average density of 2.7 kg=m3 beneath the NG. This depth roughlycoincides with the present crust-mantle boundary (25–30 km) based on geophysi-cal data (Posgay et al., 1991; Horvath, 1993; Lenkey, 1999).

The difference between the two stages of granulite metamorphism is at0.4–0.5 (�0.2) GPa. This is a minimum estimate that corresponds to thinningof the crust by 10.8–13.5 km during its ‘‘exhumation’’ path. The degree of thin-ning is in agreement with Huismans et al. (2001) who proposed thinning factor(�¼ 1.4–1.6) of crustal extension for the first stage (18–16 Ma) of the Miocenerifting in the Pannonian Basin. This corresponds to 40 km thick crust before thefirst thinning event, if we assume 27 km as an average thickness for the presentcrust (Fig. 6). It is believed that the protolith of the NG granulite xenoliths wentthrough metamorphism at pressures equivalent to the ‘original’ thickness of thecrust, whereas events of melting and recrystallization of minerals in thesymplectites happened closer to the present depth of the MOHO. The garnetbreakdown process could have taken place between these two stages. Evidenceof the thinning event was also reported by T€oor€ook (1995) and D�eegi and T€oor€ook


(2004) from the BBH granulite xenoliths in the central Pannonian Basin, wherethinning on the order of 7–15 km was proposed based on fluid inclusion measure-ments, mineral equilibria and geothermobarometry. Characteristic temperaturefor the lower crust at the time of basaltic volcanism is also taken from their work,as in the N�oograd-G€oom€oor Volcanic Field an adequate method for putting con-straints on the temperature conditions of granulites (i.e. fluid inclusion measure-ments) has not yet been applied.

It is a widespread idea that lower crustal mafic rocks (i.e. granulites, amphib-olites, eclogites) could play a significant role in the petrogenesis of intermediateto acidic rocks (Rudnick, 1992; Downes, 1993; Harangi et al., 2001; Harangi,2001). However, xenoliths representing this source material have not yet beenfound in the Carpathian-Pannonian Region. We suppose, based on the evidencefor melting, that the NG granulite xenoliths might represent a potential source ofthe Tertiary calc-alkaline magmas in the NG. Also, Harangi (2001) assumed that

Fig. 6. P-T path (arrow) of the NG granulite xenoliths. Evolution of xenoliths, stabilityfield of garnet-free and garnet-bearing granulites are also indicated (opx orthopyroxene,cpx clinopyroxene, sp spinel, pl plagioclase, sapph sapphirine, ol olivine, co corundum,di diopside). 1, Uncertain granulite-facies metamorphism of the proposed mafic protolith.2, Peak-metamorphism of the rocks studied, with garnet formation during granulite faciesmetamorphism. 3, Exhumation stage: break-down of garnet and formation of the spinel-feldspar-clinopyroxene symplectite and its melting, due to both significant decreasein pressure and increase in temperature probably caused by the first phase of rifting(16–18 Ma ago) in the Pannonian Basin. 4, Equilibrium conditions reached correspondingto the present depth of the MOHO beneath the NG (Posgay et al., 1991; Horvath, 1993)


metasomatized lower crustal rocks could play an important role at the onset ofTertiary calc-alkaline volcanism in the Carpathian-Pannonian Region.

Conclusion

Mafic granulite xenoliths of the N�oograd-G€oom€oor are plagioclase-bearing hornblendeclinopyroxenites, plagioclase-bearing clinopyroxene hornblendites, and plagioclase-bearing clinopyroxenites. Unusual symplectites were recognized in the xenoliths,which are composed of spinel, feldspar and clinopyroxene. They are interpretedas the product of garnet breakdown.

The N�oograd-G€oom€oor granulite xenoliths display evidences of melting and sub-sequent recrystallization, mostly in the symplectites. The amount of melt in thespinel-feldspar-clinopyroxene symplectites is significant, reaching upto 40 vol%locally. We propose that melting was an in situ process. This is also suggested bythe fact that the host basalt did not have any chemical effect on the melt composi-tion in the symplectites. We suppose, based on the evidences of melting, that lowercrustal rocks similar to the N�oograd-G€oom€oor granulite xenoliths might have been apotential source of the Tertiary calc-alkaline magmas in the studied area.

We suggest that the protolith of the N�oograd-G€oom€oor granulite xenoliths weremetamorphosed at pressures equivalent to the ‘original’ Pre-Miocene thickness ofthe crust (>30 km). However, it is still ambiguous whether the bodies of the sus-pected mafic protolith were the result of igneous underplating or were draggeddown to the depth of the lower crust by subduction. Events of melting and recrys-tallization of minerals in the symplectites happened close to the present depth ofthe MOHO (19–16 km).

Acknowledgements

The authors express their thanks to L. Taylor (University of Tennessee, Knoxville),B. Paterson (University of Bristol), for major and trace elements analysis, respectively.The authors are also grateful to K. T€oor€ook, Z. Zajacz and Gy. Falus (Lithosphere FluidResearch Lab, E€ootv€oos University) and T. M. T�ooth (University of Szeged) for their helpfuldiscussions. M. Janosi is acknowledged for her help in sample collection. J. Foden, H. S€oolva,H. Downes, M. Elburg are greatly acknowledged for highly improving the earlier version ofthe manuscript. We appreciate the useful editorial assistance of K. St€uuwe. Pro RenovandaCultura Hungariae foundation is thanked for financial support to IK. We acknowledge thesupport of the European Community Access to Research Infrastructure action of the Improv-ing Human Potential Programme, contract HPRI-CT-1999-00008 awarded to B. J. Wood (EUGeochemical Facility, University of Bristol). This is the 18th publication of the LithosphereFluid Research Lab of the Department of Petrology and Geochemistry at E€ootv€oos University,Budapest.

References

Bali E, Szab�oo C, Vaselli O, T€oor€ook K (2002) Significance of silicate melt pockets in uppermantle xenoliths from the Bakony-Balaton Highland Volcanic Field, Western Hungary.Lithos 61: 79–102

Bohlen SR (1991) On the formation of granulites. J Metamorph Geol 9: 223–229


Chen W, Arculus RJ (1995) Geochemical and isotopic characteristic of lower crustal xeno-liths, San Francisco Volcanic Field, Arizona, U.S.A. Lithos 36: 203–225

D�eegi J, T€oor€ook K (2004) Petrographic evidence of crustal thinning in Bakony-Balaton High-land Volcanic Field. Magyar Geofizika 44: 125–133 (in Hungarian with English abstract)

Dobosi G, Jenner GA (1999) Petrologic implications of trace element variation in clinopy-roxene megacrysts from the N�oograd volcanic province, north Hungary: a study by laserablation microprobe-inductively coupled plasma-mass spectrometry. Lithos 46: 731–749

Dobosi G, Downes H, Embey-Isztin A, Jenner GA (2003) Origin of megacrysts and py-roxenite xenoliths from the Pliocene alkali basalts of the Pannonian Basin (Hungary).N Jb Mineral Abh 178=3: 217–237

Downes H (1993) The nature of the lower continental crust of Europe: petrological andgeochemical evidence from xenoliths. Phys Earth Planet Interiors 79: 195–218

Downes H (2001) Formation and modification of the shallow sub-continental lithosphericmantle: evidence from ultramafic xenoliths suites and massifs of western and centralEurope. J Petrol 42: 233–250

Downes H, Embey-Isztin A, Thirlwall MF (1992) Petrology and geochemistry of spinelperidotite xenoliths from the western Pannonian Basin (Hungary): evidence for anassociation between enrichment and texture in the upper mantle. Contrib Mineral Petrol109: 340–354

Embey-Isztin A, Scharbert HG, Dietrich H, Poultidis H (1989) Petrology and geochemistryof peridotite xenoliths in alkali basalts from the Transdanubian Volcanic Region, WestHungary. J Petrol 30: 79–105

Embey-Isztin A, Downes H, James DE, Upton BG, Dobosi G, Ingram GA, Harmon RS,Schrabert HG (1993) The petrogenesis of Pliocene alkaline volcanic rocks from thePannonian Basin. J Petrol 34: 317–343

Embey-Isztin A, Dobosi G, Altherr R, Meyer HP (2001) Thermal evolution of the lithospherebeneath the western Pannonian Basin: evidence from deep-seated xenoliths. Tectono-physics 331: 285–306

Embey-Isztin A, Downes H, Kempton PD, Dobosi G, Thirwall M (2003) Lower crustalgranulite xenoliths from the Pannonian Basin, Hungary, part 1. Mineral chemistry,thermobarometry and petrology. Contrib Mineral Petrol 144: 652–670

Faure F, Trolliard G, Montel J-M, Nicollet C (2001) Nano-petrographic investigation of amafic xenolith (Maar de Beaunit, Massif Central, France). Eur J Mineral 13: 27–40

Franceschelli M, Carcangiu G, Caredda AM, Cruciani G, Memmi I, Zucca M (2002)Transformation of cumulate mafic rocks to granulite and re-equilibration in amphiboliteand greenschist facies in NE Sardinia, Italy. Lithos 63: 1–18

Frey FA, Prinz M (1978) Ultramafic inclusions from San Carlos, Arizona: petrologic andgeochemical data bearing on their petrogenesis. Earth Planet Sci Lett 38: 129–176

Furlong KP, Fountain DM (1986) Continental crustal underplating: thermal considerationsand seismic-petrologic consequences. J Geophys Res 91: 8285–8294

Garvie OC, Robinson DN (1984) The formation of kelyphite and associated sub-kelyphiticsculptured surface on pyrope from kimberlite. In: Kornprobst I (ed) Kimberlites I:kimberlites and related rocks. Elsevier, Amsterdam, pp 371–382

Gregoire M, Cottin JY, Giret A, Mattielli N, Weis D (1998) The meta-igneous granulitexenoliths from Kerguelen Archipelago: evidence of a continent nucleation in an oceanicsetting. Contrib Mineral Petrol 133: 259–283

Griffin WL, O’Reilly SY (1987) Is the continental Moho the crust=mantle boundary? Geology15: 241–244

Harangi S (2001) Neogene to Quaternary volcanism of the Carpathian-Pannonian region areview. Acta Geol Hung 44: 223–258


Harangi S, Downes H, K�oosa L, Szab�oo C, Thirlwall MF, Mason PRD, Mattey D (2001)Almandine garnet in calc-alkaline volcanic rocks of the Northern Pannonian Basin(Eastern-Central Europe): geochemistry, petrogenesis and geodynamic implications.J Petrol 42: 1813–1843

Horvath F (1993) Towards a mechanical model for the formation of the Pannonian basin.Tectonophysics 226: 333–357

Huismans RS, Podladchikov YY, Cloetingh S (2001) Transition from passive to active rifting:relative importance of asthenospheric doming and passive extension of the lithosphere.J Geophys Res 106: 11271–11291

Huraiova M, Konecny P (1994) Pressure-temperature conditions and oxidation state of theupper mantle in southern Slovakia. Acta Geol Hung 37: 29–39

Hurai V, Simon K, Wiechert U, Hoefs J, Konecny P, Huraiova M, Pironon J, Lipka J (1998)Immiscible separation of metalliferous Fe=Ti-oxide melts from fractionating alkalibasalt: P-T-fO2 conditions and two-liquid elemental partitioning. Contrib Mineral Petrol133: 12–29

Koroknai B, Horvath P, Balogh K, Dunkl I (2001) Alpine metamorphic evolution and coolinghistory of the Veporic basement in northern Hungary: new petrological and geochro-nological constraints. Int J Earth Sci 90: 740–751

Kovacs I, Zajacz Z, Szab�oo C (2004) Type-II xenoliths and related metasomatism from theN�oograd-G€oom€oor Volcanic Field, Carpathian-Pannonian Region (northern Hungary –southern Slovakia). Tectonophysics 393: 139–161

Kurat G, Embey-Isztin A, Kracher A, Scharbert HG (1991) The upper mantle beneathKapfenstein and the Transdanubian Volcanic Region, E-Austria and W-Hungary: acomparison. Mineral Petrol 44: 21–38

Leake BE, Woolley ER, Arps CE, Birch WD, Gilbert MC, Grice JD, Hawthorne FC, Kato A,Kisch HJ, Krivovichev VG, Linthout K, Laird J, Mandarino JA, Maresch WV, Nickel EH,Rock NMS, Schumacher JC, Smith DC, Stephenson NCN, Ungaretti L, Whittaker EJW,Guo YZ (1997) Nomenclature of amphiboles: report of the subcommittee on amphibolesof the International Mineralogical Association, commission on new minerals and mineralnames. Am Mineral 82: 1019–1037

Lenkey L (1999) Geothermics of the Pannonian Basin and its bearing on the tectonics ofbasin evolution. Thesis, Vrije Universiteit, pp 215

Markwick AJW, Downes H (2000) Lower crustal granulite xenoliths from the Arkhangelskkimberlite pipes: petrological, geochemical and geophysical results. Lithos 51:135–151

Morimoto N, Fabries J, Ferguson A, Ginzburg IV, Ross M, Seifert FA, Zussman J, Aoki K,Gottardi G (1988) Nomenclature of pyroxenes. Am Mineral 73: 1123–1133

Morishita T, Arai S (2001) Petrogenesis of corundum-bearing mafic rock in the Horomanperidotite complex, Japan. J Petrol 42: 1279–1299

Nakamura N (1974) Determination of REE, Ba, Fe, Mg, Na, and K in carbonaceous andordinary chondrites. Geochim Cosmochim Acta 38: 757–776

Nimis P (1995) A clinopyroxene geobarometer for basaltic systems based on crystal-struc-ture modeling. Contrib Mineral Petrol 121: 115–125

Nixon PH (1987) Mantle xenoliths. Wiley & Sons, New York, pp 589Padovani ER, Carter JL (1977) Non-equilibrium partial fusion due to decompression and

thermal effects in crustal xenolith. In: Dick HJB (ed) Magma genesis. Oreg Dept GeolMineral Ind Bull Portland, Oregon, pp 43–57

Posgay K, Albu I, Mayerova M, Nakladalova Z, Ibrmajer I, Blizkovski M, Aric K, GutdeutschR (1991) Contour map of the Mohorovicic discontinuity beneath Central Europe.Geophys Transact 36: 7–13


Rudnick RL (1992) Xenoliths – samples of the lower continental crust. In: Fountain D et al.(eds) Continental lower crust. Elsevier, Amsterdam, pp 269–316

Sachs PM, Hansteen HT (2000) Pleistocene underplating and metasomatism of the lowercontinental crust: a xenolith study. J Petrol 41: 331–356

Springer W (1992) Entstehung granitoider Magmen durch partielle Aufschmelzungbasischer Unterkruste: eine experimentelle Studie. Thesis, Universit€aat K€ooln, pp 116

Szab�oo C, Harangi S, Csontos L (1992) Review of Neogene and Quaternary volcanism of theCarpathian-Pannonian region. Tectonophysics 208: 243–256

Szab�oo C, Taylor LA (1994) Mantle petrology and geochemistry beneath the N�oograd-G€oom€oorVolcanic Field, Carpathian-Pannonian Region. Int Geol Rev 36: 328–358

Szab�oo C, Harangi S, Vaselli O, Downes H (1995) Ultramafic xenoliths from the LittleHungarian Plain, Western Hungary: a petrologic and geochemical study. Acta Volcanol7: 241–239

Szab�oo C, Bodnar RJ, Sobolev AV (1996) Metasomatism associated with subduction related,volatile-rich, silicate melt in the upper mantle beneath the N�oograd-G€oom€oor volcanic Field,Northern Hungary=Southern Slovakia: evidence from silicate melt inclusions. Eur JMineral 8: 881–899

Szab�oo C, Falus G, Zajacz Z, Kovacs I, Bali E (2004) Composition and evolution oflithosphere beneath the Carpathian-Pannonian region: a review. Tectonophysics 393:119–137

Sun S, McDonough WF (1989) Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes. In: Saunders AD, Norry MJ (eds)Magmatism in the ocean basins. Geol Soc Lond Spec Publ 42: 313–345

T€oor€ook K (1995) Garnet breakdown reaction and fluid inclusions in a garnet-clinopyroxenitexenolith from Szentb�eekkalla (Balaton-Highland, Western Hungary). Acta Vulcanol 7:285–290

Vaselli O, Downes H, Thirlwall M, Dobosi G, Coradossi N, Seghedi I, Szakacs A, Vannucci R(1995) Ultramafic xenoliths in Plio-Pleistocene alkali basalts from the EasternTransylvanian Basin: depleted mantle enriched by vein metasomatism. J Petrol 36:23–53

Vaselli O, Downes H, Thirlwall MF, Vannucci R, Coradossi N (1996) Spinel-peridotitexenoliths from Kapfenstein, (Graz Basin, Eastern Austria): a geochemical and petrolog-ical study. Mineral Petrol 57: 23–50

Yu J, Xu X, Zhou X (2003) Late Mesozoic crust-mantle interaction and lower crust compo-nents in South China: a geochemical study of mafic granulite xenoliths from Cenozoicbasalts. Science in China Series D 46=5: 447–460

Authors’ address: I. Kovacs (e-mail: [email protected]) and Cs. Szab�oo (e-mail:[email protected]), Department of Petrology and Geochemistry, Lithosphere FluidResearch Lab, E€ootv€oos University, Pazmany P�eeter s�eetany 1=C, Budapest, H-1117, Hungary

290 I. Kovacs and C. Szab�oo: Petrology and geochemistry of granulite xenoliths

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