CONTACT METAMORPHISM OF THE LUCERNE PLUTON HANCOCK CO. , MAINE

by

Steven W. Novak

Thesis submitted to the Graduate Faculty of the

Virginia Polytechnic Institute and State University

in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

in

Geological Sciences

APPROVED:

D. R. Wones, Chairman

M. C. Gilbert D. A. Hewitt

March~ 1979

Blacksburg, Virginia

ACKNOWLEDGMENTS

It is an honor to acknowledge the help and support of my

advisor, David R. Wones, whose detailed mapping of this area

formed the basis of this study. Critical reviews by my advisory

committee, D. A. Hewitt and M. C. Gilbert, have also greatly

improved the manuscript. Fellow students and

provided help with a critical review and many

informal discussions. Thanks to

on the microprobe and especially to

and

for instruction

for drafting

for photo-figures. The help of

graphy and for typing is also appreciated. Last

but not least, I thank my wife

standing during this study.

for her support and under-

Financial support was provided by a grant from the research

divisi.on of VPI & SU and N.S.F. Grant EAR 78-03655 to David R.

Wanes.

i

TABLE OF CONTENTS

INTRODUCTION AND PURPOSE OF STUDY.

GEOLOGIC SETTING • • • • • • • • •

PETROGRAPHY OF LOW GRADE BUCKSPORT FORMATION

MINERAL CHANGES IN THE BUCKSPORT FORMATION •

MINERAL CHANGES IN THE PENOBSCOT FORMATION •

MINERAL CHEMISTRY. • • • • • • • • • • •

INTENSIVE VARIABLES DURING METAMORPHISM.

Pressure During Metamorphism. • •

Temperatures During Metamorphism.

FLUID COMPOSITIONS DURING METAMORPHISM

MINERAL ZONING IN THE BUCKSPORT FORMATION ••

CONCLUSIONS. •

REFERENCES .

APPENDIX I .

APPENDIX II.

APPENDIX.III .

VITA ••••

Page

1

2

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23

31

35

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• • • • • 56

56

65

• • • • 6 7

• • • • •· 74

• • • • 79

81

86

91

92

• 109

INTRODUCTION AND PURPOSE OF STUDY

The Lucerne pluton is a coarse, seriate biotite.-bearing p1uton

located in Hancock County, Maine. It intrudes several structurally

distinct, fault-bounded blocks containing lower paleozoic metamorphic

rocks. The pluton is located on the northeast limit of regional

biotite grade metamorphism in Maine and probably represents a

transitional area between the deeper erosional levels of central

Maine and the shallower low grade,terranes of northeastern Maine (Doyle

and Hussey, 1967; Thompson and Norton, 1968). This study char-

acterizes the mineral assemblages of the Silurian-Devonian?

Bucksport formation and the Ordovician-Silurian? Penobscot formation

within the Lucerne's contact aureole in order to determine the

conditions of emplacement of the pluton. The Bucksport formation,

which is thought by Wbnes (1976) to be equivalent to the Vassalboro

formation is a calcareous turbidite. The study area is similar to that

investigated by Ferry (1976a,b) of the metamorphic aureole in the

Vassalboro formation in contact with the Togus plutons. However, the

area of the Lucerne pluton is not affected by the higher grade regional

metamorphism of central Maine, nor is late stage hydrothermal alteration

and important aspect of the Lucerne pluton. Petrographic observations

combined with microprobe analyses of minerals from the contact aureole

allow an estimate of pressure during intrusion and a temperature gradient

within the aureole. This information provides an initial estimate of

the evolution of H2o-co2 fluids in the Bucksport formation and H2o rich

fluids in the Penobscot formation during contact metamorphism.

1

GEOLOGIC SETTING

Recent ideas on the geologic evolution of central and eastern

Maine are given by Osberg (1974) and Pankiwskyj and others (1976).

Stewart and Wanes (1976) review the geology of the Penobscot bay

area that includes the Lucerne pluton. The study area (fig. 1)

includes the Coastal Volcanic Belt of eastern Maine and the south-

east limb of the Marrimack synclinorium (Pankiwskyj and others, 1976).

The Lucerne intrudes three and possibly four structural blocks,

each with its own stratigraphic section (fig. 1). From north to

south respectively, these are: the Waterville-Vassalboro block,

the Passagassawakeag-Bucksport block, the Penobscot block, and.

the Castine-Ellsworth or Coastal Volcanic block. Each block is

separated from adjacent blocks by faults or unconf ormities and each

has its own characteristic sequence of formations (Wones, 1976).

1he Waterville-Vassalboro block lies north of the Lucerne and contains

the area of Buchan metamorphism studied by Osberg (1968, 1971, 1974)

and Ferry (1976a,b, 1978). Chlorite grade Vassalboro formation

found in this block is separated from biotite grade Vassalboro of

the adjacent Passagassawakeag-Bucksport block by the Norumbega fault.

This major strike-slip fault may extend to New Brunswick and truncates

the north end of the Lucerne pluton (Wones and Stewart, 1976).

If Wanes (1976) is correct, the Waterville-Vassalboro and Passagassa-

wakeag-Bucksport blocks are equivalent so the Norumbega fault is

confined within one large structural block. Since the Noru.mbega fault

cuts the Lucerne, the pluton probably intruded both the Waterville-

Vassalboro and Passagassawakeag blocks, however, the Lucerne has not

2

3

Figure 1. Geologic map of the Lucerne pluton and surroundings. Sampling of the aureole was from the Vassalboro (Bucksport) and Penobscot formations.

N

M\20t ~ 6i:l'35 '

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44°55' -

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68°30 '

45•0 0 ·- I 68'20'

I

\ GEOLOGY OF

THE LUCERNE PLUTON HANCOCK COUNTY, MAINE

DAVID R. WONE S 1979

)~ CONGLOMERATE S , Pt) $ T M IO - u E. 110NIAN

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D WALLAMATOGUS PL U T(J N

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D BLU E HILL PLUTON

~ SOUTH PENOBSCO T PLUTON

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D VASSALBORO t B u ci-: s Po RT l r o RMAT 10 N

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~ COPELA ND FORMATI ON , ~ RIDER B L UFF MEMBER

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IO M.les ~ PAS SAGASSAWAKEA G GNE I SS, 1--~-1.~~_...~~-"-~~.._~_. ~ MIXER PONC MEMBE R

~ PA SSAGA SSA WA KEA G GNE I SS

5

Figure la. Locations of samples of the Bucksport formation from the Orono quadrangle. All samples preceded by prefix OND.

6

7

\

Figure lb. Locations of samples of the Bucksport formation from the northwest.corner of the Orland quadrangle. All samples preceded by the prefix ORB. Samples 101-1 through 101-13 collected by D. R. Wones, all others collected by S. Novak.

8

9

Figure le. Locations of samples of the Bucksport formation from the southwest corner of the Orland quadrangle. All sample numbers preceded by the prefix ORC.

10

11

Figure ld. Locations of samples of the Penobscot formation from the Ellsworth quadrangle. All sample numbers have the prefix ELA. Sample ELA 13b is 5 km north of Greenwood cemetery along Route 180.

12

13

been identified north of the fault. South of the Norumbega fa.ult is

the Passagassawakeag-Bucksport block which extends to the contact of

the Vassalboro (Bucksport) with the Penobscot formation. This block

contains rocks ranging from pre-Cambrian to Devonian age and also

contains the portion of the ~ucksport (=Vassalboro). formation that

has been thermally metamorphosed by the Lucerne pluton. To the

south of the Passagassawakeag-Bucksport block, the Lucerne has also

intruded the Penobscot block that extends from the Bucksport (=Vassal-

boro)-Penobscot contact to the Turtle Head fault. This block contains

the Ordovician-Silurian? Pen.obscot formation that has also been

metamorphosed by the Lucerne pluton. The Bucksport-Penobscot contact

has been interpreted by Wanes (1976) as an unconformity but may be a

fault since chlorite-biotite grade rocks of the Bucksport formation

are in contact with andalusite-cordierite rocks of the Penobscot

formation. Ludman (1978) has demonstrated that this contact is a

reverse fault to the Northeast of the Lucerne, but Ruitenberg and

Ludman (1978) interpret it as an unconformity in New Brunswick. South

of the Penobscot block is the Castine-Ellsworth or Coastal Volcanic

block. The boundary between these two blocks is the Turtle Head fault

zone which places andalusite-cordierite grade Penobscot formation against

biotite grade Ellsworth formation.

The number of faults in the area indicates a complex structural

history with faulting occurring at several different times. The Turtle

Head fault zone extends southwest from the southern end of the Lucerne

pluton and was active from upper Silurian-lower Devonian through middle

Devonian time (Wanes, 1976). This fault zone is a major northeast

14

trending strike slip zone and may have been utilized as a zone .,of weak-

ness intruded by the Lucerne and other major plutons found to the east

(Wones, 1976). The northeast trending Norumbega fault zone is also

a major strike slip fault, and as it truncates the Lucerne it must .be

younger than the Turtle Head fault zone. The Norumbega has been traced I

from Winterport to the Grartd Lake area northeast of the Lucerne, with

a minimum of 25 km of right-lateral displacement (Wones and Stewart,

1976). Similar strike slip faults have been mapped on strike in

eastern Maine and western New Brunswick (Larrabee, 1965; Van de Poll,

1973; Ludman, 1978)~ If these faults are the northeast extension of

the Norumbega, 25 km of right-lateral ·motion is also suggested in

Mississippian rocks near Fredricton, New Brunswick. A smaller post

intrusional fault which may be equivalent to the Sunnyside fault in

the Belfas.t area (Bickel, 1976) cuts the Lucerne within the Passagassa-

wakeag-Bucksport structural block. It is a vertical fault with both

vertical and horizontal displacements. Thrust faults have been

mapped to the southwest of the Lucerne in the Rockland area (Osberg

and Guidotti, 1974). This faulting has affected rocks that appear

to be correlative with the Penobscot formation near the Lucerne

(Ordovician-Silurian?). No available evidence indicates thrust

faulting of the Penobscot formation near the Lucerne, but this

cannot be ruled out. However, the present distribution of later

sediments (Bucksport = Vassalboro) and the structural blocks surround-

ing the Lucerne appear to be due to the action of strike~slip

faulting along the Turtle Head and Norumbega fault zones (Wones

and Stewart, 1976).

15

Recumbent folding and thrust faulting figure prominently ina

plate tectonic model proposed for eastern central Maine by Osberg

(1975, 1978). In this model, collision of continental plates in

early Devonian time caused abduction of a Siluro-Devonian turbidite

sequence with the formation of large nappes and east dipping thrust

faults. Continued compression caused thickening of the crust in this

vicinity and produced plutonism and regional metamorphism during the

middle Devonian. The model is proposed to explain the large recumbent

folds and thrust faults in central and western New England. However,

no firm evidence for major recumbent folding or thrusting involving

the Vassalboro has been found in the vicinity of the Lucerne pluton.

There is a long history of deformation in the rocks surrounding

the Lucerne pluton. The Passagassawakeag gneiss was deformed during

the pre-Cambrian (Stewart and Wones, 1974; Bickel, 1976). Cambrian

and Ordovician sediments of the Copeland, Ellsworth, and Penobscot

formations that uncomf ormably overlie the Passagassawakeag were

deformed prior to the deposition of the Buckspo_rt formation. Refolded

folds found in these formations are not observed in the Bucksport.

A later large-scale fold, the Liberty-Orrington anticline, is responsi-

ble for· the map pattern of pre-Cambrian and Cambre-Ordovician rocks

in the Penobscot block. The plunging nose of this fold is exposed

to the west of the Lucerne pluton. This major northeast trending

anticline is one of several mapped in east-central Maine and was

probably produced during the lower Devonian. A later post Lucerne

folding has produced small scale open folds in the Bucksport

(=Vassalboro). These folds strike Nl5E to N25E and· their axial

16

parallel to the intrusive contact of the Lucerne. Most of the

foliation observed in the pluton also is subparallel to this strike.

In the calcareous rocks of the Bucksport formation, com.-

positional layering may reflect original bedding. However, most of

the observed layering was formed by calcareous material transposed

from bedding. The transposed layers are nearly vertical and parallel

to the axial planes of the small scale folds striking N25E (see fig.

17). Compositional bands in the calc-silicate gneiss of the contact

aureole also have this strike and dip. Similar transposition of

bedding has been reported from the calcareous rocks of ,the Flume

Ridge formation, though to be correlative with the Bucksport forma-

tion, to the northeast of the Lucerne (Ludman, 1978). Near the contact

of the Lucerne, whitish veins of zoisite are found at the center of

some of the calc-silicate layers. These veins may be beds that were

originally calcite rich due to transposition of calcareous material.

Thermal metamorphism has produced the abundant zoisite. Alternatively,

these veins could be equivalent to quartz-calcite veins found outside

the thermal aureole. Where deformation of low grade rocks has taken

place, e.g., near the Norumbega fault zone, these veins are stretched

and boudinaged into thin discontinous layers. These small characteris-

tics are found in the whitish veins within the thermal aureole of

the Lucerne.

Several metamorphic events have been noted in the rocks surround-

ing the Lucerne pluton. The earliest is metamorphism of the pre-Cambrian

Passagassawakeag gneiss. This formation was metamorphosed to silli-

manite grade prior to deposition of the Cambrian Copeland formation.

17

Figure 17. Sketch of outcrop showing transposed bedding in the Bucksport formation. Original bedding is shown by theisoclinly folded layer angling from upper right to lower left across the page. Transposed layering is shown by the nearly straight layers running from upper left to lower right. These layers parallel the axial planes of folds in original bedding. Width of outcrop perpendicular to trans ... posed layering is approximately 2 meters. Outcrop is located along Route 1 approximately 900 meters northwest of East Holden.

I I

'! I /JI / ; 1J I / 11

'111111 I I I

J J

18

OUTCROP SKETCH SHOWING TRANSPOSED BEDDING

LOCATED 900 M NW OF EAST HOLDEN

19

A later metamorphism affected the Ellsworth formation, in the coastal

Volcanic block to the southeast of the study area. Metamorphosed

fragments of the Ellsworth formation (Cambra-Ordovician) are found

at the unconformity within the Castine volcanics (Silurian). This

dates the metamorphism at Cambre-Ordovician to mid-Silurian (Stewart

and Wanes, 1974). Metamorphism of the Penobscot formation to c.ordi-

erite-andalusite grade could have taken place at any time between

the Ordovician and early to mid-Devonian. The metamorphic event

that produced the chlorite-biotite grade rocks in the Vassalboro

formation must be post-Silurian (Wanes, 1976). The Parks Pond

Monzonite metamorphosed the Bucksport formation prior to the in-

trusion of the Lucerne pluton. Sampling of the Lucerne aureole was

more than 3 km from the exposed monzonite so that superposed meta-

morphism should not have affected the samples. However, the position

of the Parks Pond prior to the intrusion of the Lucerne is unknown.

The hybridized zone southeast of the Lucerne contains inclusions of

material similar to the Parks Pond Monzonite. This indicates the

monzonite contact could have been close to the western edge of the

Lucerne, so may have affected the Bucksport formation in this area.

Textural evidence in the Bucksport indicates only one metamorphic

event, however. No reaction rims, overgrowths, psedumorphs or other

signs of multiple metamorphism were observed in any of the Bucksport

samples.

A series of granitic plutons intrude the various structural blocks

surrounding the Lucerne pluton. Isotopic ages for most of the plutons

are 375 ± 25 my in age (Brookins, 1976) and at present the concordance

20

and precision of these ages cannot be used to establish an intrusion

sequence. However, geologic evidence can be used to construct an in-

trusive history. The oldest dated intrusive is the Stricklen Ridge

pluton, a pegmatitic body within a pre-Devonian migmatite terrane.

The next older appear to be the Wallamatogus and South Penobscot

plutons to the south of the Lucerne. Both are cut by the Lucerne.

The Wallamatogus pluton contains garnet, sillimanite and muscovite and

appears to have crystallized at a somewhat deeper level than the

surrounding plutons. The Mt. Waldo pluton to the west of the Lucerne

is inferred to be younger than the Wallamatogus since it intrudes

and metamorphoses the Siluro-Devonian Bucksport (=Vassalboro)

formation while the Wallamatogus is confined to the older rocks of

the Penobscot block. On the northwest, the Lucerne also intrudes

the dike-like Parks Pond Monzonite. The relationship of this body

to the other surrounding plutons is unknown, however, it intrudes

and metamorphoses the Bucksport formation. Thus the Lucerne pluton

appears to be the youngest intrusive body in this area, except for a

single basaltic dike observed on the western edge of the pluton.

The Lucerne pluton is a large (20 x 60 km), biotite-bearing,

granitic pluton (Wones, 1976). It consists of coarse, tabular

potassium feldspar phenocrysts, some with viborgitic texture, in a

seriate groundmass of plagioclase, alkali feldspar, and quartz.

Biotite is the predominate maf ic phase and ilmenite is the common

oxide. A few grains of tourmaline have been observed. These mafic

minerals make up about 8% of the rock. The white alkali feldspar

and plagioclase give the rock its very light color. All of the

21

observed contacts except for the Norumbega fault are intrusive

and quite sharp. Geophysical studies indicate sharp, essentially

vertical contacts for the pluton (Sweeney, 1972). At the north end

of the pluton, a porphyritic f acies is developed in the core of the

pluton. It consists of coarse alkali feldspar, plagioclase, quartz,

and medium-grained biotite in a groundmass of mediumigrained quartz,

plagioclase, alkali feldspar, and fine-grained biotite. Miarolitic

cavities are found in this facies. A few small aplitic dikes intrude

the pluton and the country rock.

PETROGRAPHY OF LOW GRADE BUCKSPORT FORMATION

The Bucksport formation is a calcareous, quartzofeldspathic

. pelite interbedded with a highly phyllitic, rusty weathering pelite.

This formation is uniform over large areas in the sense that these

two rock types are present in roughly the same proportions and

appearance. The pelite is generally less than 30% of any given out-

crop. The Bucksport in the vicinity of the Lucerne pluton is thought

to be correlative with the Vassalboro, Kellyland, and Flume Ridge

formations found at various locations in eastern Maine, but may not

be correlative with the Bucksport as mapped by Bickel in the Belfast

area (Osberg, 1968, Larrabee, 1965; Ludman, 1978; Bickel, 1976; Wanes,

1976).

Outside of the contact metamorphic aureole, 70-80% of the

Bucksport consists of a massive, grey to green schist composed mainly

of quartz, calcite, and albite with smaller amounts of muscovite,

biotite, and chlorite. Tourmaline, apatite, and ilmenite occur as

accessory minerals. Randomly spaced laminations .5 -2mm in width are

22

common and are caused by higher concentrations of calcite and lesser

amounts of phyllosilicates. These layers weather to a lighter

greenish brown color giving the rock a distinctive striped appearance

in weathered outcrops. The calcite rich layers apparently represent

original bedding features and have been folded into small scale open

folds with the axial planes striking N25E. Grain sizes in these rocks

is uniform and quite fine (<.l-.3mm). Isolated larger grains of

muscovite are found scattered through the rock and are probably

detrital, although muscovite is also present in elongate stringers

interleaved with chlorite. Some of the detrital muscovite grains are

kinked. Biotite is found in varying amounts and may be absent from

samples of thin section size. 'It is always associated with muscovite

and chlorite. A moderately well defined schistosity is formed by

intergranular stringers of muscovite, chlorite and ~iotite with the

long axes of quartz grains parallel as well.

Approximately 20-30% of the Bucksport formation consists of finely

laminated beds composed primarily of muscovite with some quartz,

plagioclase, and pyrite. Beds of calcareous material may be several

meters thick while the pelite beds are less than a meter thick. The

grain size is extremely fine (<.Olmm) and the rocks have a highly

crinkled and well developed schistosity. The quartz and feldspar are

generally found in layers that parallel the schistosity and are

probably the result of metamorphic segregationrather than original

bedding. In hand specimen these rocks are shiny greenish grey to

black with a very irregular surface due to breakage along the

schistosity. These beds are rusty weathering because of the presence

23

of pyrite.

MINERAL CHANGES IN THE BUCKSPORT FORMATION

Near the contact of the Lucerne pluton, a distinctive series

of mineral changes is observed within the rocks of the Bucksport

formation. In the field, the massive grey calcareous schists and

phyllites are recrystallized to banded calc-silicate gneiss with

pelitic interbeds. The calc-silicate layers assume a grey to greenish

grey cast due to the presence of actinolite and diopside while the

pelitic material appears purplish due to the larger amounts of biotite.

Concurrently, the amount of calcite in the rocks decreases markedly

as shown by the lack of reaction with HCl. Bedding in the low grade

metamorphics (strike N25E) gives way to thicker compositional banding

that dips 80-90 degrees and strikes N30E, subparallel to the igneous

contact. These layers, while related to original bedding, are mainly

the result of metamorphic differentiation.

The lowest grade assemblage observed in the Bucksport formation

is: quartz + calcite + albite + chlorite +muscovite + biotite +

ilmenite + tourmaline. With increasing grade, muscovite and chlorite

disappear, biotite increases and the plagioclase changes composition

to about An30. In thin section, biotite occurs between chlorite

and muscovite in the presence of calcite, albite, and quartz. This

·type of assemblage may be the result of a reaction such as:

Muscovite + Calcite + Quartz + Chlorite = Biotite + Anorthite + H20 + co2 (1)

5KA13si3o10 (OH) + 8Caco3 + 7Si02 + 3Mg5Al2si3o10 (0H) 8 = 5KMg3Alsi3o10 (OH) 2 + 8CaA12si2o8 + 12H20

24

(Crawford, 1966; Chatterjee, 1971; Ferry, 1976a). The modal

percentages of muscovite and chorite are not equal and it is

probable that muscovite is consumed first. In two samples a.t this

grade, coexisting plagioclases of different composition were observed.

In the lower grade sample, ,the plagioclase compositions (An0-1 vs

An30-33) are consistent with those proposed for the peristerite

solvus as observed in metamorphic rocks (Crawford, 1966; Jones, 1972).

In the higher grade sample that contains actinolite without diopside,

plagioclase near An40 coexists with albite. This is indicative of

disequilibrium as large detrital albites persist to this grade. No

coexisting plagioclases were observed at higher grade.

With increasing grade, calcic amphibole forms along with a very

small amount of potassium feldspar. Textural existence indicates the

amphibole forms at the expense of biotite by the reaction:

Biotite + Calcite + Quartz =

Ca Amphibole + K"<"·feldspar + H2o + co2 (2)

5KMg3AlSi3o10 (0H) 2 + 6CaC03 + 24Si0 2 =

3Ca2Mg5Si8022(0H)2 + 5KA1Si308 + 6C02 + 2H20

(Hewitt, 1975). Compositions of coexisting biotite, calcic amphibole,

and potassium feldspar plotted on a diagram with coordinates FeO,

MgO, and K20 (fig. 2) show three phase triangles shifted as a result

of differing conditions of formation. Very little potassium feldspar

was found associated with the products of this reaction and most of

that was identified during microprobe examination. The potassium

feldspar that was present occurs as extremely fine intergrowths with

plagioclase. This lack of feldspar may be due to the relative mobility

25

Figure 2. Compositions of coexisting actinolites (open figures) biotites (closed figures) and alkali feldspar co-existing with calcite and quartz. All samples from the Bucksport formation. Each point was plotted on the basis of FeO + MgO + K4o.= 100%. The approximate order of increasing grade is: OND lllb, ORA 24, ORC 27, ORC 23, ORA 2la. Increasing Fe in the biotite and actinolite indicates an Fe-Mg exchange reaction.

26

LU ~

w :i 0

~ ~ ~ ~ 0 0 iii cl

ORA 210 • 0 ORA 24 • 0

ORC 27 • A

ONO lllb • 0 ORC 23 • 0

BIOTITES

MgO

27

of K2o in the metamorphic fluid. Vidale (1969) shows that potassium

feldspar from calc-silicate bands in regionally metamorphosed lime-

stones is concentrated in associated pelite beds. Large concentrations

of feldspar were not observed in the pelitic layers of the Bucksport

formation. The potassium feldspar may have reacted with chlorite

in the pelitic layers to produce the abundant biotite found throughout

the aureole. In addition, circulating fluids could have carried some

feldspar components out of the system. Some amphibole may have been

produced by reaction of excess chlorite with calcite in the calcareous

beds (Ferry, 1976a). This could not be verified texturally in the

Bucksport formation.

Above the grade at which amphibole is formed, zoisite is stable

in all calc-silicate assemblages. The zoisite coexists with plagio-

clase, calcite, or both, so it appears to be the result of the reaction:

Anorthite + Ca~cite + H20 = Zoisite + C02

3CaAlzSi208 + CaC03 + HzO = 2Ca2Al3Si3012(0H) + co2

(3)

Most frequently the zoisite is found in an extremely fine grained

mixture of calcite plus quartz. In some samples, whitish veins are

at the center of calc-silicate bands that consist of larger grains

of diopside, quartz, and sphene in a groundmass of fine zoisite. The

textural relationship suggest that the zoisite has replaced the

plagioclase of the groundmass outside the vein. Varying amounts of

calcite may remain in these veins. The whitish veins probably

represent thin calcite and plagioclase rich layers originally formed

during transposition of bedding. With higher temperature conditions,

calcite has reacted with the anorthite rich plagioclase to form

28

zoisite. Zoisite can also form as a product of the reaction of

amphibole to diopside since aluminum present in the amphibole is

not found in the pyroxene (Hewitt, 1973a).

At the highest grade within the aureole, the greenish calc-

silicate bands consist of small rounded diopside grains associated

with plagioclase (An90), quartz, sphene, zoisite, and calcite. Some

of these grains retain the elongate habit of the repalced amphibole

and, in transitional zones on the edges of calc-silicate bands, clearly

replace amphibole. The production of diopside is probably the result

of the commonly deduced reaction:

Ca Amphibole + Calcite + Quartz =

Diopside (+ Zoisite) + H20 + co2 (4)

Ca2Mg5si8o22 (0H) 2 + 3Caco3 + 2Si02 = 5CaMgSi2o6 + H20 + 3C02

(Skippen, 1974, Slaughter, Kerrick and Wall, 1975). A diagram with

coordinates FeO, MgO, and Al2o3 (fig. 3) shows the compositions of

coexisting actinolite, diopside, and zoisite. The amphibole in this

area is slightly aluminous actinolite (Leake, 1978). Upon reaction

of the amphibole to diopside, the aluminium probably reacts to form

the small isolated zoisite grains frequently associated with diopside,

or anorthite component, depending on the composition of the metamorphic

fluid present. Some of the larger diopside grains show well developed

lamellae that may be due to exsolution or twinning. Small isolated

zoisite grains are usually associated with rounded and well crystalized

hematite, suggesting a moderately oxidizing environment.

29

Figure 3. Compositions of coexisting diopsides (triangles), actinolites (squares) and zoisites (circles) from two samples in the Bucksport formation. Each point plotted on the basis of FeO + MgO + Al 2o3 = 100%. The variation in zoisite composition is actually due to Fe2o3.

.)0

Al 20 3 ~

ZOISITES ~~

•

ZOISITE ACTIHOLITE OIOPSIOE ONO 2e • • • ORA 210 ° 0 6

Co.I ACTINOLITES

• .c. .t. •

A~--= .. ::.....:~~~'--~--Y-~~-¥-~~--~---MgO FeOL----lL----...¥.-------~

31

The purple biotite schists that occur interbedded with the calc-

silicates uniformly consist of biotite + plagioclase + quartz + pyrite

in varying proportions, with apatite a common accessory. Immediately

at the granite contact, one sc;i.mple contains small rounded grains of

corundum in a biotite-plagioclase schist and probably represents a

muscovite-rich quartz-poor bed. Corundum was probably produced from

the dehydration of muscovite through the reaction:

Muscovite = Corundum + K-feldspar + H2o

KA13Si3o10(0H) 2 + A12o3 + KA1Si3o8 + 2H20

MINERAL CHANGES IN THE PENOBSCOT FORMATION

(5)

Mineralogical changes in the Penobscot formation within the

thermal aureole of the Lucerne are less obvious than in the Bucksport

formation. The extensive reconstitution visible in the Bucksport is

not as well developed. Layering on the scale of l-5cm may be bedding

and is mainly due to variation in the proportions of micas to quartz

and feldspar. This layering, while not as strongly affected by the

Lucerne as in the Bucksport formation, is strongly folded in some areas.

The lowest grade assemblage observed is biotite + muscovite +

quartz + plagioclase + andalusite + cordierite + pyrrhotite. This

assemblage was formed during earlier (regional) metamorphism of the

~Penobscot formation and may be related to the intrusion of the

Wallamatogus pluton. Andalusite is the stable aluminosilicate through-

out the formation. Cordierite is fauna both with and without anda-

lusite in rocks of suitable bulk composition throughout the aureole.

Compositions of coexisting cordierite, biotite, and andalusite are

plotted in figure 4. Near the contact, symplectites of muscovite +

32

Figure 4. Compositions of coexisting cordierite (filled symbols) and biotite (open symbols) in equilibrium with anda-lusite, muscovite, and quartz. This diagram is a projection through muscovite.

33

Alz03- 3K20 ANOALUSITE

BIOTITES

ELA 7 ELA 8 ELA 13

COROIERITE BIOT IT E

• ... •

0

A

0

34

quartz become more and more connnon until nearly all of the muscovite

has been consumed. Andalusite is commonly found as small rounded

grains within the mixture indicating the reaction:

Muscovite + Quartz = Andalusite + K-f eldspar + H2o (6)

KA13s13o10 (0H) 2 + Al 2Si05 + KA1Si308

Potassium feldspar is very common in rocks at higher grade. At the

contact, one thin bed shows rounded and embayed grains of corundum

with rims of muscovite in a matrix of biotite and plagioclase. This

bed lacks potassium feldspar and quartz and there is a thin zone in

the adjacent bed where potassium feldspar is depleted. The texture

suggests the muscovite is forming from the retrograde reaction:

Corundum + K-feldspar + H2o = Muscovite

Both of the samples from the Bucksport and Penobscot formations

that contain corundum occur directly at the contact with the Lucerne.

The restricted occurrence indicates that corundum formed as a prograde

mineral due to thermal effects of the intrusion. The beds that formed

corundum were probably phyllitic with a very high percentage of

muscovite and very little quartz. For this reason, muscovite survived

to high enough grade to react:

Muscovite = Corundum + K-feldspar + H2o (5)

In the Penobscot sample enough K-feldspar was present to allow the

retrograde reaction to occur producing the muscovite rims. In

contrast, insufficient K-feldspar remained in the Bucksport sample

to produce the retrograde reaction.

Pyrrhotite is the dominant sulfide in the high grade Penobscot

formation and is abundant in some samples. Graphite is also present

35

in both high and low grade samples. Reaction of pyrite to form

pyrrhotite in the presence of graphite probably involves Fe-Mg

silicates through such reactions as:

Chlorite + Pyrite + Graphite =

Pyrrhotite + Aluminosilicate + Quartz + co2 + H20

or

Biot'ite + Pyrite + Graphite =

(7)

K-feldspar + Pyrrhotite + Quartz + C02 + H20 (8)

Garnet is notably absent from the Penobscot formation. This is

apparently due to reactions such as the above causing an effective

change in bulk composition of the silicate assemblages. Iron in-

corporated by the pyrrhotite might shift the bulk composition to the

Mg-rich side of the biotite-aluminosilicate tie line, thus giving

the assemblage biotite + cordierite + aluminosilicate (fig. 4).

Textural evidence for this reaction occurs in sample ELA8 where

embayed pyrite grains are rimmed by pyrrhotite. It is also possible

that the original bulk composition of the Penobscot formation may

have been too magnesian for the formation of garnet.

MINERAL CHEMISTRY

Maximum information about the intensive variables during meta-

morphism requires determination of the chemical compositions of the

coexisting minerals. Microprobe analyses are used to explore the

variations for a given mineral group as well as variations between

groups. Mineral analyses were performed on an automated ARL-SEMQ

microprobe with an accelerating voltage of 15kv and beam current of

36

lOua. Nine major element analyses were made with a 10 sec. count

time using natural silicate and sulfide mineral standards. Data

reduction followed the method of Bence and Albee (1968) with correction

factors from Albee and Ray (1970). Mineral analyses were recalculated

by computer using the programs of Rucklidge (1972) and Goff and

Czamanske (1972) for amphiboles. Each reported mineral analysis

represents single analyses with totals of 100+2 weight percent that

best fulfill the stoichometry.

A plot of Fe vs. Mg per formula unit (fig. 5) for the ferro-

magnesian minerals of the Bucksport formation shows a generally

similar Fe/Mg ratio for biotite, diopside, and some chlorites. This

is evidently due to the fact that the Fe/Mg ratio of the precursor

minerals exerts some control on the Fe/Mg ratio in the higher grade

minerals. The overall Fe/Mg ratio probably reflects accurately the

original bulk composition of the sediment that formed the Bucksport

formation. While some of the amphlboles have similar Fe/Mg, there is

clearly a greater variation than in any of the other minerals.

Amphiboles coexisting with diopside have Fe/Mg similar to other minerals

while those coexisting with biotite and chlorite have wide Fe/Mg

variation. At least some of the Fe/Mg variation in the amphiboles

of the Bucksport formation can be attributed to Fe/Mg variation in

chlorite. In addition, an amphibole forming reaction apparently

proceeds at somewhat higher grade than the biotite forming reaction.

That is, once muscovite is consumed by the formation of biotite,

excess chlorite reacts with calcite to form amphibole. This is

consistent with observations by Ferry (1976a) although textural

37

Figure 5. Plots of total Fe per formula unit against total Mg per formula unit for minerals in the Bucksport and Penobscot formations. All diopsides, chlorites and actinolites are from the Bucksport formation. All cordierites are from the Penobscot formation. Patterned areas repre-sent different samples and show variation within individual samples. The line drawn through the mineral groupings show the similarity in Fe/Mg for the minerals and probably reflects the bulk Fe/Mg of the Bucksport forma-tion. This line is for reference only and is not a re-gression line.

3 I '

I I

SLOPE =

0.795 ~

/ +

-·-c :::> c 3

2 E '-

00 ~

M

'-Q)

a. Q

) LL -0 +

-

~

0 I

2 3

4

Total Mg per Form

ula Unit

39

evidence in the Bucksport formation is lacking. Formation of biotites

with the restricted Fe/Mg observed would tend to leave Mg enriched

chlorites. These chlorites would then react with calcite to form

amphiboles higher in Mg than those formed froinbiotite. Chlorites

coexisting with.amphibole are more magnesian than those without

amphibole. For comparison, cordierites and biotites of the Penobscot

formation are also plotted in fig. 5. Both of these show a much more

limited Mg c.ontent than the Bucksport minerals and there is also a

less well developed correlation of sympathetic Fe-Mg variation.

The chemical variation of the amphiboles as a group was investi-

gated to see what, if any, substitutions were occurring that might

affect the variation of Fe/Mg. Site assignments for the amphiboles

were calculated with the program of Goff and Czamanske (1972) with

the Fe+3 estimated using the method of Ferry (1976b). Amphiboles

from the Bucksport formation are actinolites (Leake, 1978). Coupled

substitutions possible in amphiboles have been outlined by Robinson

and others (1971) and Czamanske and Wones (1973). Czamanske and

Wones point out that calculated site assignments are sensitive to

assigned Fe+3 , but that the trends shown by site substitutions

would not be significantly affected by errors here.

A plot of AlIV vs FeVI (fig. 6) shows that changes in Fe

content take place without affecting Al1v. A plot of Mg+ Si vs Al IV

+ AlVI (fig. 7) shows an excellent linear correlation suggesting that

the tschermakite substitution is causing variation in tetrahedral

Al. The edenite substitution is also causing . . . Al IV variation in

shown by a IV total A site occupancy (fig. 8). content as plot of Al vs

40

Figure 6. Plot of tetrahedral Al vs octahedral Fe for amphiboles in the Bucksport formation. Open circles represent sample ORC 27. Changes in oct. Fe occur without affecting octahedral Fe.

-<t

1.0 0

0.8

0.6 •

0.4

0.2 • • •

41

0

• • •

• •

• •

0-----------------'-------------------1.0 1.2 1.4 1.6 1.8 2.0 Fen

42

Figure 7. Plot of octahedral plus tetrahedral Al vs octahedral Mg plus tetrahedral Si for Bucksport amphiboles. Open circles represent sample ORC 27.

43

1.0

0 0.8

N 0.6 0

·~ -<.t 0 + 0.4 • P1 •• '· <( ••

0.2 • • •

0 ---""----..L..----1 5.0 5.5

Mg·:iI.+ S iN/ 2

44

Figure 8. Plot of tetrahedral Al vs total A site occupancy for Bucksport amphiholes. Open circles represent sample ORC 27. The line is drawn for reference only to show a 1:1 slope.

1+5

0.6 0

0

oL_ .. 1 ~·------1 iL 0 0.05 0 .. 10 0.15

TOT A

46

The 1:1 slope of this line indicates that there is little coupling

of other substitutions that would affect tetrahedral Al content.

The intercept near .2 AlIV indicates that some other substitution

IV i.e. tschermakite, is operating producing an excess of Al •

There is a slight excess of total Al over AlIV as shown by the

AlIV vs total Al plot (fig. 9). This indicates the major tschermakite

substitution is:

Fe(III)IV + AlVI =Mg + Si

but there is also a slight amount of the substitution:

AlIV + AlVI =Mg+ Si.

This coupling identifies these amphiboles as hastingsitic (Czamanske

and Wones, 1973).

Biotite is another commonly occurring mineral in both the Bucksport

and Penobscot formations. As the Fe/Mg plot (fig. 5) shows, there is

much less variation of biotite composition than for amphiboles. The

Penobscot biotites show a higher Fe/Mg probably reflecting differing

bulk compositions between the two formations. The major variations

in chemistry expected in the biotites is substitution of AlIV + AlVI

for R +2 + Si. A plot of Al IV vs Fe (fig. 10) shows that biotites from

the Bucksport formation lie along a line with a slope of one

indicating that this substitution is producing variation in aluminum

content. Since Fe+3 was not determined the effect of this omission is

not known. Biotites from the Penobscot formation also show a

relationship between AlIV and Fe, but the slope for this line

indicates 4Fe = lAl. Charge balance would have to be made up by

additional substitutions possibly involving Fe(III) or Ti, however,

4.7

Figure 9. Plot of tetrahedral Al vs total Al for Bucksport amphiboles. Open circles represent sample ORC 27. The line is drawn for references only to show a 1:1 slope.

-I 0

0

0 .. I\)

0 . ~

0 c,,

i! ,.. 9 CD

l> -· . 0

. I\)

. en

0

48

Al :m: 0 0 0 0 . . . . . I\) 0

0

0

49

Figure 10. Plot of tetrahedral Al vs octahedral Fe for biotites in the Bucksport and Penobscot formations. Closed circles are Bucksport biotites and open circles are Penobscot biotites. The Bucksport biotites lie along a line with a 1/1 slope indicating a coupled sub-stitution between octahedral and tetrahedral sites. The Penobscot biotites lie along a line with a slope of 1/4.

o'r 11"1

3.0

I I

I I

I I

I I

I I

I I

I I

I I 0

o PE

NO

BS

CO

T 0

2.8

L •B

UC

KS

PO

RT

•

0 •

0 •

2.6

L 0

• <1 0

0 •

0

I •

• • • •

• • ~ 2.4 ~

• ••

• •

• •

• • <t 2.2 ~

. ' r--

•

2.0 I I

I I

I I

I e

e .I

I ,w

x:d I

' '

' I

1.8 2.0

2.2 2.4

Fe JI 2.6

2.8 3.0

3.2 3,4

51

the lack of Fe(III) determination precludes a solution. No correla-

tion of Ti with any other element was observed.

Analyses of pyroxene for higher grade Bucksport samples show

compositions midway between diopside and hedenbergite. Again, the

Fe/Mg ratio (fig. 5) probably reflects bulk compositional influence.

The main deviation from quadrilateral components is Al which is present

in amounts up to 2.4 wt%. This is due to MgAl-CATS substitution IV (Papike and Cameron, 1976) as shown by a plot of Mg vs Al (fig. 11).

No correlations of AlIV were found with any other major cation and

all other non-quadrilateral components are present in very small

amounts.

Zoisite is commonly found in rocks of the Bucksport formation

that also contain diopside. The compositions range from nearly

pure zoisite up to the beginning of the clinozoisite range of composi-• tion.s (30 mole% epidote component).· Most fall in the compositional

range 0-25 mole% epidote component. A plot of Fe (assumed Fe+3) vs

Al (fig. 12) shows that Fe+3 substitutes directly +3 for Al • Although

no optical zoning was noted in the zoisites, compositions vary somewhat

within grains. One exception to this sample ORB 15, an albite..;..

chlorite-zoisite rock in which small rounded zoisite grains contain

concentric optical zones around a distinctly different core. Energy

dispersive analysis shows that the cores contain cerium while the

outer zones do not. No compositional differences were found between

the optically distinct zones. These grains may represent altered

allanite grains from a highly deformed igneous dike. No compositional

break was observed in the zoisites which agrees with the epidote

52

Figure 11. Plot of tetrahedral Alvs octahedral Mg for pyroxenes from the Bucksport formation. The line has a slope of 1/2. The linear relationship shows substitution of Al in cpx is due to the MgAl-Calcium Tschermakite substitution. The line is for reference only.

0.05

O.O I

53

• • . :/: •

o.s 0.6 Mg

54

Figurel2. Plot of octahedral Al vs Fe+3 in zoisites ff_~m the Bucksport formation. All Fe ~~s assumed Fe • The 1:1 relationship indicates Fe substituted directly for Al in zoisites. The line drawn is for reference only.

55

3.0 ~-------_,..... ______ _..,.

2.9

f;:1 2.8

<( 2.7

2.6 1: 1

2.5 ____________________________ --.l

0 0.1 0.3 0~4

56

miscibility gap existing at higher molar epidote compositions

(50-75 mole%; Raith, 1976).

INTENSIVE VARIABLES DURING METAMORPHISM

Pressure During Metamorphism

One of the most important pieces of information about the

geologic history of an intrusion is the depth of crystallization.

The mineralogical data compiled on the assemblages of the contact

aureole allow an estimate of the depth of the present erosional level

during contact metamorphism. Several pieces of information suggest

a relatively low lithostatic pressure during intrusion.

Andalusite is the stable aluminosilicate in the aureole and it

occurs within 15 m of the contact. Therefore, if the temperature

at the contact is known, an upper limit can be placed on the litho-

static pressure. Figure 13 shows the position of the andalusite=

sillimanite curve as determined by Holdaway (1971) with the dashed

curve giving the position determined by Richardson, Gilbert, and Bell

(1968). Recent measurements of the enthalpy of solution for anda-

lusite by Anderson, Newton, and Kleppa (1977) show that the slope for

the andalusite=sillimanite curve is most accurately predicted by

Holdaway. In addition, they point out that the amount of Al-Si

disorder observed in natural sillimanites was accurately predicted

by Holdaway based on his experimental data. ·For these reasons the

lower pressure triple point of Holdaway is preferred, although neither

curve can be positively favored at this time.

The maximum temperature of the contact was the temperature at

which the Lucerne magma was intruded. The solidus temperature is

57

Figure 13. Pressure-Temperature diagram showing some reactions con-sidered in the Bucksport and Penobscot formations. All are plotted for PH20 = Ptotal' Data sources are: Holdaway, 1971; Chatterjee and Johannes, 1974; Hewitt, 1975; Holdaway and Lee, 1977, Richardson, Gilbert and Bell, 1968.

) .'·

-I fT1 3:: -0 rr1 :a ):> -I c ::0 f'Tl .

. --0 (') .......

~ 0 0

(J1 0 0

O') 0 0

-.J 0 0

N

58

P( kb) PH20 = ProT c.,.i . CJ1 O')

59

.·' 0 a minimum of 725 C from two feldspar geothermometry (D.R. Wanes,

personal communication, · 19 78 ):. ; however, the temperature of the

country rock at the contact was probably somewhat less. Cal~

culations by Jaeger (1957, 1959) suggest that the contact temperatures·

are near l00°C less than intrusion temperatures. Therefore, the

occurrence of andalusite restricts the pressure to less than 2000

bars using the Holdaway curve and less than 5000 bars using that of

Richardson, Gilbert, and Bell. Since contact temperatures may be

greater than 600°C, these are maximum pressures.

The occurrence of corundum at the contact in both the Bucksport

and Penobscot formations was probably the result of the reaction:

Muscovite = Corundum + Sanidine + H2o To have andalusite stable with the production of corundum requires

pressures less than 1.4 kb (3.3 using RGB) if P = P H2o total (Chatterjee and Johannes, 1974). However, the presence of pyrite in

the Bucksport formation and pyrrhotite + graphite in the Penobscot

formation indicates PH20 was probably less than Ptotal i.e. ~20 in the fluid was less than one. Calculations by Ohmoto and Kerrick

(1977) show that the maximum ~ 0 in fluids in equilibrium with 2

pyrrhotite + pyrite + graphite is .8 for temperatures near those

asstimed for the contact F0 = QFM). Since sulfur fugadties are 2

small compared to H20 and co2 , the absence of pyrite does not change

the amount of diluting species significantly. If the fluid did have

~ 0 = .7, the production of corundum with andalusite stable would 2

require pressures less than 1.9 kb (4.5 using RGB). Since~ 0 could 2

have been less than .7, the presenc~. of corundum does not limit the

60

possible lithostatic pressure more than the presence of andalusite.

An additional calculation of lithostatic pressure was attempted

using the method and data of Ferry (1976b) and microprobe analyses of

minerals from the Bucksport formation. This method is based on

linear combinations of mineral equilibria modified 'for solid solution

of the phases. The calculati~n yielded a value somewhat les\ than

3kb. Hotvever, the present accuracy of this type of calculation com ...

bined with the inaccurate temperature estimate for the sample gives

this value questionable significance. Ferry (1976b) estimates that

even with accurate temperatures, the method is accurate only to

+900 bars. The calculation does indicate a lithostaticpressure

consistent with the stability of andalusite and corundUm. when referred·

to the aluminosilicate diagram. of Holdaway (1971).

Independent evidence of lithostatic pressure during crystalli ...

zation comes from the porphyritic f acies of the Lucerne. This

rock contains miarolitic cavities indicating water saturation during

crystallization. In addition, the open cavities indicate PH 0 = . 2

P total during late stage crystallization. The temperature during

crystallization of this facies is a minimum of 675-700°c from two

feldspar geothermometry (D.R. Wones, personal communication, 1978).

Using the water saturated granite minimum of Tuttle and Bowen (1958),

these temperatures indicate pH20 during crystallization was 1500 ...

2500 bars. The few aplite dikes that cut the Lucerne were probably

also water saturated during crystallization. Comparison of the

normative data for the aplites (D.R. Wones, personal communication,

·1978) with the water saturated minimum of the Ab ... Or - Qtz system

61

indicates pressures of 500-1000 bars (Tuttle and Bowen, 1958). The

reason for this discrepancy could be alkali exchange of the feldspars

which would give a lower apparent pressure.

The assemblage muscovite + corrierite + biotite + quartz + alumina-

silicate (andalusite) present in the Penobscot formation has been

shown to be a good geobarometer if metamorphic temperatures are known

(Haase and Rutherford, 1975; Holdaway and Lee, 1977). The experimental

data of Haase and Rutherford and Holdaway and Lee along with data

provided by M. Rutherford (personal communication, 1978) are combined

in figure 15. Phase relations in this assemblage are greatly affected

by PH 0 and the diagram is plotted to show the effects of reduced 2

PH 0 • Thus, given that andalusite is stable and that the sample con-2

taining cordierite of composition XFe= .50 is at lower temperature than

the muscovite + quartz reaction temperature, the pressure would be a

maximum of 2.8 kb. If PH 0 is .5 Ptotal' the pressure would be 2.5 kb., 2

and further reductions of PH 0 would give still lower pressure 2

estimates. The pressure estimates apply to the Lucerne only if the

biotite and cordierite equilibrated within the contact aureole. No

cordierite was found nearer to the contact than SOOm and in one sample

nearer than this the cordierite was completely pseudomorphed by a fine

grained mixture of muscovite and chlorite. The calculated temperature

gradient for the Lucerne aureole indicates the samples lie within the

thermal aureole, although at a lower temperature than that indicated

by the biotite-cordierite pairs. The Kd values for the mineral pairs

are systematically related to the contact. Sample ELA 7 has a Kd

of 1. 39 while ELA 8 and ELA 13b has Kd' s of 1. 77 and 1.79 respectively.

62

Figure 15. Pressure-Temperature diagram showing a portion of Figure 13 with equilibria relevant to the Penobscot formation. The andalusite-sillimanite boundary is from Holdaway, 1971. All other curves from Holdaway and Lee, 1977. The shaded areas shows the stability field for Penobscot cordierites.

4

a..

2

63

>>>>: LIMITING CONDITIONS FOR THE ASSEMBLAGE -:·:-:-:-:-:-:-:· MUS+ 810 + AND+ CORO(XFe • .50) + QTZ IN

THE PENOBSCOT FORMATION ~

""

550 600 650

64

The samples closer to the contact have a lower Kd, although the XFe

of cordierites are less well correlated with distance. This dis-

turbance of Kd indicates the compositions of cordierite·-biotite pairs

re-equilibrated within the thermal aureole to reflect the conditions

of crystallization of the Lucerne. Variations in XFe are probably

due to bulk compositional variation or differences in PH 0 • 2

Available evidence of lithostatic pressure during intrusion

of the Lucerne pluton indicates values near 2000 bars with probable

maximum limits of 1000 bars. These values are compatible with both

aluminosilicate curves. Pressures near 3000 bars are unlikely if the

Holdaway diagram accurately represents the stability of andalusite.~

In addition, because feldspar temperatures may represent minimums for

the plutons, the Richardson, Gilbert and Bell diagram also limits

pressures below 3000 bars. If the lower contact temperatures near

625°C are assumed, the Richardson, Gilbert and Bell curve restricts

pressures only to less than 4500 bars.

Those values are lower than the 3-4 kb proposed for regional

metamorphism in central Maine (Osberg, 1968; Ferry, 1976b; Guidotti,

1970). Abbott (1977, 1978) has investigated the petrology of the

Red Beach granite near Calais, Maine and estimated conditions for its

formation. On the basis of a biotite + K-feldspar + magnetite

assemblage, a lithostatic pressure of 270-490 bars was calculated for

the intrusion of this pluton. Associated volcanics thought to be

petrogenetically related to the granite also give support for a very

shallow depth of intrusion. The Lucerne then appears to represent an

intermediate depth between the shallow plutons to the northeast and

65

the deeper intrusions of western and central Maine. This is supported

as well by the regional grade of metamorphism decreasing to the

northeast.

Temperatures During Metamorphism

Given that the lithostatic pressure during intrusion of the

Lucerne was between 1000 and 3000 bars, temperatures reached within

the contact aureole can be estimated. The pressure was probably

constant over the size of the study area although fluid pressures

may not have been equal to total pressure. Again the reactions

referred to are compiled in figure 13. The andalusite = sillimanite

transition provides a temperature maximum if a pressure is assumed.

Thus, given that andalusite is stable, the maximum temperature in

the aureole could be 700°C if a pressure of 1000 bars is assumed but

only 550°C if a pressure of 3000 bars is assumed, using the data

of Holdaway. These values would be 800°C and 720°C respectively

using the Richardson, Gilbert, and Bell curve. Both temperatures

determined by the Holdaway curve are consistent with feldspar

temperatures for the pluton although the lower temperature value

is unlikely. The preferred pressure of 2000 bars gives a temperature

maximum of 625°C which is in good agreement with the idealized values

for contact temperatures calculated by Jaeger (1957, 1959). Given

the possible pressure variation, the temperature range could be +75°C.

For the narrow range of crystallization temperatures indicated by the

Lucerne feldspars (700-750°C, D. R. Wanes, personal connnunication, 0 1978), Jaeger calculated a contact temperature of 512 C based on

66

assumptions of ideal conduction of heat away from an :igneous contact.

Since the rocks of the Bucksport formation were at biotite grade

prior to intrusion, the rocks were already at an elevated temperature.

Preheating of the country r~ck was ~ot taken into account in the

calculations by Jaeger and the additional. amount of heating brings

his calculated value within the estimated temperatures for the

Lucerne aureole.

The occurrence of corundum at the contact due to the reaction of

muscovite also gives an indication of contact temperature. To produce

corundum with andalusite stable requires a temperature of 660°C if

P = P If the value of 2000 bars is assumed for total pressure, H2o total"

production of corundum requires a temperature of 625°C with PH 0 = .77. 2

This agrees well with the assumption of reduced ~ 0 due to the presence 2

pyrrhotite + graphite. Corundum could be produced at lower temperatures

if ~ 0 is reduced still further. This would also be the case if the 2

total pressure was higher.

Approximately 136m (450 ft.) from the contact, muscovite+ quartz

is unstable due to the.reaction: Muscovite + Quartz = Andalusite + K-feldspar + H2o·

The temperature of this reaction is .also highly dependent on fluid

pressure or ~20 • However, both the theoretical calculations and

production of corundum at 2000 bars indicate ~ 0 was less than or 2

equal to .8 in the Penobscot formation. This restricts this reaction

to less than 574°C (Chatterjee and Johanees, 1974). Again, the lower

temperature limit for this reaction would depend on further reduction

of PH 0 or ~ 0 , or a higher total pressure. 2 2

67

The lowest grade Bucksport samples have a temperature maximum

imposed by the assemblage muscovite+ calcite+ quartz (Hewitt, 1973).

This reaction reaches a thermal maximum at XCO = .5. For a total 2

0 pressure of 2000 bars, this .reaction occurs at 475 C or less depending

on fluid composition. The low grade muscovites in the Bucksport for~

mation have a significant celadonite component. This reduces the

activity of muscovite in the mica and would cause the reaction to

occur at still lower temperatures. In addition, Ferry (1976b)

indicates that the reaction:

Muscovite + Chlorite + Calcite + Quartz =

Biotite + Anorthite + H2o + co2

occurs at lower temperature than the muscovite + calcite + quartz

reaction. This also indicates the low temperature estimate is

(1)

probably too high. The curves of Jaeger lie within the error brackets

of temperatures estimated for the Lucerne aureole. The curve for the

Lucerne actually lies at somewhat lower temperatures than those cal-

culated by Jaeger at larger distances from the contact. This is

probably due to endothermic reaction occurring within the aureole.

This additional source of heat loss was not taken into account in

the calculations by Jaeger.

FLUID COMPOSITIONS DURING METAMORPHISM

A metamorphic fluid phase was present in both the Penobscot and

Bucksport formations during production of the thermal aureole around

the Lucerne pluton. Abundant evidence of fluids is found throughout

the Bucksport formation where numerous veins containing quartz,

plagioclase, zoisite, and actinolite cut the rocks. Such prominent

68

Figure 16. Estimated temperature gradient for the Lucerne aureole. The solid circles give position of estimated tempera-tures at 2 kb with error brackets estimated. Both the muse + qtz = and + K-feldspar and muse + cc + qtz points are maximum temperatures as indicated by arrows. The two upper curves are calculated gradients from Jaeger (1957).

O'I

\C

650 u

r MUSC = CO

RUNDUM t K

FELDSPAR

~

600 w

0:: ::> ~

550-a:

MU

SC

I

+ Q =A

ND

w

CL ::;?:

500 L + KFE

LDS

PA

R

~· w

I-l

450

Tc = 62

5

18 km thick

Tc = 625 10 km thick

LUC

ER

NE

M

UStC

C+Q

-,

40

0 ....__ _

__

.._---.-&

-__

__

__

_ ...._

_-&

__

_.._ __

__

__

_ _

0 1000

2000 3000

4000

DIS

TAN

CE

FR

OM

C

ON

TAC

T (F

EE

T)

70

veining is not seen in the Penobscot formation, however, dehydration

reactions occurring in the aureole liberate H20 so some form of fluid

must have been present.

The metamorphic fluid present in the calcareous Bucksport

formation is assumed to have been a mixture of H20 and co2 since

prograde reactions give off H2o and co2 in various proportions. In

addition, H2o could be supplied by the Lucerne. ·The fluid composition

of rocks of the Bucksport formation outside the contact aureole could

not be determined. Ferry (1976b) suggests that low grade calcareous

rocks of the Vassalboro formation approximately 100 km west of the

Lucerne have co2 enriched fluids due to reactions at low grade that

produce co2 • However, the amount of dilution by H2o will depend upon

the amount of interbedded pelite reacting to give off H2o alone

(Hewitt, 1973a). Within a larger part of the aureole, the fluid

is clearly H2o rich as indicated by the presence of zoisite (see

figure 14). The zoisite commonly occurs in whitish veins within

calc-silicate bands, however, it is also found as isolate.d grains

throughout some of the high grade calc-silicates. Thus, it is not

limited to obviously H2o rich areas such as quartz veins. While the

exact position of the zoisite curve is in dispute, there is agreement

that H2o rich fluids (ZN rf:-.90) are necessary for its formation 2

(Storee and Nitsch, 1972; Kerrick, 1974). The source of this H2o rich

fluid could be the interbedded pelitic material undergoing dehydration

within the aureole or H2o being released during intrusion of the Lucerne.

During the production of prograde minerals within the aureole,

fluid compositions probably varied greatly between the highly calcareous

71

Figure 14. T-X diagram showing mineral reactions relevant to the Bucksport formation. The diagram is plotted for pfluid = 2000 bars. Data sources: Kerrick, 1977; Greenwood, 1967; Hewitt, 1973b, 1975; Kerrick, 1974.

N

........

-u 0

-700

w 600

0:: :::> ~ er: w

a..

500 ~

w

I-

400 (izo + co2

0 (\J :I: + u u

0

P = 2000 bars

~ /./l?O

•Co~ ·.

Mo~+c~

0.2 0.4

0.6 0.8

1.0

Xco2

73

beds and pelite beds. The calcareous beds had a higher co/H20

than the surrounding pelites because of decarbonation reactions.

The comm.on occurrence of isobaric "univariant" assemblages, such as

biotite + calcite + quartz + actinolite + K-feldspar, indicates

fluids in the calcareous beds were buffered by the calc-silicate

assemblages. In the Bucksport formation, these assemblages are not

truly univariant because of varying Fe/Mg and excess Al, however,

they do buffer the fluid composition. Fluids rich in co2 would explain

why calcite plus quartz survives in the calcareous layers at high

grade. 0 For a contact temperature of 625 C at 2 kb, the fluid would

have to have XCO >.3 (Greenwood, 1967). At some point, H20 rich 2

fluids must have been introduced to produce the abundant zoisite.

Zoisites have lower Fe contents approaching the Lucerne. Kerrick

(1977) shows that increasing Fe in zoisite increases :its stability

in more co2 rich fluids. Thus, it appears that H2o rich fluids

were associated with the intrusion of the Lucerne. These fluids

were released during late stage crystallization of the porphyritic

facies of the Lucerne where there is definite evidence of H2o satu-

ration. Introduction of fluids also produced the abundant veins

found at low grade. This must have occurred after peak metamorphism

at temperatures below the intersection of the Calcite + Quartz =

Wollastonite curve with the Anorthite + Calcite = Zoisite curve

(475°c in the pure system (fig. 13). The late stage deformation

seen in the Lucerne could have been responsible for fracturing of

the rocks, thus allowing access of H20 rich fluids. Abundant

zoisite bearing veins in the Bucksport formation fit with H2o rich

74

fluid circulation during production of the contact aureole. Cal-

culations by Ferry (1976b) indicates that co2 and H20 are by far

the most common fluid species in calcareous pelites at moderate

grade.

Pelitic rocks of the Penobscot formation were also coexisting

with a fluid phase during metamorphism, but of a different nature

than that of the calcareous Bucksport formation. Prograde reactions

in the Penobscot formation produce only H2o; however, the presence of

abundant pyrrhotite and graphite indicate fluid species were of the

C-0-H-S system. Calculations of fluid compositions coexisting with

graphite + pyrrhotite + pyrite at typical metamorphic conditions

show that H2o, co2, and CH4 are the main constituents of the fluid.

The difference between graphite + pyrrhotite + pyrite and graphite +

pyrrhotite is small because of the extremely low fugacities of sulfur

species in the fluid (Ohmoto and Kerrick, 1977). Due to the presence

of co2 and CH4 in the fluid, the maximum XH 0 of the fluid will be 2

.85-.75 at estimated conditions within the aureole (QFM Buffer). This

is essentially the same fluid composition required for the decomposition

of muscovite in the presence of andalusite at 2 kb (~ 0 = .77) 2

(Chatterjee and Johannes, 1974). The amount of dilution of H2o and co2

and CH4 is controlled by oxygen fugacity and shifts of less than one

log unit of oxygen fugacity could produce a change to XH 0= .5. 2

MINERAL ZONING IN THE BUCKSPORT FORMATION

Recrystallization of the Bucksport formation to the banded calc-

silicate gneiss within the contact aureole has probably been the result

75

Figure 18. Tracing of a photo of mineral layers developed in sample OND 2e. Pelite layer is on the left, calcareous layer is on the right. Tracing covers approximately 3 millimeters. Graph below the tracing shows plagio-clase compositions through the layer at the locations given by small spots in the tracing. The dashed vertical lines show the separate zones. The bottom, approximate modes are given for each layer. These are visual estimates only. Potassium feldspar was determined by microprobe.

-z ~ 80 ~ z 0 ... -en 60 0 A. 2 0 u

... en ~ 40 ..J u 0 ~ • ~ 20 t

TRACING

Qtz - 35 Bio - 30 Plag - 19 Op - 1

I

I

76

OF SAMPLE

t t

APPROXIMATE

Qtz - 50 Act - 37 Plag - 10 Ksp - Tr Sph - 2 Op - 1

ONO 2e

t1 t

MODES

63x

t t

Qtz - 34 Plag - 30 Dio - 30 Ksp - Tr Sph - 3 Zo - 2 Cal - Tr Op . - 1

t

( . . '

77

of both mechanical movement of material which produced the calcareous

and non-calcareous beds and thermal metamorphism. Wherever calcareous

layer$ are in contact with pelite layers, a distinct mineral zone is

developed between the two .layers. It consists of coarser actinolite

in a groundmass of quartz and plagioclase with traces of potassium

feldspar and sphene. The actinolites in this zone are coarser than

either the biotite or diopside in the adjacent layers. Layering is

on a very fine scale with the transition occurring over several milli-

meters or less. Figure 18 diagrams a mineral zone in sample OND 2e

for which microprobe data were obtained. The e2ttreme1y fine scale

of layering precludes accurate modes and the given modes represent

visual·estimates only. This zoning is found throughout the

Bucksport formation in rocks that contain diopside. The presence of

An25 plagioclase and lack of muscovite and chlorite in the pelite

indicates reaction 1 has gone to completion. The appearance of

actinolite coincides with a sharp increase in the artorthite content

of plagioclase probably because of excess aluminum released during

reaction of biotite to actinolite. The slight drop in anorthite

content of plagioclase in the diopside bearing zone is probably

due to the presence of zoisite as the result of reaction 3.

The sequence of minerl:lls developed could be caused by an

initial gradient in bulk .composition, with the amount of calcite

decre~ing as the pelite layer is approached. However, the thick-

ness of the zoning is generally constant from sample to sample and

is symmetrically developed on either side of calcareous layers. These

facts suggest compositional control is unlikely although an initial

78

compositional gradient must have been present. Two alternative

methods of producing this type of zoning at pelite-limestone boundar-

ies have been described by Vidale and Hewitt (1973). The first is

that the zones are produced by a co2/H2o gradient between the layers.

Each new mineral zone is produced by crossing an isobaric univariant

curve in T-x space at constant temperature. The zoning developed in

the Bucksport formation is consistent with this model only if the

calcareous layers have a relatively high CO/H2o (.::_. 75).

A second method of producing mineral zones is cation diffusion

(Vidale, 1969, Thompson, 1975). In this case, the mineral zones are

formed by diffusion of calcium out of the calcareous layers and

reciprocal diffusion of other elements into the calcareous layer.

This produces an effective change in bulk composition in the zones

which is responsible for the different assemblages. The sequence

of assemblages in the Bucksport formation is also consistent with

this model. Unfortunately, the scale of layering is so small that

the accurate modes needed to prove changes in bulk composition

cannot be obtained.

CONCLUSIONS

The Lucerne pluton has intruded a series of lower Paleozoic

rocks producing a contact metamorphic aureole about one kilometer

in width. In the Bucksport (=Vassalboro) formation, prograde

minerals are biotite, slightly aluminous actinolite, diopside,

and zoisite. Contact metamorphism also produced andalusite and

corundum. in both the Bucksport and Penobscot formations. The

minerals present in the aureole indicate crystallization of the

pluton at a pressure between 1000 and 3000 bars, equivalent to

3.5 - llkm depth. Crystallization 6f the pluton took place near

750-700°c while temperatures in the aureole ranged from near

600-6S0°c to less than 475°C. Contact metamorphism of the Bucksport

records a complicated history. Initial effects of the intrusion

or pre-intrusion faulting produced vertical calc-silicate banding

in the aureole by shearing and flattening these isoclinally folded

rocks. Calcareous material was transposed parallel to fold axes

forming alternating calcareous and pelite layers. Thermal meta-

morphism produced prograde minerals with the calcareous layers

remaining co2 rich because of fluid buffering by calc~silicate

assemblages. A late stage tectonic event, possibly associated with·.·

the Turtle Head fault zone, produced deformation and foliation

in the Lucerne and surrounding sediments. The rocks of the

aureole were fractured allowing circulation of H20 rich fluids,- .

possibly associated with late stage crystallization of the.porphyritic

facies of the Lucerne. These HzO rich fluids produced· the._ ~wiSite. ·

found near the pluton by reaction of calcite and anorthite~ ·

79

80

The present distribution of structural blocks surrounding the

Lucerne pluton appear to have been the result of strike-slip faulting

along the Turtle Head and Norumbega fault zones. However, thrust

faulting has also been proposed as a means of explaining the structure

of eastern Maine. The areas of western Maine that have unquestionably

been thrust faulted appear to show a somewhat higher pressure meta-

morphism than that estimated for the Lucerne (Ferry, 1976a,b,

Guidotti, 1970). In addition, detailed mapping northeast of the

Lucerne has not revealed major thrusts (Ludman, 1978, Ruitenberg and

Ludman, 1978). The low pressure of intrusion for the Lucerne is

consistent with a model of strike-slip faulting for the region

surrounding the Lucerne. This implies that either the thrust faulting

and recumbent folding observed to the southwest and west of the

Lucerne occurred before deposition of the Vassalboro (=Bucksport)

formation, or that the Vassalboro was involved in thrusting and

was extensively eroded prior to the intrusion of the Lucerne.

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New Brunswick: Queen'·s College Geol. Bull. no. 6, p. 17-37.

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Anderson, P.A.M., Newton, R. C., and Kleppa, O. J., 1977, The enthalpy change of the andalusite-sillimanite reaction and the Al2Si05 diagram: Amer. Jour. Sci., v. 277, p. 585-593.

Bence, A. E., and Albee, A. L., 1968, Empirical correction factors for the electron microanalysis of silicates and oxides: Jour. Geol., v. 76, p. 382-403.

Bickel, C. E., 1976, Stratigraphy of the Belfast quadrangle, Maine: In Page, L. R., ed., Contributions to the stratigraphy of New England: Geol. Soc. Amer. Mem. 148, p. 97-128.

Brookins, D. G., 1976, Geochronologic contributions to stratigraphic interpretation and correlation in the Penobscot Bay area, eastern Maine: In Page, L. R., ed., Contributions to the Stratigraphy of New England: Geol. Soc. Amer. Mem. 148, p. 129-146.

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----- and Johannes, W., 1974, Thermal stability and standard thermodynamic properties of synthetic 2M1 muscovite, KA12 (AlSi3o10 (oH2): Contr. Min. Petrol., v. 48, p. 89-114.

Crawford, M. L., 1966, Composition of plagioclase and associated minerals in some schists from Vermont, U.S.A., and South Westland, New Zealand, with inferences about the peristerite solvus: Contr. Min. Petrol., v. 13, p. 269-294.

Czamanske, G. K., and Wones, D.R., 1973, Oxidation during magmatic differentiation, Finnmarka complex, Oslo area, Norway: Part 2, the mafic silicates, Jour. Petrol., v. 14, p. 349-380.

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82

Doyle, R. G., and Hussey, A. M. (compilers), 1967, Preliminary geologic map of Maine: Maine Geol. Survey, Augusta, Maine.

Ferry, J.M., 1976b, P.T. fCO , and fH 0 during metamorphism of calcareous sediments in Ehe Water~ille-Vassalboro area, south-central Maine, Contr. Min. Petrol.: v. 57, p. 119-143.

------, 1976a, Metamorphism of calcareous sediments in the Waterville-Vassalboro area, south-central Maine: Mineral re-actions and graphical analysis, Amer. Jour. Sci., v. 276, p. 841-882.

, 1978, Fluid interaction between granite and sediment -----during metamorphism, south-central Maine: Amer. Jour. Sci., v 278, p. 1025-1056.

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------, 1976, Metamorphism at moderate temperatures and pre-sures: In Bailey, D. K., ed., The Evolution of the Crystalline Rocks: Acad. Press, p. 187~259.

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------, 1973b, Stability of the assemblage muscovite-calcite-quartz, Amer. Min., 58, 785-791.

------, 1975, Stability of the assemblage phlogopite-calcite-quartz: Amer. Min., v. 60, p. 391-397.

Holdaway, M. J., 1971, Stability of andalusite and the aluminosili-cate phase diagram: Amer. Jour. Sci., v. 271, p. 97-131.

, and Lee, S. M., 1971, Fe-Mg cordierite stability in high -----grade pelitic rocks based on experimental, theoretical, and natural observations: Contr. Min. Petrol., v. 63, p. 175-198.

83

Jaeger, J. C., 1957, The temperature in the neighborhood of a cool-ing intrusive sheet: Amer. Jour. Sci. , v.. 255, p. 306-318.

------, 1959, Temperatures outside a cooling intrusive sheet: Am.er. Jour. Sci., v. 257, p. 44-54.

Jones, J. W., 1972, An almandine garnet isograd in the Rogers pass area:, British Columbia: the nature of the reaction and an estimation of the physical conditions during its formation, Contr. Min. Petrol., v. 37, p. 291-306.

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------' .1977, The genesis of zoned skarns in the Sierra Nevada, California: Jour. PetroL , v .. 18, p. 144-181.

Larabee, D. M., ·Spencer, C. W., and Swift, D. J. P., 1965, Bedrock geology of the Grand Lake area,, Aroostook, Hancock, Penobscot, and Washington Counties, Maine: U.S.G.S. Bull. 1201-E, p .. 382 .•

Leake, B. E., 1978, Nomenclature of amphiboles, Amer. Min., v. 63, p. 1023-1052.

Ludman, A., 1978, Stratigraphy, structure, and progressive metamor"'."' phism of lower paleozoic rocks in the Calais area, southeastern Maine: In Ludma:O:, Allan, ed., NEIGC Guidebook for Field Trips in Southeastern Maine and Southwestern New Brunswick: Queen's College Geologl.cal Bulletin No. 6, p. 145-i61.

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Osberg, P. H., 1968, Stratigraphy, structural geology, and metamor-phism of the Waterville-Vassalboro area, Maine: Maine Geol. Survey Bull., v. 20, p. 60.

------, 1971, An equilibrium model for Buchan-type metamorphic rocks, southcentral Maine: Amer. Min., v. 56, p. 570-585.

-----, 1974, Forward to field trips in east-central and north-central Maine: In Osberg, P. H., ed., Geology of east-central and north-central Maine: Orono, Univ. of Maine, p. iii-x.

-----, 1975, Recumbent folding in New England and the plate tectonic model: Abstracts with programs, Geol. Soc. Am., v. 7, p. 102-103.

84

-----, 1978, A plate tectonic model based on the geology of east-central Maine: Abstracts with programs, Geol. Soc. Am., v. 10, p. 79.

-----, and Guidotti, C. V., 1974, The geology of the Camden-Rockland area: In Osberg, P. H., ed., Guidebook for Field Trips in East-central and North-central Maine: Univ. of Maine, Orono, p. 48-60.

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Stewart, D. B., and Wones, D. R., 1974, Bedrock geology of the Penobscot Bay region: In Osberg, P. H., ed., Geology of east-central and north-central Maine: Univ. of Maine, Orono, p. 223-239.

Storre, B., and Nitsch, K., 1972, Die reaktion 2Zoisite ~ 1C02 = 3Anorthite + lCalcit + 1H20: Contr. Min. Petrol., v. 35, p. 1-10.

Sw$,eney, J. F., 1972, Subsurface distribution of granitic rocks, ·. south-central Maine: GSA Bull., v. 87, p. 241-249.

Thompson, A. B., 1975, Cale-silicate diffusion zones between marble and pelitic schist: Jour. Pet., v. 16, p. 314-346.

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. p. 857-874.

------, and Hewitt, D. A., 1973, 'Mobile' components in the formation of calc-silicate bands, Amer. Min., v. 58, p. 991-997.

Wanes, D. R.~ 1976, Granitic intrusives of the Penobscot Bay region, Maine.and their structural setting: Field guide to the geology and plutonic rocksof southwest New Brunswick.and .Pen-obscot Bay area, Maine, IGCP Caledonides Ordeen, Canadian Study Group, v. · 1, p. 40-69.

---'----, and Stewart, D. B.; 1976, Middle paleozoic regional right lateral. strike slip faults in central coastal Maine: Abstracts with programs, Geol. Soc. Amer., v. 8, p. 304.

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APPENDIX I OBSERVED MINERAL ASSEMBLAGES

Abbreviations Used In Assemblage Table

Act - Actinolite

And - Andalusite

Bio - Biotite

Cal - Calcite

Chl - Chlorite

Cord - Cordierite

Dio - Diopside

Kspar - Potassium feldspar

Mus - Muscovite

Op - Opaques

Flag - Plagioclase

Po - Pyrrhotite

Sph - Sphene

Zo - Zoisite

86

87

Mineral Assemblages in Samples of the Penobscot Formation

Sample II ~ Muse Bio Cord And Kspar Plag Po Chl

ELA 2a A re M A M s EI.f\ 2b A Ac Ms A M M r ELA 2c A Ms M s M Mr ELA 2d A Mc M M M M M ELA 2e A Mc M M M s M ELA 2f A Mc Ms M M A ELA 2g ELA 2h A Mc s s s d ELA 3 M M M Aa M A ELA 4 A M A M A ELA 5 t A M M M s M

ELA 6 s A M Mp M s A ELA 7 M A M Ap M s A ELA 8 g M A M Ap Mp s Mb

ELA 13b g M A A Ap s M

Approximate Limits

A - Abundant 20% M - Moderate 5-20% s - Sparse 5%

a - pseudomorphed b - rims pyrite c - sytnplectitic d - contains chlorit.e + sphene veins e - sparse corundum with muscovite rims g - contains trace graphite p - porphyroblastic r - retrograde $ - sagenitic biotite t - contains trace tourmaline

88

Mtneral Assemblages in Sam:eles from the Bucksport Fomation Orono Quadrangle - MaE la

(

Sample fl gg_ Bio Cal Act Dio Zo Plag Ksp Sph Op Other

OND 2a A A M x Chl-x,t OND 2b A A M Mp Chl-r OND 2c A A x M x. Chl-x OND 2d A A m,n,t OND 2e, 1 A A M A M A s s Si Chl-r,a OND 2£ A A x M s Chl-r OND 2g, 1 A A M s s ? So Si Chl-Sr,a OND 2h A s M A Ax A ? So Si OND 2i, b A A Sx Sx s Sp OND 2j' 1 M M M M M M M Tr Sp OND 2k OND 4, l.A A M x M ? x Sp OND 5, d A A M Mp t,a OND 6 OND 7, b A s s Mp

A - Abundant M - Moderate s = Sparse

a - trace apatite b - coarse quartz veins c - zoisite in whitish veins, concordant d - contains bed of extremely fine grained muscovite + biotite i - ilmenite 1 - layered or zoned calc-silicate bands m - abundant muscovite n - moderate andalusite 0 -· rims ilmenite p - pyrite r· - retrograde Tr - trace t - trace tourmaline x - in crosscutting veins

89

Mineral Assemblages in Samples from the Bucksport Formation Orland Quadrangle - Map lb Sample fl Qtz Bio Cal Act Dio Zo Plag Ksp Sph Op Other -- --ORB 21 A A M Sp ORB 2la, 1 A s s A Mc A s So Si ORB 101-1 A A s M Sp 101-2 A Mx Mx M s Si t,a 101-3, d A A M Mus-Ms, t 101-4 A A M Sp Chl-r,t 101-5 A A M Sp Chl-r,t 101-6 A A M Sp Mus-Ss,t 101-7 A s s M Sr Sp Chl-Mr 101-8 101-9, 1 A A s s s s M Tr s Sp,i a 101-10 M s s M M M s s Si 101-11 A A M Sp Chl-r,t 101-12 A M M M Tr s Si,p a 101-13,1 M A s Sp Mus-M llla, d A s Mp Mus-M lllb A M s M Tr Si,p Chl-Tr ORB 24 A M M M M Tr Si t ORB 22 A M A M Si ORB 9a A s M M Si Chl-M

Mus-S ORB 9b M s Sp Mus-A ORB 1 A M M Si Chl-S A - abundant a - trace apatite M - moderate c - zoisite in whitish veins, concordant s - sparse d - cut by numerous quartz veins

i - ilmenite 1 - layered or zoned calc-silicate bands 0 - rims ilmenite p - pyrite r - retrograde Tr - trace s - symplectite t - trace tourmaline x - in cross cutting veins

90

Mineral Assemblages in Samples from the Bucksport.Formation Orland Quadrangle .~- Map le

Sample II Qtz Bio Cal Act Dia Zo Plag Ksp Sph Op Other

ORC 20, b A s M M s M s So Si,p ORC 20-2 A M M ? Si,p t ORC 20-3 A M s M M s Si t ORC 23 A M s M M ? Sp ORC 24 ORC 25 A s M M Si Mus-S ORC 27 A M M M M s Si t ORC 28 ORC 29 Ad s M M ? So Si,p Chl-r,t ORC 30 A M M M Si,p a ORC 31 Ad A M Si,p Mus-S,t ORC 32 A M s M Si,p t

A - abundant M - moderate s - sparse

a - trace. apatite b cut by veins of qtz + plag + calcite + ?prehnite d - cut by numerous quartz veins i - ilmenite 0 - riws ilmenite p - pyrite r - retrograde t - trace tourmaline

APP

END

IX II

MO

DAL

ANAL

YSIS

OF

BUCK

SPOR

T FO

RMAT

ION

(100

0 PT

S).

ORB

SN

ORA

~2

ORA

2lb

ORA

24

ONC

113b

O

RA

9a

OR

B 10

1-·1

0 ----

----

Qua

rtz

20. 7

1 19

.2

21.3

32

.9

29.2

22

.4

9.6

Pla

gio

clas

e .

29. 5

21

.4

31. 9

15

.3

12.0

1

9.l

36

.5

Cal

cite

34

.3

41.9

5.

0 10

.0

24.9

23

.0

1.6

Ch

lori

te

8.5

7.4

6.5

Mus

covi

te

5.8

5.1

25.7

B

ioti

te

16.5

21

. 8

19.5

2.

0 T

r A

ctin

oli

te

19.6

3L

f. 3

Dio

p sid

e 35

.0

14 ..

1

Sphe

ne

1. 7

3.

4 \D

!-

-' E

pido

te

4.8

Opa

ques

1

.1

0.9

0.2

0.

Lt 1

.8

1.1

0.

3 A

pati

te

Tr

Tou

rmal

ine

0.1

0.

3 K

-fel

df?p

ar

Tr

Tr

?

APPENDIX III ANALYSES OF MINERALS BIOTITES

Si02 Al203 Na20 cao :<:o Ti02 !'!nO FeO MgO H20 SUM

:i<;LA 2a

36 .. 09 21 .. 07

.. 23 ,. 0 5

9.42 2- 26

19 .. 56 7 .. 24 3. 99

100 .. 34

s i 5 .. 42 Al .2 .. 59 Sum Tet 8.00

Al :e '.'L; Mn 'I' i t11-M2

Ca Na K sum .~

1. 1 ~ 2.45 1 .. 6 2

• 06 • 26

5.52

• 01 • 07

1.. 8(} 1,. 38

Penobscot Formation

ELA 13b

35.68 21 .. 86

• 23 .. 12

7.20 2 .. 27

• 19 2 4 .. 14

5,.29 3 .. 99

100 .. 97

5 .. 35 2 .. 65 8 .. 00

1. 22 3. 0 3 1 .• 12 "02 .. 2E

5 .. 71

.02

.. 07 1 .. 38 1 .. 46

ELA 8

33.84 20.55

.. 13 .. 02

8 .. 05 1. 77

• 04 22 .. 90

8. 64 3"" 92

99.86

92

5 .. 17 2 .. 83 8. 0 I)

" 8 7

1.97 • c 1 .. 20

5 .. 97

.JO .04

1. 57 1. 61

ELA 7

34.05 22.66

• 2 1 .os

8. 19 2 .. 28

• 1 0 23 .. 20

7 .. 92 4 .. .J4

102.70

2 .. 9 s 8 ... -JI)

1. 0 1 2 .. 3 8 1.. 75

.. J 1

.25 5 • 9 ('

.. 0 1

.06 1 .. s 5 1 .. 6 2

Si02 Al203 Na20 cao K20 Ti02 t1nO FeO :'!gO H20 Su in

Si Al Su~ Tet

Al :F'e Mg Mn 'i'. ~ ].

:i1~:--:2

Ca ~id

ORA 21a

3g_ 67 16. 41

.. 96 .. 76

8 ... 35 3.92

.. 09 18. 94 8. 18 4. 07

101,. 35

5.84 2. 16 8. 00

"5g 2 .. 33 1.80

• 01 .43

5. 26

.. 12 • 27

1. 57 1. 96

93

BIOTITES

Bucksport Formation

ORC 13

36 .. 64 19 .. 04

• 14 .03

9 .. 18 1. 18

• 15 16. 96 11. 81 3.99

99 .. 12

5.50 2 .. 50 8 .. 00

.86 2 .. 13 2.64

.. 02 • 13

5. 78

.01

.04 1. 7 6 1 .. 80

ORA 21

38 .. 72 15" 21

• 21 .08

9.26 2. 38

.20 17 .. 24 12.70 4.02

10 o .. 0 2

5.77 2.23 8.00

• :.+4 2 .. 15 2 .. 82 .03 .27

s .. 70

• 01 .C6

1 .. 7 6 1 .. 83

OBC 27

37.16 17 .. 82

.. 12

.. 08 8 .. 69 2. 11 .02

17"' 33 12.26

4 .. J 2 99 .. 61

5 ... 54 2 .. 46 8.JO

.67 2'" 16 2.73

.. \) 0 • 2 4

:: •• 3 0

• J 1 .. ·J4

1 .. 6 5 1 .. 7 0

Si02 Al20 3 Na20 cao K20 Ti02 MnO FeO L1g0 H20 Sum

Si Al Sum Tet

Al Fe Mg Mn 'l' . J. 1. M:1-M2

Ca Na K Sum A

ORA 24

36. 78 16. 9 2

... 05 • 06

9. 25 2.00

• 11 18 .. 11 12. 65

3 .. 99 99.92

5. 52 2.48 8.00

• 51 2 .. 27 2.83

a 01 • 23

5.85

• 01 • 02

1. 77 1. 80

94

EIOTITES

Bucksport Formation

OND 111b CRC 23

37.35 17.42

.07 • l 1

8.72 3. 18 .17

17.61 11. 4 2 4.03

100.08

5.56 2. 46 8" ()I)

• 6 1 2. 19 2 ... 53

.. 02

.36 5. 71

.02 .02

1. 6 5 l. 6 9

37.23 , 8. 43

• (15 .20

8'9 52 2.07 .12

17. 52 11,,, 8 4

U,.04 no. 02

5. 52 2 .. 48 8. 00

"'75 2. 17 2. 62 .02 .• 2.3

5.79

.03

.. 0 1 1 .. 6 1 1. 6 6

ORC 20- 3

37. 27 17.69

.05 .06

9.34 1. 77

.. 14 16.99 12 .. 09 4.00

99 .. 40

s .. 5 8 2 .. 4 2 8 ... 00

.70 2 .. 13 2.70

.20 5 .. 75

• J 1 .02

1 .. 7 8 1 .. 81

95

DIO!?SIDES

OND 2e OND 2e ORA 21a 0 F: A 21a ORA 21b 1 2 1 2 2

Si02 51 .. 31 51.42 51. 19 51.74 . 52. 07 Al203 • 41 .62 1 .. 29 1.65 .. 19 Na20 • 11 .13 .. 22 • 1 3 .. 13 Cao 23 .. 28 23 .. 97 22.79 21. 28 23.91 K2C • 03 .02 • 02 .. 05 • 00 Ti02 • 11 .13 .37 • 06 .07 MnO • 57 .so ""'61 .. 57 • 76 FeO 1 ~- 78 13.70 13.25 14.76 14. 67 MgO 9. 37 9.61 9.96 10. 08 8. 54 Sum 99 ... 97 100 .. 10 99.70 100. 32 100. 31+

c: • ~l. 1. 98 1. 9 8 1. 97 1.97 2.00 Al • 02 .02 .03 .03 • 00 Sum :'et 2. 00 2.00 2. 00 2 .. 00 2.JJ

Ca 0'" • J 0 .. 99 .. 94 .37 • 99

Na .01 .. o 1 .02 .. J 1 • 0 1 K • 00 .oo .. 00 .oo ·• 00 Mn • 02. .02 .02 • i) 2 .03 Sum :12 .. 99 1. 02 .. 98 • '3 0 1 .. 0 3

Al .. 00 .. 00 '"02 .. •JS • 0 1 Fe • 48 .• 44 .43 .47 .. 47 ~g • 54 .55 .57 • 57 • 49 Sum M1 1 .. 02 .99 1.02 1. 09 .. 97

96

CORDIEFITES

ELA 13b ELA 8 ELA 7

Si02 47 .. 85 49.29 4 7.10 A 1203 33 .. 02 33 ... 31 34 .. 59 Na20 • 39 • 35 .58 cao • 02 .01 .. 00 K20 ,. 00 .oo .. 00 Ti02 .03 .. 0 3 .04 ~lnO • 61 .. 08 .. 06 FeO 12.74 10 .. 59 11.30 MgO 5 .. 15 6. 46 5. 88 Sum 99.81 100.12 99 .. 55

Si 4.97 5 .. 03 4 .. 87 Al 3 .. 03 2 .. 97 3. 13 Sum I'et .3 .. 00 8.00 8.00

Al 1. 01 1. 0 3 1. c 8 Fe 1. 11 .. 90 .98 Mg • 80 .98 • 9 1 Mn • 05 .01 • 01 ~~a • 08 .07 •• 12 Sum 3.05 3. ') 0 3. oe

Si02 Al203 Na20 cao K20 Ti02 MnO Fe203 .MgO H20 sum

Si Al Sum ~et

Al F e-.+-.J Sum

an Ti Na Ca K 11 q S nm

ORA 2 la

39 .. 12 31. 31

.02 23. 97

.02

.. 03

.. 02 2.75

• 10 1. 9 5

99. 29

3" 0 1 • co

3.01

2. 84 - 16

3 .. 00

.. 00 • 00 • 00

1 .. 97 • 00 • 01

1. 99

ORC 13

38. 93 29.20

.01 23. 67

.03 • 15 .20

4 .. 95 "'15

1 .. 9 3 99 .. 22

3. 02 .00

3 .. 02

2. 67 .29

2. 83

• 0 1 • 0 1 .oo

1 .. 97 .oo .02

2. 0 l

97

ZOISITES

OF.A 211:

37. 77 31 .. 95

.02 23.94

.01

.. 05 • 10

1. 69 •• 07

1.92 97. 52

2.95 • 05

3 .. 00

2 .. 90 "'10

3,. 0 0

.01

.oo - 00

2.01 • 0 !) • 0 1

2 .. 03

OND 2e 1

39.53 31.99

• 28 23 .• 6 8

.06

.01 .• (} 5

2.24 .. 11

1.97 99 .. 92

J.01 11 00

3.01

2 .. 87 .. 13

3.00

.. 00

.oo

.04 1 .. 9 3

• J 1

OND 2e 2

39. 04 30.92

.03 23. 58

• 37 • 02 • 12

4. 27 • 09

1. 9 6 100.40

2. 99 .. 01

3 .. 00

2. 78 • 25

3.03

• 0 1 ~ 00 "00

L 93 .. 04 ... 0 1

1. g9

Si02 Al203 FeO MgO ti no Ti02 cao Na20 K20 Sum

Si Al Sum Tet

Fe Mg N1+M3

Al 'T' • . l. Fe..,+-..J 11 g Fe..,+-, 2 M2

Fe-,+ .,2 Mn Ca M4

Ca Na K Sum A

ORA 210 2

so .. 97 2. 54

18.06 11.92

• 1+0 n 20

12 .. 10 • 33 • 12

95. 6:+

7. 65 • 35

8. Q,J

1. 23 l. 77 3. 00

.. 10 • 02 • 37 .. 83 • 6 2

2.00

.. 05 • 05

1. 9 !J 2.00

• 05 • 10 • 02 • 17

98

AM PHI BOLES

OEA 21b 3

50.54 4. 69

19.20 11. 0 6

.. 43 • 18

11. 66 • 34 .16

98 .. 26

7. 48 .52

8 ... 00

1 .. 21 1 .. 79 3. i) 0

• 29 402 .. 59 .65 .44

2. 00

.. 13

.05 1 .. 8 2 2. 00

.03 • 10 .03 • 16

ORC 27 1

50 .. 7 3 4 .. 98

13. 8 1 14. ~6

.. 29 .26

11 .. 97 .. 53 .. 05

97.0S

7 .. 41 .. 59

8. 00

"fi 8 2. 3 2 3 .. 00

.27 .• 03 .. 63 .83

2.00

.. 14

.04 1. 8 3 2 .. 00

.05

.. 15

.01 • 21

ORC 20-3 ORA 24 2 1

53.06 3 .. 44

12.91 14.91

.. 29 .. 23

11 • 7 9 .. 28 .. 13

97 .. 04

7 .. 6 9 • 31

8.00

.77 2. 23 3 .. 00

• 27 • "0 3 .. 38 .99 .. 34

2.0J

.. 08

.. () 4 1. 3 3 2.00

.oc • () 2 .02 .. 04

52. 10 3.£2

16. 61 13.38

"2 9 • 31

12. 16 • 27 • 09

98 .. 83

7 .. 56 .44

8 .. 00

• g 8 2 .. 02 3.00

• 18 "' I) 3 , 48 • 8 8 "'43

2.00

• 12 .04

1. 3 4 2.00

.. 05

.. 08

.• 0 2 u 15

99

AMP HI BOLES

ORA 24 OND 111 b OND 111 b OBA 21a ORC 23 2 1 2 1

SiC2 53 .. 21 55. 04 54. 96 SC.84 51 .. 46 Al203 3. 44 2. 67 3. 01 4 .. 04 7 .. 25 FeO 12. 51 10.86 1l • .36 17.61 13. 31 MgO 15. 58 16. 71 16. 47 12. 20 13 .. 0 1 ~no • 26 - 49 .. 49 .36 .. 19 Ti02 • 07 .. 23 .26 • 29 • 43 cao 12 .. 19 12.32 11. 91 12.<+4 11. 99 Na20 .. 33 .. 25 .. 28 "36 .. 50 K20 .. 16 • 06 • Cl 6 .24 • 18 Sum 97.75 98 .. 63 98.80 98.38 98.32

Si 7. 65 . 7 .. 76 7. 7 5 7 .. 48 7. 37 ;..1 .35 .;. 24 .. 25 .52 .. 63 Sum 'Tet 8.00 8 .. 00 R.OQ 8.00 8.00

Fe-,+..,2 - 76 .71 .63 1 • 13 .89 Mg 2 .. 24 2. 29 2. 3 7 1.37 2. 11 ~1+[13 3. 00 3 .. 00 3.00 3 .. 00 3. 00

.~l .. 23 .21 .22 • 18 • 60 m' L 1. .. 01 .02 ~03 • 03 ~ 05 Fe..,+-.3 • 2'3 • 16 • 35 .25 - 40 Mg 1. 10 1.23 1.09 .81 .. 6 7 Fe..,+-.2 • 38 .38 a29 .49 • 28 Sur:i 1'12 2 .. 00 2.00 2.00 2 .. 00 2.00

Fe-.+...,2 • 08 .03 .07 .06 .02 Mn • 03 .06 .06 .. J4 • 0:: Ca 1. 88 1. 8 6 1... 80 1. 90 1, 34 Sum M4 2.00 2 .. 00 2. 0 0 2. :)0 2. OJ

Ca • 00 .oo .. 00 .OS .. 00 Na • 08 O" .. ~ • 0 1 .. 10 • 02 K .03 • 0 1 • 0 1 • 05 .03 Sum A • 11 .. 03 •· .02 • 15 .05

100

AM'.?HIBOLES

ORC 23 ORC 23 OND 2e OND 2e 2 1 1 2

Si02 l'1. 80 52 .. 25 51.. 74 50 .. 32 Al203 9 .. 99 5.24 3. f. 7 3.78 :'eO 14 .. 66 13 .. 05 16 .. 24 15.17 ~go 11.75 14 .. 04 12. 38 12 .. 89 11n0 .. 25 • 26 .34 .. 29 Ti02 .53 • 34 .39 • 36 cao 11. 8 5 11. 9 3 11. 8 2 11 ... 76 Na20 • 96 .29 .. 52 .47 K20 ' 17 • 13 .• 33 "'28 Sum 97 .. 96 97.53 97.43 9F ... 32

Si 6. q1 7,. 53 7 .. 62 7 .. 51 Al 1- OJ • 4 7 .. 38 .. 49 Sum ::",~·

~ - L. 8 .. 00 8,. r)O 8.JO 3,.:)0

Fe-.+-.2 • 88 .92 1. 16 .99 ~g 2. 12 2 .. 08 1 .. 84 2.01 111+1'13 3. 00 3 .. 00 3 .. 00 3.00

Al .. 6.3 .43 .25 • l8 Ti • 06 .04 .. 04 .04 Fe,+-.3 ,._65 • 18 .27 '• 50 ~g 0 43 .. 94 .88 • 8 f. .Fe-.+-.2 .. 18 .. 4 2 - 56 4 ": . ... Sum ~12 2. 00 2.00 2 .. 00 2.00

Na .04 .07 .08 .. J 0 fe-.+-.2 • 08 .05 .01 • 10 Mn .. () 3 .03 .. o.:+ .04 Ca 1. 8 5 1. 8 4 1.86 1. 8 (i Su rn "14 2.00 2. 00 2 .. 0 0 2.00

Ca • 00 • 00 .. OG .02 Na '"24 .. 01 .07 • 14 :\ .. 0 3 • 02 • 06 oc " ~

Sum A. .. 27 .03 .13 • 21

101

PLAGIOCLASES Bucksport :rorr.iation

ORB 1 OF:A 22 ORA 22 ORA 24 ORA 24

Si02 68.65 59.24 6 7. 23 SE.69 68.14 Al203 19 .. 76 25. 72 2 o. 11 26 .. 99 19. 48 Na20 11 .. 74 7.77 1o.99 6 .. 27 12.01 cao .09 6. 98 .79 9.29 .• 07 K20 ,. 02 .05 • 04 .25 - 05 Ti02 • 00 .. 00 "00 .. 04 • 01 M. no .oo .. 05 .05 .. 00 • 00 FeO • 04 • 10 .04 .19 • 17 MgO .03 .03 .. 02 • 08 .. 05 Sum 100.33 99 .. 94 S9.27 99 .. 80 99.98

An • 42 33 .. 17 3 .. 82 Ll 5 .. 12 .. 32 Ab 99.58 66.83 96 .. 18 54 ... 98 99. 68 Or • 11 .. 28 .23 1 .. 4 2 • 27

ONQ 2e OND 2E> ODA 21b OPC 27 ORA 21 i\

Si02 57. 1 u 45 .. 59 43.80 62 .. 45 56.75 Al203 26. AU 3 4 .. 32 37 .. 44 24.28 28. 13 ~a20 6. 61 1.09 .75 f.47 6. 15 Ca~O 8 .. 51 18 ... 0 8 18 .. 35 6 .. 50 9.53 i\20 1 ,-• • :J .. 03 .. 02 .. '.)8 - 19 Ti02 .02 .02 .. 0 4 .. )0 , 01 '.1n0 • 0 1 "'00 .. 00 • 01 .03 FeO • 06 .os " 10 • ·)0 .05 £1 go • 0 3 .. 05 .05 • ·')6 • 10 Sum 99.37 99.23 100.55 99.35 100.94

An 41. 57 9 o. 16 9 J,. 11 35.7C 46. 13 Ab 58. 43 9. 84 6. 89 64 .. 30 53.87 Cr • 86 .. 23 " 12 .. 5 2 1. 08

Si02 Al203 Na20 cao K20 Ti02 MnO FeO MgO Sum

An Ab 0 :r

Si02 .~ 1203 Na20 cao K20 7i02 MnO FeO MgO Sum

An Ab Or

ORC 13

SA .. 76 27 .. 92

6 .. 74 8.62

,. 1 t) • 04 .. 04 • 16 .09

·102 .. 1n

'~1 .. 41 58. 59

• 57

ELA 8

69. 02 2tJ. 0 1 7.83 2 .. 40 1. 27

• 02 .oo • 18 • 12

99. 79

14.43 85.52

8.63

102

PLAGIOCL;.SES Bucksport Formation

OBA 21

60.23 25.53

7 .. 1+ 7 6. 60 .07 .oo .00 .02 ,. 0 3

99.95

3 2. 81 67. 19

.41

OB3 101a

5 6 .. 7 4 28.25

6 .. 35 9. 6 2

.. 12

.02

.oo • 08 .. 07

101.25

4 5. 26 5 4,. 07

.67

PLAGIOCLASES Penobscot Formation

ELA 13b

65.13 22. 89 12.10

• 59 .03 ... 01 .. c 0 .. 13 .oo

101 .. 94

2. 6 2 97.22

Q 16

Si02 :\1201 Na20 CaO K20 Ti02 MnO FeO MgC H20 Sum

Si Al Sum '!'et

Fe Mg Sum

Ca Na K Sum A

ELA 2a

43.98 38. 82

.68

.02 10.06

• 51 • 01 • 88 • 88

4 .. 53 100 .. 37

s .. 81 2 .. 19 d .. 00

3. 8 5 • 05 .. 1 '.) .. 17

4 .. 18

• 17 1. 7 0 1. 87

103

MUSCOVITES

Penobscot Formation

EL& 7

4f.46 38.95

.59

.. 00 9. 62

.. 49

.oo

.65

.67 4. 65

102.08

5. 99. 2.01 8.00

3 .. 90 .. 0 5 .07 .. 13

4. 14

• 15 1. 58 1.73

ELA 13b

49.13 36.70

1. 26 • 28

7. 5 2 .45 .oo • 91 .. 28

4. 6 7 101.20

6 .. 31 1.69 8.00

3 .. 86 • 0 Ll • 10 .05

4.06

.04 • 31

1. 2 3 1 .. 58

104

MUSCOVITES

Buckspol:'t Formation

ORB 1 ORB 1 ORC 109a ORC 109a ORC 109a 2 3 1 2 3

Si02 45.76 49 .. 63 46.61 48 .. 73 \ 47. 34 Al203 34. 25 28 .. 15 35.93 31..82 32. 63 Na20 .45 .28 .44 .19 • 26 cao .. 05 .03 .. 01 Q'J .. - .. 0 3 K20 9.32 9. 85 9 .. 43 1o .. 27 1 o .. 15 Ti02 • 81 .. 54 • 91 .• 4 1 1. 17 :'lnO • 00 ,02 - 0 lt .• 0 3 .OS FeO 2:so 4 .. 16 1. 15 1.76 2. 36 !'1g0 2.20 J .. 55 .ES 2. 18 1,. 2 8 H20 4. 51 4.50 4.54 4 .. 52 4. 49 Sum 100. 41 100.71 J 9 .. 71 99. 93 99.76

Si 6. 08 6.61 6.16 f.46 f .. 32 Al 1.92 1. 39 1 .. 84 1 .. 5 4 1.68 Sum 'let 8.00 8.00 8.00 8.JO 8.00

Jl. l 3 .. 45 3 .. 03 J .. 75 3 .. 44 3. !~5 'Ii • 08 .OS .09 .. J Li • 12 Mn .. 01 FP. • 29 .46 .. 13 .• 20 .26 Mg .44 .71 • 1 3 .. ~ 3 ,., ,.

-· .:...0 Sun 4. 24 4. 25 u .. 10 4. 11 4.C9

Ca • 0 1 N"' . ~ .. 12 .. 07 .. 11 .. 05 .. 07 :-\ 1.67 1. 6 7 1.59 1.. 7 4 1. 7 3 Sum A 1. 79 1 .. 75 1. 70 1 .. 79 1. 80

10,5

CHLORITES

OND 111b OND 111 b OFA 24 0£.C 27

Si02 26 .. 89 23. 15 28 .. 15 29 .. 2 5 Al203 22.20 27 .. 40 18. 30 20.92 Na20 .• 00 "0 3 .07 • 21 cao .05 • 18 .20 • 11 t\20 • 05 ' .07 .48 • 26 Ti02 .06 • 11 .17 .18 MnO .. 43 .. 27 .21 .13 FeO 19 .. 64 28 .. 21 21.40 22.55 MgO 18. 50 8.98 16.01 17.21 H20 1l.77 11. 33 11.31 12.06 Sum 99. 59 99 .. 7 3 96 .. 66 102~38

Si s.~7 4.90 E.04 5 .. s 1 Al 2 .• 53 3. 10 1. 9 6 2.19 Sum ret 8. 00 8.00 8.00 8 •• JO

Al 2.80 3.73 2 .. 61 2. 7 1 Fe 3. 34 4. 99 3. 79 "=! ., a:::

-· .• .I

Mg 5 .. 61 2. 83 5.06 5.10 "'. • 0 l .02 .03 0., J. 1. .. J

"!n • 07 .OS .04 .02 Na .01 .03 • 08 Ca .• 01 .04 .05 .. 0 2 K • c 1 0"' . ... • 1 J .07 Snr.l 11.85 11 .. 6 y 11.73 1L78

106

CHLO RITES

ORC 109a ORC 109a OFB 1 , 2

Si02 25.92 27. 01 2E.20 Al20J 21. 17 19 .. 48 23.84 Na20 .. 05 .05 .39 cao • 00 .19 .07 r.:20 "'00 .oo .,.33 Ti02 .oo .oo • 1 1 MnO .oo .oo .. 19 F'eO 24 .. 99 23.98 21.58 MgO 16 .. f), 16 .. 38 15 .. 7 4 H20 11. 55 11.46 11. 73 Sum 100 .• 20 99.05 100. 1f,

Si 5. 38 5. 65 5.35 Al 2.62 2.35 2. 65 Sum Tet 8. co 8. 00 8. 00

Al ' 2.55 2.45 3 .. oq Fe 4 .. 34 4.1S 3. 69 Mg s. 14 5.26 4. 79 Ti -"""\ 11 02 ~n .. 0 3 Na .02 .. 02 • 15 Ca .04 .02 K • 09 Snm 12. 0 :.+ 11 .. 9 t 11 .. 8 8

107

PYFRHOTITES Penobscot Fonna t:ion

ELA 7 ELA 8 ELA .13b Fe 61. 03 61. 10 60. 69 Ni • 19 • 16 • 14 s 38 .. 78 38. 66 38. 6.6 Sum 100. 00 99. 92 99.49

Xpo • 95 .95 .. qs

IL~1ENI~E SP HE NE ORC 1J ELA 7 ORA 21b

Si02 • 12 .08 28 .. 91 Al20 3 • 42 .. 19 4 ~ 18 Na20 s 13 .08 .04 cao • 37 .08 27. 2 5 K20 • 05 .. 08 Qt:; ... '

Ti02 54. 48 52. 84 36.05 r1n0 ~- 20 .72 .. 04 FPO 40.70 47.60 .. 45 MgO • 39 • 28 .. 2-J Sum 100 .. 86 101.95 97.25

108

CALCITES Bucksport .Formation

ORA 22 ORC 27 () p. B 1

Si02 1 '' • 4 .oo • 0 1 Al203 .. 03 .oo - 01 \ Na20 - 02 .07 .. 20 cao so. 56 53.15 53. 56 K20 .02 .oo .03 Ti02 • 00 .01 .03 r-!nO • 59 • 26 .39 FeO l. 14 .46 • 88 MgO • 92 .. 77 .75 C02 44. 00 4U.- 00 4 4 .. 00 Sum 9T.43 98.72 99.87

Ca - 95 • 97 .; 96 r1g .02 .02 .• 02 Fe .02 .01 • 01 Mn • a 1 .01

l?OT ASSI Ur' FELDSPAR

.Eli\ 2a ORA 21a

Si02 65.46 65. 11 Al203 17. 82 18. 52 Na20 • 61 • 61 cao • 00 .. 03 K20 16. 02 15. 99 Ti02 .oo .05 '.1nO • 00 .. 00 FeO • 00 .oo MgO • 02 .06 Sum 99 .. 93 100 .. 37

An 0'" ... v .. 15 Ab 5 .. 47 5. 47 Or 94 .. 53 94 .. 38

The vita has been removed from the scanned document

CONTACT METAMORPHISM OF THE LUCERNE PLUTON, HANCOCK COUNTY, MAINE

by

Steven W. Novak

(ABSTRACT)

The Lucerne pluton intrudes rocks of the Penobscot formation

Ordovician-Silurian (?)), a quartz-rich sulfidic pelite that contains

muscovite, biotite, cordierite, andalusite, plagioclase, pyrrhotite

and graphite outside the thermal aureole; and the Bucksport for-

mation (=Vassalboro, Silvian-Devonian (?)), a calcareous, quartzo-

feldspathic pelite that contains chlorite, biotite, celadonitic

muscovite, albite, and ilmenite outside the Lucerne aureole. Within

the aureole, the Penobscot formation contains K-feldspar plus

andalusite as the result of muscovite reaction with quartz. Corundum

occurs at the immediate contact of the granite from the. reaction of

the remaining muscovite. The Bucksport formation is recrystallized

within the aureole to a purple and green gneiss. The gneissic

banding is not present in the low grade calcareous rocks, and

represents the segregation of biotite-rich and calc-silicate.-rich

bands. Vertical or sleepy dipping, the banding parallels both

the regional strike and the intrusive contact, and is probably

the result of both mechanical and chemical effects. The following

sequence of assemblages (+ quartz) is found in the calcareous portions

of the Bucksport formation as the Lucerne contact is approached:

a) chl + bio +muse+ cc+ albite; b) bio +cc+ plag (An25 _33);

c) actinolite +cc+ K-feldspar + plag (An40); d) diopside +

zoisite + sphene +cc+ plag (An85_90). Interbedded pelites contain

· biotite + quartz + plagioclase + pyrite with corundum occurring at

the igneous contact in quartz free beds. The mineral assemblages

in the Lucerne aureole indicate a lithostatic pressure between 1000

and 3000 bars during metamorphism with temperatures between 700°C

and 450°C. Isobaric univariant assemblages in the calc-silicate

beds indicate buffering of H2o/co2 fluids produced by prograde

reactions. H2o rich fluids that produced zoisite were probably

associated with late stage crystallization of the Lucerne.