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are Lrdlcated by coexisting @&ite+quarte
&% er. 1979. fir. 10-2).
&mbi&e- 4 cdntaihs dfscontlnuously zoned
garnets. Relatively uneoned birefringent cores comlst
of 83 rnol percent grossular (gr), 15 mol percent andradite
(an), 1 mol percent spessartine (sp), and no alman-
dine (ai) (table 12). Isotropic rims ate zoned outward
from F ~ ~ ~ '0 ~ 860m33~P11* ~ ~ P ~ " me ~ mre ,
may have formed durlrrg revon me morphism of Peand
Al-rlch carbonate r&. The rims could have
formed during the contact-metamorphic event at the
ertpense of earlier formed Pe- and Mn-ing miner-
&, or the cores and rims may both have formed during
the same event by a discontinuous reaction.
Alternatively, semiquantitative emissionspectroscopy
malysei, of calcsilicates from Table
Mountain suggest that they are enriched in Zn, Sn, W.
I and Cu and may thus have undergone metasomatism
from flukls emanating from the nearby granodiorite
1 pluton and (or) epizonal PelsIc intrusions. However,
the sequence of assemblages 1 through 4 b observed in
( the same order at three separate Wtiss uig. 32), a
result that could be due to thermal metamorphism of
I compositionally distinct layers.
Contact-rnetemorphlc essembhges and taKtures
are observed along the Ptnnell Mountain trall es far as
6 km southwest of the granodiorite pluton mapped in
the northeastern part of the study area (fig. 32).
Because this is too 1 e a contact aureole for such a
srnu pluton, a laFgeryeblc plubn underlying the area
I3 suggested. The small felsic Intrusions may well be
related to such a body.
REFERENCES CITED
Cushing, G. W., Foster, H. L., taird, Jo, end Burack,
A. C., 1982, Deacrlptlon and preliminary Inter-
pretation of folds and faults in a small area In
Circle 6-4 and &5 quedranglea, Alaska, in
Cooncad, W. L., ed., 'lhe United States ~eol*
cal !Survey h Alaska8 AccornpUshments during
1980: U.S. Cgologfcel Survey Circular 844, p.
56-58.
Pnster, H. L., Weber, F. R., Forbes, R. &, and Brabb,
E. E., 1973, Regional geology of the Yukon-
Tanana Upland, M a , & Pitoher, M. G., ed.,
Arctic geology: American miation of P e e
leum Geologists Memoir 19, p. 388-396.
Labotka, T. C., 1981, Petrology of an anddmitetype
reglonal metamorphic terrane, Panamlnt Moun-
talns, C-ornia: Journal of Petrology, v. 22, no.
2, p. 261-296.
Laird, Jo, 1980, Phase equWbria in mafic sohist from
Vermont: Journal of Petrology, v. 21, no. 1, p. 1-
37.
Rice, J. M., 1980, Phsse equMbrL Involving humite
minerals in impure dolomltic limmtonea, part r:
Calculated stability of clinohumlte: Contribu-
tions to Mineralogy and Petrology, v. 71, no. 3, p.
219-235.
Smith, J. V., 1972, Critic& review of synthesP and
occurrenee oi plagiociase feldspars and a
possible phase diegram: Journal of Geology, v.
80, no. 5, p. 505-525.
Winklet, H. G. P., 1979, Petrogmsk of metamorphic
rocks (5th ed.): New York, Springer-Verlag, 348
P-
-
Amphmole eclogite in the C%& m e ,
TnllaM Upland,
Petmgraphic and electron-m icrwrobe analyses
of a sample of mafic schist collected north of Twin
Buttes, Circle A-6 quadrangle, Yukon-Tanana Upland
(area 11, fig. 23; fig. 33), show it to be eclogite near
the boundary of Groups B and C of Coleman and others
(1985). Estimated conditions of metamorphism are
600~*50~~ and 1.35f0.15 GPa. This edogite is an
strike with that reported by Swainbank and Forbes
(1975) from the nearby Pairbank district (Pig. 33).
Pigwe 33.-Eclogite localities in eastern part of
Livengood (A-2) quadrangle and western part of Circle
(A-6) quadrangle.
The sample studied (79AWrl08C, fig. 33) Is lrom
a mafic layer within quarte+white mIca+garnet borne-
what retrograded to chlorite) schist and quartalte.
Where the contact is vtsible, the foliation has the same I
orientation in both the malic and pelltic Layers, which
appear to have been metamorphosed together. The
mafia layer cuts across the foliation and is more
massive in the interior, an observation suggesting that
its protolith was a dike,
In general, the mafic layer is rnedlum grained,
medium green, massive to fouated, containing
rnediummn pyroxene, dark-blue-green amphibole,
reddbh-bmwn garnet porphyroblasts as large as 3 mm
across, quartz, a paleyellow epidote-group mineral,
white mica, and gold+olared sulfides. Similar rocks
mcur as rubble on the adjacent ridges to the west and
east
Pe-aphialy the sample is mmpsed (in
estimated modal percent) ol: garnet (25), clinopyrox-
ene (25), quartz (201, clinoamphibole (lo), elhozoisite
(lo), white mica (LO), rutile (I), and suLtide (trace).
The clinopymxene is colorless and is surrounded and
cut by ccyptocrystalline material that may be sirnil@
to the symplectite described by other workers as an
alteration product of eologftic omphacite. hphlbole
shows colorless to pale-blue-gray pleochrofsm except
in a few places next to garnet, where a colorles to