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and 40178 have a bigger crustal signature ana rnus are
more like CAB and CTB. With more geochemical &ts
and some warranted scepticism, the RBE patterns and
trace-elment chemistry of orthoamphibolite of the
Yukon-Tanana Upland, together with more detailed
field mapping of these rocks, may provide valuable
information about the tectonic history of this enig-
matic terrane.
REFERENCES CITED
Aleinfkoff, J. N., DuseL-Bacon, Cynthia, Poster, H. L.,
and Futa, Kiyoto, 1981, Proterozoic zircon from
augen gneiss, Yukon-Tanana Upland, east-central
Alaska: Geology, v. 9, no. 10, p. 469-473.
AIeinikoff, J. N., Foster, H. L., Nokleberg, W. J., and
Dusel-Bacon, Cynthia, 198 5, Isotopic evidence
from detrjtal zircons for Early Proterozoic crus
tal material, east-central Alaska, Cobnrad, W.
L., and Elliott, R L., eds., The United States
Geologfcnl Survey In Alaska-Aecomplishments
during 1981: U.S. Geological Swey Circular
868, p. 43-45.
Arth, J. G., 1981, Rareearth element geochemistry of
the island-an! volcanic rocks of Rabaul and
Telasea, New Britain: Geological Society of
America Bulletin, v. 92, no. 11, p. 858463.
Barth, T. F. W., 1962, Theoretical petrology (2d ed.):
New York, John Wiley, 416 p.
Evens, B. W., and Leake, B. B., 1960, ?he composition
and orldn of the striped amphibolites of Comemafa,
Gelend: ~ournk of ~etrology, v. 1, no. 3,
p. 337-363.
Frey,-F. A., Heskln, M. A., Poeb, 3. A., and Baskin, L
A., 1968, Rare earth abundances in some besic
rocks: Journal of Geophysical Researah, v. 73,
no. 18, p. 6085-6098.
GareIe, M. O., 1978, Criteria for the identifioation of
ancient volcanic arcs: Earth Scfence Reviews, v.
14, no. 2, p. 147-165.
Gottfried, !kvid, Annell, C. S., and Sehwarz, L. J.,
1977, Geochemistry of subsurface basalt from
the deep corehole (Clubhouse Crossroads corehole
1) near Charleston, South Carolina-magma
type and tectonic implications: U.S. Geological
Survey Professional Paper 10284, Q. 91-113.
Hasun, L. A,, Frey, P. A., Schmitt, R. A, and Smith,
R. H., 1966a, Meteoritic, solar, and terrestrial
rare-eerth distributions, & hhrens, L. H., Press,
Prank, Runcorn, S. R., and Urey, K C., eds,
Physics and chemistry of the earth: New York,
Pegamon, p. 167-321.
Haskin, L. A., Wildeman, T. R, Prey, F. A,, Collins, K.
A., Keedy, C. R, and Hesldn, M. k, 1966b, Rare
earths in sediments: Journal of Geophysical
Research, v. 71, no. 24, p. 6091-6105.
Leake, B. E., 1964, The chemical distinction between
ortho- and para-amphibolites: Journal of Petrology,
v. 5, no. 2, p. 238-254.
Masuda, Akimasa, Nakamura, Noboru, and Tanaka,
Tsuyoshi, 19'73, Fine structures of mutually normalized
rare-earth patterns of chondritos: Ceouhimica
et Cmochlmica Acta, V. 37, no. 2, p.
239-248.
Noekolds, S. R., 1954, Average chemical compositions
of -me lmeous rock Geolodcal Society of
America ~ hetln, V. 65, no. 10,g 1007-1032;
Orvllle, P. M., 1969, A mMek for metamorphic differ-
entiation origin of Ulin-layered amphibolftes:
American Journal of Science, v. 267, no. 1, p. 64-
86.
Pearce, J. A., 1975, Basalt geochemistry used to inves-
tigate past tectonic environments on Cyprus:
Tectonophysics, v. 25, no. 1-2, p. 41-67.
Pearce, J. A, and Can, J. R., 1973, Tectonic setting
of basic volcanic rocks determined using trace
element analyses: Earth and Planetary Sdence
Letters, v. 19, no. 2, p. 290-300.
Preto, V. A. G., 1970, Arnphibolites from the Grand
Forks quadrangle of British Columbia, Canada:
Geological Society of America Bulletin, v. 81,
no. 3, p. 763-782.
Shaw, D. M., and Kudo, A. M., 1965, A test of the dis-
criminant function in the amphibolite problem:
Mineralogical Magazine, v. 34, no. 268; p. 423-
435.
Suen, C. J., Frey, F. A., and Malpas, J., 1979, Bay of
lslands ophiolite suite, Newfoundland: Petrologic
and geochemical characteristics with emphasis
on rare earth element geochemistry: Earth and
Planetary Science Letters, v. 45, no. 2, p. 337-
348.
Metamorphi0 -1- of the 'IBhle Martlbh m,
Circleqnadreagle,AZeslca
By~C.WnadqJ~~,BalenL.Paatet,and I
Grant W. Cuahiqg
i
Metamorphic rocks along Me Pinnell Mountain
trail, Circle E M quadrangle, Alaska (area 3, fig. 23;
flg. 321, are part of a complexly deformed terrane of
schlst and quartzite of Paleozoic and (or) Precambrian
age that are typical of much of the western Yukon-
Tanma Upland (Poster and others, 1973). We have
been studying the petrolcgy of these rocks as a regre-
sentative sample of this metamorphic terrene, and this
repart describes typical mlneral assemblages and
presents pmbabIe conditions of metamorphism. A
knowledge of the metarnorphia history may help in
identifying the kind and extent of minerallaation in the
Table Mountain area.
The metamorphic rocks studied are divided into
pefitie schist and quartzite, mnfic schist, and calc-
sUlcate rocks. A northeast-trendhg lineament, dis-
oernible on aerial photographs (fig. 32; CusNng and
others, 19821, appears to separate rocks regionally
metamorphosed to epidote-amphibolite facies (garnet
grade) on the south from contact-metamorphosed
rocks (biotite hornfels) on the north. The contact
me mor him, which is related to a ernall (approx 2-
km e are 3 granodiorfte pluton (fig. 32) has overprinted
regional metamorphism of probable epidote-
amphibolite f acies (gatnet grade). Several small
epizonal felsic intrusions dm crop out north of the
lineament, mostly in the vicinity of Table Mountain
eig. 32).
Pelltic rocks south of the lineament are ptlmar-
Ily composed of quartz~lagioclase+muscovite+chlor-
ite+biotIteIgarnet; the plagioclase is commonly por-
phyroblastic. Coexisting with this epidote-
am phiMLLte-facies assemblage, near the linae ment