Mafic schist and amphibolite

Unit symbol: Pzyms
Age range Devonian or older Paleozoic (541 to 358.9 Ma)
Lithology: Metamorphic
Group name: Gneiss, amphibolite, schist, quartzite, and marble (Yukon-Tanana crystalline complex)
“Green, quartz-chlorite-carbonate schist, commonly having abundant plagioclase porphyroblasts. Associated with amphibolitic schist and minor marble, quartzite, and pelitic schist. Thought to represent metamorphosed mafic pyroclastic rocks interbedded with schists of unit |<yqs” in the Circle quadrangle (Wilson and others, 1998; see also Foster and others, 1983). In the south-central Circle and adjacent Big Delta quadrangle unit varies from greenish-gray actinolitic greenschist to dark green, fine- to coarse-grained, schistose amphibolite of unit |<yqm, which is interlayered or interlaminated with muscovite-feldspar-quartz felsite (Smith and others, 1994). In the southeast Big Delta quadrangle, unit is similarly composed of dark-green, fine- to medium-grained, strongly foliated, hornblende-biotite amphibolite gneiss associated with augen gneiss of unit MDag or interlayered with foliated, medium-grained, equigranular calc-silicate schist and, locally, quartzite of unit |ymi (Day and others, 2007). In the southeastern Eagle quadrangle, unit consists of moderately- to nonfoliated, fine- to medium-grained hornblende metagabbro and metadiabase (Werdon and others, 2001).Unit also contains a green and white, medium- to coarse-grained, slightly- to nonfoliated metaigneous rock that has pseudomorphs after clinopyroxene and plagioclase of fine-grained actinolite, chlorite, epidote, clinozoisite, albite, and (or) sphene (Szumigala and others, 2002)

Source map information

Source map Foster, H.L., Laird, Jo, Keith, T.E.C., Cushing, G.W., and Menzie, D.W., 1983, Preliminary geologic map of the Circle quadrangle, Alaska: U.S. Geological Survey Open-File Report, 83-170-A, scale 1:250,000.
Symbol PzpCm
Unit name Mafic schist
Description Green, chlorite-quartz-carbonate schist, associated with amphibolitic schist and minor marble, quartzite, and pelitic schist.
Lithology Metamorphic

Correlated geologic units

Label PzZms
Description Mafic schist
Geologic age Paleozoic to Devonian
Geologic setting Metamorphic, undivided
Lithology Form Importance
Calc-silicate-schist < Schist < Metamorphic Greenschist Major
Amphibole-schist < Schist < Metamorphic Greenschist Indeterminate, major
Marble < Metacarbonate < Metasedimentary < Metamorphic Greenschist Minor
Quartzite < Metaclastic < Metasedimentary < Metamorphic Greenschist Minor
Quartz-feldspar-schist < Schist < Metamorphic Greenschist Minor