Klondike Schist

Unit symbol: Pks
Age range Permian (298.9 to 252.2 Ma)
Lithology: Metamorphic
Group name: Klondike Schist, Keevy Peak Formation, and similar rocks (Yukon-Tanana crystalline complex)
Poorly understood assemblage of generally low-grade metamorphosed pelitic and volcanic rocks and minor marble. Primarily exposed in the Eagle quadrangle in Alaska (Szumigala and others, 2002; Dusel-Bacon and others, 2006) and more broadly exposed in the Yukon (Gordey and Ryan, 2005; Beranek and Mortensen, 2011), it consists of gray-green to dark-greenish-black massive greenstone, amygdaloidal pillow basalt and metatuff and associated metachert, quartzite, phyllite, silica-carbonate lenses, and other low-grade metasedimentary rocks. Mortensen (1999) reported that the Klondike Schist yielded mid-Permian protolith ages as determined by U/Pb zircon analysis, and more recent analyses by Beranek and Mortensen (2011) bracket intrusion and metamorphism to between 260 and 252.5 Ma. In the Tanacross quadrangle, quartz-muscovite, quartzite, quartz-muscovite schist, actinolite schist, chert and other fine-grained silicic rocks, phyllite, metagraywacke, and schistose greenstone are also included here (Foster, 1970). On this map, assignment of rocks in the eastern Eagle quadrangle to the Klondike Schist or the Keevy Peak Formation (unit Pzkp) must be considered tentative; Permian (~255 Ma) U/Pb zircon ages, as well as Mississippian and Devonian zircon ages are reported by Dusel-Bacon and others (2006) for the Nasina assemblage, here assigned to the Keevy Peak map unit (unit Pzkp)

Source map information

Source map Foster, H.L., 1976, Geologic map of the Eagle quadrangle, Alaska: U.S. Geological Survey, Miscellaneous Investigations I-922, 1 sheet, scale 1:250,000.
Symbol Pzq
Unit name Quartz-mica schist and greenstone
Description Quartz-mica schist and greenstone. Also includes quartzite, marble, quartz phyllite, phyllite, and quartz-graphite schist, quartz-muscovite schist, chlorite schist, calcareous schist, and greenstone.
Lithology Metamorphic

Correlated geologic units

Label Pks
Description Klondike Schist, assemblage of metamorphosed pelitic/volcanic rocks and minor marble.
Geologic age Permian
Geologic setting Metaigneous and metaseds, low-grade
Lithology Form Importance
Calc-silicate-schist < Schist < Metamorphic Greenschist Major
Mica-schist < Schist < Metamorphic Major
Greenstone < Metaigneous < Metamorphic Greenschist Minor
Marble < Metacarbonate < Metasedimentary < Metamorphic Greenschist Minor
Quartzite < Metaclastic < Metasedimentary < Metamorphic Greenschist Minor