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Full-Text Articles in Tectonics and Structure
Ar-40/Ar-39 Evidence For Middle Proterozoic (1300-1500 Ma) Slow Cooling Of The Southern Black Hills, South Dakota, Midcontinent, North America: Implications For Early Proterozoic P-T Evolution And Posttectonic Magmatism, Daniel Holm, Peter Dahl, Daniel R. Lux
Ar-40/Ar-39 Evidence For Middle Proterozoic (1300-1500 Ma) Slow Cooling Of The Southern Black Hills, South Dakota, Midcontinent, North America: Implications For Early Proterozoic P-T Evolution And Posttectonic Magmatism, Daniel Holm, Peter Dahl, Daniel R. Lux
Peter Dahl
Ar-40/Ar-39 total gas and plateau dates from muscovite and biotite in the southern Black Hills, South Dakota, provide evidence for a period of Middle Proterozoic slow cooling. Early Proterozoic (1600-1650 Ma) mica dates were obtained from metasedimentary rocks located in a synformal structure between the Harney Peak and Bear Mountain domes and also south of Bear Mountain. Metamorphic rocks from the dome areas and undeformed samples of the similar to 1710 Ma Harney Peak Granite (HPG) yield Middle Proterozoic mica dates (similar to 1270-1500 Ma). Two samples collected between the synform and Bear Mountain dome yield intermediate total gas mica …