Structural geology and tectonics of the paleoproterozoic rocks of the Mount Rushmore Quadangle, Black Hills, Souh Dakota

The Early Proterozoic Matachewan Large Igneous Province: Geochemistry, Petrogenesis, and Implications for Earth Evolution

“…The 2480 ± 6 Ma Blue Draw Metagabbro is an 800 m thick (~6 km outcrop area) layered amphibolite sill (Dahl et al, 2006) which crops out in the Black Hills uplift, South Dakota, west of Nemo township (Fig. 1) (Redden et al, 1990;Hill, 2006 Woo (1952) and Maranate (1979) described the intrusion as a 1 km thick layered sill with serpentinite at the base which grades into hornblendite, plagioclase gabbrodiorite, biotite granodiorite and discontinuous dioritic pegmatite. A series of dominantly NW-SE trending faults have removed the side-wall contacts of the intrusion and have otherwise dismembered the Blue Draw Metagabbro such that slivers of metamorphosed gabbro thought to be correlative with it crop out at several locations throughout the area (Dahl et al, 2006).…”