The Homestake gold mine, an early Proterozoic iron-formation-hosted gold deposit, Lawrence County, South Dakota

Abstract

Jl. Map showing generalized geology of the Black Hills uplift, South Dakota and Wyoming J3 J2. Diagram and graph of annual gold production, ore-ledge discovery, and significant historical events, Homestake mine, Lead, S. Dak. J4 J3. Schematic diagram illustrating stratigraphy of the Homestake mine area J6 J4. Generalized geologic map of the eastern part of the Lead dome of the Black Hills uplift, South Dakota J7 J5. Generalized geologic cross section through 33 Stope, Main Ledge Reference Line, Homestake mine JS J6. Geologic map of 2600 level, Homestake mine, showing significant fold structures and ore ledges J9 J7. Plot of Mg:(Mg+Fe+ 2 ) versus Ca (cation percent) for selected gruneritecummingtonite-series amphiboles from the Homestake mine JlO J8. Jensen cation plot for mafic metavolcanic rocks of the Poorman Formation (Yates unit) and Ellison Formation, Homestake mine J12 J9. AFM diagram for metabasalt samples from the Poorman Formation (Yates unit) and Ellison Formation, Homestake mine J12 JIO. KTP diagram for metabasalt samples from the Poorman Formation (Yates unit) and Ellison Formation, Homestake mine J13 111. Geologic map of 2600 level, Homestake mine, showing upper greenschist-lower amphibolite facies and surface trace of garnet isograd J20 112. ACF diagram for lower amphibolite facies metamorphism of Poorman and Ellison Formations mafic igneous rocks, Homestake mine J21 113. A'KF diagrams for mineral assemblages from the Poorman and Ellison Formations, Homestake mine J21 114. Projected AFM diagrams for upper greenschist facies and lower amphibolite facies mineral assemblages for Homestake Formation, Homestake mine J22 115. Geologic map of 2600 level, Homestake mine, showing D1a structural domains J28 116. Schematic diagram showing D 1 a fold events at Homestake mine J29 117. Generalized geologic map of 2600 level, Homestake mine, showing lower hemisphere, equal-area stereonet with 288 poles to folded foliations of late S1a from the Lead anticline J30 118. Iron-formation fold profile section of the Gentle Annie structure (east limb of the Lead anticline), 2600 level J31 119. Sketches of late F1a (sheath) and early Fib minor folds in Poorman and Ellison Formations in the eastern ledge area of the Lead anticline J33 120. Structural sketches in profile sections of minor folds in latest Dla shear zones, western ledge area on the Poorman anticline J34 121. Generalized geologic map of part of 6800 level, Homestake mine, western ledge area, showing lower hemisphere, equal-area stereonet with 110 poles to transposed late S1a foliation J35 122. Plan view vertical projection of selected horizontal slices of the Caledonia, 9 Ledge, and 17 Ledge ore bodies to a horizontal plane, showing the geometric elements of an ore ledge J37 123. Plan view vertical projection of selected horizontal slices of Main Ledge ore bodies to a horizontal plane J38 124. Plan view vertical projection of selected horizontal slices of 9 Ledge ore bodies to a horizontal plane, showing geometric elements of an ore ledge and the upper greensch...

Creation of a Mixed‐Mode Fracture Network at Mesoscale Through Hydraulic Fracturing and Shear Stimulation

“…Experiment 1 of the EGS Collab Project benefitted from a thorough characterization of prior experiments near the site such as from the kISMET project (Oldenburg et al, 2017). The experiment is embedded in a host rock of carbonate-rich, quartz-bearing phyllite of the upper Poorman formation (Caddey et al, 1991). This metamorphic rock is strongly foliated and as a result has a highly anisotropic mechanical response (Frash et al, 2019;Vigilante et al, 2017).…”

Culture-based analysis of ‘Cave Silver’ biofilms on Rocks in the former Homestake mine in South Dakota, USA

“…The rocks in this region consist of phyllites of the Poorman formation. These phyllites consist mainly of sericite, biotite, graphite, ankerite, and quartz, with pyrrhotite also present (Caddey, 1991). In a zone from 8 to 60 m beyond a flowing diamond drill hole known as "Thiothrix Falls", the site of an astrobiology experiment, areas of thin (less than 1 mm thick) iridescent biofilms frequently occur on the walls and ceilings of the tunnel.…”

Comparison of Biotite Elastic Properties Recovered by Spherical Nanoindentations and Atomistic Simulations — Influence of Nano‐Scale Defects in Phyllosilicates

“…The samples used in this study were schist rocks from the Poorman Formation collected from the Sanford Underground Research Facility (SURF), South Dakota, collected under the kISMET project (Oldenburg et al, 2016(Oldenburg et al, , 2017, same as those used by (Vigilante et al, 2017). The rocks used in this study are characterized as a biotite-quartz-carbonate phyllite to schist (Caddey et al, 1991) and also include chlorite and minor amounts of muscovite and rutile. These schist rocks were chosen because of their low porosity (less than 1%) and the large biotite grains (∼100 μm) in the rock that allows us to probe single crystal properties.…”