Presented by Berger, Byron R..
Authors:
Berger, B. R.,
Goldhaber, M. B.,
Hildenbrand, T.,
Wanty, R. B..
Key words: economic geology, gold, Carlin, model
In Session 160 Economic Geology (Posters) Thursday, 29-Oct-98 PM in Room: Hall-E at 1:30 PM for 240 minutes.
Abstract: Models of Late Eocene-Early Oligocene Carlin-style gold deposits, Nevada, must account for coupling of deformation, heat transfer, and solute transfer in fluid-flow systems at all scales. 50-37 Ma hornblende cooling ages in metamorphic core complexes imply 10+ km extension during the period. Far-field stresses led to NW-SE directed extension. A flat Moho and lack of concurrent basins imply rapid delamination of lower crust to account for required uplift. Traction forces across the brittle-ductile transition would result in motion accommodation in the brittle crust on strike-slip transfer faults between blocks with differing slip rates. Heat flow across the shallowing brittle-ductile transition (=15 km to =7 km), the high heat flow core complexes, and *42-40 Ma magmatism led to complex patterns of free convection of fluids in the brittle crust. With brittle crust stress and strain localized on transfer faults, net fluid flow was to the block boundaries resulting in the linear trends of Carlin-style gold deposits.
Distal from the core complexes to the NW, slower delamination possibly led to the subsidence in which the Tuscarora (*41 Ma) lacustrine basin sediments accumulated. This large reservoir of meteoric waters could have provided recharge along the transfer faults which directed fluids into the large-tonnage Jerritt Canyon, Carlin, and Twin-Creeks-Getchell trends.
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