Impact of sedimentary-exhalative hydrothermal systems on marine chemistry and mass extinctions : applications for ore genesis research and mineral exploration

• Main Authors: Emsbo, Poul, Premo, Wayne R, McLaughlin, Patrick I, Neymark, Leonid A, Vandenbroucke, Thijs, Day, James (Jed) E, du Bray, Edward A, Manning, Andrew H, Bancroft, Alyssa M
• Other Authors: Arribas, AM, Mauk, JL
• Format: Conference Object
• Language: English
• Published: Society of Economic Geologists 2018
• Subjects: Earth and Environmental Sciences; STRONTIUM ISOTOPE STRATIGRAPHY; OCEANIC ANOXIC EVENTS; ZN-PB; MINERALIZATION; WESTERN BROOKS RANGE; FLUID-FLOW; PALEOMAGNETIC; EVIDENCE; NORTHERN AUSTRALIA; SR-87/SR-86 VALUES; PHANEROZOIC TIME; AG; DEPOSITS; Macmillan Pass; Navan; Brooks Range
• Online Access: https://biblio.ugent.be/publication/8585272; http://hdl.handle.net/1854/LU-8585272; https://doi.org/10.5382/SP.21.05; https://biblio.ugent.be/publication/8585272/file/8585273

Times of metal-rich brine discharge into ancient ocean basins, associated with the formation of sedimentary-exhalative (sedex) Zn-Pb-Ba ore deposits, coincided with short-duration positive excursions ("spikes") in the global marine Sr isotope record. While these spikes are unexplained by conventional oceanic models, chronostratigraphic correlations, combined with mass balance evidence and oceanographic modeling, suggest that the flux of radiogenic Sr from sedex brines during ore formation is sufficient to explain these previously enigmatic Sr-87/Sr-86 spikes. We review existing Sr-87/Sr-86 data and present new data as verification of these global Sr-87/Sr-86 spikes and their correlations with the formation of giant sedex ore deposits. Major events include an 1 x 10(-4) (similar to 0.7078-similar to 0.7079) excursion contemporaneous with formation of the Rammelsberg deposit at -389 Ma; spikes on the order of 1 to 3 x 10(-4), coeval with formation of the Meggen deposit at similar to 381 Ma, several ore deposits in the Macmillan Pass district at similar to 379 to 375 Ma, and the Silvermines deposits at similar to 352 Ma; and two >6 x 10(-4) spikes coincident with formation of the giant Navan deposit at similar to 346 Ma and Red Dog deposits at similar to 337 Ma. Moreover, the timing of peak 8(87)Sr/Sr-86 spikes correlates with global delta C-13 and delta O-18 spikes,deposition of metal-rich black shales and ironstones, metal-induced malformation (teratology) of marine organisms, and mass extinctions. The relationships among these features were poorly understood, but our new model explains how the flux of key biolimiting nutrients and metals contained in sedex brines, demonstrably equivalent to or exceeding that of the total modern riverine flux to the ocean, spurred ocean eutrophication, which, ultimately, through a series of positive feedback mechanisms, may have triggered global chemical and biological events. If, as we hypothesize, sedex hydrothermal systems are recorded in the global marine isotopic, ...