Surge of ore metals in seawater and increased bio-activity: a tracer of VHMS mineralization in Archaean successions, Yilgarn Craton, Western Australia

Barrote, Vitor; Tessalina, Svetlana; McNaughton, Neal J.; Evans, Noreen J.; Hollis, Steven P.; McDonald, Bradley J.

doi:10.1007/s00126-020-00986-6

Cited by 1 publication

(3 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The latter event includes the resetting of sericite 40 Ar- 39 Ar ages and remobilization of minor base metals in quartz-carbonate veins [15]. Most recently, Barrote et al [16] have detailed trace element variations in hanging-wall polymict conglomerates above the Nimbus deposit, providing further evidence that mineralization was syngenetic with the host stratigraphy. Here, we build on all these recent accounts, incorporating new petrographic observations with lithogeochemical and hyperspectral data.…”

Section: Previous Research and Methodsmentioning

confidence: 99%

“…These same zones are also marked by a higher abundance of quartz in the TIR, due to intense silicification. Very high wavelength absorption features (at~2205 m to 2220 nm) were only identified towards the top of hole NBDH010, associated with polymict conglomerates, which form the least altered hanging-wall of the Nimbus deposit [13,16].…”

Section: Hyperspectral Halos To Mineralizationmentioning

confidence: 99%

“…Consequently, its origin has been contentious for a number of years with early models favoring either a VMS deposit [9,10] or a fault-hosted high sulfidation deposit [11]. Based on its tectonostratigraphic position, paleo-environmental setting, the geochemistry of its host sequence (i.e., FI-affinity felsic volcanic rocks), sulfide mineralogy (e.g., Ag-Sb-Pb-As sulfosalts, high Hg, minor chalcopyrite), and chlorite-poor alteration assemblages, the Nimbus deposit has most recently been interpreted as a "hybrid" VMS deposit which displays a number of epithermal characteristics due to its inferred shallow water depth [12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Lithogeochemical and Hyperspectral Halos to Ag-Zn-Au Mineralization at Nimbus in the Eastern Goldfields Superterrane, Western Australia

Hollis

Foury²,

Caruso

et al. 2021

Minerals

Self Cite

View full text Add to dashboard Cite

With new advances in rapid-acquisition geochemical and hyperspectral techniques, exploration companies are now able to detect subtle halos surrounding orebodies at minimal expense. The Nimbus Ag-Zn-(Au) deposit is unique in the Archean Yilgarn Craton of Western Australia. Due to its mineralogy, alteration assemblages, geochemical affinity, and tectonic setting, it is interpreted to represent a shallow water (~650 mbsl) and low-temperature (<250 °C) volcanogenic massive sulfide (VMS) deposit with epithermal characteristics (i.e., a hybrid bimodal felsic deposit). We present a detailed paragenetic account of the Nimbus deposit, and establish lithogeochemical and hyperspectral halos to mineralization to aid exploration. Mineralization at Nimbus is characterized by early units of barren massive pyrite that replace glassy dacitic lavas, and underlying zones of polymetallic sulfides that replace autoclastic monomict dacite breccias. The latter are dominated by pyrite-sphalerite-galena, a diverse suite of Ag-Sb ± Pb ± As ± (Cu)-bearing sulfosalts, minor pyrrhotite, arsenopyrite, and rare chalcopyrite. The main sulfosalt suite is characterized by pyrargyrite, and Ag-rich varieties of boulangerite, tetrahedrite, and bournonite. Zones of sulfide mineralization in quartz-sericite(±carbonate)-altered dacite are marked by significant mass gains in Fe, S, Zn, Pb, Sb, Ag, As, Cd, Ni, Cu, Ba, Co, Cr, Tl, Bi, and Au. Basaltic rocks show reduced mass gains in most elements, with zones of intense quartz-chlorite-carbonate±fuchsite alteration restricted to thick sequences of hyaloclastite, and near contacts with dacitic rocks. Broad zones of intense silica-sericite alteration surround mineralization in dacite, and are marked by high Alteration Index and Chlorite-Carbonate-Pyrite Index (CCPI) values, strong Na-Ca depletion, and an absence of feldspar (albite) in thermal infrared (TIR) data. White mica compositions are predominantly muscovitic in weakly altered sections of the dacitic footwall sequence. More paragonitic compositions are associated with zones of increased sericitization and high-grade polymetallic sulfide mineralization. Chlorite in dacitic rocks often occurs adjacent to zones of sulfide mineralization and is restricted to narrow intervals. Carbonate abundance is sporadic in dacite, but is most abundant outside the main zones of Na-Ca depletion. Basaltic rocks are characterized by strongly paragonitic white mica compositions, and abundant chlorite and carbonate. Shifts from Ca carbonates and Fe-rich chlorites to more Mg-rich compositions of both minerals occur in more intensely hydrothermally altered basaltic hyaloclastite, and near contacts with dacitic rocks. Hanging-wall polymict conglomerates are characterized by minor amounts of muscovitic to phengitic white mica (2205–2220 nm), and an absence of chlorite and carbonate alteration.

show abstract