TY - JOUR
T1 - Surge of ore metals in seawater and increased bio-activity
T2 - a tracer of VHMS mineralization in Archaean successions, Yilgarn Craton, Western Australia
AU - Barrote, Vitor R.
AU - Tessalina, Svetlana G.
AU - McNaughton, Neal J.
AU - Evans, Noreen J.
AU - Hollis, Steven P.
AU - McDonald, Bradley J.
N1 - Author is new to the University of Edinburgh, he is awaiting the accepted manuscript from the corresponding author.
PY - 2020/6/19
Y1 - 2020/6/19
N2 - The Nimbus Ag–Zn(–Au) deposit is a hybrid VHMS deposit with epithermal characteristics formed in the Eastern Goldfields Superterrane, Yilgarn Craton, under shallow water (~ 700 mbsl), low-temperature conditions. Intersections of some ore lenses are high-grade and polymetallic, making similar styles of mineralization attractive Yilgarn exploration targets. The mineralization at Nimbus is hosted by a bimodal felsic–mafic succession of volcanic rocks, which are overlain by a succession of least-altered polymict conglomerates with a carbonaceous to dacitic matrix. A new Re–Os age (2680 ± 34 Ma; nodular pyrite and black shale) suggests that the overlying polymict conglomerate is coeval to ~ 2.70 Ga volcanism and mineralization at Nimbus. The pyrite within the high-grade polymetallic sulfide assemblages has a consistently lower Sb/Ag ratio (1–30) than pyrite from other sulfide phases (e.g., 30 to 1000 in colloform and barren pyrite). Trace elements (TEs) in sedimentary nodular pyrite from multiple intervals along a single drillhole (NBDH010), indicate the existence of an enriched sedimentary interval with higher total TE content, Ag/Au and Sb/Au, lower S/Se, and polymetallic-like signature of Sb/Ag. Within this enriched interval, the black shale matrix of the polymict conglomerate shows higher total organic carbon (TOC), Mo content, and Co/Ni ratios and suggest increased bio-activity at that time, interpreted to be associated with the Ag–Zn(–Au) mineralization. The TE characteristics in sedimentary pyrite, reflecting increased metal content in seawater inferred from in situ pyrite trace element analysis has the potential to be developed into an exploration tool for successions, adjacent and coeval to similar ore deposits.
AB - The Nimbus Ag–Zn(–Au) deposit is a hybrid VHMS deposit with epithermal characteristics formed in the Eastern Goldfields Superterrane, Yilgarn Craton, under shallow water (~ 700 mbsl), low-temperature conditions. Intersections of some ore lenses are high-grade and polymetallic, making similar styles of mineralization attractive Yilgarn exploration targets. The mineralization at Nimbus is hosted by a bimodal felsic–mafic succession of volcanic rocks, which are overlain by a succession of least-altered polymict conglomerates with a carbonaceous to dacitic matrix. A new Re–Os age (2680 ± 34 Ma; nodular pyrite and black shale) suggests that the overlying polymict conglomerate is coeval to ~ 2.70 Ga volcanism and mineralization at Nimbus. The pyrite within the high-grade polymetallic sulfide assemblages has a consistently lower Sb/Ag ratio (1–30) than pyrite from other sulfide phases (e.g., 30 to 1000 in colloform and barren pyrite). Trace elements (TEs) in sedimentary nodular pyrite from multiple intervals along a single drillhole (NBDH010), indicate the existence of an enriched sedimentary interval with higher total TE content, Ag/Au and Sb/Au, lower S/Se, and polymetallic-like signature of Sb/Ag. Within this enriched interval, the black shale matrix of the polymict conglomerate shows higher total organic carbon (TOC), Mo content, and Co/Ni ratios and suggest increased bio-activity at that time, interpreted to be associated with the Ag–Zn(–Au) mineralization. The TE characteristics in sedimentary pyrite, reflecting increased metal content in seawater inferred from in situ pyrite trace element analysis has the potential to be developed into an exploration tool for successions, adjacent and coeval to similar ore deposits.
KW - Re–Os dating
KW - Sedimentary pyrite
KW - Trace elements
KW - VHMS
UR - http://www.scopus.com/inward/record.url?scp=85086713253&partnerID=8YFLogxK
U2 - 10.1007/s00126-020-00986-6
DO - 10.1007/s00126-020-00986-6
M3 - Article
AN - SCOPUS:85086713253
SN - 0026-4598
JO - Mineralium deposita
JF - Mineralium deposita
ER -