TY - JOUR

T1 - The structure, mineral associations, and noble metals of the mir oceanic ore mound, the TAG hydrothermal field (Mid-Atlantic Ridge, 26°N latitude)

AU - Mozgova, N. N.

AU - Krasnov, S. G.

AU - Borodaev, Yu S.

AU - Stepanova, T. V.

AU - Cherkashev, G. A.

AU - Lalou, C.

AU - Samovarov, M. S.

PY - 1998/1/1

Y1 - 1998/1/1

N2 - The horizontal asymmetrical zonation of the inactive Mir hydrothermal mound (the TAG field, 26°N, Mid-Atlanlic Ridge) reflected in the south-north succession of Fe-Si, Zn, and Cu zones has been confirmed based on the complex study of ore minerals and their associations from the fragments of sulfide tubes and ore clasts. The age of mineralization varies from 63 to 0.7 ka. The chemistry and ratios of the prevalent sulfides reflect nonequilibrium formation conditions. Elevated Au and Ag contents were established in 10 large-sized samples and 117 lumps of ore (Au = 0.67-7.50, Ag = 9.90-440 and Au = 0.13-43.68, and Ag = 0.90-694.6 g/t, respectively); the highest contents are peculiar to tubes (Au from the Zn zone and Ag from the Cu zone). The interrelation of high Au and Hg contents is noted. Au and Ag are found in main sulfides (in 44 of 117, and in 108 of 199,microprobe analyses, respectively). Maximum Au contents (wt %) are as follows: 1.0 in exsolution products of idaite and bornite solid solutions, 1.1-1.2 in pyrite and chalcopyrite, 1.7 in sphalerite, 0.8 in marcasite, and 0.1 in covellite. Under a similar frequency of occurrence and the mineral composition becoming more complex, the Ag content increases to 1.2 wt % in exsolution products of idaite solid solutions and about 13 wt % in gray ore. Au and Ag are supplied by primary fluids. The successive replacement of minerals with the highest Au and Ag contents through zones is related to the hydrothermal alteration of ores during the infiltration-metasomatic growth of zones. The appearance of single grains of native gold, Zn-bearing copper, and Ag-containing sulfides is related to ore substance transformations (including submarine hypergenesis).

AB - The horizontal asymmetrical zonation of the inactive Mir hydrothermal mound (the TAG field, 26°N, Mid-Atlanlic Ridge) reflected in the south-north succession of Fe-Si, Zn, and Cu zones has been confirmed based on the complex study of ore minerals and their associations from the fragments of sulfide tubes and ore clasts. The age of mineralization varies from 63 to 0.7 ka. The chemistry and ratios of the prevalent sulfides reflect nonequilibrium formation conditions. Elevated Au and Ag contents were established in 10 large-sized samples and 117 lumps of ore (Au = 0.67-7.50, Ag = 9.90-440 and Au = 0.13-43.68, and Ag = 0.90-694.6 g/t, respectively); the highest contents are peculiar to tubes (Au from the Zn zone and Ag from the Cu zone). The interrelation of high Au and Hg contents is noted. Au and Ag are found in main sulfides (in 44 of 117, and in 108 of 199,microprobe analyses, respectively). Maximum Au contents (wt %) are as follows: 1.0 in exsolution products of idaite and bornite solid solutions, 1.1-1.2 in pyrite and chalcopyrite, 1.7 in sphalerite, 0.8 in marcasite, and 0.1 in covellite. Under a similar frequency of occurrence and the mineral composition becoming more complex, the Ag content increases to 1.2 wt % in exsolution products of idaite solid solutions and about 13 wt % in gray ore. Au and Ag are supplied by primary fluids. The successive replacement of minerals with the highest Au and Ag contents through zones is related to the hydrothermal alteration of ores during the infiltration-metasomatic growth of zones. The appearance of single grains of native gold, Zn-bearing copper, and Ag-containing sulfides is related to ore substance transformations (including submarine hypergenesis).

UR - http://www.scopus.com/inward/record.url?scp=0742297789&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0742297789

VL - 40

SP - 228

EP - 249

JO - Geology of Ore Deposits

JF - Geology of Ore Deposits

SN - 1075-7015

IS - 3

ER -