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Germanium‐bearing Colusite in Siliceous Black Ore from the Ezuri Kuroko Deposit, Hokuroku District, Japan
Author(s) -
Komuro Kosei,
Kajiwara Yoshimichi
Publication year - 2004
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2004.tb00220.x
Subject(s) - sphalerite , chalcopyrite , galena , tetrahedrite , geology , germanium , mineralization (soil science) , pyrite , electron microprobe , geochemistry , mineralogy , mineral , metallurgy , copper , materials science , silicon , soil science , soil water
. Germanium‐bearing colusite occurs with sphalerite, galena, tetrahedrite‐tennantite, chalcopyrite and pyrite in microdruses and veinlets in the siliceous black ore from the Ezuri Kuroko deposit in the Hokuroku district of Japan. X‐ray microdiffractometry of this mineral gives strongest lines at 1.60, 1.32 and 1.09 Å, which are consistent with the known powder diffraction data of colusite. On the basis of 32 S atoms per formula unit, electron microprobe analyses yield empirical chemical formulae of (Cu 24 0 Fe 0.3 Zn 1.0 ) σ25.3 V 1.9 (A s4.8 Sb 0.2 ) σ5.0 Ge 1.3 S 32 for Ge‐bearing colusite in close association with sphalerite, and (Cu 24.6 Fe 0.9 ) σ25.4 V 1.8 (A s4.1 Sb 0.2 ) σ4.3 Ge 1.7 S 32 for that coexisting with chalcopyrite, consistent with the ideal formula of Cu 24+x V 2 (As, Sb) 6‐x (Sn, Ge) x S 32 (x = 0 to 2) proposed by Spry et al. (1994) for this mineral species. The Ge‐bearing colusite mineralization is suggested to have occurred concurrently with consolidation of the siliceous black ore, possibly during hydrothermal modification in association with the igneous activity of the Ohtaki quartz diorite of the later Onnagawa stage. It is likely that biogenic siliceous ooze, a possible precursor of the siliceous black ore, may have served as an in situ source of Ge as well as other essential rare elements, leading to the formation of Ge‐bearing colusite during transformation or recrystallization of biogenic opal into a‐quartz.