11:15 AM - 11:30 AM
[SRD39-08] Mineralization of Ag-rich Sulfide Minerals in Chimney Samples at Bayonnaise Knoll, Izu-bonin Arc.
Keywords:Beyonnaise Knoll, Chimney, Ag-sulfide Minerals
Chimney has a tubular structure and the growth axis is perpendicular to the chimney length. A manganese oxide is covered to the surface, 1) a white sulfate rich portion (G1), 2) followed by a gray portion containing sulfide (G2) and 3) a black porous portion containing sulfide (G3). This simillar classification can be also observed in the Kuroko-ore. Ba distribution are evenly confirmed in G1-G2 but only confiremed in G3 as a large crystalline portion in vug. It is known from previous studies that the formation temperature of barite (G1) is mainly estimated as 150-215 ℃ and the formation temperature of sphalerite (G2-G3) is around 205-225 ℃. Sphalerite, galena and chalcopyrite, which belongs to Kuroko-ore, were mainly observed in G2-G3. These similar mineralization can be obtained Kuroko-ore. From EPMA measurements, Ag-rich portion is distributed mainly on the outside of G2 and Ag-Cu-Pb, in which sulfide minerals were confirmed. It is presumed that Ag-rich-sulfide minerals were formed at around 200 ℃ because of the formation temperature of barite and sphalerite and that Ag-rich-sulfide distribution.Therefore, from the above point, chimney and mound ore in the Bayonnaise Knoll, is Au and Ag rich, but characterized by a similar concentration of major elements (Cu, Pb, Zn) to the Kuroko ores. And it was found that Ag-sulfide minerals were distributed in G2.