A930 Goldschmidt Conference Abstracts 2007 A study on the formation mechanism High-grade Ag-Cu-Sn-In of Temagami Iron-Formations, mineralization in the Nishizawa- Canada Ashio area, Tochigi Prefecture, 1 1 1 Y. SHIMADA , A. YASUMATSU , Y. MOTOMURA , central Japan 1 1 2 1 R. OKAZAKI , T. NAKAMURA , H. OHMOTO , Y. OKAUE 1 2 1 MASAAKI SHIMIZU , SATOSHI MATSUBARA , AND T. YOKOYAMA 1 3 MARINA SHIMIZU , YOSHINORI KYOUNO , 4 5 1Fac. Sci., Kyushu University; Ropponmatsu, Chuo-ku, AKIRA HARADA AND NIGEL J. COOK Fukuoka, 810-8560, Japan; 1Department of Earth Sciences, University of Toyama, Japan (
[email protected]) (
[email protected]) 2Penn State University 2 Department of Geology and Paleontology, National Museum of Nature and Science In order to elucidate systematically the formation 3Omochanomachi Branch, Ashikaga Bank, Japan mechanism of BIF (Banded Iron-Formations), a BIF sample 4D. O. C. Consultant, Japan collected at Temagami, Canada was characterized by optical 5Natural History Museum, University of Oslo, Norway microscope, EPMA, Xray microscope, SIMS, and chemical analysis. This BIF can be divided into three layers visually; Mineral Identification and Observation black layer, white layer, red layer. Main minerals in the three Polymetallic (Au-Ag-Cu-Pb-Zn-Fe-As-Sb-Bi-Sn-In-W) layers were magnetite, dolomite and quartz with fine hematite vein-type mineralization in the Nishizawa-Ashio area occurs particles respectively. in strongly altered late Neogene felsic volcanic rocks. To estimate the formation temperature of each three Recently Ishihara (2006) and Ishihara et al. (2006) reported mineral and the formation environment (especially oxidation- that indium had been exploited in ore concentrates (e.g., 1200 reduction conditions), the oxygen isotope ratios (18O/16O) and tons In at Ashio).