13:45 〜 15:15
[HRE11-P01] Petrography and whole rock geochemistry of ore minerals from the Omatapati Cu–Ag prospect, Kaokoveld, Kunene region, Namibia
キーワード：mineralization, geochemistry, petrography
The Kaokoveld mineral province in Kunene region, northwestern Namibia is part of the Pan-Africa Damara Orogenic Kaoko Belt. The Damara Orogeny deformed sediments of the Damara Supergroup and formed the Damara, Gariep, and Kaoko Belts, a triple junction around Swakopmund. The Damara Supergroup hosts prominent deposits such as Tsumeb in the Otavi Group, and over 200 deposits and prospects including Omatapati Cu–Ag prospect hosted by shales, and dolostones of the Ombombo Subgroup. A mineralization zone 19 m run length interval of a drill core with 1.63–5.02 wt % Cu and 31–312 g/t Ag intersection was found at the Omatapati deposit, however, the shape of the ore body is still unknown (Webb, 2013). Also, the mineralogical and geochemical characteristics of the Omatapati prospect are poorly understood.
Hence, this study aims to reveal characteristics of mineralization of the Omatapati deposit based on petrography and whole rock geochemistry. On the basis of the observation of the drill core, zones of discordant quartz-calcite veins and disseminated host rock include primary chalcopyrite, bornite, ± chalcocite/digenite at 75 to 87 m run length, whereas sem-massive secondary covellite, chalcocite, spertiniite, delafossite, malachite, hematite ± gothite ± siderite ± barite at the surface to 34 m run length. Bulk chemical composition analysis using the atomic absorption spectrometer (AAS) for major elements including Cu, and the inductively-coupled plasma mass spectrometry (ICP–MS) analysis for REEs and trace elements of the ores and host rock indicates 1–14 wt % Cu and 24–523 ppm Ag for primary ores and up to 51 wt % Cu and 1376 ppm Ag for secondary mineralization. The post-Archean Austrian shale (PAAS)–normalized rare earth elements (REE) display a concave–up depleted light rare earth elements (LREE) profiles with relatively flat heavy rare earth elements (HREE) profiles. These REE profiles are characterized by a strong positive Eu anomaly and are similar to those reported by O’Neil et al. (2007) for the banded iron formation (BIF) of marine origin, hence, the data points out a significant marine contribution to the formation of the Omatapati Cu–Ag deposit.
References:
O’Neil, J., Maurice, C., Stevenson, R.K., Larocque, J., Cloquet, C., David, J., and Francis, D., 2007, Chapter 3.4 The Geology of the 3.8 Ga Nuvvuagittuq (Porpoise Cove) Greenstone Belt, Northeastern Superior Province, Canada. Developments in Precambrian Geology, v. 15, no. 41371315, p. 219–250.
Webb, K., 2013, Final Technical Report of INV Metals’ Activities at the Kaoko JV Project, Namibia.
Hence, this study aims to reveal characteristics of mineralization of the Omatapati deposit based on petrography and whole rock geochemistry. On the basis of the observation of the drill core, zones of discordant quartz-calcite veins and disseminated host rock include primary chalcopyrite, bornite, ± chalcocite/digenite at 75 to 87 m run length, whereas sem-massive secondary covellite, chalcocite, spertiniite, delafossite, malachite, hematite ± gothite ± siderite ± barite at the surface to 34 m run length. Bulk chemical composition analysis using the atomic absorption spectrometer (AAS) for major elements including Cu, and the inductively-coupled plasma mass spectrometry (ICP–MS) analysis for REEs and trace elements of the ores and host rock indicates 1–14 wt % Cu and 24–523 ppm Ag for primary ores and up to 51 wt % Cu and 1376 ppm Ag for secondary mineralization. The post-Archean Austrian shale (PAAS)–normalized rare earth elements (REE) display a concave–up depleted light rare earth elements (LREE) profiles with relatively flat heavy rare earth elements (HREE) profiles. These REE profiles are characterized by a strong positive Eu anomaly and are similar to those reported by O’Neil et al. (2007) for the banded iron formation (BIF) of marine origin, hence, the data points out a significant marine contribution to the formation of the Omatapati Cu–Ag deposit.
References:
O’Neil, J., Maurice, C., Stevenson, R.K., Larocque, J., Cloquet, C., David, J., and Francis, D., 2007, Chapter 3.4 The Geology of the 3.8 Ga Nuvvuagittuq (Porpoise Cove) Greenstone Belt, Northeastern Superior Province, Canada. Developments in Precambrian Geology, v. 15, no. 41371315, p. 219–250.
Webb, K., 2013, Final Technical Report of INV Metals’ Activities at the Kaoko JV Project, Namibia.