The Kamoa Copper Deposit, Democratic Republic of Congo: Stratigraphy, Diagenetic and Hydrothermal Alteration, and Mineralization
The Kamoa Copper Deposit, Democratic Republic of Congo: Stratigraphy, Diagenetic and Hydrothermal Alteration, and Mineralization
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刚果民主共和国卡莫阿铜矿床：地层学、成岩作用和热液蚀变以及矿化
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发表时间：
2013
期刊：
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通讯作者：
J. Humphrey
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作者：
Danielle S. Schmandt;D. Broughton;M. Hitzman;P. Plink‐Björklund;D. Edwards;J. Humphrey
卡莫阿铜矿位于刚果民主共和国南部加丹加省，位于以前被认为有大型铜矿远景的地区之外。以1%的铜为下限，卡莫阿的浅成矿带面积超过81平方公里，厚度从2到15米不等，目前横向上不受限制。该矿床赋存于赤铁矿和局部黄铁矿Mwa hya亚群砂岩与上覆的Nguba群大砾岩单元细粒黄铁矿之间的地层接触处。Mwa hya砂岩似乎沉积在边缘海-河环境中。大砾岩中含有冰源物质输运和沉积物重力流沉积。该单元似乎沉积在构造活跃、局部缺氧的海洋环境中。马瓦希亚和大砾岩单元之间的接触代表了在可能是快速下沉或海平面上升的时期沉积风格的重大变化。卡莫阿矿体大部分赋存于大砾岩单元的最下部，该单元含有粉砂岩，其中含有高浓度的成岩框架状黄铁矿，后来又含有可能表明早期热液活动的立方黄铁矿。后来，大砾岩内的热液蚀变矿物组合在地层上被分带，从最低地层单位中的钾质蚀变和硅化组合转变为地层中较高的以镁质为主的蚀变组合。矿期硫化物矿物垂直分带，远离Mwa hya-Grand砾岩接触带，从辉铜矿到斑铜矿再到黄铜矿再到黄铁矿，随着地层高度的增加。铜硫化物矿物以细粒的形式分布在角闪岩基质中，可能代表交代的成岩黄铁矿，也可能存在于角闪岩碎屑的粗粒矿物边缘中。边缘在最低的地层单位中最发育，在大小、垂直伸长和向上地层剖面丰度方面逐渐减小。硫同位素研究表明，铜硫化物中的大部分硫来自早期形成的成岩铁硫化物。流体包裹体分析表明，成矿流体为盐水，~23~26wt%NaClwt当量，均一温度(Th)为210~240℃。
The Kamoa copper deposit is located in the Katanga Province of the southern Democratic Republic of Congo outside of the area previously considered prospective for large copper deposits. With a 1% Cu cutoff, the hypogene ore zone of Kamoa spans over 81 km2, varying in thickness from 2 to 15 m, and is currently laterally unconstrained. The deposit is hosted at the stratigraphic contact between hematitic and locally pyritic Mwashya Subgroup sandstones and overlying fine-grained pyritic diamictites of the Grand Conglomerat unit of the Nguba Group. The Mwashya sandstones appear to have been deposited in a marginal marine to fluvial environment. The Grand Conglomerat diamictite contains glacially derived mass transport and sediment gravity flow deposits. The unit appears to have been deposited in a tectonically active, locally anoxic marine environment. The contact between the Mwashya and Grand Conglomerat units represents a major change in depositional style during what was probably a period of rapid subsidence or sea level rise. The majority of the Kamoa orebody occurs within the lowermost portion of the Grand Conglomerat unit that contains siltstones with high concentrations of diagenetic framboidal and later cubic pyrite that may be indicative of early hydrothermal activity. Later hydrothermal alteration mineral assemblages within the Grand Conglomerat are stratigraphically zoned, changing from a potassic alteration and silicification assemblage in the lowermost stratigraphic units to a dominantly magnesian alteration assemblage higher in the stratigraphy. Ore stage sulfide minerals are zoned vertically away from the Mwashya-Grand Conglomerat contact, changing from chalcocite to bornite to chalcopyrite to pyrite with increased stratigraphic height. Copper sulfide minerals occur as fine-grained disseminations within the diamictite matrix that probably represent replaced diagenetic pyrite as well as in coarse-grained mineral rims on diamictite clasts. The rims are best developed in the lowermost stratigraphic units and gradually lessen in size, vertical elongation, and abundance up stratigraphic section. Sulfur isotope studies indicate that most of the sulfur in the copper sulfides was derived from earlier formed diagenetic iron sulfide. Fluid inclusion analyses indicate that the ore-forming fluid was saline, ~23 to 26 wt % NaCl wt equiv, and had homogenization temperatures (T h ) ranging from 210° to 240°C.