纳米比亚罗什皮纳地区泛非期花岗岩浆作用及其成矿效应

Gariep belt in south-west Afica has experienced the tectonic cycle of subduction and collision between South America plate and Kalahari plate during the Pan-African period, and is one polymetallic ore concentration area in southwest Africa after complicated structural evolution and extensive distribution of magma activity.A series of previous research on the tectono-thermal event in Gariep belt have been studied, and all of the research nearly focosed in formation-evolution-development of the orogenic belt and tectonic background, but the magmatic activities and mineralization mechanism were seldom mentioned.Hence, in this project the Pan-African granite,which is related with the mineralization such as molybdenite，zinc，plumbum and copper in Rosh pinah area of the south Gariep belt will be studied.Based on the modern isotopic dating method, clearing and definiting the era of the granite, completely researching about mineral chemistry and element geochemistry, the types of petrogenesis will be explained, the composition of source area and output tectonic environment will be discussed, earth's deep spheres function and the metallogenic effect will be explored. The magmatic evolution mode of the south Gariep Belt during the Pan-African period will be built. However, the detailed process of the collisional orogeny will be retrospected, and the mineralization mechanism of polymetallic deposit will be discussed in south-west africa.

西南非洲的加列普造山带在泛非期经历了南美与卡拉哈日板块拼合的俯冲-碰撞造山旋回，复杂的构造演化和广泛发育的岩浆活动使得该区成为西南非洲重要的多金属矿集区之一。前人已对加列普造山带的形成演化进行过一定程度的研究，但重点均集中在构造-热事件方面，而造山过程中岩浆活动及其成矿作用的研究则受到严重制约。鉴于此，本项目拟以加列普造山带南段罗什皮纳地区与铅、锌、铜、钼矿化作用密切相关的泛非期花岗岩作为研究对象，通过现代同位素定年方法，明确花岗岩的形成时代，并在矿物学、元素及同位素地球化学综合研究的基础上，阐明其岩石成因类型、源区物质组成以及产出构造环境，探讨深部圈层作用规律以及成矿效应。结合区域动力地质背景资料，构建加列普造山带南段泛非期岩浆演化模式，从而追溯并解译该地区泛非期碰撞造山的具体过程，探讨该区金属矿床的成矿机制。

项目对罗什皮纳地区罗雷铜矿区中部侵位于奥兰治河群石英云母片岩中的花岗闪长岩进行了锆石U-Pb年代学和全岩地球化学的分析。结果表明，岩浆锆石的206Pb/238U加权平均年龄为1860±10 Ma（n=21，MSWD=0.76），指示了该岩体为古元古代亚马逊造山运动晚期的岩浆作用产物；该花岗闪长岩富硅、富铝，为弱过铝质岩石，稀土配分曲线为右倾型，具有明显Eu负异常，显示I型花岗岩类的特点。地质与地球化学分析显示罗雷铜矿区中部花岗闪长岩岩浆源自壳-幔混合源区，在上升演化过程中经历了显著的分离结晶作用；该花岗闪长岩体具有富铜岩浆岩的特点，是该铜矿床的成矿岩体；罗雷铜矿区内中部花岗闪长岩及其成矿作用形成于亚马逊造山运动后碰撞的构造背景。

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