东南亚红土镍矿床地质地球化学特征及成因探讨——以印尼苏拉威西岛Kolonodale矿床为例

Kolonodale矿床是东南亚红土镍矿带上一处典型矿床,位于印度尼西亚苏拉威西岛东部。矿床产自富镁超基性岩红土风化壳,矿化剖面自上而下出现红土层→腐岩层→基岩层垂向分带。红土镍矿石产在红土剖面上部,载镍矿物是铁质氧化物。硅镁镍矿石产在红土剖面中下部,载镍矿物为镍蛇纹石、镍滑石等含水层状硅酸盐矿物。地球化学分析显示,沿矿化剖面元素地球化学分异非常显著,Ni次生富集效应明显。超基性岩红土化过程的元素地球化学行为具有多样性,Fe、Al、Ti、Cr属残留富集组分,Si、Mg属淋滤缺失组分,Mn、Ca、Co、Ni属次生富集组分。通过典型矿床对比,Kolonodale矿床属原地自生硅酸盐型红土镍矿床,其发育受地质背景和地表环境条件的综合制约。富镁超基性岩、良好的构造组合、稳定的大地构造环境、湿热热带雨林气候、有利地形地貌等均是成矿有利条件。综合分析认为,Kolonodale矿床的成矿过程可划分为腐岩化、红土化和次生富集3个成矿阶段。

Geological and geochemical characteristics of laterite nickel deposit and ore genesis—A case study of Kolonodale deposit in Indonesia Sulawesi,

Laterite nickel deposit is a hotspot of global nickel resource exploration and development, and it is also a key target of foreign mineral resource exploration for our country. The Kolonodale deposit located in Sulawesi Island in Indonesia is a typical deposit in SE Asian laterite nickel deposit belt. The deposit occurred in laterite weathering profile of ultramafic rocks. The ore bearing profile can be divided into four vertical layers: the red ferric oxide layer, the yellow clay layer, the sage green ore layer and the protolith. The laterite ore occurred in the upper part of the regolith profile. The major Ni bearing minerals are ferric oxyhydroxides. The silicate ore occurred in the middle and lower part of the regolith profile, forming in cracks and voids of saprolite and protolith, dominated by nepouite, willemseite and other hydrated Mg Ni silicates. The geochemical data show that the differentiation of elements along the profile is obvious, especially the high enrichment of Ni in the deeper layer. The migration of elements in lateritization was affected by superficial environment and geochemical activities. Fe, Al, Ti, and Cr represent the residual elements, Si and Mg belong to filtering elements and Mn, Ca, Co, and Ni are classified to the secondary rich elements. By comparison with global typical laterite nickel deposits, the Kolonodale is determined to be of the in situ silicate type. It is formed by coupling many geological and geographical factors, including the geochemical source from ultramafic rocks, the weathering force affected by rain forest climate, the filtering and precipitation channels provided by structural activities, the ore deposition space offered by good relief, and the time insurance from stable tectonic environment. This study indicates that the ore forming process of the Kolonodale deposit can be divided into three stages: The sparolite stage, the laterite stage and the secondary enrichment stage.