南祁连化隆地区下什堂含铜镍矿基性-超基性岩体成因研究:锆石年代学、地球化学和Sr-Nd同位素约束  

The genesis study on Xiashentang basic-ultrabasic intrusion associated with Ni-Cu mineralization in Hualong,southern Qilian Mountains: Zircon geochronology,geochemistry and Sr-Nd isotopic constraints

作　　者：张照伟[1] 李文渊[1] 王亚磊[1] 高永宝[1] 

机构地区：[1]国土资源部岩浆作用成矿与找矿重点实验室,西安710054

出　　处：《岩石学报》2015年第9期2539-2548,共10页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41102050);中国地质调查局地质科研项目(121201112092;1212011121088;1212011120183)联合资助

摘　　要：主要由橄榄岩相、辉石岩相组成的下什堂基性-超基性岩体侵位于南祁连造山带化隆岩群中,且伴有磁黄铁矿、镍黄铁矿和黄铜矿等的硫化物矿化。精确的LA-ICP-MS锆石U-Pb定年获得了下什堂岩体的形成年龄为449.8±2.4Ma。地球化学表现为轻稀土富集和明显的Nb-Ta负异常特征,εNd值在-2.62^-2.52之间,(87Sr/86Sr)i比值集中在0.709012~0.714682之间。Sr-Nd同位素表明,下什堂基性-超基性岩体的母岩浆来自一个曾经被交代富集的地幔源区。地壳富硅组分的同化混染在成矿过程中起了很重要的控制作用。结合区域构造演化背景与成矿认识,认为南祁连化隆地区的成岩成矿可能与俯冲结束后,后碰撞伸展环境密切相关,这对于指导区域找矿实践和成矿理论研究均具重要的地质意义。The Xiashentang basic-ultrabasic intrusion which mainly composed of peridotites and pyroxenite was intrusived into Hualong rocks group in the southern margin of the Qilian Block,sulfide mineralization in the intrusion is dominated by disseminated sulfides of pyrrhotite,pentlandite and chalcopyrite. Precise LA-ICP-MS zircon U-Pb dating reveals that the ages of the Xiashentang intrusion is 449. 8 ± 2. 4Ma. The Xiashentang intrusion was characterized by light REE enrichments relative to heavy REE and pronounced negative Nb-Ta anomalies,consistent with the products of arc magmatism. The εNd values from- 2. 62 to- 2. 52 and elevated（87Sr /86Sr）i ratios from 0. 709012 to 0. 714682. Sr-Nd isotopic compositions show that the parent magma of Xiashentang in Hualong originated from ever metasomatic enriched mantle source. The isotope data collectively suggest that silicification was involved in ore genesis at Xiashentang,and played a significant controlling role. Our results show that the Hualong region of southern Qilian Mountains may host the post-collisional extension type,small Ni-Cu sulfide deposits. Our main focuses are the ages of the intrusions,the style of magmatism and sulfide mineralization, which have practical significance for the future of mineral exploration and mineralization theories study on Ni-Cu deposits in this region.

关 键 词：锆石U-PB定年 Sr-Nd同位素组成 基性-超基性岩体 成因 下什堂 南祁连 

分 类 号：P588.125[天文地球—岩石学] P597.3[天文地球—地质学]