【摘要】 海南抱伦金矿区的金矿脉与大量辉绿岩脉在空间上紧密相关。在详细的野外地质调查基础上,本文对这些辉绿岩脉开展了岩相学和矿相学观察、全岩主量和微量元素分析、Sm-Nd同位素组成分析、金丰度分析以及SHRIMP锆石U-Pb定年,初步探讨了辉绿岩脉的成因、岩浆演化和构造背景以及与金成矿作用的关系。地球化学分析结果表明,辉绿岩脉形成于拉斑玄武质岩浆,主要为左倾型的稀土配分模式;相对N-MORB,富集Sr、K、Rb和Ba等LILE和Th,亏损HFSE,ε_Nd（t）为0. 3～5. 6,说明岩浆源区为受到俯冲带含水流体影响和少量地壳混染的亏损地幔。辉绿岩脉的SHRIMP锆石U-Pb年龄为231. 6±2. 6Ma,与尖峰岭花岗质岩体的年龄（236±3. 5Ma～249±5Ma）相近,产出位置相邻,类似于海南兴隆地区的双峰式侵入岩,表明它们产出于造山后伸展环境。辉绿岩脉对应的岩浆富含CO₂、H₂O、F、K、Rb、Ba和适量的S,为抱伦金矿等单金矿床中Au的合适载体。金丰度分析结果表明,辉绿岩脉中的Au曾被活化迁移。再结合辉绿岩脉成岩年龄与抱伦矿区的成矿年龄在误差范围内一致的特征,认为抱伦金矿的Au可能来源于辉绿岩脉。更多还原

【Abstract】 A large number of diabase dykes were observed spatially associated with the auriferous quartz veins in the Baolun gold deposit in Hainan Province. Based on systematic field investigation,an integrated study of petrographical and mineralographical work,whole-rock major and trace elements,Sm-Nd isotopes and Au abundance analysis,as well as zircon SHRIMP （sensitive high massresolution ion microprobe） U-Pb dating has been undertaken on these diabase dykes to provide primary insights into their magmatic sources,evolutionary processes and associated tectonic environment,and to evaluate the relations between the diabase dykes and gold mineralization in the Baolun deposit. Geochemically,these diabase dykes can be classified into tholeiitic magma series,which are characterized by left-deeping REE pattern. In addition,compared with N-MORB,the diabase dykes are rich in large ion lithophile elements （LILEs）,such as Sr,K,Rb and Ba,and depleted in high field strength elements （HFSEs）. Their ε_Nd（t） values （ranging between 0. 3 and 5. 6） suggest that these diabase dykes were likely derived from a depeleted mantle source that had been metasomated by fluids from subduction zone and contaminated by the crust. The diabase dykes in the Baolun deposit have been dated at 231. 6 ±2. 6 Ma through SHRIMP U-Pb zircon method,which is close to the crystallization age of the Jianfengling granite （236 ± 3. 5 Ma ～ 249 ±5 Ma）. Combined with the adjacent occurences,the diabase dykes and the Jianfengling granite show characteristics of bimodal magmatic rocks,and thus a post-collisional environment is probably suitable for the generation of the protolith of the diabase dykes,which is consistent with the bimodal intrusive rocks in the Shuanglong area,Hainan Island. The magma for the diabase dykes is enriched in CO₂,H₂O,F,K,Rb and Ba as well as S,being a proper carrier for Au in the Baolun gold-only deposit. Au abundances also indicate that Au in the diabase dykes might have been reactivated and migrated. Further more,the diagenetic age of the diabase dykes is in agreement with the mineralization age of the Baolun deposit. Au in the Baolun gold deposit is thus considered to be sourced from these diabase dykes.更多还原