【摘要】 十二排钼矿床位于上杭-云霄断裂带与闽西南拗陷的复合部位,是紫金山铜金矿田外围新近探明的一处具有中大型远景的斑岩型钼矿床。野外地质调查显示,其钼矿化呈细脉状、网脉状主要产出于黑云母二长花岗岩和黑云母花岗斑岩中。热液蚀变具有斑岩型矿床的分带特征,由黑云母花岗斑岩向外依次发育钾硅酸盐化带、绢英岩化带和青磐岩化带,钼矿体主要赋存于绢英岩化与钾硅酸盐化构成的叠加带中。锆石U-Pb定年结果表明,黑云母二长花岗岩和黑云母花岗斑岩分别形成于（143.1±0.9）Ma和（143.5±0.4）Ma。4件辉钼矿样品的Re-Os加权平均年龄为（143.9±2.1）Ma。辉钼矿的w（Re）为1.2×10^-6～7.8×10^-6,说明成矿物质可能主要来自地壳。岩石地球化学分析结果显示,十二排含矿花岗岩具有相似的主量和微量元素组成,均属于弱过铝质高钾钙碱性I型花岗岩,其中,黑云母花岗斑岩表现出高分异花岗岩特征,两者可能是古老变质基底来源的熔体经历不同程度分异结晶的产物,并混入有少量幔源物质。综合已有的资料,文章认为十二排斑岩型钼矿化与早白垩世早期花岗质岩浆活动密切相关,上杭-云霄断裂带存在古太平洋板块俯冲后撤引发构造体制转换阶段的成岩成矿响应,进一步找矿勘查工作应加强评价早白垩世早期高分异花岗岩体的钼多金属成矿潜力。更多还原

【Abstract】 The Shierpai Mo deposit, located at the intersection of the southwestern Fujian depression belt and the Shanghang-Yunxiao fault zone, is an newly discovered porphyry Mo deposit with a medium-to large-sized prospecting prospective in the periphery of the Zijinshan Cu-Au orefield. Field observations reveal that veinlets and stockworks Mo mineralization occur in the biotite monzogranite and biotite granite porphyry. The deposit has developed typical porphyry-type alteration zoning, with potassic, phyllic and propylitic alteration zones from biotite granite porphyry outward. Mo mineralization is mainly hosted in the phyllic alteration overprinting potassic zone.Zircon U-Pb dating of the biotite monzogranite and biotite granite porphyry yielded weighted mean ages of（143.1±0.9）Ma and（143.5±0.4）Ma, respectively. Four molybdenite samples yielded Re-Os weighted mean age of（143.1±5.5）Ma with w（Re） varying from 1.2×10^-6 to 7.8×10^-6, indicative of a crustal origin for the ore metals.Geochemical data show that the two ore-related granitic rocks have similar major and trace elemental compositions, belonging to weak peraluminous, high-K calc-alkaline I-type granites, whereas biotite granite porphyry has characteristics of a highly fractionated I-type granite. They were probably derived from partial melting of the Proterozoic basement rocks with addition of minor mantle components, and subsequently experienced variable degrees of fractional crystallization. Combined with the published data from the study area, the authors hold that the porphyry-type Mo mineralization was genetically linked with the emplacement of granitic rocks in the Shierpai deposit during the earliest Cretaceous. These data prove that the earliest Cretaceous magmatism and related mineralization occurred in the Shanghang-Yunxiao fault zone, probably in response to the tectonic regime transition triggered by the slab rollback of the paleo-Pacific Plate. The further prospecting exploration could strengthen the potential evaluation of Mo polymetallic mineralization for the Earliest Cretaceous highly fractionated granitoids in the study area.更多还原