地质通报2017，Vol.36Issue(6)：945-955,11.
西藏多龙矿集区萨玛隆闪长岩LA-ICP-MS锆石U-Pb年龄和岩石化学特征及其对成矿背景的约束
LA-ICP-MS zircon U-Pb age and petrochemistry of the Samalong diorite in the Duolong metallogenic area of Tibet and its constraint on the metallogenic setting of the porphyry deposits
摘要
Abstract
The Duolong ore concentration area is the most favorable potential prospecting area in the Bangong Co-Nujiang metallogenic belt.Four porphyry Cu-Au deposits have been discovered in the Duolong area,but their metallogenic setting is still in controversy.The Samalong diorite is located in the central part of the Duolong area.Combined with the tectono-magmatic activation,the authors studied geochronology and bulk geochemistry of the Samalong diorite so as to constrain the metallogenic setting of the porphyry deposits.25 zircon samples selected form the Samalong diorite intrusion were analyzed by LA-ICP-MS,which yielded a weighted 206Pb/238U age of 121.6±1.7Ma (MSWD=1.9,n=23),which represents its intrusive age.According to the bulk petrochemical results,the Samalong diorite intrusion belongs to the middle potassium and sodium-rich magmatic series.The Samalong diorite is also enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high field-strength elements,with high Sr and low Y concentrations,suggesting adakite-like affinity.The high initial 87Sr/86Sr values (0.7056～ 0.7073) and low initial 143Nd/144Nd (0.5124～0.5125) and ε Nd(t) (-1.3～0.7) suggest that the Samlong diorite was generated from the lower crust,and its relative high MgO content and incompatible elements (Cr,Ni,etc.) concentrations indicate that there might have been some melt derived from the peridotitic mantle wedge mixed in the source region.The Samalong diorite was cut by the former strike-slip faults,which probably suggests that these later strike-slip faults controlled the formation of the porphyry deposits within 116～121Ma,and the porphyry deposits in the Duolong ore concentration area were formed within the structural transferring period at the last stage of the northward subduction ofBangong Co-Nujiang Neo-Tethys Ocean.关键词
多龙矿集区/闪长岩/斑岩铜矿/成矿背景/锆石U-Pb测年/LA-ICP-MSKey words
Duolong ore concentration area/diorite/porphyry copper deposit/metallogenic setting/zircon U-Pb dating/LA-ICP-MS分类
天文与地球科学引用本文复制引用
陈华安,祝向平,刘朝强,李光明,马东方,段志明,李玉昌,卫鲁杰..西藏多龙矿集区萨玛隆闪长岩LA-ICP-MS锆石U-Pb年龄和岩石化学特征及其对成矿背景的约束[J].地质通报,2017,36(6):945-955,11.基金项目
国家自然科学基金项目《西藏自治区改则县多不杂斑岩铜金矿床岩浆演化与成矿背景研究》(批准号:41202049)、《西藏冈底斯过铝花岗岩的岩石成因及其对地壳生长的约束》(编号:41272091)和中国地质调查局项目《中国矿产地质与成矿规律综合集成和服务》(矿产地质志)(编号:DD20160346)、《滇西地区三稀等重要矿产地质调查》(编号:DD20179604)、《西南三江有色金属资源基地调查》(编号:DD20160016) （批准号:41202049）
