西藏班公湖-怒江带西段龙荣矿集区的岩浆活动及其对成矿的指示  

Magmatism of the Longrong ore cluster,western Bangong-Nujiang belt,Tibet,and their metallogenic implications

作　　者：张夏楠 李光明[3] 秦克章[3] 李金祥 李真真 刘通[1] 邹心宇 罗辉 ZHANG XiaNan;LI GuangMing;QIN KeZhang;LI JinXiang;LI ZhenZhen;LIU Tong;ZOU XinYu;LUO Hui(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;Jiangxi Provincial Key Laboratory of Genesis and Prospect for Strategic Minerals,East China University of Technology,Nanchang 330013,China;State Key Laboratory of Lithospheric and Environmental Coevolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;State Key Laboratory of Tibetan Plateau Earth System,Environment and Resources,Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101,China;China Institute of Disaster Prevention,Sanhe 065201,China)

机构地区：[1]核资源与环境国家重点实验室,东华理工大学,南昌330013 [2]战略性矿产成矿理论与深部预测江西省重点实验室,东华理工大学,南昌330013 [3]岩石圈演化与环境演变全国重点实验室,中国科学院地质与地球物理研究所,北京100029 [4]青藏高原地球系统与资源环境重点实验室,中国科学院青藏高原研究所,北京100101 [5]防灾科技学院,三河065201

出　　处：《岩石学报》2025年第2期585-599,共15页Acta Petrologica Sinica

基　　金：第二次青藏高原科学考察研究(2019QZKK0806);国家自然科学基金项目(42102096、42462016)联合资助.

摘　　要：龙荣矿集区是在西藏班公湖-怒江成矿带(班-怒带)西段新近发现的一个矿集区,也是在班-怒带中,目前发现的唯一一个同时发育铁矿化(矽卡岩型)和铜矿化(斑岩型为主)的矿集区。该矿集区位于班-怒带西段目前已知Fe矿带的最东端和已知Cu矿带的最西端。针对龙荣矿集区中的花岗岩类岩石我们开展了锆石定年,全岩主微量、Sr-Nd同位素测试和锆石Hf同位素测试来限定其成因。锆石U-Pb数据表明,龙荣矿集区中与Fe矿化伴生的岩体年龄为~160 Ma(154.7~163.4Ma,2σ范围),与Cu/Cu-Pb-Zn矿化伴生的岩体年龄为~120Ma(115.9~127.9Ma,2σ范围),它们与班-怒带西段其他已知铁矿化和铜矿化的时间一致。这些岩石以高钾钙碱性为主,富集轻稀土和大离子亲石元素(如Rb、K和Pb),亏损高场强元素(如Nb、Ta),具有弧岩浆的典型地球化学特征。~160Ma酸性岩浆岩可能由近同期中性岩浆经历同化混染以及角闪石、斜长石、磷灰石等分离结晶形成,而~120Ma酸性岩浆岩的形成可能主要与近同期中性岩浆的分离结晶(角闪石、斜长石、独居石等)有关。其全岩初始Sr同位素范围为0.7066~0.7136,ε_(Nd)(t)范围为-8.6~-5.4,锆石ε_(Hf)(t)范围为-17.34~-4.83,均指示了古老地壳物质的加入;并且龙荣矿集区中~120Ma花岗岩类岩石比多龙和青草山同时期的花岗岩类岩石有更大比例的古老壳源物质,这可能与其距离俯冲带更远有关。龙荣矿集区~160Ma的岩浆岩可能形成于正常的班公湖-怒江洋北向俯冲阶段,而~120Ma的花岗岩类岩石可能是继北向俯冲的班公湖-怒江洋板片于平坦俯冲(145~125Ma)后、板片后撤的产物;两期岩浆作用的物质来源均为受交代的地幔楔与古老羌塘大陆地壳的混合。The Longrong ore cluster is a recently discovered ore district in the western segment of the Bangong-Nujiang metallogenic belt(the Ban-Nu belt in short),Tibet.It is also the only one known ore cluster which develops both Fe mineralization(skarn type)and Cu mineralization(porphyry type dominated)in the Ban-Nu belt.It is located at the easternmost part of known Fe mineralization belt,and the westernmost part of known Cu mineralization belt in the western segment of the Ban-Nu belt.We present zircon U-Pb ages,bulk-rock geochemical and Sr-Nd isotope data,as well as zircon Hf isotope data to constrain the petrogenesis of the granitoids in this ore cluster.Zircon U-Pb data yielded ages of~160Ma(154.7~163.4Ma,2σrange)for granitoids associated with Fe mineralization,and~120Ma(115.9~127.9Ma,2σrange)for granitoids associated with Cu/Cu-Pb-Zn mineralization,which are consistent with the mineralization ages of known iron deposits and copper deposits in the western segment of the Ban-Nu belt,respectively.These granitoids are of high-K calc-alkaline affinity,with enrichment of light rare earth elements(LREEs)and large-ion lithophile elements(e.g.,Rb,K,and Pb),and depletion of high-field strength elements(e.g.,Ta,Nb),which are typical of the geochemical signatures of the arc magmas.The felsic magmatic rocks formed at~160Ma may be related with assimilation and fractionation of amphibole,plagioclase and apatite from the coeval intermediate magma;while the felsic magmatic rocks formed at~120Ma may be generated mainly by fractionation of amphibole,plagioclase,and monazite from the coeval intermediate magma.The two periods of Longrong granitoids have initial Sr isotopic ratios of 0.7066~0.7136,ε_(Nd)(t)values of-8.6 to-5.4,and zirconε_(Hf)(t)values of-17.34 to-4.83,indicating old crustal materials added to them.Compared with contemporaneous granitoids from the Duolong ore cluster and the Qingcaoshan deposit,the~120Ma Longrong granitoids sourced from a larger proportion of crustal materials,likely arising from the further distanc

关 键 词：龙荣 斑岩矿床 矽卡岩矿床 岩石成因 班公湖-怒江成矿带 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]