摘要
海苏沟岩体位于大兴安岭造山带南段,岩体中发育有海苏沟钼矿床及小井子北铜钼矿床,目前对该岩体的了解还不完善,成因类型存在争议且对两个钼矿床间差异并未进行探讨.对该岩体不同岩相花岗岩开展锆石U-Pb年代学、岩石地球化学研究,对矿区内辉钼矿进行Re-Os同位素研究.获得海苏沟钼矿床黑云母花岗岩年龄结果为137.1±0.6 Ma和143.6±0.8 Ma,测得Re-Os模式年龄为143.9±2.9 Ma.小井子北铜钼矿区二长花岗岩年龄为126.5±0.7 Ma.海苏沟岩体中花岗岩均属高钾钙碱性系列I型花岗岩,具准铝质-弱过铝质特征,主量元素SiO2含量为68.81%~77.18%,K2O+Na2O含量为6.80%~8.31%,CaO含量为0.43%~2.88%,MgO含量为0.15%~1.32%,A/CNK值介于0.97~1.07.岩石相对富集轻稀土,(La/Yb)N=6.19~10.74,稀土配分呈右倾海鸥型,具有中等铕负异常(δEu=0.37~0.81).结合已有的研究结果,认为海苏沟岩体演化过程中经历了强烈的分离结晶作用,该岩体黑云母花岗岩与钼矿床的形成密切相关.海苏沟岩体的成岩及钼成矿作用的时间与西拉沐伦成矿带的第3期大规模成岩成矿作用时间相吻合,对应当时的构造背景为构造体系转折(由挤压环境转变为拉伸环境)至岩石圈减薄的环境.
The Haisugou rock mass is located in the southern part of the Daxing’anling orogenic belt.The Haisugou Mo deposit and the Xiaojingzibei Cu and Mo deposit are found in the intrusive mass.At present,the understanding of the rock mass is insufficient,the genetic type is controversial and the difference between the two molybdenum deposits has not been discussed.In this study,zircon U-Pb geochronology and petro-geochemistry analyses were carried out on different rocky granites in Haisugou rock mass,and Re-Os isotope analyses on molybdenite in the mining area were conducted.The LA-ICP-MS zircon U-Pb dating results of the biotite granite in the Haisugou molybdenum mining area are 137.1±0.6 Ma and 143.6±0.8 Ma;the Re content of molybdenite in the Haisugou molybdenum deposit is 2.1×10-6,the molybdenite Re-Os model age is 143.9±2.9 Ma.The dating result of LA-ICP-MS zircon U-Pb of the monzonitic granite in the Xiaojingzibei copper-molybdenum deposit is 126.5±0.7 Ma.The granite in the Haishugou pluton belongs to high-K calc-alkaline series I-type granite with metaluminous to weakly peraluminous characteristics.The main elements SiO2 content is 68.81%-77.18%,K2 O+Na2 O=6.80%-8.31%,CaO content ranges from 0.43%to 2.88%,MgO ranges from 0.15%to 1.32%and aluminum index(A/CNK)value ranges from0.97 to 1.07.The rocks are relatively enriched in light rare-earth elements(La/Yb)N=6.19-10.74 and the rare earth distribution pattern is right-dipping with a moderate negative Eu anomalies with aδEu value from 0.37 to 0.81.By combining existing research results,It can be considered that the magma evolution experienced magma mixing and the fractional crystallization plays a dominant role.The time of diagenesis and molybdenum metallogenesis of the Haisugou intrusive mass coincides with the time of the third phase of the large-scale diagenesis and mineralization of the Silamulun metallogenic belt,indicating the corresponding tectonic background is the transition of the tectonic system(from the extrusion environment to the tensile environment)to the lithosphere thinning environment.
作者
谢元惠
李小伟
祝新友
黄行凯
刘腾
徐巧
刘孜
Xie Yuanhui;Li Xiaowei;Zhu Xinyou;Huang Xingkai;Liu Teng;Xu Qiao;Liu Zi(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Beijing Institute of Geology for Mineral Resources,Beijing 100012,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第1期43-60,共18页
Earth Science
基金
中国地质调查局基础性公益性地质矿产调查项目(No.DD20160072).
