西秦岭双朋西矽卡岩型金铜矿床花岗闪长岩LA-ICP-MS锆石U-Pb定年、岩石成因和构造意义

发布时间：2018-03-22 05:24

本文选题：花岗闪长岩　切入点：锆石U-Pb年龄　出处：《岩石学报》2017年02期 　论文类型：期刊论文

【摘要】：青海双朋西矽卡岩型金-铜矿床位于西秦岭造山带同仁-泽库弧后前陆盆地,区域出露地层主要为下二叠统甘家组、下三叠统隆务河群的沉积岩系。矿区侵入岩主要为花岗闪长岩,金矿体赋存于花岗闪长岩体与甘家组大理岩、白云岩接触带的矽卡岩中。本文对双朋西花岗闪长岩体开展了锆石LA-ICP-MS U-Pb年代学和岩石地球化学研究,结果表明,双朋西花岗闪长岩的结晶年龄为233.9±2.8Ma,具有高SiO_2、高K_2O,低Al_2O_3和MgO含量的特征,Mg~#值为33.6~35.2,富集轻稀土元素((La/Sm)N=3.14~11.6)与大离子亲石元素,重稀土元素分布平坦((Gd/Yb)N=1.17~1.63),具有中等的Eu负异常。具有较高的Sr初始值(Isr=0.708299~0.708748)和相对较低的εNd(t)值(-12.6~-9.47),~(206)Pb/~(204)Pb、~(207)Pb/~(204)Pb和~(208)Pb/~(204)Pb比值分别为18.623~18.965、15.610~15.652和39.124~40.732。Nb/Ta(5.5~12.9)、Ce/Pb比值(3.0~11.6)均与地壳组份一致,岩体中的暗色微粒包体具有岩浆混合的组构特征。因此,双朋西花岗闪长岩主要起源于下地壳高钾性玄武岩的部分熔融,并发生壳幔岩浆混合作用。对双朋西花岗闪长岩体及区内一系列侵入岩构造环境研究表明,西秦岭构造带在中三叠世处于由洋壳俯冲向陆陆碰撞转换阶段,俯冲板片的折返和断离引发地幔软流圈上涌,加热上覆下地壳发生部分熔融,产生长英质岩浆,形成大量中酸性岩体。
[Abstract]:The Shuangpenxi skarn type gold-copper deposit in the West Qinling orogenic belt is located in the Tongzhou-Zecu back-arc Foreland basin. The regional outburst strata are mainly Gan-Jia formation of the Lower Permian. Sedimentary rock series of the Lower Triassic Longwuhe Group. The intrusive rocks of the mining area are mainly granodiorite, and the gold orebody occurs in the granodiorite and the Gangjia formation marble. In the skarn of dolomite contact zone, zircon LA-ICP-MS U-Pb chronology and geochemistry of the Shuangpengxi granodiorite have been studied in this paper. The crystallization age of Shuangpengxi granodiorite is 233.9 卤2.8 Ma, which has the characteristics of high SiO2, high K2O2, low Al_2O_3 and MgO contents with a value of 33.635. 2, enriched with light rare earth elements (LREE), La / Sm / N ~ (3. 14) and 3. 14 ~ (11. 6) and large ion lipophilic elements. The distribution of heavy rare earth elements is flat and the distribution of heavy rare earth elements is flat, with moderate negative EU anomalies with relatively high initial Sr values Isr0.708299n 0.708748 and a relatively low 蔚 Ndft value of -12.66-9.474PbP / 20207PbP / 207PbP / 204Pb and 208PbP / 204Pb ratios of 18.623969 18.61010 15.61015.652 and 39.1240.42% NbTa5.5Nb-1 / 12.011.03.011.6), respectively, which are in agreement with the crustal composition. The dark granular inclusions in the rock mass are characterized by magmatic mixing. Therefore, the Shuangpengxi granodiorite originated mainly from the partial melting of high potassium basalts in the lower crust. The tectonic environment of the Shuangpenxi granodiorite and a series of intrusive rocks in the area shows that the West Qinling tectonic belt was in the transition stage from oceanic crust subduction to continental collision in the Middle Triassic. The upwelling of mantle asthenosphere caused by the exhumation and rupture of subduction plate resulted in partial melting of the crust covered by heating and the formation of felsic magma and formation of a large number of intermediate-acid rock masses.
【作者单位】：武警黄金地质研究所;中国地质大学地质过程与矿产资源国家重点实验室;
【基金】：国家自然科学重点基金项目(41030423) 中国地质调查局科外部科研项目(1212011220899);中国地质调查局地质调查工作项目(1212011220924) 高等学校学科创新引智计划(B07011)联合资助
【分类号】：P588.122;P618.41;P618.51

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