摘要
小柯勒河钼铜矿床位于额尔古纳地块和兴安地块的结合部位,是近年来大兴安岭北部新发现的斑岩型矿床。为确定该矿区内二长岩的形成时代、岩石成因、岩浆源区及构造背景,对其进行了锆石U-Pb定年及全岩分析。锆石U-Pb定年结果显示:二长岩形成于57.8 Ma±0.3 Ma(MSWD=2.0),为古新世。全岩分析结果显示:二长岩具有低镁(w(MgO)为1.89%~2.06%)和高碱(w(K_(2)O+Na_(2)O)为8.02%~8.68%)特征,属于准铝质、钾玄岩系列岩石;富集大离子亲石元素(Rb、Ba、K),亏损高场强元素(Nb、Ta、Ti),与俯冲带岩浆岩特征一致;具有低镁指数(Mg#为35.07~36.46)、钴(w(Co)为9.80×10^(-6)~11.66×10^(-6))和镍(w(Ni)为1.22×10^(-6)~3.25×10^(-6))特征,较高的w(La)/w(Nb)值(1.87~2.97)、w(Th)/w(La)值(0.21~0.28)、w(Th)/w(Nb)值(0.43~0.66),与壳源岩浆岩特征相似,应是下地壳基性变质岩部分熔融的产物。结合前人区域构造背景的研究成果,认为二长岩形成于太平洋俯冲板块向后回撤引起的区域伸展构造背景下。
The Xiaokelehe Mo-Cu Deposit is a porphyry deposit newly discovered in the north of Greater Khingan Mountains in recent years and is located at the junction of Erguna massif and Khingan massif.In order to determine the chronology,petrogenesis,magma source and tectonic settings of the monzonite in the area,zircon U-Pb dating and whole rock analysis of the monzonite is conducted.The zircon U-Pb dating results show that the monzonite yields a Paleocene age,that is 57.8 Ma±0.3 Ma(MSWD=2.0).The whole rock analysis results show that the monzonite is characterized by low Mg(w(MgO)is 1.89%-2.06%)and high alkali(w(K_(2)O+Na_(2)O)is 8.02%-8.68%)concentrations,indicating it is aluminous and shoshonite rock;the samples are rich in LILEs(Rb,Ba,K),depleted in HFSEs(Nb,Ta,Ti),consistent with the magmatic characteristics of subduction zone;they have low Mg#(35.07-36.46),Co(w(Co)is 9.80×10^(-6)-11.66×10^(-6))and Ni(w(Ni)is 1.22×10^(-6)-3.25×10^(-6)),and relatively high ratios of w(La)/w(Nb)value(1.87-2.97),w(Th)/w(La)value(0.21-0.28)and w(Th)/w(Nb)value(0.43-0.66),similar to the characteristics of crustal magmatic rocks,which is supposed to be the product of partially melting of the basic metamorphic rocks in the lower crust.Based on the previous research results of regional tectonic setting,it is considered that the monzonite formed in the regional extensional tectonic setting caused by the withdrawal of the Pacific subduction plate.
作者
于涛
李雪梅
于润涛
李治华
孙永刚
姜芷筠
Yu Tao;Li Xuemei;Yu Runtao;Li Zhihua;Sun Yonggang;Jiang Zhijun(College of Earth Sciences,Jilin University)
出处
《黄金》
CAS
2021年第6期11-19,共9页
Gold
基金
吉林省自然科学基金项目(20180101089JC)
吉林省科技发展计划重点项目(20100445)。
