新疆东天山地区三岔口铜矿床的成因:岩石学、年代学和地球化学证据

发布时间：2018-05-18 20:30

  本文选题：岩石地球化学 + O型埃达克岩　； 参考：《矿物岩石》2017年04期

【摘要】：三岔口铜矿床位于新疆东天山大南湖岛弧带的东北缘。目前对于三岔口铜矿床的成因类型及成矿年代还存在争议。三岔口铜矿床中赋矿岩体为闪长岩-花岗闪长岩,发育黑云母化、硅化、绢英岩化、青磐岩化等。测得三岔口铜矿床辉钼矿Re-Os年龄为416Ma±6.4 Ma,含矿闪长岩中锆石LA-ICP-MS U-Pb年龄为425 Ma±3.9 Ma,反映该矿床形成于中志留世。矿区内闪长岩-花岗闪长岩w(Na_2O+K_2O)为3.88%~4.68%,A/NCK值均大于1,为铝饱和岩石。岩体贫钾(w(K_2O)0.47%~1.18%)富钠(w(Na_2O)_2.83%~4.23%),w(TiO_2)偏低(0.41%~0.46%),多属于低钾拉斑系列。岩体富集w(Ba)(260×10~(-6)~4 810×10~(-6)),w(Sr)(644×10~(-6)~797×10~(-6))等大离子亲石元素,亏损w(Nb)(2.1×10~(-6)~2.6×10~(-6)),w(Ta)(0.1×10~(-6)),w(Zr)(11.2×10~(-6)~13.1×10~(-6))等高场强元素,具岛弧岩浆岩的特征。岩体富Na贫K,K_2O/Na_2O0.42,且具有高w(Al_2O_3)(≥16.65%),w(SiO_2)(≥61.3%),w(Sr)(≥644×10~(-6))以及较低的w(Y)(≤13.7×10~(-6))和w(Yb)(≤1.41×10~(-6)),具O型埃达克岩的特征,表明三岔口铜矿床形成于俯冲岛弧环境。结合研究区域内铜(钼)矿床的成矿时代及矿床类型,得出东天山地区有三期斑岩型矿床成矿作用:志留纪的三岔口、玉海斑岩型铜矿床,石炭纪的土屋-延东、延西等斑岩型铜矿床,以及三叠纪的东戈壁、白山斑岩型钼矿床。
[Abstract]:Sanchakou copper deposit is located in the northeast margin of the Dananhu island arc belt in East Tianshan, Xinjiang. At present, the genetic type and metallogenic age of Sanchakou copper deposit are still controversial. The ore-bearing bodies in Sanchakou copper deposit are diorite-granodiorite, biotite, silicitization, sericite, Qingiranlitization, etc. The Re-Os age of molybdenum is 416Ma 卤6.4 Ma. and the LA-ICP-MS U-Pb age of zircon in diorite is 425 Ma 卤3.9 Ma, which indicates that the deposit was formed in the Middle Silurian. W(Na_2O K _ 2O) of diorite-granodiorite in the ore area is 3.88 and 4.68 and the value of A- / NCK is all greater than 1, which is aluminum-saturated rock. The rock mass is low in potassium content (0.47 / 0.47 / 1.18) and in the Na / S / Na _ 2O _ 3 / 2.83 / 2.83 / 4.23T / w _ 2O _ 2) low 0.41 / 0.46 and 0.46 / 0.46, mostly in the low K _ 2O _ 3 series. The rock mass is rich in large ion lithophile elements, such as w(Ba)(260 脳 10 ~ (10) ~ (-6) ~ (4) 10 ~ (10) ~ (10) ~ (6) ~ (6), etc., and is characterized by high field and strong elements, such as w(Nb)(2.1 脳 10 ~ (10) -6 ~ (6) ~ (2. 6 脳 10 ~ (10) ~ (6) ~ (1) ~ (10) ~ (10) ~ (-6) ~ (1) ~ (11) 脳 10 ~ (10) ~ (1) ~ (1) ~ (1) ~ (1) ~ (1) ~ (1) ~ (1 脳 10 ~ (10) ~ (6) ~ (), and is characterized by the characteristics of the island arc magmatic rocks. The rock body is rich in K _ 2O / Na _ 2O _ (0.42), and has the characteristics of high wtiao _ 2o _ 3 (鈮，

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