祁漫塔格印支期铝质A型花岗岩的确定及初步研究  

Determination and preliminary study of Indosinian aluminous A-type granitesin the Qimantag area, southeastern Xinjiang

作　　者：陈丹玲[1] 刘良[1] 车自成[1] 罗金海[1] 张云翔[1] 

机构地区：[1]西北大学大陆动力学教育部重点实验室,西北大学地质学系,陕西西安710069

出　　处：《地球化学》2001年第6期540-546,共7页Geochimica

基　　金：国家"九七三"项目(G1999075508);国家自然科学基金(49972063);西北大学校内基金

摘　　要：祁漫塔格小红山印支期钾长花岗岩的岩石化学成分为过铝质(A/NKC介于1.03～1.06之间),高硅(SiO2>76%),偏碱性(ALK=7.77%～8.22%),K2O>Na2O,FeOT/MgO比值高(9.4～21.7),CaO、MgO、TiO2和P2O5含量低(分别为<0.78%,≤0.14%,≤0.1%和≤0.02%)。岩石富Rb、Th、U、Y、Zr、Nb和Hf,贫Sr、Ba、Eu、Cr和Ni,Ga/Al比值高,明显不同于I型和S型花岗岩,显示了铝质A型花岗岩的特征,形成于造山后的伸展环境。该A型花岗岩的确定证明了祁漫塔格地区晚三叠世之前碰撞造山作用的存在,以及祁漫塔格与东昆仑造山带的亲缘性。Xiaohongshan intrusive in Qimantag Mountain, southeastern of Xinjiang, mainly consists of potash feldspar granites. The major component of Xiaohongshan intrusive is peraluminous (A/NKC=1.03～1.06, with an average of 1.05) and is characterized by high silica content (SiO2 >76%), high alkaline (K2O+Na2O= 7.77%～<IMG SRC='IMAGE/01170013.JPG' HEIGHT=11 WIDTH=33>8.22%), rather high ratio of FeOT/MgO (9.4～21.7), low content of CaO, MgO, TiO2 and P2O5 (<0.78%, ≤0.14%, ≤0.1%and ≤0.02%, respectively). The trace element and REE compositions show the feature of high quantity of REE, Rb, U, Th, Y, Zr, Nb,Hf, Yb, depletion of Eu, Ba, Sr, Cr, Ni, and the ×Ga/Al ratios, changing from2.72 to 3.24, are obviously higher than that of I and S type granites average (2.1 and 2.28, respectively). These characteristics are quite similar to those of typical A type granites such as Mumbulla granitoid and alumious A typegranites in the coastal area of Fujian Province. Evidences from petrology and geochemistry and discrimination diagrams, Nb Y Ce triangle diagram as well asR1 Ga/Al, all show that the Xiaohongshan granite falls into aluminous A2 type granites. According to the R1 R2 diagram Xiaohongshan intrusive was formed under the tectonic setting of post orogenic extension. Xiaohongshan intrusive,of which an Rb Sr isochron age of (212±7) Ma is obtained, was formed duringthe period of Later Triassic, and was consistent with A type granite outcropping widely in the East Kunlun orogenic belt and the rhyolite outcropping widely in the southern margin of the Qaidam massif. Therefore, the determination of Xiaohongshan A type granite in Qimantag shows that Qimantag tectonic belt, formedby the collision, was one part of the East Kunlun orogenic belt.

关 键 词：A型花岗岩 地球化学 构造环境 柴达木地块 成因 岩相学 碰撞造山作用 

分 类 号：P588.121[天文地球—岩石学]