巴颜喀拉沉积盆地基底为扬子地台西缘的一部分：来自花岗岩的证据

侵入于巴颜喀拉沉积盆地中的扎加岩体，主要由高钾钙碱性的黑云母花岗岩组成，并出现有具岩浆结构的暗色微粒包体。花岗岩富集轻稀土（LREE）及大离子亲石元素（LILE），相对亏损重稀土（HREE）和高场强元素（HFSE），具Eu负异常（0．5～0．7）、较低的εNd（t）值（-3．5～-6．2）和中等的（^87Sr／^86Sr）初始比值（0．7088～0．7090），它们的亏损地幔Nd模式年龄tDM在1．1～1．3Ga之间。与寄主花岗岩相比，闪长质暗色微粒包体具有较低的SiO2，更低的Eu负异常（0．2～0．4）和εNd（t）值（-4．7～-6．1），更高的（^87Sr／^86Sr）初始比（0．7084～0．7124），以及稍老的tDM（1．4Ga）。岩石的地球化学资料表明，扎加花岗岩是在碰撞后构造环境下幔源岩浆上涌诱发下地壳岩石部分熔融的产物，其物源可能是苦海杂岩和万宝沟岩群的混合物。巴颜喀拉沉积盆地下面存在中元古代的基底，属于扬子地台西缘的一部分

The Basement of Baryan Har Basin Is A Part of Western Yangtze Platform: Evidence from Granites

The Zhajia pluton, emplaced in the Triassic Baryan Har sedimentary basin on the northeastern margin of the Tibet-Qinghai Plateau, consists of high-K calc-alkaline biotite granites. Mafic microgranular enclaves with magmatic textures are also present in the pluton. The granites are characterized by enriched LREE and LILE, and depleted HREE and HFSE. They have moderate negative Eu anomaly （0.5 -0.7）, low end （t）（ -3.5 - -6.2）and moderate initial （87Sr/86Sr） ratios （0.7088 -0. 7090）, and their depleted mantle model ages （tDM） range from 1.1 to 1.3 Ga, while mafic enclaves have lower SiO2 contents, lower end （t） （ - 4. 7 - - 6. 1 ）, higher initial （^87Sr/^86Sr） ratios （0. 7084 -0.7124） and older tDM （1.4 Ga） than the host granites. It is suggested that the early Jurassic Zhajia pluton was formed in post-collisional setting, and granitic magma of the pluton was generated by par- tial melting of the lower crust as a result of the intrusion of mantle-derived magma. The sources of granitic magma might be the mixture of Precambrian Kuhai complex and Wanbaogou group occurring in Kunlun orogenic belt. It seems that there is a Middle Proterozoic basement beneath the Baryan Har sedimentary basin, and the basement is a part of the Western Yangtze platform