摘要
新疆东准噶尔卡拉麦里地区是一个重要的锡成矿带,分布有多种类型花岗岩,其中黑云母花岗岩长期以来被认为是S型花岗岩。本文研究表明,苏吉泉黑云母花岗岩富集Rb、K等大离子亲石元素及Zr、Hf等高场强元素,其FeO/MgO和10000Ga/Al值大,明显不同于典型的I型和S型花岗岩,属于典型的铝质A型花岗岩。锆石的LA-ICPMSU-Pb定年结果显示其形成时代为304±2Ma,比该区钙碱性花岗岩侵位晚,而与碱性花岗岩形成时代相近。这些黑云母花岗岩具有高εNd(t)的同位素特征,但它们不是直接来源于亏损地幔,而更可能是源自地幔且被深埋的年轻地壳物质部分熔融和结晶分异作用的产物。花岗岩微量元素构造判别图显示它们是一种后碰撞花岗岩,标志晚石炭世卡拉麦里地区造山作用的结束和板内构造演化的开始。
Several types of granites are distributed in Karamaili area of East Junggar, Xinjiang, which constitutes an important tin metallogenic zone. Biotite granites there have long been thought to be of S-type. Nevertheless, the study conducted by the authors shows that biotite granites in Sujiquan are actually typical aluminous A-type granites characterized by enrichment of LILE （such as Rb, K） and HFSE （such as Zr, Hf） as well as high FeO/MgO and 10 000 Ga/Al ratios. These features are obviously different from those observed for Ⅰ- and S- type granites. Zircon U-Pb dating by LA-ICPMS shows that they were emplaced at about 304± 2Ma, close to the formation time of alkaline granites but later than the emplacement of calc-alkaline granitoids in this area. Although these biotite granites possess high εNd（ t ） values, they were not derived directly from a depleted mantle, but were most likely formed by partial melting of mantle-derived juvenile crustal materials which were subjected to deep burial and magmatic fractional crystallization. Trace element tectonic discriminant diagrams for granites reveal that biotite granites belong to post-collision granitoids, which marked the end of orogenic movement and the beginning of the intraplate evolution in Karamaili of East Junggar in late Carboniferous.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2006年第3期175-184,共10页
Acta Petrologica et Mineralogica
基金
中国科学院西部之光项目(2002年度)
国家重点基础研究发展规划项目(2001CB409805)
