准噶尔东部早志留世两类花岗岩的岩石成因及构造意义

哈尔里克山西段早志留世二长花岗岩和正长花岗岩呈北西西向带状展布，侵入奥陶系塔水组（O_1-2t），LA-ICP-MS锆石U-Pb年龄为438.8±2.3~435.8±3.1 Ma。岩石高硅（SiO₂含量73.0%~77.8%）、富钾（K₂O含量3.31%~4.26%）、低镁（MgO含量0.03%~0.59%），铝饱和指数A/CNK值1.02~1.08，属高钾钙碱性弱过铝质岩石。二长花岗岩轻重稀土分馏显著，Eu异常中等，亏损Nb、Ta、Ti、P，富集Rb、Ba、K，表现为分异的Ⅰ型花岗岩特征，源区为基性下地壳；正长花岗岩强烈亏损Eu、P、Ti、Sr，不同程度富集Rb、K、Zr、Hf，表现为A型花岗岩特征，其源区为缺水的浅部长英质地壳。结合区域地层不整合资料，认为东准噶尔地区早志留世为后碰撞环境而非岛弧带，后碰撞软流圈上涌带来的热熔融准噶尔年轻地壳形成了岩性丰富的东准噶尔志留纪后碰撞岩浆岩组合。 

PETROGENESIS AND TECTONIC IMPLICATIONS OF TWO TYPES EARLY SILURIAN GRANITES IN EAST JUNGGAR

The early Silurian monzogranite and syenogranite are located in the western section of Harlik Mountain with a NWW-trending, which intrude into the Ordovician Tashui Formation (O_1-2t). The LA-ICP-MS zircon U-Pb dating shows their emplacement ages are 438.8±2.3 Ma~435.8±3.1 Ma. The rocks have high contents of silicon (SiO₂=73.0~77.8%)and potassium (K₂O=3.31~4.26%), and low contents of magnesium (MgO=0.03~0.59%), with moderate aluminum saturation index (A/CNK=1.02~1.08), which show that the rocks are high-K calc-alkaline, weakly peraluminium series. Monzogranites exhibit strongly fractionated REE patterns with moderate negative Eu anomalies, and they are depleted in Nb, Ta, Ti, P, but enriched in Rb, Ba, K, showing notable fractionated I-type granitoids with mafic lower continental crust as a potential magma source. Syenogranites show remarkably depletion of Eu, P, Ti and Sr, and enrichment of Rb, K, Zr and Hf, showing A-type granites affinity, whose magma source maybe the dehydrated felsic upper continental crust. Combined with the stratigraphic unconformity in this region, we propose that the East Junggar is in a post-collisional setting rather than arc-related setting during the early Silurian. The upwelling asthenosphere provided enhanced heat flux and triggered the partial melting of the juvenile crust, and resulted in the generation of various Silurian post-collisional granites in East Jungga.