西天山那拉提构造—岩浆岩带石炭纪花岗岩岩石地球化学特征及侵位机制探讨

LITHOGEOCHEMICAL FEATURES AND EMPLACEMENT OF THE CARBONIFEROUS GRANITE IN THE NALATI STRUCTURE-MAGMATITE ZONE OF WESTERN TIANSHAN MOUNTAIN

中天山那拉提构造—岩浆岩带石炭纪岩浆活动非常发育,中性岩、酸性岩均有不同程度的出露。通过地质调查研究,划分出2个序列,6个期次。岩石组合及岩石地球化学研究表明,细粒石英闪长岩、英云闪长岩、中粒花岗闪长岩组合为混源序列,其岩浆主要来源于地壳和地幔,属"I"型花岗岩;中粗粒二长花岗岩、中粒斑状二长花岗岩、中细粒二长花岗岩组合岩浆主要来源于地壳,属"S"型花岗岩。它们显示碰撞环境特征,是俯冲阶段岛弧环境产物,总体呈中性—酸性的演化规律,反映出以强力就位为主的地质特征。

The Carboniferous magmation in the Nalati structure-magmatite zone of Western Tianshan Mountain is well developed with intermediate rock and acidic rock outcropping in different degrees.Geological survey at 1：50,000 in the mineralized areas around Xinyuan forest management area has distinguished two sequences of mixed source and crustal source,from which 6 phases are divided further.Rock association and lithogeochemical studies have indicated that fine-grained quartz diorite,tonalite and mesograined granodiorite associations are attributed into the mixed sources and the major source of magma was from earth crust and mantle,belonging to products formed by subduction under island-arc setting.The association by mesograined monzogranite,mesograined porphyritic monzogranite and mesogrined-finegrained monzogranite formed the crustal source and the magmatite was mainly from earth crust,belonging to ＂S＂-type granite and showing a collision setting.The general evolution of the Carboniferous magma present from neutrality to acidity evolution,reflecting geological feature with forceful emplacement.