西准噶尔乌尔喀什尔山库鲁木苏序列A型花岗岩地球化学特征及地质意义

Geochemistry of the Kulumusu A_type granite series in Wuerkashier, West Junggar, and its geological significance

西准噶尔乃至整个北疆地区广泛发育晚古生代后碰撞花岗岩类。作为其中的一部分,乌尔喀什尔山一带库鲁木苏岩基中的库鲁木苏序列主要由二长花岗岩、细粒正长花岗岩、中粗粒正长花岗岩、碱长花岗岩和碱长花岗斑岩组成。该序列富硅（Si O2=70.78%-76.85%）、富碱（K2O＋Na2O=7.87%-9.71%）、低钛（Ti O2=0.08%-0.41%）、贫钙（Ca O=0.16%-1.42%）,为准铝质至强过铝质（ACNK=0.98-1.15）;稀土元素配分曲线为典型的＂V＂字型,具有明显的负Eu异常;微量元素特征显示富集大离子亲石元素（Rb、Th、K）及高场强元素（Zr、Hf）,而强烈亏损Ba、Sr、P、Eu和Ti。以上特征表明库鲁木苏序列为A2型花岗岩,结合区域构造演化,认为库鲁木苏序列形成于后碰撞环境。

Late Paleozoic post-collisional granitoid intrusions are extensively developed in West Junggar and even in the whole northern Xinjiang. The Kulumusu series of Kulumusu batholith in the Wuerkashier of West Junggar,which is one of these intrusions, mainly comprises monzogranite, fine-grained syenogranite, middle-coarse-grained syenogranite, alkali feldspar granite and K-feldspar porphyry. The Kulumusu series is characterized by high silica（ SiO2= 70. 78% - 76. 85%）, alkali（ K2O ＋ Na2O = 7. 87% - 9. 71%）, and low titanium and calcium（ TiO2=0. 08% - 0. 41%, CaO = 0. 16% - 1. 42%）, thus belonging to metaluminous to strongly peraluminous series（ ACNK = 0. 98 - 1. 15）. The rocks display ＂V＂-shaped REE patterns, and are evidently depleted in Eu. They are enriched in light rare earth elements（ Rb, Th, K） and high strength field elements（ Zr, Hf）, and significantly depleted in Ba, Sr, P and Ti. These features indicate that the Kulumusu series belongs to A2-type granite. In combination with the tectonic evolution of this region, the authors hold that the Kulumusu series was formed in a post-collisional tectonic setting.