西天山克孜勒扎依劳岩基地球化学特征

克孜勒扎依劳岩基位于新疆阿拉山口西侧,为石炭纪混源序列花岗岩,包括8个侵入序次.主元素地球化学特征是,由较早序次至较晚序次,SiO2和(K2O+Na2O)含量有逐渐增加的趋势;而Mg、Fe、Ca和TiO含量有逐渐减少的趋势.微量元素中,亲铁元素、亲铜元素和亲石元素在岩浆演化过程中各有不同的演化规律.总体来看,大半径亲石元素相对富集,而高场强元素相对亏损.稀土元素特征是其总量自早至晚有逐渐增加的趋势,轻稀土相对富集,而重稀土相对亏损.轻稀土具有较强的分馏作用,而重稀土分馏作用较弱.岩石地球化学资料综合分析显示,由较早序次至较晚序次,侵位深度越来越浅;岩浆的物质来源主要为玄武岩浆分异,主体具有I型花岗岩特征;较早序次形成于阿拉套晚古生代陆缘盆地拉张-聚合阶段,较晚序次形成于阿拉套晚古生代陆缘盆地之闭合-碰撞阶段.

GEOCHEMICAL CHARACTERISTICS OF THE KEZILEZHAYILAO BATHOLITH IN WEST TIANSHAN

The Kezilezhayilao batholith, located~in the west of Alataw Pass in Xinjiang, belongs to Carboniferous mixed source sequence granite, including eight intrusive sequences. Geochemically, the contents of SiO2 and KzO＋Na20 tend to increase gradually from early to late sequences, while those of Mg, Fe, Ca and TiO tend to decrease. Among trace elements, the siderophile, chalcophile and lithophile elements each have different evolutional laws in the evolution process of magma. In general, major radius lithophile elements are relatively concentrated while high field strength elements are relatively depleted. The total amount of rare earth elements tends to increase from early to late sequence, with LREE enriched and HREE depleted relatively. The fractional distillation of LREE is strong while that of HREE is relatively weak. Comprehensive analysis of lithogeoehemical data suggests that the emplacement depth becomes shallower from early to late sequence. The source of magma is mainly from basaltic differentiation, mostly with characteristics of I- type granite. The early sequences were formed in the extension-convergence stage of the Late Paleozoic Alataw continental margin basin; while the late sequences, in the closure-collision stage.