西天山特克斯达坂岩基解体的地球化学证据及钼找矿意义

Geochemical evidence for the "disintegration" of the Tekesi Daban batholith in the West Tianshan Mountain and its Mo-prospecting significance

西天山特克斯达坂岩基可解体为早石炭世库勒萨依序列和早二叠世其那尔萨依序列。库勒萨依序列为钙碱性岛弧斑岩组合,SiO2含量为57.06%-70.74%,σ值平均〈3.26,（Na2O＋K2O）/Al2O3〈0.9,高Al2O3、Na2O、Sr,相对富集LREE,低MgO、Y、Yb,亏损HREE,Na2O/K2O值大都〉1,Sr/Y平均值57.67,δEu平均1.22,具有典型O型Adakite岩特征,Cu、Mo、W等元素富集,已发现Mo矿体。其那尔萨依序列SiO2含量为76.75%-77.83%,σ值平均4.28,（Na2O＋K2O）/Al2O3〉0.9,δEu平均0.07,相对贫Ba、Sr、Ni、Sc,富Rb、Y、Zr、Th、Ta等,Sr/Y值平均3.24,属正常壳源板内裂谷碱性花岗岩类。地球化学特征不仅为这一岩基的解体提供了有力证据,而且对深化区域成矿规律、丰富构造岩石组合、指导进一步找矿和探讨本区大地构造演化均有重要意义。

The Tekesi Dahan batholith can be divided into two intrusive series, i.e., Early Carboniferous Kulesayi series and Early Permian Qinaersayi series. The porphyry assemblage of the Kulesayi series is a talc-alkaline series formed in an island arc environment. SiO2 is 57.06%-70.74%, the Rittmann index （σ） is lower than 3.26, and （Na2O ＋ K2O）/AlaO3 is lower than 0.9. It is enriched in Al2O3, Na2O, Sr and LREE, and poor in MgO, Y, Yb and HREE; Na2O/K2O is higher than 1, Sr/Y is 57.67, δEu is 1.22, indicating O-type adakite. The Kulesayi series is enriched in Cu, Mo and W, and even contains Mo ore bodies. In the Qinaersayi series, SiO2 is 76.75 %-77.83 %, σ is higher than 3.3, （Na2O ＋ K2O）/Al2O3 is higher than 0.9, and δEu is 0.07 ; this series is poor in Ba, Sr, Ni, Sc but enriched in Rb, Y, Zr, Th, Ta, with Sr/Y being 3.24. The protolith was partly derived from melting of argillaceous rocks of the earth crust, belonging to the alkaline series formed in an intraplate rift environment. Geochemical characteristics provide not only powerful evidence for the disintegration of the Tekesi Dahan batholith but also abundant information for the improvement of native metallogenic regularity. In addition, these characteristics enrich types of tectonite assemblage, guide oreprospecting work and contribute to researches on tectonic evolution.