The study of Early-Paleozoic peraluminous granite (SP) and its tectonic significance in the Xingxingxia suture zone, eastern Tianshan Mountains, Xinjiang, northwest China

Abstract

The Qianluzi granite intruded along the Xingxingxia fault at the south margin of the central Tianshan Mountains. The granite is characterized by high absolute Si, Al and K, whereas low Mg, Fe contents, K 2O>Na 2O, A/CNK > 1.1, is high K calc-alkaline peraluminous granite(SP). The rocks also are characterized by relatively low CaO/Na 2O(0.06 ̃ 0.07) and Al 2O 3/TiO 2 (48.9 ̃ 55.3)ratios; high REE, Nb and Y abundance, enriched LREE and LILE(Rb, U, Th, K); strongly depleted Ba, Sr P, Ti, Eu and HREE; relatively high zircon Hf isotopic(ε Hf(t) = -2.3 ̃ +1.6) ○ These characters indicate the Qianluzi granite is the post-collision granite; the source rocks are mud-rocks which are the mixtures matters that origin from the whethering of the growth crust and the old crust; is recycle of the accretionary crust. In the post-collision strike-extension setting, the mantle raised along the fault and lead partial-melting of the mud rocks. The Zircon U-Pb dating by LA-ICPMS shows that its crystallization age is 444.5 ± 2.2 Ma, in the late Ordovician, limits the collision time of the central Tianshan tarrane and the Gongpoquan arc. Summary, the Qianluzi peraluminous granite(SP) is the result of the collision between the central Tianshan terrane and the Gongpoquan Tarrane, and is the one of the results of the crustal growth in the Central Asian Orogeny Belt.