Abstract:

The granitoid rocks in Alatage, located in southern margin of central Tianshan plate in Daheishan area, are mainly composed of granodiorite, adamellite and porphyaceous granite. The granites are characterized by high SiO₂(66.29%-77.47%), high Na₂O+K₂O (6.75%-9.93%), high Al₂O₃ (10.97%-14.40%), and low Sr((28.78-153.00)×10^-6, averaging 99.23×10^-6) , and low TiO₂（0.09%-0.77%). The comprehensive analysis suggests that the granites are peraluminous calcalkalic series rocks(A/CNK=1.19-1.50); REE analysis shows that the averaged ∑REE is 362.04×10^-6, the ratios of LREE/HREE and (La/Yb)_N are 6.80-8.45，6.06-9.03 respectively. The REE distribution patterns show that the granites are enriched in LREE and depleted in Eu; the trace elements distribution patterns show that the granites are enriched in Rb, Th, K, Hf and Zr（LILE）except Ba, and depleted in Nb, Ta, P and Ti（HFSE）, especially depleted in Sr. Y-Nb, Y+ Nb-Rb and R₁-R₂ diagrams and Sr, Nd isotopic comprehensive analyses indicate a tectonic setting of post collision. The granites belong to granite complexes with mixed origin and multiple stages of intrusion.

Key words: eastern Tianshan, Alatage, geochemistry, tectonic significance, granitoid