关键词: A型花岗岩；裂谷作用；博格达裂谷；卡拉麦里蛇绿岩带

Abstract:

The Sujishan granite, formed at Balikun, Xinjiang province, is a ferro-edenite alkali-feldspar granite, locating tectonically at
the eastern segement of the Bogda orogenic belt. Containing high contents of SiO2, K2O+Na2O, NK/A and low content of Al2O3, it
invariably exhibits light rare earth elements (LREE) enrichment with weak negative Eu anomalies and enrichment of LILE and HFSE
with the depletion of Cs, Sr, P, Ti. The element combinations of high HFSE (Zr+Nb+Ce+Y) range from 451×10-6 to 674×10-6 and
zircon-saturation temperature lies within 841℃ to 883℃. These characteristics show that it belongs to A-type granite, and specifically

most of the samples fall into the range of A2-type granite according to the discrimination diagrams. The amphibole as rock-forming
mineral belongs to calcic amphibole group, ferro-edenite hronblende subgroup, which is characterized by Al2O3 2.9%~4.5% and Si/(Si+
Ti+A1) 0.88~0.93, implying a crustal source. The zircon LA-ICP-MS U-Pb dating analysis suggests the emplacement age of Sujishan
granite is ca. 301.5±2.4Ma, which belongs to the Gzhelian stage of the late Carboniferous. Sujishan A-type granite with crustal-derived
amphiboles differs from A1-type granitoid representing a stretching mechanics related with mantle plume or rifting. Additionally, the
emplacement time at middle and late of rifting differs from A2-type granitoid formed at a post-orogenic tectonic stage. In combination
with granites emplaced at adjacent region, the Sujishan A-type granite marked a limited stretching mechanics related with rifting,
which may be the product of oblique subduction of the paleo-Asian Ocean plate along the Kalameili subduction belt .

Key words: A-type granite, rifting, Bogda rift, Kalameili ophiolite belt