关键词: 中天山地块, 星星峡群, 地球化学, 构造背景, 变质条件

Abstract: The Central Tiansan Block is an important part of the Chinese Tianshan Orogenic Belt, and the formation age of Precambrian basement in the Central Tianshan Block becomes older as it goes east. The Xingxingxia Group is located in the easternmost of the Central Tianshan Block and has the oldest Precambrian basement of the Chinese Tianshan Orogen. In this paper, the metamorphic schist and gneiss in the Xingxingxia Group were observed and sampled in the field, and thin section observation, mineral electron probe analysis and whole-rock geochemistry test were carried out in the laboratory. The geochemical analysis of the whole rock major element indicates that the protoliths of the metamorphic schist and gneiss in the Xingxingxia Group are mainly argillaceous rocks and sandstone. The results of trace elements and REE indicate that the Xingxingxia Group was deposited in continental arc or active continental margin environment based on the results of EPMA and major elements. The temperature and pressure conditions of the peak metamorphism of the Xingxingxia Group were 610-730℃ and 6.8-8.5 kbar. In addition, according to the latest metamorphic age of the basement rock, the time of peak metamorphism of the Xingxingxia Group is about 380 Ma.

Key words: Central Tianshan Block, Xingxingxia Group, geochemistry, tectonic setting, metamorphic condition