The petrological and geochemical characteristics of the Zhamashi mafic complex, Qilian Mountain and their tectonic implications
祁连山扎麻什基性杂岩体岩石地球化学特征及其大地构造意义

The Zhamashi mafic complex in Qilian County, Qinghai province, intruded into Cambrian-Ordovician strata, is mainly composed of gabbro with ultramafic rock, pyroxenite, hornblendite and diorite. Petrological and geochemical studies suggest that the complex is derived from a calc-alkalic magma by crystallization with different degree. The rocks are enriched in LILE and depeleted in HFSE, with clearly Nb and Ta negative anomalies. Combined with the spatial relationship between the complex and the northerly Qingshuigou-Baijinshi subduction complex, we conclude that the Zhamashi complex formed in an island arc setting, and may be as product of southward subduction of North Qilian ocean crust to the north.