Abstract:

Weilasituo Cu polymetal deposit is located in the west of middle-southern metallogenic belts in Great Xing’an Mountains of Inner Mongolia. In order to constrain the forming tectonic setting of the deposit, this paper analyses the major and trace elements and Sr-Nd-Pb isotopic compositions of the granitoid rocks. The granitoid rocks are composed of granites, monzonitic granites and diorites, and these granitoid rocks are calc-alkali rocks. The granites and monzonitic granites are rich in SiO₂, and characterized by high REE, middle negative Eu, relatively lower partition of HREE, strongly enriched in LILE, and depleted in HFSE. The (⁸⁷Sr/⁸⁶Sr)t (0.705 93-0.710 75) and ε_Nd(t) (-4.45--0.63) values suggest that the rocks are highly fractionated I-type granites. The primary magma for granitic rocks could be mainly derived from partial melting of the deep crust, which may be related to Xilingele complex. The diorites are rich in Mg，Cr，Ni, slightly negative Eu, with geochemical features of analogous to sanukite. The results indicated that the magma was derived from enriched mantle metasomatized by slab-derived fluids or melts. By combining with comprehensively analyses of the tectonic settings, we suggest that the Weilasituo granitoid rocks were formed in a post-collisional tectonics

Key words: Weilasituo deposit, granitoid rock, geochemistry, Sr-Nd-Pb isotopes, Inner Mongolia