Sr-Nd-Pb-Hf isotopic characteristics of ore-bearing granites in the Honghuaerji scheelite deposit, Inner Mongolia

Abstract: A study of whole-rock Sr-Nd isotopes, Pb isotopes of K-feldspar and Hf isotopic compositions of zircons from the ore-bearing granites in the Honghuaerji scheelite deposit was carried out in this paper. The results show that the average (87Sr/86Sr)i ratios of pink monzogranite, gray monzogranite and quartz monzonite are 0.70525, 0.70517 and 0.70482 respectively, displaying a decreasing trend; however, the average εNd(t) values are +2.2, +2.3 and +3.1 respectively, exhibiting an increasing trend. The Pb isotopic compositions of K-feldspar samples selected from pink and gray monzogranites are relatively uniform, with the 206Pb/204Pb ratios ranging from 18.258 to 18.276, 207Pb/204Pb ranging from 15.507 to 15.512 and 208Pb/204Pb ranging from 37.994 to 38.018. The εHf(t) values of zircons from the three samples are +5.2?+10.4, +3.1?+9.8, +5.8?+14.4 respectively. The Sr-Nd-Pb-Hf isotopic compositions show that the granites-forming materials might have been derived from a depleted mantle during Neoproterozoic. The quartz monzonite was likely the inclusion which was a product of magma mingling. The regional tectonic analysis indicates that the magma resources were probably related to the interaction between the ocean plate and the upper mantle during the closure of Paleo-Asian Ocean before Mesozoic Era; and after the disappearance of Mongolia?Okhotsk marine trough, the compression tectonic setting that had resulted from the collision of plates triggered the partial melting of the resources in early Jurassic epoch.