ZIRCON SHRIMP AGE AND GEOCHEMISTRY OF CAIZHONG GRANITE FROM EAST TIANSHAN, XINJIANG, CHINA

Abstract

SHRIMP U-Pb age for zircons, major and trace elements and Nd-Sr isotopic compositions for biotite monzonitic granite of Caizhong in Kangguertage area in eastern Tianshan of the Xinjiang are studied in this paper. A 206Pb/238U weighted mean age of 316 ± 4(2σ) Ma for zircons was gained, presenting the time of emplacement of the Caizhong biotite monzonitic granite. This result indicates that the Caizhong biotite monzonitic granite was formed during early period of Late Carboniferous, which modified uncertainty age that considered Caizhong granite as a intrusion of late of Early Permian. Based on analyses of major and trace elements, Caizhong granite has characteristics of metaluminous and calc-alkaline granite, showing their formation in island arc setting. The Caizhong granite has high values of εNd(t) from + 8.5 to + 7.4 and low 87Sr/86Sr ratios (ISr = 0.7034-0.7036), implying its protolith derived from depleted mantle source. Younger Nd model ages of TDM from 0.38 to 0.47 Ga suggest that source of its protolith scarcely was contaminated by older crustal materials. Summarized all results, it is indicated that the Caizhong granite has characteristics as similar as those of granites from the eastern and western Junggar orogen.