科研之友
微信
新浪微博
Facebook
分享链接
摘要
Secondary-ion mass spectrometric U-Pb age (324.8-323.1 Ma) and δ18O and laser-ablation multi-collector ICP-MS εHf(t) of zircons, mineral chemistry and whole-rock geochemistry and Nd-Sr isotopes of the Carboniferous intrusive complex of Hadanxun were analyzed in this study in order to expound the mechanism of arc magma generation and decipher high P-wave velocity body in the middle crust of Northeast Junggar. Their rare earth element distribution patterns are concave-up. The major and trace element variations from diorite (with entrained hornblendite cumulate) to monzogranite, with decreasing Dy/Yb and primitive-mantle normalized NbN/TaN, can be reproduced with quantitative modeling of fractional crystallization of hornblendite (Stage 1) and feldspar-dominated minerals (Stage 2). They exhibit high Sr/Y, low Y and mean zircon δ18O of 6.42‰, suggesting derivation from subducting oceanic-slab. Al-in-hornblende barometer reveals that the hornblendite cumulate (population 1: 26-22 km depth; population 2: 20-18 km) constitutes high P-wave velocity body in the middle crust of Northeast Junggar. The Carboniferous intrusive complex of Hadanxun exhibits high positive zircon εHf(t) (weighted mean=12.99) and depleted εNd(t) (6.22-6.55) and (87Sr/86Sr)i (0.703 7-0.704 0), precluding oceanic crust and continental-crustal materials from Chinese Altay as source component. Thus, the Northeast Junggar was an intra-oceanic arc and the oceanic-plate subduction continued until the Carboniferous.
- 单位
