中国地质2017，Vol.44Issue(4)：722-736,15.DOI:10.12029/gc20170406
帕米尔地区穆尔尕布辉长岩-闪长岩的成因:锆石U-Pb年龄、Hf同位素及岩石地球化学证据
Petrogenesis of Murgab gabrro-diorite from Pamir:Evidence from zircon U-Pb dating, Hf isotopes and lithogeochemistry
摘要
Abstract
Located in the central part of Pamir, Tajikistan, near the Rushan-Pshart suture zone, the Murgab pluton separates the middle Pamir from southern Pamir. Petrologically, the pluton consists of gabrro and diorite which intruded into the epimetamorphic detrital rocks of late Proterozoic (?). LA-ICP-MS zircon U-Pb dating shows that the age of gabbro and that of diorite is 232±1.5 Ma and 231.5 ± 1.9 Ma respectively, which represents the formation age of this pluton. The εHf (t) values of the zircon are in the range of 4.8-12.1 and 6.4-10, with a weighted average of 8.1 ± 1.5 (MSWD=6.5) and 7.9 ± 0.8(MSWD=2.4), suggesting that its original rock was derived from mantle materials. The one-stage Hf model ages (TDM1) are 477-621 Ma, 391-672 Ma respectively indicating an original rock of Cambrian-Precambrian basement. The lithogeochemical data shows that gabbros are characterized by rich Mg and, poor Al and alkali, thus belonging to low-potassium rocks, whereas the diorites are rich in Si, Al and poor in Mg, Ti, hence belonging to calc-alkaline to high K calc- alkaline rocks. The gabbros and diorites share similar REE and trace elements features, which are characterized by high total REE content and rich LREE with slight normal Eu anomaly. The trace elements are characterized by rich LILEs and poor HFES. Based on geochemical characteristics, the authors infer that the pluton formed in an island-arc environment. The subduction was continuing during late Triassic, which indicates that the Rushan Ocean basin was closed at least later than 232 Ma.关键词
帕米尔/穆尔尕布岩体/LA-ICP-MS锆石U-Pb年龄/锆石Hf同位素Key words
Pamir/Murgab complex/zircon LA-ICP-MS U-Pb dating/zircon Hf isotopes分类
天文与地球科学引用本文复制引用
洪俊,计文化,张海迪,刘明义,马中平,李艳广,张辉善..帕米尔地区穆尔尕布辉长岩-闪长岩的成因:锆石U-Pb年龄、Hf同位素及岩石地球化学证据[J].中国地质,2017,44(4):722-736,15.基金项目
中国地质调查局项目(121201112036、12120114018601)资助.Supported by China Geological Survey Program (No. 121201112036, 12120114018601). （121201112036、12120114018601）
