地质学报2017，Vol.91Issue(6)：1192-1207,16.
西昆仑甜水海地块南屏雪山早古生代花岗岩地球化学、Hf同位素特征及其壳幔岩浆作用
Geochemistry and Hf Isotopic Compositions of Early Paleozoic Granites in Nanpingxueshan from the Tianshuihai Terrane,West Kunlun: Crust-Mantle Magmatism
摘要
Abstract
The Early Paleozoic granite in Nanpingxueshan in the eastern part of the Tianshuihai terrane,West Kunlun,consists of medium-grained porphyritic biotite-quartz monzonite (485Ma) and medium to finegrained biotite-quartz monzonite (528Ma).Chemically,the two rocks are enriched in Si and alkali,and depleted in TFe2 O3,MgO and CaO,thus suggesting that they can be grouped into high-K calcalkaline and weakly peraluminous granitoids.In terms of trace elements and rare earth elements,the two granites are enriched in Rb,Th,U,K,Pb and LREE,depleted in Ba,Sr,Nb,Ta,Ti and P,with high Rb/Sr,Rb/ Ba,Nb/Ta,Y/Yb ratios and strongly negative europium anomalies.They also have lower Zr,Nb,Ce and Y concentrations relative to that of the typical A-type granites.Integrated geological and geochemical discrimination suggests that the Nanpingxueshan granite should be genetically ascribed to highly fractionated I-type granites.The medium-grained porphyritic biotite-quartz monzonite and medium to fine grained biotite-quartz monzonite have narrow zircon Hf isotopic compositions,with positive εHf(t) values ranging from 0.9 ～ 5.3 and 1.4 ～ 5.6,respectively.Correspondingly,they have Mesoproterozoic two-stage Hf model ages ranging from 1118 ～ 1398Ma and 1136 ～ 1396Ma,respectively.Similar geochemical features and zircon Hf isotopic compositions indicate that they were the products of the same magma evolution.Based on evolution history of the regional structure,we can speculate the Proto-Tethys may be bidirectional subduction during early Mesozoic.The Nanpingxueshan granite was formed through a certain extent of fractional crystallization and at least two partial melting of the Mesoproterozoic young crust,which was induced by uprising of mantle magma and invaded into lower crust during the continuous southward subduction-collision of Tethys ocean during Early Cambrian to Early Ordovician.关键词
早古生代花岗岩/地球化学/Hf同位素/原特提斯洋/南屏雪山/甜水海地块Key words
Early Paleozoic granite/geochemistry/Hf isotopic compositions/Proto-Tethys ocean/Nanpingxueshan/Tianshuihai terrane引用本文复制引用
胡军,王核,慕生禄,王敏,候学文..西昆仑甜水海地块南屏雪山早古生代花岗岩地球化学、Hf同位素特征及其壳幔岩浆作用[J].地质学报,2017,91(6):1192-1207,16.基金项目
本文为“十二五”国家科技支撑计划项目(编号:2011BAB06B05-01、2015BAB05B03)和国家自然科学基金青年基金项目(批准号:41602063)联合资助的成果. （编号:2011BAB06B05-01、2015BAB05B03）
