西天山喇嘛苏岩体年代学、地球化学及成矿意义  

Geochronology,geochemistry and metallogenic implications of the Lamasu intrusion in western Tianshan,NW China

作　　者：解洪晶[1,2] 武广[3,4] 朱明田[5] 晋建平 钟伟[1] 刘军[3] 糜梅[1] 

机构地区：[1]中国科学院广州地球化学研究所矿物与成矿重点实验室,广东广州510640 [2]中国科学院研究生院,北京100049 [3]中国地质科学院矿产资源研究所,北京100037 [4]河南省灵宝市金源矿业有限责任公司,河南灵宝472500 [5]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029

出　　处：《地学前缘》2013年第1期190-205,共16页Earth Science Frontiers

基　　金："十一五"国家科技支撑计划项目(2007BAB25B03);国家重点基础研究发展计划"973"项目(2007CB411308);国家自然科学基金项目(41172081;40772055)

摘　　要：文中主要对西天山喇嘛苏岩体进行SHRIMP锆石U-Pb年龄、主微量及Sr-Nd-Pb同位素测定,阐明岩体成因及形成构造背景。喇嘛苏岩体主要由石英二长闪长岩、花岗闪长斑岩和英云闪长斑岩组成。其中,石英二长闪长岩形成于(394.8±4.9)Ma,花岗闪长斑岩和英云闪长斑岩形成于(380.9±3.9)Ma,略晚于石英二长闪长岩。岩体具有埃达克质岩的特征,且显示从钙碱性向高钾钙碱性演化的趋势,稀土元素配分曲线显示相对富集轻稀土((La/Yb)N:3.55～15.52)及中等的负或正Eu异常(δEu:0.53～1.12)。岩体具有较高的Sr含量((322～808)×10-6)和较低的Y含量((12.90～18.86)×10-6)。微量元素特征显示岩体富集LILE亏损HFSE,并具有Nb、Ta和Ti负异常。岩体初始Sr-Nd同位素组成为εNd(t)=-4.29～+0.75和ISr=0.706 052～0.708 263,Nd模式年龄为1.03～1.46Ga。花岗闪长斑岩和英云闪长斑岩的铅同位素特征为206Pb/204Pb=18.500～19.044,207Pb/204Pb=15.575～15.626,208Pb/204Pb=38.443～38.864;石英二长闪长岩为206Pb/204Pb=18.694～18.711,207Pb/204Pb=15.622～15.630,208Pb/204Pb=38.648～38.660。所有地球化学特征显示喇嘛苏岩体是俯冲洋壳部分熔融形成的熔体,上升过程中与受俯冲带沉积物交代的地幔楔相互作用,且有少量古老地壳的混染而形成。岩体形成于晚泥盆世准噶尔残余洋盆向伊犁—中天山地块俯冲的大陆弧背景,与该区Cu(Au)矿化有较密切的联系。The zircon U-Pb geochronology,major and trace elements and S^Nd isotopes determination of the Lamasu intrusion in western Chinese Tianshan were conducted to understand its petrogenesis and geodynamic setting. The Lamasu intrusion is mainly composed of quartz monzodiorite,granodiorite porphyry and tonalite porphyry. Among them the quartz monzodiorite was formed in 394. 8 ± 4. 9 Ma, while the granodiorite porphyry and tonalite porphyry were intruded in 380. 9±＋3. 9 Ma. The rocks display the adakitic affinity and show a calc-alkaline and high-K calc-alkaline differentiation trend. They display REE patterns characterized by relative enrichment of LREE （（La/Yb）N ： 3.55 - 15.52） with slightly negative or positive Eu anomalies （δEu： 0. 53 - 1.12）. They have high Sr （（322 - 808） × 10 6 ） and low Y contents （（12.90 - 18.86） X 10 6 ） and also enriched in LILE but depleted in HFSE with negative Nb, Ta and Ti anomalies. Initial Sr-Nd isotopic compositions are eNa（t）=--4. 29 to 0. 75 and Isr=0. 706052 to 0. 708263. The Nd model ages vary from 1.03 to 1.46 Ga. The Pb isotopic ratios of granodiorite porphyry and tonalite porphyry are 206 pb/20,1Pb--18. 500 - 19. 044,207Pb/204 Pb= 15. 575 - 15. 626,208 Pb/204 Pb= 38. 443 - 38. 864, while the quartz monzodiorite are 206Pb/204Pb= 18. 694- 18. 711,207 Pb/204 Pb= 15. 622 - 15. 630,208Pb/204 Pb= 38. 648- 38. 660. All these geochemical data demonstrate that the Lamasu intrusion is likely derived from the partial melting of oceanic crust,with the subsequent melts interacted during their uplift with the overlying mantle wedge metasomatized by the subducted sediments and subordinately contaminated by ancient crust. The Lamasu intrusion was emplaced in a continental arc setting during the southward subduction of the Junggar Remnant Ocean Basin in the Late Devonian and are closely related with Cu （Au） mineralization of that region.

关 键 词：喇嘛苏岩体 锆石SHRIMPU-PB定年 元素地球化学 同位素地球化学 西天山 

分 类 号：P618.51[天文地球—矿床学]