新疆巴尔鲁克地区石屋岩体的成因:锆石U-Pb年代学、岩石地球化学和Sr-Nd-Pb-Hf同位素制约  

Origin of the Shiwu pluton in Barluk region,Xinjiang: Zircon U-Pb chronological,geochemical and Sr-Nd-Pb-Hf isotopic constraints

作　　者：胡洋[1] 王居里[1] 王建其[1] 令伟伟[1] HU Yang, WANG JuLi ,WANG JianQi , LING WeiWei(State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi＇ an 710069, Chin)

机构地区：[1]大陆动力学国家重点实验室西北大学地质学系,西安710069

出　　处：《岩石学报》2018年第3期601-617,共17页Acta Petrologica Sinica

基　　金："十二五"国家科技支撑计划项目(2011BAB06B01-03);国家自然科学基金项目(41572057)联合资助

摘　　要：新疆巴尔鲁克地区石屋岩体主要由石英闪长玢岩、石英闪长岩组成。本文通过锆石U-Pb年代学、岩石地球化学和Sr-Nd-Pb-Hf同位素等研究,探讨其构造背景、岩石成因和成矿意义。LA-ICP-MS锆石U-Pb定年表明:石屋石英闪长玢岩的成岩年龄为322.1±1.5Ma,石英闪长岩的形成年龄为322.4±1.5Ma,二者形成时代为晚石炭世。石屋石英闪长玢岩和石英闪长岩地球化学特征相似,Mg~#为32.4~57.2,轻重稀土分馏较明显且富集轻稀土((La/Yb)N=2.36~6.04),Eu异常不明显,相对富集LILEs等,亏损Nb、Ta、P、Ti等高场强元素。Sr-Nd-Pb-Hf同位素显示:样品具有低的ISr值(0.7036~0.7045),正εNd(t)值(+4.61^+7.03),年轻的tDM1年龄(0.59~0.78Ga),初始铅同位素比值为(^(206)Pb/^(204)Pb)i=18.173~18.450,(^(207)Pb/^(204)Pb)i=15.542~15.562,(^(208)Pb/^(204)Pb)i=37.830~38.036,锆石εHf(t)值为+4.5^+15.3,t_(DM2)=0.36~0.62Ga。综合石屋岩体的地质、地球化学和年代学特征,认为石英闪长玢岩和石英闪长岩源区相同,它们均形成于晚石炭世早期俯冲背景下的岛弧环境,可能是在亏损玄武质岩浆(俯冲板片脱水交代地幔楔产生的上涌岩浆)底侵作用下,新生地壳发生部分熔融,并有部分玄武质岩浆加入,发生混合、侵位的产物。石屋岩体的形成环境及其岩浆演化过程可能有利于区内斑岩型铜矿化,其含矿性值得做进一步评价。The Shiwu pluton in Barluk region, Xinjiang, is mainly composed of quartz diorite porphyry and quartz diorite. By combined studies of zircon U-Pb chronology, Hf isotope, whole rock geochemistry and Sr-Nd-Pb isotopes on this pluton, its petrogenesis, tectonic setting and metallogenic significance are discussed. LA-ICP-MS zircon U-Pb dating on the quartz diorite porphyry and quartz diorite yields their crystallization ages of 322.1±1.5Ma and 322.4±1.5Ma, respectively, indicating the pluton was formed in Late Carboniferous. The quartz diorite porphyry and quartz diorite of the Shiwu pluton have similar geochemical characteristics. They have Mg^# ranging from 32.4 to 57.2. The REEs are obviously fractionated with （La/Yb）N=2.36-6.04 and weakly Eu anomaly. They are also enriched in LILE and depleted in Nb, Ta, P and Ti. Sr-Nd-Pb isotopic compositions indicate that Shiwu granite body is characterized by positive εNd（t）（＋4.61-＋7.03）, low ISr（0.7036-0.7045）and relatively young model ages （tDM） ranging from 0.59Ga to 0.78Ga, （^206Pb/^204Pb）i=18.173-18.450, （^207Pb/^204Pb）i=15.542-15.562 and （^208Pb/^204Pb）i=37.830-38.036. The εHf（t） values and tDM2 model ages of zircon are ＋4.5-＋15.3 and 0.36-0.62Ga, respectively. Comprehensive geological, geochemical and chronological studies demonstrate that the Shiwu intrusive rocks may be formed in an island background during early subduction stage in Late Carboniferous, and are derived from partial melting of the juvenile crust, which may be generated by underplating of depleted basaltic magma （the upwelling of magma formed by the fluid metasomatic mantle wedge）. The tectonic setting and evolution of Shiwu pluton are very important for copper mineralization, and therefore it is worth for further evaluation.

关 键 词：晚石炭世 岛弧 岩石成因 石屋 巴尔鲁克地区 新疆 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]