新疆西准噶尔地区晚石炭世洋内俯冲与成矿:来自苏云河钼矿区Ⅰ~#含矿花岗岩体的证据  

Late Carboniferous intra-oceanic subduction and mineralization in western Junggar: Evidence from the petrology,geochemistry and zircon U-Pb geochronology of Ⅰ~# ore-bearing granite body in Suyunhe molybdenite orefield,Xinjiang

作　　者：杨猛[1,2] 王居里[1] 王建其[1] 刘存 

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 [2]西北有色地质勘查局,西安710054 [3]西北有色地质勘查局715总队,临潼710600

出　　处：《岩石学报》2015年第2期523-533,共11页Acta Petrologica Sinica

基　　金：“十二五”国家科技支撑计划项目(2011BAB06B01-03)资助

摘　　要：新疆西准噶尔苏云河地区发育有斑岩型（铜-）钨钼共生矿床，通过对矿区内I^#含矿岩体进行详细的岩石学、地球化学及锆石U-Ph年代学研究，探讨岩浆起源、构造背景及其成矿意义。结果表明：（1）岩体高SiO2、A12O3，中等富碱且相对富钠，A／CNK=1．08-1．28，б=1．52-1.81，属钙碱性（强）过铝质花岗岩；稀土含量较低（∑REE=33．77×10^-6～92．91×10^-6），轻重稀土分馏程度中等且富集轻稀土（（La／Vb）N=5．13-9．69），具弱Eu负异常（бEu=0．62-0．92）；相对富集Rb、Th、u、K等LILE和LREE，亏损Ba、Sr、P、Ti、Nb、Ta和HREE等；（2）锆石LA-ICP-MSU．Pb定年获得岩浆结晶年龄为308．8±4．1Ma，岩体侵位时代为晚石炭世；（3）岩体具有正的8Nd值（PNd=3．64～6．33）、低的87Sr／86Sr初始比值（Isr=0．704009～0．705313）和较年轻的二阶段模式年龄（t2DM=0．52-0．70Ga），形成于晚石炭世洋内俯冲背景下、有俯冲流体及少量洋盆陆源碎屑沉积物参与的晚元古代玄武质洋壳的部分熔融；（4）苏云河地区晚石炭世浅成岩浆侵入活动同时是一期重要的斑岩型（铜-）钨钼成矿事件，I^#岩体深部及巴尔鲁克断裂以西石嶷纪中酸性岩体的含矿性值得做进一步评价。Porphyry-type molybdenite mineralization of Suyunhe in western Junggar is closely related to Late Carboniferous granitic magrnatism. Rock samples of I^# ore-beating granite body consisting of monzonitic granite-porphyry, porphyritic monzonitie-granite and biotite monzonitie granite porphyry are geochemically characterized by high SiO2, A1203 with Na20/K20 ratios changing from 0. 97 to 1.32 and A/CNK ratios ranging from 1.08 to 1.28, which synthetically display characteristics of calcalkaline peraluminous granitoids. Granite samples are rich in LREE and LILE （ K, Rb, Th, U etc. ）, infertile in HREE and Ba, St, P, Ti, Nb, Ta etc. , coupling with weakly Eu negative anomaly （бEu = 0. 62 -0. 92 ）. Ore-beating granite body intruded at 308.8 ＋ 4. 1 Ma. Sr-Nd isotopic compositions indicate that I^# ore-bearing granite body is characterized by positive end （t） （ 3. 64 - 6. 33 ）, low /st （ 0. 704009 - 0. 705313 ） and relatively younger two-stage model ages （ t2DM ） ranging from 0. 52Ga to 0. 70Ga. In terms of both previous research results on regional tectonic setting and discrimination diagrams, I^# ore-bearing granite body in Suyunhe derived from partial melting of Late Proterozoic marie rocks with the mixture of fluid and elastic sediments. Granitic intrusion formed at intra-oceanic arc setting of Hercynian accretionary orogeny, which may also cause reasonable porphyry-type polymetallic mineralization related to Late Carboniferous magmatism in the west of Barleik Fault.

关 键 词：晚石炭世 源区性质 洋内弧 斑岩型矿床 西准噶尔苏云河 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]