Zircon U-Pb Age and Geological Implications of Ultramafic Rocks in Changshagou, Altun Area, Xinjiang Province
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摘要: 通过1:50000地质填图,表明新疆长沙沟(蛇绿)构造混杂岩带超镁铁质岩主要岩石类型为斜长辉石角闪岩、辉石橄榄岩、强蛇纹石化辉石橄榄岩等;总体贫SiO2、CaO、K2O、Na2O,富含MgO、
特征,分异指数DI=0.35～14.45,固结指数SI=47.82～70.05,表明岩浆分异不明显,固结程度较高;里特曼指数σ=0.97,属钙性系列;M/F=1.94～4.39,属镁铁质超基性岩类;其中,辉石橄榄岩TiO2含量接近洋中脊地幔(TiO2=0.10%~0.40%),稀土元素、微量元素特征与地幔橄榄岩近似,认为属原始地幔分离产物,为蛇绿岩套组成部分;斜长辉石角闪岩可能为超镁铁质杂岩.首次获得了辉石橄榄岩206Pb/238U加权平均年龄为(510.60±1.40)Ma(MSWD=0.11),形成时代为寒武纪,其可能代表了南阿尔金洋盆早期的产物. Abstract: During 1:50000 scale regional survey, the author discovered that the ultramafic rocks from Altun ophiolite tectonic mixtite belt are mainly composed of plagioclase pyroxene amphibolite, pyroxene peridotite, and serpentinized peridotite. Geochemistry of the diabase shows that the geochemistry of the major is characterized by low contents of SiO2, CaO, K2O, Na2O and high contents of MgO and FeO. With a low DI value (0.35-14.45), the magmatic differentiation is not obvious; while the solidification degree, with a high SI value (47.82-70.05), is relatively high. The ultramafic rocks belong to calcium series and magnesian ultrabasic rock, with the Rittman index of 0.97 and the M/F index from 1.94 to 4.39. Among the compositions, the TiO2 content in pyroxene peridotite is close to that of mid-ocean ridge mantle(0.10%-0.40%). Characteristics of rare earth element and trace element are similar to those of mantle peridotite. All these characteristics indicate that the ultramafic rock is a part of ophiolite suite derived from the primitive mantle. The plagioclase pyroxene amphibolite may be ultramafic diamictite. Meanwhile, the authors firstly got the U-Pb age (510.60±1.40 Ma) of zircon from pyroxene peridotite and hold that its age is considered to be the Cambrian and it may represent early products of South Altun oceanic basin.-
Keywords:
- ultramafic rocks /
- Zircon U-Pb dating /
- geological implications
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郭金城, 徐旭明, 吴永祥, 等. 新疆阿尔金地区1:5万J45E012015、J45E012016、J45E012017、J45E013015、J45E013016、J45E013017六幅区域地质矿调查报告 [R]. 河北省区域地质矿产调查研究所, 2013. Guo Jincheng, Xu Xuming, Wu Yongxiang, et al. Geological survey report and geological map at scale 1:250000 of Suwushijie Quadrangle [R]. Published by Hebei Institute of Regional Geological and Mineral Resource Survey, 2013.
西安地质矿产研究所. 昆仑—阿尔金成矿带基础地质综合研究报告 [R]. 2012. Xian Geological Survey, Geological survey report and geological map at scale 1:250000 of Suwushijie Quadrangle [R]. Published by Xian Geological Survey, 2012.
许立权, 邓晋福. 内蒙古达茂旗哈尔陶勒盖地区蛇绿岩形成环境探讨 [J]. 中国地质, 2006, 33(5): 1038-1043. Xu Liquan, Deng Jinfu. Tectonic environment of ophiolites in the Har Tolgoi area, Damao Qi, Inner Mongolia [J]. Geology in China, 2006, 33(5): 1038-1043.
广西壮族自治区地质调查院. 1:25万瓦石峡幅、古尔嘎幅区域地质调查报告 [R]. 2002. Guangxi Geological Survey, Geological survey report and geological map at scale 1:250000 of Washixia Quadrangle [R]. Published by Guangxi Geological Survey, 2002
冯益民. 蛇绿岩概念及其构造含义的变化 [J]. 西北地质, 1986, 19(03): 12-15. Feng Yimin. Ophiolite concept and the change of construct meaning [J]. Northwestern Geology, 1986, 19(03): 12-15.
马中平, 孙吉明, 唐卓, 等. 阿尔金山南缘长沙沟—清水泉一带镁铁-超镁质杂岩体Cu-Ni-PGE含矿性讨论 [J]. 西北地质, 2010, 43(4): 18-24. Ma Zhongping, Sun Jiming, Tang Zhuo, et al. Discussions on the Magmatic Cu-Ni-PGE Sulfides Mineralization Potential of the Changshagou-Qingshuiquan Layered Ma-fic-Ultramafic Intrusions, Altyn Tagh [J]. Northwes-tern Geology. 2010, 43(4): 18-24.
刘良, 车自成, 王焰, 等. 阿尔金茫崖地区早古生代蛇绿岩的Sm-Nd等时线年龄证据 [J]. 科学通报, 1998, 33(8): 880-883. Liu Liang, Che Zicheng, Wang yan, et al. Early Palaeozoic ophiolite evidence from Rb-Sr isochron ages of macrocrystalline calcite in Mangya, Altyn Tagh [J]. Chinese Science Bulletin, 1998, 33(8): 880-883.
马中平, 李向民, 孙吉明, 等. 阿尔金山南缘长沙沟镁铁-超镁铁质层状杂岩体的发现与地质意义——岩石学和地球化学初步研究 [J]. 岩石学报, 2009, 25(4): 793-804. Ma Zhongping, Li Xiangmin, Sun Jiming, et al. Discowery of layered mafic-ultramafic intrusion in Changshagou, Altyn Tagh, and its geological implication: A pilot study on its petrological and geochemical characteristics [J]. Acta Petrologica Sinica, 2009, 25(4): 793-804.
张旗, 李达周, 张魁武, 等. 义敦型镁铁-超镁铁岩的主要特征及其与蛇绿岩的对比 [J]. 岩石学报, 1990, 6(03): 33-42. Zhang Qi, Li Dazhou, Zhang Kuiwu, et al. The Characteristics of Yidun-type mafic-ultra-mafic rocks and their comparison with ophiolites [J]. Acta Petrologica Sinica, 1990, 6(03): 33-42.
马中平, 李向民, 徐学义, 等. 南阿尔金山清水泉镁铁-超镁铁质侵入体LA-ICP-MS锆石U-Pb同位素定年及其意义 [J]. 中国地质, 2011, 38(4): 1071-1078. Ma Zhongping, Li Xiangmin, Xu Xueyi, et al. Zircon LA-ICP-MS U-Pb isotopic dating for Qingshuiquan layered mafic-ulmafic intrusion southern Altun orogen, in northwestern China and its implication [J]. Geology in China, 2011, 38(4): 1071-1078.
简平, 刘敦一, 孙晓猛. 滇川西部金沙江石炭纪蛇绿岩SHRIMP测年: 古特地斯洋盆演化的同位素年代学制约 [J]. 地质学报, 2003, 77(2): 217-228. Jian Ping, Liu Dunyi, Sun Xiaomeng. SHRIMP Dating of Carboniferous Jinshajiang Ophiolite in western Yunnan and Sichuan: Geochronological constraints on the Evolution of the Paleo-Tethys Oceanic Crust [J]. Acta Geologica sinica, 2003, 77(2): 217-228.
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