| 西准噶尔宝贝岩体的LA-ICP-MS锆石U-Pb年代学与地球化学 |
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| 引用本文： | 乔耿彪,赵寒森,陈隽璐,白建科,樊金生,彭素霞.西准噶尔宝贝岩体的LA-ICP-MS锆石U-Pb年代学与地球化学[J].地质科学,2018,0(2):566-585. |
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| 作者姓名： | 乔耿彪 赵寒森 陈隽璐 白建科 樊金生 彭素霞 |
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| 作者单位： | 中国地质调查局西安地质调查中心，国土资源部岩浆作用成矿与找矿重点实验室 西安 710054
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中国地质调查局造山带地质研究中心 西安 710054
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西安西北有色物化探总队有限公司 西安 710068 |
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| 摘 要： | 宝贝岩体位于新疆西准噶尔南部的晚古生代达尔布特中酸性岩浆岩带中，其主要岩性为花岗斑岩。通过LA-ICP-MS锆石U-Pb定年，结合锆石阴极发光图像（CL）和U、Th元素特征，获得宝贝岩体的年龄为297±10 Ma （MSWD = 14），时代属晚石炭世晚期。花岗斑岩为典型的斑状结构，斑晶以斜长石、条纹长石和石英为主；岩石中SiO2含量为74.59%～76.26%、全碱变化于8.13%～8.63%；铝饱和指数A/CNK为1.00～1.02，属弱过铝质；岩石轻稀土富集且轻重稀土元素分馏明显，（La/Yb）N为1.54～3.05，负Eu异常（δEu为0.25～0.53）；富集Rb、Th、U、K和LREE等大离子亲石元素，而贫Ba、Nb、Sr、P、Ti等元素，属高钾钙碱性Ⅰ型花岗岩系列。根据岩体的成因类型并结合区域构造环境演化，分析认为西准噶尔不仅在晚石炭世早期存在与俯冲作用相关的岛弧花岗岩，在晚石炭世晚期-早二叠纪早期也存在持续俯冲作用，在此环境下形成了与俯冲作用相关的岛弧型宝贝花岗斑岩。
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| 关 键 词： | 地球化学 晚石炭世晚期 Ⅰ型花岗岩 宝贝岩体 西准噶尔 |
| 收稿时间： | 2017-08-04 |
| 修稿时间： | 2017-08-04; |
Petrogenesis of the Baobei pluton in West Junggar: Constraints from LA-ICP-MS zircon U-Pb geochronology and geochemistry |
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| Qiao Gengbiao Zhao Hansen Chen JunluBai Jianke Fan Jinsheng Peng Suxia.Petrogenesis of the Baobei pluton in West Junggar: Constraints from LA-ICP-MS zircon U-Pb geochronology and geochemistry[J].Chinese Journal of Geology,2018,0(2):566-585. |
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| Authors: | Qiao Gengbiao Zhao Hansen Chen JunluBai Jianke Fan Jinsheng Peng Suxia |
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| Institution: | Xi'an Center, China Geological Survey, Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MLR, Xi'an 710054;Orogen Research Center of China Geological Survey, Xi'an 710054;Geophysical and Geochemical Exploration Corporation, Northwest Bureau of Geological Exploration for Nonferrous Metals, Xi'an 710068 |
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| Abstract: | The Baobei pluton is located in the intermediate acidic magmatic rocks belt of the West Junggar area of Xinjiang. The pluton is composed mainly of granite porphyry. Combined with the cathodolumine scence（CL）images and element U and Th features of zircon, this study yielded an age of 297±10 Ma（MSWD = 14）for the pluton using the LA-ICP-MS zircon U-Pb dating, indicating the Late Carboniferous. The plagioclase, perthite and quartz phenocrystals are dominant in granite porphyry with a typical porphyrotopic texture. The geochemical analysis show that the pluton is characterized by SiO2 = 74.59%～76.26%, total alkali（Na2O+K2O）= 8.13%～8.63%, and aluminum index A/CNK = 1.00～1.02, indicating a transitional composition between metaluminous and peraluminous. The pluton is enriched in LREE, depleted in HREE（LREE/HREE = 2.38～4.03,（La/Yb）N = 1.54～3.05 ）, with negative Eu anomaly（δEu = 0.25～0.53）. While the trace elements are characterized by Rb, Th, U, K, LREE enriched, and Ba, Nb, Sr, P, Ti depleted. All the features suggest a high K calcic-alkaline Ⅰ-type granite. Based on comprehensive analysis of the genetic type of the pluton and evolution of regional tectonic environment, we suggested that when the Junggar Ocean perpetually continued its deep subduction toward north during from the early Late Carboniferous to the Early Permian, and the Baobei granite porphyry was formed just during this tectonic evolution. |
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| Keywords: | Geochemical characteristics" target="_blank">')" href="#">Geochemical characteristics Late Carboniferous Ⅰ-type granite" target="_blank">Ⅰ-type granite')" href="#">Ⅰ-type granite Baobei pluton West Junggar" target="_blank">')" href="#">West Junggar |
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