| 东昆仑希望沟橄榄辉石岩LA-ICP-MS锆石U-Pb定年及岩石地球化学特征 |
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| 引用本文： | 孔会磊,栗亚芝,李金超,贾群子,国显正,张斌.东昆仑希望沟橄榄辉石岩LA-ICP-MS锆石U-Pb定年及岩石地球化学特征[J].地质力学学报,2019,25(3):440-452. |
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| 作者姓名： | 孔会磊 栗亚芝 李金超 贾群子 国显正 张斌 |
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| 作者单位： | 中国地质调查局西安地质调查中心, 陕西 西安710054;自然资源部岩浆作用成矿与找矿重点实验室, 陕西 西安710054;中国地质大学(武汉)地质调查研究院,湖北 武汉,430074;宝鸡西北有色七一七总队有限公司,陕西 宝鸡,721012 |
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| 基金项目： | 中国地质调查局地质调查项目（DD20160013，12120115022101，12120113029000） |
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| 摘 要： | 东昆仑古特提斯域镁铁-超镁铁质岩石的研究极为薄弱，对青海东昆仑东段希望沟镁铁-超镁铁质杂岩体中橄榄辉石岩进行岩相学、地球化学及年代学分析，以期为东昆仑晚古生代-早中生代构造岩浆演化提供新的约束。利用LA-ICP-MS锆石U-Pb定年，获得希望沟橄榄辉石岩加权平均年龄为（262.4±1.6）Ma，表明岩体侵位于中二叠世。岩石地球化学研究显示，希望沟橄榄辉石岩具有较高的Mg#值（85.31~86.27），m/f比值介于5.50~6.18，属于铁质超基性岩类；具有低TiO2（0.41%~0.52%）和低Al2O3（3.04%~4.57%），属钙碱性系列。岩石富集大离子亲石元素（Rb、Th、U）和Pb，相对亏损高场强元素（Nb、Ta、P、Ti），ΣREE为29.79×10-6~38.96×10-6，（La/Yb）N为1.71~2.51，平均2.15，δEu=0.73~0.86，具有弱的Eu负异常。岩石成因分析表明，岩石源区为被俯冲改造的岩石圈地幔，岩浆在演化过程中遭受了上地壳物质的同化混染作用。结合东昆仑区域构造演化，认为希望沟橄榄辉石岩为阿尼玛卿古特提斯洋俯冲阶段的岩浆记录。
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| 关 键 词： | 地球化学 锆石U-Pb定年 希望沟橄榄辉石岩 东昆仑 |
| 收稿时间： | 2018/5/9 0:00:00 |
| 修稿时间： | 2018/8/27 0:00:00 |
LA-ICP-MS ZIRCON U-PB DATING AND GEOCHEMICAL CHARACTERISTICS OF THE XIWANGGOU OLIVINE PYROXENOLITE IN EAST KUNLUN |
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| KONG Huilei,LI Yazhi,LI Jinchao,JIA Qunzi,GUO Xianzheng and ZHANG Bin.LA-ICP-MS ZIRCON U-PB DATING AND GEOCHEMICAL CHARACTERISTICS OF THE XIWANGGOU OLIVINE PYROXENOLITE IN EAST KUNLUN[J].Journal of Geomechanics,2019,25(3):440-452. |
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| Authors: | KONG Huilei LI Yazhi LI Jinchao JIA Qunzi GUO Xianzheng and ZHANG Bin |
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| Institution: | 1.Xi'an Center of Geological Survey, CGS, Xi'an 710054, Shannxi, China2.Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MNR, Xi'an 710054, Shannxi, China3.Institute of Geological Survey, China University of Geosciences, Wuhan 430074, Hubei, China4.Baoji 717 Corps Limited of the NWME, Baoji 721012, Shannxi, China |
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| Abstract: | The mafic-ultramafic rocks in Paleo-Tethys domain of East Kunlun are not well documented. Researches on petrography, geochronology and geochemistry of the olivine pyroxenolite in Xiwanggou mafic-ultramafic intrusion, located in the Eastern Section of East Kunlun in Qinghai Province, can provide new constraints for the Late Paleozoic-Early Mesozoic tectono-magmatic evolution in East Kunlun. LA-ICP-MS zircon U-Pb dating indicates that the weighted mean age of Xiwanggou olivine pyroxenolite is (262.4±1.6) Ma, in the Middle Permian. Lithogeochemical studies show that the olivine pyroxenolite, which is calc-alkaline series, is characterized by high content of Mg#(85.31~86.27), low content of TiO2(0.41%~0.52%) and low Al2O3(3.04%~4.57%). The m/f ratios range from 5.50 to 6.18, indicative of iron series of ultrabasic rocks. This suite of rocks are enriched in LILE (such as Rb, Th, U) and Pb, relatively depleting in HFSE (such as Nb, Ta, P, Ti). The rocks have low REE contents, with slightly negative Eu anomaly(∑REE=29.79×10-6~38.96×10-6, (La/Yb)N=1.71~2.51, δEu=0.73~0.86). The geochemical characteristics show that the parental magma of olivine pyroxenolite derived probably from the mantle influenced by the subducton. The parental magma is developed by the upper crustal assimilation contamination during the magma evolution. Combined with regional evolutionary characteristics in East Kunlun, the authors consider that the Xiwanggou olivine pyroxenolite ought to be the magmatism records in the subduction of Anyemaqen-Paleo-Tethys ocean. |
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| Keywords: | geochemistry zircon U-Pb dating Xiwanggou olivine pyroxenolite East Kunlun |
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