| 西准噶尔克拉玛依岩体的成因:年代学、岩石学和地球化学证据 |
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| 引用本文： | 贺敬博,陈斌.西准噶尔克拉玛依岩体的成因:年代学、岩石学和地球化学证据[J].地学前缘,2011,18(2):191-211. |
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| 作者姓名： | 贺敬博 陈斌 |
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| 作者单位： | 贺敬博,He Jingbo(北京大学,地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京,100871);陈斌,Chen Bin(北京大学,地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京,100871;新疆大学,地质与勘察工程学院,新疆,乌鲁木齐,830046) |
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| 基金项目： | 新疆大学"天山学者"特聘教授启动资金项目，国家自然科学基金项目 |
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| 摘 要： | 西准噶尔地区克拉玛依岩体主要由闪长岩和花岗岩组成,锆石SHRIMP法给出的岩体结晶年龄为(315.5±2.8)Ma,为晚石炭世侵入岩.克拉玛依岩体具岛弧岩石的元素地球化学特征:总体上岩石富钠.A/CNK=0.57～0.84,富集LREE,(La/Yb)N=4.7～6.1,Eu显示弱负异常(δEu=0.76～0.91),...
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| 关 键 词： | 克拉玛依岩体 包体 岩浆混合 Nd-Sr同位素 西准噶尔 |
Petrogenesis of Karamay plutons in the west Junggar:Constraints from geochronology,petrology and geochemistry |
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| He Jingbo,Chen Bin.Petrogenesis of Karamay plutons in the west Junggar:Constraints from geochronology,petrology and geochemistry[J].Earth Science Frontiers,2011,18(2):191-211. |
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| Authors: | He Jingbo Chen Bin |
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| Institution: | 1,2 1.Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education;School of Earth and Space Sciences,Peking University,Beijing 100871,China 2.School of Geology and Exploration Engineering,Xinjiang University,rümqi 830046,China |
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| Abstract: | The Karamay plutons from the west Junggar are mainly made up of dioritic to granitic rocks.U-Pb dating of zircons from a quartz diorite suggests that the pluton was emplaced at 315.5±2.8 Ma(late Carboniferous),based on the SHRIMP method.The Karamay plutons show geochemical features reminiscent of arc magmas: Na-rich,A/CNK=0.57-0.84,enrichment of LREE((La/Yb)N=4.7-6.1) and LILEs with minor negative Eu anomalies(δEu=0.76-0.91),depletion of HFSEs such as Nb and Ta,and being typical of I-type granitoids.Linear trends of SiO2 versus other major elements were observed,suggesting that mixing between mantle-derived magma and crustal melts and/or fractional crystallization have played an important role in forming different rock types of the plutons.Microgranular mafic enclaves(MMEs) are common in the plutons.Compositional and textural disequilibrium of plagioclase and hornblende in the MMEs and host rocks was observed,suggesting a mechanical and chemical exchange between the two rock units and also a mixing origin for the MMEs.The host rocks and MMEs are similar in terms of Nd and Sr isotopic compositions,with ISr(t)=0.70352-0.70388,εNd(t)=6.9-7.4,typical of that of depleted mantle.Isotopic modeling suggests no signs of old continental crust beneath the west Junggar.The petrogenesis of the Karamay plutons can be summarized as below: post-collisional lithospheric extension caused the upwelling of asthenosphere and partial fusion of lithospheric mantle,producing voluminous basaltic magmas,which underplated in,and thus caused the partial melting of the juvenile lower crust(Paleozoic arc series and oceanic crust) and resulted in the formation of granitic magmas;subsequent mixing between the granitic and basaltic magmas gave birth to a hybrid magma,from which the Karamay plutons were formed through significant fractionation of calcic plagioclase and ferromagnesian phases such as pyroxene and hornblende. |
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| Keywords: | Karamay plutons mafic enclaves magma mixing Nd-Sr isotopes west Junggar |
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