| 锆石U-Pb年代学和地球化学对浙皖马鞍山高分异岩体成因的约束 |
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| 引用本文： | 张建芳,汪隆武,陈津华,朱朝晖,刘健,章明圆.锆石U-Pb年代学和地球化学对浙皖马鞍山高分异岩体成因的约束[J].地球科学,2015,40(1):98-114. |
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| 作者姓名： | 张建芳 汪隆武 陈津华 朱朝晖 刘健 章明圆 |
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| 作者单位： | 浙江省地质调查院, 浙江杭州 311203 |
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| 基金项目： | 中国地质调查局地质大调查项目 |
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| 摘 要： | 为了解由早期(伟晶、巨晶)斑状二长花岗岩、中期(细粒)花岗岩和晚期花岗(斑)岩脉组成的马鞍山杂岩体的成因, 采用SHRIMP和LA-ICP-MS锆石U-Pb法厘定其侵入时代, 年龄显示伟晶斑状二长花岗岩为132.2±1.6 Ma, 巨晶斑状二长花岗岩为127. 7±1.2 Ma, 细粒花岗岩为128.3±1.1 Ma, 花岗斑岩脉为127.4±1.8 Ma.岩石地球化学研究结果表明岩体从早到晚具有从钾玄岩系列向高钾钙碱系列演变特征, 分异演化程度逐渐变高; 斑状二长花岗岩具有高REE含量, 轻重稀土分异较为明显, 具较强负铕异常和弱右倾的配分曲线特征, 富集K、Th、U、Rb等元素, 弱亏损Ba、Sr、P、Nb、Ta、Ti等元素; 细粒花岗岩及花岗(斑)岩脉具有较低REE含量, 轻重稀土分异不明显, 具强负铕异常和"V"型配分曲线特征, 富集K、Th、U、Rb等元素, 强亏损Ba、Sr、P、Nb、Ti等元素.马鞍山岩体为浙西北-皖南地区早白垩世俯冲造山后陆内拉张作用环境下下地壳部分熔融的同源岩浆侵位结晶分异作用形成的产物, 具有高分异I型花岗岩的特征.
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| 关 键 词： | 锆石U-Pb 地球化学 岩石成因 马鞍山岩体 浙皖相邻区 |
| 收稿时间： | 2014-05-01 |
Genesis of Highly Fractionated Ma’anshan Rock in Zhejiang and Anhui Provinces Constrained by U-Pb Zircon Geochronology and Geochemistry |
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| Zhang Jianfang,Wang Longwu,Chen Jinhua,Zhu Chaohui,Liu Jian,Zhang Mingyuan.Genesis of Highly Fractionated Ma’anshan Rock in Zhejiang and Anhui Provinces Constrained by U-Pb Zircon Geochronology and Geochemistry[J].Earth Science-Journal of China University of Geosciences,2015,40(1):98-114. |
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| Authors: | Zhang Jianfang Wang Longwu Chen Jinhua Zhu Chaohui Liu Jian Zhang Mingyuan |
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| Affiliation: | Zhang Jianfang;Wang Longwu;Chen Jinhua;Zhu Chaohui;Liu Jian;Zhang Mingyuan;Zhejiang Institute of Geological Survey; |
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| Abstract: | To understand the genesis of Ma'anshan rock composed of early period pegmatite and megacryst porphyritic adamellite, medium period fine granite and late period granite porphyry dykes, intrusion epochs are confirmed using SHRIMP and LA-ICP-MS zircon U-Pb methods. The dating shows that the pegmatite porphyritic adamellite is 132.2±1.6 Ma (MSWD=1.9, n=11), the megacrysts porphyritic adamellite 127.7 ±1.2 Ma (MSWD=1.1, n=10), the fine-grained granite 128.3±1.1 Ma (MSWD=1.7, n=10) and the granite porphyry dykes 127.4±1.8 Ma (MSWD=0.77, n=11). Rock geochemistry shows that the rock from early to late has the characteristic of alkali series shoshonite series evolving to high potassium calc (during evolution), whereas the differentiation degree gradually increases. The porphyritic adamellites have the characteristics of high ΣREE content, obvious differentiation between light rare earth and heavy rare earth elements, with a strong negative Eu anomaly and weak rightward REE distribution patterns. It is enriched in elements of K, Th, U, Rb and weakly depleted in Ba, Sr, P, Nb, Ta, Ti. The fine-grained granite and granite porphyry dyke have the characteristics of lower ΣREE content, not obvious differentiation between light and heavy rare earth elements, with a strong negative Eu anomaly, and "V"-type REE distribution patterns. It is enriched in elements of K, Th, U, Rb, strongly depleted in Ba, Sr, P, Nb, Ti. Ma'anshan rock was formed by the function of partially molten magma emplacement successively crystallization differentiation and it is the product of intracontinental extension after the Early Cretaceous subduction orogeny in Northwest Zhejiang-South Anhui, with the characteristic of highly fractionated I-type granites. |
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| Keywords: | zircon U-Pb geochemistry petrogenesis Ma'anshan rock Zhejiang and Anhui border area |
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