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| 浙东南晚中生代玄武岩的地球化学特征及其对源区物质的指示意义 | |
| 引用本文： | 崔玉荣,谢智,王斌,陈江峰,俞云文,贺剑锋.浙东南晚中生代玄武岩的地球化学特征及其对源区物质的指示意义[J].高校地质学报,2011,17(4):492-512. |
| 作者姓名： | 崔玉荣 谢智 王斌 陈江峰 俞云文 贺剑锋 |
| 作者单位： | 1. 中国科学技术大学 地球和空间科学学院，中科院 壳幔物质与环境重点实验室，合肥 230026；; 2. 天津地质矿产研究所，天津 300170；3. 浙江省地调院，萧山 311200 |
| 基金项目： | 中科院知识创新项目，国家自然科学基金项目，新世纪优秀人才支持计划 |
| 摘 要： | 浙江东南部晚中生代上、下火山岩系(以下简称上、下岩系)中均有玄武岩产出,本文对这些玄武岩分别进行了元素地球化学和Sr-Nd-Pb同位素研究.不同岩系玄武岩的主量元素均表现出富碱、富Al等特征.但微量元素存在差异,下岩系天台和青田样品具有轻稀土富集以及Ba,Pb和Sr富集,Eu负异常,Nb,Ta,Zr和Hf亏损的特征.上... |
| 关 键 词： | 晚中生代 玄武岩 地球化学特征 源区物质 浙东南 |
| 修稿时间： | 2011-09-26 |
Geochemical Characteristics of the Late Mesozoic Basalts in Southeastern Zhejiang Province and Constraints on Magma Source Materials |
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| CUI Yu-rong,XIE Zhi,WANG Bin,CHEN Jiang-feng,YU Yun-wen,HE Jian-feng.Geochemical Characteristics of the Late Mesozoic Basalts in Southeastern Zhejiang Province and Constraints on Magma Source Materials[J].Geological Journal of China Universities,2011,17(4):492-512. | |
| Authors: | CUI Yu-rong XIE Zhi WANG Bin CHEN Jiang-feng YU Yun-wen HE Jian-feng |
| Institution: | 1. Chinese Academy of Sciences Key Laboratory of Crust Mantle Materials and Environments, School of Earth and Space Sciences,; University of Science and Technology of China, Hefei 230026, China; 2. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China; 3. Zhejiang Geological Survey, Xiaoshan 311200, China |
| Abstract: | The late Mesozoic basalts occur in the southeastern Zhejiang Province together with acidic volcanic rocks， which can be divided into upper and lower rock series (URS and LRS). Major, trace elements and Sr-Nd-Pb isotopic features of these basalts are studied in this paper to provide insights into the nature of their magma sources and evolution processes. Both the URS and LRS basalts are enriched in alkaline and Al elements. However, their characteristics of trace elements are different. The samples from Tiantai and Qingtian of LRS are enriched in LREEs, Ba, Pb and Sr, and depleted in Nb, Ta, Zr and Hf with Eu negative anomalies. The basalts from Yongjiahuatan, Ningboxuantandi, Xinchangjingling and Yongjiajingjiashan basalts of URS show similar trace elements and REEs natures to those of the samples from LRS, but basalts from Wuyi of URS show no negative Ta, Nb anomalies, while the trace element features of the basalts from Jinqu Basin are on the average. Correspondingly, isotopic compositions of these basalts are also variable apparently. The initial isotopic ratios of basalts from LRS range are as follows: ISr= 0.70850~ 0.70897, εNd(t )=-5.6~-4.1, (206Pb/204Pb)i =18.21~18.38, (207Pb/204Pb)i =15.55~15.58, (208Pb/204Pb)i =38.26~38.49,which are approximate to those of the intermediate-acid magmatic rocks in LRS, indicating that their magmatic sources were contaminated significantly by the lower crustal materials. Basalts from URS demonstrate a marked difference from those of the LRS in isotopic features by showing similar groups as the characteristics of trace elements. The samples from Yongjiahuatan,Ningboxuantandi, Xinchangjingling and Yongjiajingjiashan of URS have enriched Sr-Nd isotopic compositions with I Sr=0.70734~0.70936, εNd(t )=-7.1~-2.1, (206Pb/204Pb)i =18.01~18.40, (207Pb/204Pb)i =15.54~15.62, (208Pb/204Pb)i = 37.99~38.62,suggesting that these basalts are most likely generated from active continental margin. The samples from Wuyi and Jinqu Basins have the characteristics similar to OIB with I Sr = 0.70533~0.70589, εNd(t ) = 0.4~3.3, (206Pb/204Pb)i = 17.23~18.11, (207Pb/204Pb)i=15.46~15.53, (208Pb/204Pb)i = 36.91~38.43, towards the end member of depleted mantle. Based on elements and isotopic compositions of the Late Mesozoic basalts from the southeastern Zhejiang Province, the sources of the basalt are significantlydifferent and varied obviously with time. It could be concluded that the initial magma of basalts of LRS may be derived fromthe ancient lithospheric mantle, subducted altered oceanic crust and contaminated by lower crustal materials. The source of the basalts of URS may contain the materials of the lithospheric mantle which is similar to basalts from LRS, depleted OIB-like mantle and lower crust materials. It is also concluded the formation of the late Mesozoic basalts in the southeastern Zhejiang Province may be related to the Pacific plate subduction, but the influence of delamination of the lithospheric mantle could not be ruled out.Since that, much further information of petrology and/or mantle xenoliths is needed for the specific discussion about the dynamic process. |
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