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江西相山火山—侵入杂岩及其包体希土元素地球化学

段芸, 赵连泽, 范洪海, 王德滋   

  1. [1]南京大学地球科学系及内生金属矿床成矿机制研究国家重点实验室,江苏南京210093
  • 收稿日期:2001-03-20 修回日期:2001-03-20 出版日期:2001-03-20 发布日期:2001-03-20

REE-Geochemistry of Mesozoic Volcanic-Intrusive Complex and Dark Inclusions in Xiangshan District,Jiangxi Province

DUAN Yun, ZHAO Lian-ze, FAN Hong-hai, WANG De-zi   

  1. Department of Earth Sciences and State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China
  • Received:2001-03-20 Revised:2001-03-20 Online:2001-03-20 Published:2001-03-20

摘要: 本文综合性地报道了江西相山中生代中、酸性火山-侵入杂岩的稀土元素地球化学研究,以探讨基底变质岩、火山岩、次火山岩及闪长质包体之间的成因联系和差异性。认为此套火山-侵入杂岩具同源演化关系,推测它们均来源于前震旦系结晶基底,成因上属于陆壳重熔型。这与前人对此研究的主流观点是一致的,同时更具有完整性和系统性。

Abstract: The dark-coloured enclaves were found in subvocanic dike for the first time in the Xiangshan district,Jiangxi Province,which provides a new information for studying Mesozoic vocanic-intrusive complex in this region. This kind of enclaves exsit in smal1 amounts,with chilled margin,back veins,and other obvious quenching characteristics. Petrologically they aye mainly dioritoids. We colleted 14 samples ,including the basemental rocks,volcanic rocks,subvolcanic rocks and dark enclaves,and made detailed REE analyses on them. Combining with the previous study, we tried to explain the genetic relations hip and difference between them in a more integrated and systematic way. The data and diagrams demonstrate that: 1)as a whole,the magmas which formed various volcanic rocks with slight to intermediate fractionation degree of REE and strong europium negative anomalies ,were differentiated an d evolved in the same magmatic reservoir, The latter was originated from the continental crust; 2)products of the bicyclic volcanic activity. Rhyodacite and porphymclast lava,represent double emptying of magma reservoir; 3)REE data of dioritic enclaves don’t show strong europium negative anomalies . Conseguently we concluded that the magma of these enclaves was derived from a deeper level,and could be a mixture of lower crust and enriched mantle with a higher mixing proportion. Furthermore,Pb,Si,Nd isotope data also provided similar information. εNd(t) of volcanics and subvolcan cs are –8.8 and –11.2,respectively,which are very close to the upper crust va1ue in southeast China,while that for the dioritic enclaves is –6.5,which indicates involvement of a deeper source component. Mesozoic volcanic-intrusive complex in Xianshan district was generated by the partial melting of sialic lithosphere and belongs to the S-type in origin,which is consistent with the popular point of view. However,discovery of dioritic enclaves implies possible participation of lower crust or even upper mantle component