南澜沧江带南段原特提斯岛弧火山岩新证据  

NEW EVIDENCE FOR THE ORIGINAL TETHYSAN ISLAND-ARC VOLCANIC ROCKS IN THE SOUTHERN SEGMENT OF SOUTH LANCANGJIANG BELT

作　　者：沈上越[1] 冯庆来[1] 魏启荣[1] 张志斌 

机构地区：[1]中国地质大学,湖北武汉430074 [2]云南地质调查院区调所,云南玉溪653100

出　　处：《矿物岩石》2008年第4期59-63,共5页Mineralogy and Petrology

基　　金：国家自然科学基金(批号:40372105,40772143)

摘　　要：从岩相学特征、岩石组合、岩石化学、稀土元素、微量元素、铅同位素、大地构造环境等诸方面对云南惠民-曼来地区前泥盆纪(Pt3)变质火山岩的特征进行研究,结果表明:该地区变质火山岩保留有变余间粒及变余安山结构;火山岩组合为玄武岩-安山岩-英安岩;火山岩的化学成分:基性—中性—中酸性,属亚碱性,钙碱性系列与拉斑系列并存,以低TiO2为特征;稀土模式为轻稀土富集右倾斜型;微量元素大阳离子元素富集,且普遍富Th,亏损Ti,部分亏损Cr;铅同位素组成属于冈瓦纳型;岩石化学投点绝大部分落在岛弧火山岩区,为该区原特提斯岛弧火山岩的存在提供了新证据。Based on the study of petrographic characteristics,rock assemblage,petrochemistry, REE,trace elements, lead isotopes and geotectonic setting, the characteristics of pre-Ordovician （Pt3） metamorphic volcanic rocks in the Huimin-Manlai region of Yunnan Province are described. The metamorphic volcanic rocks are characterized by a basalt-andesite-dacite assemblage, basic-intermediate-intermediate-acid in chemical composition with blasto-intergranular and blastoandesitic textures. They belong to semi-alkaline rocks,with coexistence of cale-alkaline series and tholeiite series. Their REE distribution patterns are characteristic of LREE enrichment,right inclined type, enriched in large cation elements, commonly enriched in Th,depleted in Ti and partly depleted in Cr. Their Pb isotopic composition indicates that they belong to the Gondwana type because the data points fall mostly within the field of island-arc volcanic rocks. All these characteristics provided new evidence for the existence of original Tethysan island-arc volcanic rocks in the studied region.

关 键 词：南澜沧江带南段 惠民-曼来变质火山岩 原特提斯 岛弧火山岩 冈瓦纳型 

分 类 号：P596[天文地球—地球化学] P597[天文地球—地质学]