金平龙脖河铜矿区变钠质火山岩系地球化学研究:Ⅱ.Nd、Sr、Pb同位素特征与年代学  

GEOCHEMICAL STUDIES ON SODIUM ENRICHED VOLCANIC ROCKS IN THE AREA OF LONGBOHE COPPER DEPOSIT,YUNNAN PROVINCE, SW CHINA: II. CHRONOLOGY AND CHARACTERISTICS OF Nd-Sr-Pb ISOTOPE

作　　者：常向阳[1] 朱炳泉[1] 邹日[1] 孙大中[1] 

机构地区：[1]中国科学院广州地球化学研究所,广州510640

出　　处：《地球化学》1998年第4期361-366,共6页Geochimica

基　　金：国家科学技术委员会攀登计划和中国有色金属工业总公司地质勘查总局联合资助

摘　　要：多种同位素方法定年结果证实了云南金平龙脖河铜矿区变钠质火山岩系形成于元古古。（1596±140）Ma的Pb-Pb等时年龄表明其形成时代应与大红山群变钠质火山岩相当，属中元古代。（1330±150）Ma的Sm－Nd等时年龄应代表了这套火山岩发生钠交代细碧岩化作用的时间，与哀牢山岩群和瑶山岩群的大理岩沉积时间相近。火山岩的Rb-Sr年龄和铜矿石的Pb-Pb年龄记录了晋宁期强烈的动力变质和铜的强力改造成矿事件。该区变钠质火山岩系与大红山群变钠质火山岩系在形成时代、岩石组合、同位素体系特征以及改造成矿时代上的相似性，使该区成为寻找大红山式钢铁矿床的极有利地区。Nd-Sr-Pb isotopic data indicate that the sodium enriched volcanic rocks from the Longbohe copper deposit Jinping, Yunnan Province, SW Chin4 were erupted during Proterozoic. The Pb-Pb isochron from the fresh soditum enriched volcanic rocks yields an age of (1596±140) Ma, which is interpreted as the formation age of volcanic rocks and is in agreement with the age of the Dahongshan Group (1660 Ma) within analytical errors. Sm-Nd isotopic systematics give an isochom age of (1330±150) Ma with , which represents the age of sadium metasomatic event and associated with marble sedimentation. Rb-Sr isotopic system were strongly disturbed during the subsequent geological processes. Due to the resemblance of the formation age between the volcanic rocks from Longbohe and Dahongshan areas, Nd-Pb isotopic systematics and the reworked age of the copper and iron deposits, Longbohe area has great potential for exploring of the 'Dahonongshan type' Cu-Fe deposits.

关 键 词：地质年代学 钠质火山岩 铜矿床 钕 锶 铅 

分 类 号：P618.410.4[天文地球—矿床学] P688.14[天文地球—地质学]