云南腾冲全新世火山岩地球化学特征及其成因  

A study on the geochemical characteristics and petrogenesis of Holocene volcanic rocks in the Tengchong volcanic eruption field,Yunnan Province,SW China

作　　者：李欣[1] 刘嘉麒[1] 

机构地区：[1]中国科学院地质与地球物理研究所,新生代地质与环境研究室,北京100029

出　　处：《岩石学报》2012年第5期1507-1516,共10页Acta Petrologica Sinica

基　　金：国家自然科学基金委重大国际合作研究项目(41020124002);国土资源部深部探测技术与实验研究专项课题(201011060)联合资助

摘　　要：通过对腾冲火山群的黑空山、打莺山和马鞍山火山岩主量元素、微量元素、Sr-Nd-Pb同位素地球化学的研究表明,腾冲全新世火山岩为高钾钙碱性系列,包括粗面玄武岩、玄武粗安岩、粗面安山岩和英安岩。该套火山岩富集大离子亲石元素和轻稀土元素,亏损Nb-Ta-Ti不相容元素,具有高的87Sr/86Sr比值(0.705862～0.710614),低的143Nd/144Nd比值(0.511941～0.512526)和较高的放射性成因Pb同位素组成(208Pb/204Pb=38.962～39.155;207Pb/204Pb=15.620～15.659;206Pb/204Pb=17.872～18.269)。主量、微量和同位素地球化学研究表明,腾冲全新世三座火山的岩浆源区为富集地幔,地幔富集与古洋壳俯冲有关。它们是由相同的地幔源区经历了不同的岩浆演化阶段的产物,打莺山岩浆演化程度最高,黑空山次之,马鞍山岩浆演化程度最弱。通过腾冲全新世火山岩与藏南碰撞后钾质火山岩的地球化学成分对比,Sr-Nd-Pb同位素地球化学成分存在着明显的不同,暗示两者的源区存在差异。Studies of major element,trace element and Sr-Nd-Pb isotopic compositions of the Holocene volcanic rocks in the Tengchong volcanic eruption field,including Heikongshan,Dayingshan and Maanshan volcanic rocks,indicate they are high potassium calc-alkaline series rocks including trachybasalt,basaltic trachyandesite,trachyandensite,and dacite.These rocks are enriched in LILE and LREE,and depleted in Nb-Ta-Ti in mantle-normalized incompatible trace element patterns.They have relatively high 87Sr/86 Sr（0.705862 ～ 0.710614）,low 143 Nd/144 Nd（0.511941 ～ 0.512526） and relatively high radiogenic Pb isotopes（208 Pb/204 Pb = 38.962 ～39.155,207Pb/204Pb =15.620 ～15.659 and,206Pb/204Pb =17.872 ～18.269）.The geochemical characteristics of the Holocene volcanic rocks in the Tengchong volcanic eruptive field indicate that the magma sources of Heikongshan,Dayingshan,Maanshan are from enriched mantle which possibly resulted from palaeo-oceanic crust subduction.The magma sources of these three volcanoes are same but with different evolution stage.The magma evolution of Dayingshan is higher than that of Heikongshan and Maanshan.The comparison with geochemical characteristics of post-collisional K-rich rocks in South Tibet shows that the magma sources of Holocene volcanic rocks in the Tengchong volcanic eruption field and post-collisional K-rich rocks in South Tibet are different.

关 键 词：高钾钙碱性火山岩 岩石地球化学 全新世 腾冲 

分 类 号：P588.14[天文地球—岩石学]