满洲里南部白音高老组流纹岩锆石U-Pb定年及岩石成因  

Zircon LA-ICPMS U-Pb dating and petrogenesis of rhyolites in Baiyingaolao Formation from the southern Manzhouli,Inner-Mongolia

作　　者：苟军[1] 孙德有[1,2] 赵忠华[3] 任云生[1] 张学元[3] 付长亮[4] 王晰[1] 魏红艳[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]西北大学大陆动力学国家重点实验室,西安710069 [3]核工业240研究所,沈阳110032 [4]中国国土资源航空物探遥感中心,北京100083

出　　处：《岩石学报》2010年第1期333-344,共12页Acta Petrologica Sinica

基　　金：国家"973"项目(2009CB219303);中国核工业地质局项目;西北大学大陆动力学国家重点实验室开放课题基金联合资助;"东北亚生物演化与环境教育部重点实验室";吉林大学"211"工程三期建设项目;2009年教育部基本科研业务经费("吉林大学创新团队发展计划")支持

摘　　要：满洲里南部白音高老组火山岩主要由流纹岩组成,含少量珍珠岩和流纹质凝灰岩。LA-ICPMS锆石U-Pb定年结果显示,流纹岩形成于141～139Ma的早白垩世早期。岩石地球化学研究表明,火山岩具有高硅富碱、贫钙镁和高FeO^T/MgO比值的特征;稀土丰度总量较高(∑REE介于103×10^(-6)～488×10^(-6)),轻重稀土分馏明显[(La/Yb)_N=4.12～30.94)],Eu负异常显著(δEu=0.12～0.46);微量元素以富集Rb、Th、U、K,强烈亏损Ba、Sr、P、Ti,中等亏损Nb、Ta和高Ga/Al值为特征,与A-型花岗岩特征相似。锆石^(176)Hf/^(177)Hf比值介于0.282785～0.282970之间,ε_(Hf)(t)值均为正值,介于3.78～9.98之间。流纹岩岩浆来源于斜长石稳定区玄武质下地壳物质的部分熔融,形成于非造山板内伸展构造环境。The volcanic rocks of Baiyingaolao Formation in the southern Manzhouli are composed of rhyolites and a little amount of perlites and rhyolitic tuffs.U-Pb age determinations of zircon by LA-ICPMS show the rhyolites were formed at Early Cretaceous,and their formation ages ranged from 141Ma to 139Ma.The geochemical study suggests that rhyolites are rich in silicon,alkalis,poor in calcium,magnesium and have high FeO^T/MgO ratio.All samples have similar characteristics of REE patterns which are characterized by relatively high total REE contents(ΣREE = 103×10^(-6)-488×10^(-6)),significant fractionation of HREE and LREE[(La/Yb)_N = 4.12-30.94]and strong negative Eu anoalies(δEu = 0.12-0.46).The trace element geochemistry are characterized evidently by enrichment of Rb,Th,U,K,strong depletion of Ba,Sr,P,Ti,mediate depletion of Nb,Ta and higher Ga/Al ratio.The geochemical characteristics of rhyolites show an affinity with the A-type granite.The initial ^(176)Hf/^(177) Hf ratios of the magmatic zircons from rhyolites vary in 0.282785-0.282970 and the correspondingε_(Hf)(t) values are positive ranging from 3.78 to 9.98.The characteristics above indicate that the rhyolitic magma was origrinated from partial melting of basaltic lower crustal materials in the plagioclase-stable field.Combining with the regional researching results,we suggest that the rhyolites were formed in an intra-plate anorogenic extensional setting.

关 键 词：白音高老组 流纹岩 锆石U-PB年龄 岩石成因 满洲里 

分 类 号：P588.141[天文地球—岩石学]