辽西建平县义县组火山岩形成构造环境的地球化学鉴别  

Geochemical Discrimination of Tectonic Environments of Volcanic Rocks of Yixian Formation in Jianping of Western Liaoning

作　　者：彭艳东[1] 黄菲[2] 邢德和[3] 张志斌[3] 

机构地区：[1]东北大学秦皇岛分校,河北秦皇岛066004 [2]东北大学资源与土木工程学院,辽宁沈阳110819 [3]沈阳地质矿产研究所,辽宁沈阳110034

出　　处：《东北大学学报（自然科学版）》2013年第7期1012-1016,共5页Journal of Northeastern University(Natural Science)

基　　金：国家自然科学基金资助项目(41272062);国土资源大调查项目(1212011120662)

摘　　要：对辽西建平县平庄-马厂盆地的火山岩进行了岩石学、地球化学、同位素年代学研究.结果表明,火山岩属白垩纪.义县组火山作用可分为2个亚旋回.火山岩主要为流纹岩类、粗面岩类和粗安岩类.义县旋回火山岩属高钾钙碱性岩石系列.火山岩具有高SiO2,Al2O3,K2O,Na2O和低MgO,TiO2的特征.火山岩富集大离子亲石元素(LILE)K,Rb,Sr,Zr,Ba,Pb,Li等,高场强元素(HFSE)Nb,Ti,P及相容元素Co,Ni,Cr,V亏损.火山岩为轻稀土富集型,总体显示弱负铕异常、无铈异常.对火山岩形成的构造环境的地球化学判别,表明义县组火山岩成岩物质主要来源于下地壳的部分熔融,岩浆在上升过程中受到了一定程度的上地壳物质的混染.火山岩形成于板内岩石圈不均匀伸展作用环境,具有大陆板内造山带火山岩的基本特征.Petrology,geochemistry,isotope geochronology of the volcanic rocks distributed in Pingzhuang-Machang basin of Jianping of western Liaoning were studied.The results showed that the volcanic rock is the Cretaceous.The volcanism of Yixian formation may be divided into two sub-cycles.The volcanic rocks mainly consist of rhyolites,trachyte and trachyandesites.The volcanic rocks belong to the high-K calc-alkaline magmatic series.The volcanic rocks are characterized by components of high SiO2,Al2O3,K2O and Na2O,and comparatively low MgO and TiO2.The volcanic rocks are obviously enriched in large ion lithophile elements（K,Rb,Sr,Zr,Ba,Pb and Li）,and depleted in high field-strength element（Nb,Ti,P）as well as compatible elements（Co,Ni,Cr and V）.The volcanic rocks is rich in LREE.There is a slight negative Eu anomaly and no Ce anomaly.A detailed geochemical discrimination of the selected elements allowed us to identify that the volcanic rocks of Yixian formation mainly derived from the partial melting of lower crust materials,but also has been contaminated by upper crustal materials during its ascent process in some degree.The volcanic rocks of Yixian volcanic cycle were generated in response to lithosphere inhomogeneous extension in the continental intraplate orogenic belt.They have the basic characteristics of continental intra-plate volcanic rocks.

关 键 词：建平县 义县组 地球化学判别 岩石圈伸展作用 板内造山带 

分 类 号：P591[天文地球—地球化学]