摘要
银-额(银根-额济纳旗)盆地及其邻区二叠纪火山岩分布广泛,目前对其成因和构造背景研究还很薄弱。对该区火山岩岩石学和元素地球化学特征进行研究,为恢复二叠纪盆地性质与古构造环境提供了岩石地球化学约束。分析的二叠纪火山岩主要岩石类型为玄武岩、玄武安山岩和安山岩,显示亚碱性系列的特征。Mg#介于0.53～0.86之间,高场强元素Nb、Ta、Ti明显亏损,岩石轻度富集轻稀土元素(LREE),(La/Yb)N=1.68～6.10,Eu亏损不明显(δEu=0.64～0.99),稀土元素配分曲线右倾较缓。总体上既显示了板内构造环境的特征,又具有俯冲带地球化学的印记。综合沉积建造特征和邻区的研究结果,认为银-额盆地二叠纪火山岩形成于板内裂谷环境,且很可能与地幔柱事件有关,岩浆在上升过程中受到地壳物质不同程度的混染。
Permian volcanic rocks are widespread in Yingen-Ejin Banner basin and its neighboring areas,and their genesis and tectonic setting remain a problem of much controversy.Based on a petrologic and geochemical analysis of Permian volcanic rocks in the study area,this paper attempts to clarify the palaeo-tectonic setting and provides independent evidence for understanding the nature of the basin.The volcanic rocks are dominated by basalts,basaltic-andesite and andesite,which fall into the sub-alkaline series.Mg# content of this suite ranges from 0.53 to 0.86,exhibiting strong depletion of the high field strength elements Nb,Ta and Ti and slight enrichment of LREE.In terms of REE,（La/Yb）N content ranges from 1.68 to 6.10,showing insignificant Eu depletion（δEu=0.64～0.99） and slightly right-oblique REE distribution patterns.These data show not only the characteristics of an intraplate setting on the whole but also the signature of a subduction zone.Combined with the sedmentary formation characteristics,the authors have reached the conclusion that the Permian magmatic activity of the study area was generated in an intraplate setting,with variable degrees of contamination of the crust during magmatic ascending,related probably to the mantle plume event.
出处
《地质通报》
CAS
CSCD
北大核心
2011年第6期923-931,共9页
Geological Bulletin of China
基金
中国地质调查局国土资源大调查项目<西北地区中小盆地群油气资源远景调查>(编号:1212010733506)
教育部中央高校基本科研业务费专项基金项目<川西北石棉-泸定-丹巴地区新元古代基性-超基性岩成因及构造环境研究>(编号:CHD2010JC038)
