摘要
北山古生代火山岩尤其是石炭纪-二叠纪火山岩的形成环境及成因备受学者关注且长期以来存在争议。本文收集了近年来发表的关于北山石炭纪-二叠纪火山岩研究的地球化学数据,岩石地球化学特征显示北山石炭纪玄武岩主要为安山玄武岩,属拉斑系列,二叠纪火山岩主要为安山玄武岩和亚碱性玄武岩,落入拉斑系列及过渡区;石炭纪玄武岩和二叠纪玄武岩均具有LREE富集的球粒陨石标准化稀土元素配分模式,轻重稀土元素分馏程度均较低。在微量元素蛛网图上,石炭纪-二叠纪遭受地壳混染的玄武岩呈现出明显的Nb-Ta亏损和微弱的Ti亏损特征,而未遭受地壳混染作用的绝大多数石炭纪-二叠纪玄武岩主要呈现出与OIB相似的"隆起"状不相容元素标准化配分模式。岩石成因分析认为,石炭纪-二叠纪玄武质岩浆可能主要来源于地幔柱,部分石炭纪-二叠纪玄武岩在形成演化过程中遭受了明显的大陆地壳混染作用,导致其出现十分相似于岛弧或活动大陆边缘的地球化学特征。结合区域构造演化分析及构造环境判别,认为石炭纪-二叠纪玄武岩均形成于大陆板内环境。
The tectonic setting and petrogenesis of the Paleozoic volcanic rocks, especially the Carboniferous and Permian volcanic rocks in the Beishan orogenic belt are problems of long controversy and have aroused much interest among geologists. The authors consider that the Carboniferous volcanic rocks belong to the andesitic basalt of tholeiite series and the Permian volcanic rocks belong to the andesitic basalt and subalkaline basalt of tholeiite and transition series. The samples collected from the Carboniferous and Permian volcanic rocks are characterized by slight enrichment of LREE and slight fractionation between LREE and HREE. The Carboniferous and Permian vol- canic rocks which were contaminated by the crust are highly depleted in Nb, Ta and slightly depleted in Ti, where- as the Carboniferous and Permian volcanic rocks which were not contaminated by the crust are similar to ocean is- land basahs （OIB） and ＂hump-shaped＂ mantle-normalized multi-element patterns without negative Nb and Ta a- nomalies. The Carboniferous and Permian basaltic rocks were derived from the mantle plume, because some basahs which belong to the Carboniferous and Permian volcanic rocks were obviously contaminated by the crust, exhibitinggeochemical characteristics of island-arc or active continental margin basahs. Combined with the research on tecton- ic evolution in the study area and the related tectonic setting discrimination diagram, the authors have reached the conclusion that the Carboniferous and Permian basahs were all formed in an intraplate setting.
作者
王国强
李向民
徐学义
余吉远
计波
朱涛
WANG Guo-qiang;L;XU Xue-yi;YU Ji-yuan;JI Bo;ZHU Tao(Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,Ministry of Natural Resources,Xi＇an Center of Geological Survey,Geological Survey of China,Xi＇an 710054,China;China Geological Survey,Beijing 100037,China)
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2018年第6期884-900,共17页
Acta Petrologica et Mineralogica
基金
国家自然科学基金项目(41703038
41202045)
中国地质调查局工作项目(DD20160012)~~
关键词
石炭纪
二叠纪
玄武岩
岩石成因
构造环境
北山
Carboniferous
Permian
basalts
petrogenesis
tectonic setting
Beishan
