摘要
本文对右江盆地北缘晚二叠世大隆组、早三叠世罗楼组中的凝灰岩夹层开展地质分析研究。镜下岩石学鉴定显示其为一套玻屑、晶屑凝灰岩;而其主量元素特征分析表明属流纹质、安山质凝灰岩,具高硅、高铝、高钾特征。结合稀土元素球粒陨石标准化分布型式图及微量元素原始地幔标准化蛛网图形态特征,Y、Nb、Rb、La、Pb及Ce等稀土、微量元素的比值特征,认为凝灰岩的岩浆来源与该时期发生在凭祥一带的中—酸性火山弧活动密切相关。构造背景属于古特提斯洋向北往华南陆块之下俯冲时,形成活动大陆边缘岛弧,弧后陆壳发生伸展活动形成右江盆地。岩浆来源于洋壳俯冲发生部分熔融,且尚未与地幔发生作用,在上升过程中与陆壳物质发生混染,由火山弧的活动喷发而来。
Comprehensive geochemical analyses were conducted on the interbedded tuff collected from Late Permian Dalong Formation to Early Triassic Luolou Formation. The samples are rhyolitic and andesitic tuff, characterized by high contents of Si02, Al2O3 and K20 with vitroclastic texture. According to the REE pattern and trace elements spider diagram,the source has a close connection with volcanic arc within Pingxiang area. Active continental margin arc was formed while the Paleo-tethys Ocean subduction towards to the South China Block. Then Youjiang basin was formed after continental crust extension. It indicates that the source material was partly melted by oceanic crust subduction, contaminated with continental crust materials during the rising process.
出处
《贵州地质》
2017年第2期82-89,共8页
Guizhou Geology
基金
中国地质调查局地质调查项目<贵州1:5万独山等四幅区域地质调查>(121201010000150011-03)
2010年度贵州省地矿局局管重大科研项目之<贵州区域构造特征
构造演化与矿产空间分布关系研究>
贵州省地矿局青年地质科学研究项目<贵州松桃-江口地区寒武系炭质粘土岩地球化学特征研究>[黔地矿科合(2012-16号)]资助
关键词
凝灰岩
地球化学
右江盆地
火山弧
活动大陆边缘
Tuff
Geochemistry
Youjiang basin
Volcanic arc
Active continental margin
