摘要
本文对铜官山岩体开展详细的显微镜观察鉴定,利用电子探针和LA-ICP-MS技术对岩浆岩典型矿物斜长石、角闪石和榍石进行了主量和微量元素测定。显微镜鉴定表明,铜官山岩体中存在着大量的岩浆不平衡结构:如斜长石和角闪石嵌晶结构以及针状磷灰石等。这些现象的存在表明铜官山岩体在形成过程中曾发生过一次或多次岩浆混合作用。电子探针分析结果显示,斜长石的成分环带是震荡环带,而大尺度的震荡环带可能代表了大规模的岩浆混合作用;角闪石成分TiO2-Al2O3图解、CaO/NaO2-Al2O3/TiO2图解和Mg-(Fe2++Fe3+)-LiNaKCa角闪石成因矿物族三角图解指示铜官山岩体中角闪石很可能为壳-幔混合成因。LA-ICP-MS技术对主要造岩矿物的微量和稀土元素分析表明,角闪石很可能为幔源或壳幔混合源,斜长石可能为不同分异程度岩浆的混合形成。本研究比较明确地反映了铜官山岩体的形成过程中岩浆来源和结晶动力学过程,即壳幔源区的混合交代作用,与前人通过元素-同位素手段获得的信息比较吻合。
This study presents detailed microscopic observations for the Tongguanshan pluton distributed along the Yangtze River region in south Anhui Province. Electron Microprobe and LA-ICP-MS techniques were used to analyze major and trace elements of typical minerals such as plagioclase, hornblende and sphene. Microscopic identification shows a large number of magma unbalanced structures occur in the Tongguanshan pluton, for example, embedded crystal structure of plagioclases and hornblendes, and acicular apatites. These phenomena reveal that the Tongguanshan pluton had experienced one or several times of magma mixing during its formation. EPMA results show that the plagioclase composition zoning is an oscillatory one and the large-scale zoning may represent a large-scale magmatic activity. Diagrams of TiO2-AI203, CaO/NaO2-Al2 O3/TIO2 and Mg-（Fe^（2＋） ＋ Fe^（3＋） ）-LiNaKCa of hornblende suggest that amphiboles of the Tongguanshan pluton are likely crust-mantle in origin. Using LA-ICP-MS method, trace elements and REE analyses for main rock forming minerals indicate that amphiboles may be mantle or crust-mantle mixing sources and plagioclase may form from the mixing of magma of different magmatic differentiation. Our study positively reflects that during the formation of the Tongguanshan pluton, magma source and crystallization kinetic process, i.e. mixing metasomatism of crust and mantle, coincide with previous data using elements and isotopic means.
出处
《地质学报》
CAS
CSCD
北大核心
2012年第11期1748-1760,共13页
Acta Geologica Sinica
基金
中国科学院知识创新项目(编号KZCX1-YW-15-3)
国家自然科学基金项目(编号41173057,41093072,40921002)资助成果
关键词
铜官山岩体
岩浆不平衡结构
斜长石环带
岩浆混合
Tongguanshan pluton
unbalanced structure
plagioclase zoning
amphibole
magmamixing
