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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。
In this paper, we carried out a detailed microscopic observation and identification of the Tongguanshan rock mass. The main and trace elements of the plagioclase, hornblende and limpinite, which are typical magmatic rocks, were determined by electron probe and LA-ICP-MS. Microscopic identification shows that there are a large number of magmatic imbalances in the Tonggoushan pluton, such as plagioclase and amphibole inlaid structure and acicular apatite. The existence of these phenomena indicates that one or more magmatic mixing events occurred in the formation of the Tongguanshan pluton. The results of electron probe analysis show that the component zone of plagioclase is an oscillating zone, while the large-scale oscillatory zone may represent large-scale magma mixing. The composition of the hornblende is represented by TiO2-Al2O3 and CaO / NaO2-Al2O3 / TiO2 illustration and Mg- (Fe2 + + Fe3 +) - LiNaKCa hornblende mineralogy Triangle diagrams indicate that hornblende in the Tongguanshan pluton is probably due to the crust-mantle mixing. Trace and rare earth element analysis of major rock-forming minerals by LA-ICP-MS shows that amphibole is probably a mixed source of mantle or crust and mantle, and plagioclase may be a mixed formation of magmas with different degrees of differentiation. This study more clearly reflects the magma source and crystallization kinetics during the formation of Tonggunshan pluton, that is, the mixed metasomatism of crust and mantle source, which is in good agreement with the previous information obtained by elemental-isotopic method.