摘要
云南剑川金河岩体中的硅化霓辉正长斑岩含有较多的镁铁-超镁铁质深源岩石包体。岩相学研究表明,伴随交代蚀变,其主岩和各类包体岩石中普遍发育沿矿物粒间和矿物晶体裂隙或解离纹贯入或穿插的呈网状和细脉浸染状分布的黑色不透明物质。对该物质进行了电子探针及扫描电镜和能谱分析,发现其组成以微晶硅酸盐矿物为主,含少量微晶石英,尤其是含有微晶地幔标型矿物——含钛磁铁矿(或镜铁矿)和含铬自然铁;后两者与硅酸盐矿物构成超显微熔离结构交生。研究认为,这种物质组成和特征,是具超临界和熔浆性质的地幔流体的微观表现,其活动所引发的交代蚀变表现为硅化、钠化及深源包体中的暗色矿物由辉石→角闪石→黑云母的退变序列。这一地幔流体作用微观踪迹的揭示,对于分析和论证滇西地区新生代多金属成矿的深部地质作用规律具有重要的理论和现实意义。
There exist quite a few deep xenoliths in silicified aegirine syenite porphyry within Jinhe intrusive body of Jianchuan, western Yunnan Province. Petrographic researches show that black opaque materials are widely distributed reticulately along intergranular cracks of minerals, crystal fissures and cleavages in association with metasomatic alteration in mafic-ultramafic xenoliths and their host rocks. These black opaque materials were tested by electron microprobe analysis, SEM and energy spectrum analysis. The authors found that they are mainly composed of microcrystalline silicates together with minor quartz and, especially, Ti-magnetite （specularite） and Cr-ferrite that serve as typomorphic minerals of the mantle. Both ferruginous minerals and microcrystalline silicates show characteristics of liquation in the backscattered electron image. It is concluded that the compositions and characteristics of the materials are microscopic reflection of supercritieal and molten-lava mantle fluids. The metasomatie alteration caused by mantle fluids finds expression in silication, soda metasomatism and retrograde reaction in order of pyroxene →amphibole→biotite in dark minerals of deep xenoliths. The conclusions drawn by the authors have theoretical and practical significance for the study of the regularity governing the deep geological process of polymetallic mineralization.
出处
《矿床地质》
CAS
CSCD
北大核心
2009年第2期185-194,共10页
Mineral Deposits
基金
国家自然科学基金项目(批准号:40773031)
中国地质大学地质过程与矿产资源国家重点实验室开放课题基金项目(GPMR200705)
成都理工大学矿物学岩石学矿床学国家重点(培育)学科建设项目的资助
关键词
地质学
黑色不透明微晶固体
地幔标型矿物
地幔流体作用
金河岩体
剑川
云南
geology, black opaque microcrystalline solid, mantle typomorphic minerals, mantle fluid process, Jinhe intrusive body, Jianchuan, Yunnan
