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幔源岩石包体研究,是认识上地幔岩石圈物质组成、幔源岩浆演化及壳幔动力学过程的重要手段。铜陵地区小铜官山石英二长闪长岩中发育有微粒闪长质包体,并且这些微粒闪长质包体中不均匀地分布着镁铁质团块,三者的形成过程可视为铜陵地区岩浆演化的缩影,为了解本区深部岩浆作用过程提供了有力的证据。在前人研究的基础上,笔者借助电子探针、扫描电镜、电镜能谱和二次飞行时间离子探针(Tof-SIMS)对产于铜陵地区微粒闪长质包体中的镁铁质团块进行了详细的研究,首次获得了一套精确的矿物化学资料和元素分布图,总结了镁铁质团块的特征,并讨论了本区的深部岩浆作用过程。矿物学研究表明,镁铁质团块中的角闪石和辉石均已发生了不同程度的透闪石化和阳起石化蚀变,蚀变过程中,从镁钙闪石到镁角闪石,再到透闪石,随着Si的增加,角闪石呈现出Mg的富集和Ti、Al贫化的特点。团块中的富Cr磁铁矿、Ti磁铁矿和少量的铝直闪石指示了其具有深源性。Tof-SIMS元素分布图显示,透闪石主要由Al、Si、Ca、Sc、V、Cr、Mn、Cu和Sr元素组成,透辉石主要由Si、Mg、Ca、Cu和Rb组成。在铜陵地区,上地幔部分熔融形成一套玄武岩浆,受岩浆底侵作用影响,玄武岩浆上侵,进入下地壳深位岩浆房,与下地壳硅镁层发生同化混染作用,形成一套轻度演化的中基性(辉长质)玄武岩浆,镁铁质团块就是这类中基性玄武岩浆直接结晶形成的。后受构造作用影响,这类中基性玄武岩浆上侵到中地壳岩浆房(12~16 km),与中地壳的变质岩系发生同化混染和结晶分异作用形成一套中性闪长质岩浆,微粒闪长质包体就是这套闪长质岩浆发生结晶分异作用而形成的。镁铁质团块和微粒闪长质包体清楚地解释了铜陵地区深部岩浆作用过程,并有力地证明了铜陵地区中地壳的闪长质岩浆来源于下地壳的壳幔混源岩浆。
The study of mantle-derived rock inclusions is an important means to understand the lithospheric material composition, mantle-derived magmatic evolution and crust-mantle dynamics processes of the upper mantle. There are fine-grained dioritic inclusions in the small Tongguanshan quartz diorite in Tongling area, and the mafic clumps are unevenly distributed in the dioritic inclusions of these grains. The formation process of the three can be considered as the Tongling The microcosm of regional magmatic evolution provides strong evidence for understanding the magmatic process in the area. Based on the previous studies, the author used the electronic probe, SEM, TES and Tof-SIMS to analyze the ferrochrome clusters in the fine-grained dioritic inclusions in Tongling area For the first time, a set of accurate mineralogical data and elemental maps were obtained. The characteristics of mafic clumps were summarized and the deep magmatic processes in this area were discussed. Mineralogical studies have shown that amphiboles and pyroxenes in mafic clumps have undergone tremolite and Yangyang petrochemical alteration in varying degrees. During the alteration process, from magnesite to amphibole, Then to tremolite. With the increase of Si, amphiboles show the enrichment of Mg and the depletion of Ti and Al. Rich Cr magnetite, Ti magnetite and a small amount of aluminum tremolite in the clump indicate its deep origin. The Tof-SIMS elemental distribution shows that tremolite is mainly composed of Al, Si, Ca, Sc, V, Cr, Mn, Cu and Sr elements and diopside mainly consists of Si, Mg, Ca, Cu and Rb. In the Tongling area, the upper mantle partially melts to form a set of basaltic magmas. Influenced by the magma underplating, the basalt magma invades into the deep magma chamber of the lower crust and assimilates and mixes with the magnesia layer in the lower crust to form a set of light Degree of evolution of the basic (glorious quality) basaltic magma, mafic clumps is such a direct crystallization of basaltic magma formed. Affected by the tectonic effect, these basaltic basaltic magmas invaded the middle crust magma chamber (12-16 km), assimilating contamination and crystallization differentiation with the metamorphic rocks of the middle crust to form a set of neutral dilatances Magmatic magma, particle dioroplane inclusions is formed by the crystallization of dioritic magma. The mafic mass and the fine-grained dioritic inclusions clearly explain the deep magmatic processes in Tongling area and strongly demonstrate that the dioritic magma in the middle crust of Tongling area originated from crust-mantle mixed-sourced magmas in the lower crust.