论文部分内容阅读
呈中心环状的尾亚杂岩体由外环石英正长岩和内环石英闪长岩、黑云母二长花岗岩以及细粒花岗岩组成,但对两个环带是同源还是异源的认识仍存在较大分歧。鉴于黑云母是大多数中酸性火成岩中比较重要的一种镁铁质矿物,它能很好地反映寄主岩浆的属性和成岩时的物理、化学条件,因此,本文的目的在于,通过比较外环石英正长岩和内环石英闪长岩、黑云母二长花岗岩以及细粒花岗岩中黑云母的成分变化,来为两个环带是同源还是异源提供矿物学方面的佐证。结果表明,外环黑云母与内环黑云母相比,富Fe和Ti,贫Mg和Al,前者为铁质黑云母,寄主岩浆属碱性岩系;后者皆属镁质黑云母,寄主岩浆属钙碱性岩系。碱性岩系中铁质黑云母的形成主要与其晶格中Fe→Mg和3Fe2+→2Al双替代有关,而钙碱性岩系中镁质黑云母则主要与2Al→3Mg替换有关。外环与内环黑云母成分的差别,归根结底,与其寄主岩浆形成于不同的源区、产于不同的构造环境密切相关。内环各相带云母之间没有明显的演化趋势,只是细粒花岗岩中的云母比石英闪长岩和黑云母二长花岗岩中的云母富Al和F,贫Ti。结合岩石地球化学、全岩氧同位素和锆石晶形及微量元素地球化学研究成果,外环和内环之间黑云母的成分变化,排斥了外环和内环同源的可能性;内环之间黑云母成分演化趋势表明石英闪长岩、黑云母二长花岗岩以及细粒花岗岩非同一母岩浆分离结晶所致,而可能是不同期次的异源岩浆相继侵入的产物。
The central ring-shaped Meiya complex is composed of outer ring quartz syenite and inner ring quartz diorite, biotite monzogranite and granitic granite, but whether they are homologous or heterologous to the two annulus There are still big differences. Since biotite is the most important mafic mineral in moderate-acid igneous rocks, it can well reflect the properties of host magmatism and the physical and chemical conditions during diagenesis. Therefore, the purpose of this paper is to compare the characteristics of host magma Quartz syenite and inner quartz diorite, biotite monzogranite and granodiorite biotite composition changes to provide two zoning is the same or different source to provide mineralogical evidence. The results show that the outer biotite is rich in Fe and Ti, poor in Mg and Al compared with the inner biotite. The former is composed of biotite and host magma, and the latter belongs to magmatic biotite. The hosts Magma is a calc-alkaline rock series. The formation of iron biotite in alkaline rocks is mainly related to the double substitution of Fe → Mg and 3Fe2 + → 2Al in its crystal lattices, while the biotite in magmatic alkaline rocks is mainly related to the substitution of 2Al → 3Mg. The differences between the outer and inner biotite compositions are, in the final analysis, closely related to their host magma formed in different source regions and produced in different tectonic settings. There is no obvious evolutionary trend between the mica in the inner ring facies, but the mica in the fine-grained granite is more Al and F and less Ti than the mica in the quartz diorite and biotite monzogranite. Combined with the research results of lithochemistry, whole-rock oxygen isotope, zircon crystal and trace element geochemistry, the composition of biotite between the outer ring and the inner ring repels the possibility that the outer ring and the inner ring are homologous. The evolutionary trend of the biotite composition indicates that the quartzite, biotite monzogranite and granitic granite separated and crystallized due to the separation of different parent magma, which may be the result of successive intrusion of heterogeneous magma at different stages.