深部地壳镁铁质岩石(斜长角闪岩)叶理的组成及形成机制分析--以辽东海城地区变质镁铁质岩石为例

高级变质镁铁质岩石叶理形成于地壳深部环境，对其组成及形成机制的深入研究有助于讨论在深部地壳(下地壳)环境中岩石的表现与流动过程。以辽宁海城马风地区广泛出露的斜长角闪岩为例，对变质镁铁质岩石中几种不同类型叶理的组成及形成机制进行初步探讨。显微构造分析结果表明，变质斜长角闪岩中主要发育三种具有不同特点的叶理构造型式：条带状、糜棱状和片麻状。作为岩石叶理的主要组成矿物。角闪石对叶理的形成贡献最大。斜长石在不同类型岩石中对叶理的形成作用不同。组成叶理的斜长石和角闪石矿物对的温压测算结果表明，它们形成于426～532MPa和58l℃～639℃之间。变质基性岩中叶理的形成是这种温度和压力条件下多种机制(包括晶体的定向重结晶作用、应力作用下的变质分异、晶质塑性变形、亚颗粒旋转动态重结晶)共同作用的结果。

Mechanisms of Development and Components of Foliations in Metamorphosed Mafic Rocks (Amphibolites) from Lower Crust--Taking the metamorphic mafic rocks from Haicheng, Liaodong Peninsula for example

Foliations in high--grade metamorphic mafic rocks are generally formed at lower crustal levels. The study of the components and mechanisms of formation of such foliations is helpful to elucidate the rheological behavior and flow processes of rocks in the lower crust. Samples from the Liaohe Group in Mafeng area of Haicheng, Liaoning and the components of foliations and a(c)mechanisms of foliation development in the metamorphosed mafic rocks are investigated. Microstructural analysis reveals the existence of different types of foliations, banded, mylonitic and gneissic. It is shown that as one of the major components, hornblende grains played the most important role in the development of faliation. Plagioclase has different effects in different rocks. Geothermometer and geobarometer analyses give the temperature and pressure ranges for the development of the foliations. The foliations are formed by an association of several different processes (including oriented recrystallization, stress--driven metamorphic differentiation, crystalline plasticity and dynamic recrystallization by subgrain rotation, etc.) under the T/P conditions.