斜方角闪石组合的变质压力类型

斜方角闪石组合是前寒武纪变质岩系中的一种特殊的岩石类型，以富Mg、Al，贫Ca、K为特征，矿物组成为堇青石、斜方角闪石和富铝矿物如Al2SiO5、十字石、石榴石、斜长石、云母类和单斜角闪石类。其分布遍及欧亚及大洋洲各地的古老岩系中，在许多产地与硫化物矿床有密切关系。按其变质条件可以分为低压和高压两种类型：低压型以堇青石-直闪石-镁铁闪石组合为特征；高压型以蓝晶石、铝直闪石组合为特征，有时有石榴石。堇青石、十字石构成围绕蓝晶石周围的冠状体，成为变质地体经历近绝热抬升的极好证据。本文论述其特征矿物组合、结构的演化、所涉及的变质反应及其形成的构造环境。

A study on the baric types of the orthoamphibole association

The orthoamphibole association is a special rock type developed mostly in Precambrian metamorphic terranes. It is rich in Mg and Al but depleted in Ca and K. Its major mineral constituents include cordierite, orthoamphibole, Al 2SiO 5 minerals, staurolite, garnet, plagioclase, micas and clinoamphiboles. Associations of this kind are distributed in a lot of ancient metamorphic complexes throughout the world, with some of them closely related to sulfide deposits. According to metamorphic conditions, the orthoamphibole association can be tentatively divided into two types: the lower pressure type and the high pressure type. The former type is characterized by the cordierite- anthophyllite-cummingtonite association, while the latter type is Al 2SiO 5 minerals-gedrite association, sometimes with garnet. The Al 2SiO 5 in high_pressure terranes is kyanite. Cordierite and staurolite mainly formed corona textures surrounding kyanite or garnet, indicating the nearly adiabatic uplift of a metamorphic terrane. The present paper deals with the mineral paragenesis, the baric types, the related metamorphic reactions and the conditions under which these rocks were formed.