递增变质作用中变斑晶形成的时间标志——兼论阿尔泰地区变质带形成顺序

根据变质构造和镜下显微组构的研究,提出了与Zwart,H.J.(1962,1963)的变斑晶包体S形构造成因观点不同的解释。结合包体和基质矿物成分、组构特征建立了递增变质作用中变斑状特征变质矿物形成的相对时间标志。以此确定了阿尔泰变质地带递增变质作用过程中一系列特征变质矿物及其相应的变质带的形成顺序。

THE WICROSTRUCTURE CRITERIA OF INCLUSION IN PORPHYROBLASTS ESTABLISHING THE PROGRESSIVE METAMORPHISM EVOLUTION OF ALTAY HERCYNIDE

Many textural criteria have been proposed for elucidating the time relationship between the growth of porphyroblasts and foliation development(Z-wart 1960,1962, Rosenfeld 1968.1970, Spry l969,Vernon 1978) .Porphyroblast rotation has been regarding as the standard model interpreting a curved inclusion trails in porphyroblast. The purpose of this paper is to present a new microstructure criteria timing porphyroblasts growth and discuss the development sequence of relavent metamorphic zones in Altai metamorphic belt.We believe that the"S"shape inclusion trails in porphyroblasts may form in different ways.According to our study on macrostructure and microstructure, the main way is that the matrix minerals transposing from S1 to S2 continuly during main episod deformation are trapped continualy by growing porphyoblast.The characteristics of porphyroblasts formed in each stage of main episod of deformation differ in grain size, shape, mineral composition and pattern of inclusion and matrix and the relationship between Si(Schistosity of incl-usion)and Se (Schislosity of matrix).We present a new criteria timing the growth of porphyroblasts according the difference and determing the development zoes.sequence of porphyroblastic index minerals and corresponding metamorphic.