河北矾山岩体边缘弧形挤压带岩石的显微构造研究

矾山岩体是一环状碱性超镁铁杂岩体。靠近该岩体的白云岩已变成白云质大理岩,岩层产状迅速变陡。沿岩体边缘形成一弧形挤压带。挤压带中,大理岩具明显的形态组构,其片理面平行于挤压带,岩石晶粒的轴比为2.6:1:0.5。本文提出一种计算f双晶面上分剪应力系数的新方法和一种关于岩体形成机制的新认识。

A MICROSTRUCTURE STUDY OF ROCKS WITHIN A CURVED COMPRESSIVE ZONE AROUND THE FANSHAN PLUTON OF HEBEI

There is a kali-alkaline ultramafic complex in the Fanshan of Hebei.Nearthe boundary of the pluton tbe dolomite recrystallized into dolomiticmarble and its dip sharply become steeper downwards, forming a ring-shapedcompressive zone with a normal fault. The analyes of microstructures andfabric of the marble in the compressive zone shows that the marble hasa significant grain shape fabric with X: Y: Z=2.6: 1: 0.5. Near thepluton, the schistosity is parallel to the compressive zone. Using the ftwinning of dolomite as a paleo-piezometer, it is showed that thedifferential stress during the deformation of marble is unusual high, maybe more than 2000 bar. It is suggested that this may be a impactedstructure instead of a diapir. A new method is proposed for calculatingthe component shear stress coefficient on the f twin plane.