大麻坪尖晶石二辉橄榄岩岩体中辉石碎斑的研究

STUDY ON A FRAGMENTED PYROXENE PHENOCRYSTAL IN DAMAPING SPINEL-LHERZOLITE ROCK BODY,BEIJING,CHINA

A mega-crystal of pyroxene (16 × 10 × 6 cm³), which shows fragmentation, is found in Damaping rock body. It consists of mosaic enstatite plate and Cr-diopside plate. The two kinds of crystal plate are equal in with (about 0.05-0.5mm). Bulk analysis is carried on py. opx. and cpx respectively and the results are compared with that of the groundmass minerals. This study reveals that the megacrystal were exposed to at least two times of solid solution seperation indicating two stress events (taking place during the emplacement of the rock body), further continous movement of upper mantle and the heterogeneous stress for different parts of the moving mantle.