The Genesis and Evolution of Alpine-Type Ultrabasic Rocks in Western Junggar, Xinjiang

The alpine-type ultrabasic rocks of the studied area have undergone plastic deformation under a temperature about 800--1200℃, a pressure about 0.9--1.68 GPa and differential stress of 0.2--0.35 GPa in relatively dry conditions, forming ultrabasie mylonite with porphyroclastic and mylonitic textures, Primary crystallized silicate melt inclusions and melt-fluid inclusions are discovered in porphyroclastic minerals and ore-forming chrome spinel. These rocks are formed under relatively stable physico-chemical conditions through liquid immiscibility of silicate melts, at 1200°-- 1300° and 1.1--1.38 GPa, equivalent to a depth of 40--50 km. No inclusion has been found in recrystallized secondary olivine and pyroxene, indicating that the plastic deformation happened after the formation of the rocks.

The Genesis and Evolution of Alpine-Type Ultrabasic Rocks in Western Junggar,Xinjiang

Abstract The alpine-type ultrabasic rocks of the studied area have undergone plastic deformation under a temperature about 800–1200°C, a pressure about 0.9–1.68 GPa and differential stress of 0.2–0.35 GPa in relatively dry conditions, forming ultrabasic mylonite with porphyroclastic and mylonitic textures. Primary crystallized silicate melt inclusions and melt-fluid inclusions are discovered in porphyroclastic minerals and ore-forming chrome spinel. These rocks are formed under relatively stable physico-chemical conditions through liquid immiscibility of silicate melts, at 1200°– 1300° C and 1.1–1.38 GPa, equivalent to a depth of 40–50 km. No inclusion has been found in recrystallized secondary olivine and pyroxene, indicating that the plastic deformation happened after the formation of the rocks.