The Causes And Genesis Study Of Nephrite In Alamas Yutian Xinjiang China

Nephrite is the important material of our eight thousand years jade culture’sheritage and development. Xinjiang is the most important origin of nephrite. AlamasYutian region is a typical nephrite deposit in the west Kunlun Mountains. It can beconsidered as contact metasomatism which the dolomite has been invaded by theintermediate-acid granite or granodiorite. Therefore, this article selected some simplesin the contact zone to analyze the causes and genesis of nephrite.In this article we selected three specimens located in the contact zone of nephriteformation part from Alamas Yutian region which are kept in National Infrastructureof Mineral Rock and Fossil Resources for Science and Technology. After microscopicobservation, electron probe microanalytical data shows that the main mineral in thecontact zone is tremolite, diopside, dolomite, calcite and the minor mineral is apatite,pyrite, magnetite, feldspar and talc. The size of the main mineral is changeable. Theappearance of pyrite and magnetite could be a proof that nephrite is formed in a weakreduction environment.There are two processes during the forming of nephrite. In the rock formingprocess, diopside, tremolite and calcite are formed. In the jade forming process, themineral formed in the rock forming process changed into micro cryptocrystallinetremolite in the work of hydrothermal and tectonic stress. Jade forming is a diversifiedprocess in the metasomatic processes that formed the nephrite. It could be said that ifthere are appropriate elements in the hydrothermal, nephrite can be formed when thecircumstances is appropriate.This type of nephrite formation is restricted with three factors: country rocks,intrusive rocks and tectonic activities.