Study On The Cause And Deformation Features Of The Quarts Veins In The Luolin Rock Group,in Jiacha County,Tibet

The yarlung zangbo river is the combining site of Gangdese block and Himalaya block. Lorraine terrain is unordered flysch assise, a typical subducted accretionary wedge, which is multi-phase highly-deformed and with metamorphous greenschist facies. It was formed during late Triassic epoch as the yarlung zangbo river collided and subducted northward. There are mainly two stages of tectonism developed in Lorraine terrain, one is subduction phase in the early stage and another is collision phase in the late stage. Many quartz veins are found in the research zone, greatly affected by its geological struction.There are widespread quartz veins of various shapes in Lorrain terrain. Quartz veins that were formed in the early stage have flexible and flow folds, angular folds, porphyroclast system, rootless ditch-shaped folds, etc. as quartz veins have constantly changed shapes and been influenced by bedding shear. Quartz veins that were formed in the main collision process are straight and orderly. They have cleavages that are penetrative and consistently south-dipping.After experimental analysis on the quartz veins, Roman spectrum showed the main ingredients of fluid inclusion are CO2、H20 and N2. Based on micro thermometry, the formation temperature of the inclusion is 180℃~260℃, the pressure captured is 120~160MPa and the salinity is 0.22~7.21wt%. Fluid inclusions in Lorrain terrain are mainly rich in CO2 and with low salinity.According to the data of experiment on quartz vein fluid inclusions, the level of the deformation and metamorphose of this area is low and it is light green schist. The main cause of quartz vein formation is dissolving-recrystallization. The formation causes of quartz veins formed at two stages have uniformity. Within different samples, the span of temperature, salinity, and density of inclusions is big, illustrating that the formation of inclusions has been influenced by consistent progressive deformation, and that the main phase formation has an influence of modification on early-stage formation.