Structural deformation of the Jiajika dome in western Sichuan

The Jiajika dome in western Sichuan is famous for its abundant spodumene resources. Both the NS- and EW-trending convergence of the North China,Yangtze and Qiangtang blocks resulted in the complex structural deformation of the Jiajika dome. Generally,the Jiajika dome appears as a concentric anticlinorium where the coral strata are gentle,and become gradually steeper outwards. There are A-type isoclinal recumbent folds,ptygmatic quartz veins and symmetrical pressure shadows on the top of the dome. The metamorphic minerals on the limbs are almost strenched and rotated into asymmetrical formes,displaying the nature of a positive shear movement from the limbs outwards. The vertical tight folds and overturned folds occur in the steeper strata around the dome. On the whole,the Jiajika dome is interpreted as the products of joint tectonism and magmatism,and has successively experienced two phases of tectonic movements,i. e.,two phases of NS- and EW-trending tectonic compression.