Calcite fabric of tectonite in an ore-controlling fault belt in the Baiyangping east ore district, Yunnan

Abstract：We may deduce the stress field orientation in the fault belt by an integrated analysis of the calcite petrofabric in tectonite of a fault belt and deduce the orientation of the paleostress using the C (compressive)-T (tensile) stress diagram of calcite with e-twins. The methods have been applied by many geologists in the practice. In the Baiyangping east ore district of Yunnan, the Huachangshan and Shuimofang faults are the principal ore-controlling structures. The petrofabric diagrams of calcite optic axis and e-twin poles both show c-axis pole maxima and girdles, indicating that the compressive stress in the c-axis direction causes gliding along the ab plane. In the C-T stress system, the principal compressive stress is oriented in a SE-NW direction and the principal tensile stress is oriented in a NE-SW direction, and the sinistral motion predominates for the Huachangshan and Shuimofang faults; the SE block of the Huachangshan fault is thrust in a NW direction, while the Shuimofang fault is thrust antithetically from NW to SE. These coincide with the macroscopic structural analysis in the field.