新疆哈密库姆塔格沙垄北段韧性剪切带特征及其地质意义

通过野外调研和显微构造测试,分析了新疆哈密库姆塔格沙垄北段韧性剪切带几何学、运动学和动力学特征,探讨了韧性剪切带的演化及其地质意义,详细研究了韧性剪切带S-C面理、波状消光、变形条带、变形纹、机械双晶、亚颗粒、动态重结晶颗粒、核幔结构、压力影、旋转碎斑系、显微裂隙和石英、方解石c轴组构等显微构造特征,并对其形成机制进行了解析。

DUCTILE SHEAR ZONE AND ITS GEOLOGICAL SIGNIFICANCE IN NORTHERN KUMUTAGESHALONG OF HAMI, XINJIANG

The prospecting area, characterized by development of ductile shear zone, is located in northern Kumutageshalong of Xinjiang. Through fieldwork and lab testing, in this paper the geometric, kinematic and dynamic features of the ductile shear zone are analyzed, and the evolution of the ductile shear zone and its geological significance are discussed. The main conclusions are listed as follows:1. The north of the ductile shear zone is the F1 fracture where diorite is developed, while the south of the ductile shear zone is the Yamansu deep fracture.2. The microstructure features of the ductile shear zone are studied in detail, including the S-C foliation, deformation bands, deformation lamellae, deformation twins, subgrains, dynamically recrystallized grains, core and mantle textures, pressure shadows, relic phenocrysts, wavy extinction, quartz and calcite c-axis, etc., together with their formation mechanisms.3. The ductile shear zone underwent multi-stages of shearing from ductile (dextral)-brittle-ductile (sinistral)-ductile-brittle (dextral)-brittle (sinistral). In the first stage the principal stress (σ1) is along ca. 140°∠14°, and the paleo-stress is estimated at about 100.95MPa; In the second stage the principal stress (σ1) is along ca. 220°∠65°, and the paleo-stress is estimated at about 48.19MPa; In the third stage the principal stress (σ1) is along ca. 300°∠65°, and the paleostress is estimated at about 176 MPa; And in the last stage the principal stress (σ1) is along ca. 60°∠65°. 4. By systematically measuring the angles of S-C foliations, it can be calculated that the displacement of ductile shear zone is at a magnitude of about 3.77km, and the extensional capacity is estimated at about 0.614%.5. The ductile shear zone we discussed is a part of the Qiugemingtashi-Huanshan ductile shear zone in eastern Tianshan. It controls the evolution of the tectonics in eastern Tianshan, and the distribution of the gold metallogenic belt in Kanggu′er-Huanshan area. The secondary ductile shear zone distributed at its north side is also favorable for gold mineralization.