内蒙古白乃庙同轴叠加旋卷构造及其控矿规律

THE COAXIAL SUPERIMPOSED VORTEX STRUCTURE AND ITS ORE-CONTROLLING PATTERNS IN BAINAIMIAO,INNER MONGOLIA

本文通过对内蒙古白乃庙地区断裂力学性质和组合特征的研究,厘定了白乃庙同轴叠加旋卷构造。浅层次脆—韧性的白乃庙断裂为主干断裂,形成于印支—燕山早期。经历了先右行走滑,后左行压扭性错动,相应地导生出两期由脆性断裂组成的旋卷构造,即早期被含金石英脉充填的张扭性帚状构造、涡轮状构造和晚期压扭性帚状构造。主干断裂导矿。早期旋卷构造容矿,矿化主要富集在帚状构造的中部和靠近收敛端的部位。晚期帚状构造是破矿构造。利用有限单元法反演了控矿断裂形成时的平面构造应力场,金矿体集中分布在剪应为值为中高值处。

The fracture mechanics of Bainaimiao area and the assemblage characteristics are discussed, and Bainaimiao coaxial vortex structure is demonstrated in this paper. The epizonal brittleductile fracture shows to be the main fracture and is believed to be formed in Indo-Sinian-early Yenshan stage and undergoing a rightward sliding first and then a leftward transpressional shearing, thus forming the vortex structure by brittle fractures of two stages, that is, the tenso-shear brush structure and the whirl structure at the early stage and the transpressional brush structure at the late stage. Ore veins are derived from the main fractures and trapped in the early-staged vortex structure. Mineralizations are found in the middle of the brush structures and near the end of convergence, and the late-staged transpressional brush structure shows to be destructive. The plane tectonic field formed during the period of the formation of the ore-controlling fracture is deduced with the finite unit method and it is found that the whole orebody concentrates where the shear stress value appears to moderately high.