相山铀矿田西部成矿构造应力场及与铀矿化关系

THE METALLOTECTONIC STRESS FIELD IN THE WEST OF THE XIANGSHAN URANIUM OREFIELD AND ITS RELATIONS TO URANIUM MINERALIZATION

相山铀矿田是我国最大的火山岩型铀矿田。本文选择矿田西部地区，通过节理、裂隙测量和数值模拟，重建和恢复了区内成矿构造应力场，并在此基础上，探讨铀矿化在构造应力场内的分布规律和火山岩中铀元素在构造应力作用下的迁移、集散特征。结果表明：铀矿床多分布在剪应力值产生急剧变化的梯度带、应力值偏低一侧的应力“缓冲带”部位，且有从矿床、矿点到异常点，剪应力值逐渐降低的变化趋势。火山岩中的铀元素在构造应力驱动下，向应力梯度减小的方向迁移，并参与了成矿作用。

The Xjangshan uranium orefield is the largest volcanics type uranium orefield in China.Having selected the western part of the orefield as a study area,the present paper made a prelimi-nary study on the tectonic stress field of metallogenic faults that occur in volcanic cover and di-rectly control uranium mineralization Based on measurement of joints and fissures as well as fi-nite-element numerical simulation in Julongan sector,the paper reconstructed the metallotectonicstress field of the area and,on such a basis,investigated the distribution of uranium mineralizationin the tectonic stress field and the migration and dispersion of uranium volcanic rocks under theaction of tectonic stress.The following understanding has been obtained:(1).The metallogenic fault zones,ore-control joints and fissure zones were products underthe action of NWW-SEE regional compressional tectonic stress field. The local deviation of thestretching of fault structure reflects the restriction action and influence of the basement structure.(2).In the tectonic stress field, uranium deposits are mostly distributed in the gradient zonewith drastic change in stress value,and at the position of stress“buffer-zone” on the side of some-what lower stress value, In addition, shear stress values tend to decrease gradually from ore de-posits through ore occurrences to anomalous points.Such distribution characteristics of uraniummineralization are basically consistent with the shear stress contour diagram in plan and profile.(3).In the process of tectonic activity, certain degree of uranium migration alsO took place involcanic rock,which was controlled by intensity and distribution of tectonic stress. Driven by tec-tonic stress, uranium travelled in the direction of decreasing stress gradient and towards the posi-tion where stress was considerably released, and took part in the ore-forming process.