庞西垌银矿区控矿断裂地质特征及其形成演化

位于粤桂边界的庞西垌银矿床是粤西北地区蚀变构造岩型银金多金属矿床的典型代表之一.在区域应力场分析的基础上,通过对庞西垌矿区控矿断裂构造岩、断裂分带以及伴生节理构造的研究,对庞西垌银矿区控矿断裂构造的形成和演化过程进行了探讨.所得结论为:①矿区控矿断裂构造形成演化受区域构造应力场影响和控制,与区域构造应力场相对应,矿区控矿断裂构造经历了海西-印支期压性、燕山早期压扭性、燕山晚期张扭性3种不同构造应力场的叠加改造,不同特征的构造岩在空间上叠加产出.②矿区控矿断裂构造活动具有继承性特点,表现为晚期断裂活动沿早期断裂形成的构造面进行,不同阶段构造活动的中心基本一致.比较而言,晚期断裂构造活动强烈,影响范围大,对早期构造岩具有强烈改造作用.③构造透镜体形态及运动学标志指示矿区控矿断裂构造早期表现为左行平移-逆冲运动,晚期表现为右行平移-滑覆运动.

Geological Characteristics and Discussion on Formation and Evolution of Ore-Controlling Fault in Pangxidong Silver Ore Field

Pangxidong silver deposit,located at the boundary between Guangdong and Guangxi,is a typical representative of Ag-Au polymetallic deposits in the northwest of Guangdong,which occurs in altered tectonites.The paper discusses the ore-controlling fault's formation and evolution process in Pangxidong silver field on the basis of the regional stress analysis and the study of the ore-controlling fault tectonites,fault zoning and the associated joint structure.It is concluded that(1) The forming and evolution of fault in this ore field was influenced and controlled by the regional structural stress field,corresponding to which,ore-controlling fault went through the superposition transformation of three different tectonic stress fields,namely press in Hercynian-Iddosinian period,compress-shear in early Yanshan period and tenso-shear in late Yansian period,and tectonites of different characteristics occur superposedly in space;(2)The ore-controlling fault activity has inherited attribute,with the later fault activity occurring along the early fault plane and the centre of activity in different stages basically the same.Comparatively,the later fault tectonic activity is more intense than the early and has larger influence sphere and impacted strongly on the early fault activity;and(3) Structural lens shape and kinematics signs indicate that the early fault movement was of sinistral shear with thrust,and the later,dextral shear with oblique down-slip.