断裂构造发育过程与控矿构造形成演化———以邹家山铀矿床为例

热液脉状矿床主要受断裂控制,控制矿脉就位的含矿(赋矿)构造绝大多数是规模比较小的次级断裂或裂隙,而主干断裂普遍被认为是导矿构造或配(运)矿构造,但往往不含矿,甚至没有一点与矿化有关的蚀变痕迹、或成矿流体经过的痕迹。从岩石力学破裂准则看,是最先形成有微孔隙或缺陷存在的微破裂,微破裂逐渐扩展形成小断裂,最后贯通形成主断裂;相关模拟实验也证实存在基底断裂的情况下,盖层破裂的发育过程是最先出现R裂隙、其次是P裂隙、再是D裂隙,最后贯通成具辫状结构的主断裂带。邹家山铀矿床含矿构造是在“X”剪节理基础上发展起来并经持续(递进)变形而形成的“弧形断层面夹透镜状岩块”组合,控制矿带或矿体群的构造是北东东走向、倾向北北西中偏缓倾角、具有左行正断的隐性断裂带。含矿裂隙经历初成、成型和成矿三个阶段演化,成矿后经历邹家山-石洞主断裂贯通和隆升剥露两个阶段演化,最终形成目前的保存状态。

Development process of fault structure and formation and evolution of ore-controlling structure: A case study of the Zoujiashan uranium deposit

Hydrothermal lode deposit is mainly controlled by fault structure. The ore-bearing or ore-hosting structures controlling the emplacement of ore-body and ore vein are often minor second-order faults or fractures, while the major faults are generally considered as passage-ways for ore fluids; however, they usually contain no ore, even no trace of mineralization alteration or evidence of ore fluids passing by. According to the fracture criterion of rock mechanics, a micro fracture with micropores or defects forms first under compression stress, then the micro fracture gradually extends, forming a minor fault, and finally breaks through to form a main fracture. Relevant simulation experiments also confirmed that in the case of basement faults, the development process of caprock fracture can be divided into four stages:R-fracture stage, P-fracture stage, D-fracture stage and through-going stage, finally forming a major fault with braid structure. The ore-bearing structure of the Zoujiashan uranium deposit, developed on the basis of "X" shear joints and formed by continuous (progressive) deformation, is composed of arcuate fault planes with lenticular rocks in between. The ore-belts (or ore body groups) are arranged obliquely, indicating that the ore-controlling structure is a high-degree hidden left-slip normal fault with NEE-trending (50°~65°) and low-middle angle(30°~45°) dipping to northwest. The ore-bearing structure went through initial formation, forming and metallogenic stages, followed by the through-going of the Zoujiashan-Shidong major fractures and uplift and exhumation, and finally formed the current state.