大坪金矿床主矿体控矿构造与矿化富集规律

大坪金矿床位于哀牢山金矿带南部,为研究其规模最大的V1-2-3号矿体的控矿构造和矿化富集规律,本文研究总结了矿体地质特征,对矿体的多级控矿构造及力学性质进行剖析,采用矿体垂直纵投影图对厚度、品位及其剩余值、趋势值等值线图进行分析。研究结果表明:金矿主要受三级断裂构造控制:红河-哀牢山深大断裂控制整个金矿成矿带;小新街断裂为导矿构造;小新街断裂的次级断裂带为容矿构造。在构造应力机制发生转换的大规模成矿时期,矿区受到由顺时针旋转变为逆时针旋转的构造应力场作用,控矿断裂性质由左行压扭性转变为张性。构造应力场严格控制了矿体的空间位置、规模、形态、矿体厚度与品位变化特征。成矿流体运移方向为北西-南东方向,在多期、多阶段成矿作用下,形成层状分布矿化富集带。研究厘定了V1-2-3号矿体共有3个矿化富集带,包括7个矿化富集中心,其侧伏方向为北西-南东方向。矿化富集中心大多形成于构造引张的部位,形成透镜状富厚矿体;在构造闭合的地方,矿脉变薄、品位降低,形成贫化带或无矿段。

Ore-controlling structure and mineralization rules of main auriferous quartz veins in the Daping gold deposit: An example of the Ailao Shan metallogenic belt in Yunnan Province, China

The Daping gold deposit, with the largest auriferous quartz vein No. V1-2-3, is located in the south of the Ailao Shan gold metallogenic belt. In order to study ore-controlling structure and mineralization regularity of this vein, this paper summarizes the geological characteristics of the deposit and analyzes the multiple-order ore-controlling structure and its mechanical nature based on contours of thickness, grade and residuals and tends projected on longitudinal profiles. The results show that the Daping gold deposit is mainly controlled by faults of three orders, including the Ailao Shan-Red River (ASRR) fault which controls the whole gold deposits in the Ailao Shan metallogenic belt, Xiaoxinjie fault as the leading structure, and its secondary faults which serve as the transfer and deposition structures during mineralization. The direction of tectonic stress field changed from clockwise rotation to counter-clockwise rotation during metallization, making the ore-controlling faults change from left-lateral strike-slip to tensional structure. The structural dynamic mechanism of the Daping gold deposit had great impact on the distribution, scale, shape as well as variation of thickness and grade of V1-2-3. The transfer direction of ore-forming fluid was NW-SE, which formed three enrichment zones with multi-stage mineralization. Quartz vein V1-2-3 contains three enrichment zones of mineralization according to this study, whose direction of lateral-trending is NW-SE, and they include seven enrichment centers, usually being lenticular bonanza, mostly formed in the tensile stress zone. At the localities of structural closure, auriferous quartz veins have been thinned with lowered grades, forming lean lodes or dead sections.