大坪金矿构造矿体空间分布特征与构造控矿规律

大坪金矿是哀牢山造山型金矿的典型代表。矿床明显受到了红河—哀牢山断裂、小新街断裂以及小新街断裂的次级断裂的控制。研究断裂构造与矿体的空间分布特征以及新生代(58 Ma)以来研究区内发生的多次构造动力机制的转变对成矿的影响具有重要的理论价值和找矿意义。新生代以来,印度板块与欧亚板块发生汇聚碰撞,形成NW向的三级断裂构造系统;汇聚过程中,印度板块发生四次旋转方向的转变引发区内构造动力机制的四次转换,构造动力机制的转换与哀牢山造山带的大规模成矿作用具有重要关系,成矿物质主要来源于下地壳或上地幔,受壳—幔相互作用影响。红河—哀牢山断裂控制了区内造山型金矿的分布,小新街断裂是大坪金矿的导矿构造,次级断裂带构成了大坪金矿的容矿构造,断裂带中构造应力引张部位为金矿的矿化富集带。研究成果为大坪金矿成矿机制研究和深部找矿预测提供了重要的依据,对区内其他造山型金矿的研究也具有重要的参考意义。

Spatial distribution of faults and structural ore-control regularity in the Daping gold deposit, Yunan Province

Abstract: The Daping gold deposit is a typical orogenic gold deposit in the Ailao Shan-Red River (ASRR) metamorphic belt. Auriferous veins are controlled by ASRR fault, Xiaoxinjie fault and its secondary faults. In this study, the authors analyzed regional structures and distribution of auriferous veins in the ASRR metamorphic belt during several times of changes of structural dynamic mechanism which have had great influence on the mineralization of the Daping gold deposit since 58 Ma. The results achieved by the authors are valuable for theoretical research and gold exploration. There are three grades of northwest structural faults in the ASRR belt which resulted from convergence between India and Eurasia that led to four times of changes of regional structural dynamic mechanism due to the four times of change of the convergence direction since 58 Ma. Intense mineralization in ASRR orogenic belt had close relationship with changes of structural dynamic mechanism, and the metallogenic substance mainly came from the lower crustal layers and the upper mantle. The left- and right-lateral shears were responsible for the formation of gold deposits in the ASRR orogenic belt. The ASRR fault corresponds to the distribution of the ASRR gold belt, whereas the Xiaoxinjie fault and its secondary faults serve as the mineral transfer and mineral deposition structure. It is also demonstrated that extensive part of the secondary fracture in auriferous veins formed by tensile stress indicates the deposition of bonanza. This study plays an important role in the metallogenic mechanism research and the exploration prediction of the Daping gold deposit and is also useful for the study of other orogenic gold deposits along the ASRR orogenic belt.