桐柏山老湾金矿带右行走滑断裂控矿体系的构建及其意义

Establishment and Significance of Dextral Strike-slip Fault Ore-controlling System of the Laowan Gold Belt,Tongbai Mountains

以老湾金矿带上上河-彭家老庄、老湾-盛老庄金矿床为研究对象，通过野外地表和坑道观察，进行断裂产状统计、配套分析及构造性质与矿化类型耦合关系的研究，确立了老湾金矿带控矿构造体系性质及组合型式。上上河-彭家老庄金矿床以石英脉型矿化较为发育为特点，控矿断裂属走滑构造体系中的R型张扭性裂隙带，向北陡倾，走向（290°～310°）与主剪切带方向（286°）交角约为15°，具右行剪切特征，滑距约10 m。老湾-盛老庄矿床以蚀变岩型矿化为特征，充填脉型矿化不发育，其金矿控矿断裂属 P 型压扭性裂隙，向南缓倾，其总体走向近东西（约92°），与主剪切带方向的另一端交角约15°。3条规模较大的断裂蚀变带平面上右型侧列特点反映其滑移方向与上上河-彭家老庄控矿断裂滑移方向一致。综合整个矿带断裂产状及矿化信息，认为老湾金矿带控矿构造总体为以老湾和松扒断裂为边界断裂，由里德尔剪切体系中的P型和R型剪切带连结形成的辫状右行走滑剪切带。结合桐柏造山带区域地质演化历史，分析认为该脆性断裂构造带是早期韧性剪切带继承性演化的结果，反映桐柏造山带不同构造块体间斜向碰撞及随后地壳抬升作用的动力学演化过程。老湾金矿带右行走滑构造体系与成矿作用的耦合关系对矿床成因提供重要地质约束。

Focusing on the Shang Shanghe-Peng Jialaozhuang and Laowan-Sheng Laozhuang gold deposits of the Laowan gold metallogenic belt, Tongbai Mountains, the authors investigated the structural nature and assembly patterns of ore-controlling structural zone of the Laowan gold belt based on field investigation, mine channel observation, statistical analysis of fault attitude and assorting, and discussed the coupling between property of fault and mineralization type. The Shang Shanghe-Peng Jialaozhuang gold deposit has well-developed quartz vein type-mineralization, and its ore-controlling faults are characterized by R-type tension-shear fracture of Reidel shear structure, steep dipping northward, trending 290°～310° which strike at an angle of about ＋15° to the principal shear zone （286°）, 10 m of displacement by dextral strike-slip. The Laowan-Sheng Laozhuang gold deposit has altered rock type mineralization without quartz vein. Its ore-controlling faults are characterized by P-type compression-shear fracture of Reidel shear structure, gently dipping southward, trending about 92°, which strike at an angle of about 15° to the principal shear zone （286°）, and dextral strike-slip is reflected by the right echelon arrangement of its three large fracture alteration belts. Integrating the information of faults and mineralization of the whole gold belt, we concluded that the ore-controlling fault system of gold belt is a braided dextral strike-slip shear zone by linkages between R and P shears of Reidel shear zone bounded by the Laowan and Songpa faults. Combined with the regional geological evolution of the Tongbai orogenic belt, it is proposed that the brittle shear zone of the Laowan gold belt was as a consequence of further development of early ductile shear zone, reflecting the dynamic mechanism of oblique collision between different tectonic blocks followed by uplift of the Tongbai orogenic belt. The coupling relationship between the dextral strike-slip fault ore-controlling system of the Laowan gold belt and gold mineralization provides important geological constraint on genesis of gold deposit.