北大巴山闹阳坪锌萤石矿区断裂特征与找矿预测

闹阳坪锌萤石矿床位于北大巴山逆冲推覆褶皱带平利隆起东侧,为该区首次发现的受构造裂隙控制的气水–热液型锌萤石矿床。本文从矿区断裂入手,通过对该区矿床地质、断裂特征、矿体特征的研究,总结了该区断裂的演化序列及其对成矿的控制机制与规律。认为NW-SE向断裂组是矿区的主要控矿构造,矿区断裂变形发育演化序列为晚印支–早燕山期形成近EW向断裂F1,早燕山期形成NW-SE向断裂F7和NE-SW向断裂F4,随后的右行走滑作用叠加有张扭性应力,形成有利于成矿热液运移充填成矿的张扭性右行走滑断裂。并明确了成矿期应变椭球体,恢复了成矿期主压应力方向为NNW向(340°~350°)。在此基础上,预测平面上闹阳坪矿区F7与F8断裂之间为下一步找矿重点地段,剖面上K3萤石矿体下伏北东方向可能存在隐伏矿体。

Characteristics of Fracture and Ore-prospecting of Naoyangping Zinc-fluorite Deposit,North Daba Mountain

TheNaoyangping zinc-fluorite deposit is a hydrothermal deposit controlled by fractures. It is located in the north Daba mountain thrust fold belt, at the east side of the Pingli uplift. This paper summarize the evolutionary sequence of ore control fractures and ore-control mechanism. The NW-SE trending faults are the main ore-control structures. The EW trending fractures were produced in Late Indosinian-Early Yanshanian, whereas the NW-SE and NE-SW trending fractures were produced in Early Yanshanian. The transtensional faults resulted from the dextral strike slipping shearing were conducive to the migration of ore fluids and emplacement of the orebodies. We suggest that the strain ellipsoid and restoration of the principal compressive stress direction is NNE (340°–350°) during the period of mineralization. On this basis of the above observations, we conclude that the favorable prospecting target should be located between the F7 and F8 fractures at the surface, and to the northeast of the K3 fluorite ore body at the deep of the Naoyangping mining area.