西南三江兰坪盆地隐伏岩体探测及其成矿效应

兰坪盆地内发育以金顶、白秧坪为典型代表的MVT型Pb-Zn矿床,其中金顶是我国规模最大的铅锌矿床。现有研究成果中针对区域大规模成矿作用过程、成矿流体形成机制等认识仍存在分歧,特别是对盆地深部是否存在隐伏岩体有较大争议。本文基于区域重磁异常特征与遥感环形构造分析,认为金顶-白秧坪矿集区深部发育中酸性隐伏岩体;通过开展隐伏岩体顶、底埋深,3D展布形态的计算,发现深部岩体空间展布严格受中轴断裂控制,且白秧坪岩体埋藏较深,金顶岩体顶面呈断续凸起的串珠状,具有北浅南深的特点。依据区域构造演化及矿集区成矿时序,推测盆地内部隐伏岩体形成于走滑-应力松弛伸展期,与金顶-白秧坪矿集区主成矿期一致。进一步分析其成矿效应认为,盆地边缘深大断裂与中轴断裂带一起组成的深部岩浆导流体系,促进深部岩浆上侵;上侵岩浆为区域成矿提供主要的热源,直接参与盆地热卤水流体的形成,并促进热卤水运移至浅部断裂与盖层断裂中成矿。

Prognosis and ore-forming effect of concealed metallogenetic pluton in Lanping basin, western Yunnan.

Series of MVT type Pb-Zn deposits typically represented by Jinding deposit and Baiyangping deposit are developed in Lanping basin, and Jinding deposit is the largest Pb-Zn deposit in our country. There still have been different opinions on regional ore-forming process and ore-forming fluid formation mechanism, especially larger debate as to whether there is concealed intrusion at depth of the basin. Based on the analysis on the regional gravity and magnetic anomaly characteristics and the remote sensing ring structure, this article suggests that the concealed acid rock masses are developed in the depth of the Jinding-Baiyangping ore concentration area. And by the calculation of the top and bottom buried depth, 3D distributed shape of the concealed acid rock mass, it's revealed that the space distribution of the deep rock mass is strictly controlled by axial fracture, and Baiyangping rock mass is deeply buried, the top of Jinding rock mass is shaped as beads-strings, with the feature of shallow north and deep south. According to the regional tectonic evolution and the mineralization time sequence of the ore-concentrated area, this article speculate that the concealed rock mass in the basin is formed in the strike slip-stress relaxation and extension period, and is coincident to the main metallogenetic period of the Jinding-Baiyangping ore-concentrated area. From the further analysis of its metallogeny, the hypomagma flow-guide network system is composed by the deep faults at the margin of the basin and the central axial fault zones, and stimulates the hypomagma rising. The raised magma provides the major heat source for the regional mineralization, to directly participate in the formation of the hot brine fluids in the basin and to stimulate its migration; at the same time, the shell faults and superficial faults, which became the direct ore hosting and controlling structure.