哀牢山老王寨金矿田构造问题探讨

ON STRUCTURE OF LAOWANGZHAI COLD OREFIELD IN MT.AILAO

哀牢山老王寨金矿产于变质的晚古生代岩石中,是由浅变质的砂板岩、杂砂岩以及海相火山岩所组成。区内岩浆活动强烈,断裂发育。区内存在具挤压逆冲性质的东西向断裂带和显示塑性—脆性剪切带特征的NW-SE向断裂带,它们是主要的控矿构造。此外,有少量规模不大的NE-SW向断层,可切割上述断裂和矿体。根据对共轭节理测定、岩组分析和岩石有限应力分析等,本文对构造应力场作了划分:早期(成矿前)构造应力场发生于海西-印支运动期间;晚期(成矿期)构造应力场发生于燕山期,并可进一步划分早晚两个阶段。成矿主要受断裂控制,构造活动引起岩石蚀变,多次构造活动导致多次蚀变矿化。成矿时代为燕山晚期至喜山早期。

The Laowangzhai gold ore of Mt. Ailao occurs in the metamorphosed late Paleozoic rocks consisting of the epizonal sandy slate, graywacke and volcanic rock of marine facies. Strong magmatic activities and wide-spread faults are found in this area. There are compression-thrust fault zones striking E-W and NW-SE fault zones showing the features of brittle-plastic ductile zone in this area. They are the major ore-controlling structures. In addition, a few small-scale faults striking NE-SW may cut the said faults and ore bodies. Based on the measurements of conjugate joints, analyses of petrofabic and rock restricted stress, the tectonic stress field since the late Paleozoic has been discussed by this paper. It can be divided approximately into two periods, i.e. the early one(premineral)occurred in the Hercynia-Indosinian movement and the late one(metallogenic period)happened in Yenshan period, the latter is further divisible into two stages of early and late. The metallizations are largely controlled by faults. The rock alterations were caused by structure action; polyphasic alterations and metallizations were formed by polyphasic structure activities. The metallogenic epoch is considered to be from late Yenshan to Himalayan in age. Finally, this paper summarizes in brief the ore-forming structural guides and probes how the ore-search prospect is enlarged and the concealed ore deposits are pridicted.