桂西古岩溶型金矿地质特征

桂西地区自寒武纪至三叠纪发生了多次古侵蚀作用，已大致查明有11次沉积间断时期形成了古岩溶面，其中两次大范围的构造隆升及一次在裂谷拉张期相对持续时间较长的古水下岩溶作用，造成古生界为主的碳酸盐岩系溶蚀尤其强烈，形成大面积的古岩溶面。这些古岩溶面对微细粒浸染型金矿的控制非常明显，部分金矿床虽未直接产于古岩溶面，但其控矿断裂带多与深部古岩溶隐伏带有关系，古岩溶面起到间接控矿作用；主要金矿化的岩性有细碎屑岩、硅质岩、基性及中酸性侵入及喷出岩等，均为硅铝质岩系，而矿化最终底板均为古岩溶面下的碳酸盐岩系。金矿形成机制为：古岩溶潜山构造在后期叠加构造蚀变时，由地层淋滤出的金在古岩溶面及其影响带发生再富集而成矿。

Geological characteristics of paleokarst type gold deposits in western Guangxi

From the Cambrian to Triassic several erosions took place in western Guangxi.I t has been largely as-certained that paleokarst surfaces formed during11sedimentary hiatuses in th e area.Subaqueous karstification that continued for a relatively long period of time during two extensive tectonic uplifts and one rift extension resulted in st rong corrosion of mainly Paleozoic carbonate rock series and formation of extens ive paleokarst surface.These paleokarst surfaces exerted very pronounced control ling effects on finely disseminated gold deposits.Part of gold deposits do not d irectly occur on the paleokarst surfaces,but the ore-controlling faults are most ly related to the hidden paleokarst zones at depths.The paleokarst surfaces have played an indirect role in controlling mineraliza-tion.The main mineralized rocks include fine clastic rocks,siliceous rocks a nd basic and intermediate-acid intru-sive and extrusive rocks,which are all sialic rocks;whereas the ultimate foo twall rocks of the mineralization are all carbonate rocks below the paleokarst s urfaces.The mechanism of gold deposit formation is as follows:when tec-tonism and metamorphism repeatedly occurred on the buried paleokarst hills,g old leached from the strata was concentrated on the paleokarst erosional surface s or their influence belts and thus the ore formed.