Guangxi Fuzichong The Lead-zinc Ore Field, Hot Water Deposition - Storeyed Transformation Of Mineralization And Prospecting Model,

The Fozichong lead-zinc polymetallic orefield is one of the large-scale deposits in Guangxi Province. In the previous studies, the orefield was regarded either as a group of typical skam or as magmatic hydrothermal deposits.One of the most important discoveries in this study is the regional exhalative sedimentary mineralization along the Bobai-Chenxi faulted zone in early Palaeozoic, based on which, the metallogenic model of diplogenesis is developed for the Fozichong orefield.According to regional data, the Bobai-Chenxi fault zone was a syngenetic system in early Palaeozoic. Activities of the fault zone led to the change of sedimentary facies, and a large number of grativity sedimentation and grativity sliding structures were developed along the slope contolled by the fault zone, with volcanic activities. There are a series of lead-zinc polymetallic deposits, such as Fozichong, Dongtao, Xiashui, Wenlongjing and Jilongding distributed along the fault zone. These deposits have some similiar features: 〢ll of them are bounded in the strata of lower Palaeozoic group; ㎝ain orebodies occur as stratiform or stratoid form with occurrence consistent with that of host strata; ㏒tratiform skam or baritic rock are the direct country rock of orebodies; ㏕ypical syngenetic sedimentary fabric preserved in the ore. These deposits may be included in the same metallogenic series.Fozichong orefield occurs in lower Silurian which is composed of fine clasolite and carbonate. Two kinds of ore have been identified. The first type is characterized by syngenetic sedimentation, which is called as hot-water sedimentary ore. The ore emerges in bedded orebodies which have stable thickness. The ore's mineral component is simple, and its main association of minerals are leucocratic sphalerite-galenite梔iopsite (epidot, chlorite). Leucoratic sphalerite and diopsite are the guide minerals in the ore. There are typical laminated structure,soft sedimentary-slipping deformed structure, syngenetic brecciated structure in the ore which are the mirror of syngenetic sedimentation. The other type of ore has the charactristic of epigenetic mineralization,which is called as telescoped ore. The ore occurs in vein, pocket, lensoid and bedd. The ore minerals are mainly composed of marmatlte, galenit, pyrrhotite(pyrite), chalcopyrite, or marmatite, galenite, pyrite and hedenbergite. Marmatite and hedenbergite are the indicated minerals of the ore. The main ore structure include massive % vein> drusy structure, etc. The second type ore penetrates last type ore in some areas. Therefore, two mineralization periods ore divided, which can be called as hot-water sedimention period and telescoping period.Stratiform green-rock is the direct country rock of bedded orebodies. The rock was called as skam in the past. The green-rock has following features: ㏕he stratiform green-rock's mode of occurrence is conformable with that of the strata, and there are typical syngenetic sedimentary structure in the rock; (2)The stratiform green-rock is constituted mainly by bistagite without zonal distribution around magmatic rocks. The auther regards the stratiform green-rock as a kind of exhalative sedimentary rock which is different from contact-metasomatic skarn.In terms of sulphur isotope result from sphalerite, galenite > pyrite and chalcopyrite, the 8 34S%o value obtained in Fozichong orefield ranges mainly between 0~+5, which is coincident with the average 5 34S%o value of submarine stratabound sulphide deposits in Silurian strate distributed over other areas of the world. The initial sulphur in Fozichong orefield is mostly derived from marine sulfate and strata sediment. The lead isotope compsition of ore suggested that the lead should mainly be derived from old sequence at depth.Carbon and oxygen isotope data show that the carbonatite layer in Fozichong ledge is different from the normal marine sedimentary carbonatite, infering that its formation has relation with hot-water sedimentary activity. Isotope compositions of sulphur, lead, oxygen and carb...