【摘要】 城口锰矿是成岩作用的产物 ,除叠层石外其它如鲕粒、豆粒、球粒等主要源自碳酸盐台地 ,由合适的海流搬运而来 ,后被原地生长的微生物韵律性包覆而构成稳定的“滩”。Mn2 + 主要来源于下部富含有机质、形成于深水还原环境之泥岩的粒间水 ,其极有利于来自陆地和海底喷发的锰质的富集和保存 ,在成岩作用时受上覆重荷影响使富含 Mn2 + 的酸性粒间水被排驱 ,向压力较小的孔隙度大、渗秀性好的“滩”内转移 ,使“滩”相弱碱性碳酸盐层的Ca2 + 、Mg2 + 被 Mn2 + 交代而成矿更多还原

【Abstract】 Manganese carbonate deposits are situated in Chengkou County, Chongqing.According to their position gained from paleogeographical study they were located in a transitional belt between stable Upper Yangtze carbonate platform and active Qinling Basin during late Sinian. Manganese ore beds occur in the Middle to Upper part of Doushanto Formation of late Sinian.Underlying these ore beds are black carbonaceous mudrocks,in which some structures of gravity slide deposit and contourite can be found locally.Overlying them are dolomicrites.Ore body consists of manganese carbonate and several intercalations in different amounts.Total thickness attains about 1-2.5m. Numerous evidences obtained both from field work and laboratory study indicate that these manganese carbonate deposits are product of diagenetic effects in Chengkou County.Apart from stromatolites,all of other carbonate grains,such as ooids,pisoids,pelletoids and etc.,were transported from carbonate platform by appropriate currents,afterwards they were encrusted rhythmically by microbial organisms in the form of in situ growth,thus forming stable shoal deposits. Mn 2+ elements were originated from lower black mudrocks underlying the ore beds,which are rich in organic materials and were formed in deep-water reductive environments.These Mn 2+ et al.elements might well be concentrated and preserved from sources of both the continents and submarine eruptions.During diagenesis these acidic,intergranular water rich in manganese element was drived by upper overlying loads of sediments and would be migrated into shoal deposits of less pressure,which were of high porosity and permeability.Finally these Ca 2+ ,Mg 2+ elements in less alkaline carbonate beds of shoal facies were to tally replaced by Mn 2+ element,thus forming these manganese carbonate deposits.更多还原