Sedimentary Facies And Sequence Stratigraphic Analysis In Manganese-containing Falang Formation, Southeast Yunnan

Our country,China,is short of manganese ore resource extremely.Manganese ore is a important strategy mineral resource,and the high-quality manganese ore have been entered in a list of badly needed mineral resource.The southeast of Yunnan is the area where output high-quality manganese ore . The distribution of the verified manganese ore beds and manganese ore points along Jianshui-Kaiyuan-Wenshan.the manganese is depoisited of Ladinian Falang Formation(T2f) of the Middle Triassic. the underlie bedding is Gejiu Formation(T2g) .in Dounan and Jianshui,there is a cessation of deposition surface between T2f and T2g . T2f have two beddings contain manganese,placed in middle of T2f and top of it. few of place,such as Wenshan Laowu,only have the top of manganese bedding in T2f and Dounan Yanzijiao has the lower section of manganese layer.In these manganese-containing beddings areas,the lithologic character and quality of manganese ores are different because of the depositional environments are different.The first and second manganese-containing beddings depositional environment of Jianshui Baixian manganese bed both are tidal flat facies.The frist manganese-containing beddings has manganese-containing limestone and thin manganese layer.The second of it has thin layer marl,inside of it is the manganese-containing mudstone;InYanshan Dounan manganese ore ,the first manganese-containing bedding's sedimentary facies is tidal flat facies,It's Lithologic character is siltstone, argillaceous siltstone and manganese-containing siltstone;the second one is continental platform facies, argillaceous siltstone,siltstone, arene dolomitic limestone, intraclast limestone, manganese-containing limestone contain manganese.In Southeast Yunnan, Ladinic period,Nanpanjiang basin has been encircled in three circum continental environment :offshore—epeiric sea, northwest of it is Kangdian diastrophic block,southwest of it is Ailaoshan uplift zone;sourh of it is Yunbei diastrophic block,is a relative closed bay.Middle of Triassic,the water from sea inter Nanpanjiang basin,and deposit in it.The water is becomed to more deep and boundary of sea is also becomed to bigger.from west to east.The facies in southest of Yunnan from west to east is:estricted platform—open marine platform—aulacogen—lagoon after beach—reef (beach)—beach(reef)—platfom boundary clinothem—basin—basin plain—deep sea basin.Baixian restricted platform,Dounan platfom boundary clinothem ,Tangdian-Zhuyuan aulacogen and Yanshan Dounan continental platform.In Southeast Yunnan,we can see three triple in T2f sequences,their division surfaces are I type sequence surface.SQ1 is only in Dounan Mengzi and Yangqigou area.In Dounan continental platform,the base of TST has exposed erosion bedding and appeared brecciola what is standed for low water level wedge.SQ2 is only appeared in middle and supreme Ladinic stage,is the most important sequence what contain manganese.Dounan,Baixian and other area has high-quality manganese bed.SQ3 in top of T2f ,Yanshan Dounan is developed continental platform. Manganese-containing argillaceous siltstone in this sequence.In Yanshan Donnan and Jianshui manganese ore,we can see that only in triple sequence's TST can be founded manganese-containing bedding in southeast of Yunnan..