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Tidal-flat and shoal deposits of carbonate facies in the Qiziqiao Formation are widely distri-buted over the vast areas of Guangxi,Guangdong and Hunan provinces,constituting an impor-tant stratigraphic unit where strata-bound and stratiform ore deposits (galena-sphalerite-pyrite)are found.These types of ore deposit seem to have close relations to the tidal deposits.Recog-nition of tidal deposits is based upon rock fabric,texture,structure,fossil assemblage,and par-ticular sedimentary cycle.The typical sequence of tidal-flat deposits consists mainly of threeunits:Amphipora limestone,laminated limestone and dolostone (from the bottom to the top).This sequence represents a complete process of sedimentation from low-tideflat through inter-tidal to high-tideflat or supratidal.The sequence of shoal deposits of carbonate facies consistschiefly of grainstone and algal osparite.Two major types of tidal deposit (open and restricted marine facies) can be distinguished,with eleven microfacies as follows:1)calcarenite (grainstone) with sparite (MF-1);2)algalosparite (MF-2);3)oncolite (alga-,or stromatoporoid-encrusted grains) (MF-3);4)bioclas-tic grainstone (biosparite) or rudstone with sparite (MF-4);5)Amphipora limestone (MF-5);6)dark fossil-poor micrite (MF-6);7)pelsparite or peloidal grainstone with sparite (MF-7);8)laminated pellet mudstone-wackstone (MF-8);9)micrite with onkoids (MF-9);10)rud-stone or floatstone (MF-10;and 11) bedded dolomite-gypsum-dolomite (MF-11).
Tidal-flat and shoal deposits of carbonate facies in the Qiziqiao Formation are widely distri-buted over the vast areas of Guangxi, Guangdong and Hunan provinces, constitute an impor- tant stratigraphic unit where strata-bound and stratiform ore deposits (galena-sphalerite- pyrite) are found. These types of ore deposits seem to have close relations to the tidal depositss.Recog-nition of tidal deposits is based upon rock fabric, texture, structure, fossil assemblage, and par-ticular sedimentary cycle.The typical sequence of tidal-flat deposits consists mainly of threeunits: Amphipora limestone, laminated limestone and dolostone (from the bottom to the top). This sequence represents a complete process of sedimentation from low-tideflat through inter-tidal to high-tideflat or supratidal.The sequence of shoal deposits of carbonate facies consists of grafly of grainstone and algal osparite.Two major types of tidal deposit (open and restricted marine facies) can be distinguished, with eleven microfacies as f 2) algalosparite (MF-2); 3) oncolite (alga-, or stromatoporoid-encrusted grains) (MF-3); 4) bioclas- tic grainstone 5) Amphipora limestone (MF-5); 6) dark fossil-poor micrite (MF-6); 7) pelsparite or peloidal grainstone with sparite (MF-7) 9) micrite with onkoids (MF-9); 10) rud-stone or floatstone (MF-10; and 11) bedded dolomite-gypsum-dolomite .