Geochemistry Characteristics And Origin Of Late Carboniferous Dolomites In The Anhui Segment Of The Lower Yangtze Area

Late Carboniferous dolomites was extensively developed in the Anhui segment of theLower Yangtze Area. It was also the main host strata of the ore belt of the Middle andLower Reach of Yangtze River.Research showed that Late Carboniferous dolomites included three rock types, mostlyrystalline dolomites, secondly breccia dolomites and remnant grain dolomites. Thenrystalline dolomites could be divided into powder crystal dolomites, fine grained dolomites,medium-coarse crystalline dolomites and powder crystal dolomites were especially welldeveloped.According to the analysis of trace elements, rare-earth elements, carbon isotopes,oxygen isotopes and fluid inclusions, rystalline dolomites were mostlypenecontemporaneous, some were produced burial dolomitization. dolomites were mostlypenecontemporaneous and burial dolomitization in Huaining area, hydrothermal dolostonesonly existed in replacement dikes and holes of dolomites. breccia dolomites were producedby penecontemporaneous dolomization and mixed water dolomization. remnant graindolomites were produced by burial dolomitization.Dolostone diagenesis of Late Carboniferous in the Anhui segment of the LowerYangtze Area were mainly dolomitization, compaction and pressure solution,dedolomitisation, silicification, dissolution, fracturing, recrystallization and cementation.Among which dolomitization, dissolution, fracturing and recrystallization had constructiveeffects on porosity, compaction and cementation had destructive to porosity.