【摘要】 湖北宜昌地区下奥陶统以碳酸盐岩沉积为主,成岩作用主要有胶结、压实、泥晶化、新生变形、硅化、溶解和白云石化作用,以胶结作用和白云石化作用最为广泛。成岩环境为淡水渗流带、淡水潜流带、淡水-海水混合带、海水潜流带与埋藏带。大多数成岩变化发生于淡水潜流带和混合带。更多还原

【Abstract】 The sequence of the Lower Ordovician in Yichang, Hubei is dominated by carbon-ates. The carbonates consist of allochems, such as bioclast, intraclast, pellet and ooid,abundant micrite and dolomite. The petrological characters indicate that the sequence wasdeposited in the carbonate platform--epeiric sea. The Lower part of the sequence mainlydeveloped in shallow areas of higher energy, while the upper part in shallow shelf areas oflower energy, indicating the process of transgression. According to the conventional and cathodoluminescent petrography and stuble iso-topes of carbon and oxygen, diagenesis, which includes the cementation, compaction, mi-critizatiom, neomorphism, silicification, dissolution and dolomitization, has been identified.The cementation and dolomitization are most common. The equant cement contains lighter δ¹⁸O than most marine cements, indicating itsmeteoric phreatic origin. Its δ¹³C is heavier than δ¹³C of most marine cements through theinfluence of original components in the rocks. The δ¹⁸O and δ¹³C values of most micritesare within the range of marine calcites, suggesting that they formed in marine phreatic en-vironments. The dolomites are mostly euhedral with partly subhedral and enriched relativeto calcites in ¹⁸O and ¹³C. The dolomitization occurred in the mixing environment. Both equant cements and dolomites have mostly bright cathodoluminescence andsometimes may contain interlayers of dull luminescence. The bright luminescence is thecharacteristic of slightly reducing environments. The dull luminescent interlayers mayhave developed in temporal oxidizing conditions. A large proportion of the diagenesis can be ascribed to the early diagenesis.更多还原