湖南晚二叠世生物礁成岩作用的碳、氧同位素研究

An Application of Carbon and Oxygen Isotopes to Late Permian Reef Diagenesis in Hunan Province

本文通过对湖南晚二叠世生物礁中的有关胶结物及岩石的碳、氧稳定同位素研究,并结合薄片观察、探针成分分析、包裹体测温等,探讨了该地区生物礁成岩作用中的有关成岩特征。研究认为:①湖南晚二叠世生物礁中胶结物从早期至晚期δ^(13)C和δ^(18)O值总体上均有变轻的趋势,反映了礁体为一连续埋藏的成岩过程;②生物礁中所见白云石化现象主要属埋藏压实成因,礁体基本未受早期淡水或混合水影响;③礁中粗晶方解石胶结物形成于深埋期,但湘南和湘西生物礁被深埋的程度却有明显差别。

Based on the study of carbon and oxygen stable isotopes of the related cements and rocks in the Late Permian reef of Hunan Province, and combining the observation of thin sections, electron-probe analysis, and enclave thermometry, the relative diagenetic characteristics of reef dia-genesis in the studied area are discussed. The authors consider that: (1) the C and O stable isotopes values of cements from the early to late stages in the Late Permian reef of Hunan Province tend to become smaller on the whole, suggesting that the reefs have a continuously buried diagenetic history; (2) the dolomitization seen in the reefs mainly results from burial compaction, and the reefs are not influenced by the early fresh or mixed water; (3) the calcite cements of the coarse-giant crystals were formed during the deep-buried period, but there are obvious differences in the degree of deep burial between the southern and the western Hunan reefs.