DIAGENETIC ALTERATION OF EARLIER PALAEOZOIC MARINE CARBONATE AND PRESERVATION FOR THE INFORMATION OF SEA WATER
HUANG Si jing 1, SHI He 2, MAO Xiao dong 1,2 , ZHANG Meng 1, SHEN Li cheng 1, WU Wen hui 1 (1.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, China; 2.Yichang Center of China Geological Survey)
Evaluation about the diagenetic alteration of marine carbonate and its preservation for information of sea water has been paid more and more attention to recently and become an important precondition of the research on Palaeo oceanography. Its progress is very important to promotion of the research level in Palaeo oceanography and related other subjects. Based on the test of cathodoluminescence and the analyses of Mn, Sr, Fe and Mg of the marine carbonate samples collected from the sedimentary section of Earlier Palaeozoic in Xiushan of Chongqing, Upper Yangtze Platform, Southwest China, this paper assesses the preservation of different structural components for the information of Earlier Palaeozoic sea water. Micritic limestone, also dolomite, specially fine crystalline dolomite preserve well the information of sea water. Among the factors controlling the alteration of carbonate, apart from the original composition of carbonate mineralogy, the author emphasizes the effect of porosity and the content of terrene clastics of carbonate rocks. The dissolution of aluminosilicate in diagenesis may provide more radiogenic strontium which will show a high content of strontium in carbonate rocks. So the ratio of Mn/Sr should be a better criterion to estimate the alteration of carbonate.