早古生代海相碳酸盐的成岩蚀变性及其对海水信息的保存性

有关海相碳酸盐对海水信息保存性的评估研究近年来得到了越来越多的重视，已成为古海洋学研究一个不可缺少的重要前提，其发展对古海洋学及其他相关学科研究水平的提高至关重要，通过对重庆市秀山剖面早古生代海相碳酸盐的阴极发光性和Mn,Sr,Fe,Mg等元素分析，评估了早古生代层中各种碳酸盐结构组分对海水信息的保存信息的保存性及主要控制因素。除细结构的微晶方解石和腕足类壳对海水信息保存较好以外，白云石，尤其是微－粉晶白云石对海水信息的可保存性也得到肯定，在控制碳酸盐矿物成岩蚀变性的因素中，除要注意其原始矿物是否具有较高的抗成岩蚀变能力外，同时要注意岩石原生孔隙度和岩石中陆源碎屑含量对碳酸盐岩蚀变的影响，作者还强调了成岩过程中由长石等铝硅酸溶解提供壳源Sr所造成的碳酸盐矿物成岩蚀变可能表现为较高的Sr含量，这是将Sr含量作为评估方法时需要注意的，在不进行^87Sr/^86Sr测定的前提下，Mn/Sr比值可弥补这方面的不足。

DIAGENETIC ALTERATION OF EARLIER PALAEOZOIC MARINE CARBONATE AND PRESERVATION FOR THE INFORMATION OF SEA WATER

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.