华南志留系红层粘土矿物与铁氧化物矿物学特征及其沉积环境指示意义

The Silurian red beds has been intensively studied in geological fields, such as lithostratigraphyd and biostratigraphy. However, the mineralogy of the Silurian red beds in South China have not yet been investigated in detail. We planned to collecte Sedimentary Rocks from the "upper red beds" Huixingshao Formation, and to show characteristics and quantitative pattern of iron (oxyhdr)oxide mineral and clay minerals using X-ray diffraction (XRD), diffuse reflectance spectrophotometry (DRS), scanning electron microscopy (SEM), chemical analyses and so on. In this study, we used the high-resolution transmission electron microscopy (HRTEM) to identify the forms of hematite and other iron oxides, and to thus interpret the origin of the red colour in the Telychian red beds. Sediment provenance, diagenetie history and diagnetie environments of The Telychian red beds will be discussed according to detrital and/or authigenic clay minerals like chlorite, illite. We specifically address the study of mineralogy of the Huixingshao Formation compared with the Rongxi Formation in the Upper Yangtze Region and Tangjiawu Formation in lower Yangtze region. The goal of this project is to understand the different factors that control the red beds genesis. The results of this study will contribute to understanding of the origin of red beds, sediment sources of the red beds, and the palaeoclimatology during the Silurian period.

红层在志留纪研究中被众多国内外学者所关注，在华南志留系浅海相红层古生物、古地理研究取得许多重要进展时，其矿物学的研究工作还极少有人涉及。本项目通过选取华南志留系红层中有代表性的"上红层" 迴星哨组作为研究对象，在对野外地层进行详细勘察的基础上，运用现代矿物学研究手段如：X射线、光谱学、电子显微等技术，并结合地球化学分析，重点开展红层（含红色和非红色地层）铁氧化物、粘土矿物特征和定量解析研究；探讨红层的沉积成岩作用和物源特征，反演沉积环境，阐明红层Fe元素赋存状态、来源和致色铁氧化物的形成机理；在此基础上，进一步与"下红层"溶溪组和浙西唐家坞组地层的矿物学特征进行对比，综合分析红层在志留纪古环境演变过程中的响应机制；本研究拟为解释华南志留纪红层的成因机制，进而探索当时的古环境、古气候等方面的问题提出新的证据和认识。

本项目通过对上扬子张家界地区志留系红层中有代表性的"上红层" 迴星哨组的研究，并与重庆秀山地区同时代红层的对比，在对野外地层进行详细勘察的基础上，运用现代矿物学和地球化学手段方法，进行了红层沉积岩的岩石薄片光学观察、X射线衍射分析、漫反射光谱学、电子显微等技术、岩石磁学，并结合元素和同位素地球化学分析，重点开展了红层（含红色和非红色地层）铁氧化物、粘土矿物特征和其组成的元素关系的研究，研究发现赤铁矿是导致红层成色的主要矿物，用同位素方法进行了物源的讨论。在此基础上，进一步与江苏沿海现代滨浅海沉积物进行了对比研究，分析了不同物源对现代浅海沉积物赤铁矿和针铁矿的贡献情况，探讨了气候对沉积物中针铁矿和赤铁矿的控制因素。本项目的成果为解释华南志留纪红层的成因机制和沉积环境提供了有益参考。