沉积相稀土地球化学标志

REE Geochemical Characteristics of Sedimentary Facies

摘要: 沉积相研究是沉积矿床研究的基础，本文系统研究了各种沉积相的稀土元素地球化学特征，探讨了表生环境下稀土元素演化规律。根据大洋铁锰结核与大石桥菱镁矿碳酸盐岩、智利与冲绳海沟沉积物、麻阳中生代陆相沉积岩及潮坪相磷块岩等沉积相稀土元素分配特征分析，发现不同沉积相稀土分配特征不同，尤其是不同沉积物源及沉积相岩石的LRE/HRE-ΣREE、δEu-LRE/HRE相关性不同。本文第一次把沉积相物质来源和沉积环境结合进行分类，分为海源海相、陆源陆相、陆源海相及海陆过渡相四种沉积相。海源海相沉积物以大洋铁锰结核与大石桥镁质碳酸盐岩为代表，铁锰结核的LRE/HRE-ΣREE、δCe-LRE/ HRE正相关，δEu-LRE/HRE负相关，而镁质碳酸盐岩的LRE/HRE-ΣREE、δCe-LRE/HRE、δEu-LRE/HRE均为正相关，两者的差异反映了氧化还原条件的差异。陆源陆相沉积物以麻阳中生代沉积岩为代表，LRE/HRE-ΣREE负相关，δEu-LRE/HRE正相关。陆源海相沉积物以海沟碎屑沉积物为特征，碎屑物以陆缘为主，海源物质形成胶结物，LRE/HRE-ΣREE、δEu-LRE/HRE都呈曲线相关型式。海陆过渡相以磷块岩为代表具有海陆物质混合的特点，钙磷质属于海源物质，而碎屑物属于陆源物质，LRE/HRE-ΣREE、δEu-LRE/HRE都表现为曲线相关型式。岩石中Zr/Y比值影响LRE/HRE-ΣREE、δEu-LRE/HRE的相关性，因此LRE/HRE-ΣREE、δEu-LRE/HRE的相关演化特征及其稀土配分模式可以作为判别沉积相的重要标志。

Abstract: Sedimentary facies study is a base of research on sedimentary deposits. In this paper, a systematic study is carried out on REE geochemical characteristics of different sedimentary facies, followed by the exploration about evolution of REE in supergene environment. Based on the analysis of the REE distribution patterns about Chile trench sediments, Mesozoic continental sedimentary rocks in Mayang and tidal-flat phosphorite, a regular pattern is summarized that REE distribution features vary among different sedimentary facies. More specifically, the correlations of LRE/HRE- ΣREE and δEu-LRE/HRE are significantly different among the rocks of different sedimentary source and sedimentary facies. Marine sea sediments show a positive correlation in LRE/HRE-ΣREE diagram and a negative correlation in δEu-LRE/HRE diagram, while for the terrigenous continental sediments, the conditions are just the opposite. Furthermore, marine mixed-source sediments display a curvilinear correlation in LRE/HRE-REE and δEu-LRE/HRE diagrams. As Zr/Y ratios have some influence on the correlations of LRE/HRE-REE and δEu-LRE/HRE, the correlations and REE patterns can be used to distinguish different sedimentary facies.