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沉积物源判别的地球化学方法
王轲
中国海洋大学
摘要:
本文对沉积物源判别的地球化学方法进行了分类总结,并分析了各类方法中存在的问题,进一步给出了应用建议,以期更加实用。综合分析表明,常量元素(组分)主要用于表征化学风化程度和判断源岩类型;微量元素组成不仅可以示踪物源区,还可以判别构造环境,其中蛛网图和三角图是最有效的判别图解,Ce异常是判断古海洋氧化还原环境的常用指标,Eu异常常用于区分基性岩和热液流体与酸性岩和陆源物质;直接指示物源的同位素指标以Sr、Nd、Pb同位素组成及其特征值最为有效,不仅可用于追踪沉积物源,还可用于确定沉积物的年龄、划分沉积地层和反映区域性或全球性的地质事件。古气候变化是影响生物碎屑碳酸盐中C、O同位素组成变化的重要因素,而古气候直接影响物源供给。因此,生物碎屑碳酸盐中C、O同位素组成可以间接反映物源供给情况。此外,石英δ18O值对于河流沉积物、沙漠、黄土和风尘等沉积物的物源分析以及陆海源汇效应的研究具有重要意义。在利用地球化学方法进行物源分析时,运用单一方法往往存在一定的局限性,应当充分利用各类方法的优势,考虑各种造成误判的因素,利用多种方法综合分析,必要时还应考虑沉积环境的其他要素。
关键词:  沉积物源判断  地球化学方法  构造背景  古气候  沉积环境
DOI:10.11759/hykx20191115001
分类号:
基金项目:
Geochemical methods for identification of sediment provenance
wang ke
Ocean university of China
Abstract:
Compared with petrological and mineralogical methods, geochemical methods for identifying sediment sources are more accurate and widely applicable. In this paper, the geochemical methods of sediment source identification are classified and summarized. In order to make the method more practical, the problems in various methods are pointed out and the application suggestions are given.The comprehensive analysis shows that the major elements (components) are mainly used to characterize the degree of chemical weathering and judge the type of source rock.Trace elements can not only trace the provenance, but also distinguish the tectonic environment.Ce anomaly is a common index to judge the paleo-oceanic REDOX environment, while Eu anomaly is often used to distinguish basic rocks and hydrothermal fluids from acidic rocks and terrestrial sources.Sr, Nd and Pb isotope are the most effective isotopic indicators that can be used not only to track sediment sources, but also to determine the age of sediments, divide sedimentary strata and reflect regional or global geological events.Paleoclimate change is an important factor affecting the change of δ13C and δ18O in bioclastic carbonate and paleoclimate directly affects the material supply. Therefore, δ13C and δ18O in bioclastic carbonate can indirectly reflect the provenance.In addition, the quartz δ18O value is of great significance for the provenance analysis of river sediments, deserts, loess and dust, as well as the study of land-sea source and sink effects.When geochemistry methods are used for provenance analysis, single method often has some limitations. It is effective to make full use of the advantages of various methods, take into account various factors causing misjudgment, make comprehensive analysis with various methods, and take other elements of sedimentary environment into consideration when necessary.
Key words:  Determination of sediment provenance  Geochemical methods  Tectonic setting  Paleoclimate  Sedimentary environment
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