| 沉积地层中草莓状黄铁矿分析方法及其在古海洋学上的应用 |
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| 引用本文： | 常晓琳,黄元耕,陈中强,侯明才.沉积地层中草莓状黄铁矿分析方法及其在古海洋学上的应用[J].沉积学报,2020,38(1):150-165. |
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| 作者姓名： | 常晓琳 黄元耕 陈中强 侯明才 |
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| 作者单位： | 1.成都理工大学沉积地质研究院，成都 610059 |
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| 基金项目： | 国家自然科学基金项目41902120国家自然科学基金项目41672102地质过程与矿产资源国家重点实验室开放课题GPMR201710 |
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| 摘 要： | 草莓状黄铁矿是黄铁矿的特殊形态，其定义为由相近大小、相似形态的黄铁矿微晶颗粒组成的球形、亚球形聚合体。草莓状黄铁矿粒径分析已广泛应用于各个地质历史时期的古海洋环境恢复研究中，但其形成机理、判别标准与实验方法仍存在分歧。因此对沉积地层中草莓状黄铁矿的形成机理、在古海洋环境恢复中的指示意义及判别标准、实验与数据分析方法等进行总结阐述，有助于理解草莓状黄铁矿的粒径大小与形态对氧化还原条件的指示意义。草莓状黄铁矿在不同氧化还原环境下的形成机理存在差异，其粒径大小、数量以及分布范围可综合反映沉积时水体的氧化还原条件；而草莓状黄铁矿微晶几何形态及整体形貌特征也与古海洋氧化还原环境密切相关。此外，虽然有学者指出该方法可能存在一些问题，但只要在分析过程中结合沉积特征、古生态特征、地球化学指标等多方面证据对环境进行综合判别，甄别特殊条件下沉积的草莓状黄铁矿，则可有效避免这些问题。最后，针对后期氧化作用对草莓状黄铁矿粒径分布的影响进行了评价，结果显示经过后期氧化作用的草莓状黄铁矿粒径变化很小，不会对其在恢复古海洋氧化还原环境的应用上产生影响。
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| 关 键 词： | 草莓状黄铁矿 形成机制 古海洋 氧化还原环境 黄铁矿氧化作用 |
| 收稿时间： | 2019-07-17 |
The Microscopic Analysis of Pyrite Framboids and Application in Paleo-oceanography |
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| Institution: | 1.Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China2.State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China3.State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China4.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China |
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| Abstract: | Pyrite framboids are defined as microscopic spheroidal to sub-spheroidal clusters of equidimensional and equimorphic pyrite microcrystals. The size distribution of pyrite framboids has been widely used as a promising tool for reconstructing the redox conditions of geological periods. Summarizing the formation mechanism, paleo-oceanographic implications, discrimination standard, and experimental methods using pyrite framboids might help to understand why they play such an important role. The formation mechanism of pyrite framboids differs in oxic and euxinic conditions. Their size, abundance and distribution range are all important proxies in inferring the oxygen levels of the water column. The microcrystal geometries and morphological characteristics are closely related to the redox condition of the paleo-ocean in the deposition process. Furthermore, although one or two unknown problems may yet be present in the method, their potential effect may be offset by using additional effective methods (e.g., sedimentary microfacies analysis, paleocommunity reconstruction, and specific geochemical indices) to analyze the redox condition and to recognize unusual settings. The validity of the oxidized pyrite framboid in reconstructing the redox conditions of paleo-ocean has been evaluated. The results show that the oxidation of pyrite has little effect on redox interpretations based on pyrite framboid distributions. |
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