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| 新近纪深海大洋红层的分布分类及成因 |
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熊梓翔1,2, 朱俊江1,2, 杨国明1,2, 王长盛1,2, 贾仲佳1,2, 欧小林1,2, 李三忠1,2
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1.深海圈层与地球系统前沿科学中心, 海底科学与探测技术教育部重点实验室, 中国海洋大学 海洋高等研究院和海洋地球科学学院, 山东 青岛 266100;2.青岛海洋科学与技术国家实验室 海洋矿产资源评价与探测技术功能实验室, 山东 青岛 266100
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| 摘要: |
| 新近纪大洋红层是一种在氧化条件下形成的红色-粉色-棕色海洋沉积物。白垩纪大洋红层研究成果众多，然而新近纪大洋红层研究缺乏系统的分析和总结。本文以新近纪大洋红层为研究对象，通过对全球大洋钻探井位资料的分析，发现39个钻井含有新近纪大洋红层。通过对不同大洋区域、不同钻井内93个红层离散样品的主量元素CaO，Al2O3和SiO2含量进行三元图投点分析，将新近纪大洋红层分为铝质和钙质大洋红层，其中绝大多数为铝质大洋红层。进一步分析了部分钻井中离散样品的磁化率变化、反射光谱一阶导数曲线、热退磁曲线和交变磁场退磁曲线变化，结果表明新近纪大洋红层的致色矿物以赤铁矿为主。12个钻井中新近纪大洋红层离散样品的低总有机碳含量和低CaCO3含量指示较低的生物生产力，此外19个钻井中红层的沉积速率平均为4 mm/ka，而非红层的沉积速率平均为85.3 mm/ka，指示红层的沉积速率相对较低。总结和分析新近纪大洋红层的以上特征，本文认为较低的有机质堆积速率为铁氧化物（赤铁矿）的形成提供了有利的氧化条件，使得沉积物中的铁氧化物在成岩阶段得以保存，最终形成全球分布的新近纪大洋红层。 |
| 关键词: 大洋红层 新近纪 赤铁矿 物理属性 全球分布 |
| DOI：10.11759/hykx20201017002 |
| 分类号:P736 |
| 基金项目:山东省自然科学基金面上项目（ZR2019MD036号）；青岛海洋科学与技术试点国家实验室海洋矿产资源评价与探测技术功能实验室自主课题资助项目（MMRZZ201802号）；国家自然科学基金重点项目（91958214；41831280）；中国海洋大学研究生教育质量提升联合培养基地项目（HDYJ18011）；中央高校基本科研业务费专项（202172002） |
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| Distribution, classification, and origin of Neogene deep oceanic red beds |
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XIONG Zi-xiang1,2, ZHU Jun-jiang1,2, YANG Guo-ming1,2, WANG Chang-sheng1,2, JIA Zhong-jia1,2, OU Xiao-lin1,2, LI San-zhong1,2
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1.Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Lab of Submarine Geosciences and Prospecting Techniques, MOE and College of Marine Geosciences, Ocean University of China, Qingdao 266100, China;2.Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology(Qingdao), Qingdao 266100, China
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| Abstract: |
| Oceanic red beds (ORBs) are red to pink to brown marine sediment formed in oxic conditions. Previous studies mainly focused on the Cretaceous ORBs, but the systematic analysis and summary of Neogene ORBs are not comprehensive. This paper selects the ORBs in Neogene as the research object. Through the analysis of global ocean drilling sites data, we found that 39 sites contained Neogene ORBs. Based on the ternary diagram of the contents of the main elements CaO, Al2O3, and SiO2 of 93 discrete samples of ORBs at different oceans, the Neogene ORBs were divided into Al-ORBs and Ca-ORBs, whereby most of them were Al-ORBs. Further analysis of the magnetic susceptibility changes, the first-derivative curve of the reflectance spectroscopy, thermal demagnetization curve, and alternating field demagnetization curve of the discrete samples in sites indicate that hematite is the main mineral imparting the red color of Neogene ORBs. The low total organic carbon and low CaCO3 content of ORBs in 12 sites indicate lower biological productivity. Moreover, the average sedimentation rate of ORBs in 19 sites was 4 mm/ka, while the average deposition rate of non-red beds was 85.3 mm/ka; this feature also showed that the deposition rate of the red layer was relatively low. Based on the summary and analysis of the above characteristics of Neogene ORBs, the low organic materials accumulation rate provides favorable oxic conditions for iron oxide (hematite) formation; the iron oxides can be preserved, which causes coloration during the diagenesis, leading to the formation of global Neogene ORBs. |
| Key words: oceanic red beds Neogene hematite physical properties global distribution |