Acta Scientiarum Naturalium Universitatis Pekinensis ›› 2019, Vol. 55 ›› Issue (5): 915-924.DOI: 10.13209/j.0479-8023.2019.065

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Mineralogical Characteristics of Natural Semiconducting Minerals in Danxia Red Layers of Lang Mountain, Xinning, Hunan Province, China

XIAO Yuxiong, LI Yanzhang, DING Hongrui, LI Yan, LU Anhuai†   

  1. Key Laboratory of Orogenic Belts and Crustal Evolution (MOE), Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871
  • Received:2018-12-14 Revised:2019-05-01 Online:2019-09-20 Published:2019-09-20
  • Contact: LU Anhuai, E-mail: ahlu(at)pku.edu.cn

湖南新宁崀山丹霞红层天然半导体矿物的矿物学特征研究

肖育雄, 黎晏彰, 丁竑瑞, 李艳, 鲁安怀†   

  1. 造山带与地壳演化教育部重点实验室, 环境矿物功能北京市重点实验室, 北京大学地球与空间科学学院, 北京 100871
  • 通讯作者: 鲁安怀, E-mail: ahlu(at)pku.edu.cn
  • 基金资助:
    国家自然科学基金(41872042, 41522201)资助

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Abstract:

After fieldwork, metallic minerals in the samples collected from the red layers of Danxia located in Lang mountain, Xinning, Hunan province, were characterized by complementary methods, including Polarizing Optical Microscope (POM), Environmental Scanning Electron Microscopy (ESEM), Energy Dispersive X-ray analysis (EDX), High Resolution Transmission Electron Microscopy (HRTEM), Electron Probe Micro-Analysis (EPMA), micro-area X-Ray Diffraction (XRD), micro-Raman spectra (μ-Raman), and X-ray fluorescence (XRF), either by in situ analysis or powder analysis. The dominant natural semiconducting minerals from the red layers of Danxia were hematite and anatase. In addition, the contents of iron and titanium in the red layers were 2.8 times and 2.4 times higher than that of the non-red layers, respectively. Mineralogical investigation revealed that the majority of Fe/Ti oxides were presented like cementating coarse silicate minerals (feldspar, quartz and biotite), suggesting these Fe/Ti oxides were formed exogenically after weathering and eluviation of Fe and Ti-bearing silicate minerals (ilmenite and biotite). Semiconducting properties exhibited by exogenic hematite and anatase in the red layers of Danxia can provide fundamental information to further study the photocatalytic properties and environmental effects of the Danxia red layers, and to understand the interrelationship between the Cretaceous oceanic red bed and continental red bed on the Earth’s surface.

Key words: Danxia landform, iron oxide, titanium oxide, characteristics of mineral

摘要：

在野外勘察的基础上, 采用原位和分离处理两种样品制备方法, 利用偏光显微镜(POM)、环境扫描电子显微镜(ESEM)、X射线能谱(EDX)、高分辨透射电子显微镜(HRTEM)、电子探针(EPMA)、微区X射线衍射(XRD)、显微拉曼光谱(μ-Raman)和X射线荧光(XRF)技术, 揭示湖南新宁崀山丹霞红层中金属矿物的矿物学特征。结果表明, 该丹霞红层砂岩中的主要金属矿物铁钛氧化物以天然半导体矿物赤铁矿和锐钛矿为主, 红层中Fe和Ti元素的平均含量分别是非红层的2.8倍和2.4倍; 绝大部分铁钛氧化物以胶结物的形式赋存在大颗粒矿物(如石英、长石和云母)之间, 推测为红层中含钛硅酸盐矿物(钛铁矿或黑云母)风化之后经过淋滤作用原位沉积的产物。由于赤铁矿与首次在红层中发现的锐钛矿均具有半导体性质, 研究结果可为丹霞红层在地球表面的光催化性质和环境效应研究以及认识和理解白垩纪大洋红层与陆相红层的相互关系提供基础资料。

关键词: 丹霞红层, 铁氧化物, 钛氧化物, 矿物学特征

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