同步辐射X射线吸收光谱在环境矿物学中的应用     

彭明生  胥焕岩 《矿物岩石地球化学通报》2005,24(3):217-221

本文介绍了同步辐射X射线吸收光谱（XAS）在环境矿物学中的应用与进展,尤其是在矿物载体催化剂的环境催化活性研究、固-液界面的微观机制研究、毒性痕量元素在矿物中赋存状态的研究、核废料的矿物处置研究等方面的发展现状。最后指出,XAS对推动环境矿物学的发展、优化环境矿物材料和原料的工艺流程具有独特的优势,在我国还有待进一步加强其发展和应用。  相似文献   

Mineralogy,geochemistry, and sulfur isotope characteristics of sediment-hosted hydrothermal sulfide minerals from the southern Okinawa Trough     

Yamin Yang  Zhigang Zeng  Xuebo Yin  Xiaoyuan Wang  Shuai Chen  Haiyan Qi  Zuxing Chen  Bowen Zhu 《海洋学报(英文版)》2021,40(10):129-143

Studies of the mineralogy and sulfur isotope composition of sediment-hosted hydrothermal sulfide minerals in cores are important for understanding the seafloor mineralization environment and material source and reconstructing the hydrothermal history. However, the source of ore-forming materials and the history of hydrothermal activity in the southern Okinawa Trough (SOT) remain unclear. Here, the mineralogy and sulfur isotope characteristics of sulfides from gravity core HOBAB4-S2, collected between the Yonaguni Knoll IV hydrothermal field (HF) and the Tangyin HF, was investigated. Enrichments in Zn (up to 321×10?6), Cu (up to 73.7×10?6), and Pb (up to 160×10?6) and the presence of pyrite, galena, pyrrhotite and minor sphalerite and chalcopyrite provide evidence for the input of hydrothermal materials into the sediments. The pyrite morphologies include disseminated cubic, pentagonal dodecahedron, and framboidal forms. Except for minor framboidal pyrite, euhedral pyrite from core HOBAB4-S2 is mainly of hydrothermal origin with Co/Ni ratios >1 and S/Fe atomic ratios <2 in the Cu-Zn-Pb-rich layers. The occurrences of hexagonal pyrrhotite, high-Co (up to 0.17%) pyrite and high-Fe sphalerite indicate that the hydrothermal precipitates formed at medium-high temperatures and low-sulfur fugacity (fS₂) environments. The δ34S values of sulfides (0.21‰–3.45‰) with low- fS₂ mineral assemblages (e.g., pyrrhotite ± high-Fe sphalerite) in the core are significantly lower than those of magmatic rocks and seawater, indicating possible incorporation of previously formed biogenic sulfur in the sediment. Combined with the age model of the core, it is suggested that hydrothermal activity likely began in the Tangyin HF before AD 1445–1483 and that at least three active episodes may have occurred since then.  相似文献   

Clay minerals in the late Quaternary sediment of Tulare Lake,California: Implications for climate change,weathering, and erosion processes     

Junhua Guo  Christine Pyles  William Krugh  Rob Negrini 《国际泥沙研究》2019,34(5):432-443

The clay mineralogy of Tulare Lake sediment was examined to investigate hydroclimatic and environmental changes in the southern Sierra Nevada Mountains (SNM) since the most recent glacial maximum. Evolution of clay mineral assemblages elucidates significant changes in weathering, erosion, and hydroclimatic condition in the catchment. During the last glacial period (24.4–15.1 cal ka BP), low illite content implies less physical erosion of the granitic batholith rocks and a cold and arid environment in the southern SNM. Abrupt increases of illite content at 21.8–20.8 and 17.6 cal ka BP resulted from the glacier advances to the ablation zone and illite-rich glacier flour was transported down to the lake. The gradual increase of smectite induced by progressive depletion of illite-rich glacier flour from 17.6 cal ka BP toward the end of this period indicates climate was beginning to get warm and wet. From 11.9 to 5.3 cal ka BP, two warm and wet periods (10.7–9.4 and 8.2–5.2 cal ka BP) were characterized by high smectite/illite content ratios and low illite crystallinity values, suggesting intensive rainfall precipitation and more physical erosion in the highland and lowland catchment as well as more smectite formation in the terrace soils. Since the last glacial period, physical erosion, in comparison to the chemical weathering, was the dominant process responding to the hydroclimatic change in the Tulare Lake catchment. Moderate to weak chemical weathering was signified by the mostly low illite chemical weathering index of the core sediments. Such results suggest that vegetation cover in the southern SNM was low and limited.  相似文献   

河北宽城蛇纹石玉的宝石矿物学特征研究          下载免费PDF全文

徐子维  孙佳乐  郝森  刘云贵  王礼胜  宋彦军 《岩石矿物学杂志》2023,42(3):442-450

河北宽城蛇纹石玉结构细腻,颜色可呈肉红色、绿色,当地市场称之为"热河玉"。本文通过常规宝石学测试结合激光拉曼光谱、电子探针、X射线粉晶衍射、激光剥蚀等离子质谱以及可见光吸收光谱等手段对其进行了系统分析,并采用伽玛能谱仪对其放射安全性进行了检测。结果表明,肉红色样品折射率及相对密度值均较低,折射率为1.54~1.55,相对密度为2.33~2.43,主要组成矿物为斜纤蛇纹石,主要具纤维交织结构、纤维柱粒交织结构,局部可见变余生物骨架结构,次要矿物有方解石和透辉石,Fe和Mn元素含量相对较高,Fe元素含量范围在184.9×10^-6~951.7×10^-6,Mn元素含量为106.4×10^-6~287.3×10^-6;绿色样品折射率为1.55~1.56,相对密度为2.58~2.62,主要组成矿物为叶蛇纹石,具更加细腻的纤维交织结构,次要矿物为滑石及四方硫铁矿,Fe元素含量极高,可达5 979×10^-6~6 359×10^-6。结合可见光吸收光谱分析结果认为Fe³⁺、Fe²⁺以及Mn³⁺的综合作用是导致样品呈现肉红色的主要原因,而Fe²⁺和Fe³⁺则是导致绿色的主要原因。放射性检测结果显示样品的内、外照射指数及放射性比活度值均低于标准要求,对人体无放射性危害。  相似文献   

Effects of grain size distribution on mineralogical and chemical compositions: a case study from size‐fractional sediments of the Huanghe (Yellow River) and Changjiang (Yangtze River)     

Xiaojing Zhou  Anchun Li  Fuqing Jiang  Jian Lu 《Geological Journal》2015,50(4):414-433

The influence of hydrodynamics on the chemical composition of sediments is based on the uneven distribution of element abundances in different size fractions. In this study, 72 size‐fractional sediments from the Huanghe (Yellow River) and Changjiang (Yangtze River) riverbeds were measured with XRD, SEM, ICP‐AES and ICP‐MS. The analysis results show that the mineral and chemical characteristics change with grain size in the Huanghe and Changjiang sediments. According to the principal components analysis, three independent geochemical factors were found. The first factor elements, Zr, Hf, Th, U, Y, La and TiO₂ are influenced by the existence of heavy minerals. The second factor elements, Al₂O₃, alkalis, alkaline earth (excluding Ca and Sr) and most of the transitional metals are dominated by clay minerals. The third factor group includes Ca and Sr, which were controlled by calcium‐bearing mineral contents and chemical weathering intensities. The various grain size distributions greatly affect the mineralogical and chemical compositions of bulk sediments. Compared to other size fractions, the 5–6PHI size fractions of the Huanghe and Changjiang sediments have special mineralogical and chemical compositions, and intermediate volume percentages. Weight or volume percentage of each size fraction may be more suitable than mean grain‐size of the bulk sediment to elucidate the grain size effects. Chemical Index of Alteration (CIA) values increase steeply with decreasing grain size, while Weathering Index of Parker (WIP) values are relatively stable. Because of the big influence of the abundance of clay minerals on CIA values, it is questionable to use CIA as a proxy of weathering intensity. Considering the clay mineral effects, stability in values and heterogeneous material properties, WIP has the potential to indicate the chemical weathering intensity of sediments. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

月球岩浆洋演化的实验岩石学研究进展SCIEI北大核心CSCD          下载免费PDF全文

李瑞  刘建忠  庞润连  朱丹  鞠东阳  杜蔚 《岩石学报》2022,38(4):1043-1062

由于缺少直接来自月球深部的岩石样品,实验和计算模拟是认识早期月球演化过程的有效方法和手段。20世纪70年代以来,陆续开展了大量的实验岩石学和实验地球化学工作对月球岩浆洋(lunar magma ocean,LMO)演化模型进行验证和修正。但是,学界对LMO模型中的两个关键性参数,即初始物质组成和熔融深度,仍然存在不同的认识。根据月震和重力探测数据推测的平均月壳厚度的差异、月球样品含水量的研究以及新的遥感数据解译发现月表广泛分布富镁铝尖晶石(Cr#<5)等等,直接影响我们对月球初始物质组成和LMO深度以及月球深部高压矿物相的评估。本文通过整理高温高压实验岩石学和实验地球化学在研究LMO演化方面的一系列研究成果,主要聚焦以下几个科学问题:(1)月球初始物质组成中的难熔元素和挥发分含量,以及LMO深度对月壳厚度、结晶矿物的种类及含量有着决定性的影响;(2)高压矿物相石榴子石在月球深部稳定存在的可能性及其对残余岩浆中微量元素的分配行为的制约;(3)特殊类型的月球样品(包括火山玻璃、镁质岩套等)的成因机制对月球深部物质组成具有指示意义;(4)月核的不同物质组成对LMO模型的初始成分含量,特别是微量元素的限定作用。我们以最新的观测数据和月球样品的分析结果为依据,对已有的LMO演化模型进行重新评估,提出月球深部含有石榴子石的LMO演化模型的可能性,并对该方向亟需开展的工作进行探讨。  相似文献   

层硅铈钛矿的矿物学研究          下载免费PDF全文

楼凤升  张荣英  刘汉儒 《岩石矿物学杂志》1988,7(1):58-65

层硅铈钛矿是一种罕见又多变的矿物,因而至今未见详细报导。笔者在赛马碱性岩体的铀、钍、铌、稀土巨型综合矿床中获得了各种成因的新鲜矿样,作了系统的研究,指出该矿物为单斜晶系、具类似2M型白云母结构的层状钛硅酸盐。  相似文献