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1.
安哥拉Huila省Bonga碳酸岩型铌矿床烧绿石地球化学组成、演化及其与岩浆热液作用过程的关系 总被引：1，自引：0，他引：1
安哥拉Bonga碳酸岩型烧绿石矿床是一个重要的铌矿床,烧绿石是碳酸岩中主要的含Nb矿物。Bonga碳酸岩中发育了5种类型(阶段)的烧绿石(Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ)。其中烧绿石Ⅰ为岩浆(原生)烧绿石,其余为热液交代形成的烧绿石。烧绿石Ⅰ与氟磷灰石共生,以富Nb贫Ta、Ca、Na占A位和F占满Y位为特征,烧绿石的结晶和Nb、Ta等高场强元素的含量受碳酸岩浆中挥发分F和H2O的控制。Bonga环带烧绿石发育,多为原生的岩浆震荡环带烧绿石遭受了后期低温热液作用改造而成,具有岩浆振荡环带结构和热液烧绿石的化学特征。高温的热液过程中岩浆烧绿石被烧绿石Ⅱ交代,以F和Na含量的降低,Ca含量基本不变,A空位急剧增多为特征。而在稍低的温度下,经热液作用交代形成了烧绿石Ⅳ(A空位高,其他占位元素少)。最晚阶段富Sr的烧绿石Ⅲ(Sr含量较高)和烧绿石Ⅴ形成于相对低温的热液作用过程中,与石英、菱锶矿等热液矿物共生,Sr可能来源于对岩浆碳酸盐矿物的热液交代作用。在整个热液作用过程中,Bonga的烧绿石可能存在以下元素替换机制：3Nb5++2Ca2+→2Si4++Fe3++2(U,Th)4+;2Nb5++Na++2Ca2+→Si4++Fe3++2(U,Th)4++A□。在更低温、氧化的条件下,烧绿石蚀变形成大量的含铌金红石和少量的易解石,此过程中释放出Ce和Th等,形成独居石、氟碳钙铈矿、氟碳铈矿、Sr REE磷酸盐矿物和方钍石等。此外,还发现了含铌针铁矿,显示Bonga烧绿石中的Nb在表生条件下发生了迁移。 相似文献
2.
本文论述了北祁连含蓝闪石岩的岩石类型、原岩类型、特征矿物组合及产态.区内含蓝闪石岩的原岩包括优地槽内发育的各类富钠火山岩、含富钠火山质的沉积岩。在含蓝闪石岩分布区,岩石的变质相有葡萄石-绿纤石相、蓝闪石—绿片岩相、绿帘石-角闪岩相、铁铝榴石—角闪岩相等,未发现高压低温矿物组合.岩石应属区域动力变质作用产物,并对其形成环境进行了探讨. 相似文献
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碾子沟金红石矿床蚀变作用的基本特征及其与成矿的关系 总被引：4，自引：1，他引：3
矿区蚀变岩分为细晶直闪(片)岩、粗晶直闪(片)岩、绿泥片岩及滑石(片)岩4大类;一般绿泥片岩位于蚀变带边部,滑石(片)岩位于中部,直闪(片)岩位于二者之间;含矿岩石主要为直闪(片)岩、次为滑石(片)岩,绿泥片岩富含铁质矿物。蚀变作用过程划为细晶直闪石化、粗晶直闪石化、绿泥石化、滑石化及斜长石化5个阶段,前4个阶段分别形成了上述4类蚀变岩,后一阶段仅形成了矿物细脉;形成金红石的主要为滑石化、次为粗晶直闪石化及细晶直闪石化,斜长石化形成的甚微。高温热液使深部及围岩中的钛向成矿部位富集,蚀变过程中铁与钛的分离及滑石化在直闪(片)岩等上的叠加,是主要成矿作用。据蚀变岩分布规律分析,碾子沟地区应有较好成矿远景。 相似文献
5.
CCSD主孔超高压榴辉岩金红石中的矿物包裹体研究 总被引：6，自引：0，他引：6
金红石是榴辉岩中的主要含钛副矿物。中国大陆科学钻探工程（CCSD）主孔100～2000m岩心样品中，金红石榴辉岩、多硅白云母榴辉岩和蓝晶石榴辉岩中都程度不等地含有金红石。金红石既可以与其他矿物一起被石榴石、绿辉石等主要变质矿物包裹，也可以包裹其他矿物。本文利用电子探针技术，对CCSD所揭示的超高压榴辉岩的金红石中的矿物包裹体进行了鉴定和分析。结果显示，绿辉石、富铪锆石、高铝榍石、韭闪石和红闪石、斜黝帘石等矿物包裹体形成于榴辉岩相进变质至峰期变质阶段；随着超高压变质带快速折返，榴辉岩经受强烈的退变质作用，包括金红石、绿辉石在内的多种矿物都经受了退变质作用，与金红石共生的钛铁矿完全或者部分退变成含铁金红石和钛铁晶石。在退变的金红石中，还发现了透辉石＋斜长石后成合晶、低铝榍石、镁绿闪石等退变质矿物组合。 相似文献
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天然半导体矿物金红石因结构中含有类质同象替代杂质元素V和Fe,具有一定的可见光吸收和光催化活性。为改善金红石的日光光催化性能,在H2还原气氛下,对天然金红石粉末进行500～900℃不同温度的热处理改性研究。紫外-可见漫反射吸收光谱（UV-Vis diffuse reflectance absorption spectra）表明H2还原处理显著改善了金红石在可见光区460～750 nm波段的光吸收,其中900℃处理样品的光吸收提升最为明显。电子顺磁共振（EPR）和X射线光电子能谱（XPS）测试表明,随着还原温度升高,杂质元素V和Fe从高价态（V5＋,Fe3＋）向较低的价态（V4＋,V3＋,Fe2＋）转化,同时金红石表面的化学吸附水含量也有所增加。本文认为H2还原热处理引起的过渡金属元素价态的改变,尤其是较低氧化态V离子（V4＋和V3＋）的形成,可能是导致金红石样品可见光吸收显著增加的主要原因。 相似文献
7.
西大别造山带红安高压榴辉岩主要矿物为石榴石、绿辉石、冻蓝闪石、石英和绿帘石,有时可见蓝闪石、多硅白云母和钠云母.石榴石具有生长环带且边缘成分变化大,可分为代表峰期的Ⅰ型边(XMg高、Grs低)和受退变质改造的Ⅱ型边(XMg低、Grs高).石榴石内蓝闪石包体发育冻蓝闪石退变边,说明包体不能完全反映进变质条件.基质绿辉石比包体绿辉石Jd含量低,在一个晶体内成分有明显变化和沿解理缝发育冻蓝闪石,显示峰后绿辉石有成分变化和退变质改造.基质中冻蓝闪石晶体较大,核部见有蓝闪石残留,说明二者有成因联系.冻蓝闪石和绿辉石都发育后成合晶结构,石榴石有韭闪石的反应冠状体.在THERMOCALC程序计算的P-T视剖面图中,石榴石Ⅰ型边反映的峰期P-T条件为2.4～2.6GPa、570～585℃,和基质中多硅白云母Si含量等值线限定范围一致,对应硬柱石蓝闪石榴辉岩组合.石榴石Ⅱ型边P-T范围为1.9～2.4GPa、530～570℃,低于峰期条件.在可能的峰后降压过程中,岩石先后主要经历了硬柱石脱水生成绿帘石和蓝闪石、绿辉石退变为冻蓝闪石的反应阶段.绿辉石、冻蓝闪石发育的后成合晶说明晚期退变过程缺乏流体,石榴石的韭闪石冠状体也可能在该阶段产生,都受局部成分域控制.红安高压榴辉岩中各矿物与成分代表不同变质阶段,称其为冻蓝闪石榴辉岩只是对现有主要组成矿物的描述,不是基于共生关系的严格岩石学命名. 相似文献
8.
烧绿石超族矿物是指通式为A2-mB2X6-wY1-n(m=0~1.7,w=0~0.7,n=0~1.0)的氧化物。IMA-CNMNC2010年批准了烧绿石超族矿物分类命名的新方案,该方案中将B类离子用于分类,而A、Y类离子用于命名,并对已发表的烧绿石类矿物进行了重新认定。目前已有16个烧绿石超族矿物种被IMA-CNMNC正式认可,另有15种被定义为可能的新矿物种,但尚待进一步研究,在充分描述后有望得到IMA的批准承认,所有不符合新命名规则的矿物名称都将废弃。我国的烧绿石超族矿物较为丰富,并有其特点,同一个矿区产出的不同颗粒其主要成分含量变化较大,部分含放射性元素的矿物有不同程度的非晶质化。对其进行的化学成分分析、X射线衍射分析及晶体结构和离子占位研究对该类矿物的分类命名有重要意义。 相似文献
9.
在法国Ｂｅａｕｖｏｉｒ花岗岩中，烧绿石－细晶石族矿物是重要的铌钽矿物之一，主要出现在岩体的上部。大部分晶体为自形，白色、谈黄色或谈绿色，粒径为微米至毫米级。３０多个电子探针分析结果表明，主要成分为Ｎａ、Ｃａ、Ｕ、Ｎｂ，Ｔａ、Ｆ．从岩体的下部到上部，烧绿石族矿物的Ｎｂ／（Ｎｂ＋Ｔａ）比值呈升高的趋势。这些矿物富含铀，Ｕｏ＿２含量最高达１５．０５％，部分烧绿石和细晶石为铀烧绿石和铀细晶石；另一方面，在岩体下部，细晶石中Ｕｏ＿２含量平均为６．３％，而在岩体上部，烧绿石和细晶石中的Ｕｏ＿２平均含量为９．０％ 相似文献
10.
在野外地质调查的基础上,结合室内显微镜观察及电子探针分析测试,对新疆拜城波孜果尔碱性岩中的副矿物的矿物学特征和化学成分进行了研究.发现这些副矿物常以共生组合的形式产在碱性岩中,主要分布在石英二长闪长岩和石英二长岩中.烧绿石中U、Th和REE替代Ca、Na.独居石富含LREE,Th和LREE相互替代;根据独居石中w(La+ Ce) ＞40％和La/Nd比值在1.6～4.5,推断独居石为热液成因.磷钇矿中富含REE,且以HREE为主;w(Th)＞w(U).锆石中Zr/Hf比值在60％以上,符合碱性岩特征;其Th/U比值为0.6,属于岩浆锆石.星叶石中w(Rb2O)、w(Cs2O)较高.萤石中Y、Ce替代Ca.锆石中的钍石w(U)明显高于磁铁矿中钍石w(U).在石英二长岩中,烧绿石的w(CaO)、w(TiO2)、w(ZrO2)、w(U3O8),磷钇矿的w(Y2O3),星叶石的w(TiO2),萤石的w(Ca),氟碳铈镧矿的w(CaO)较丰富;而在石英二长闪长岩中,烧绿石的w(Ce2O3),磷钇矿的REE含量,星叶石的w(Nb2O5)、w(Rb2O),萤石w(Ce)、w(Y)和氟碳铈镧矿的w(La2O3)较高. 相似文献
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碳酸盐岩红色风化壳Ce异常特征及形成机理 总被引：6，自引：0，他引：6
Ce在贵州碳酸盐岩红色风化壳剖面上部表现为正异常,在底部稀土超常富集层显示强烈亏损。通过对Ce的质量迁移系数的计算,结合相态分析和水化学分析结果,对碳酸盐岩红色风化壳中“的异常行为进行系统的分析后发现：在剖面上部,Ce^3＋氧化水解,水解产物主要与铁锰氧化物共沉淀,少量的与粘土矿物结合,使得ce保留而相对显示正异常;在剖面底部,Ce负异常一方面来源于对基岩负异常的继承;更重要的是,Ce较其他轻稀土稳定,发生迁移富集的量远远小于La,Nd等轻稀土元素,导致Ce在底部富集时相对于其他轻稀土元素发生强烈亏损。而Ce与HCO3^-络合迁出并不是导致碳酸盐岩红色风化壳中强烈Ce负异常的主要原因。 相似文献
13.
《Applied Geochemistry》2000,15(6):695-723
Ground and surface waters collected from two undisturbed Zn–Pb massive sulphide deposits (the Halfmile Lake and Restigouche deposits) and active mines in the Bathurst Mining Camp (BMC), NB, Canada were analysed for the rare earth elements (REE). REE contents are highly variable in waters of the BMC, with higher contents typical of waters with higher Fe and lower pH. There are significant differences between ground- and surface waters and between groundwaters from different deposits. The REE contents of surface waters are broadly similar within and between deposit areas, although there are spatial variations reflecting differences in pH and redox conditions. Surface waters are characterised by strong negative Ce anomalies ([Ce/Ce*]NASC as low as 0.08), produced by oxidation of Ce3+ to Ce4+ and preferential removal of Ce4+ from solution upon leaving the shallow groundwater environment. Groundwaters and seeps typically lack significant Ce anomalies reflecting generally more reducing conditions in the subsurface environment and indicating that Ce oxidation is a rapid process in the surface waters. Deeper groundwaters at the Halfmile Lake deposit are characterised by REE patterns that are similar to the host lithologies, whereas most groundwaters at the Restigouche deposit have LREE-depleted patterns compared to NASC. Halfmile Lake deposit groundwaters have generally lower pH values, whereas Restigouche deposit groundwaters show greater heavy REE-complexation by carbonate ions. Shallow waters at the Halfmile Lake and Stratmat Main Zone deposits have unusual patterns which reflect either the adsorption of light REE onto colloids and fracture-zone minerals and/or precipitation of REE–phosphate minerals. Middle REE-enrichment is typical for ground- and surface waters and is highest for neutral pH waters. The labile portion of stream sediments are generally more middle REE-enriched than total sediment and surface waters indicating that the REE are removed from solution by adsorption to Fe- and Mn-oxyhydroxides in the order middle REE≥light REE>heavy REE. 相似文献
14.
P. A. van Aken V. J. Styrsa B. Liebscher A. B. Woodland G. J. Redhammer 《Physics and Chemistry of Minerals》1999,26(7):584-590
The Fe M
2,3-edge spectra of solid solutions of garnets (almandine-skiagite Fe3(Al1–xFex)2[SiO4]3 and andradite-skiagite (Fe1–xCax)3Fe2[SiO4]3), pyroxenes (acmite-hedenbergite (Ca1–xNax)(Fe2+
1−xFe3+
x)Si2O6), and spinels (magnetite-hercynite Fe(Al1–xFex)2O4) have been measured using the technique of parallel electron energy-loss spectroscopy (EELS) conducted in a transmission
electron microscope (TEM). The Fe M
2,3 electron energy-loss near-edge structures (ELNES) of the minerals exhibit a characteristic peak located at 4.2 eV and 2.2 eV
for trivalent and divalent iron, respectively, prior to the main maximum at about 57 eV. The intensity and energy of the pre-edge
feature varies depending on Fe3+/ΣFe. We demonstrate a new quantitative method to extract the ferrous/ferric ratio in minerals. A systematic relationship
between Fe3+/ΣFe and the integral intensity ratio of the main maximum and the pre-edge peak of the Fe M
2,3 edge is observed. Since the partial cross sections of the Fe M
2,3 edges are some orders of magnitude higher than those of the Fe L
2,3 edges, the Fe M
2,3 edges are interesting for valence-specific imaging of Fe. The possibility of iron valence-specific imaging is illustrated
by Fe M
2,3-ELNES investigations with high lateral resolution from a sample of ilmenite containing hematite exsolution lamellae that
shows different edge shapes consistent with variations in the Fe3+/ΣFe ratio over distances on the order of 100 nm.
Received: 14 April 1998 / Revised, accepted: 8 March 1999 相似文献
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We report strong magnetic linear dichroism (MLD) at the Fe L23 and O K edges of the antiferromagnetic compound hematite -Fe2 O3 in high-resolution orientation- and temperature-dependent electron energy-loss spectroscopy (EELS). Large intensity differences of corresponding spectral features are observed when the Fe L23 and O K edges are measured with momentum transfer either parallel or perpendicular to the magnetization. The resultant difference spectra for the Fe L23 edges is consistent with the MLD observed in X-ray absorption spectroscopy. For the first time we have observed MLD at the O K edge, where the magnetic origin of this dichroism is demonstrated by temperature-dependent investigations across the Morin transition temperature TM= 263 K, at which the Fe electron spins, i.e. the magnetic moments, rotate by 90°. The O K edge MLD is interpreted in terms of superexchange between the spins of the Fe 3d and O 2p electrons through overlapping Fe 3d and O 2p orbitals. The experiments were performed in a transmission electron microscope (TEM), yielding information about the anisotropic electronic structure at nanoscale spatial resolution when operated with a focused electron probe. The effects of MLD at the Fe L23 edges on the determination of Fe3+/Fe in hematite at submicrometre scale using different independent quantification methods are discussed. 相似文献
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Pyrochlore-group minerals are the main concentrators of niobium in carbonatites of the Belaya Zima alkaline pluton. Fluorcalciopyrochlore, kenopyrochlore and hydropyrochlore were identified in chemical composition. Their main characteristics are given: compositional variation, morphology, and zoning. During evolution from early calcite to late ankerite carbonatites, the UO2, TiO2, REE, and Y contents gradually increased. All carbonatite types are suggested to contain initial fluorcalciopyrochlore. However, in calcite–dolomite and ankerite carbonatites, it is partially or completely hydrated due to hydrothermal processes at the late stage of the pluton. This hydration resulted in the appearance of kenopyrochlore and hydropyrochlore due to removal of Ca, Na and F, and input of Ba, H2O, K, Si, Fe, and probably U and REE. At the last stage of the pluton, this hydrated pyrochlore was replaced by Fe-bearing columbite. 相似文献
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Recent exploration work in South Morocco revealed the occurrence of several carbonatite bodies, including the Paleoproterozoic Gleibat Lafhouda magnesiocarbonatite and its associated iron oxide mineralization, recognized here as iron-oxide-apatite (IOA) deposit type. The Gleibat Lafhouda intrusion is hosted by Archean gneiss and schist and not visibly associated with alkaline rocks. Metasomatized micaceous rocks occur locally at the margins of the carbonatite outcrop and were identified as glimmerite fenite type. Rare earth element (REE) and Nb mineralization is mainly linked to the associated IOA mineralization and is represented by monazite-(Ce) and columbite-(Fe) as major ore minerals. The IOA mineralization mainly consists of magnetite and hematite that usually contain large apatite crystals, quartz and some dolomite. Monazite-(Ce) is closely associated with fluorapatite and occurs as inclusions within the altered parts of apatite and along cracks or as separate phases near apatite. Monazite shows no zonation patterns and very low Th contents (<0.4 wt%), which would be beneficial for commercial extraction of the REE and which indicates monazite formation from apatite as a result of hydrothermal volatile-rich fluids. Similar monazite-apatite mineralization and chemistry also occurs at depth within the carbonatite, although the outcropping carbonatite is barren, suggesting an irregular REE ore distribution within the carbonatite body. The barren carbonatite contains some tiny unidentified secondary Nb-Ta-U phases, synchysite and monazite. Niobium mineralization is commonly represented by anhedral minerals of columbite-(Fe) which occur closely associated with magnetite-hematite and host up to 78 wt% Nb2O5, 7 wt% Ta2O5 and 1.6 wt% Sc2O3. This association may suggest that columbite-(Fe) precipitated by an interaction of Nb-rich fluids with pre-existing Fe-rich minerals or as pseudomorphs after pre-existing Nb minerals like pyrochlore. Our results most strongly suggest that the studied mineralization is economically important and warrants both, further research and exploration with the ultimate goal of mineral extraction. 相似文献
18.
REE mineralization in the carbonatites of the sung valley ultramafic-alkaline-carbonatite complex,Meghalaya, India 总被引：1，自引：0，他引：1
The Early Cretaceous Sung Valley Ultramafic-Alkaline-Carbonatite (SUAC) complex intruded the Proterozoic Shillong Group of rocks and located in the East Khasi Hills and West Jaintia Hills districts of Meghalaya. The SUAC complex is a bowl-shaped depression covering an area of about 26 km2 and is comprised serpentinised peridotite forming the core of the complex with pyroxenite rim. Alkaline rocks are dominantly ijolite and nepheline syenite, occur as ring-shaped bodies as well as dykes. Carbonatites are, the youngest intrusive phase in the complex, where they form oval-shaped bodies, small dykes and veins. During the course of large scale mapping in parts of the Sung Valley complex, eleven carbonatite bodies were delineated. These isolated carbonatite bodies have a general NW-SE and E-W trend and vary from 20–125 m long and 10–40 m wide. Calcite carbonatite is the dominant variety and comprises minor dolomite and apatite and accessory olivine, magnetite, pyrochlore and phlogopite. The REE-bearing minerals identified in the Sung Valley carbonatites are bastnäsite-(Ce), ancylite-(Ce), belovite-(Ce), britholite-(Ce) and pyrochlore that are associated with calcite and apatite. The presence of REE carbonates and phosphates associated with REE-Nb bearing pyrochlore enhances the economic potential of the Sung Valley carbonatites. Trace-element geochemistry also reveals an enrichment of LREEs in the carbonatites and average ΣREE value of 0.102% in 26 bed rock samples. Channel samples shows average ΣREE values of 0.103 wt%. Moreover, few samples from carbonatite bodies has indicated relatively higher values for Sn, Hf, Ta and U. Since the present study focuses surface evaluation of REE, therefore, detailed subsurface exploration will be of immense help to determine the REE and other associated mineralization of the Sung Valley carbonatite prospect. 相似文献
19.
通过我国氧化矿石伴生银赋存特征的系统研究后指出,银以独立银矿物为主,少量为离子吸附银和类质同象银。银矿物组合及矿化系列、产出形态、结构、粒度及嵌布类型与原矿的成矿溶液性质和氧化程度有关。铅、锌、铁氧化物和残留的硫化物是银的主要载体矿物。银的配分受矿石氧化强度、矿物组合及嵌布形式控制。这一研究成果为有效提高银的回收率提供了科学依据。 相似文献
20.
Geological and geochemical characteristics of REE iron formation (REEIF), a term proposed by Prof. Tu Kuang-chih to specify a special type of Precambrian iron formations rich in REE, are discussed in this paper with special reference to its REE contents, REE distribution patterns, the formation mechanism, the relationship between its development and the multi-stage evolution of the continental crust in China, and the implications of REE as an indicator of oxidation state for ancient atmosphere. Major conclusions are outlined as follows:
- REEIFs are characterized by high REE concentrations against the very low REE levels in normal Precambrian iron formations.
- REEIFs are formed by marine sedimentary-diagenetic processes in miogeosynclines or transition zones during Proterozoic times To some extent, volcanic activity may play an important role in the deposition of ore-forming materials. In a broader sense, REEIFs belong to Fe-bearing dolomite formations. Most REEIFs in China may be superimposed by late geological processes such as hydrothermal-metasomatism, migmatization and metamorphism. Generally, REEIFs have much in common with stratabound ore deposits in respect to their characteristic features.
- Similar to Precambrian iron formations, REE are enriched in LREE. But, the degree of LREE enrichment is noticed to increase of total REE content. Most REEIFs are characterized by high ratios of σ Ce/σY, (Mg+Fe)/Ca, Na/K, Nb/Ta, Zr/Hf, Th/U, Ba/Sr, etc.
- The extensive occurrence of REEIFs indicates higher REE abundance in the continental crust of China, thus lending further support to the multi-stage theory regarding the evolution of chemical elements and the differentiation in the continental crust of China.
- Preliminary data seem to support the time-dependence of REE distribution patterns and relative Eu contents of REEIFs in China.