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黑柱石是一种少见的含钙铁硅酸盐矿物。通过富含黑柱石的青海省双庆铁矿区与仅含少量黑柱石的福建省马坑铁矿区矿床地质特征的对比,认为矿床中黑柱石的产生与中基性火成岩的参与有关;黑柱石的解体与硼的参与有关。 相似文献
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黑柱石是一种不常见的夕卡岩标型矿物,本次研究在新疆磁海矿区首次发现黑柱石。本文对磁海矿区的黑柱石产出地质环境、矿物共生组合、化学成分、光学性质等进行了研究。化学成分均由电子探针分析求得,计算化学简式为Ca0.98(Fe1.72Mn0.07Mg0.11)1.902+(Fe0.95Al0.03)0.983+[Si2.00O7]O(OH)。磁海矿区黑柱石的形成与基性次火山热液活动有关,是一种特殊的退变质(蚀变)夕卡岩矿物;在成矿作用晚期,随着热液活动加强,早期夕卡岩矿物可退变质形成黑柱石。黑柱石形成时间较晚,对早期形成的磁铁矿起贫化作用。将磁海矿区黑柱石与国内外其它矿区黑柱石的化学成分进行了对比,认为磁海矿区黑柱石为普通黑柱石。黑柱石在常用的矿物中较少提及,应该引起重视。 相似文献
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E. Schmidbauer Th. Fehr R. Hochleitner J. Schneider 《Physics and Chemistry of Minerals》2005,32(5-6):388-399
Structural and compositional data as well as 57Fe Mössbauer parameters were determined on a natural Mn-rich monoclinic ilvaite crystal (ideal composition CaFe 2 2+ Fe3+Si2O8(OH)) which was used for electrical conductivity and thermopower measurements (part 2 of this paper). A zonar structure was found by electron microprobe analysis with a strong decrease in Mn concentration from the rim to the centre of the crystal in a plane perpendicular to the [001] direction. X-ray powder diffraction analysis of the most Mn-rich composition was performed. Mn2+ cations populate preferentially M2 sites of the ilvaite unit cell (space group P21/a), to a lower extent they reside on M1 and a reduced part is on Ca sites. The monoclinic angle was determined to β=90.178(4)°. The structural results are compared to literature data for other natural Mn-rich as well as low-impurity ilvaites; this concerns in particular the lattice b parameter and the undecided issue of the varying β angle. In the literature, the order parameter σ, which describes the varying degree of ordering of Fe2+–Fe3+ pairs on M11 and M12 sites in chains running parallel to the [001] direction, and structural defects are thought to be related to β. The interrelationship between β and σ with respect to a possible twin domain structure is discussed. Various 57Fe Mössbauer spectra were recorded between 151 K and 327 K. Mössbauer parameters and Fe2+/Fe3+ concentration ratios were determined from the fits to the spectra. Fitting of subspectra was accomplished with the idea to find assignments of Fe2+ and Fe3+ doublets in agreement with X-ray results. The fraction of Mn2+ substituting Fe2+ on M1 sites could be estimated. 相似文献
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Endoskarn assemblages involving the Ca-silicates ilvaite, epidoteand Ca-rich garnet occur along fracture zones in the persodicIlímaussaq intrusion, South Greenland. The 1·16Ga intrusion solidified at a depth of about 3–4 km, belowa cover of sandstones and pillow-basalts of the Eriksfjord Formation.In contrast to typical skarn assemblages, the Ilímaussaqendoskarns contain albite as a main phase and they did not formin metacarbonate rocks, as these are completely lacking in thevicinity of Ilímaussaq. Instead, they record late- topost-magmatic interaction of possibly external Ca-rich fluidswith the alkaline to agpaitic magmatic rocks. Accordingly, endoskarntextures clearly reflect the magmatic textures of the precursorrocks. Phase relations in two endoskarn varieties with epidote+ albite + andradite-rich garnet ± ilvaite ± retrogradeprehnite suggest their formation at about 500°C at highoxygen fugacities slightly above the hematite–magnetiteoxygen buffer [FMQ (fayalite–magnetite–quartz) +5 to FMQ + 7] with later small modifications as a result offluid influx or cooling of the original fluid at about 300–350°C(formation of prehnite) and at about 200–250°C (oxygenisotopic re-equilibration of the albite). One model for theformation of the observed assemblages is the decomposition ofCa-bearing minerals, such as primary eudialyte, clinopyroxeneor ternary feldspar, and redistribution of the Ca by a metasomatizinglate-magmatic fluid. Stable isotope (O, H) investigations, however,favour a model in which seawater was the metasomatizing fluid,which entered the Eriksfjord basalts above the intrusion, reactedwith them (spilitization) and brought about 10–3 mol/lCa along fractures into the metasomatized rocks. Fluid–rockinteraction in the Eriksfjord basalts is documented by abundantchlorite–epidote–quartz assemblages; high fluid/rockratios allowed the fluid to retain its seawater oxygen isotopecomposition. KEY WORDS: agpaite; endoskarn; Ilímaussaq; ilvaite; metasomatism; seawater 相似文献
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黑柱石是一种矽卡岩型铅锌及铁矿床中少见的矿物,与铅锌矿体、磁铁矿体关系密切。为查明黑柱石成矿过程中与铅锌铁铜多金属成矿作用的关系,本文对金厂河Fe- Cu- Pb- Zn多金属矿床中的黑柱石产状、矿物共生组合、化学成分、分带性等开展了研究。根据电子探针数据计算可得,金厂河矿区黑柱石的化学式为:Ca0. 95- 1. 08(Fe0. 87- 1. 97Mn0. 08- 0. 36Mg0. 01- 0. 06)2+(1. 89- 2. 03)(Fe0. 82- 1. 04Al0. 01- 0. 03)3+(0. 88- 1. 15)\[Si1. 94- 2. 08O7\]O(OH)。结合矿物组合类型、产状、分带特征等,推测矿床内矽卡岩由内带逐渐向外带交代的趋势。金厂河矿区主要有3种矿物共生组合：黑柱石+磁铁矿组合,黑柱石+磁铁矿+黄铁矿+黄铜矿组合,黑柱石+方铅矿+闪锌矿+黄铜矿组合,分别对应三个不同的蚀变阶段：晚期矽卡岩阶段（代表组合I）,以石榴子石的分解为主,形成大量的黑柱石;退蚀变阶段（代表组合II）,以阳起石、黄铜矿、黄铁矿发育为主;石英- 硫化物阶段（代表组合III）,以发育大量的方铅矿、闪锌矿为主,同时这一阶段内黑柱石分解,形成阳起石、方解石、磁铁矿等。此外,黑柱石的稀土元素配分模式与石榴子石的类似,一定程度上保留了石榴子石的稀土元素特征。研究认为：黑柱石是早期石榴子石退化分解的产物,矿床自内向外逐渐交代,形成了铅锌铜矿体中以锰质黑柱石为主,而磁铁矿体、铜矿体中以含锰黑柱石为主的分带特性。锰质黑柱石有利于铅锌矿的形成,而对于磁铁矿有贫化的影响,同时也可为矿区揭露中酸性岩体和深部找矿提供重要科学意义。 相似文献
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