首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Summary Titanian ferrocolumbite is a rare accessory mineral in the spodumene-bearing pegmatites at Weinebene, Carinthia, Austria. It contains abundant exsolved niobian rutile and scarce inclusions of cassiterite that may be primary. The titanian ferrocolumbite is relatively homogeneous with Mn/(Mn + Fe) 0.24–0.33, Ta/(Ta + Nb) 0.09–0.13 (atomic ratios) and 0.47–0.88 Ti per 12 cations (2.7–5.0 wt.% TiO2). Natural specimens are considerably disordered but become more ordered on heating. Niobian rutile has Mn/(Mn + Fe) 0.00–0.04 and Ta/(Ta + Nb) 0.26–0.38; it concentrates Fe, Ta, Ti and Sn relative to the Mn- and Nb-enriched ferrocolumbite. The overall scarcity of Nb, Ta-oxide minerals in the spodumene-bearing pegmatites of southern Ostalpen conforms to their general features ranking them with the albite-spodumene type of rare-element pegmatites.With 4 Figures  相似文献   

2.
从云母微量元素特征探讨华南花岗岩的成因和演化   总被引：5，自引：1，他引：5  
云母中微量元素可分为浅源指示元素和深源指示元素。浅源指示元素Nb、Ta、Sn、Li、Rb在南岭系列云母中的含量高于长江系列,而深源指示元素Co、Ni的含量长江系列大于南岭系列。云母中Nb、Ta、Sn、Li、Rb变化特征是自身成矿演化的直接示踪剂,而Co、Ni变化特征是Fe、Cu、Au、Mo(W)、Pb、Zn成矿演化的重要示踪剂。云母中Cu、Zn、W、Mo、U、Th等元素呈波动性变化,不能灵敏指示花岗岩的成因与演化。微量元素在云母中的选择分布主要受岩浆物源化学背景的制约,同时也受岩浆侵位和分异演化程度高低以及结晶的物理化学条件变化等因素的影响。  相似文献   

3.
Paragenetic, textural, and chemical characteristics of micas from 10 rare-metal granitic stocks and the associated greisens were examined in order to identify the metallogenetic processes of the host granitoids. The investigated granitoids and type occurrences can be categorized as: (1) metaluminous, Nb + Zr + Y-enriched alkali granite (e.g., Hawashia, Ineigi, and a stock northwest of Um Naggat); (2) peraluminous, Ta > Nb + Sn ± W + Be-enriched Li-albite granites (e.g., Nuweibi, Igla, and Abu Dabbab); and (3) metasomatized, Nb » Ta + Sn + Zr + Y + U ± Be ± W-enriched apogranites (e.g., Um Ara, Abu Rusheid, Mueilha, and Homr Akarem).

Mica of the alkali granite is of the annite-siderophyllite series, and is characterized by an average FeO? of 28.14, low MgO of 0.05, a mean Fe?/(Fe? + Mg)atom. value of 0.996, TiO2 of 0.69, enhanced Al2O3 of 14.91, MnO of 0.58, Li2O of 0.26, and moderate to low F of 0.86. These characteristics are representative of the relatively highly evolved nature of the annite-siderophyllite-bearing magmas. The micas closely resemble those of the anorogenic pegmatites and A-type granites.

Primary mica of the Li-albite granites is compositionally constrained between zinnwaldite in the lower zones, and white mica in the apical, more evolved zone, and is associated with columbite-tantalite, topaz, and fluorite. The occurrence of zinnwaldite with high contents of Mn and F indicates its stabilization at rather low temperatures in Li- and F-rich sodic melts. The restriction of white mica with lower Mn, F, and Li contents to the apical zones can be attributed to either volatile degassing or to the beginning of topaz crystallization. These two factors brought about an evolutionary trend for micas, which contrasts with the documented trends of Li-micas in other Li-granites (i.e., from Li-siderophyllite or Li-muscovite to lepidolite).

Micas range in composition between white mica in the lower unaltered zones of the apogranites and Li-siderophyllite-zinnwaldite in the apical microclinized and albitized zones; this systematic compositional change appears to reflect roofward increasing in μKF and μLiF of the exsolved fluids. Columbite, cassiterite, zircon, xenotime, beryl, and fluorite are common associates of the zinnwaldites. However, white micas from the greisenized apogranite and endogreisen veins have diminishing Li contents. The subsolidus formation of zinnwaldite and Li-siderophyllite in the apogranites, and white mica in the associated greisens, represent transitions from magmatic to hydrothermal environments under the influence of decreasing P, T, salinity, and alkalinity of the exsolved fluids.  相似文献   

4.
Nb-Ta-Ti-bearing oxide minerals (Nb-Ta-bearing rutile, columbite-group minerals) represent the most common Nb-Ta host in topaz-albite granites and related rocks from the Krásno-Horní Slavkov ore district. Tungsten-bearing columbite-(Fe), W-bearing ixiolite, wodginite and tapiolite-(Fe) are extremely rare in these rocks. Rutile contains significant levels of Ta (up to 37?wt.% Ta2O5) and Nb (up to 24?wt.% Nb2O5), with Ta/(Ta?+?Nb) ratio ranging from 0.04 to 0.61. Columbite-group minerals are represented mostly by columbite-(Fe) and rarely by columbite-(Mn), with Mn/(Mn?+?Fe) ratio ranging from 0.23 to 0.94. The exceptionally rare Fe-rich, W-bearing ixiolite occurs only as inclusions in Nb-Ta-bearing rutile from quartz-free alkali-feldspar syenites (Vysoky Kámen stock). Wodginite was found only in the topaz-albite microgranite of gneissic breccia matrix that occurs in the upper most part of the Hub topaz-albite granite stock. In wodginite, the Mn/(Mn?+?Fe) ratio is 0.42?C0.51, whereas the coexisting tapiolite-(Fe) has a distinctly lower Mn/(Mn?+?Fe) ratio close to 0.06.  相似文献   

5.
91 biotites (53 from granites, 35 from highly metamorphic gneisses, 3 from redwitzites) were separated and analyzed for Fe, Mn, Zn, Cl, Sn, Ni, Co, Or, Cu, V, Mo, Pb. Biotites from gneisses contain much more Ni, Co, Cr, V but less Fe, Mn, Zn than those from granites. However, the distinction between biotites from gneisses and from granites on the basis of these elements is not certain. If a gneiss undergoes anatexis, the contents of Ni, Co, Cr, V, Zn and Sn of the preexistent biotite fractionate: Zn, Sn and Pe enter the anatectic melt readily while Ni, Co, Cr and V concentrate in the remaining matter (restite). Ni, Co, Cr and V are strongly positively correlated with one another but negatively with Fe and Zn, the latter being positively correlated with Pe. The chemical composition of biotites from granites depends not only on a potential degree of secondary decomposition into chlorite and muscovite but much more on the percentage of biotite in the rock: The more biotite, the higher the content of Ni, Co, Cr, V and the lower Fe, Zn and Sn in the biotite. Thus, it is possible to distinguish between normal and abnormal concentrations of an element in a biotite and in a rock. This might be useful in geochemical prospecting. Abnormal high concentrations of Sn and Zn were found in biotites from some granites which are connected with mineralizations of these elements. It is impossible hitherto to gain informations about the history and the parental material of a granitic magma from the minor elements in the rock or the biotite because their concentrations depend on how much biotite could be incorporated by the melt. The distribution coefficient of Cl between the lattice of 4 biotites and their fluid inclusions was determined to be 0,08.  相似文献   

6.
华南富氟花岗岩高磷和低磷亚类型对比   总被引：10，自引：3，他引：7  
黄小龙  王汝成 《地质论评》1998,44(6):607-617
根据全岩Ｐ２Ｏ５含量的多寡可将华南富氧花岗岩分为高磷亚类和低磷亚类,它们之间具较大的地球化学差异。高磷亚类以低硅、强过铝和低的ＲＥＥ总量为特征,而低磷亚类则相反。在长石、云母等矿物化学成分上这两亚类花岗岩也有所差异。高磷亚类花岗岩中磷以长石中结构磷和磷铝锂石形式存在,而低磷亚类花夺中的磷则主要存在于磷灰石等磷酸盐矿物中。  相似文献   

7.
Most rare-metal granites in South China host major W deposits with few or without Ta–Nb mineralization. However, the Yashan granitic pluton, located in the Yichun area of western Jiangxi province, South China, hosts a major Nb–Ta deposit with minor W mineralization. It is thus important for understanding the diversity of W and Nb–Ta mineralization associated with rare-metal granites. The Yashan pluton consists of multi-stage intrusive units, including the protolithionite (-muscovite) granite, Li-mica granite and topaz–lepidolite granite from the early to late stages. Bulk-rock REE contents and La/Yb ratios decrease from protolithionite granite to Li-mica granite to topaz–lepidolite granite, suggesting the dominant plagioclase fractionation. This variation, together with increasing Li, Rb, Cs and Ta but decreasing Nb/Ta and Zr/Hf ratios, is consistent with the magmatic evolution. In the Yashan pluton, micas are protolithionite, muscovite, Li-mica and lepidolite, and zircons show wide concentration ranges of ZrO2, HfO2, UO2, ThO2, Y2O3 and P2O5. Compositional variations of minerals, such as increasing F, Rb and Li in mica and increasing Hf, U and P in zircon are also in concert with the magmatic evolution from protolithionite granite to Li-mica granite to topaz–lepidolite granite. The most evolved topaz–lepidolite granite has the highest bulk-rock Li, Rb, Cs, F and P contents, consistent with the highest contents of these elements and the lowest Nb/Ta ratio in mica and the lowest Zr/Hf ratio in zircon. Ta–Nb enrichment was closely related to the enrichment of volatile elements (i.e. Li, F and P) in the melt during magmatic evolution, which raised the proportion of non-bridging oxygens (NBOs) in the melt. The rims of zoned micas in the Li-mica and topaz–lepidolite granites contain lower Rb, Cs, Nb and Ta and much lower F and W than the cores and/or mantles, indicating an exotic aqueous fluid during hydrothermal evolution. Some columbite-group minerals may have formed from exotic aqueous fluids which were originally depleted in F, Rb, Cs, Nb, Ta and W, but such fluids were not responsible for Ta–Nb enrichment in the Yashan granite. The interaction of hydrothermal fluids with previously existing micas may have played an important role in leaching, concentrating and transporting W, Fe and Ti. Ta–Nb enrichment was associated with highly evolved magmas, but W mineralization is closely related to hydrothermal fluid. Thus these magmatic and hydrothermal processes explain the diversity of W and Ta–Nb mineralizations in the rare-metal granites.  相似文献   

8.
Summary Titanium placer deposits occur in alluvial-fluvial drainage systems which dissect Moldanubian gneisses intruded by Late Variscan pegmatites (Hagendorf province) in southern Germany. Based upon their texture (zonation, exsolution lamellae, intergrowth), microchemical data (Nb, Cr, Ta, V, Fe, W, Sn) and mineral inclusions, two major grain types of intergrown rutile and ilmenite have been established. Grains of type A are always zoned and consist of rutile cores enveloped by ilmenite containing small inclusions of wolframite. A core-rim transition zone is characterized by complex relations of rutile and ilmenite, with rutile lamellae being rich in Nb, V and Fe. Types B1 and B2 aggregates consist of ilmenite with lamellae of niobian rutile and/or ilmenorutile, and additionally have inclusions of ferrocolumbite, pyrochlore, betafite, sphalerite, pyrrhotite and Fe oxides. Such grain types featuring an intimate intergrowth of rutile and ilmenite were called nigrine. Type-C grains are quite similar in their morphological appearance but consist of W-enriched rutile devoid of mineral inclusions and reaction products. Pseudorutile and leucoxene replacing minerals of the nigrine aggregates are presumably caused by supergene alteration under fluctuating redox conditions. Phosphate and aluminum remobilized by supergene processes led to the formation of hydrous Ti-rich phases containing Al, P and Fe. High Nb and W concentrations in nigrine aggregates and in rutile type C may be taken as a marker for highly differentiated granites or pegmatites. This has implications for both, heavy-mineral-based provenance analysis and stream sediment exploration.  相似文献   

9.
At Segura, granitic pegmatite veins with cassiterite and lepidolite, hydrothermal Sn–W quartz veins and Ba–Pb–Zn quartz veins intruded the Cambrian schist–metagraywacke complex and Hercynian granites. Cassiterite from Sn–W quartz veins is richer in Ti and poorer in Nb and Nb+Ta than cassiterite from granitic pegmatite. Wolframite from Sn–W quartz veins is enriched in ferberite component. The Sn–W quartz veins contain pyrrhotite, arsenopyrite, sphalerite, chalcopyrite, stannite, matildite and schapbachite and the Ba–Pb–Zn quartz veins have cobaltite, pyrite, sphalerite, chalcopyrite, galena and barite, which were analyzed by electron microprobe. The presently abandoned mining area was exploited for Sn, W, Ba and Pb until 1953. Stream sediments and soils have higher concentrations of metals than parent granites and schists. Sn, W, B, As and Cu anomalies found in stream sediments and soils are associated with Sn–W quartz veins, while Ba, Pb and Zn anomalies in stream sediments and soils are related to Ba–Pb–Zn quartz veins. Sn, W, B, As, Cu, Ba, Pb and Zn anomalies in stream sediments and soils are also related to the respective old mining activities, which increased the mobility of trace metals from mineralized veins to soils, stream sediments and waters. Stream sediments and soils are sinks of trace elements, which depend on their contents in mineralized veins and weathering processes, but Sn, W and B depend mainly on a mechanic process. Soils must not be used for agriculture and human residence due to their Sn, B, As and Ba contents. Waters associated with mineralized veins were analyzed by flame atomic absorption spectroscopy (FAAS) and ICP-AES have high As, Fe and Mn and should not be used for human consumption and agriculture activities. The highest As values in waters were all related to Sn–W quartz veins and the highest Fe and Mn values were associated with the Ba–Pb–Zn quartz veins. No significant acid drainage was found associated with the old mine workings.  相似文献   

10.
The Songshugang granite, hidden in the Sinian metasedimentary stratum, is a highly evolved rare-element granite in northeastern Jiangxi province, South China. The samples were systematically taken from the CK-102 drill hole at the depth of 171–423 m. Four types of rocks were divided from the bottom upwards: topaz albite granite as the main body, greisen nodules, topaz K-feldspar granite and pegmatite layer. Electron-microprobe study reveals that the rare-element minerals of the Songshugang granite are very different from those of other rare-element granites. Mn# [Mn/(Fe + Mn)] and Ta# [Ta/(Nb + Ta)] of columbite-group minerals and Hf# [Hf/(Zr + Hf)] of zircon are nearly constant within each type of rocks. However, back-scattered electron imaging revealed that Nb–Ta oxides and zircon of the Songshugang granite, especially those of topaz albite granite, topaz K-feldspar granite and greisen, are commonly characterized by a specific two-stage texture on the crystal scale. The early-stage Nb–Ta oxide is simply subhedral-shaped columbite-(Fe) (CGM-I) with low Mn# (0.16–0.37) and Ta# (0.05–0.29). Columbite-(Fe) is penetrated by the later-stage tantalite veinlets (CGM-II) or surrounded by complex Nb–Ta–Sn–W mineral assemblages, including tantalite-(Fe), wodginite (sl), cassiterite, and ferberite. Tantalite has wide range of Mn# values (0.15–0.88) from Fe-dominance to Mn-dominance. Wodginite with Ta>Nb has large variable concentrations of W, Sn and Ti. Cassiterite and ferberite are all enriched in Nb and Ta (Nb2O5 + Ta2O5 up to 20.12 wt.% and 31.42 wt.%, respectively), with high Ta# (>0.5). Similar to Nb–Ta oxides and Nb–Ta–Sn–W mineral assemblages, the early-stage zircon is commonly included by the later-stage zircon with sharply boundary. They have contrasting Hf contents, and HfO2 of the later-stage zircon is up to 28.13 wt.%. Petrographic features indicate that the early-stage of columbite and zircon were formed in magmatic environment. However, the later-stage of rare-element minerals were influenced by fluxes-enriched fluids. Tantalite, together with wodginite, cassiterite, and ferberite implies a Ta-dominant media. An interstitial fluid-rich melt enriched in Ta and flux at the magmatic–hydrothermal transitional stage is currently a favored model for explaining the later-stage of rare-element mineralization.  相似文献   

11.
Summary In 1961–63 the Czechoslovakian Geological Survey drilled a 1596 m deep borehole in the Sn-W-mineralized Cinovec (Zinnwald) granite cupola. The hole traversed zinnwaldite granite (ZG) to 730 m, then protolithionite granite (PG). The boundary between the two granites is a transition zone (TZ) about 10 m thick. The oxides of Nb, Ta and Ti, present in accessory amounts, are columbite, ilmenorutile, rutile and pyrochlore. The columbite occurs in both granites, but in the PG only below 1558 m depth. Its crystals are strongly zoned, the zoning representing variations in Nb/(Nb + Ta) on the one hand, and non-uniform distribution of W on the other. The columbite in the TZ is strongly enriched in W, up to 32.6 wt% WO3. The columbites with W < M4+ show the substitutions W6+ + M4+ 2(Nb, Ta)5+, where (M4+ = Ti, Sn, Th, U, Zr) and 6M4+ + 3M3+ 4Fe2+ 5(Nb, Ta)5+, where (M3+ = Sc, Y). In columbites with W > M4+, tungsten is introduced by the substitution W6+ + M4+ 2(Nb, Ta)5+, but also through the appearance of Fe3+ in the B site according to the replacement 2W6+ + Fe3+ 3(Nb, Ta)5+. The ratio Fe/(Fe + Mn + Ca) increases with depth, and Nb/(Nb + Ta) is higher in the PG.The ZG is characterized by the presence of ilmenorutile, which does not occur in the PG, where rutile contains at most only 4 wt% Nb2O5. Two types of substitution have been found in the ilmenorutile: Fe3+ + (Nb, Ta)5+ 2Ti4+; (Fe, Mn)2+ + 2(Nb, Ta)5+ 3Ti4-. For the ilmenorutiles studied, the ratio [Fe3+/(Fe, Mn)2+]at is near 1.AU- and Nb-rich phase, containing up to 36.2 wt% UO2, included in protolithionite, and missing from the ZG, has the composition of a defect pyrochlore, A2+ 2 5+(O6), and forms a solid solution with U4+B2 4+(O6]), where B4-= Ti, Si, Zr, Sn. Electron microprobe analyses indicate that this phase is strongly hydrated.The crystal chemistry of Nb-, Ta- and Ti-oxides in the Cinovec cupola reflects the complex geochemistry of its component granites and the interaction of the minerals with an F- and CO2-rich fluid phase. Among the thermodynamic parameters, fO2 plays a predominant role in the early evolutionary stages.
Résumé Un sondage profond (jusqu'à -1596m), a été réalisé en 1961–63 par le Service géologique tchécoslovaque, dans la coupole granitique, minéralisée en Sn-W, de Cinovec (Zinnwald), République tchèque. Ce sondage a recoupé un granite à zinnwaldite (ZG), relayé en profondeur (–730 m) par un granite à protolithionite (PG). Le contact entre ces deux granites est matérialisé par une zone de transition (TZ) puissante de 10 m environ. Les oxydes de Nb, Ta et Ti, présents en quantité accessoire, sont représentés par: columbite, ilménorutile, rutile et pyrochlore.La columbite apparaît tant dans ZG que dans PG, mais dans ce dernier uniquement dans la zone profonde (-1558.0 m). Ses cristaux sont fortement zonés. Le zonage reflète des variations du rapport Nb/(Nb + Ta) d'une part et une distribution hétérogène de W, d'autre part. La columbite de la zone de transition ZG-PG est très enrichie en W (jusqu'à 32.6 wt.~/ 0 W03). Les coiumbites à W < SM4+ présentent des substitutions W6+ + M4+ 2(Nb, Ta)5+, où (M44+ = Ti, Sn, Th, U, Zr) et 6M4+ + 3M3+ 4Fe2+ + 5(Nb, Ta)5-, où (M3+ = Se, Y). Dans celles à W > EM4+, outre la substitution W6+ + M4+ 2(Nb, T)5+, le tungstène est introduit grâce à l'apparition de Fe 3+ sur le site B suivant le schéma: 2W6+ + Fe3+ 3(Nb, Ta)5+. Le rapport Fe/(Fe + Mn + Ca) croit avec profondeur; celui Nb/(Nb + Ta) augmente dans PG.Le ZG est caractérisé par la présence de l'ilménorutile; par contre, celui-ci est absent dans PG, oú le rutile ne contient que 4 wt.% Nb205 au maximum. Deux types de substitution sont mis en évidence dans l'ilménorutile: Fe3+ + (Nb, Ta)5+ 2Ti4+; (Fe, Mn)2+ + 2(Nb, Ta)5+ 3Ti4+. Pour les ilménorutiles étudiés, le rapport [Fe3+/(Fe, Mn)2+]à, est proche de 1.Une phase riche en U (jusqu'à 36.2 wt.% UO2) et Nb, incluse dans la protolithionite et absente dans ZG, a composition d'un pyrochlore lacunaire A2+[B2 5+(06), formant une solution solide avec U4+E:B24+(O6), où B4+ = Ti, Si, Zr, Sn. Les analyses à la microsonde électronique indiquent que cette phase est fortement hydratée.La cristallochimie des oxydes de Nb, Ta et Ti dans la coupole de Cinovec reflète tant la complexité géochimique des granites qui la composent que l'interaction des minéraux avec une phase fluide riche en F et CO,. Parmi les paramètres thermodynamiques, fO2 joue un râle prépondérant lors des stades d'évolution précoces.
  相似文献   

12.
Summary The strongly peraluminous, P- and F-rich granitic system at Podlesí in the Krušné Hory Mountains, Czech Republic, resembles the zonation of rare element pegmatites in its magmatic evolution (biotite → protolithionite → zinnwaldite granites). All granite types contain disseminated Nb-Ta-Ti-W-Sn minerals that crystallized in the following succession: rutile + cassiterite (in biotite granite), rutile + cassiterite → ferrocolumbite (in protolithionite granite) and ferrocolumbite → ixiolite → ferberite (in zinnwaldite granite). Textural features of Nb-Ta-Ti-W minerals indicate a pre-dominantly magmatic origin with only minor post-magmatic replacement phenomena. HFSE remained in the residual melt during the fractionation of the biotite granite. An effective separation of Nb + Ta into the melt and Sn into fluid took place during subsequent fractionation of the protolithionite granite, and the tin-bearing fluid escaped into the exocontact. To the contrast, W contents are similar in both protolithionite and zinnwaldite granites. Although the system was F-rich, only limited Mn-Fe and Ta-Nb fractionation appeared. Enrichment of Mn and Ta was suppressed due to foregoing crystallization of Mn-rich apatite and relatively low Li content, respectively. The content of W in columbite increases during fractionation and enrichment in P and F in the melt. Ixiolite (up to 1 apfu W) instead of columbite crystallized from the most fluxes-enriched portions of the melt (unidirectional solidification textures, late breccia).  相似文献   

13.
广东中生代与壳幔岩浆活动有关的成矿作用十分强烈,多期成矿作用明显.在前人工作的基础上,根据矿床的成矿时代、成矿地质构造环境、主要成矿作用及形成的矿床组合,将中生代与岩浆作用有关的矿床厘定为6个矿床成矿系列：1）云开与印支期岩浆活动有关的铌、钽、磷、铁矿床成矿系列;2）粤北与燕山期花岗岩有关的有色金属、稀有金属、贵金属、非金属、铀矿床成矿系列;3）深大断裂带与燕山期基性-中酸性侵入岩有关的铜、铅、锌、金、铁、钼、钨、水晶、砷、硫铁、钒、钛矿床成矿系列;4）深变质带与区域变质、动力变质及燕山期花岗岩类有关的金、银矿床成矿系列;5）沿海与燕山期火山-侵入活动有关的铁、铜、金、银、铅、锌、钨、锡、钼、铌、钽、硫铁、水晶、萤石、叶蜡石、重晶石矿床成矿系列;6）阳春-罗定与燕山晚期壳源花岗岩类侵入活动有关的锡、钨、钼、铜、铁、铅、锌、银矿床成矿系列.论述了各成矿系列的基本特征,并对成矿系列形成的构造背景和成矿作用的时空分布及演化规律进行了探讨.  相似文献   

14.
Cassiterites from both the Beauvoir and Montebras geanited of France are typically rich in trace elements such as Nb and Ta, and contain quite a number of inclusions of columbite (dominantly manganocolumbite).Two thin sections of cassiterite crystals have been prepared for Raman microprobe analysis).The spectra obtained from different parts of the cassiterites show that the vibra-tion frequency of the A1g peak decreases with increasing Nb ,Ta,Fe and Mn atomic contents.It is worthy to note that a new peak (named the “An peak”) has been reported for the first time in the part with oriented columbite inclusions.The vibration frequency varies from 827 to 830 cm^-1.The presence of th enew peak may be attributed to structural changes of cassiterite due to the excess of Nb and Ta in the lattice and the exsolution of columbite inclusions in cassiterite.  相似文献   

15.
Summary Internal structure and mineralogy facilitate distinction of four main pegmatite types at the eastern end of the Pyrenees. Three main trends in compositional variations in Nb-Ta-Sn-REE-Ti minerals have been established: a regional trend, with Ta/(Ta + Nb) ratio increasing towards the more evolved pegmatites, Mn/(Mn + Fe) being relatively low and increasing only slightly; a single-body trend, with similar enrichment toward the late pegmatite units; a single-crystal trend, with zoning related to both Ta/(Ta + Nb) and Mn/(Mn + Fe) ratios and a tendency toward Ta-enrichment in the late growth stages. The regional geochemical enrichment trends in the Mn/(Mn + Fe) ratios and Ta/(Ta + Nb) are those expected for a beryl-columbite pegmatite type. In a single pegmatite, the evolution depends on the simultaneous growth of other mineral species. Three factors seem to control the development of zoning in columbite-tantalite crystals: availability of Mn, Ta, Fe, Nb, significant differences in solubility between mineral group end members and re-equilibria with late pegmatite fluids.
Nb-Ta-Minerale aus dem Pegmatit-Feld vom Cap de Creus, östliche Pyrenäen: Verteilung und geochemische Trends
Zusammenfassung Am Ostrand der Pyrenäen können anhand des inneren Aufbaus und der Mineralogie vier Haupttypen von Pegmatiten unterschieden werden. Die Zusammensetzungen von Nb-Ta-Sn-SEE-Ti-Mineralen folgen drei Haupttrends: einem regionalen Trend, bei dem das Verhältnis Ta/(Ta + Nb) zu den höher entwickelten Pegmatiten hin zunimmt, während Mn/(Mn + Fe) relativ niedrig ist und nur leicht zunimmt; einem lokalen (auf das jeweilige Vorkommen beschränkten) Trend mit einer ähnlichen Anreicherung zu den spätpegmatitischen Einheiten hin; einem auf Einzelkristalle bezogenen Trend mit Zonierung in bezug auf die Verhältnisse Ta/(Ta + Nb) und Mn/(Mn + Fe) und einer Tendenz zur T a-Anreicherung in den späten Wachstumsphasen. Die regionalen geochemischen Anreicherungstrends in den Mn/(Mn + Fe)- und Ta/(Ta + Nb)-Verhältnissen entsprechen jenen, wie sie für den Beryll-Columbit-Pegmatit-Typ erwartet werden. In einem einzelnen Pegmatit hängt die Entwicklung vom gleichzeitigen Wachstum anderer Mineral-Spezies ab. Drei Faktoren scheinen die Ausbildung einer Zonierung in Columbit-Tantalit-Kristallen zu kontrollieren: das Angebot an Mn, Ta, Fe und Nb, deutliche Unterschiede in der Löslichkeit der Endglieder von Mineralgruppen und die Iteequilibrierung mit spätpegmatitischen Lösungen.

With 6 Figures  相似文献   

16.
南岭地区钨锡铌钽花岗岩及其成矿作用   总被引：26，自引：1，他引：25  
在晚侏罗世时,南岭地区发生了与花岗岩有关的钨锡铌钽大规模成矿作用。依据花岗岩的岩石学、地球化学及其矿化特征,可将南岭地区含钨锡铌钽花岗岩划分为三个主要类型：含钨花岗岩、含锡钨花岗岩和含钽铌花岗岩。含钨花岗岩的地球化学特征可归纳为铝过饱和,低Ba+Sr 和TiO2,轻重稀土比值低,铕亏损强烈,富Y 和Rb,Rb/Sr 比值高,分异强烈。含锡钨花岗岩总体特征表现为TiO2 含量高,准铝质—弱过铝质,轻重稀土比值和CaO/(K2O+Na2O)比值高,富高场强元素、稀土、Ba+Sr 和Rb,低Rb/Sr 比值,分异演化程度较低。含钽铌花岗岩的地球化学特征主要为TiO2 含量和CaO/(K2O+Na2O)比值低,Al2O3/TiO2 和Rb/Sr 比值明显偏高,强过铝质,贫Ba+Sr、稀土和高场强元素,铕亏损强烈,明显富Rb 和Nb,高度分异演化。三类含矿花岗岩具有明显不同的演化特征,成矿作用与它们的演化密切相关。黑云母花岗岩主要与锡成矿作用有关,二云母花岗岩和白云母花岗岩主要产生钨矿化或锡钨共生矿化,钠长石花岗岩主要与钽铌或锡（钨）钽铌矿化有关。总结了南岭锡钨钽铌矿床的重要类型,提出了绿泥石化花岗岩型锡矿新类型,指出南岭地区要特别注意在含锡钨花岗岩中寻找此类锡矿和云英岩- 石英脉型锡钨矿。  相似文献   

17.
By the example of the Orlovka massif of Li-F granites in Eastern Transbaikalia, the major- and trace-element (Li, Be, B, Ta, Nb, W, REE, Y, Zr, and Hf) compositions of the parental melt and the character of its variations during the formation of the differentiated rock series were quantitatively estimated for the first time on the basis of electron and ion microprobe analysis and Raman spectroscopy of rehomogenized glasses of melt inclusions in quartz. It was shown that the composition of the Orlovka melt corresponded to a strongly evolved alumina-saturated granitoid magma (A/CNK = 1.12–1.55) rich in normative albite, poor in normative quartz, and similar to ongonite melts. This magma was strongly enriched in water (up to 9.9 ± 1.1 wt %) and fluorine (up to 2.8 wt %). Most importantly, this massif provided the first evidence for high B2O3 contents in melts (up to 2.09 wt %). The highest contents of trace elements were observed in the melt from pegmatoid bodies in the amazonite granites of the border zone: up to 5077 ppm Li, 6397 ppm Rb, 313 ppm Cs, 62 ppm Ta, 116 ppm Nb, and 62 ppm W. Compared with the daughter rock, the Orlovka melt was depleted at all stages of formation in SiO2 (by up to 6 wt %), Na2O (by up to 2.5 wt %), and, to a smaller extent, in Ti, Fe, Mg, Sr, and Ba, but was enriched in Mn, Rb, F, B, and H2O.  相似文献   

18.
《Applied Geochemistry》2006,21(8):1322-1334
The Ervedosa Mine, in north-eastern Portugal, has Sn-bearing quartz veins containing cassiterite and sulphides that cut Silurian schists and a Sn-bearing muscovite granite. These veins were mined for Sn and As2O3 until 1969. Cassiterite, the main Sn ore, has alternate lighter and darker growth-zones. The darker zones are richer in Fe, Nb, Ta and Ti, but poorer in Sn than the adjoining lighter zones. Exsolution blebs of ferrocolumbite, manganocolumbite, Ti ixiolite, rutile, ilmenite and rare wolframite were found in the darker zones. Arsenopyrite is the most abundant sulphide and contains inclusions of pyrrhotite, bismuth, bismuthinite and matildite. Other sulphides are pyrite, sphalerite, chalcopyrite and stannite. Secondary solid phases consisting mainly of hydrate sulphate complexes of Al, Fe, Ca and Mg (aluminocopiapite, copiapite, halotrichite, pickeringite, gypsum and alunogen, meta-alunogen) occur at the surface of the Sn-bearing quartz veins and their wall rocks (granite and schist), while oxides, hydroxides, arsenates and residual mineral phases (albite, muscovite and quartz) occur in mining tailings. Toxic acid mine waters (acid mine drainage AMD), which have high conductivity and significant concentrations of As, SO4 and metal (Cu, Zn, Pb, Fe, Mn, Cd, Ni and Co), occur in an area directly affected by the mine. Surface stream waters outside this area have low conductivity and a pH that is almost neutral. Metal and As concentrations are also lower. Stream waters within the impact area have an intermediate composition, falling between that of the AMD and the natural stream waters outside impact area. Waters associated directly with mineralised veins must not be used for human consumption or agriculture.  相似文献   

19.
The Igarapé Bahia gold deposit has developed from weathering of a near-vertical hydrothermal Cu (Au) mineralization zone. The unweathered bedrock composed of chlorite schists is mainly metamorphosed basalts, pyroclastic and clastic sedimentary rocks and iron formation. Contents and Fe/(Fe + Mg) ratios of chlorites increase from distal country rock towards the mineralization zone, which can be attributed to different water/rock ratios and locations in a hydrothermal system. In the hydrothermal system high salinity fluids convected through basin-floor rocks, stripping metals from the recharge zones with precipitation in discharge zones. The chlorite with lower Fe/(Fe + Mg) ratios indicates alteration by relatively unreacted Mg-rich fluids, occurring within recharge zones. By contrast, the chlorite with higher Fe/(Fe + Mg) ratios in the mineralization zone formed from solutions rich in Fe, Mn, Au, Cu, H2S and SiO2 within a discharge zone. The iron formation could also be formed within the discharge zone or on the basin floor from the Fe-rich fluids. The distal country rock with less chlorite content is a hydrothermal product at low water/rock ratios whereas the proximal country rock and the host rock with more chlorite content formed at high water/rock ratio conditions. The Al(IV) contents of chlorites indicate that the formation temperatures of these rocks range from 204 to 266 °C, with temperatures slightly increasing from distal country rock towards the mineralization zone.  相似文献   

20.
Two mineralogically different rare metal granites located in two distinct terranes from the Tuareg area are compared: the Tin-Amzi granite in the north of the Laouni Terrane and the Ebelekan granite in the Assodé–Issalane Terrane.The Tin-Amzi granite is enclosed within Eburnean granulitic gneisses, and consists of albite, quartz, protolithionite, K-feldspar and topaz granite (PG). The accessory minerals include columbite tantalite, U- and Hf-rich zircon, Th-uraninite, wolframoixiolite and wolframite. This facies is characterised by a mineralogical evolution from the bottom to the top underlined by a strong resorption of K-feldspar and albite and the crystalliK-feldspar of more abundant topaz and protolithionite II which is further altered in muscovite and Mn-siderite. It is underlain by an albite, K-feldspar, F-rich topaz, quartz and muscovite granite (MG), with W–Nb–Ta oxides, wolframite, Nb-rutile, zircon and scarce uranothorite as accessories.The Ebelekan granite intrudes into a coarse-grained biotite granite enclosed within upper amphibolite-facies metasediments. It comprises a zinnwaldite, albite, topaz porphyritic granite (ZG) with “snow ball” quartz and K-feldspar. The accessories are zircon, monazite, uranothorite, Ta bearing cassiterite, columbite tantalite and wodginite. It is capped by a banded aplite-pegmatite (AP).The geochemistry of Tin-Amzi and Ebelekan granites is nearly comparable. Both are peraluminous (A/CNK=1.10–1.29; ASI=1.17–1.31), sodolithic and fluorine rich with high SiO2, Al2O3, Na2O+K2O, Rb, Ga, Li, Ta, Nb, Sn and low FeO, MgO, TiO2, Ba, Sr, Y, Zr and REE contents. These rare metal Ta bearing granites belong to the P-poor subclass, relating to their P2O5 content ( 0.03–0.15 wt.%). Nevertheless, they are distinguished by their concentration of W, Sn and Ta. The Tin-Amzi granite is W–Ta bearing with high W/Sn ratio whereas the Ebelekan granite is Ta–Sn bearing with insignificant W content.At Tin-Amzi the W–Nb–Ta minerals define a sequence formed by W-columbite tantalite followed by wolframoixiolite and finally wolframite showing the effect of hydrothermal overprinting with an extreme W enrichment of the fluids. At Ebelekan, the Sn–Nb–Ta oxides follow a Mn sequence: manganocolumbite→manganotantalite→wodginite+titanowodginite→cassiterite that represents a trend of primary crystallisation resulting from progressive substitution Fe→Mn and Nb→Ta during the magmatic fractionation.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号