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1.
Mansour Rezaei Azizi Ali Abedini Samad Alipour Hashem Bagheri 《Arabian Journal of Geosciences》2018,11(22):719
The Laal-Kan fluorite deposit (west of Zanjan city, NW Iran) mainly occurred as some open-space filling and vein/veinlet in the schist of the Paleozoic age. Mineralogically, calcite, fluorite types (white, smoky, and violet), and quartz are the principal constituents accompanied by a number of minor accessory minerals such as hemimorphite, hematite, barite, and clays. Based on chemical analyses, fluorites of various colors were found to have low rare earth element (REE) concentrations (4.16–25.67 ppm). The chondrite-normalized REE patterns indicated that early fluorites were enriched in LREE, relative to HREE, whereas late fluorites were enriched in HREE relative to LREE. This study, therefore, indicated that fugacity of oxygen likely played a significant role in the occurrence of positive Ce and negative anomaly in the late fluorite. Furthermore, the Gd behavior of the fluorite samples could be attributed to the Gd-F complex in ore-forming fluids. On the other hand, low pH hydrothermal fluids under alkaline conditions were probably the main mechanism responsible for the deposition of the early fluorites in this district. Fluorite-hosted fluid inclusion analyses also indicated that fluorite-forming fluids consisted of NaCl, MgCl2, CaCl2, and LiCl with a narrow TH (118–151 °C) and high salinities (18.96–23.47 wt.% NaCl equiv.). Further, the diagram of Tb/La-Tb/Ca ratios revealed that fluorites were predominantly deposited in the hydrothermal environment and the late stage fluorites could be considered as the product of the secondary mineralization of the early fluorites due to the interaction of the fluid with the early fluorites. 相似文献
2.
El-Feky M.G. 《中国地球化学学报》2011,30(4):430-443
Altered granite occurrences (GII and GV) at Gabal (G.) Gattar are the most important mineralized rocks hosting U-mineralization in Egypt. This mineralized granite is affected by multi-stage hydrothermal alteration proc-esses along brittle structures. This alteration comprises pre-ore alkali-metasomatism and ore-stage hydrothermal hematitization, silicification, kaolinitization, fluoritization, carbonatization and episyenitization. Autoradiographic examination indicates that primary uranium mineralization is present as massive or disseminated ores along tectonic fractures, interstitially in granular minerals, and as cements of breccias. Uraninite, pitchblende and coffinite are the main primary minerals, while uranophane and kasolite are the secondary ones. Galena, chalcopyrite, pyrrohtite and pyrite are the most abundant sulphides in association with uranium mineralizations. Hydrothermal alterations at the GII occurrence exhibit an increase in Ni, Cu, Zn, Pb, Mo, Nb, Rb beside HREEs and a decrease in Ba, Co, Sr, and V, while alterations at the GV occurrence show enrichment in Ni, Cu, Pb, Mo, Nb, Y, HREEs and depletion in Zn, Ba, Co, Rb, Sr, and V. Hydrothermal alteration during the late magmatic stage is also identified through the development of unusual REE patterns and fractionation of ratios like Zr/Hf and Y/Ho out of the CHARAC (Charge Radius Con-trolled) range. Non-chondritic Y/Ho ratio at GV is of larger value than chondritic one which may result from wa-ter-rock interaction or print from the encompassing sedimentary rocks. Fluid inclusion studies on quartz and fluorite revealed that temperatures of the mineralizing fluids range between 126 and 240℃ at pressure ≤0.5×108 Pa and give salinity values ranging between 1 wt% and 7.8 wt% NaCl equivalent. 相似文献
3.
REE and fluid inclusions in zoned fluorites from Eastern Transbaikalia: Distribution and geochemical significance 总被引：1，自引：0，他引：1
S. F. Vinokurov V. N. Golubev T. L. Krylova V. Yu. Prokof’ev 《Geochemistry International》2014,52(8):654-669
Special methodology was used to study the distribution of REE and some other elements in zoned fluorites from the different deposits of Eastern Transbaikalia. Fluorites from the uranium and polymetallic ore fields sharply differ in their REE distribution pattern and the composition of fluid inclusions, which reflects the geochemical specifics and indicates the possible sources of parental solutions. A gradual change in REE distribution patterns established in the successive growth zones of fluorites clearly coincides with the gradual decrease of temperature and mineralization of fluid inclusions. It is suggested that a change in the REE distribution pattern was provoked by the crystallochemical differentiation related to the formation of nano-sized mineral admixtures of REE phosphates and/or fluorcarbonates, which possess an ability to the selective accumulation of different REE groups. It was found that the zoned fluorites from the Streltsovka and Garsonui deposits show an opposite trends in the change of REE pattern with zonation. With a general decrease in total REE contents, fluorite from the Streltsovka deposit shows a change from positive parabolic to subchondritic pattern, while that from the Garsonui deposit, varies from the negative via subchondritic to the positive patterns. 相似文献
4.
四川牦牛坪稀土矿床萤石Sr、Nd同位素对地幔成矿流体的指示意义 总被引：14，自引：0，他引：14
萤石是四川牦牛坪稀土矿床主要的脉石矿物之一，其形成贯穿了整个稀土成矿过程，因此同位素的研究对探讨萤石和稀土成矿流体的来源具有重要的价值。矿区6件萤石样品的Sr、Nd同位素组成没有明显差异，结合围岩（碳酸岩－正长岩，花岗岩）同位素组成特征研究表明，不同颜色、来自不同矿石类型、具有不同REE类型的萤石为同源产物，稀土成矿流体来源于富集地幔，与区内碳酸岩－正长岩岩浆活动密切相关。 相似文献
5.
内蒙古敖包吐萤石矿床的Sr、Nd、Pb同位素地球化学特征 总被引：2，自引：1，他引：1
敖包吐萤石矿床是内蒙古北部苏莫查干地区单一萤石矿集区中的一个代表性矿床,产于早二叠世大石寨组火山-沉积岩与早白垩世敖包吐花岗岩的接触带上。文章通过分析该矿床岩、矿石的微量元素和稀土元素,揭示出萤石的成矿作用可分为2个阶段,即交代作用和充填作用。交代作用过程中大石寨组的结晶灰岩可能为萤石的形成提供了部分Ca来源,萤石矿石的稀土元素配分模式与海水基本类似,具有Ce负异常;成矿作用后期主要表现为充填作用,形成颗粒粗大的萤石,表现为重稀土元素富集的特征,并随着萤石的沉淀析出,稀土元素总量逐渐下降,反映出成矿流体经历了较长期的演化过程。各地层单元、花岗岩体和萤石矿石的Sr、Nd、Pb同位素研究表明,萤石的放射性同位素组成具有壳、幔源混合的特点,成矿物质来源具有多源性。早白垩世敖包吐花岗岩可能是萤石中F的主要来源,而大石寨组的结晶灰岩则可能提供了Ca。另外,Pb、Nd同位素的极大不均一性,有可能是成矿流体在运移过程中对艾力格庙群放射性组分的选择性吸收的结果。萤石成矿作用与钾玄岩的时空关系暗示了萤石的成矿过程可能是中国东部岩石圈减薄和下地壳的置换地质事件的结果。在构造转型的过程中,燕山中期富碱的酸性花岗岩浆的活动分异出富含F的成矿流体,与幔源流体混合,沿区域重新活化的深大断裂和大石寨组的层间破碎带上升,交代其间的灰岩透镜体,从而形成敖包吐中型萤石矿床。 相似文献
6.
阜新萤石成矿区稀土元素地球化学特征及指示意义 总被引：1，自引：0，他引：1
为了研究阜新萤石成矿机制,对其稀土元素地球化学特征进行了分析。阜新地区萤石矿赋存于早二叠世、晚三叠世和晚侏罗世花岗岩中。地球化学分析结果显示,所有萤石均具有弱的Ce负异常,其稀土配分模式存在3种类型:Eu明显亏损型、Eu弱亏损型和Eu富集型。萤石中稀土元素的含量并不随围岩中的稀土元素含量的增加而增加,晚期侵入的花岗岩富集轻稀土元素。从成矿早期到成矿晚期,萤石的稀土元素配分型式从Eu明显亏损型向富集型演化,稀土元素总量逐渐降低。赋存于早二叠世和晚三叠世花岗岩中萤石矿流体包裹体中SO42-含量及液相成分还原参数指标指示,成矿流体由还原条件向氧化条件转变,成矿物质主要来源于赋矿花岗岩。 相似文献
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8.
The Gardar failed-rift Province is world-famous for its (per-)alkaline plutonic rocks. Elevated contents of F in the mantle source and F-enrichment in the parental melts have been suggested to account for the peculiarities of the Gardar rocks (e.g. their rare mineralogy, extreme enrichment of HFSE elements, Be or REE in the Ilímaussaq agpaites, and the formation of the unique Ivigtut cryolite deposit). To constrain the formation and chemical evolution of F-bearing melts and fluids, fluorides (fluorite, cryolite, villiaumite, cryolithionite), calcite and siderite from the Ilímaussaq, Motzfeldt and Ivigtut complexes were analysed for their trace element content focusing on the rare earth elements and yttrium (REE).The various generations of fluorite occurring in the granitic Ivigtut, agpaitic Ilímaussaq and miaskitic to agpaitic Motzfeldt intrusions all share a negative Eu anomaly which is attributed to (earlier) feldspar fractionation in the parental alkali basaltic melts. This interpretation is supported by the abundance of anorthositic xenoliths in many Gardar plutonic rocks.The primary magmatic fluorites from Ilímaussaq and Motzfeldt display very similar REE patterns suggesting a formation from closely related parental melts under similar conditions. Hydrothermal fluorites from these intrusions were used to constrain the multiple effects responsible for the incorporation of trace elements into fluorides: temperature dependence, fluid migration/interaction and complexation resulting in REE fractionation. Generally, the REE patterns of Gardar fluorides reflect the evolution and migration of a F/CO2-rich fluid leading to the formation of fluorite and fluorite/calcite veins. In certain units, this fluid inherited the REE patterns of altered host rocks. In addition, there is evidence of an even younger fluid of high REE abundance which resulted in highly variable REE concentrations (up to three orders of magnitude) within one sample of hydrothermal fluorite.The REE patterns of the granitic Ivigtut intrusion show flat to slightly heavy-REE-enriched patterns characterised by a strong tetrad effect. This effect is interpreted to record extensive fluid–rock interaction in highly fractionated, Si-rich systems.Interestingly, the fluorides appear to record different source REE patterns, as the spatially close Motzfeldt and Ilímaussaq intrusions show strong similarities and contrast with the Ivigtut intrusion located 100 km NE. These variations may be attributed to differences in the tectonic position of the intrusions or mantle heterogeneities. 相似文献
9.
YUAN Shunda ;PENG Jiantang ;HU Ruizhong ;BI Xianwu ;QI Liang ;LI Zhaoli ;LI Xiaomin ;SHUANG Yan 《中国地球化学学报》2008,27(4):342-350
In this paper the authors present the REE concentrations and Sr and Nd isotopic compositions of fluorites from the Bailashui tin deposit of the Furong ore field, southern Hunan Province. The results showed that the total amount of REE in fluorites is usually low, ranging from 0.705 to 8.785 μg/g with the chondrite-normalized REE distribution patterns similar to those of the Qitianling granites in the study area, characterized by LREE-enrichment patterns with pronounced negative Eu anomalies. The fluorites vary in Sr isotopic composition within the range of 0.7083-0.7091, the values are lower than those of the granites and higher than those of the host carbonate rocks in this area. The εNd（t） values of fluorites vary between -9.4 and ＋10.3, revealing that both the crust- and mantle-source materials were involved in the ore-forming hydrothermal fluids. Combined with previous studies on this ore deposit, the Bailashui tin deposit is temporally and spatially closely related with granitic magmatism in this area. The hydrothermal fluorites are the product of fluid/rock interactions between granitic magmatic hydrothermal fluid and marine carbonate rocks. The REE and F in the ore-forming fluid were derived from the granites, whereas Sr in the ore-forming fluid came mainly from the granitic magmatic hydrothermal fluid and marine carbonate rocks, although variations in Sr isotopic composition cannot be explained by a simple mixture of these two end-members. Evidence demonstrated that the ore-forming fluids are of crustal-mantle mixing origin, but that the fluids were probably incompletely homogenized and this may be caused by inhomogeneous mixing of the fluids of different sources. 相似文献
10.
11.
The use of vein fluorite as probe for paleofluid REE and Sr-Nd isotope geochemistry: The Santa Catarina Fluorite District, Southern Brazil 总被引：1，自引：0，他引：1
Fluorite can be used as a probe for the source of Sr and REE, as well as for the Sr and Nd isotope systematics of mineralizing solutions, allowing characterization of the composition, oxidation state and sources of the fluids. The 87Sr / 86Sr ratios in vein fluorite from the Santa Catarina Fluorite District, southern Brazil, are low (0.720 to 0.745) relative to those of the majority of host granites at the time of mineralization (90 Ma), but are similar to those of less abundant and less evolved Sr- and Ca-rich granites and plagioclases of the heterogeneous Pedras Grandes granite association. Major contributions of Sr from the unradiogenic Parana Basin rocks (87Sr / 86Sr90 Ma = 0.705 to 0.718) are unlikely, considering the radiogenic character of the lower 87Sr / 86Sr end-member in fluorite mixing lines. Estimated fluorite fluid partition coefficients (KdSr-Ca = 0.019 and DSr ≈ 600) indicate a Sr / Ca ratio in the fluorite-forming solution of 0.012, and Sr contents of 0.05 to 0.25 ppm, which are similar to those of present-day granitic geothermal waters. Initial Nd isotopic compositions of the vein fluorites (0.5120 to 0.512) are similar to those of the Pedras Grandes granites. The 143Nd / 144Nd90 Ma of the evolved granites of the Tabuleiro granite association, their accessory fluorites and the Parana Basin rocks are considerably more radiogenic (0.5120 to 0.5127) and these are thus considered to be unlikely sources of the fluids. The REE patterns of vein fluorites, normalized to upper continental crust, show a range of LREE-depleted patterns, with highly variable positive and negative Eu anomalies. The host Pedras Grandes granites show flat to slightly depleted UCC normalized LREE patterns with strong negative Eu anomalies. Depletion of the LREE in fluorites resulted from the mobility of HREE fluoride complexes during fluid migration. A REE fractionation model based on ionic potential ratios indicates that Eu3+ was stable during fluid migration and fluorite precipitation. The coexistence of pyrite and Eu3+ in the mineralizing fluids is consistent with low pH and oxygen fugacities near the hematite-magnetite buffer. 相似文献
12.
晴隆锑矿床中萤石的稀土元素特征及其指示意义 总被引：18，自引：0，他引：18
本文系统地研究了黔西南晴隆锑矿床中萤石的稀土元素地球化学,表明不同颜色、不同矿物组合的萤石的稀土元素含量变化较大,但具有固定的REE分配模式,以明显的负Ce异常、富MREE、分配曲线相对平缓为特征;这种配分模式主要是受其晶体化学因素的控制,而与溶液中REE络合物的稳定性关系不大。萤石的稀土元素组成与其矿物共生组合关系不大,但与其颜色关系较密切。萤石的Ce、Eu异常主要是受氧逸度的控制,流体源区的氧逸度较高,矿物沉淀场所的氧逸度相对较低,从而导致该矿中萤石呈明显的负Ce异常,或正或负的Eu异常。晴隆锑矿床形成于开放体系条件下,水/岩反应很可能是导致萤石发生沉淀的主要机制。萤石中的Ca部分来自茅口组灰岩,部分来自大厂层玄武岩;而矿化剂F可能主要来自外部。 相似文献
13.
The Baiyanghe Be–U–Mo deposit is located in the Late Paleozoic Xuemisitan–Kulankazi island arc of the northwestern margin of the Junggar plate, Northwest China. It is the largest Be deposit (2.2 M tons of ore with grades ranging from 0.2% to 1.4%) in Asia. Orebodies in the deposit occur as fractures along contact zones between the Yangzhuang granite porphyry intrusion and Devonian pyroclastic country rocks and within the porphyry itself. Muscovite–fluorite veins are closely associated with the Be–U–Mo mineralization. A new Ar–Ar dating of the muscovite in this study yields a plateau age of 303.0 ± 1.6 Ma, which constrains the timing of the Be–U–Mo mineralization of the deposit. Three stages of fluorite of different colors have been identified at the deposit, with the earliest dark-purple fluorite more closely associated with the mineralization. Microthermometry of fluid inclusions obtained from the three stages of fluorite suggests that the fluorites were precipitated as veins from low temperature (120–150 °C) hydrothermal fluids with salinity ranging from 4.7 to 19.7 wt.% NaCl eqv. Based on the trace elemental concentrations and REE patterns of the fluorite, the style of veining, and the low salinity and low temperature characters of the fluid inclusions, it is suggested that Be and U were most likely transported as fluoride complexes and Mo as hydroxyl complexes. Pb isotopic compositions of the ores and country rocks, as well as O and H isotopic characters of the ore-related muscovite, indicate mixing between magmatic and meteoric waters; both contributed to formation of the ore-forming fluids. Metallic Be, U, and Mo were most likely leached out from the granite porphyry by the fluids. The fluid mixing led to the reduction of U, Mo, and Be and their precipitation at the deposit. 相似文献
14.
The factors determining the REE distribution in natural hydrothermal systems are studied by a numerical experiment. The behavior of REE is examined based on the composition of ore-bearing hydrothermal solutions and the parameters of ore formation processes at different fluorite deposits. These data were obtained in studies of fluid inclusions. Some regularities of the REE behavior during the formation of fluorite deposits have been revealed. It is shown that the REE distribution in fluorites is related mainly to changes in the composition of mineral-producing fluid solution. 相似文献
15.
R. T. Pidgeon A. A. Nemchin G. J. Hitchen 《Contributions to Mineralogy and Petrology》1998,132(3):288-299
Internal structures in zircons from granitoids from the late Archaean Darling Range Batholith show secondary features revealed
by HF etching, which record reconstitution of the zircons and modification of the distribution of trace elements during post
crystallisation cooling of the granitoid. Zircons from the granites commonly contain unzoned to weakly zoned cores surrounded
by rims showing oscillatory zoning which has been modified by recrystallisation. The most striking feature is the development
of high trace element concentration areas found in zircons from a number of granites. These structures range from enhanced
trace element concentrations in primary zones to a single accumulation of most trace elements in one band, about half way
between the outer edge and the centre of the zircon. In any zircon the extent of the concentration of trace elements towards
the formation of a single trace element band appears to be inversely related to the fading and broadening of primary oscillatory
zones in the outer rim. This suggests that the trace element bands formed by migration of trace elements from the outer primary
zones to new concentration sites on an inner set of primary zones. This explanation is supported by the formation of multiple
curved trace element bands that transgress primary zoning and the determination of younger SHRIMP ages on depleted zircon
outer rims compared to remnant primary oscillatory zoned areas of the zircon and unzoned centres. Also observed in some granite
zircons is a finely convoluted zoning which overprints oscillatory zoning in parts of a zoned zircon and in rare cases occurs
throughout the zircon. This structure is explained in terms of secondary migration and reconcentration of trace elements in
curved bands. All structures can be transgressed by generally rounded lobes and patches of low U, weakly nebulously zoned
zircon. This is interpreted as a late stage interaction between the zircon and fluids formed during cooling and crystallisation
of the granitoid, resulting in recrystallisation of affected parts of the zircon with accompanying loss of trace elements
from the zircon.
Received: 6 January 1998 / Accepted: 8 May 1998 相似文献
16.
17.
内蒙古林西萤石矿床稀土元素地球化学特征及其指示意义 总被引：5，自引：0，他引：5
内蒙古林西县萤石矿产资源丰富,已知萤石矿床（点）68处。萤石矿床产出于中生界火山-沉积岩地层中,矿体主要受近 SN 向或 NNE 向断裂破碎带控制。为了研究水头地区萤石矿床的成矿流体来源和成矿机理,文章对矿床稀土元素进行了分析。结果表明萤石和方解石的稀土元素总量（∑REE）为4.37-159μg/g, LREE/HREE比值为0.24-1.80,δEu =0.57-1.60,具弱Ce负异常（0.81-0.98）特征, Y/Ho比值为21-78,平均41。从成矿早阶段到晚阶段,∑REE值及LREE/HREE比值均逐渐减小,晚阶段萤石具有重新活化、重结晶的特征。结合赋矿地层及矿区外围花岗岩体REE特征分析,认为其成矿流体迁移距离较远,稀土元素和成矿元素可能来自下伏高F地体和含Ca赋矿火山-沉积地层,为热液成因-破碎带充填交代型萤石矿床。 相似文献
18.
《International Geology Review》2012,54(4):368-383
Vein-type fluorite deposits in the southern part of the Sierras Pampeanas, Córdoba Province, Argentina, occur mainly hosted by calc-alkaline porphyritic biotite granites, which belong to the Paleozoic, post-tectonic Cerro Aspero batholith. The fluorite veins, of Cretaceous age, occupy steeply dipping, strike-slip regional fault zones, and are composed of fluorite and chalcedony, locally with subordinate amounts of pyrite and, in some cases, coffinite and pitchblende. These veins show typical open-space-filling textures and are closely related to pervasive silicic and argillic alteration of the host granite. Three successive stages of mineralization were distinguished on the basis of vein chronology, REE data, and fluid-inclusion study in fluorite ores. These stages generally display slightly fractionated REE patterns (La/Yb = 1.4 to 14), with REE behavior given by a relatively stronger LREE fractionation with respect to HREE. The REE composition of the fluids responsible for fluorite deposition was largely controlled by differential mobility of the REE during the silicic or argillic alteration of the host granite. Preferential leaching of HREE over LREE occurred during both alteration types, but in the argillic alteration the LREE were practically not removed. The total homogenization of primary-like aqueous inclusions took place invariably in the liquid phase at temperatures ranging from 187°C to 103°C, with concentrations of values around 160°C, 136°C, and 116°C (stages I, II, and III, respectively), defining a clear trend of fluid cooling. This cooling is accompanied by large changes in the fO2 of the fluid, from oxidizing to reducing, as inferred from the Eu/Eu? ratios and the mineral assemblage (pyrite, pitchblende, and coffinite). The three stages of fluorite deposition exhibit temperatures of ice melting within the interval from ?0.3°C to +0.4° C, indicating that the mineralizing fluids were exclusively aqueous and highly dilute. No evidence of fluid mixing or boiling was found. The fluid-inclusion data suggest that the proposed three stages of mineralization probably were the result of a single hydrothermal event, and strongly support a single, uniform fluid reservoir for the ore-forming solutions; evidently, the latter were heated meteoric waters rather than fluids generated in deep-seated environments within the crust. 相似文献
19.
Mohamed Abdel-Moneim Mohamed 《Arabian Journal of Geosciences》2012,5(4):697-712
The Neoproterozoic pluton of Gabal Gharib granite Eastern Desert of Egypt is intruded in subduction-related calc-alkaline granitic rocks of granodiorite to adamellite composition. A zone of metasomatized granite was developed along the contacts at the expense of the calc-alkaline granite. The granite of Gabal Gharib is hypersolvus, composed mainly of orthoclase-microperthite, quartz, and interstitial arfvedsonite. Fluorite, zircon, ilmenite, allanite, and astrophyllite are the main accessories. Pegmatite pods as well as miarolitic cavities (mineral-lined cavities) are common and ranging in size from a few millimeters to 50?cm. Rare-metal minerals such as columbite, cassiterite, and fluorite have been identified from the miarolitic cavities. Geochemical studies revealed that Gabal Gharib granite is a highly fractionated granite, homogeneous in composition, with high contents of SiO2, and alkalis, high Ga/Al, and Fe/Mg ratios, and low concentrations of Al, Mg, and CaO relative to granodiorite?Cadamellite country rocks. Gabal Gharib granite is metaluminous to peralkaline with ASI (0.94?C1.07). Trace element characteristics of Gabal Gharib granite include abundances of Rb, Nb, Ta, Sn, Th, U, Y, Ga, Zn, rare earth elements (REEs, except Eu), and F, and depletion in Sr, and Ba relative to granodiorite?Cadamellite country rocks. It has the geochemical characteristic of anorogenic A-type granite. The uniform trends of differentiation, normal REE distribution patterns, and low calculated tetrad effects of REE (<0.2) indicate that the effect of post-magmatic subsolidus processes were minimal in the studied granite. Fluid inclusions were studied in quartz crystals from Gabal Gharib granite, quartz pods, and metasomatized granite. The study revealed the presence of high-temperature (480?C550°C), high-salinity (19.45?C39.13?wt.% NaCl eq.) primary inclusions in both metasomatized and rare-metal granites coexisting with melt inclusions and medium-temperature (350?C450°C), medium-salinity (10?C16?wt.% NaCl esq.) aqueous inclusions coexisting hydrocarbon-bearing inclusions. Hydrocarbon is represented by magmatic CH4 in Gabal Gharib granite, while heavier aliphatic compounds may be present in quartz pods. Melt inclusions with temperatures of homogenization >600°C were also reported. Petrographic, geochemical, and fluid inclusion studies constrain that the peralkaline anorogenic granite of Gabal Gharib was derived from highly evolved magma probably originated by fractional crystallization of mantle source. 相似文献
20.
Mohamed F. Raslan 《Resource Geology》2009,59(1):99-105
Uraniferous iron grains occur in some radioactive granite plutons in the Eastern Desert of Egypt. Modal analysis of these grains indicates that weight abundance of uraniferous grains amounts to 17.50%, 18.00% and 26.00% of the total accessory heavy minerals of the uranium-mineralized samples of Gabal Gattar, El Missikat and El Erediya, respectively. These grains are mainly restricted to shear zones associated with strong hematitization, and occur either as fracture fillings or as interstitial grains among the main rock-forming minerals. Uraniferous iron grains are mainly composed of uranophane and β-uranophane coated and stained with limonite. These grains represent the main radioactive minerals in addition to the bright canary yellow to yellow uranophane and β-uranophane mineral grains. The data obtained on scanning electron microscopy and electron microprobe analysis confirm the abundance of iron in the darker colored varieties with respect to the light colored varieties. This mode of occurrence of the uranium minerals requires special consideration during mineral processing by physical means. 相似文献