Na-Metasomatism and Uranium Mineralization during a Two-Stage Albitization at Kitongo, Northern Cameroon: Structural and Geochemical Evidence

Mapping and documentation of lithological varieties and their corresponding geochemistry at the Kitongo uranium mineralization were concerned. The Kitongo U occurrence is hosted by granitic rocks that include interleaved sequences of metasedimentary and metavolcanic rocks of the collectively termed Poli Group. U-mineralization and Na-metasomatism are related and structurally controlled. The most promising uraniferous bodies are intimately related to intersections between the ductile ENE-trending faults and the brittle conjugate R' faults postdating the shearing event. The con- centration of uranium at fault intersections rather than along individual faults suggests that these zones that are dilatational in nature were also highly permeable and therefore the hydrothermal fluids ponded there could readily precipitate U therein. A two-stage albitization has altered the foliated granitic host rock and the second albitization that has over-printed the first one is more effective at fault intersections. Whole rock geochemistry was performed by using ICP-MS and ICP-AES respectively for major oxides, trace and REE. The U-bearing rock suite exhibits restricted range in SiO2 concentration (62.89% - 70.91%) and Al2O3 (13.16% - 18.59%) and it is poor in MgO (0.02% - 1.03%), CaO (0.24% - 1.88%) and K2O (0.08% - 5.32%). The mineralized rocks are however comparatively richer in Na2O (4.33% - 10.92%) compared to their barren counterparts. The host granite and associated granodioritic rocks in the area are weakly metaluminous, peralkaline, and are calc-alkaline. They are moderately to strongly fractionated and have tholeiitic and shoshonitic affinities with moderate to high HFSE (high field strength elements) and LILE (large ion lithophile elements) enrichment. The Rb/Sr, Rb/Ba and Sr/Ba ratios are 0.31, 0.14 and 1.48, respectively. U content in the mineralized granite is up to 651 ppm while the non-mineralized rock has only 2.4 ppm U. The REE patterns of the granite show LREE enrichment and strong Eu negative anomalies (Eu/Eu* = 0.03 to 0.48). The main mineralization stage characterized by local U, Na, Pb, Zn, Ga, Hf, Sr, Fe, Al, P and Zr enrichments is related to the second albitization event and could probably be associated in time with the calcite-uranium stage. The identification of fault segments favorable for uranium mineralization in northern Cameroon (Poli area) is important for understanding the genesis of hydrothermal ore deposits within continental strike-slip faults and therefore has great implications for exploration strategies.

Low temperature albitization in Caino-Mesozoic reservoir sandstones from North Tarim, and a discussion on the fluid origin

CAJNOZOIC and Mesozoic in North Tarim are predominantly a set of terrestrial detrital formations. In thereservoir sandstones in the area, albite is one of the widely developed authigenic mineral. Micro-structural evidence shows that diagenetic albite occurs as euhedral crystals in the pore, and replaces feldsparand other detritus along cleavage and micro-crack. EPMA analyzing found that some of the alteration product has a chemical composition between purealbite and the replaced detrital feldspar. For example, composition of replaced alkali feldspar is betweenmicrocline and albite, and content of altered plagioclase decreases continuously. This has been regardedas direct evidence for fluid replacement, for feldspar crystallized from solution or magma is usually withfixed chemical composition. Taking alkali feldspar as an example, although Kf and Ab forming completeisomorphous admixture in high temperature, they exsolved out as two relative pure phases while temperature decreases.

40Ar-39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East-Central China and Its Significance

40Ar-39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan-Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle-lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large-scale lithosphere delamination and strong sinistral strike-slip movement of the Tancheng Lujiang fault zone. The copper, molybdenum and gold deposit system in the middle-lower Yangtze River region was formed during the stress transition period of the eastern China continent.

Hydrothermal Alteration Zoning and Kinetic Process of Mineral-Water Interactions

This study reports the kinetic experimental results of albite in water and inKCl solution at 22 MPa in the temperature range of 25 to 400 deg C. Kinetic experiments have beencarried out in an open flow-through reaction system (packed bed reactor). Albite dissolution isalways incongruent in water at most temperatures, but becomes congruent at 300 deg C (close to thecritical point 374 deg C). At temperatures from 25 to 300 deg C, the incongruent dissolution ofalbite is reflected by the fact that sodium and aluminum are easily dissolved into water; from 300to 400 deg C it is reflected by silicon being more easily dissolved in water than Al and Na. Maximumalbite dissolution rates in the flow hydrothermal systems have been repeatedly observed at 300 degC, independent of flow rates. The kinetic experiments of albite dissolution in a KCl aqueoussolution (0.1 mol KCl) indicate that the dissolution rate of albite increases with increasingtemperature. Maximum silicon release rates of albite have been observed at 400 deg C, while maximumaluminum release rates of albite at 374 deg C. The reaction rates of albite also depend on thepotassium concentration in the aqueous solution. These results can be used to interpret themechanism for forming hydrothermal alteration. The kinetic experiments of mineral-aqueous solutionsinteractions in the hydrothermal system from 25 to 400 deg C and at 22 MPa indicate that theformation of the feldspar-mica-kaolinite zoning occurring in some ore deposits may depend not onlyon the mineral stability but also on the kinetics of feldspar hydration, which is affected by thewater property variation when crossing the critical point.

Petrological Implication of the Albite Rims in the Felsic Gneisses of the Fuping Complex

The albite rim is present in most felsic gneisses of the Fuping Complex. The presence of the rim indicates the coexistence of plagioclase and K-feldspar in the rock. The rim is formed immediately after the myrmekite, and both textures were derived from the alteration of K-feldspar. The difference is that that there is no quartz present in the rim, and the rim is nearly albite and the anorthite content of the rim plagioclase is substantially lower than that of the myrmekite plagioclase. Formed at 400- 500~C the albite rim was derived from the K-feldspar composition adjustment in the late or post- magmatism stage. As the temperature decreased, the equilibrium between K-feldspar and plagioclase could be maintained, and reactions between the minerals occurred. The leucocratic veins in the complex show distinguished magma or migmatitic characteristics. The rim might form in the late magma or deuteric stage. The formation of the rim implies obvious granitic magmaor melt-injection activity. Typical metamorphic rocks cannot produce the rims. Anatexis after medium-high grade metamorphism might be subordinate. If present, the anatexis is water-present, but the rim texture cannot be taken as the symbol of anatexis.

Geophysical Mapping, Geochemical Evidence and Mineralogy for Nuweibi Rare Metal Albite Granite, Eastern Desert, Egypt

The present study aims to shed light on the rare metals of Nuweibiareaalbite granite in the Eastern Desert through the chemical analyses of the two types of fine-grained albite granite (FAG) and medium-grained albite granite (MAG) in addition to mineralogical studies as well as ground spectrometric survey and aeromagnetic mapping. On the basis of ground spectrometric measurements K, eUand eTh distribution maps were obtained. The concentration of K, U and Th content shows maxima (4.5%, 13 ppm and 27 ppm on average, respectively) in the FAG, and (4.5%, 10 ppm and 35 ppm on average) in the MAG. The eU/eTh ratio significantly increases in FAG with higher magma differentiation than MAG reaching 0.63. This paper uses magnetic geophysical methods to investigate geometry and sense of motion across the Nuweibi area. The interpreted structures from the magnetic maps are characterized by two main intersecting sets of NW-SE and NE-SW trending faults in addition to other three minor faults that trend in N-S, NNW-SSE and ENE-WSW directions. The NW-SE trending faults represent the recent sets in the study area where they are dissected and displaced by the other old faults. The Werner depth map shows the interface depths of the granite and basement rocks that extend to great depths ranging from 10 to 380 m. FAG is extended underneath most of the surrounding schist rocks because of their attributed low magnetic intensity that confirmed also with drilling. Microscope and Microprobe analyses indicated that the most important radioactive minerals include uranothorite, thorite, zircon, and monazite. Columbite group minerals represent the most common Nb-Ta host in Nuweibi-albite granites that contain significant levels of Ta (up to 65.4 wt. % Ta2O5) and Nb (up to 60 wt. % Nb2O5), with Ta/(Ta+Nb) ratio ranging from 0.17 to 0.84. Columbite group minerals are represented mostly by columbite-(Mn) and tantalite-(Mn), with Mn/(Mn+Fe) ratio ranging from 0.42 to 0.89. Ixiolite, wodgnite and tapiolite-(Mn) were found only in the FAG indicating the final stages of the evolution of parental granitic magma. The U-Th and U-K variation diagrams suggested that magmatic processes controlled the distribution of these elements. The Scanning Electron-microprobe analyses reveal variable compositions and extents between the MAG and FAG in the Nb, Ta-Ti, Sn-Fe, Mn triangular plot. It is worthy to be noted that because of the higher Ta/Nb ratio in the tapiolite-Mn and ixiolite of FAG in comparison with the coexisting Mn-columbite in the MAG, levels of HfO2 greater than 15% and even attaining 23%, characterized the hafnium zircon in the Nwueibialbite-enriched facies. There is a close correlation between Hf/(Hf + Zr) and Ta/(Nb + Ta) which seems mainly associated with the FAG.

Insights into the floatability between spodumene and albite from crystal chemistry standpoint

Spodumene is a silicate mineral rich in lithium.However,the gangue mineral,albite has similar crystal chemical structure and composition to spodumene.In this work,the density functional theory(DFT)calculation was taken to research the floatability from the perspective of crystal chemistry.And contact angle test and reagent adsorption test were used to support the simulation results.In addition,the weighted total density of broken bonds is proposed for the first time to judge the generation probability of cleavage surface.The DFT calculation results display that the Na and Al sites on the albite surface are the adsorption sites of water molecules.While the water molecules only bond with Al atom on the surface of spodumene and each Al site can adsorb only one water molecule.Thus,the wetting effect of water molecules on the albite surface is stronger than that of spodumene.This is consistent with the result of contact angle.In sodium oleate system,the oleic acid anion is adsorbed on the spodumene surface in form of a multicomponent ring while the albite is a single ring.Theoretically,oleic acid anion can be strongly adsorbed on the surface of spodumene and albite under vacuum.The adsorption strength of spodumene is higher than that of albite.However,on hydrated surface,the adsorption strength of oleic acid anion on mineral surface is greatly reduced due to the interaction between water molecules and metal site on mineral surface.Thus,spodumene and albite are hard to float without external activated ions in sodium oleate system.

A Study of Ferrospheres in the Coal Fly Ash

Coal fly ash is an industrial by-product, produced from coal combustion in thermal power plants. It is the most complex anthropogenic materials, which consists of combination of minerals originated from different sources. Coal fly ash and its byproduct has become an environmental concern over the World. Therefore, there is a pressing and ongoing need to investigate the structures and some properties of coal fly ash and develop new recycling methods for it. The amount of silica, aluminum, calcium, potassium, magnesium, sodium, titanium and phosphorus oxides contained in power plant fly ash was determined by X-ray flouresecence (XRF) analysis. Concentration of heavy metals in fly ash was in sequence of Pb > Zn > Cu > Cr > Ni. As results of Scanning Electron Microscopy (SEM), except for porous and hollow particles, large and small microspheres were observed. These particles are classified as ferrospheres. X-ray diffraction (XRD) analysis show that fly ash consists of the following crystal phases: quartz, albite, anorthite and hematite.

Flotation separation of spodumene and albite with activation of calcium ion hydrolysate components

It is difficult to separate spodumene and albite by flotation with calcium ion as activator.In this study,microflotation experiment,solution chemistry calculation,density functional theory(DFT)calculation and X-ray photoelectron spectroscopy(XPS)analysis were conducted to investigate the effect mechanism of c alcium hydrolysate on the flotation separation of spodumene and albite.Results show that the weak interaction intensity of Ca^(2+)with O atoms on the mineral surface makes it difficult to activate minerals effectively.The O atom in the hydroxyl group of Ca(OH)^(+)and Ca(OH)_(2)can be strongly bonded with Al atom on the mineral surface,which greatly improves the adsorption strength.After the activation of Ca(OH)^(+),the adsorption forms of collectors on the surface of spodumene and albite are quite different,and the adsorption intensity on the surface of spodumene is higher,which is conducive to the flotation separation of spodumene and albite.After the action of Ca(OH)_(2),the adsorption of the collector on the albite surface is stronger than that of spodumene,which is not conducive to the flotation separation of the two minerals.By adjusting the initial concentration of calcium ions and pulp pH,Ca(OH)^(+)is the main active component,which is the key to improve the separation effect of spodumene and albite.

Experimental studies of interaction between water and albite melts

On the basis of FTIR and Raman spectra studies on hydrous albite glasses, it is found that there exist two water solubility mechanisms in albite melts simultaneously. On the one hand, water interacts with Al -O°-Al to produce the Q3 Al-OH, leading to depolymerization, and this results in the appearance of 4500 cm(1 in FTIR spectra and 900 cm(1 in Raman spectra. On the other hand, the exchange of H+ in water with Na+ in albite melt as charge-balancing cation occurs at the same time. In the initial stage, the production of Al -OH is the dominant solubility mechanism, at the stage of higher water contents, the exchange of H+ with Na+ becomes the important dissolution mechanism. The dissolution of water into albite melt can be expressed as H2O+ 3NaAlSi3O8 = 2NaAl(OH)Si3O7.5 +HAlSi3O8 +NaOH.

Non-Oxidative Methane Conversion Using Lead- and Iron-Modified Albite Catalysts in Fixed-Bed Reactor

Raw and modified albite catalysts, including Pb/Atbite and Fe/Albite catalysts, have been investigated for methane conversion to C2 hydrocarbons under non-oxidative conditions. Introduction of Pb to albite improved the activity and selectivity to non-coke products. Based on characterization, it was found that Pb entered into the alkali and alkaline-earth metal sites of albite, while partial Fedoped in the tetrahedron sites and the other loaded on the surface of albite. At the reaction temperature of 1073 K, methane gas hourly space velocity （GHSV） of 2 L.gcat-1·h-1, catalyst dosage of 0.25 g （300 mesh）, the methane conversion catalyzed by raw albite in the fixed-bed micro reactor exhibited a methane conversion of 3.32%. Notably, introducing a Pb content of 3.4 wt% into albite greatly enhanced the conversion of methane up to 8.19%, and the selectivity of C2 hydrocarbons reached 99% without any coke under the same reaction conditions. While Fe-doping could weakly heighten the methane conversion to 3.97%, and coke was formed. Thus, a comparison of Pb/Albite and Fe/Albite catalysts demonstrates that the catalytic activity of albite is mainly decided by alkali and alkaline-earth metal sites, and lead-modification can effectively improve the catalytic activity of albite.