K2O P2O5 Research Articles

Geochronology and geochemistry of a Neoproterozoic syn-tectonic granitic pluton in the Gari-Gombo area, East Cameroun: Implications for petrogenesis and tectonic evolution

Granites are widespread in many Precambrian orogenic belts worldwide; therefore, they can provide insights into orogenic processes and associated magmatism. Zircon UPb age, monazite Th-U-total Pb age and whole-rock geochemical data for a granite pluton from the Gari-Gombo area in the Adamawa-Yade domain of the Central African Fold Belt (CAFB) in East Cameroon are presented. The granite is composed dominantly of perthitic K-feldspars, quartz, plagioclase and minor biotite with accessory monazite, apatite and zircon. LA-ICP-MS zircon UPb dating yielded an age at ca 631–620 Ma, which is interpreted as age of emplacement that coincides with the onset of D2 Pan-African deformation. Monazite grains in Gari-Gombo granite follow strictly the huttonite substitution trend in Th + U vs Si coordinates. Monazites give consistent Neoproterozoic ages of 630 ± 4 Ma and 602 ± 4 Ma, indicating that growth history and crystallization age of monazites also correlate well with the Pan-African plutonism and granulite facies metamorphism (ca 614–600 Ma) in the Gari-Gombo area. The Gari-Gombo pluton samples show high-K calc-alkaline magnesian, slightly peraluminous signature, high SiO2 (70.16–78.80 wt%), K2O (4.39–5.38 wt%), and Rb (165–248 ppm), and low P2O5 ≤ 0.01 wt% and Sr (146–222 ppm) contents. They have highly-fractionated REE pattern ((La/Yb)N = 6.17–148.18), moderately Eu negative anomalies (Eu/Eu* = 0.53–0.93) and the obviously Nb and Ti negative anomalies. These geochemical features suggest that the Gari-Gombo pluton is a highly fractionated I-type granite generated by partial melting of older meta-igneous materials at middle to lower crustal levels. The 2.9 and 0.95 Ga inherited zircon grains identified within the studied granites further confirm the existence of ancient crust in this region.

Study on topsoil chemical characteristics in Bao Thang district, Lao Cai province for agricultural development

Researching some chemical characteristics of topsoil in Bao Thang district, Lao Cai province to serve the management, planning, and reasonable use of agricultural land resources is very necessary, especially for identifying areas for growing specialty crops to convert crop purposes and improving local people’s lives. Result analysis of pHsoil, organic carbon (OC), organic matter (OM), major elements and trace elements from 49 topsoil samples taken at depths from 0÷20 cm on different formations in Bao Thang district, Lao Cai province shows that topsoil in Bao Thang district has pH in the slightly acidic to neutral soil group, OM and OC in moderate concentrations. The chemical composition of soil samples shows a relationship with bedrock. The geochemical characteristics of topsoils are high Fe2O3, poor to rich K2O and rich P2O5. Some trace elements in the topsoil of different fomations have lower or equivalent concentrations with those in the world’s soil and are consistent with the safety threshold of National technical regulation on soil quality (QCVN 03:2023/BTNMT), except Cr and Zn. This issue needs to be paid attention to during cultivation and agricultural production.

Petrogenesis and Geochronology of A1-Type Rhyolites in the Late Late Triassic of the East Kunlun Orogenic Belt: Constraints on the End of the Paleo-Tethys Orogenic Event

The rhyolites which are widely exposed to the northern margin of the East Kunlun orogenic belt were chosen as a research object to discern the post-orogenic tectonic evolution of the East Kunlun orogenic belt and reconstruct the post-collision orogenic processes of the Buqingshan- A’nyemaqen Ocean. We researched zircon U-Pb ages and geochemistry characteristics of the Late Triassic rhyolites in the eastern segment of the East Kunlun Orogenic Belt in the northern Tibetan Plateau. Zircon U-Pb dating yields coeval ages of 200.4 ± 1.4 Ma and 202.8 ± 1.2 Ma for the Keri rhyolites of the East Kunlun Orogenic Belt, indicating that the volcanic rocks were formed in the Late Triassic Rhaetian–Early Jurassic Hettangian. The Keri rhyolite is a product of the late magmatism of the Elashan Formation volcanic rocks. The rhyolites include rhyolitic brecciated tuff lavas and rhyolitic tuff lavas. The rhyolites are peraluminous and are high-K calc-alkaline, with high contents of SiO2, K2O, TFe2O3, and low P2O5 contents. The A/CNK ratios range from 0.97 to 1.09, indicating that the rhyolites are metaluminous to weakly peraluminous. The chondrite-normalized rare earth element (REE) distribution shows a significant negative Eu anomaly and low total REE concentrations. All samples are depleted in high field strength elements (HFSEs, e.g., Eu, Sr, Ti, and P), heavy rare earth elements (HREEs), and enriched in large ion lithophile elements (LILEs, e.g., Rb, Zr, Nd, Th, and U) and light rare earth elements (LREEs). The Keri rhyolite has the characteristics of A1-type magmatic rock, formed in an anorogenic environment after the closure of the Paleo-Tethys Ocean, and was the product of late magmatism in the Elashan Formation volcanic rocks.

Discovery of Variscan orogenic peridotites in the Pelvoux Massif (Western Alps, France)

Small bodies of mantle-derived peridotites and other ultramafic rocks are commonly found in exhumed lower crustal units of collisional orogens. They provide a direct record of the complex evolution of the upper mantle before and during an orogeny, and are therefore key markers of the geodynamic evolution of an orogen. We report here the discovery of such mantle-derived peridotites, which occur as fragmented enclaves in migmatites of the high-grade Variscan lower crust exposed in the Pelvoux Massif (external Western Alps). A wide petrographic diversity has been observed, from very fertile, garnet-bearing lherzolites, to more depleted spinel/chromite-bearing harzburgites. Thermobarometric calculations on a garnet lherzolite indicate an initial stage at 3.0–4.0 GPa and 970–1140 °C, followed by exhumation to 0.8–1.3 GPa and 800–850 °C, while the harzburgites do not show any evidence of equilibration in the garnet field. Petrological observations, whole-rock geochemistry and in situ mineral compositions suggest the peridotites have undergone a complex history prior to their incorporation in the lower crust during the Variscan Orogeny. They derive from a refractory mantle, which has experienced variable degrees of melt depletion, and has then been extensively refertilized. Cryptic metasomatism is observed in all samples. It is characterized by an enrichment in large-ion lithophile elements (LILE, in particular Cs, Rb, U and Pb) relative to high field strength elements (HFSE), in particular Nb and Ta. This cryptic metasomatism is presumably related to percolation of subduction-related fluids or melts in the mantle. In addition, modal metasomatism occurred in some samples, where crystallization of phlogopite, pargasite, chromite and apatite has been observed. This modal metasomatism resulted in significant enrichment in K2O, P2O5 and Cr2O3 of the bulk rock, together with a strong enrichment in incompatible LREE relative to HREE. These geochemical characteristics are strikingly similar to that of syn-collisional, Mg–Cr–LILE rich mantle-derived (ultra)-potassic magmas such as durbachites and vaugnerites, which are ubiquitous in the Variscan metamorphic allochthons of Massif Central, external Alps, Vosges and Bohemian Massif. We therefore suggest that this metasomatism results from dynamic percolation of the peridotites by K2O–P2O5–Cr2O3-rich melts from which the durbachites and vaugnerites are primarily derived. These geochemical characteristics are in line with whole-rock Nd isotopic compositions, which indicate enrichment of the mantle by a continental crust component, presumably related to Variscan subductions. This evolution is consistent with that of other Variscan peridotites in the Eastern Alps (Ulten) and the Bohemian Massif, where multiple metasomatic episodes related to melts or fluids released in Variscan subduction zones have been documented.

Synthesis and characterization of newly developed phosphate-based glasses through experimental gamma-ray and neutron spectroscopy methods: Transmission and dose rates

In this study, four new phosphate-based glasses with the compositions of CaO–Na2O–K2O–P2O5 (PN system), CaO–Na2O–K2O–Al2O3–P2O5 (PA system) and CaO–Na2O–K2O–Al2O3–SiO2–P2O5 (PS system) were synthesized and characterized through experimental gamma-ray and neutron spectroscopy methods. Glass densities were then measured experimentally and evaluated theoretically. Next, a high purity Germanium (HPGe) detector was used for determining the fundamental gamma-ray transmission parameters in 35.4–383 keV gamma-ray energies emitted from 133Ba source (Radioactivity: 3Ci). Additionally, the experimental setup was used to determine the equivalent dose (EAD) to get a better knowledge of fast neutron attenuation. Our findings indicate that experimental gamma-ray transmission measurements are consistent with standard theoretical data (EpiXS). Consequently, PA10 was shown to have higher gamma-ray and neutron attenuation capabilities when compared to the other glass samples studied. Our outcomes showed that increasing the molar contribution of Al2O3 to the phosphate-based glasses increased not only their transparency but also their gamma-ray and neutron attenuation capacities. It can be concluded that substituting Al2O3 for P2O5 is a functional and monotonic tool for improving the optical, gamma-ray, and neutron attenuation of phosphate-based glasses, which are being evaluated as prospective shielding materials for medical and industrial radiation facilities.

Petrology and Geochemistry of Rocks of Ishiagu and Environs Southeastern Nigeria Using Ed-Xrf Method

Geochemistry of rocks of Ishiagu area was carried out using Energy Dispersive X-Ray fluorescence (ED-XRF) method. Twelve samples were analyzed and their geochemical properties determined using Excel-Software. Geological mapping reveals that basalts, dolerites and diorites emplaced in shale and mudrock country hosts are the main lithological units occurring in the area. They have silica content of 40.4–49.2wt.%, indicating they are basic-ultrabasic in character. The dolerite and diorite contain average plagioclase (An70-17.4vol.%), hematite 26.29vol.%, showing enrichment in ferromagnesian minerals and depletion in quartz. The Na2O and K2O averaged 1.22wt.% and 1.46wt.% respectively, indicating depletion in alkali, thus corroborating their basic–ultrabasic property. The TiO2 value is 3.6wt. %, indicating oceanic magma derivation. The industrial metals Pb, Cu, Ni and Zn were relatively similar with average values of 37.13, 23.96, 23.69, and 20.08ppm respectively, showing common protolith. The diorite and dolerite are enriched in trace elements Zr, Sr, with average concentration of 172.49, 109.73ppm, and relatively depleted in As and Au with values of 0.04 and 0.03ppm respectively. Petrogenetic analyses using ternary diagram TiO2–K2O–P2O5 for discriminating magma type, the dolerites and diorites all plot in continental basaltic field. In the AFM, and P2O5 versus Zr plots all the dolerites and diorites fall in the tholeiitic field, corroborating that they originated from tholeiitic basaltic magma, probably derived from lower crust/upper mantle. In the Na2O/Al2O3 versus K2O/Al2O3 diagram the dolerites and diorites all plot in the igneous field, the shale plot in metasedimentary field, while the ironstone fall on the boundary between igneous and metasedimentary fields indicating hybrid provenance.

Evaluation of the physical, structural, thermal, and advanced radiation absorption characteristics of SiO2–Na2O–K2O–P2O5–CaO bioactive glasses

We report herein an evaluation of the physical, structural, thermal, advanced photon energy absorption, and fast neutron removal characteristics of a series of bioactive glasses having the compositions 20SiO2-7.5Na2O-7.5K2O-(65–x)P2O5-xCaO, where x = 2.5, 5.0, 7.5, and 10.0 mol.%. X-ray diffraction (XRD) patterns confirmed the amorphous nature of these phosphosilicate glass systems fabricated by the melt-quench technique. To confirm the in vitro bioactivity of the prepared glasses, powdered samples of each composition were compressed into pellets and then soaked in simulated body fluid (SBF) at 37 ± 0.5 °C for 28 days. Soaked samples were investigated by means of XRD, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS/EDX). Thermo-gravimetric and differential thermal analysis (TG-DTA) was applied to determine the glass transition temperature (Tg) and crystallization temperature (Tc) for each glass sample. Fourier-transform infrared (FTIR) measurements were performed in the range 4000–400 cm−1, and showed the bending and stretching motions of different groups and the presence of CO2 and OH− groups in the glasses. Radiation absorption properties, such as mass energy absorption coefficient (μen/ρ), kinetic energy released per unit mass (KERMA) relative to air (ҠR), and mean free path values have been obtained for the bioactive glasses and compared with those of registered 45S5 Bioglass®. The simultaneous variation of mass energy absorption and mass attenuation values with photon energy has been explored to visualize the difference between absorption and attenuation. Linear attenuation coefficients for the present glass samples have been measured at photon energies of 511, 662, 1173, and 1332 keV in narrow-beam transmission geometry, and were in good agreement with theoretical results (error < 2 %). Further, detailed comparative analysis of energy absorption build-up factor (EABF) values for the glass samples has been conducted using two software tools, namely Photon Shielding and Dosimetry (PSD) and EXABCal, as well as on the basis of equivalent atomic number (Zeq) and effective atomic number (Zeff). We also attempted to calculate effective removal cross-sections (∑R) in order to evaluate the neutron absorption performances of these glass samples. The present detailed analysis shows that glass sample S4 with 10 mol.% CaO exhibits the most promising radiation absorption properties, resembling those of 45S5 Bioglass®.

Geochemistry of Granites from Chail Group of Garhwal Region, Lesser Himalaya, NW India

Paleoproterozoic granites are well exposed in the Chail group of Garhwal region, Lesser Himalaya crystalline sequences (LCHS). These granites are less studied in terms of geochemical classification and tectonic settings. In the present work, we carried out the geochemical analysis of granites of the Chail group from the Chirbatiya-Khal and Ghuttu areas. All the samples have high SiO2 (73.24 ̶79.1 wt %), Al2O3 (11.2 ̶12.95 wt %), K2O (3.8 ̶5.9 wt %) and low P2O5 (0.11 ̶0.24 wt %), CaO (0.21 ̶1.02 wt %), and Na2O (2.2-3.03 wt %; exceptionally low in one sample, that is 0.009 wt %) contents. The A/CNK values for the samples are range from 1.19 to 2.91, characteristic of S-type granites. REE patterns for these granites are moderately fractionated with an average (La/Yb)N ̴8.21 and europium anomaly (Eu/Eu*) ̴0.15. The tectonic settings of the studied granite suggest that they are formed in syn-collision tectonic environments.

English

Coarse rutile with some grains exceeding 32 mm was recovered from regolith excavated from three pits (ABC) at Ebensuk. The rutile concentration ranges from 2.53 kg/m3 of regolith material in Pit C to 2.83 kg/m3 in Pit B with an average of 2.66 kg/m3. The rutile is black, longitudinally striated, with a metallic to adamantine luster and hard. Results of grain size (Z) analysis show that the rutile crystals range in size from 4mm to Z≥32 mm. The grains are predominantly concentrated in the 16≤Z 96 wt%, and subordinate Fe2O (2.2-3.1 wt%), and minor amounts of Al2O3, SO3, K2O P2O5 and Mn2O3 for all the samples analyzed, and meets international specifications for economic rutile ores. The rutile must have been derived through weathering of the underlying gneisses and their coarse nature is probably indicative of a possible source from granite pegmatite veins occurring in the gneisses outcropping in the study area. Key words: Coarse rutile, geochemistry, high quality, regolith, grain size.

Reaction Sintering of Bioceramic Based on Substituted Calcium Phosphates CaMPO4 (M = K, Na)

The synthesis of double phosphates based on calcium and alkali metals from different two-phase mixtures was studied. The phase relationships in the CaO–K2O–P2O5 and CaO–Na2O–P2O5 system were clarified, especially the phase transition temperature in potassium rhenanite CaKPO4. It was shown that some compounds that are mentioned in the literature, in particular, CaK2P2O7, CaNa2P2O7, CaK4(PO4)2, and CaNa4(PO4)2, cannot be obtained at 1000–1200°C at normal pressure. The densification and recrystallization were investigated during the reaction sintering of selected two-phase mixtures. Reaction sintering of a mixture of Ca3(PO4)2 and CaK4(PO4)2 gives CaKРO4 ceramic with a density of 78% (linear shrinkage of the sample is 5%); when sintering a mixture of K2CO3 and Ca2P2O7, the density of ceramic was 62% with a linear shrinkage of 15%. The reaction sintering of sodium-containing mixtures made it possible to obtain dense ceramics (density above 90%, linear shrinkage more than 6.5%) from a mixture of CaNa4(PO4)2 and Ca3(PO4)2. The experimental features of the reaction sintering of calcium and potassium/sodium double phosphates are discussed from the point of view of volume change during the course of the reaction. Another aspect that determines the density and microstructure of ceramics is the phase transformation of α → β in alkali metal rhenanites CаMPO4.

Genesis and timing of the Sungai Lembing tin deposit in Pahang, East Malaysia: Constraints from LA–ICP–MS zircon and cassiterite U–Pb dating, geochemical compositions and Sr–Nd–Hf isotopes

The Sungai Lembing tin (Sn) deposit is one of the largest primary Sn deposits in Malaysia, and is a typical hydrothermal vein-type deposit with strong spatial and genetic relationship with the underlying granites. In-situ LA-ICP-MS cassiterite U-Pb dating of the Sn-bearing polymetallic sulfide stockworks yields a weighted average age of 264.2 ± 2.0 Ma, consistent to the zircon U-Pb ages (ca. 260.3–263.0 Ma) for the granites there, showing that the Late Permian mineralization was co-magmatic. The ore-related granites are featured by high SiO2, Al2O3, Na2O, K2O, and low P2O5 contents, with low A/CNK ratios, indicating that these granites are peraluminous I-type high-K calc-alkaline. These granites are enriched in Rb, U, Nd, Zr, Hf and light rare earth elements (LREEs), and relatively depleted in Ba, Nb, Sr, P, Ti and heavy rare earth elements (HREEs), accompanied by negative Eu anomalies. The relatively low whole-rock initial 87Sr/86Sr ratios (0.704199–0.708692), moderately high εNd(t) (−5.30 to −1.88), and old two- stages Nd model ages (1.05–1.28 Ga), together with the negative zircon εHf(t) (−3.2 to −0.3) and old two-stages Hf model ages (1.29–1.48 Ga), indicate that the granites were sourced from the magma generated by the partial melting of Proterozoic meta-igneous rocks of the Indochina Block. The extensive emplacement of Permian granites and Sn mineralization in the Eastern Granite Belt of Peninsular Malaysia may have been resulted from the east-dipping subduction of the Paleotethys beneath the western Indochina Block.

Study of the Non-Isothermal Crystallization Kinetics of Lithium Disilicate Glass Ceramic

The glass ceramic with the crystals of lithium disilicate Li2O · 2SiO2 (LS2) as the main crystal phase is one of the prospective materials in the field of restorative dentistry. In this study, the crystallization kinetics of LS2 glass ceramic obtained from the base glass of the system SiO2–Li2O–Al2O3–K2O–P2O5 were investigated by the non-isothermal method using differential thermal analysis at four different heating rates. The DTA curves showed different exothermic crystallization peaks over the temperature ranges of 645–683 and 807–845°C. The lithium metasilicate, Li2O · SiO2 (LS), and the lithium disilicate, crystallized over these respective temperature ranges, was established by XRD technique. The crystallization kinetic parameters were calculated by the Kissinger plot and Augis-Bennett equations for non-isothermal analysis. The calculated activation energy of crystal growth, EC1= 236 kJ/mol, EC2 = 340 kJ/mol, and the Avrami parameters, n1 = 1.46–1.67, n2 = 2.73–2.91, together with the results from SEM observations, indicated that the crystallization mechanism of LS was substantial surface crystallization while the crystallization mechanism of LS2 was dominant bulk crystallization. The calculated activation energy of glass transition was also determined EV = 516 kJ/mol.

Partial Substitution of Potassium with Sodium in the K2Ti2(PO4)3 Langbeinite-Type Framework: Synthesis and Crystalline Structure of K1.75Na0.25Ti2(PO4)3.

The interaction of TiN with Na2O–K2O–P2O5 melts was investigated at (Na+K)/P molar ratios of 0.9, 1.0, and 1.2 and at Na/K molar ratios of 1.0 and 2.0. Interactions in the system led to the loss of nitrogen and the partial loss of phosphorus and resulted in the formation of KTiP2O7 and langbeinite‐type K2−xNaxTi2(PO4)3 (x=0.22–0.26) solid solutions over the temperature range of 1173 to 1053 K. The phase compositions of the obtained samples were determined by using X‐ray diffraction (including Rietveld refinement), scanning electron microscopy (using energy‐dispersive X‐ray spectroscopy and element mapping), FTIR spectroscopy, and thermogravimetric analysis/differential thermal analysis. K1.75Na0.25Ti2(PO4)3 was characterized by single‐crystal X‐ray diffraction [P213 space group, a=9.851(5) Å]. The 3D framework is built up by TiO6 octahedra and PO4 tetrahedra sharing all the oxygen vertices with the formation of cavities occupied by K(Na) cations. Only one of the two crystallographically inequivalent potassium sites is partially substituted by sodium, and this was confirmed by calculating the bond‐valence sum. The thermodynamic stability of K1.75Na0.25Ti2(PO4)3 crystals and the preferable occupation sites of NaK cationic substitutions were investigated by DFT‐based electronic structure calculations performed by the plane‐wave pseudopotential method.

Two-phase fluid induced by N2 in metamorphic rocks

The first quantitative thermodynamic model of two-phase fluid induced by N2 and equilibrated with mineral assemblage in the system SiO2–TiO2–Al2O3–Fe2O3–MnO–MgO–CaO–Na2O–K2O–P2O5–H2O–CO2–N2 (STAFMMCNKPO–HCN) in the conditions of amphibolite facies rocks is proposed. Calculations are performed using the Gibbs free energy minimization technique. The fluid may consist of one phase, either aqueous solution (AS) or fluid with gas-like properties (FG), and also these two fluid phases (AS+FG) may co-exist, depending upon nitrogen content in the system. The values of total nitrogen at which AS co-exists with FG in the fluid were calculated at carbon saturation over a range in pressure and temperature of 3–7kb and 550–650°C. The model is capable of accurately describing various parameters of two fluid phases at each step of nitrogen increment in the system: density, partial pressure and mole fraction of constituents, pH, Eh, concentration of aqueous species. Increments of such an inert component as nitrogen cause the changes in the fluid resulting into subtle quantitative re-distribution of mineral phases in the assemblage plagioclase–biotite–quartz–ilmenite–garnet–apatite–graphite plus minor sillimanite and andalusite.

Subsolidus segregation of quartz in metamorphic differentiation of metasedimentary rocks

Thermodynamic modeling of the SiO2–TiO2–Al2O3–Fe2O3–MnO–MgO–CaO–Na2O–K2O–P2O5–H2O (STAFMMCNKPOH) system at 600°C, 5 kbar has been applied to investigate dissolution and re-precipitation of quartz. Comparing silica molality in the STAFMMCNKPOH and SiO2–H2O systems, there is seen to be no effect of mineral assemblage on quartz solubility. From quantitatively estimated water/rock ratio required to dissolve quartz completely, one can deduce that the segregation of quartz appears to be due to diffusive transport of silica in inner pore fluid rather than to advective transport (in fluid flow).

Soil nutrients losses by wind erosion in a citrus crop at southeast Spain

The purpose of this study was to analyze the influence of wind erosion on the productivity of citric crops over gypsiric Fluvisols in Gador area (Almeria, SE Spain) by blowing air through a wind tunnel. Wind erosion varies considerably depending on time since the last tillage. This is because a physical crust forms after tilling which protects the soil from wind. Crust formation in the study area is strongly favored by dew, which causes them to form in around a week. The repeated measurements ANOVA, as a nonparametric alternative to the ANOVA, using the Geiiser method and the Friedman test shows significant differences (P ≤ 0.05) in the fractions of very fine sand and coarse silt, which confirmed that very fine sand and coarse silt are the fractions most susceptible to loss from wind. The same statistical analysis for fertility showed smaller differences in organic carbon and K2O content, while N and P2O5 increased. Nutrients lost from wind imply an additional fertilization cost for a crop to be economically feasible. The cost of this restoration of nutrients lost from the soil because of wind erosion was based on experimental data taken in crusted soil and immediately after tilling. Losses in organic matter (O.M.), N, P2O5 and K2O were estimated based on the cost of fertilizers most commonly used in the area.

Effects of strong network modifiers on Fe3+/Fe2+ in silicate melts: an experimental study

The effect of CaO, Na2O, and K2O on ferric/ferrous ratio in model multicomponent silicate melts was investigated in the temperature range 1450–1550 °C at 1-atm total pressure in air. It is demonstrated that the addition of these network modifier cations results in an increase of Fe3+/Fe2+ ratio. The influence of network modifier cations on the ferric/ferrous ratio increases in the order Ca < Na < K. Some old controversial conceptions concerning the effect of potassium on Fe3+/Fe2+ ratio in simple model liquids are critically evaluated. An empirical equation is proposed to predict the ferric/ferrous ratio in SiO2–TiO2–Al2O3–FeO–Fe2O3–MgO–CaO–Na2O–K2O–P2O5 melts at air conditions.

The effect of CO2 and N2 on phase relations, fluid composition, and quartz solubility in amphibolite facies metamorphic rocks

Phase equilibria in the system SiO2–TiO2–Al2O3–Fe2O3–MnO–MgO–CaO–Na2O–K2O–P2O5–H2O–CO2–N2 are calculated to illustrate phase relations in amphibolite facies metasediments over a wide range of X[H2O–CO2–N2] conditions at 600 °C and 4.4 kb. Calculations are performed using the Gibbs free energy minimization technique. Results are presented in plots showing stable mineral assemblages as a function of total carbon in the system at varying water (\(a_{{{\text{H}}_{2} {\text{O}}}}\) = 1) content in the presence/absence of N2 in the fluid. The calculations indicate that the typical assemblage plagioclase—quartz—biotite—ilmenite—garnet—apatite is restricted to the rocks with CO2 saturation and \(X_{{{\text{H}}_{ 2} {\text{O}}}}\) higher than 60% in the fluid. Significant decrease in \(X_{{{\text{CO}}_{2} }}\) favors the stability of muscovite rather than garnet, whereas the decrease in \(X_{{{\text{H}}_{ 2} {\text{O}}}}\) leads to the stability of microcline over all range of \(X_{{{\text{CO}}_{2} }}\). This paper also presents the composition and parameters (pH, Eh) of the fluid equilibrated with mineral assemblage. It is shown that the presence of low concentrations of N2 causes the fluid to consist of two phases when an aqueous supercritical solution (AS) coexists with a supercritical fluid with gas-like properties (SF). At high concentration of N2, the fluid consists of SF alone; in the absence of nitrogen, the fluid consists of AS alone. The solubility of monomer SiO20 and dimer Si2O40 decreases with increasing CO2 and after CO2 saturation point is held constant. The magnitude of the silica solubility at CO2 saturation depends upon the water content in AS. The effect of nitrogen on quartz solubility has been demonstrated to be negligible.

KMg6(P2O7)2P3O10: A novel phosphate with two distinct anions

A novel mixed-anion phosphate, KMg6(P2O7)2P3O10, has been synthesized by spontaneous crystallization technique with K2O–P2O5–Li2O as a flux. Single-crystal X-ray analysis reveals that KMg6(P2O7)2P3O10 features two kinds of isolated anions, [P2O7] dimers and [P3O10] trimers. Such coexisting of two distinct anions in one polyphosphate, which has somewhat conflict with Pauling's parsimony (V) rule, is very rare in alkali metal and alkali-earth metal phosphates. This finding enriches the structural chemistry of phosphates and provides new perspective on the design of multiple anion materials. The thermal stability and a.c. conductivity of KMg6(P2O7)2P3O10 are also discussed in this paper.

Single-Component White Emitting Silicate Glass Triply Activated by Ce3+/Tb3+/Mn2+ for Organic-Resin-Free White LEDs

Thermal management is still a great challenge for high-power phosphor-converted white-light-emitting diodes (pc-WLEDs) intended for future general lighting. Luminescent glass based WLEDs (LG-WLEDs) are strongly expected to be an interesting and excellent alternative approach to traditional pc-WLEDs fabricated by combining InGaN based LED chips, with phosphor and organic resin. In the past years, many efforts have been made to develop luminescent glasses for LG-WLEDs. However, some of these glasses are poor in mechanical and chemical stability, some cannot be excited effectively owing to weak f-f absorption, and others are not very suitable for UV-LED chips ascribed to their maximum excitation wavelengths in deep UV. [1]In this paper, a series of single-component white emitting silicate SiO2–Li2O–SrO–Al2O3–K2O–P2O5: Ce3+, Tb3+, Mn2+(SLSAKP: Ce3+, Tb3+, Mn2+) glasses that simultaneously play key roles as a luminescent convertor and an encapsulating material for WLEDs were prepared via the conventional melt-quenching method. The as-synthesized SLSAKP: 0.3%Ce3+, 2.0%Tb3+, 2.0%Mn2+ glass shows good thermal stability, inconspicuous chromaticity shift, better high-temperature resistance, and higher thermal conductivity. These are rare but desirable characteristics that are not present in the phosphors used as luminescent convertor and the epoxy resin used as the encapsulating material in pc-WLEDs. Luminescent glass (LG-) WLEDs based on SLSAKP: 0.3%Ce3+, 2.0%Tb3+, 2.0%Mn2+glass and UV-COB was successfully fabricated. These results indicate that SLSAKP: Ce3+, Tb3+, Mn2+ glass may serve as a potential bifunctional white-light-emitting materialfor LG-WLEDs pumped by UV-LED chips, especially high-power UV-COB. Fig. 1. Photographic images of the mirror-polished (left) and rough-polished (right) SLSAKP: Ce3+, Tb3+, Mn2+glasses: (a) under white-emitting fluorescent lamp; (b) under 365 nm UV lamp. (c) The conceptual and actual fabrication process