Hydrous, silica-rich melts migrating through the mantle are preserved as glass inclusions in mantle minerals in xenoliths from Philippine arc lavas. These melts, with chemistries that indicate an origin by very low degrees of melting of the subducted ocean crust, have altered their host peridotites, yielding a metasomatized mantle. This 'fertilized' mantle is the source region of the arc magmas, which share continuous chemical trends with the melt inclusions, reflecting mixing and/or varying degrees of melting. These observations provide direct evidence for the importance of slab–mantle interactions in the genesis of island-arc magmas.

Characterising the extent of volcanism at the Galapagos spreading centre using deep tow sediment profiler records

Ferrihydrite (Fh) is of great importance in affecting the migration and transformation of heavy-metal cations and oxyanions. To advance the understanding of co-adsorption reactions on Fh surface, the co-adsorption of phosphate and Zn(II) from aqueous solution to a synthesized Fh was determined. The batch experiments demonstrated a synergistic adsorption of phosphate and Zn(II) on Fh. In the pH range of 3.5 to 6, the adsorption of the two contaminants showed strong pH dependence in the single solute adsorption systems, but the dependence alleviated in the simultaneous adsorption system. X-ray photoelectron spectroscopy (XPS) revealed that the chemical shifts of Zn 2p 1/2 and Zn 2p 3/2 binding energies were more significant than that of P 2p in the single and simultaneous adsorption systems. On the other side, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) suggested increased formation of outer- and inner-sphere complexes of phosphate in the simultaneous system. Thus, the synergistic adsorption of the two contaminants could be attributed to the formation of ternary complexes as well as electrostatic interactions, while surface precipitation could not be completely ruled out. On the basis of the results from both the batch adsorption experiments and structural characterization, these two contaminants were likely to form phosphate-bridged ternary complexes (≡Fe-P-Zn) on Fh in the simultaneous adsorption system.

Co-adsorption of phosphate and zinc(II) on the surface of ferrihydrite

Geochemical transfer of cadmium in river sediments near a lead-zinc smelter

Application of neural networks to South African GPS TEC modelling

The geochemical behaviour of phosphate and arsenate ions in soil and aquatic systems is determined by the presence of mineral surfaces and major ions. Information about the distribution of oxyanions over the solid and solution phases is essential for understanding the transport, bioavailability and toxicity of these compounds in the environment. Here, we studied the adsorption of both arsenate and phosphate on ferrihydrite nanoparticles in the presence of calcium ions. The presence of calcium ions enhanced the retention of these oxyanions on ferrihydrite and vice versa. The arsenate–calcium and phosphate–calcium multi-component systems were described using a mechanistic surface complexation model. Use of this type of model enables prediction of the solution and surface speciation, along with analysis of oxyanion mobility in relation to environmental conditions. We were able to calibrate the charge distribution model with the macroscopic data obtained for the single-component systems, thus obtaining surface complexation constants for later use to simulate multi-component systems. The mutual interactions between arsenate and calcium were successfully described with these parameters, indicating that changes in the electrostatic forces at the solid/solution interface caused the observed enhanced adsorption. However, adsorption in the phosphate–calcium system was underestimated with the parameters obtained for the single-component systems, indicating that additional mechanisms or processes should be considered. Formation of insoluble mineral phases was ruled out, but the inclusion of a phosphate–calcium ternary surface complex improved the modelling predictions.

SD CHEMGE 17606 - Arsenate and phosphate adsorption on ferrihydrite nanoparticles. Synergetic interaction with calcium ions

TEC derived from GPS network in India and comparison with the IRI

This study demonstrates the compositional and structural analysis of surface sediments in natural depositional environment of the Brahmaputra River using X-ray fluorescence, Raman spectroscopic and Fourier transform infrared spectroscopic techniques. The main peaks in the Raman and infrared spectra reflected Al-OH, Al-O and Si-O functional groups in high frequency stretching and low frequency bending modes. The Raman and infrared spectra reveals the nature of clay (kaolinite) associated with quartz. The infrared spectra are indicative to the weathered metamorphic origin of the silicate minerals. The relative distributions of the contaminations in the sediment are: Si > Al > Fe > Mg > Ca > K > Ti > Mn > Cr >Ni > Zn > Cu > Co. The metal contaminations in the sediments are investigated by calculating the enrichment factor, contamination factor, geo-accumulation index and pollution load index. The relative distributions of the contamination among the samples are: Cu > Si > Mn > Mg > Ni > Cr > Ti > Al > Co > Pb > K > Ca > Zn. The investigating factors suggest the significant contamination in the sediment is due to Cu. The strong positive correlation among Al, Fe, Mg and K suggests association of sediments with clay. The elemental correlation is indicative to the metamorphosed pyrophanite (MnTiO3) deposition.

/pdf/raman-and-ftir-spectroscopic-evaluation-of-clay-minerals-and-3opmjyy9ni.pdf

Raman and FTIR Spectroscopic Evaluation of Clay Minerals and Estimation of Metal Contaminations in Natural Deposition of Surface Sediments from Brahmaputra River

pH dependent leachings of some trace metals and metalloid species from lead smelter slag and their fate in natural geochemical environment

Aqueous extract of okra called here as bio-admixture was characterized and tested for using as a sustainable chemical admixture in the production of cement mortar and concrete . Several fresh and hardened states properties of cement mortars and concrete with and without the presence of bio-admixture were evaluated. Interactions of bio-admixture with cement particles during hydrations were also investigated by using conductometric and FTIR spectroscopic methods. Moreover, an improved method was developed to determine water retention capacity of cement pastes . Results indicate that the investigated bio-admixture exhibits viscosity enhancing property. In comparison to the reference cement paste, bio-admixture containing cement pastes have shorter setting times due to increasing hydration rate of cement particles. Solution chemistry and FTIR spectroscopic investigation indicate that the addition of bio-admixture enhances cement hydration rate. Increase hydration rate can be related with the interactions of pectin type heteropolysaccharides present in bio-admixture with Ca 2+ ions of cement paste. Compressive strengths of bio-admixture containing mortar and concrete are higher than that of the reference specimens at the investigated curing period. Deterioration of strength of bio-admixture based mortars cured in MgSO 4 -NaCl solution is distinctly less in comparison to reference, depicting higher durability under such conditions. Most of the properties of cement mortar and concrete are also dependent on the concentrations of bio-admixture in aqueous solution. Therefore, investigated bio-admixture can be considered as a low-cost, environmentally benign viscosity enhancing admixture for producing sustainable cement composites having improved mechanical and durability properties.

Use of a plant based polymeric material as a low cost chemical admixture in cement mortar and concrete preparations

We present here the Raman spectroscopic study of silicate and carbonaceous minerals in three ordinary chondrites with the aim to improve our understanding the impact process including the peak metamorphic pressures present in carbon-bearing ordinary chondites. The characteristic Raman vibrational peaks of olivines, pyroxenes, and plagioclase have been determined on three ordinary chondrites from India, Dergaon (H5), Mahadevpur (H4/5), and Kamargaon (L6). The Raman spectra of these meteorite samples show the presence of nanodiamonds at 1334–1345 cm−1 and 1591–1619 cm−1. The full-width at half maximum (FWHM) of Raman peaks for Mahadevpur and Dergaon reflect the nature of shock metamorphism in these meteorites. The frequency shift in Raman spectra might be because of shock effects during the formation of the diamond/graphite grains.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.12850

Rashmi R. Borah

Papers

TEC derived from GPS network in India and comparison with the IRI

Raman and FTIR Spectroscopic Evaluation of Clay Minerals and Estimation of Metal Contaminations in Natural Deposition of Surface Sediments from Brahmaputra River

pH dependent leachings of some trace metals and metalloid species from lead smelter slag and their fate in natural geochemical environment

Use of a plant based polymeric material as a low cost chemical admixture in cement mortar and concrete preparations

Nanodiamonds and silicate minerals in ordinary chondrites as determined by micro-Raman spectroscopy