Silicate minerals

About: Silicate minerals is a research topic. Over the lifetime, 1794 publications have been published within this topic receiving 67064 citations.

Microfluidic Leaching of Soil Minerals: Release of K+ from K Feldspar.

Abstract: The rate of K+ leaching from soil minerals such as K-feldspar is believed to be too slow to provide agronomic benefit. Currently, theories and methods available to interpret kinetics of mineral processes in soil fail to consider its microfluidic nature. In this study, we measure the leaching rate of K+ ions from a K-feldspar-bearing rock (syenite) in a microfluidic environment, and demonstrate that at the spatial and temporal scales experienced by crop roots, K+ is available at a faster rate than that measured with conventional apparatuses. We present a device to investigate kinetics of mineral leaching at an unprecedented simultaneous resolution of space (~101-102 μm), time (~101-102 min) and fluid volume (~100-101 mL). Results obtained from such a device challenge the notion that silicate minerals cannot be used as alternative fertilizers for tropical soils.

Dianionic species with a bond consisting of two pentacoordinated silicon atoms

Abstract: Silicon can form bonds to other tetracoordinated silicon atoms and these bonds form the framework of many organosilicon compounds and crystalline silicon. Silicon can also form a pentacoordinated anionic structure—a so-called ‘silicate’. No compounds containing a direct bond between two silicate moieties—‘disilicates’ where two silicate structures are combined in one species—have been reported because of the electronic repulsion between the anionic halves and difficulty preventing the release of anions. Here we report the synthesis of thermally stable and isolable disilicates by the reductive coupling reaction of a silane bearing two electron-withdrawing bidentate ligands. Two pentacoordinated silicons, positively charged despite the formal negative charge, constitute a single σ-bond and bind eight negatively charged atoms. They can be reversibly protonated, cleaving two Si–O bonds, to afford a tetracoordinated disilane. Their unique electronic properties could be promising for the construction of functional materials with silicon wire made up of silicate chains. Silicon, like carbon, favours a four-coordinate geometry and this underpins the frameworks of the wide range of inorganic and organosilicon compounds, from silicate minerals to polysilanes. Although some pentavalent silicon compounds have already been reported, this work presents the first example where two five-coordinate silicon atoms are bonded to each other.

Authigenesis of titanium minerals in two Proterozoic sedimentary rocks from southern and central Sweden

Abstract: The occurrence of authigenic titanium minerals--rutile, anatase, brookite, and sphene--is recorded in two sequences of sedimentary rocks of Proterozoic age, namely the Visingso Group and the Dala Sandstone Formation. The rocks are sandstones, shales, and carbonates. Due to diagenesis of the Visingso Group and diagenesis to low-grade metamorphism of the Dala Sandstone Formation, the unstable titanium-bearing minerals, mostly biotite and ilmenite, released their titanium. This titanium was involved in the formation of different titanium minerals either on the altered detrital particles, mostly biotite and ilmenite, or in pore spaces. These titanium minerals are often found to attack silicate minerals such as quartz and feldspars. Due to higher temperature and pressure, euhedral sphene a d rutile are more common in the Dala Sandstone Formation.

Geographical variations in Sr and Nd isotopic ratios of cryoconite on Asian glaciers

Abstract: Cryoconite is a dark-coloured surface dust deposited on glaciers that consists of wind-blown mineral particles, as well as organic matter derived from microbes living on glaciers. In this paper, we analyse the Sr and Nd isotopic ratios of four mineral fractions (i.e., the saline, carbonate, phosphate, and silicate mineral fractions), as well as the organic fraction, of cryoconite samples obtained from six Asian glaciers (the Altai, Pamir, Tien Shan, Qillian Shan, and Himalayan regions), and discuss their geographical variations in terms of the geological origins of the mineral particles and the biogeochemical processes on the glaciers. The silicate mineral fraction showed lower Sr and higher Nd ratios for the glaciers located to the north (Altai, 87Sr/86Sr: 0.713?490?0.715?284, ?Nd(0): ?6.4 to ?5.6), while higher Sr and lower Nd ratios for the glaciers located to the south (Himalayas, 87Sr/86Sr: 0.740?121?0.742?088, ?Nd(0): ?16.4 to ?15.7); the ratios were similar to those of desert sand, loess, and river sediments in the respective regions of the glaciers. This result suggests that the silicate minerals within the cryoconites were derived from different sources depending on the geographical locations of the glaciers. The isotopic ratios of the saline, carbonate, and phosphate mineral fractions were distinct from those of the silicate fraction, and were similar to those of evaporites and apatite deposits from the Asian deserts, but also varied geographically, indicating that they are likely to reflect their geological origin. The Sr isotopic ratios of the organic fraction were similar to those of the saline and carbonate fractions from glaciers in the central area (Tien Shan and Qillian Shan), but were higher than those of the saline and carbonate fractions, and lower than the phosphate mineral fraction, in the northern and southern areas. The ratios of organic fraction may be determined from the mixing ratio of calcium sources incorporated by microbes on the glaciers.