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Silicate minerals

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


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Journal ArticleDOI
TL;DR: The Nova 001 and Nullarbor 010 meteorites as discussed by the authors contain euhedral graphite crystals (to 1 mm x 0.3 mm) at silicate grain boundaries, along boundaries and protruding into the silicates, and entirely within silicate mineral grains.
Abstract: The Nova 001 (= Nuevo Mercurio (b)) and Nullarbor 010 meteorites are ureilites, both of which contain euhedral graphite crystals. The bulk of the meteorites are olivine (Fo79) and pyroxenes (Wo9En73Fs18, Wo3En77Fs20), with a few percent graphite and minor amounts of troilite, Ni-Fe metal, and possibly diamond. The rims of olivine grains are reduced (to Fo91) and contain abundant blebs of Fe metal. Silicate mineral grains are equant, anhedral, up to 2 mm across, and lack obvious preferred orientations. Euhedral graphite crystals (to 1 mm x 0.3 mm) are present at silicate grain boundaries, along boundaries and protruding into the silicates, and entirely within silicate mineral grains. Graphite euhedra are also present as radiating clusters and groups of parallel plates grains embedded in olivine; no other ureilite has comparable graphite textures. Minute lumps within graphite grains are possible diamond, inferred to be a result of shock. Other shock effects are limited to undulatory extinction and fracturing. Both ureilites have been weathered significantly. Considering their similar mineralogies, identical mineral compositions, and identical unusual textures, Nova 001 and Nullarbor 010 are probably paired. Based on olivine compositions, Nova 001 and Nullarbor 010 are in Group 1 (FeO-rich) of Berkley et al. (1980). Silicate mineral compositions are consistent with those of others known ureilites. The presence of euhedral graphite crystals within the silicate minerals is consistent with an igneous origin, and suggests that large proportions of silicate magma were present locally and crystallized in situ.

35 citations

Journal ArticleDOI
01 Jan 2010
TL;DR: In this paper, the authors used synchrotron Fe-XANES, XRS, micro Raman, and SEM-TEM analyses of Stardust track 41 slice and track 121 terminal area slices to identify Fe oxide (magnetite-hematite and amorphous oxide).
Abstract: We have used synchrotron Fe-XANES, XRS, micro Raman, and SEM-TEM analyses of Stardust track 41 slice and track 121 terminal area slices to identify Fe oxide (magnetite-hematite and amorphous oxide). Fe-Ti oxide, and V-rich chromite (Fe-Cr-V-Ti-Mn oxide) grains ranging in size from 200 nm to similar to ~10 μm. They co-exist with relict FeNi metal. Both Fe-XANES and microRaman analyses suggest that the FeNi metal and magnetite(Fe2O3FeO) also contain some hematite (Fe2O3). The FeNi has been partially oxidized (probably during capture), but on the basis of our experimental work with a light-gas gun and microRaman analyses, we believe that some of the magnetite-hematite mixtures may have originated on Wild 2. The terminal samples from track 121 also contain traces of sulfide and Mg-rich silicate minerals. Our results show an unequilibrated mixture of reduced and oxidized Fe-bearing minerals in the Wild 2 samples in an analogous way to mineral assemblages seen in carbonaceous chondrites and interplanetary dust particles. The samples contain some evidence for terrestrial contamination, for example, occasional Zn-bearing grains and amorphous Fe oxide in track 121 for which evidence of a cometary origin is lacking.

35 citations

Journal Article
TL;DR: In this article, the dielectric and polarization properties of synthetic forsterite (MgrSiOo) were derived from capacitance measurements of single crystals of Mott and Littleton (1938) for orientations parallel to the a, b, and c crystallographic axes.
Abstract: The determination of the dielectric and polarization behavior of silicate minerals is important in the understanding of chemical bonding and the evaluation of interionic potentials in model calculations. The analysis of crystal-defect energetics and the atomistic theory of diffusion processes rely heavily upon the polarizability of component ions in the silicate. In this effort, dielectric constant (relative dielectric permittivity) and dielectric loss data have been obtained from capacitance measurements of single crystals of synthetic forsterite (MgrSiOo) for orientations parallel to the a, b, and c crystallographic axes. Measurements were obtained as a function of temperature (25C,4C-1000'C) and electric-field frequency (20 kHz-l MHz). The static polarizabilities of forsterite at these temperatures are derived from the dielectric constants by utilizing the Clausius-Mosotti relation. The use of the polarizability additivity rule is confirmed for predicting the polarization of forsterite from the component oxides at high temperatures. Dielectric conductivities are determined from the dielectric loss values at 40G900'C and are in agreement with previous studies of single-crystal forsterite. INrnooucrroN In recent years there has developed an interest in quantiffing the kinetics ofgeochemical and mineralogical processes. The comprehension of reaction mechanisms and of the approach of a mineral assemblage to equilibrium is vital for the application of geothermometry and geochronology, as well as for the analysis of mineral alteration, order-disorder status in minerals, crystal-growth and nucleation processes, and others. A useful and powerful technique in such an efort is the theoretical analysis of the basic atomic structure and energetics of the phases of concern. Although application of solid-state physics to ionic solids and other simple compounds has generally been met with success (see Kittel, 1976), there are limitations in analyzing the more complex atomistic nature of silicate minerals. The major hindrance in such an effort is evaluating the degree ofcovalency associated with the silicate mineral bonding, in particular the Si4 bond (Pauling, I 980), and the related polarization properties of the crystal (Lasaga and Cygan, 1982; Cygan and Lasaga, in prep.). The recognition of the influential role of polarization in crystal bonding and lattice eneryies lies in the classic work of Mott and Littleton (1938). They determined the theoretical polarization energy about a lattice point that contains an excess ofcharge (i.e., a point defect) and ap

35 citations

Journal ArticleDOI
TL;DR: The water quality index has indicated that the water quality of the lake is unsuitable for drinking from pre- to post-monsoon, whereas several parameters like salinity index, sodium adsorption ratio, sodium percent, residual sodium carbonate, magnesium hazard etc have revealed the water of Rewalsar Lake as suitable for irrigation.
Abstract: The present research is to study hydrochemistry and water quality of Rewalsar Lake during pre-monsoon, monsoon, and post-monsoon seasons. The Ca2+ and Na+ are observed as the dominant cations from pre- to post-monsoon season. On the other hand, HCO3− and Cl− are observed dominant anions during pre-monsoon and monsoon seasons, whereas HCO3− and SO42− during post-monsoon season. The comparison of alkaline earth metals with alkali metals and total cations (Tz+) has specified that the carbonate weathering is the dominant source of major ions in the water of lake. The HCO3− is noticed to be mainly originated from carbonate/calcareous minerals during monsoon and post-monsoon, but through silicate minerals during pre-monsoon. The SO42− in Rewalsar Lake is produced by the dissolution of calcite and dolomite etc. The alkali metals and Cl− in the lake can be attributed to the silicate weathering as well as halite dissolution and anthropogenic activities. Certain other parameters like NO3−, NH4+, F−, and Br− are mainly a result of anthropogenic activities. The alkaline earth metals are found to surpass over alkali metals, whereas weak acid (HCO3−) exceed to strong acid (SO42−). The Piper diagram has shown Ca2+–HCO3− type of water during all the seasons. The water quality index has indicated that the water quality of the lake is unsuitable for drinking from pre- to post-monsoon. Several parameters like salinity index, sodium adsorption ratio, sodium percent, residual sodium carbonate, magnesium hazard etc. have revealed the water of Rewalsar Lake as suitable for irrigation.

35 citations

Book ChapterDOI
01 Jan 1988
TL;DR: In this paper, the main factors controlling the rates of the chemical weathering of silicate minerals were investigated and the end products of this process were predicted. But the main focus of this paper was not on the weathering process itself, but rather on predicting its end products.
Abstract: The present paper deals with the weathering mechanisms of silicate minerals from a fundamental point of view. The goal of such a study is to understand the main factors controlling the rates of this process and to predict its end products. The chemical weathering of silicates is one of the major processes responsible for the transfer of dissolved and eventually particulate components from land to sea.

35 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
202264
202153
202064
201951
201865