Showing papers on "Silicate minerals published in 1972"

Organic Acids as Agents of Chemical Weathering of Silicate Minerals

Abstract: IN geologic weathering systems, organic acids such as fulvic and humic acids from humus or soil microorganisms decompose minerals dominantly by reacting with polyvalent cations in minerals to form water-soluble or -insoluble metallo-organic complexes (or chelates). Whether the complexes are soluble or insoluble is controlled primarily by the structures of ligands and relative stabilities of the complexes in relation to pH and Eh in the systems1–5. We report the results of the laboratory dissolution of common silicate minerals at room temperature in dilute and in 0.01 M, organic acids which contain such functional groups as carboxyl, hydroxy—and amino—which occur in soil acids and Other organic acids of geologic and pedologie systems. The systems fall into two categories: first, weakly complexing—acetic (monocarboxylic aliphatic) and aspartic (dicarboxylic amino aliphatic); and second, strongly complexing—citric (hydroxy, tricarboxylic aliphatic), tartaric (dihydroxy aliphatic), salicylic (monohydroxy aromatic) and tannic (commonly a mixture of aliphatic and polyhydroxy carboxylic acids).

Mineralogy and Petrology of the Iron Hill Carbonatite Complex, Colorado

Abstract: Bulk rock and mineral chemistry of the rock types occurring in the Iron Hill carbonatite complex have been examined in order to determine the genetic link between carbonatites and the alkaline igneous rocks with which they are ubiquitously associated. A variety of silicate rock types, including pyroxenite, uncom-pahgrite, ijolite, and nepheline syenite is developed at Iron Hill. The carbonatites are composed dominantly of calcite, ankeritic dolomite, or siderite. Only a rare variety of calcite carbonatite contains significant amounts of silicate minerals. Silicate minerals in the calcite carbonatite are generally intermediate in composition to those occurring in ijolite and nepheline syenite. These data, together with the scarcity of rock types gradational between silicate and carbonate varieties, suggest the possible separation of a discrete carbonate fluid phase during the latter part of the crystallization of the silicate series postdating formation of the ijolite but prior to the crystallization of the nepheline syenites. Calcite-dolomite and pyrite-pyrrhotite pairs indicate temperatures of crystallization of late-stage carbonatites of the order of 435° C to 290° C at sulfur fugacities of 10 −7.8 b and oxygen fugacities of the order of 10 −25 to 10 −26 b.

Occurrence of Nitride Nitrogen in Silicate Minerals

Abstract: NITROGEN is one of the most abundant elements in the cosmos; in the Sun, only H, He, O and C exceed it1. In the Earth's crust it ranks only as the thirty-first element in magmatic rocks2, at a level of about 20 p.p.m. Because of the analytic difficulties in determining the nitrogen content of rocks little work has been done in this direction since Lord Rayleigh's determinations3, which gave nitrogen contents in the range of 28 to 68 p.p.m. for a variety of magmatic rocks. These values are confirmed by recent determinations4. Most workers assume, without further proof, that most or all nitrogen is present as the ammonium ion3,5, substituting to a small extent for alkali ions in the minerals.

Infrared and Raman spectroscopic studies of structural variations in minerals from Apollo 11, 12, 14, and 15 samples.

Abstract: Infrared and Raman vibrational spectroscopic data, yielding direct information on molecular structure, were obtained for single grains ( 150 microns) of minerals, basalts, and glasses isolated from Apollo 11, 12, 14, and 15 rock and dust samples, and for grains in Apollo 14 polished butt samples. From the vibrational data, specification substitutions were determined for the predominant silicate minerals of plagioclase, pyroxene, and olivine. Unique spectral variations for grains of K-feldspar, orthopyroxene, pyroxenoid, and ilmenite were observed to exceed the ranges of terrestrial samples, and these variations may be correlatable with formation histories. Alpha-quartz was isolated as pure single grains, in granitic grains composited with sanidine, and in unique grains that were intimately mixed with varying amounts of glass. Accessory minerals of chromite and ulvospinel were isolated as pure grains and structurally characterized from their distinctive infrared spectra. Fundamental vibrations of the SiO4 tetrahedra in silicate minerals were used to classify bulk compositions in dust sieved fractions, basalt grains and glass particles, and to compare modal characteristics for maria, highland and rille samples. No hydrated minerals were found in any of the samples studied, indicating anhydrous formation conditions.

Formation of Polyorganosiloxanes from Silicate Minerals

Abstract: SEVERAL attempts have been made1–5 to prepare trimethylsilyl derivatives of inorganic mineral silicates, that is, to convert illustration in the hope that the preparation of these derivatives would both elucidate the structure of these silicates and provide a method for the preparation of new polyorganosiloxane materials of low cost. The original method proposed by Lentz1 has been improved by Gotz and Masson2,6,7 and by Currell et al.5 to give more reliable structural information on ortho and pyro silicates. The trimethylsilylation of chrysotile asbestos3,4, Mg3(Si2O5)(OH)4, yielded a solid having a similar morphology to the original material with pendant trimethylsiloxy groups. Open image in new window

The Geochemistry of Rubidium and Strontium

Abstract: Most igneous, metamorphic, and sedimentary rocks contain rubidium (Rb) and strontium (Sr) in detectable amounts. However, the concentrations of these elements are almost always less than 1 percent, and they are therefore rarely determined in routine chemical analyses. Neither rubidium nor strontium is a major constituent in the common rock-forming silicate minerals, although strontium does form a carbonate (strontianite) and a sulfate (celestite) which are found in some hydrothermal deposits and certain sedimentary rocks, particularly carbonates.

Energy Changes in Dehydroxylation of Silicate Minerals

Abstract: The dehydroxylation reactions of three 2: 1 layer type clay minerals, illite, vermiculite and chlorite and the measurement of relative thermal energies involved in the process have been reported.

Kaolinite coated with synthesized layer-type silicate minerals

Abstract: Complexes of particles of kaolinite coated with a layer-type clay-like mineral as disclosed in U.S. Pat. No. 3,252,757, and having improved mechanical properties.

Reaction between spinel-bonded magnesite refractories and cement mineral clinker

Abstract: Laboratory investigations of the reaction between MSh refractory and clinker minerals and oxides by the contact deposition method and the thermometric method showed that upon reaction of most of the oxides and silicate minerals at 1500°C there are no chemical or phase changes in the specimens; the refractoriness of the mixtures of refractory and oxide and of refractory and mineral as a rule is greater than 1750°C.

Bedded Zeolites in United States--Potential Industrial Minerals: ABSTRACT

Abstract: Zeolites are among the most common authigenic silicate minerals in sedimentary deposits. Zeolites occur in rocks that are diverse in age, lithology, and depositional environment, but they are most common in sedimentary rocks that originally contained abundant vitric material. Of the more than 30 naturally occurring zeolites, 6 commonly occur in bedded deposits that have not been subjected to deep burial or hydrothermal activity. These are analcime, chabazite, clinoptilolite, erionite, mordenite, and phillipsite. They are generally more siliceous and more alkalic than their counterparts that occur in mafic volcanic rocks. Most zeolites in sedimentary rocks formed during diagenesis mainly by reaction of vitric material with interstitial water, which may have originated as e ther meteoric water or connate water of a saline, alkaline lake. Formation of zeolites is favored by a relatively high pH and high activities of alkali ions in the interstitial water. Most zeolitic sedimentary rocks consist of 2 or more zeolites with authigenic clay minerals, silica minerals, or feldspars, and relict glass and crystal and rock fragments. Extensive and relatively pure beds of zeolite, however, occur in upper Cenozoic lacustrine deposits of the western United States. The ion exchange, adsorption, and molecular sieve properties of zeolites, coupled with a seemingly low cost of mining, suggest a variety of industrial applications. Potential uses include purification and drying of gases and liquids, chemical separations, catalysis, decontamination of radioactive wastes, removal of ammonia from wastewater, and numerous other uses in agriculture and animal husbandry. Potential uses of these zeolites could be considerably increased by chemical and structural modifications of the natural materials. End_of_Article - Last_Page 653------------

Low keV electron probe analysis of silicate minerals for Mg, Al, and Si using pure-element standards

Abstract: Accurate electron probe values for Mg, Al, and Si in silicate minerals may be obtained with pure-element standards. Analysis must be done at low (6 kV) accelerating potential and for best results, the average atomic number of the sample should be within about plus or minus 1 of the atomic number of the pure-element standard. This last requirement is automatically fulfilled for most common silicate minerals, as their average atomic numbers usually fall within the 11 to 15 range. Examples studied include a wet-chemically analyzed cordierite containing 17.71 weight percent Al, for which a value of 17.6 plus or minus 0.3 percent was obtained with the electron probe, and a hornblende containing 19.15 percent Si, which gave 19.0 plus or minus 0.3 percent using the probe method.