Most minerals, with the possible exception of micas, commonly contain fluid inclusions, Argon contained in such inclusions may be considered a possible source of error in dating very young or low potassium minerals by the K-Ar method.
Wahler [1956] first demonstrated spectrographically the presence of Ar in fluid inclusions in quartz. Elinson and Polykovskii [1961, 1963] used a vacuum ball mill to extract the gases present in fluid inclusions in various pegmatite minerals. They obtained Ar from quartz in quantities up to 8.9×10−3 cc/g. Preisinger and Huber [1964] state that they determined the Ar content of the gas emitted by heating very small samples (10−6 g) of feldspar crystals from a granite in a cycloidal mass spectrometer. The total gas emitted (water-free basis) varied from 0.8 to 3.3×10−3 cc/g. Nesmelova [1959] found up to 1.7% (Ar + Kr + Xe) in the gas from gas inclusions in sylvites from the Bereznikovsk mine in the USSR. Hoy et al. [1962] found 0.4 volume % Ar in the gases of highpressure gas inclusions in ‘popping-salt’ from the Winnfield salt dome in Louisiana. Sample weight and total gas volume were not specified. Damon and Kulp [1958] extracted excess radiogenic Ar from beryl, cordierite, and tourmaline in quantities ranging from 10−5 cc/g to 10−2 cc/g, some of which was assumed to come from fluid inclusions (p. 449). Lippolt and Gentner [1963] reported the finding of excess radiogenic Ar of the order of 10−7 cc/g in several fluorite samples and indicated that much of the excess was probably contained in fluid inclusions.
Colloform ores have generally been considered to have been deposited as colloidal sulfide gels, and even transported as colloidal sols. However, studies of doubly polished plates of colloform sphalerite-wurtzite assemblages from various deposits reveal crystal growth features that cannot have been formed by crystallization from gels, and indicate that most, and perhaps all, grew directly as minute druses of continuously euhedral crystals projecting into an ore fluid. Each of the many textural criteria proposed for recognizing colloidal deposition is shown to be invalid, ambiguous, or inapplicable to these samples, and perhaps also to most other colloform mineral samples.Four conclusions pertinent to ore research are derived from this study: (1) Primary fluid inclusions in colloform samples are believed to represent the original ore fluid, not merely a residual fluid from the crystallization of a gel. (2) Although euhedral crystals may possibly grow directly from a sol, several features make a noncolloidal (true solution) ore fluid more probable. (3) Maintenance of the large number of crystal nuclei responsible for the colloform texture is attributed to relatively high supersaturation, and hence relatively high nucleation and growth rates, for the temperatures involved. (4) Remarkably uniform, regular compositional microbands, traversing many crystals in samples from the east Tennessee, Aachen, and particularly the Pine Point deposits, are tentatively interpreted as annual varves. No actual growth rates have been determined, but each varve consists of a dark and a light band, outlining sharply euhedral former crystal growth patterns and suggesting an annual change in the ore fluid due to dilution with surface waters of varying volume or chemistry (e.g., oxygen or organic content).
Carbonatites are igneous rocks formed in the crust by fractional crystallization of carbonate-rich parental melts that are mostly mantle derived. They dominantly consist of carbonate minerals such as calcite, dolomite, and ankerite, as well as minor ...Read More
Research Article| November 01, 1981 Problems in determination of the water content of rock-salt samples and its significance in nuclear-waste storage siting Edwin Roedder; Edwin Roedder 1U.S. Geological Survey, 959 National Center, Reston, Virginia 22092 Search for other works by this author on: GSW Google Scholar R. L. Bassett R. L. Bassett 2Bureau of Economic Geology, University of Texas at Austin, Austin, Texas 78712 Search for other works by this author on: GSW Google Scholar Author and Article Information Edwin Roedder 1U.S. Geological Survey, 959 National Center, Reston, Virginia 22092 R. L. Bassett 2Bureau of Economic Geology, University of Texas at Austin, Austin, Texas 78712 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1981) 9 (11): 525–530. https://doi.org/10.1130/0091-7613(1981)9<525:PIDOTW>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Edwin Roedder, R. L. Bassett; Problems in determination of the water content of rock-salt samples and its significance in nuclear-waste storage siting. Geology 1981;; 9 (11): 525–530. doi: https://doi.org/10.1130/0091-7613(1981)9<525:PIDOTW>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The in situ water content of rock salt in beds or domes and the exact nature of its occurrence are of considerable importance for the safe design and operation of nuclear-waste storage facilities in salt deposits. Most published determinations of the "water content" of salt are not comparable. Many determinations contain serious, and in part systematic, errors. The multiplicity of water sources in salt samples, the methods of sample selection and preparation, and the analytical methods used are such that some of these results may be low by as much as an order of magnitude. There is no panacea, but most of the sources of error can be minimized. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
We have measured noble gases in 17 diamond samples, mostly inclusion free, from diverse, known locations. The 3 He/ 4 He ratios are characterized by a large spread (10 4 ), ranging from values below atmospheric to close to the solar ratio. Highest ratios were seen for an Australian colorless diamond composite and an Arkansas diamond. These samples also have imprecise but intriguing neon isotopic ratios, which are close to the solar value. An origin for the solarlike He and Ne in the diamond samples is unlikely to be accounted for by the presence of nucleogenic or spallogenic components. For single diamond stones a positive correlation is found between 3 He/ 4 He and 13 C/ 12 C, possibly indicating that heavy carbon is accompanied by primordial helium. However, the He result for the Australian colorless diamond composite with low δ 13 C value requires another explanation, possibly sedimentary carbon contaminated with cosmic dust. The wide variation in 4 He/ 40 *Ar ratios observed from diamond samples suggests a complex history for the source regions and the diamond crystallization processes. Results for two Australian diamond composites (colorless and colored), which came from the same kimberlite pipe, are especially notable: the colorless stones contain no radiogenic components but solarlike He and Ne isotopic ratios, whereas the colored stones are enriched in radiogenic and fissiogenic components. Seemingly the Australian diamonds crystallized in a heterogeneous environment in the mantle source region. A pair of Arkansas diamonds, believed to be from a single pipe, exhibits similar anomalies.
Core samples from the Rayburn and Vacherie salt domes in Louisiana were examined for fluid inclusions, in connection with the possible use of such domes for nuclear waste storage sites. Three types of fluid inclusions were found, brine, compressed gas, and oil (in decreasing volume percent abundance). The total amount of such fluids is small, certainly < 0.1 vol. % and probably in the range 0.01 to 0.001 volume %, but the inclusions are highly erratic in distribution. Unlike many bedded salt deposits, the brine inclusions in this salt contain fluids that are not far from simple NaCl-H2O solutions, with very little of other ions. One of three possible explanations for such fluids is that fresh water penetrated the salt at some unknown time in the past and was trapped; if such entry of fresh water has occurred in the past, it might also occur again in the future.
A method has been developed for the extraction and chemical microanalysis of individual fluid inclusions, or groups of inclusions, in the milligram range. Usable quantitative analyses for Na, K, Ca, Mg, Cl, B, and SO 4 have been obtained of mineral samples containing several milligrams of inclusion fluid, and with increased experimental errors, on fractional milligram samples. The steps involved are: 1) concentration of inclusions by sample selection and cutting; 2) electrolytic cleaning; 3) crushing in soft Cu sample tube in vacuo; 4) conversion of emitted water to H and determination of its volume; 5) mass spectrometric determination of the D/H ratio if desired; 6) leaching of the crushed mineral to dissolve soluble salts remaining; 7) microanalysis of the filtrate by sensitive colorimetric and flame photometric methods. The method has been applied to determine the composition of fluid inclusions in mineral samples from several types of deposits, with special attention to a series of samples from Mississippi Valley-type ore deposits.
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