Chemical Composition of an Unusual Xenolith of the Allende Meteorite

1989 ◽  
Vol 44 (10) ◽  
pp. 1005-1014 ◽  
Author(s):  
H. Palme ◽  
G. Kurat ◽  
B. Spettel ◽  
A. Burghele
Keyword(s):  
Chemical Composition ◽  
Bulk Composition ◽  
Forming Process ◽  
Volatile Elements ◽  
X Ray ◽  
Fine Grained ◽  
Oxygen Isotopic ◽  
Fine Grained Material ◽  
Chondrule Formation ◽  
Type 3

Abstract The chemical composition of an unusual xenolith (All-AF) from the Allende meteorite was determined by neutron activation and x-ray fluorescence analyses. The xenolith is similar in bulk composition to Allende, but has large excesses in some moderately volatile trace elements, such as Na, K, Au, Sb etc. Some of these elements show considerable variations in other components of Allende, suggesting inhomogeneous distribution in Allende. However, elements of higher volatility, such as Zn and Se have concentrations typical of bulk Allende and other type 3 carbonaceous chondrites. Therefore, All-AF must have formed from the same reservoir as bulk Allende.All-AF has uniform grain size and does not, and did never, contain chondrules. The low content of volatile elements, therefore cannot be ascribed to loss of volatiles during the chondrule forming process. It is a characteristic of the Allende reservoir. The chemical composition of related dark inclusions (DIs) in Allende is different from All-AF. Dark inclusions may have formed by separation of fine grained material in the early solar nebula while All-AF resembles bulk Allende material that was never subject to chondrule formation. Both, dark inclusions and All-AF have oxygen isotopic compositions which plot at the upper end of the δ18O vs. δ17O correlation, suggesting extensive oxygen exchange with ambient gas.

XRF Macroprobe Analysis of Geologic Materials

1989 ◽  
Vol 33 ◽  
pp. 593-601
Author(s):  
N. L. Gilfrich ◽  
D. E. Leyden ◽  
E. A. Erslev
Keyword(s):  
Electron Beam ◽  
Spatial Resolution ◽  
Bulk Composition ◽  
Intermediate Scale ◽  
X Ray ◽  
Fine Grained ◽  
Geologic Materials ◽  
Mineral Aggregates

An x-ray fluorescence macroprobe was built for intermediate-scale compositional mapping to bridge the gap in spatial resolution between bulk x-ray fluorescence and electron beam methods. The macroprobe was optimized for quantitative whole rock mapping on a millimeter scale to evaluate changes in bulk composition of fine-grained mineral aggregates.

Study Butte: A Chaotic Chondrite Breccia with Normal H-Group Chemistry

1989 ◽  
Vol 44 (10) ◽  
pp. 945-962
Author(s):  
K. Fredriksson ◽  
E. Jarosewich ◽  
F. Wlotzka
Keyword(s):  
Closed System ◽  
Bulk Composition ◽  
Analytical Data ◽  
Wide Spread ◽  
Multi Stage ◽  
H Chondrites ◽  
Compaction Processes ◽  
Chondrule Formation ◽  
Type 3 ◽  
Discrete Populations

Abstract The Study Butte (SB) H-group chondrite is an accretionary, well-indurated, multicomponent breccia of exceptional complexity. It contains practically all previously described types of chondrules (in two discrete populations according to Fe/Mg and Al/Ca distributions) and fragments (including CAI’s and also some which were not observed before, e.g. an “andesite”); furthermore it is gas-rich. According to currently popular definitions, it can be ascribed to petrographic type 3 based on overall texture, presence of glass in chondrules and the wide spread of pyroxene and olivine composition (PMD 30), although about 2/3 have nearly constant Fa 17 (PMD 4) in the normal H-range. In addition, Al and Ca in individual chondrules with normal H-olivines, Fa 16-20, are negatively correlated, as usual in chondrules from H 4.5 chondrites [3], but are positively correlated in other chondrules. Thus SB has the properties of both “equilibrated” and “unequilibrated” chondrites. However, in spite of the multitude and complexity of components, the bulk composition is that of normal H-chondrites. A great variety of multi-stage accretion and chondrule formation, break-ups, heating and compaction processes in a quasi closed system are clearly indicated; no clues to preceding nebular processes have been recognized. After the descriptive and analytical data a “Model”, based upon bulk composition, for the formation of chondrules and chondrites is presented.

scholarly journals Oxygen isotopic composition of coarse- and fine-grained material from comet 81P/Wild 2

2015 ◽  
Vol 166 ◽  
pp. 74-91 ◽  
Author(s):  
Ryan C. Ogliore ◽  
Kazuhide Nagashima ◽  
Gary R. Huss ◽  
Andrew J. Westphal ◽  
Zack Gainsforth ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotopic Composition ◽  
Fine Grained ◽  
Oxygen Isotopic ◽  
Fine Grained Material

COMPARISON OF CHEMICAL COMPOSITION OF SOILS AND BEDROCK OF MONT ST. HILAIRE, QUEBEC

1965 ◽  
Vol 2 (2) ◽  
pp. 44-58 ◽  
Author(s):  
G. R. Webber ◽  
J. U. Jellema
Keyword(s):  
Chemical Composition ◽  
Parent Material ◽  
Soil Samples ◽  
Forming Process ◽  
X Ray ◽  
Areal Distribution ◽  
Distribution Of Elements ◽  
Intrusive Rocks

Soil samples from Mont St. Hilaire, one of the Monteregian Hills of Quebec, were analyzed by X-ray fluorescence for the elements Fe, Ca, K, Ti, Mn, Sr, Zr, Nb, Zn, and Rb. The samples were taken below the surface organic-rich horizon.The composition of the parent material was calculated by comparing the soils with local rocks having similar Ti/Zr ratios, assuming that the Ti/Zr ratio has not changed appreciably during the soil-forming process. This comparison indicates that there has been little change in the concentration of most of the elements during weathering. Average ratios of concentration in soils to concentration in calculated parent material for the elements were Fe 1.25, Nb 1.11, Ca 1.08, Rb 1.07, Zn 1.02, Zr 0.96, Ti 0.94, Mn 0.82, Sr 0.69, K 0.54; that is, Fe showed a tendency to accumulate, and K, Sr, and possibly Mn showed a tendency to be depleted in the soils.The areal distribution of elements in the soils is in general agreement with what is known of the distribution of syenitic and essexitic intrusive rocks which make up most of the mountain.

Zussmanite in ferruginous metasediments from Southern Central Chile

1998 ◽  
Vol 62 (6) ◽  
pp. 869-876 ◽  
Author(s):  
H.-J. Massonne ◽  
F. Hervé ◽  
O. Medenbach ◽  
V. Muñoz ◽  
A. P. Willner
Keyword(s):  
Chemical Composition ◽  
Metamorphic Rocks ◽  
Stability Field ◽  
Low Grade ◽  
Central Chile ◽  
X Ray ◽  
Fine Grained ◽  
Southern Central ◽  
Similar Phase

AbstractZussmanite KFe13[AlSi17O42](OH)14, a modulated 2:1 layer silicate, has so far been found only in iron-rich metasediments from Laytonville, California (Agrellet al.), 1965). A new occurrence is reported here from Punta Nihue north of Valdivia, Chile, in banded stilpnomelane-schists. These are intercalated in the ‘Western Series’, a complex of low-grade metamorphic rocks with local high-pressure, low-temperature overprint (e.g. blueschists).The rock contains conspicuous porphyroblasts of zussmanite of mm size and is composed of chemically distinct bands with the subsequent assemblages: (1) zussmanite-stilpnomelane-quartz, (2) siderite-quartz±stilpnomelane (3) apatite-stilpnomelane-quartz±siderite. The chemical composition of zussmanite, (K0.80Na0.05Ba0.01)(Fe11.292+Mg1.11Mn0.25Fe0.143+Cr0.01Al0.19Ti0.01)[Al1.23Si16.77O42](OH)14, its optical properties and X-ray data correlate well with the Californian occurrence. Additionally, we present new IR data. In type (2) bands of fine-grained crystals of a K,Al poor mineral formed from siderite and quartz. Its chemical composition is close to that of zussmanite. A similar phase was also reported from Laytonville, California (Muir Wood, 1980).The rarity of rock-forming zussmanite can be explained by its occurrence in strongly Fe-rich and reduced rocks, as well as, by a possibly narrowP-Tstability field.

scholarly journals Evaluation of the initial stage of the reactivated Cotopaxi volcano – analysis of the first ejected fine-grained material

2015 ◽  
Vol 3 (11) ◽  
pp. 6947-6976 ◽  
Author(s):  
T. Toulkeridis ◽  
C. R. Arroyo ◽  
M. Cruz D'Howitt ◽  
A. Debut ◽  
A. V. Vaca ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Data Base ◽  
Preventive Measures ◽  
Fine Grained ◽  
Rock Fragments ◽  
Initial Stage ◽  
Cotopaxi Volcano ◽  
Fine Grained Material ◽  
Low Probability ◽  
Existing Data

Abstract. Fine-grained volcanic samples were collected at different locations near the Cotopaxi volcano on the same day of its reactivation and some days afterwards in August 2015. The wind-directions charged with such materials have been determined and compared with the existing data-base allowing preventive measures about local warning. The obtained data yielded the less expected wind-directions and therefore ash precipitation in usually less affected areas towards the northern and eastern side of Cotopaxi volcano. The collected samples were studied basically for their morphology, content in minerals and rock fragments as well as the chemical composition. The results obtained from this study allowed to identify and classify the origin of the expelled material being hydroclasts of andesites and dacites with rare appearances of rhyodacites and associated regular as well as accessory minerals all being present in the conduct and crater forming part of previous eruptive activities of the volcano. A further evaluation has been performed to determine the activity stage of the volcanic behavior. The resulting interpretation appears to point to a volcanic behavior a more frequent sporadic event with a relatively low probability of lahar generation rather than any other known destructive phase, which includes a less-frequent but tremendously more catastrophic scenario.

Distinguishing among schoepite, [(UO2)8O2(OH)12](H2O)12, and related minerals by X-ray powder diffraction

1997 ◽  
Vol 12 (4) ◽  
pp. 230-238 ◽  
Author(s):  
Robert J. Finch ◽  
Frank C. Hawthorne ◽  
Mark L. Miller ◽  
Rodney C. Ewing
Keyword(s):  
Powder Diffraction ◽  
Unit Cell ◽  
Powder Diffraction File ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Fine Grained ◽  
Fine Grained Material ◽  
Two Phases ◽  
Atomic Parameters

We have calculated X-ray powder-diffraction data for schoepite, [(UO2)8O2(OH)12](H2O)12, using unit-cell and atomic parameters from the crystal structure (a14.337,b16.813,c14.781,Z=4,Dx=4.87gcm−3). Schoepite crystallizes in space groupP21cabut is strongly pseudo- centrosymmetric, and observed reflections (Irel>0.1%) conform to space groupPbca. The six strongest reflections for schoepite are [d(Å),hkl(relative intensity)] 7.365,002(100), 3.253,242(55), 3.626,240(36), 3.223,402(25), 3.683,004(20), 2.584,244(18). The calculated intensities of reflections that distinguish space groupPbcafrom space groupPbna(the space group of metaschoepite), i.e.,h0lwithhodd andleven, are weak, and may not be evident in experimental powder patterns. Theaaxis of schoepite (14.34 Å) is significantly longer than that of synthetic metaschoepite (13.98 Å), and the two phases can best be distinguished by their unit-cell parameters. However, potential overlap of the strongest reflections can make identification and unit-cell determination difficult, especially for fine-grained material. Natural samples commonly contain intergrowths of schoepite, metaschoepite, and dehydrated schoepite. The calculated powder pattern for schoepite agrees well with data reported for natural schoepite (PDF 13-241) but shows discrepancies with the data from synthesis products. Data for “synthetic schoepite” indicate that this product was a mixture. Powder data labeled “paraschoepite” in the Powder Diffraction File do not correspond to the mineral of that name.

Glauconite nodules in a Nampa pedon from Alberta

1986 ◽  
Vol 23 (3) ◽  
pp. 432-435
Author(s):  
J. A. McKeague ◽  
P. A. Schuppli ◽  
H. Kodama
Keyword(s):  
Energy Dispersive ◽  
Thin Sections ◽  
X Ray ◽  
Fine Grained ◽  
Peace River ◽  
Fine Grained Material

Nodules 0.1–0.7 mm in diameter seen in thin sections of the C horizon of a soil from the Peace River area of Alberta were analyzed. Energy-dispersive X-ray analysis (EDXRA) showed their composition (%) to be approximately MgO, 3; Al2O3, 22; SiO2, 52; K2O, 4; CaO, 2; Fe2O3, 10. X-ray analysis by Gandolfi camera showed strong glauconite lines and weak lines for quartz and kaolinite. The presence of these relatively large glauconite nodules in an otherwise fine-grained material is incompatible with its presumed lacustrine origin. Presumably, the glauconite nodules were inherited from the Smoky River shale, and the C horizon material may be residual.

scholarly journals Nanoscale Automated Quantitative Mineralogy: A 200-nm Quantitative Mineralogy Assessment of Fault Gouge Using Mineralogic

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 665 ◽  
Author(s):  
Shaun Graham ◽  
Nynke Keulen
Keyword(s):  
Primary Electron ◽  
Fault Gouge ◽  
Spectroscopy Analysis ◽  
Primary Electron Beam ◽  
X Ray ◽  
Fine Grained ◽  
Quantitative Mineralogy ◽  
Fine Grained Material ◽  
Individual Grains ◽  
Acceleration Voltage

Effective energy-dispersive X-ray spectroscopy analysis (EDX) with a scanning electron microscope of fine-grained materials (submicrometer scale) is hampered by the interaction volume of the primary electron beam, whose diameter usually is larger than the size of the grains to be analyzed. Therefore, mixed signals of the chemistry of individual grains are expected, and EDX is commonly not applied to such fine-grained material. However, by applying a low primary beam acceleration voltage, combined with a large aperture, and a dedicated mineral classification in the mineral library employed by the Zeiss Mineralogic software platform, mixed signals could be deconvoluted down to a size of 200 nm. In this way, EDX and automated quantitative mineralogy can be applied to investigations of submicrometer-sized grains. It is shown here that reliable quantitative mineralogy and grain size distribution assessment can be made based on an example of fault gouge with a heterogenous mineralogy collected from Ikkattup nunaa Island, southern West Greenland.

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