Accurate quantification of the modal mineralogy of rocks when image analysis is difficult

2002 ◽  
Vol 66 (1) ◽  
pp. 189-200 ◽  
Author(s):  
P. F. Schofield ◽  
K. S. Knight ◽  
S. J. Covey-Crump ◽  
G. Cressey ◽  
I. C. Stretton
Keyword(s):  
Image Analysis ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Mineralogical Composition ◽  
Cost Effective ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Fine Grained ◽  
Neutron Powder Diffraction Data ◽  
Residual Strains

AbstractThe volume proportions of the mineral phases in two strongly deformed olivine-orthopyroxene rocks have been quantified by whole-pattern stripping of fixed geometry X-ray powder diffraction data. The results were compared with the phase proportions as determined by Rietveld refinement of time-of-flight neutron powder diffraction data, and were shown to be in excellent agreement. The X-ray technique not only provides a very rapid and cost-effective method of determining phase proportions, but it also circumvents several of the problems associated with obtaining this information by image analysis. Moreover, the technique is particularly advantageous in strongly textured rocks or in rocks that contain significant residual strains. As such it offers a powerful technique for analysing the mineralogical composition of fine-grained and/or deformed experimental run products, which makes it of considerable potential for monitoringin situthe progress of mineral reactions during laboratory experiments.

scholarly journals Pressing the Limits of Rietveld Refinement

1988 ◽  
Vol 41 (2) ◽  
pp. 297 ◽  
Author(s):  
RA Young
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Site Occupancy ◽  
The Other ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Refinement Method

Two examples are given, one with X-ray data and one with netltron data, of the determination of structural detail which appear to be at the edge of current possibility for the Rietveld structure-refinement method. In the first example, 2�2 wt% Sb substituted in CalO(P04)6F2 was located. X-ray powder diffraction data collected with special attention to intensity precision and scale constancy were used. The problem was solved through comparison of intra-sample site-occupancy ratios between Sb-doped and undoped samples. In the second example, high quality, high resolution neutron powder diffraction data were required. The problem was to distinguish between two subtly different models of kaolinite for which the R-weighted-pattern values differed only by 2 or 3 units in the third digit and, particularly, to understand the basis for the consistent programmatic choice of one of the models (PI) over the other. The answer was found in the calculated and 'observed' intensities for (h+ k)-odd reflections; although they were very small, less than 1% of the intensities of the main reflections, many of them were distinctly nonzero. Even though these reflections were not separately observable, because of overlap and small size, they nonetheless correlated with one model sufficiently better than the other to produce the consistent choice.

scholarly journals Quantitative Phase Analysis of Skarn Rocks by the Rietveld Method Using X-ray Powder Diffraction Data

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 894
Author(s):  
Yana Tzvetanova ◽  
Ognyan Petrov ◽  
Thomas Kerestedjian ◽  
Mihail Tarassov
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Quantitative Phase Analysis ◽  
Chemical Compositions ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Fine Grained ◽  
Variable Chemical

The Rietveld method using X-ray powder diffraction data was applied to selected skarn samples for quantitative determination of the present minerals. The specimens include garnet, clinopyroxene–garnet, plagioclase–clinopyroxene–wollastonite–garnet, plagioclase–clinopyroxene–wollastonite, plagioclase–clinopyroxene–wollastonite–epidote, and plagioclase–clinopyroxene skarns. The rocks are coarse- to fine-grained and characterized by an uneven distribution of the constituent minerals. The traditional methods for quantitative analysis (point-counting and norm calculations) are not applicable for such inhomogeneous samples containing minerals with highly variable chemical compositions. Up to eight individual mineral phases have been measured in each sample. To obtain the mineral quantities in the skarn rocks preliminary optical microscopy and chemical investigation by electron probe microanalysis (EPMA) were performed for the identification of some starting components for the Rietveld analysis and to make comparison with the Rietveld X-ray powder diffraction results. All of the refinements are acceptable, as can be judged by the standard indices of agreement and by the visual fits of the observed and calculated diffraction profiles. A good correlation between the refined mineral compositions and the data of the EPMA measurements was achieved.

BaCeN2, ein Bariumnitridocerat(IV) mit einer Struktur vom anti-TiP-Typ / BaCeN2, a Bariumnitridocerate(IV ) with a Structure of the anti-TiP Type

1994 ◽  
Vol 49 (9) ◽  
pp. 1169-1174 ◽  
Author(s):  
Oliver Seeger ◽  
Joachim Strähle
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
Type Structure ◽  
Stoichiometric Ratio ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Moisture Sensitive ◽  
Trigonal Prismatic

Reaction of Ba3N2 with CeN in the stoichiometric ratio 1:3 at 850 °C under an atmosphere of N2 followed by quenching yields air and moisture sensitive BaCeN2. The product crystallizes isotypically to β-RbScO2 with the anti-TiP type structure in the hexagonal space group P63/mmc with a = 365.06(2), c = 1266.03(3) pm, Z = 2. The structure was determined using X-ray and neutron powder diffraction data. In the structure the Ba2+ cations occupy trigonal prismatic holes with distances Ba-N = 288(1) pm while the Ce atoms are in octahedral positions with distances C e -N = 242.4(8) pm

ChemInform Abstract: Structure of Y4O(OH)9NO3 from X-Ray and Neutron Powder Diffraction Data.

ChemInform ◽  
2010 ◽  
Vol 23 (26) ◽  
pp. no-no
Author(s):  
A. N. CHRISTENSEN ◽  
M. NIELSEN ◽  
K. P. J. O'REILLY ◽  
T. WROBLEWSKI
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Powder Diffraction ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Abstract Structure
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