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Ravi, G. S.
- WDXRFS Method for Quantification of Heavy Minerals in Sand Samples
Authors
1 Hon Visiting Prof, Dept of Applied, Geochemistry, Osmania University, Hyderabad - 500 007, IN
2 Atomic Minerals Directorate for Exploration & Research, Department of Atomic Energy, Visakhapatnam-530 018, IN
3 Atomic Minerals Directorate for Exploration & Research, Department of Atomic Energy, Nagpur-440 001, IN
4 Atomic Minerals Directorate for Exploration & Research, Department of Atomic Energy, Hyderabad- 500 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 66, No 4 (2005), Pagination: 401-406Abstract
Estimation of industrial and strategic heavy minerals (HMs) in sands, viz, ilmenite, rutile, garnet, sillimanite, zircon and monazite, is usually carried out by Microscopic Gram-Counting (MGC) technique on heavy Liquid- and Magnetically-Separated fractions. This method is slow, laborious, Time-Consuming, costly, toxic and causes Eye-Strain. Its precision and accuracy depend on Microscope-Operator's skills in mineral identification and preparation, by microsplitting of representative portions of fractions for analysis. Instead, we are proposing here a WDXRFS-Based relatively simple, rapid, low-cost, non-toxic, eye Strain-Free and precise method. This involves (a) magnetic separation of a sand sample into 3 Sub-Samples that are magnetic at 0 4 and 1 2 A and Non-Magnetic at 1 2 A, (b) WDXRFS analysis of these for the oxides and elements in the formulae of HMs, and (c) computation of the contents of HMs, assuming their stoichiometric composition. The contents of HMs in sand samples, determined by this method, are in general agreement with that from MGC method on natural sand samples and prepared samples, with an overall error of <20%and coefficient of correlation (r) of -0 98. Furthermore, our method gives additional information on end-member composition of garnet, Th-content of monazite and proportion of Ortho- to Clino- in pyroxenes.Keywords
XRF Method, Heavy Minerals, Quantification, Beach Sands.- Rare-Earth-Element Geochemistry of Placer Monazites from Kalingapatnam Coast, Srikakulam District, Andhra Pradesh
Authors
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy BSOI Group, Visakhapatnam - 530 018, IN
2 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy EMP laboratory, AMD Complex, Hyderabad - 500 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 62, No 4 (2003), Pagination: 429-438Abstract
Monazite, a rareWrth and thorium phosphate with colour varying from colourless to different shades of yellow, green and brown, is one of the major components (0.02 to 2.93%) in the heavy mineral sands of Kalingapatnam coast of Andhra Pradesh. Subtle but significant variation in colour, shape, size, intensity of micro-fractures and radiation cracks besides provenance rocks warranted (1) detail mineral chemistry at micro-domain level involving multi-elemental qualitative and quantitative analyses, (2) geo-chemical evaluation and interpretations of micro-domain chemistry data using bi-variate (LREE, REE arid REE+Y vs. Th+Ca; P+LREE, P+REE and P+LREE+Y vs. Th+Si) and ternary (LREE, Th, Ca and P; REE, Th, Ca and P) plots and (3) regression statistics, Principal Component Analysis (PCA) and R-mode Factor Analysis (RFA) aiding principal substitutions amongst major and minor elements at structural level in representative grains of different monazites.The electron microprobe analysis data exhibit wide variation in constituent elements and compositional heterogeneity in monazite grains, especially ifl RE203 (45.40 to 63.53%), Th02 (5.69 to 23.17%) and UO2(0.00 to 2.07%) indicating their derivation from different rocks occurring in the hinterland comprising khondalites, granite gneisses and charnockites. Two types of detrital monazites identified with different REE distribution pattern are of much significance and significant correlation was observed amongst constituent major and minor elements. Evaluation of mineral chemistry data on such monazites using graphical and rMti-variate statistical techniques reveal that thorium is accommodated in its structure by charge-coupled substitution as depicted by equation viz. Th4+ + Ca2+ 2REE3+ and Th4+ + Si4+ - P5+ + REE3+ . Th and Ca content of monazite grains &re correlated inversely with light REE and positively with HREE and Y besides their minor enrichment.