Sem Investigation of a Lateritic Weathering Profile, Saline County, Arkansas

1993 ◽  
Author(s):  
Timothy L. Salter ◽  
Haydn H. Murray
Keyword(s):  
Weathering Profile ◽  
Sem Investigation ◽  
Saline County

Characterization of weathering profile and quality of groundwater over hard rock terrain

2021 ◽  
Vol 14 (3) ◽  
Author(s):  
Rajan Girija Rejith ◽  
Mayappan Sundararajan ◽  
Balu Gowtham ◽  
Ayyappan Balasubramanian ◽  
Joseph Francis Lawrence
Keyword(s):  
Hard Rock ◽  
Weathering Profile ◽  
Hard Rock Terrain

Thorium in crandallite-group minerals: an example from a Devonian bauxite deposit, Timan, Russia

2004 ◽  
Vol 68 (3) ◽  
pp. 489-497 ◽  
Author(s):  
L. E. Mordberg
Keyword(s):  
Crystal Lattice ◽  
Radiation Damage ◽  
Mineral Composition ◽  
Bauxite Deposit ◽  
Weathering Profile ◽  
Silicate Mineral ◽  
Fe Content ◽  
Very High ◽  
Type Substitution ◽  
Simplified Formula

AbstractA Th-rich mineral of the crandallite group has been investigated from the weathering profile of the Schugorsk bauxite deposit, Timan, Russia. It occurs within thin (up to 0.5 mm) organic-rich veinlets together with ‘leucoxene’ in the form of small shapeless grains which vary in size from 1—2 mm to 60—70 mm. Rare grains disseminated among boehmite crystals were also found. Microprobe analyses determined that the ThO2 content can be as high as 18 wt.%. The mineral composition is intermediate between crandallite CaAl3H(PO4)2(OH)6, goyazite SrAl3H(PO4)2(OH)6, Th-crandallite and svanbergite SrAl3PO4SO4(OH)6 in the beudantite group.Comparatively high contents of Fe and Si and a very high positive Th and Fe content correlation (r = +0.98) suggest that the formula of the hypothetical Th-bearing end-member is ThFe3(PO4,SiO4)2(OH)6 with Th and Si substituting for REE and Prespectively (woodhouseite-type substitution). Another possible substitution is Th4+ + Ca2+ ⇋ 2REE3+ (florencite-type). A deficiency of cations in the X site can be explained by either the presence of carbon, undetectable by microprobe, in the crystal lattice or a lack of X-site cations due to radiation damage induced by Th. Some excess of cations in the B site (Al and Fe3+) can be explained by the presence of very small boehmite and hematite inclusions on the crandallite grain surfaces. Th-rich crandallite may be the result of alteration of an unidentified silicate mineral from the parent rock with a composition close to the simplified formula Fe2+ThSiO4(OH)2.

scholarly journals A comparative study of Pleurosigma subrectum and P. acus (Bacillariophyta)

Phytotaxa ◽  
2015 ◽  
Vol 207 (3) ◽  
pp. 273
Author(s):  
FRITHJOF A.S. STERRENBURG ◽  
STUART R. STIDOLPH ◽  
EUGENIA A. SAR ◽  
Ines Sunesen
Keyword(s):  
Comparative Study ◽  
Original Data ◽  
Type Material ◽  
Diatom Species ◽  
Morphological Differences ◽  
Sem Investigation ◽  
Made In

In continuation of an earlier paper on Pleurosigma species with an (almost) non-sigmoid valve and raphe sternum, a comparative study was made in LM and SEM of Pleurosigma subrectum and P. acus. For P. subrectum, slides and a subsample of the type material were examined. For P. acus no unmounted material permitting SEM investigation is extant; a sample containing specimens fully matching the type in LM was therefore used as epitype material for SEM. The original data on striation of P. acus are emended. No morphological differences indicating separate specific status of these two taxa were observed and P. acus is therefore here designated a heterotypic synonym of P. subrectum. From the data now available, this is a very widely distributed species. The study demonstrates the indispensable role of collections for investigations on the diversity and distribution of diatom species.

The effects of oxalate-containing products on the exposed dentine surface: an SEM investigation

2001 ◽  
Vol 28 (11) ◽  
pp. 1037-1044 ◽  
Author(s):  
D. G. Gillam ◽  
N. J. Mordan ◽  
A. D. Sinodinou ◽  
J. Y. Tang ◽  
J. C. Knowles ◽  
...  
Keyword(s):  
Dentine Surface ◽  
Sem Investigation
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