CLAY MINERALOGY IN RELATION TO GEOMORPHIC ASPECTS IN WADI EL-NATROUN DEPRESSION SOILS, WESTERN DESERTS, EGYPT

Mudstone samples from the Moreno (Upper Cretaceous-Paleocene) and Kreyenhagen (Eocene) formations are analysed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) to determine their mineralogy. Smectite (Reichweite R0) is the predominant phyllosilicate present, 48% to 71.7% bulk rock mineralogy (excluding carbonate cemented and highly bio siliceous samples) and 70% to 98% of the <2 μm clay fraction. Opal CT and less so cristobalite concentrations cause the main deviations from smectite dominance. Opal A is common only in the Upper Kreyenhagen. In the <2 μm fraction, the Moreno Fm is significantly more smectite-rich than the Kreyenhagen Fm. Smectite in the Moreno Fm was derived from the alteration of volcaniclastic debris from contemporaneous rhyolitic-dacitic magmatic arc volcanism. No tuff is preserved. Smectite in the Kreyenhagen Fm was derived from intense sub-tropical weathering of granitoid-dioritic terrane during the hypothermal period in the early to mid-Eocene; the derivation from local volcanism is unlikely. All samples had chemical indices of alteration (CIA) indicative of intense weathering of source terrane. Ferriferous enrichment and the occurrence of locally common kaolinite are contributory evidence for the intensity of weathering. Low concentration (max. 7.5%) of clinoptilolite in the Lower Kreyenhagen is possibly indicative of more open marine conditions than in the Upper Kreyenhagen. There is no evidence of volumetrically significant silicate diagenesis. The main diagenetic mineralisation is restricted to low-temperature silica phase transitions.

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THE CLAY MINERALS IN SOME BRITISH COLUMBIA SUBSOILS

Canadian Journal of Soil Science ◽

10.4141/cjss62-039 ◽

1962 ◽

Vol 42 (2) ◽

pp. 296-301 ◽

Cited By ~ 2

Author(s):

J. S. Clark ◽

J. E. Brydon ◽

H. J. Hortie

Keyword(s):

British Columbia ◽

Diffraction Analysis ◽

Clay Minerals ◽

Clay Mineralogy ◽

X Ray Diffraction ◽

The South ◽

Parent Materials ◽

X Ray ◽

Northeastern Part ◽

Montmorillonitic Clay

X-ray diffraction analysis was used to identify the clay minerals present in fourteen subsoil samples that were selected to represent some more important clay-bearing deposits in British Columbia. The clay mineralogy of the subsoils varied considerably but montmorillonitic clay minerals tended to predominate in the water-laid deposits of the south and illite in the soil parent materials of the Interior Plains region of the northeastern part of the Province.

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Weathering mineral facies in altered granites: The importance of local small-scale equilibria

Mineralogical Magazine ◽

10.1180/minmag.1979.043.326.08 ◽

1979 ◽

Vol 43 (326) ◽

pp. 261-268 ◽

Cited By ~ 23

Author(s):

A. Meunier ◽

B. Velde

Keyword(s):

Chemical Composition ◽

Alkaline Earth ◽

Clay Mineralogy ◽

Small Scale ◽

Chemical Potentials ◽

Silica Activity ◽

Section Size ◽

Alkaline Earths ◽

Last Stage ◽

Rock Alteration

SummaryClassical clay mineralogy determinations and electron microprobe analyses of weathering minerals developed in altered two-mica granites indicate that the chemical forces that produce new minerals are often constrained to small volumes, frequently on the scale of a mineral grain or contact between two grains in the granite.Chemical potentials such as pH, alkali and alkaline earth and silica activity in the altering aqueous solutions provoke a destabilization of pre-existing minerals, which recrystallize locally to give a new multimineral product. The chemical composition of the new phases is largely governed by the relative concentrations of the elements present in the former minerals.Three mineral facies were observed in the weathered granites: initially a sericite-beidellitic type, then a beidellite-kaolinitic type, and finally a last stage kaolinite-oxide facies assemblage. The position of each facies is not restricted to a given depth in the profile but the relative proportions of each facies found in a thin-section size sample change towards the kaolinite-oxide facies.The global rock chemistry reflects the type facies predominant in each sample. The first two facies are roughly silica conservative while the kaolinite-oxide facies loses silica as well as alkali and alkaline earths.Geochemical and clay mineral studies of rock alteration should consider problems of mineral genesis at very localized sites.

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Clay Mineralogy and Geochemistry of the Pockmarked Surface Sediments from the Southwestern Xisha Uplift, South China Sea: Implications for Weathering and Provenance

Geosciences ◽

10.3390/geosciences11010008 ◽

2020 ◽

Vol 11 (1) ◽

pp. 8

Author(s):

Mei Zhang ◽

Hongfeng Lu ◽

Qing Chen ◽

Gayan Bandara ◽

Hui Zhang ◽

...

Keyword(s):

South China Sea ◽

Clay Minerals ◽

South China ◽

Surface Sediments ◽

Northern South China Sea ◽

Clay Mineralogy ◽

Xrd Analysis ◽

Average Weight ◽

X Ray ◽

China Sea

In the northern South China Sea, pockmarks are widely distributed on the seabed offshore on the southwestern Xisha Uplift. The mineralogy and geochemistry of the clay minerals and surface sediments from the pockmark field were identified using X-ray diffraction (XRD) analysis and X-ray fluorescence (XRF) analysis to trace the provenance, weathering, and sediment transportation system in the area. The clay minerals are primarily comprised of illite, smectite, kaolinite, and chlorite, showing a distribution of average weight percentages of 35%, 35%, 18%, and 13%, respectively. Based on the surrounding fluvial drainage basins and various transport mechanisms (current or monsoon), illite and chlorite primarily originate from rivers in Taiwan and the Mekong and Red Rivers. Kaolinite primarily originates from the Pearl River, and smectite derived from the Luzon arc system is primarily transported by surface currents with significant influence from the Kuroshio intrusion.

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