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Artificial recharge schemes in water resources development in Oman
Published in Jos H. Peters, Artificial Recharge of Groundwater, 2020
Nasir Mohammad Al Battashi, Syed Rashid Ali
The eastern part of the catchment comprises ophiolite rocks which are mainly harzburgite and dunite. These rocks are extensively fractured and weathered in the gabbroic zone. The rocks in the central part and near the recharge dam are of sedimentary origin, consisting of oolitic, litholoclastic, silicified to marly limestone, red and, white cherts. Hard rocks in general are not believed to be the potential aquifers. The alluvium consist of unconsolidated / semi-consolidated clastic deposits, occupying the areas in-between the wadi channels and plain extending downstream to the dam. The alluvial deposits near the dam have a limited thickness that hardly exceeds 40 m and consists of inter -layers of cemented to non-cemented gravel, that form the aquifer. The depth to water ranges from 13.5 to 17 m below land surface, reducing to 17 to 22 m in dry season. The aquifer’s transmissivity values obtained from past studies ranged from 200 to 700 m2 / day. However transmissivity in channel deposits can exceed 7000 m2/ day. This variation is due to difference in degree of cementation and the thickness of the aquifer at individual sites. The storage coefficient values range from 0.01 to 0.02. The average thickness of the aquifer is 18 m. The hydraulic gradient is 0.007.
Early Proterozoic Magmatism and Geodynamics — Evidence of a Fundamental Change in the Earth’s Evolution
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
In the character of the section and the composition of the rocks, the Rustenburg Layered Suite of the Bushveld Complex is similar to the Stillwater and Monchetundra intrusions, although in contrast to these, it has preserved its upper zone. Its thickness varies between 7 and 9 km. The suite can be divided into four zones. The Lower Zone consists of ultramafic rocks, including dunite, harzburgite and bronzitite. Above comes the Critical Zone, composed of norite, anorthosite and bronzitite, containing about 20 chromite seams, each about 2 m thick. The well-known Merensky Reef, the world’s largest platinum deposit, occurs in the upper part of the Critical Zone.
Geology of Chromite deposits in the Arabian Shield, Saudi Arabia
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
O. R. El-Mahdy, A. M. Al-Shanti
Host rocks to chromite mineralisation are mostly dunite and, to a lesser extent, harzburgite. In cases where chromite occurs in harzburgite, there is always a small envelope of dunite surrounding the chromite occurrences, followed outwardly by harzburgite. All these rocks are moderately to highly altered to serpentinite, and are strongly sheared and schistose. Carbonatized serpentinites occur in areas of intense deformation. The serpentinites contain 3-10% opaques (titanomagnetite, ilmenite and chromite) occurring either as disseminations or thin parallel bands.
Composition and Miocene deformation of the lithospheric mantle adjacent to the Marlborough Fault System in North Canterbury
Published in New Zealand Journal of Geology and Geophysics, 2023
Sophie J. Bonnington, James M. Scott, Marshall C. Palmer, Nadine P. Cooper, Malcolm R. Reid, Claudine H. Stirling
The Little Lottery Intrusives are a suite of alkaline intraplate intrusions that, at the field site, occur as large grey columnar-jointed nephelinite boulders within the river and as scree deposits on the hillside (Figure 2A). The samples in the river are typically very fresh and comprise olivine microphenocrysts set in a sideromelane groundmass with clinopyroxene and Ti-oxides. Coote (1987) has an unpublished K-Ar analysis of 15.1 ± 0.7 Ma on a glass-bearing sample from this location. The nephelinite boulders and scree contain abundant ultramafic xenoliths (Table 1; Figure 2B). When plotted on the ternary olivine-orthopyroxene-clinopyroxene ultramafic rock classification (Le Bas and Streckeisen 1991), 23 of the 40 analysed samples are classified as peridotite and 17 are pyroxenite, although there is gradation between groups (Figure 3). Of these, the peridotites comprise dunite, harzburgite, lherzolite and wehrlite. Most pyroxenites have an olivine-websterite composition, although four samples are orthopyroxenite.