Stability of remanence and paleomagnetic studies of some chromite ores from Barramiya and Allawi occurrences, Eastern Desert, Egypt

Refai, E.; Wassif, Nadia A.; Shoaib, A.

doi:10.1016/0012-821x(89)90091-5

Cited by 11 publications

(4 citation statements)

References 10 publications

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“…The thermal demagnetization curve is typical of magnetite held magnetization, with a maximum unblocking temperature of 575øC (Figure 2, ST45B). Chromite, a ferrimagnetic mineral, is also an efficient carrier of stable remanence [Refai et al, 1989] but much weaker than magnetite.…”

Section: Resultsmentioning

confidence: 99%

Chemical remanent magnetism related to the Dead Sea Rift: Evidence from Precambrian igneous rocks of Mount Timna, southern Israel

et al. 1993

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A paleomagnetic and mineralogical study of shallow intrusive basement rocks on Mount Timna (Arabo Nubian Massif in Sinai) shows that although all the igneous rocks are of late Precambrian age, a remanent magnetic direction similar to the subrecent field (Miocene to present) is identified in samples of quartzmonzodiorite, monzodiorite, dikes of various composition, and altered gabbro. The average direction of these rock units is (D/I) 359ø/41 ø, •x95=4 ø, and the pole is at 83.6øN,223.2øE. The "subrecent" direction appears both as an overprint direction and as the sole stable vector in dolerite, rhyolite, and andesitc dikes. The magnetic mineral assemblage of these rocks includes secondary minerals, such as hematite and goethite, which formed by oxidation and hydration of the original magnetite and Ti-magnetite. The subrecent direction is interpreted to have been acquired as a chemical remanent magnetization (CRM) by hydrothermal activity and circulation of thermal brines through fractures related to the adjacent Dead Sea transform. The hydrothermal activity occurred before uplift and erosion exposed the basement rocks, i.e., in the middle Miocene, during the early stages of activity of the Dead Sea rift. The north trending declinations indicate that Mount Timna has not rotated about a vertical axis after acquisition of the CRM, a conclusion that confirms a previous structural analysis. An absence of reversals implies that the duration of CRM acquisition was probably less than --1 m.y., the maximum length of normal polarities since the Oligocene. Other field directions were found in an alkali granite (one site, 343ø/14 ø, 0•95=22ø), in a dolerite dike (one site, 318ø/0% 0•95=2 ø) and in a gabbro (seven sites, 303ø/56% 0•95=6ø). The field direction in the granite is similar to that for Early Cretaceous, a time of magmatic activity in Timna. Northwest trending declinations and shallow inclinations found in several samples of the dikes are carried by unaltered parts of the rocks. These directions are interpreted as late Precambrian-Early Cambrian in age, indicating a near-equatorial location of the region at that time. Nubian Massif has been attached to Africa since the beginning

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Section: Resultsmentioning

confidence: 99%

Chemical remanent magnetism related to the Dead Sea Rift: Evidence from Precambrian igneous rocks of Mount Timna, southern Israel

et al. 1993

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“…Therefore, at the Barramiya, Abu Marwa, and Abu Mireiwah sites in Egypt, we have analyzed the aeromagnetic data to delineate the alteration zones, geological structures, geological boundaries, and depth to the rock of conceivable basement mineralization zones that are linked to hydrothermally altered zones. The study area has been subjected to previous geophysical studies, including paleomagnetic studies on some chromite ores [9] and others using aeromagnetic data to create the curie point depth map by means of the spectral analysis technique [10], but it is the first time that the aeromagnetic data has been analysed using the new Centre for Exploration Targeting (CET) grid analysis technique to map out geological structures and highlight the best places to look for minerals.. The edges of the sources were detected by many authors, who introduced the new techniques based on the ratios of gradients of the gravity data, where the edge detection filter was based on the ratio of the derivatives of the THG and called the logistic function of the total horizontal gradient (THG) [11,12] have used a novel filter called Balanced Horizontal Gradient for the magnetic data from central India to improve the subsurface bodies' edges, which circumvent the restrictions of traditional filters.…”

Section: Introductionmentioning

confidence: 99%

Detection of Mineralization Zones Using Aeromagnetic Data

et al. 2022

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Every day, mining corporations grow and develop over Egypt’s Eastern Desert in search of gold, silver, and other metals. Mineral resources in Egypt are a powerful tool for increasing national income. In this study, we are interested in mineral exploration, such as gold and porphyry deposits, using aeromagnetic data, applying various processing techniques such as First Vertical Derivative, Total Horizontal Gradient, Analytical Signal, Tilt Derivative, and the center of exploration targeting. The study area is located at the Central Eastern Desert, which includes the Barramiya, Abu Marwa, and Abu Mireiwah regions. The analysis of the delineated structural trends shows that the N–S, NW–SE, and NE–SW are the most effective directions for managing deposits in the investigated area. A minor trend is also shown in the E–W direction and corresponds to the alteration zones reported by geology and prior investigations. Mineralization zones occur most frequently at the contact between ophiolitic serpentinite, sediments, and other rock types. This study intends to add more about the use of the recently developed technology of CET grid analysis for mineral exploration and structural interpretation across the Central Eastern Desert. The CET porphyry analysis map shows locations where several occurrences of porphyry deposits are probable. The newly discovered spots are similar to the area’s usual deposit sites. This study proves that aeromagnetic data are significant in mineral exploration since they are useful for the discovery of the structure and shear zones controlling the mineralization zones.

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“…Mukherjee (L962) also report moderate to high magnetism in chromite ores from Nausahi, India. The behaviour of both these ores is indistinguishable from that of pseudo-single domain magnetite grains (Refai et al, 1989).…”

Section: Chromitesmentioning

confidence: 86%

Ice Induced Sea Level Change in the Late Neogene

Wilson¹

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<p>Two independent records of latest Neogene (2,0 - 6.0 Ma.) glacioeustasy are presented, one of Antarctic ice volume from East Antarctica and the other of eustatic sea level from the South Wanganui Basin, New Zealand. Glacial deposits in the Transantarctic Mountains (Sirius Group) and sediment at the Antarctic continental margin provide direct evidence of Antarctic ice sheet fluctuation. Evidence for deglaciation includes the occurrence of Pliocene marine diatoms in Sirius Group deposits, which are sourced from the East Antarctic interior. K/Ar and 39Ar/40Ar dating of a tuff in the CIROS-2 drill-core confirms their Pliocene age at high latitudes (78 [degrees] S) in Antarctica. Further evidence for Antarctic ice volume fluctuation is recorded by glaciomarine strata from the Ross Sea Sector cored by the CIROS-2 and DVDP-11 drill-holes. Magnetostratigraphy integrated with Beryllium-10, K/Ar and 39Ar/40Ar dating provides a high resolution ([plus or minus] 50 k.y.) chronology of events in these strata. In the Wanganui Basin, New Zealand, a 5 km thick succession of continental shelf sediments, now uplifted, records Late Neogene eustatic sea level fluctuation. In the Late Neogene, basin subsidence equalled sediment input allowing eustatic sea level fluctuation to produce a dynamic alternation of highstand, transgressive, and lowstand sediment wedges. This record of Late Neogene sea level variation is unequalled in its resolution and detail. Magnetostratigraphy provides a high resolution chronology for these sedimentary cycles as well as magnetic tie lines with the Antarctic margin record in McMurdo Sound. These two independent records of Late Neogene glacioeustasy are in good agreement and record the following history: The Late Miocene and Late Pliocene are times of low 'base level' glacioeustasy (here termed glacialism, rather than glacial), with growth of continental-scale ice sheets on the Antarctic continent causing a lowering of global sea level. The Early Pliocene was a time of high 'base level' glacioeustasy (here termed interglacialism, rather than interglacial), driven by collapsing of continental-scale ice sheets to local and subcontinental ice caps. The middle Pliocene is marked by a move into glacialism with an increasing 'base level' of glacioeustatic fluctuation. Higher-order glacial advances and associated eustatic sea-level lowering occurred at approximately 3.5 and 4.3 Ma., separating the Early Pliocene into 3 sea-level stages. Still higher-order glacioeustatic fluctuations are recognised in this study, with durations of 50 Ka. and 100 - 300 Ka.. The 100 - 300 Ka. duration cycles are prominent during interglacialisms, and the 50 Ka. duration cycles are prominent during glacialisms. These shorter duration fluctuations in glacioeustasy have already been recognised as glacial/deglacial cycles from detailed studies of the Quaternary. Four orders of sea-level fluctuation are recognised within the Late Neogene, these are of approximately 0.05 Ma., 0.1-0.3 Ma., 2 Ma., and 4 Ma. in duration. The 2 Ma. and 4 Ma. duration cycles are subdivisions of the third order cyclicity recognised by Vail et al. (1991) (referred to here as cyclicity orders 3a and 3b). The 0.1-0.3 Ma. duration cycles are a subset of the fourth order cyclicity recognised Vail et al. (1991), and the 0.05 Ma. Duration cycles are a subset of the 5 th order cyclicity recognised by Vail et al. (1991). 3a, 3b and 4 th order sea level fluctuations are driven by fluctuations in the volume of the Antarctic Ice Sheet. Fifth order sea level fluctuations are also suggested to be at least partially driven by fluctuations in the volume of the Antarctic Ice Sheet. Milankovitch cyclicities in glacioeustasy (<100 Ka., fifth order cyclicity) are prominent in the geologic record at times when there is large scale glaciation (glacialism) of the Antarctic Continent (e.g. for the Pleistocene). Conversely, at times when the Antarctic continent is in a deglaciated state (deglacialism) fourth order cyclicity is more prominent, with Milankovitch cyclicities present at a parasequence level.</p>

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Stability of remanence and paleomagnetic studies of some chromite ores from Barramiya and Allawi occurrences, Eastern Desert, Egypt

Cited by 11 publications

References 10 publications

Chemical remanent magnetism related to the Dead Sea Rift: Evidence from Precambrian igneous rocks of Mount Timna, southern Israel

Chemical remanent magnetism related to the Dead Sea Rift: Evidence from Precambrian igneous rocks of Mount Timna, southern Israel

Detection of Mineralization Zones Using Aeromagnetic Data

Ice Induced Sea Level Change in the Late Neogene

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