Petrogenesis of Neoproterozoic Ultramafic Rocks, Wadi Ibib–Wadi Shani, South Eastern Desert, Egypt: Constraints from Whole Rock and Mineral Chemistry
| Autor: | Farrage M. Khaleal, Gehad M. Saleh, El Saeed R. Lasheen, Mamdooh Alwetaishi |
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| Rok vydání: | 2021 |
| Předmět: |
Technology
QH301-705.5 partial melting QC1-999 Geochemistry serpentinization Pyroxene engineering.material element mobility Ultramafic rock General Materials Science Biology (General) QD1-999 Instrumentation Petrogenesis Fluid Flow and Transfer Processes Peridotite Olivine Physics Process Chemistry and Technology General Engineering Partial melting Engineering (General). Civil engineering (General) Computer Science Applications Chemistry engineering Chromite TA1-2040 forearc affinity Pseudomorph Geology |
| Zdroj: | Applied Sciences Volume 11 Issue 22 Applied Sciences, Vol 11, Iss 10524, p 10524 (2021) |
| ISSN: | 2076-3417 |
| DOI: | 10.3390/app112210524 |
| Popis: | This contribution deals with new geology, petrography, and bulk-rock/mineral chemistry of the poorly studied ultramafics of Wadi Ibib–Wadi Shani (WI–WS) district, South Eastern Desert, Egypt. These ultramafics are dismembered ophiolitic rocks that can be subdivided into serpentinites and serpentinized peridotites. Primary minerals such as olivine and pyroxene are absent in serpentinites, but relics of them occur in serpentinized peridotites. Pseudomorph after olivine is indicated by common hourglass textures with less mesh, whilst schistose bastites reflect a pyroxene pseudomorph. Chromite can be subdivided into Cr-spinel and Al-spinel. Cr-spinel ranges from chromite to magnesochromite in composition, whereas Al-spinel belongs to the spinel field. Cr-spinel includes YCr (Cr/(Cr+Al+Fe+3), YAl (Al/(Al+Cr+Fe+3), and YFe+3 (Fe+3/(Fe+3+Al+Cr), similar to forearc peridotite, whilst Al-spinel is more similar to abyssal peridotite, and may be formed during inanition of subduction processes in proto forearc environments. The main secondary minerals are tremolite, talc, and chlorite—which is subdivided into pycnochlorite and diabantite—and their temperature ranges from 174 to 224 °C. The examined rocks had undergone high partial melting degrees (> 25%), as indicated by the Cr# of their unaltered cores (Cr-spinel, > 0.6), whole rocks (Al2O3, SiO2, CaO, and MgO), trace and REEs, depleted Na2O, Al2O3, and Cr2O3 of clinopyroxene, and high forsterite content ((Fo = 100 Mg/Mg + Fe), av. 95.23 mol%), consistent with forearc settings. |
| Databáze: | OpenAIRE |
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