Ironstone occurrences in the northern part of the Bahariya Depression, Western Desert, Egypt: Geology, mineralogy, geochemistry and origin
The PhD thesis deals with two different ironstone rock types encountered in two sedimentary successions (Upper Cretaceous and Lower Cenozoic) in the northern Bahariya, Egypt. Occurrence of the two iron-bearing rock types in a same area offers an opportunity to better understanding the origin of iron...
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| Formato: | tesis doctoral |
| Fecha de publicación: | 2017 |
| País: | España |
| Recursos: | Universidad Complutense de Madrid (UCM) |
| Repositorio: | Docta Complutense |
| Idioma: | inglés |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/22343 |
| Acesso em linha: | https://hdl.handle.net/20.500.14352/22343 |
| Access Level: | acceso abierto |
| Palavra-chave: | 553.31(620)(043.2) Iron mines and mining Ironstone deposits Egypt Depósitos de hierro Egipto Mineralogía (Geología) 2506.11 Mineralogía |
| Resumo: | The PhD thesis deals with two different ironstone rock types encountered in two sedimentary successions (Upper Cretaceous and Lower Cenozoic) in the northern Bahariya, Egypt. Occurrence of the two iron-bearing rock types in a same area offers an opportunity to better understanding the origin of ironstone deposits. The ironstones occur as thin crusts within Cenomanian clastic rocks (Bahariya Formation) and as big ore bodies at three mine areas, associated to Eocene carbonate units. Analysis of the two ironstone types was carried out by means of field, petrographic, mineralogical and geochemical investigations. The ironstones contain similar iron-bearing minerals, mainly goethite and hematite, which display a variety of fabrics, i.e. concretionary, massive, stromatolitic-like, pisolithic, colloidal, reiniform aggregates, boxwork, leisegang, geode-like and brecciated. They show preferential replacement and cementation of carbonates by iron-rich minerals. Thus, the two ironstone types replaced both depositional and diagenetic carbonates (dolomites) with preservation of the structures, fabrics and thickness of their precursors. However, they exhibit some differences in textures, morphology and bed geometries but marked distinction in which refers to origin, mechanisms and timing of formation. The main mineral paragenesis in the Upper Cretaceous ironstones includes goethite, hematite, Fe-dolomite/ankerite and subordinate amounts of siderite, pyrolusite, todorokite, psilomelane and barite. In contrast, the Eocene ironstones show a more complex mineral paragenesis including goethite, hematite, quartz and subordinate amount of jarosite, alunite, barite, pyrolusite, jacobsite, romanechite, psilomelane, todorokite, apatite, palygorskite and kaolinite... |
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