| The chromite deposits associated with ophiolite complexes, Southeastern Desert, Egypt： Petrological and geochemical characteristics and mineralization |
| |
| 作者姓名： | Gehad M. Saleh |
| |
| 作者单位： | Nuclear Materials |
| |
| 摘 要： | 1 Introduction The association of massive Fe-Ni-Cu sulfides andchromite is a very unusual feature of podiformchromitites occurring in mantle tectonites of ophioliticcomplexes. It has only been described in theSoutheastern Desert, Egypt, where sulfides a…
|
| 关 键 词： | 铬铁矿沉淀 蛇绿岩复合物 东南沙漠 埃及 岩石学 |
| 收稿时间： | 22 April 2005 |
The chromite deposits associated with ophiolite complexes, Southeastern Desert, Egypt: Petrological and geochemical characteristics and mineralization |
| |
| Gehad M. Saleh.The chromite deposits associated with ophiolite complexes, Southeastern Desert, Egypt: Petrological and geochemical characteristics and mineralization[J].Chinese Journal of Geochemistry,2006,25(4):307-317. |
| |
| Authors: | Gehad M Saleh |
| |
| Institution: | (1) Nuclear Materials Authority, P.O.Box, 530 El Maadi, Cairo, Egypt |
| |
| Abstract: | The podiform chromitites occur in a well-preserved mantle sequence consisting of lherzolite-harzburgite with abundant lenses of olivine dunite. The podiform chromitite deposits are common as small and irregularly shaped masses in the Southeastern Desert (SED) of Egypt. The podiform chromitites exhibit a wide range of compositions from high Cr to high Al varieties. The Cr of chrome spinel ranges from 0.67 to 0.88 in olivine-dunite, quite similar to that of the high-Cr chromitite, whereas it is around 0.62 in lherzolite-harzburgite. Primary hydrous mineral inclusions, amphibole and phlogopite, in chrome spinel have been reported for the first time from the Pan-African Proterozoic podiform chromitites. On the other hand, petrographic and geochemical evidence suggests that podiform chromitites in the SED of Egypt were formed as a result of crystallization of mafic melts, probably of boninitic composition, the boninitic parental magmas were probably produced by a second stage of melting above a subduction zone. Three types of chromite ores can be distinguished within the SED of Egypt: (a) sulphide-poor podiform ores; (b) brecciated ores; and (c) sulphide-rich ores. Two textural types of inclusions in chromite are distinguished: (1) primary silicate inclusions generally have high Mg-number (>96), Cr and Ni, and are dominated by pargasitic amphibole, forsterite, diopside, enstatite and Na-phlogopite. A diversity of primary and secondary platinum group minerals (PGM) is described from the chromitites, including alloys, sulphides, sulpharsenides and arsenides of Ru, Os, Ir, Rh, Ni, Cu, Fe and Co; (2) in addition to primary PGM and hydrous silicates, the fluids are of low to moderate salinity, sodium-dominated aqueous solutions with complex gas contents. Variable amounts of water, hydrogen, hydrocarbons, carbon dioxides and nitrogen have been determined in inclusion-rich samples. The chondrite-normalized PGE patterns of lherzolite-harzburgite and olivine-dunite have negative Ir and Pt, and positive Pd and Au anomalies. Chromitites are homo-geneous in composition but texturally zoned on a large scale. They carry elevated IPGE, manifested in numerous, primary and secondary PGM phases. |
| |
| Keywords: | chromite deposit ophiolite complex Southeastern Desert Egypt petrological and geochemical chara-cterristics and mineralization |
| 本文献已被 CNKI 维普 万方数据 SpringerLink 等数据库收录！ |
|
