Jabal Hamra REE-mineralized silexite, Hijaz region, Kingdom of Saudi Arabia

Jackson, Norman; Douch, Colin J.

doi:10.1016/s0899-5362(86)80088-4

Cited by 12 publications

(3 citation statements)

References 7 publications

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“…The altered zone is in irregular and gradational contact against the adjacent quartz alkali-feldspar syenite. Jackson and Douch (1986) recorded a sharp, brecciated and sheared contact between the altered granite and the surrounding quartz alkali-feldspar syenite. However, field observations and further petrographic and chemical studies suggest that the altered granite is not magmatic rock but a type of hydrothermal alteration.…”

Section: Jabal Al Hamramentioning

confidence: 99%

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

Qadhi

2007

Central European Geology

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The Jabal Hamra (538 Ma) and Jabal Abu ad Dud plutons in northeast Saudi Arabia are epizonal bodies consisting of alkali feldspar granite and alkali feldspar syenite. Fracture-controlled zones of highly altered granites are recorded along the margins of the plutons. The granites intrude metamorphosed volcano-sedimentary successions of the Matran Formation. The rocks of the two plutons are chemically indistinguishable. They are characterized by above-average Th, Nb, Y, Ta, Hf and Zr, very low CaO, TiO 2 , MgO, FeO and MnO, and by high contents of rare earth elements (REE). Tectonic discrimination diagrams suggest an intra-plate environment, with many geochemical and mineralogical features resembling post-orogenic A-type granites. Numerous local and regional geologic constraints indicate that the plutons were intruded in an extension-related setting following the cessation of Neoproterozoic arc-related magmatism. Geochemical data are consistent with their derivation by partial melting of depleted crust followed by fractional crystallization of feldspars, ferromagnesian minerals and REE-rich accessory phases. The radiogenic isotope data [eNd (T) values are +3.5 to +4.2] indicate that the granite magma was generated from a 'juvenile' source, which is typical of the rocks making up most of the Arabian-Nubian Shield. Rare-metal mineralization is associated with the fracture-controlled alteration zones that occur at Jabal Al Hamra and Jabal Abu ad Dud. The altered rocks are characterized by higher TiO 2 , Fe 2 O 3 , SiO 2 and lower Al 2 O 3 , CaO, Na 2 O, than the unaltered rocks. They show high and wide range in the total REE contents (804-15579 ppm), , Nb (51-3483 ppm), Hf (13-368 ppm), Zr (394-14887 ppm), Th (16-572 ppm) and U (4-143 ppm). Field observations and further petrographic and chemical studies suggest that the altered rocks and the rare metal enrichment are the products of hydrothermal-metasomatic alteration of the quartz alkali feldspar syenite and the alkali feldspar granite. The rare-metal enrichment was explained by orthomagmatic fluid transport of these elements as fluoride complexes, and their subsequent deposition as a result of mixing with externally derived Fe-rich fluids.

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Section: Jabal Al Hamramentioning

confidence: 99%

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

Qadhi

2007

Central European Geology

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“…Jabal Hamra and Said, Higaz region, Saudi Arabia, Jackson and Douch (1986), Hackett (1986), and Harris et al (1986); Blachford Lake deposits, Trueman et al, (1988);Tundulu complex, Malawi, Ngwenya (1994)). The ore minerals occur either as impregnations or fracture fillings as well as small veinlets.…”

Section: Gara El Hamra (Gh) Syenite-granitementioning

confidence: 99%

An Overview on the REE-Mineralized Alkaline Granites in Egypt, with Special Reference to the Abu Khruq and Gara El Hamra Bodies

Abdalla¹

2006

Resource Geology

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. The REE‐mineralized alkaline granites in Egypt are divided into the following three classes: (1) Mesozoic, anorogenic nepheline syenite ring complexes with REE amounting up to 1.3 %, particularly in their fenitized parts (e.g. Abu Khruq), (2) an orogenic peralkaline syenite‐granite, composed of i) Zr, Nb, ‐ REE, and Th‐enriched peralkaline granite‐syenite complexes with REE amounting up to 0.5 % (e.g. Um Hibal, Tarbite North and South, Gharib, and Zarget Naam) and ii) Y, Th, HREE, and P‐enriched post‐Cretaceous peralkaline complexes that intrude the Phanerozoic rocks of the Southwestern Desert with REE amounting up to 2 % (e.g. Gara El Hamra), and (3) upper Proterozoic, post‐orogenic siderophyllite alkali feldspar granite with REE amounting up to 0.8 %, particularly in their apical miarolitic pegmatites and albitized zones (e.g. Kadabora‐Abu Dob and Um Naggat). Special attention is given to the Abu Khruq and Gara El Hamra granitic bodies.

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“…ring complexes; Harris, 1985) and many of them are rare-metal-bearing (Küster, 2009). For example, economic raremetal grades are encountered at Ghurayyah in the Midian region (Elliott et al, 1999), subeconomic rare-metal concentrations are found in the Jabal Tawlah microgranite sill (Drysdall et al, 1984;Drysdall and Douch, 1986), the Jabal Hamra silexite (Drysdall et al, 1984;Jackson and Douch, 1986), the Jabal Sa'id aplite/pegmatite (Hackett, 1986), and the Umm al Birak aegirine microgranite (Drysdall et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

Geochemistry of the Late Neoproterozoic Hadb adh Dayheen ring complex, Central Arabian Shield: Implications for the origin of rare-metal-bearing post-orogenic A-type granites

Moghazi

Harbi

Ali

2011

Journal of Asian Earth Sciences

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Jabal Hamra REE-mineralized silexite, Hijaz region, Kingdom of Saudi Arabia

Cited by 12 publications

References 7 publications

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

An Overview on the REE-Mineralized Alkaline Granites in Egypt, with Special Reference to the Abu Khruq and Gara El Hamra Bodies

Geochemistry of the Late Neoproterozoic Hadb adh Dayheen ring complex, Central Arabian Shield: Implications for the origin of rare-metal-bearing post-orogenic A-type granites

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