Document Details
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Document Type |
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Article In Journal |
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Document Title |
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Geology and Lithostratigraphy of the ultramafic-mafic rocks and associated mineralization, Wadi Khamal area, West-Central Arabian Shield الجيولوجية والاستراتجرافية الصخرية للصخور المافية - فوق المافية والتمعدنات المصاحبة لها، منطقة وادي خما ل، غرب وسط الدرع العربي |
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Subject |
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Geology and Lithostratigraphy of the ultramafic-mafic rocks and associated mineralization, Wadi Khamal area, West-Central Arabian Shield |
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Document Language |
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Arabic |
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Abstract |
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Field, petrography and major elements geochemistry of the
ultramafic -mafic rocks of Wadi Khamal area led to the recognition of
the following rock groups, namely: 1) ophiolitic suite, melagabbronorite
and cumulate gabbronorite to the south of Wadi Mahalah
(southern ultramafic-mafic rocks) and 2) Wadi Khamal anorthositegabbro
complex to the north.
The ophiolitic rocks in the southern area include serpentinites,
peridotites and pyroxenites. The serpentinites contain large blocks of
amphibolites, schists, gneisses, and metagabbros. These rocks were intruded
by melagabbronorite and cumulate gabbronorite. On the AFM
diagram, these rocks plot along the MgO-FeO* side in the tholeiitic
field except those of the melagabbronorite which plot within the calcalkaline
field.
The Wadi Khamal complex consists of four major units; marginal
gabbro unit, anorthosite unit, central gabbroic unit and northern
gabbronorite unit. The marginal gabbro unit and anorthosite unit have
a calc alkaline differentiation trend while those of the central gabbro
unit (olivine gabbro, melagabbronorite and Fe-Ti oxides-apatite gabbronorite)
and the northern gabbronorite show a distinct different
trend parallel to the FeO*-MgO side line and belong to the tholeiitic
differentiation trend. Based on major element geochemistry, the
southern ultramafic – mafic rocks were derived from a more mafic
liquid source rather different from magma source(s) which formed the
Khamal anorthosite-gabbro complex.
The Fe-Ti oxides-apatite gabbronorite of the central unit of the
Khamal complex hosts two main types of Fe-Ti oxide ores. 1) Massive
bands of nelsonite ore consist mainly of magnetite, ilmenite, apa120
H.M. Harbi
tite and minor amounts of silicates. It occurs in the form of bands and
lenses of variable sizes intercalated with the magnetite-ilmeniteapatite
gabbronorite, and 2) massive magnetite-ilmenite ore, which is
less abundant compared to the nelsonite. The latter occurs as dyke-like
bodies with nelsonite selvages within the anorthosite, or as bands or
lenses enclosed within the nelsonite and close to the contact with the
overlying anorthosite cap. The contact of magnetite-ilmenite ore with
the nelsonite bands is gradational. The close spatial association and
mineralogical similarities between the Fe-Ti oxides – apatite gabbronorite
and the nelsonite, as well as the variable Fe-Ti oxides/apatite ratios
suggest that the nelsonite was formed as accumulations due to in
situ fractional crystallization of Fe, Ti, P and volatiles-rich gabbroic
magma. The formation of the massive magnetite-ilmenite ore is attributed
to high fO2 and mobility which promote later injection into the |
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ISSN |
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1012-8832 |
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Journal Name |
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Earth Sciences Journal |
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Volume |
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19 |
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Issue Number |
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1 |
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Publishing Year |
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1427 AH
2008 AD |
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Article Type |
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Article |
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Added Date |
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Tuesday, October 25, 2011 |
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Researchers
| هشام محمد حربي | alharbi, hesham muhammed | Researcher | Doctorate | |
| منصور عبدالله القرني | alqarni, mansoor abdullah | Investigator | Doctorate | |
| عبدالمنعم عبدالفتاح الدجدج، | aldagdag, abdulmuneam abdulfathah | Researcher | Doctorate | |
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