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Document Type |
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Article In Journal |
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Document Title |
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Sulfide Assemblages and Metamorphic Episodes at Mahd Adh Dhahab Gold Mine, Kingdom of Saudi Arabia صحبات الكبريتيدات وأزمنة التحول في منجم مهد الذهب بالمملكة العربية السعودية |
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Subject |
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Earth Sciences |
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Document Language |
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English |
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Abstract |
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The Mahd Adh Dhahab gold mine is located in the west central
part of the Arabian Shield and has been the most productive gold mine in
Saudi Arabia in both ancient and recent times. Textural and mineralogical
features observed in the ore deposits at Mahd Adh Dhahab indicate that the
deposits have been subjected to metamorphism.
Three main effects were recognized. Recrystallization of the ores during
regional metamorphism resulted in changes mainly in the fabrics, but also in
the mineralogy, of the ores. With increasing metamorphism: a) there is a
general increase in grain size, b) growth of pyrite as porphyroblasts, and c)
presence of triple junction point texture. Deformational effects present varied
from none, through brittle cataclasis to ductile deformation. The features
observed include: a) fracturing, brecciation and mylonitization of
fine-grained sulfides and porphyroblasts, b) deformation twinning, c) folding
and disruption of cleavage traces, d) rotation of pyrite crystals, and e)
stretching and elongation of soft sulfides. Remobilization produced irregular
bodies of vein quartz and ore minerals, either within the deposits or in
their immediate country rocks. The remobilization distances are limited,
either within parent body or in restricted halo surrounding it (up to some
tens of meters). The remobilization is selective and proceeded by creep or
fluid-phase transport. The apparent order of decreasing mobility is: galena,
chalcopyrite, sphalerite, pyrite. Certain replacement phenomena observed
between the euhedral-subhedral pyrite grains and the base metal sulfides'
could be ascribed to metamorphism.
At Mahd Adh Dhahab area, successive episodes of low grade metamorphism
prevailed during a long time span. Intermittent with such pervasive
regional metamorphism, the ores were subjected to short periods of essentially
dynamic and thermal metamorphism. |
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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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5 |
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Issue Number |
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1 |
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Publishing Year |
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1412 AH
1992 AD |
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Number Of Pages |
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22 |
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Article Type |
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Article |
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Added Date |
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Sunday, October 11, 2009 |
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Researchers
| هاشم حكيم | HASHEMD. HAKIM | Researcher | | |
| عمر المهدي | OMAR EL-MAHDY | Researcher | | |
|