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Document Type |
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Article In Journal |
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Document Title |
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A Fluid Inclusion Study on Mahd Adh Dhahab Gold Deposit, Saudi Arabia دراسة المكتنفات السائلة في تمعدن الذهب فيمهد الذهب المملكة 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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Mahd adh Ohahab. the oldest gold mine in Saudi Arabia, is
situated at the central part of the Arabian shield. It consists of an upper Proterozoic
rock sequence of andesite, agglomerate, lower rhyolitic tuff, lithic
crystal tuff, upper rhyolitic tuff and a late small porphyritic rhyolite intrusion.
Four generations of quartz veins cut through the sequence with three
generations mineralized. The area has been regionally metamorphosed to
low-grade green schist facies. To date, Mahd adh Ohahab has estimated ore
reserves of 1.45 million tons, grading 26 git Au and 92 git Ag, and a further
109,000 tons of oxide ore with an average of 77 git Au.
The majority of the fluid inclusions in quartz from quartz veins at Mahd
adh Ohahab are very small. However, primary fluid inclusions of larger
sizes (5 to 15 U) were chosen and analyzed. All the analyzed fluid inclusions
are two phase (gas and liquid) inclusions. Upon heating, they all
homogenized into a liquid phase. The final melting temperatures of ice
from the analyzed fluid inclusions fall between -0.3 and -2.2°C whereas,
the final homogenization temperatures of bulk composition fall between
+ 100 and + 380°C. The calculated compositions of the fluid are 99.21 to
99.33% of H2O and 0.67 to 0.79% of NaCI.
A microthermometric study of the fluid inclusions suggests that there are
at least two stages of quartz deposition, one at about 100-21!fC and ahother
at about 340-380°C. Quartz deposited at low temperature is considered to
be barren or contain minor amount of mineralization , whereas quartz deposited
at high temperature is postulated to be mineralized and economically
important.
It is concluded that the mineralizing fluid at Mahd adh Ohahab consisted
mainly of meteoric water with a possible minor amount of sea water. The
mineralization is postulated to have been deposited at a shallow depth in the
earth's crust to form a typical epithermal deposit. |
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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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2 |
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Issue Number |
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1 |
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Publishing Year |
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1409 AH
1989 AD |
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Number Of Pages |
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17 |
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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 | H. D. HAKIM | Researcher | | |
| منوت شنكول | M. CHINKUL | Researcher | | |
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