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Document Type |
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Article In Journal |
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Document Title |
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Geology of the Ishmas Gold Prospect, Kingdom of Saudi Arabia جيولوجية تمعدن الذهب بمنطقة إشماس 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 area of the Ishmas gold prospect is underlain by the Upper
Proterozoic rocks of the Arabian Shield. These are here interpreted, in
part, to represent an ophiolitic assemblage and include serpentinized
websterite and other altered ultramafics, cumulate and massive gabbros,
metabasalts, metarhyolites and related rocks, quartzites, metadolomitic
limestone and skarn, all intruded by granite bodies and dykes. The contacts
between the different rock units are generally tectonic. The volcanic rocks
are bimodal in nature, and were formed from a low K-tholeiitic magma in a
spreading ocean floor environment. The gabbros are of an oceanic type and
the ultramafic rocks are ophiolitic cumulates, characterized by low contents
of lithophile elements. So, on the basis of this, and other field observations,
it is believed that these rocks represent an ophiolite sequence, autochthonous
in nature, formed as a result of rifting and subsequent closure of an
ocean.
Rocks of the area are cut by faults striking in a number of directions,
namely: N-S, 45-60,140-160 and 155.
Quartz veins in the area are believed to represent three stages of vein formation;
an early stage (striking N-S), an intermediate stage (striking 140-
160 and 45-60) and a late stage (striking 115). The intermediate stage of vein
formation was the most important gold-forming episode.
The gold deposits are probably related spatially to the Najd fault system.
They are hydrothermal, epigenetic precious metal vein-type (bonanza) deposits.
The source of gold and associated chalcophile elements is most probably
the altered ultramatic rocks. |
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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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1 |
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Issue Number |
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1 |
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Publishing Year |
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1408 AH
1988 AD |
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Number Of Pages |
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14 |
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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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