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Document Type |
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Article In Journal |
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Document Title |
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Geochemistry and Tectonic Evolution of the Orogenic Granitoids Associated with the Andean-Type Siham Arc, Central Arabian Shield جيوكيمياء والتطور التكتوني للجرانيتات التجبلية المصاحبة لقوس سهام من النوع الاندياني وسط الدرع العربي |
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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 syntectonic granitoids and the Al Bara batholith trondhjemite-
granite suite exposed in the Afif quadrangle, Saudi Arabia, are the major
plutonic components of the Andean-type Siham arc, developed during the
period from about 750 to 700 Ma along the western margin of the Afif terrane.
These plutonic rocks have a wide range of lithologies, from diorite to leucogranite.
They are characterized by multiple periods of plutonism and rejuvenation
during Pan-African orogeny (c. 900-550 Ma).
The syntectonic granitoids and the Al Bara batholith rocks are calc-alkaline,
I-type and metaluminous to marginally peraluminous. They are enriched in Rb,
Ba, K, La, Ce and Sr relative to Nb, Zr and Ti, suggesting their emplacement
along an active continental margin. The Al Bara batholith rocks, with the largest
variations in lithology, texture and incompatible elements’ patterns, indicate
the greater effects of Pan-African rejuvenation.
The post-tectonic Dariyah batholith granites were intruded at 585 ± 8 Ma in
the late Proterozoic (650-615 Ma) Murdama group, a back-arc basin filled up
with clastic sedimentary rocks with minor limestone and volcanic rocks. The
batholith ranges in composition from co-magmatic granodiorite to syenogranite.
Biotite granite is the abundant rock type. All lithologies of the batholith are in
part porphyritic with lack of chilled contacts. The porphyritic varieties are modeled
as mixtures of phenocrysts (presumably restite) and minimum melts. The
higher levels of Rb, Na, La, Ce and Sm, the marked depletion of Ba, Sr, and Ti
and the strong Eu negative anomaly are all indicative of in-situ fractionation of
the Dariyah rocks after intrusion into higher levels of the crust. |
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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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10 |
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Issue Number |
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1 |
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Publishing Year |
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1419 AH
1998 AD |
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Number Of Pages |
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26 |
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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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