Isotopic, mineralogical, and thermobarometric variations of Al-Wahbah crater (Maklaa Tameya), Kishb area, Saudi Arabia
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- 作者：Antar Abdel Wahab ; Mohamed Fouad Ghoneim ; Tamer Abu-Alam
- 关键词：Al ; Wahbah crater ; Harrat Kishb ; Saudi Arabia ; Cenozoic basalts ; Arabian–Nubian shield
- 刊名：Arabian Journal of Geosciences
- 出版年：2017
- 出版时间：January 2017
- 年：2017
- 卷：10
- 期：2
- 全文大小：
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth Sciences, general;
- 出版者：Springer Berlin Heidelberg
- ISSN：1866-7538
- 卷排序：10
文摘
The Cenozoic volcanism of western Saudi Arabia extends from southern Yemen to Jordan northward. They cover an area of nearly 180,000 km2. The rocks are dominated by alkali olivine basalts and olivine basalts. Al-Wahbah crater, a part of Harrat Kishb, represents a model occurrence to study the gneisses of these rocks. New mineral chemistry and isotopic data are presented. It aims to follow the isotopic, mineralogical, and thermobarometry variations among these volcanics. Amphiboles of the studied volcanics belong to the monoclinic calcic group. The chemistry of the amphibole crystals shows two ranges of pressure. They are 3.6–5.6 and 0.38–0.78 kbar. The Aliv values of the amphiboles are in the range of 1.202 and 1.407, indicating corresponding temperature condition of 820–920 and 620–720 °C, respectively. The feldspar of the studied samples has the composition of plagioclase, though some grains have sanidine composition. They are formed in temperature range of 975 and 400 °C. The coexisting amphiboles and plagioclases indicate two sets of pressure and temperature. They are 540–575 °C (3.5–4 kbar) and 510–525 °C (~2 kbar), respectively. Rb–Sr isochron of the whole rock yields an age of 0.867 ± 0.160 Ma with initial Sr87/Sr86 of 0.702 ± 0.00086. The low initial ratio of Sr87/Sr86 together with positive values of εNd today implies that the studied volcanics have mantle source. Meanwhile, the present isotopic data suggest extraction of juvenile magma from asthenosphere source. The present study shows that the Al-Wahbah crater rocks belong to Cenozoic basalts and indicate EM-I-like signature.