Chemical composition of crustal xenoliths from southwestern Syria: Characterization of the upper part of the lower crust beneath the Arabian plate |
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| Authors: | Abdulrahman Al-Safarjalani Sobhi Nasir Thomas Fockenberg Hans-Joachim Massonne |
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| Institution: | 1. Department of Soil Sciences, Damascus University, Damascus, P.O. Box 30621, Syria;2. Department of Earth Sciences, Sultan Qaboos University, P.O. Box 36, Oman;3. Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany;4. Institut für Mineralogie und Kristallchemie, Universität Stuttgart, Azenbergstr. 18, D-70174 Stuttgart, Germany |
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| Abstract: | The chemical bulk rock composition of 37 xenoliths, brought from depths of 25–30 km to the surface by penetrating Cenozoic alkali basaltic magma, from the Shamah Harrat, southwestern Syria, was determined by XRF spectroscopy. The geochemical character of these xenoliths points to original marls and within-plate igneous rocks. To obtain the mean chemical composition of the corresponding upper portion of the lower crust, the compositions of the 37 xenoliths were averaged and a leucogranitic and upper crustal component was added to account for assimilation by the Cenozoic magmas. This mean is more basic (SiO2—50.5 wt%) and richer in HFSE, LREE, and LILE compared to compositions of the lower crust given by Taylor and McLennan 1985. The Continental Crust: Its Composition and Evolution. Blackwell, Oxford, 312pp.] and Rudnick and Gao 2005. Composition of the continental crust. In: Rudnick, R.L. (Ed.), The Crust. Treatise on Geochemistry, vol. 3. Elsevier, Amsterdam, pp. 1–64]. Calculations of the seismic compressional-wave velocity from our compositional mean, using the PERPLE_X computer software, yielded values around 6.85 km/s, which are in accordance with reported seismic studies for the corresponding depth levels (6.7–7.1 km/s). |
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