Unexplained volcanism: Saudi Arabia

The Arabian Peninsula has been diverging from Africa for the past 30 million years, following the arrival of the Afar hot spot. Decompression melting has been providing the lavas that create new oceanic crust in the opening Red Sea, but a suite of volcanoes in western Saudi Arabia that have been erupting for the past 12 million years is probably too far to the east of the divergent margin to be directly related. What then is causing this volcanism? (check out western Saudi Arabia in Google maps to see the impressive black lava surrounded by the vast desert landscape). The Afar hot spot would be a good candidate, but it is also thought to be a bit too far to the south, near the diverging triple junction. Perhaps lateral flow of the hot spot plume is driving the melting, or maybe a separate plume directly beneath Saudi is involved. Bob Duncan and Abdullah Al-Amri (2013) set out to address this question by studying Harrat Lunayyir volcanic field, which last erupted about 1000 years ago and occasionally experiences seismic activity suggesting that it is still active. Their 40Ar/39Ar age determinations show that the field is very young (less than 600 thousand years) with lavas characterized by intraplate geochemistry (perhaps ruling out the divergent margin or other extension related melting). The lack of age progression, along with isotopic considerations, also seems to rule out lateral flow from the Afar plume. More study is necessary to understand the cause of volcanism this region.

Source: Robert A. Duncan, Abdullah M. Al-Amri, Timing and composition of volcanic activity at Harrat Lunayyir, western Saudi Arabia, Journal of Volcanology and Geothermal Research, Volume 260, 15 June 2013, Pages 103-116, ISSN 0377-0273, (http://www.sciencedirect.com/science/article/pii/S0377027313001479).