Characterization and Origin of the Miocene Mudawwara-Quwayra Basaltic Dike, Southern Jordan

Abstract

Petrographic, mineralogical and geochemical investigations were carried out on representative samples from the Mudawwara-Quwayra Dike (MQD) in southernJordan. The MQD intruded Paleozoic and Cretaceous rocks as sub-vertical basaltic plugs, striking NW-SE along a fault zone and extending for more than 100 km. The MQD forms irregularly positive features, and is represented by symmetrical, elliptical, elongated or circular hills. It comprises thin basaltic layers intercalated with pyroclastics and inclusions of different size and lithology, including limestone, sandstone, phosphate, quartzite, and marble. Petrographically, the rock exhibits phyric, porphyritic, vitrophyric and locally glomerophyritic textures manifested by plagioclase, clinopyroxene and rare olivine and set in a matrix of plagioclase, pyroxene, brown glass and opaque phases. Clinopyroxene and olivine phenocyrsts show disequilibrium textures such as reaction/resorbed rims in the forms of corroded ends. The paragenetic sequence shows that olivine is the first phase to be crystallized and coexisting with pyroxene at sometime, while pyroxene continues crystallization. Plagioclase might have crystallized in contemporaneous later than the pyroxene. The MQD rocks are classified as basalt and exhibit a narrow range of silica with a unique subalkaline affinity. This is most probably attributed to assimilation of the abundant siliciclastic inclusions by the ascending magma. Emplacement of the MQD is attributed to regional phase of magmatism in Jordan and Saudi Arabia, which is probably the peripheral extension of a large magmatic event widely exposed in the Red Sea realm.