Volcanotectonic evolution of central Jordan: Evidence from the Shihan Volcano

The E-W Siwaqa transcurrent fault is the result of tectonic activity related to the opening of the Red Sea and sinistral movement along the Dead Sea Transform (DST). During the translation and anticlockwise rotation of the Arabian Plate, dextral motion occurred along the Siwaqa Fault that resulted in opening of the crust and allowed lava to erupt intermittently from the Shihan Volcano, producing the Shihan Basalt Group. The stress field that formed the Siwaqa Fault and its related volcanic group is characterized by N-S to NNW-SSE compression and E-W to ENE-WSW extension, which is compatible with that known in Middle Miocene - Recent and related to the DST tectonic activity. The temporal and spatial distribution of the different volcanic formations was possibly affected by stress fluctuations. The first volcanic stage occurred prior to the formation of Wadi Mujib during the Messinian age. The latest erupted during the middle Pleistocene after the formation of Wadi Mujib. The Shihan Basalt Group consists of alkali olivine basalt, basanite and hawaiite. The basalt is subdivided into a silica saturated unit and an undersaturated silica unit. Crustal contamination is evident; variations in the basalt composition are due to different degrees of partial melting and fractional crystallization.