Structural control of young basaltic fissure eruptions in the plateau basalt area of the Arabian Plate,northeastern Jordan |
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| Institution: | 1. Department of Geosciences, Idaho State University, 921 South 8th Avenue, Stop 8072, Pocatello, ID 83209, United States;2. NASA Ames Research Center, Mountain View, CA 94035, United States;3. Bay Area Environmental Research Institute, Petaluma, CA 94952, United States;4. NASA Goddard Space Flight Center, Geology, Geophysics and Geochemistry Lab, Greenbelt, MD 20771, United States;5. Department of Geological Sciences, Brigham Young University, Provo, UT 84602, United States;6. Mars Space Flight Facility, Arizona State University, Tempe, AZ 85287, United States;1. University of Jordan, Amman 11942, Jordan;2. Bundesanstalt fuer Geowissenshaften und Rohstoffe (BGR) Hannover, Germany;3. Water, Energy and Environment Center, University of Jordan, Amman 11942, Jordan;1. Siberian Branch of RAS, Novosibirsk State University and Lavrentyev Institute of Hydrodynamics, 15 Av. Lavrentyev, Novosibirsk 630090, Russia;2. LAMA, UMR 5127 CNRS, Université Savoie Mont Blanc, Campus Scientifique, Le Bourget-du-Lac Cedex F-73376, France;3. Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, LAMA, 73000 Chambéry, France |
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| Abstract: | In the El Hamadieh region, part of the large intracontinental basalt plateau extending NW-SE from Syria to Jordan and Saudi-Arabia in the northern part of the Arabian Plate, young volcanic edifices formed by fissure eruptions have been investigated; all geometrical dimensions and parameters of the ridges have been measured, the field relationships documented, the data evaluated and the structural patterns analysed. Using the attitude of the fissures as palaeostress indicators, a stress-strain-model is introduced, showing the superimposition of stress fields. Magma was extruded at the intersection of two regional structures: the NE-SW-striking Amman-Hallabat fold belt and the NW-SE-trending Azraq-Sirhan graben. A first effusion with a relatively fluid magma took place in reactivated fold-related conjugated hk0-shear fractures with a compressional σ1-stress trending NW-SE. A second phase of fissure effusions produced a more viscous lava. These fissures represent (a) hk0-planes with an acute angle about the fold axis, and (b) planes of normal faults along the southwestern shoulder of the Azraq-Sirhan graben in the position of fold-related reactivated conjugated 0hl-shear planes.The geometrical relationships between the Amman-Hallabat folds, the Azraq-Sirham faults and the volcanic fissures indicate a rotation of the local stress field with the originally NW-SE-trending compressional σ1- and the NE-SW-trending, σ3-stress changing into a NE-SW-acting tensional σ1-stress. |
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