Distinctive diamagnetic fabrics in dolostones evolved at fault cores,the Dead Sea Transform |
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| Institution: | 1. Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel;2. Geological Survey of Israel, 30 Malkhe Israel Street, Jerusalem 95501, Israel;1. Department of Earth Science, University of Toronto, 22 Russell Street, Toronto, ON M5S 3B1, Canada;2. AEL-AMS Laboratory, Advanced Research Complex, University of Ottawa, 25 Templeton St., Ottawa, ON K1N 6N5, Canada;1. Young Researchers and Elites Club, Science and Research Branch, Islamic Azad University, Tehran, Iran;2. Department of Industrial Management, Faculty of Management and Accounting, Karaj Branch, Islamic Azad University, Alborz P.O. Box: 31485-313, Iran;3. Young Researchers and Elites Club, Karaj Branch, Islamic Azad University, Alborz, Iran;1. Analytical & Testing Center of Beijing Normal University, Beijing 100875, China;2. Institute of Beijing Criminal Science and Technology, Beijing 100054, China;1. Northeast Petroleum University, Daqing 163318, China;2. Exploration and Development Institute of PetroChina Liaohe Oil Field Company, Panjin 124010, China;3. Resolution Energy Services LLC, Houston TX, 77204-2024, USA;4. Daqing Oil Field Company Ltd., PetroChina, Daqing 163517, China |
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| Abstract: | We resolve the anisotropy of magnetic susceptibility (AMS) axes along fault planes, cores and damage zones in rocks that crop out next to the Dead Sea Transform (DST) plate boundary. We measured 261 samples of mainly diamagnetic dolostones that were collected from 15 stations. To test the possible effect of the iron content on the AMS we analyzed the Fe concentrations of the samples in different rock phases. Dolostones with mean magnetic susceptibility value lower than −4 × 10−6 SI and iron content less than ∼1000 ppm are suitable for diamagnetic AMS-based strain analysis. The dolostones along fault planes display AMS fabrics that significantly deviate from the primary “sedimentary fabric”. The characteristics of these fabrics include well-grouped, sub-horizontal, minimum principal AMS axes (k3) and sub-vertical magnetic foliations commonly defined by maximum and intermediate principal AMS axes (k1 and k2 axes, respectively). These fabrics are distinctive along fault planes located tens of kilometers apart, with strikes ranging between NNW-SSE and NNE-SSW and different senses of motion. The obtained magnetic foliations (k1–k2) are sub-parallel (within ∼20°) to the fault planes. Based on rock magnetic and geochemical analyses, we interpret the AMS fabrics as the product of both shape and crystallographic anisotropy of the dolostones. Preferred shape alignment evolves due to mechanical rotation of subordinate particles and rock fragments at the fault core. Preferred crystallographic orientation results from elevated frictional heating (>300 °C) during faulting, which enhances c-axes alignment in the cement-supported dolomite breccia due to crystal-plastic processes. The penetrative deformation within fault zones resulted from the local, fault-related strain field and does not reflect the regional strain field. The analyzed AMS fabrics together with fault-plane kinematics provide valuable information on faulting characteristics in the uppermost crust. |
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| Keywords: | Anisotropy of magnetic susceptibility Faulting Fault core Preferred orientation Dead Sea Transform |
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