--> Determination of Stress and Strain Evolution From Faults and Calcite Twins on the Western Margin of the Indochina Block

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Determination of Stress and Strain Evolution From Faults and Calcite Twins on the Western Margin of the Indochina Block

Abstract

Francesco Arboit a*, Khalid Amrouch b, Alan S. Collins a, Rosalind King a and Christopher Morley c a Centre for Tectonics Resources and Exploration (TRaX), Department of Earth Sciences, The University of Adelaide, SA 5005, Australia. b Australian School of Petroleum (ASP), Department of Earth Sciences, The University of Adelaide, SA 5005, Australia. C Chiang Mai University, 239 Huaykaew Road, Tumbol Suthep Amphur Muang, Chiang Mai, Thailand. Abstract In polyphase tectonic zones integrating fault and fracture analysis with a study of calcite twins can determine the evolving paleo-stress magnitudes and principle directions that affected the area. Here we want to presents the results of the analyses of fractures, striated faults and calcite twins collected within the Khao Khwang Fold and Thrust Belt (KKF&TB) in central Thailand (SE Asia), attempting therefore to reconstruct the tectonic evolution of highly deformed, polyphase ranges. Tectonic data were collected in the Permian carbonates of the Khao Khad Formation of the Saraburi Group, and five successive tectonic stages are determined that are interpreted to have developed before, during and after the Triassic Indosinian Orogeny. The first three stages pre-date the main deformation event: the first stage is interpreted as a pre-Indosinian N-S extensional stage, the second stage was a N-S compression mostly perpendicular to the fold axes of the main structures, while the third stage shows a rotation of about 90° associated with a E-W compressional strike slip phase. The last two stress tensors were recorded both by the calcite twins and faults & fractures emplaced in the Khao Khad Formation. These two stages took place after the main folding event and correspond to N-S compressional and to a E-W strike-slip, which most likely is attributable to the last Cainozoic deformation.