Geophysical evidence for an extensive Pie de Palo Complex mafic–ultramafic belt,San Juan,Argentina |
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| Institution: | 1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina;2. Servicio Geológico–Minero Argentino (SEGEMAR), Julio A. Roca 651, 1067 Buenos Aires, Argentina;3. Dpto. Ciencias Geológicas, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires, Argentina;4. Geological Survey of Canada, 601 Both St., Ottawa, Canada;1. Beijing SHRIMP Centre, Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, 100037 Beijing, China;2. Department of Geosciences, University of Mainz, P.O. Box 3980, 55099 Mainz, Germany;3. Council for Geoscience, Limpopo Unit, Polokwane, South Africa;1. Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China;2. PetroChina Tarim Oilfield Company, Korla 841000, China;3. State Key Lab for Geological Processes and Mineral Resources, Center for Global Tectonics, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an 710069, China;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. Department of Geochemistry, College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China;1. Northern Arizona University, Flagstaff, AZ, United States;2. University of Idaho, Moscow, ID, United States;3. University of Wisconsin–Madison, Madison, WI, United States |
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| Abstract: | The recent completion of a high-resolution aeromagnetic survey over the Pie de Palo uplift of the western Sierras Pampeanas has revealed an area of large magnetic anomalies associated with the Pie de Palo Complex. The Las Pirquitas thrust, which has transported and uplifted the Pie de Palo Complex, is recognized for at least 30 km in a roughly NE direction along the western boundary of the Pie de Palo Complex, beyond its limited outcrop. The type of sediments of the Caucete Group in the footwall of the Las Pirquitas thrust, which are regarded as the leading edge of the Precordillera terrane, are associated with much less pronounced magnetic anomalies.In addition, a conspicuous, NNE trending, broad magnetic high stands out in the survey, several kilometers to the east of the main outcrops of the Pie de Palo Complex; this broad magnetic anomaly bisects the Pie de Palo basement block, and continues further south at least as far as 32°S, the southern boundary of the latest aeromagnetic survey. This magnetic anomaly is interpreted to represent a structure corresponding to the Grenvillian Precordillera–Pie de Palo tectonic boundary zone, and would comprise the buried largest part of the mafic–ultramafic belt.The geophysical model of the magnetic data indicates that the boundary zone dips to the east, possibly suggesting the existence of a set of synthetic east dipping, west-verging thrusts, of which only one major structure (Las Pirquitas thrust) is exposed; the possibility of other slivers of upthrust boundary zone material cannot be excluded. It is considered that the Pie de Palo Complex represents a small sliver upthrust from the unexposed boundary zone material (containing highly magnetic mafic–ultramafic rocks).The east-dipping, west verging structures associated with the Pie de Palo Complex are suggested to represent an Ordovician reactivation of a Grenvillian suture zone developed when the Precordillera basement and Pie de Palo terrane docked; this reactivation probably resulted from the collision of the Cuyania terrane onto the western margin of Gondwana. |
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