Magmatic Gradients in the Cretaceous Caleu Pluton (Central Chile): Injections of Pulses from a Stratified Magma Reservoir |
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| Institution: | 1. Department of Geology, University of Chile, Casilla 13518, Correo 21, Santiago, Chile;2. Institut de Recherche pour le Development (IRD), Casilla 53390, Correo Central, Santiago, Chile;1. Food Technology Department, Universitat Politècnica de València, Camino de Vera s/n, Valencia, Spain;2. Chemical and Biochemical Engineering Department, Instituto Tecnológico de Veracruz, Av. Miguel A. de Quevedo, 2779, Veracruz, Mexico;1. Earth Dynamics Group, ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), Curtin University, GPO Box U1987, Perth, WA 6845, Australia;2. The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;3. School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia;4. School of Earth Sciences, University of Western Australia, Perth WA 6009, Australia;5. State Key Lab of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;4. Grupo de Investigación en Estratigrafía y Vulcanología (GIEV) Cumanday, Universidad de Caldas, Colombia;1. Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000, Clermont-Ferrand, France;2. Instituto Geofísico, Escuela Politécnica Nacional, Ladrón de Guevara, E11-253, Ap., 2759, Quito, Ecuador;3. Université Côte d''Azur, Observatoire de la Côte d''Azur, CNRS, IRD, Géoazur, 250 Rue Albert Einstein, Sophia Antipolis, 06560, Valbonne, France;4. Université Paris-Saclay, CNRS, Laboratoire GEOPS, Rue du Belvédère, 91405, Orsay, France;5. Laboratoire Géosciences Océan, Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, Rue Dumont d''Urville, 29280, Plouzané, France;1. Bullard Laboratories, Department of Earth Sciences, University of Cambridge, UK;2. Research School of Earth Sciences, The Australian National University, Acton, ACT, Australia;3. Lamont–Doherty Earth Observatory, Columbia University, New York, USA;4. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA;5. Lawrence Berkeley National Laboratory, Berkeley, CA, USA;6. Department of Earth Science and Engineering, Imperial College London, UK;7. School of GeoSciences, University of Edinburgh, UK |
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| Abstract: | The Caleu pluton (Central Chile) extending over 338 km2 and with more than 1, 400 m of vertical relief intrudes the N-S trending Lower Cretaceous volcano-sedimentary and volcanic successions at a depth equivalent to a pressure of 2 kb. The host, stratified volcanic successions, are tilted about 30°–40° E, whereas the pluton shows paleomagnetic evidence of either tilting of <15° E or clockwise rotation by few degrees.A gradient of westward increasing SiO2 content is recognized across the pluton, giving rise to three N-S elongated zones: Gabbro/Diorite Zone (GDZ), Tonalite Zone (TZ) and Granodiorite Zone (GZ). Biotite and hornblende compositions also exhibit a westward decreasing gradient in Mg/(Mg+Fe), indicating that the more mafic the zone is, the more oxidizing is its crystallization condition. Horizontal inward gradients of progressively less evolved rocks are recognized across GDZ and TZ, whereas no horizontal gradients were found in the GZ. Vertical compositional gradients are recognized in the GDZ and TZ, which consist of an upward increase in SiO2 and decrease in MgO, FeO, Fe2O3, and compatible trace elements. A vertical compositional boundary was recognized along a traverse across the TZ separating two magma pulses with similar trends of compositional variations.The three zones of the Caleu pluton were derived from a common isotopically (Sr-Nd) depleted source. Each zone probably evolved independently, as their compositional characteristics would have not been acquired in situ. The resulting compositional characteristics of the zones would have been developed prior to the intrusion, in a subjacent stratified reservoir placed at about seven kilometers below the pluton. |
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