HR: 1340h
AN: V33C-1524    [Abstracts]
TI: Magnetic fabric of the Torres del Paine, Patagonia
AU: Michel, J
EM: juergen.michel@unil.ch
AF: Institute of Mineralogy and Geochemistry, Universtity of Lausanne, Lausanne, 1015,
AU: * Baumgartner, L
AF: Institute of Mineralogy and Geochemistry, Universtity of Lausanne, Lausanne, 1015,
AU: de Saint-Blanquat, M
AF: Laboratoire des Mécanismes et Transferts en Géologie, Université Paul-Sabatier 3, Toulouse, 31400,
AU: Putlitz, B
AF: Institute of Mineralogy and Geochemistry, Universtity of Lausanne, Lausanne, 1015,
AU: Sanchez, A
AF: Departamento de Geología, Universidad de Chile, Santiago, Correo 21,
AU: Darbellay, B
AF: Institute of Mineralogy and Geochemistry, Universtity of Lausanne, Lausanne, 1015,
AU: Cavargna, M
AF: Institute of Mineralogy and Geochemistry, Universtity of Lausanne, Lausanne, 1015,
AB: The Miocene bimodal Torres del Paine Intrusive Complex (TIPC) consists of the lower Paine-Mafic-Complex (PMC) and the overlaying Paine Granite. Igneous structures (layering, xenolith orientations, and major contacts) are vertical in the westernmost part of the PMC, while they are sub-horizontal in the central and eastern parts. The TPIC is very homogeneous except in the PMC where complex interactions between mafic and felsic magmas were observed. No foliation or lineations are present in the field. Based on field-observations we distinguish at least three different sheet-like units in the Paine Granite, each one several tens to hundreds of meters thick. Younger sheets generally under-plate their precursor. We measured the anisotropy of magnetic susceptibility (AMS) on 145 samples from sites distributed horizontally over the entire surface of the TPIC and along 4 vertical profiles. The high intensity of the magnetic susceptibility for most of the Paine Granite and the PMC samples is due to the presence of magnetite. The magnetic lineations show a general WNW-ESE trend, parallel to the long axis of the intrusion. Lineations in the western part are strongly west-dipping to subvertical, parallel to the magmatic layering in the PMC. This supports the interpretation of a feeder-zone in that area. The lineations are sub-horizontal in the rest of the intrusion. Only minor variations in lineation orientation are observed in several hundred meter long vertical profiles in the central part of the Paine Granite. The magnetic foliations show the structural control exerted by the contact of the intrusion during its assembly: they are mostly horizontal in the central part, and are progressively steeper towards the contact. The low anisotropy is in agreement with the absence of texture observed in the field and thin sections. No sub-solidus deformation took place during the TPIC construction. The internal structures and magnetic fabrics support the interpretation of an intrusion assembled by horizontal transfer of magma in the form of sheet-like pulses stacking them vertically. Our results also show that the regional syn-magmatic deformation played no role in the emplacement of the TPIC.
DE: 1518 Magnetic fabrics and anisotropy
DE: 1519 Magnetic mineralogy and petrology
DE: 3618 Magma chamber processes (1036)
DE: 8035 Pluton emplacement
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting