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Coalescence of lateral spreading magma ascending through dykes: a mechanism to form a granite canopy (El Hongo pluton, Sierras Pampeanas, Argentina)

Eramo, Fabiana d' and Pinotti, Lucio Pedro and Tubía, José María and Vegas, Néstor and Aranguren, Aitor and Tejero López, Rosa María and Gómez, Daniel O. (2006) Coalescence of lateral spreading magma ascending through dykes: a mechanism to form a granite canopy (El Hongo pluton, Sierras Pampeanas, Argentina). Journal of the Geological Society, 163 (5). pp. 881-892. ISSN 0016-7649

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Abstract

This study deals with the structure of the El Hongo trondhjemite, a ENE–WSW elongate pluton
belonging to the Famatinian magmatic arc that developed from Late Cambrian to Silurian times in the Sierras
Pampeanas (Argentina). Anisotropy of magnetic susceptibility (AMS) measurements combined with structural
and microstructural data permit the correlation of magmatic and magnetic fabrics within this ferromagnetic
pluton. Magnetic foliations strike north–south and dip steeply west but in the marginal facies the foliation
becomes parallel to the ENE–WSW pluton contacts. Magnetic lineations mostly trend north–south and
plunge SE. Gravity data reveal that the pluton is in the form of a very thin horizontal sheet resting on two
north–south-trending root zones detected below the central portion of the pluton. These root zones represent
feeder dykes that exploited tension fractures. The emplacement of the El Hongo pluton took place during the
action of a buried sinistral shear zone, parallel to the elongation of the pluton, corresponding to a transfer
fault associated with the late extensional exhumation of the Famatinian domain. The emplacement of other
Famatinian granites of the Sierras Pampeanas could be related to similar late shear zones.


Item Type:Article
Uncontrolled Keywords:Trondhjemite study; Magma; Sierras Pampeanas; Argentina
Subjects:Sciences > Geology > Petrology
Sciences > Geology > Geodynamics
ID Code:17140
Deposited On:19 Nov 2012 12:03
Last Modified:19 Nov 2012 12:03

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