Interaction between magmatic and tectonic stresses during dyke intrusion

Cataclastic and mylonitic rocks exposed in the southwestern part of the Peninsula de Mejillones, northern Chile, are intruded at high angles of the foliation by younger, steeply inclined (±70°) basaltic dykes that resemble intrusive tension gashes with knife-edge contacts with the country rocks. The...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autor principal:	Skarmeta,Jorge
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2011
Materias:	Basaltic dykes Shape preferred orientation Magmatic and tectonic stress Magmatic faulting Magma viscosity Hydrostatic regime
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062011000200008
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:scielo:S0718-71062011000200008
record_format	dspace
spelling	oai:scielo:S0718-710620110002000082011-09-28Interaction between magmatic and tectonic stresses during dyke intrusionSkarmeta,Jorge Basaltic dykes Shape preferred orientation Magmatic and tectonic stress Magmatic faulting Magma viscosity Hydrostatic regime Cataclastic and mylonitic rocks exposed in the southwestern part of the Peninsula de Mejillones, northern Chile, are intruded at high angles of the foliation by younger, steeply inclined (±70°) basaltic dykes that resemble intrusive tension gashes with knife-edge contacts with the country rocks. These late dykes developed sigmoidaly-shaped, preferred orientation paths defined by oriented pyroxene phenocrysts that vary in size, aspect ratio, concentration and distribution across the width of an individual dyke. This banding has z and s asymmetries that indicate the sense of displacement of the country rock. The relative involvement of the coeval, internal and external stresses that caused the finite strains is estimated by using a partition analysis. The phenocryst location and size distribution are related to the internal magma flow velocity (u m) stress component, whereas the sigmoid banding is linked to the external tectonic wall displacement velocity (±u). Dyke wall sliding with or against the magma flow induced the asymmetric shear strain distribution. The measured strain and displacements are analyzed using the deformation model of viscous laminar flow confined between two parallel plates moving parallel to each other with opposed motion. The shear stresses related to magma intrusion and frictional dyke-wall shear are quantified on the basis of magma flow displacements, cooling times and the temperature dependent viscosity of basalts in the linear rheology range. At the estimated depth where the intrusion and deformation occurred, the state of stress was close to being hydrostatic. This conclusion is in agreement with established models of active-collapsing volcanic centres, where bulk permeability is accommodated by means of a mesh of interconnected dykes and active faults. This interactivity tends to re-equilibrate, locally and transiently, any excess differential stress and redistributes excess magmatic pressures to create a uniform hydrostatic stress regime.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.38 n.2 20112011-07-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062011000200008en
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Basaltic dykes Shape preferred orientation Magmatic and tectonic stress Magmatic faulting Magma viscosity Hydrostatic regime
spellingShingle	Basaltic dykes Shape preferred orientation Magmatic and tectonic stress Magmatic faulting Magma viscosity Hydrostatic regime Skarmeta,Jorge Interaction between magmatic and tectonic stresses during dyke intrusion
description	Cataclastic and mylonitic rocks exposed in the southwestern part of the Peninsula de Mejillones, northern Chile, are intruded at high angles of the foliation by younger, steeply inclined (±70°) basaltic dykes that resemble intrusive tension gashes with knife-edge contacts with the country rocks. These late dykes developed sigmoidaly-shaped, preferred orientation paths defined by oriented pyroxene phenocrysts that vary in size, aspect ratio, concentration and distribution across the width of an individual dyke. This banding has z and s asymmetries that indicate the sense of displacement of the country rock. The relative involvement of the coeval, internal and external stresses that caused the finite strains is estimated by using a partition analysis. The phenocryst location and size distribution are related to the internal magma flow velocity (u m) stress component, whereas the sigmoid banding is linked to the external tectonic wall displacement velocity (±u). Dyke wall sliding with or against the magma flow induced the asymmetric shear strain distribution. The measured strain and displacements are analyzed using the deformation model of viscous laminar flow confined between two parallel plates moving parallel to each other with opposed motion. The shear stresses related to magma intrusion and frictional dyke-wall shear are quantified on the basis of magma flow displacements, cooling times and the temperature dependent viscosity of basalts in the linear rheology range. At the estimated depth where the intrusion and deformation occurred, the state of stress was close to being hydrostatic. This conclusion is in agreement with established models of active-collapsing volcanic centres, where bulk permeability is accommodated by means of a mesh of interconnected dykes and active faults. This interactivity tends to re-equilibrate, locally and transiently, any excess differential stress and redistributes excess magmatic pressures to create a uniform hydrostatic stress regime.
author	Skarmeta,Jorge
author_facet	Skarmeta,Jorge
author_sort	Skarmeta,Jorge
title	Interaction between magmatic and tectonic stresses during dyke intrusion
title_short	Interaction between magmatic and tectonic stresses during dyke intrusion
title_full	Interaction between magmatic and tectonic stresses during dyke intrusion
title_fullStr	Interaction between magmatic and tectonic stresses during dyke intrusion
title_full_unstemmed	Interaction between magmatic and tectonic stresses during dyke intrusion
title_sort	interaction between magmatic and tectonic stresses during dyke intrusion
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2011
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062011000200008
work_keys_str_mv	AT skarmetajorge interactionbetweenmagmaticandtectonicstressesduringdykeintrusion
_version_	1714205833112322048

Interaction between magmatic and tectonic stresses during dyke intrusion

Ejemplares similares