New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)

La Pacana (central Andes, Northern Chile) is one of the largest resurgent calderas in the world, formed 4 Ma ago during an eruption with a VEI of 8.7. We undertake a gravimetric study to contribute new insights into the inner structure and evolution of this caldera. The La Pacana Bouguer residual an...

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Autores principales:	Delgado,Francisco, Pavez,Andrés
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2015
Materias:	La Pacana caldera Volcanology Gravimetry Caldera collapse
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000300002
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spelling	oai:scielo:S0718-710620150003000022015-10-20New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)Delgado,FranciscoPavez,Andrés La Pacana caldera Volcanology Gravimetry Caldera collapse La Pacana (central Andes, Northern Chile) is one of the largest resurgent calderas in the world, formed 4 Ma ago during an eruption with a VEI of 8.7. We undertake a gravimetric study to contribute new insights into the inner structure and evolution of this caldera. The La Pacana Bouguer residual anomaly is asymmetric and has an average amplitude of -12 to -14 mGal, which we interpret as being produced by the low-density intracaldera ignimbrite infill. A reinterpretation of the caldera stratigraphy plus the available geochronology suggests that the current shape of La Pacana was produced by the collapse of two nested calderas, roughly limited by the axis where the resurgent dome changes its orientation, with the oldest eruption in the southern part of La Pacana. The gravity data suggests that these southern and northern nested structures would have collapsed with downsag and trap-door geometries respectively, evidence of asymmetric subsidence. Intra caldera ignimbrite thicknesses were calculated with 2.5D forward models and show that the ignimbrite infill in its southern and northern parts reach ~0.6-1.1 km and ~2.5-3 km respectively. Using Gauss’s theorem, we calculate the volume of the intra caldera ignimbrite infill is ~3,400-3,500 km³, in agreement with previous estimates and with models that show that the larger the caldera diameter, the larger the erupted volume.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.42 n.3 20152015-09-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000300002en10.5027/andgeoV42n3-a02
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	La Pacana caldera Volcanology Gravimetry Caldera collapse
spellingShingle	La Pacana caldera Volcanology Gravimetry Caldera collapse Delgado,Francisco Pavez,Andrés New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)
description	La Pacana (central Andes, Northern Chile) is one of the largest resurgent calderas in the world, formed 4 Ma ago during an eruption with a VEI of 8.7. We undertake a gravimetric study to contribute new insights into the inner structure and evolution of this caldera. The La Pacana Bouguer residual anomaly is asymmetric and has an average amplitude of -12 to -14 mGal, which we interpret as being produced by the low-density intracaldera ignimbrite infill. A reinterpretation of the caldera stratigraphy plus the available geochronology suggests that the current shape of La Pacana was produced by the collapse of two nested calderas, roughly limited by the axis where the resurgent dome changes its orientation, with the oldest eruption in the southern part of La Pacana. The gravity data suggests that these southern and northern nested structures would have collapsed with downsag and trap-door geometries respectively, evidence of asymmetric subsidence. Intra caldera ignimbrite thicknesses were calculated with 2.5D forward models and show that the ignimbrite infill in its southern and northern parts reach ~0.6-1.1 km and ~2.5-3 km respectively. Using Gauss’s theorem, we calculate the volume of the intra caldera ignimbrite infill is ~3,400-3,500 km³, in agreement with previous estimates and with models that show that the larger the caldera diameter, the larger the erupted volume.
author	Delgado,Francisco Pavez,Andrés
author_facet	Delgado,Francisco Pavez,Andrés
author_sort	Delgado,Francisco
title	New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)
title_short	New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)
title_full	New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)
title_fullStr	New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)
title_full_unstemmed	New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)
title_sort	new insights into la pacana caldera inner structure based on a gravimetric study (central andes, chile)
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2015
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000300002
work_keys_str_mv	AT delgadofrancisco newinsightsintolapacanacalderainnerstructurebasedonagravimetricstudycentralandeschile AT pavezandres newinsightsintolapacanacalderainnerstructurebasedonagravimetricstudycentralandeschile
_version_	1714205850094010368

New insights into La Pacana caldera inner structure based on a gravimetric study (central Andes, Chile)

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