HR: 1340h
AN: T33B-0554    [Abstracts]
TI: Formation of Ore Deposits Triggered by Aseismic Ridge Subduction
AU: * Rosenbaum, G
EM: rosenbaum@uni-mainz.de
AF: Institut f�r Gowissenschaften, Johannes Gutenberg Universit�t, Becherweg 21, Mainz, 55099 Germany
AU: * Rosenbaum, G
EM: rosenbaum@uni-mainz.de
AF: Department of Earth Sciences, University of Queensland, Brisbane, Qld 4072 Australia
AU: Giles, D
EM: David.Giles@sci.monash.edu.au
AF: School of Geosciences, Monash University, Melbourne, Vic 3800 Australia
AU: Betts, P
EM: Peter.Betts@sci.monash.edu.au
AF: School of Geosciences, Monash University, Melbourne, Vic 3800 Australia
AU: Saxon, M
EM: marksaxon@optusnet.com.au
AF: Sierra Minerals Ltd, PO Box 2213, Bendigo DC, Vic 3554 Australia
AU: Weinberg, R
EM: weinberg@mail.earth.monash.edu.au
AF: School of Geosciences, Monash University, Melbourne, Vic 3800 Australia
AU: Duboz, C
EM: cecile@mail.earth.monash.edu.au
AF: School of Geosciences, Monash University, Melbourne, Vic 3800 Australia
AB: Magmatic-hydrothermal ore deposits in suprasubduction environments are abundant in the Andes, where they are associated with the eastward subduction of the Nazca plate beneath the continental South American plate during the last 200 Ma. These deposits do not seem to correspond with progressive subduction processes but are concentrated at distinct regions that experienced pulses of intense metallogenic activity. An example is the Miocene metallogenic belt in the central Andes that was formed during a relatively short period between 15-5 Ma, and is characterised by clusters of mineral deposits in northern Peru and in central Chile. We propose that a key factor for the occurrence of metallogenic episodes during progressive subduction is related to bathymetric heterogeneities within the subducting oceanic plate. Such heterogeneities are manifested by the subduction of topographic anomalies that affected the whole dynamics of the subduction system and triggered metallogenic processes. Our study shows that the spatial and temporal distribution of Miocene ore deposits in the Peruvian Andes correspond with the arrival of relatively buoyant topographic anomalies, namely the Nazca Ridge in central Peru and the now-consumed Inca Plateau in northern Peru, at the subduction zone. Plate reconstruction shows a rapid metallogenic response to the arrival of the topographic anomalies at the subduction trench. This is indicated by clusters of ore deposits situated within the proximity of the laterally migrating zones of ridge subduction. It is accordingly suggested that tectonic changes associated with aseismic ridge subduction, (i.e. a change in the state of stress, flattening of the subducting slab, temporal quiescence in the volcanic activity and partial melting of the subducting slab) may trigger the formation of ore deposits in metallogenically fertile suprasubduction environments.
DE: 3665 Mineral occurrences and deposits
DE: 8104 Continental margins: convergent
DE: 8155 Plate motions: general (3040)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 9360 South America
SC: Tectonophysics [T]
MN: Fall Meeting 2005