Mantle processes and sources of neogene slab window magmas from Southern Patagonia, Argentina

Matthew Gorring, Suzanne M. Kay

Research output: Contribution to journalArticleResearchpeer-review

145 Citations (Scopus)

Abstract

Neogene plateau lavas in Patagonia, southern Argentina, east of the volcanic gap between the Southern and Austral Volcanic Zones at 46·5° and 49·5°S are linked with asthenospheric slab window processes associated with the collision of a Chile Ridge segment with the Chile Trench at 12 Ma. The strong ocean-island basalt (OIB)-like geochemical signatures (La/Ta <20;; Ba/La <20; 87Sr/86Sr = 0·7035-0·7046; 143Nd/144Nd = 0·51290-0·51261; 206Pb/204Pb = 18·3-18·8; 207Pb204Pb = 15·57-15·65; 208Pb/204Pb = 38·4-38·7) of these Patagonian slab window lavas contrast with the mid-ocean ridge basalt (MORB)-like, depleted mantle signatures of slab window lavas elsewhere in the cordillera, (e.g. Antarctic Peninsula; Baja California). The Patagonian lavas can be divided into a voluminous ∼ 12-5 Ma, tholeeitic main-plateau sequence (48-55% SiO2; 4-5% Na2O 〈 K2O) and a less voluminous ∼ 7-2 Ma alkaline post-plateau sequence (43-49% SiO2; 5-8% Na2O 〈 K2O). Moderately high FeOT(9-11%), and low heavy rare earth element (HREE), γ, and Sc concentrations in all lavas are consistent with melt generation just below the garnet-spinel transition at a depth of ∼ 70 km. The main-plateau lavas from the western back-arc can be modeled by ∼ 10-15% partial melting of an OIB-like asthenospheric mantle source with additions form slab fluid-melt components coupled with crustal contamination (AFC). A three-stage petrogenetic model is envisaged: (1) decompression melting and source region contamination of an OIB-like subslab asthenospheric source by slab melts of the trailing edge of the subducted Nazca Plate; (2) minor contamination of slab window melts with arc components 'stored' in the supraslab mantle wedge and/or basal continental lithosphere; (3) further modification by addition of crustal components during magma ascent. The main-plateau lavas from the eastern back-arc can be modeled by ∼ 7% partial melting of the same asthenospheric source as the influence of arc components diminishes and the intensity of mantle upwelling into the slab window decreases. All post-plateau lavas can be modeled as 1-4% partial melts of the pristine OIB-like asthenospheric source in the widening slab window.

Original languageEnglish
Pages (from-to)1067-1094
Number of pages28
JournalJournal of Petrology
Volume42
Issue number6
DOIs
StatePublished - 1 Jan 2001

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mantle process
Argentina
mantle source
Neogene
slab
Earth mantle
slabs
plateaus
basalt
ocean island basalt
plateau
Melting
Contamination
melt
oceans
arcs
contamination
Chile
melting
partial melting

Keywords

  • Back-arc processes
  • Mantle chemistry
  • Plateau basalt petrogenesis
  • Slab window magmatism
  • Southern patagonia

Cite this

@article{0dc65a61003f49edbd20d8b3ac08e813,
title = "Mantle processes and sources of neogene slab window magmas from Southern Patagonia, Argentina",
abstract = "Neogene plateau lavas in Patagonia, southern Argentina, east of the volcanic gap between the Southern and Austral Volcanic Zones at 46·5° and 49·5°S are linked with asthenospheric slab window processes associated with the collision of a Chile Ridge segment with the Chile Trench at 12 Ma. The strong ocean-island basalt (OIB)-like geochemical signatures (La/Ta <20;; Ba/La <20; 87Sr/86Sr = 0·7035-0·7046; 143Nd/144Nd = 0·51290-0·51261; 206Pb/204Pb = 18·3-18·8; 207Pb204Pb = 15·57-15·65; 208Pb/204Pb = 38·4-38·7) of these Patagonian slab window lavas contrast with the mid-ocean ridge basalt (MORB)-like, depleted mantle signatures of slab window lavas elsewhere in the cordillera, (e.g. Antarctic Peninsula; Baja California). The Patagonian lavas can be divided into a voluminous ∼ 12-5 Ma, tholeeitic main-plateau sequence (48-55{\%} SiO2; 4-5{\%} Na2O 〈 K2O) and a less voluminous ∼ 7-2 Ma alkaline post-plateau sequence (43-49{\%} SiO2; 5-8{\%} Na2O 〈 K2O). Moderately high FeOT(9-11{\%}), and low heavy rare earth element (HREE), γ, and Sc concentrations in all lavas are consistent with melt generation just below the garnet-spinel transition at a depth of ∼ 70 km. The main-plateau lavas from the western back-arc can be modeled by ∼ 10-15{\%} partial melting of an OIB-like asthenospheric mantle source with additions form slab fluid-melt components coupled with crustal contamination (AFC). A three-stage petrogenetic model is envisaged: (1) decompression melting and source region contamination of an OIB-like subslab asthenospheric source by slab melts of the trailing edge of the subducted Nazca Plate; (2) minor contamination of slab window melts with arc components 'stored' in the supraslab mantle wedge and/or basal continental lithosphere; (3) further modification by addition of crustal components during magma ascent. The main-plateau lavas from the eastern back-arc can be modeled by ∼ 7{\%} partial melting of the same asthenospheric source as the influence of arc components diminishes and the intensity of mantle upwelling into the slab window decreases. All post-plateau lavas can be modeled as 1-4{\%} partial melts of the pristine OIB-like asthenospheric source in the widening slab window.",
keywords = "Back-arc processes, Mantle chemistry, Plateau basalt petrogenesis, Slab window magmatism, Southern patagonia",
author = "Matthew Gorring and Kay, {Suzanne M.}",
year = "2001",
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doi = "10.1093/petrology/42.6.1067",
language = "English",
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}

Mantle processes and sources of neogene slab window magmas from Southern Patagonia, Argentina. / Gorring, Matthew; Kay, Suzanne M.

In: Journal of Petrology, Vol. 42, No. 6, 01.01.2001, p. 1067-1094.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Mantle processes and sources of neogene slab window magmas from Southern Patagonia, Argentina

AU - Gorring, Matthew

AU - Kay, Suzanne M.

PY - 2001/1/1

Y1 - 2001/1/1

N2 - Neogene plateau lavas in Patagonia, southern Argentina, east of the volcanic gap between the Southern and Austral Volcanic Zones at 46·5° and 49·5°S are linked with asthenospheric slab window processes associated with the collision of a Chile Ridge segment with the Chile Trench at 12 Ma. The strong ocean-island basalt (OIB)-like geochemical signatures (La/Ta <20;; Ba/La <20; 87Sr/86Sr = 0·7035-0·7046; 143Nd/144Nd = 0·51290-0·51261; 206Pb/204Pb = 18·3-18·8; 207Pb204Pb = 15·57-15·65; 208Pb/204Pb = 38·4-38·7) of these Patagonian slab window lavas contrast with the mid-ocean ridge basalt (MORB)-like, depleted mantle signatures of slab window lavas elsewhere in the cordillera, (e.g. Antarctic Peninsula; Baja California). The Patagonian lavas can be divided into a voluminous ∼ 12-5 Ma, tholeeitic main-plateau sequence (48-55% SiO2; 4-5% Na2O 〈 K2O) and a less voluminous ∼ 7-2 Ma alkaline post-plateau sequence (43-49% SiO2; 5-8% Na2O 〈 K2O). Moderately high FeOT(9-11%), and low heavy rare earth element (HREE), γ, and Sc concentrations in all lavas are consistent with melt generation just below the garnet-spinel transition at a depth of ∼ 70 km. The main-plateau lavas from the western back-arc can be modeled by ∼ 10-15% partial melting of an OIB-like asthenospheric mantle source with additions form slab fluid-melt components coupled with crustal contamination (AFC). A three-stage petrogenetic model is envisaged: (1) decompression melting and source region contamination of an OIB-like subslab asthenospheric source by slab melts of the trailing edge of the subducted Nazca Plate; (2) minor contamination of slab window melts with arc components 'stored' in the supraslab mantle wedge and/or basal continental lithosphere; (3) further modification by addition of crustal components during magma ascent. The main-plateau lavas from the eastern back-arc can be modeled by ∼ 7% partial melting of the same asthenospheric source as the influence of arc components diminishes and the intensity of mantle upwelling into the slab window decreases. All post-plateau lavas can be modeled as 1-4% partial melts of the pristine OIB-like asthenospheric source in the widening slab window.

AB - Neogene plateau lavas in Patagonia, southern Argentina, east of the volcanic gap between the Southern and Austral Volcanic Zones at 46·5° and 49·5°S are linked with asthenospheric slab window processes associated with the collision of a Chile Ridge segment with the Chile Trench at 12 Ma. The strong ocean-island basalt (OIB)-like geochemical signatures (La/Ta <20;; Ba/La <20; 87Sr/86Sr = 0·7035-0·7046; 143Nd/144Nd = 0·51290-0·51261; 206Pb/204Pb = 18·3-18·8; 207Pb204Pb = 15·57-15·65; 208Pb/204Pb = 38·4-38·7) of these Patagonian slab window lavas contrast with the mid-ocean ridge basalt (MORB)-like, depleted mantle signatures of slab window lavas elsewhere in the cordillera, (e.g. Antarctic Peninsula; Baja California). The Patagonian lavas can be divided into a voluminous ∼ 12-5 Ma, tholeeitic main-plateau sequence (48-55% SiO2; 4-5% Na2O 〈 K2O) and a less voluminous ∼ 7-2 Ma alkaline post-plateau sequence (43-49% SiO2; 5-8% Na2O 〈 K2O). Moderately high FeOT(9-11%), and low heavy rare earth element (HREE), γ, and Sc concentrations in all lavas are consistent with melt generation just below the garnet-spinel transition at a depth of ∼ 70 km. The main-plateau lavas from the western back-arc can be modeled by ∼ 10-15% partial melting of an OIB-like asthenospheric mantle source with additions form slab fluid-melt components coupled with crustal contamination (AFC). A three-stage petrogenetic model is envisaged: (1) decompression melting and source region contamination of an OIB-like subslab asthenospheric source by slab melts of the trailing edge of the subducted Nazca Plate; (2) minor contamination of slab window melts with arc components 'stored' in the supraslab mantle wedge and/or basal continental lithosphere; (3) further modification by addition of crustal components during magma ascent. The main-plateau lavas from the eastern back-arc can be modeled by ∼ 7% partial melting of the same asthenospheric source as the influence of arc components diminishes and the intensity of mantle upwelling into the slab window decreases. All post-plateau lavas can be modeled as 1-4% partial melts of the pristine OIB-like asthenospheric source in the widening slab window.

KW - Back-arc processes

KW - Mantle chemistry

KW - Plateau basalt petrogenesis

KW - Slab window magmatism

KW - Southern patagonia

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U2 - 10.1093/petrology/42.6.1067

DO - 10.1093/petrology/42.6.1067

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