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Subduction controls on Miocene back-arc lavas from Sierra de Huantraico and La Matancilla and new Ar-40/Ar-39 dating from the Mendoza Region, Argentina

Dyhr, Charlotte T. ; Holm, Paul M. ; Llambias, Eduardo J. and Scherstén, Anders LU (2013) In Lithos 179. p.67-83
Abstract
Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquen has been widespread from the Miocene to historic times. We present a detailed investigation of profiles through two of the major Miocene volcanic areas of the region, the neighboring Huantraico and La Matancilla plateaus, including new Ar-40/Ar-39 age results of major and trace elements as well as Nd, Sr and Pb isotopic data. Four million years of eruptions from 24.4 +/- 0.3 Ma (2 sigma) of alkali olivine basalts with OIB-type incompatible trace element enrichments at La Matancilla (similar to 36.50 degrees S) provide evidence for the presence of back-arc mantle devoid of subduction-related components. In contrast, the lower Huantraico lavas (similar to 37.30... (More)
Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquen has been widespread from the Miocene to historic times. We present a detailed investigation of profiles through two of the major Miocene volcanic areas of the region, the neighboring Huantraico and La Matancilla plateaus, including new Ar-40/Ar-39 age results of major and trace elements as well as Nd, Sr and Pb isotopic data. Four million years of eruptions from 24.4 +/- 0.3 Ma (2 sigma) of alkali olivine basalts with OIB-type incompatible trace element enrichments at La Matancilla (similar to 36.50 degrees S) provide evidence for the presence of back-arc mantle devoid of subduction-related components. In contrast, the lower Huantraico lavas (similar to 37.30 degrees S) require an atypical back-arc mantle, almost devoid of arc-like components (e.g. low La/Ta = 15-18 and Ba/La = 12-18), but with a more depleted isotopic signature (e.g. Sr-87/Sr-86, 0.7033-0.7037) than observed elsewhere in the Andean back-arc. The Lower to Upper Series development in the Huantraico sequence represents a gradual change from basaltic to trachyandesitic back-arc lavas with a weak but temporally increasing arc geochemical signature (e.g. La/Ta = 15-21; Ba/La = 12-45), which is accompanied by Sr, Nd and Pb isotopic compositions approaching present day values of the Andes arc. The compositional change is accompanied by a gradually decreasing role for garnet in the mantle source, a decreasing degree of melting, but also simultaneously increasing influence from subducted fluids, probably as the slab geometry changes through time. The volcanism at Huantraico ceased when a flat slab was established around 15 Ma. (C) 2013 Elsevier B.V. All fights reserved. (Less)
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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Back-arc/arc transition, Flat slab subduction, Ar-40/Ar-39 dating
in
Lithos
volume
179
pages
67 - 83
publisher
Elsevier
external identifiers
  • wos:000328592900006
  • scopus:84878119883
ISSN
0024-4937
DOI
10.1016/j.lithos.2013.08.007
language
English
LU publication?
yes
id
0ebe25f5-3fee-4420-b52d-8afb288a948a (old id 4272127)
date added to LUP
2016-04-01 10:55:19
date last changed
2022-02-17 22:35:14
@article{0ebe25f5-3fee-4420-b52d-8afb288a948a,
  abstract     = {{Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquen has been widespread from the Miocene to historic times. We present a detailed investigation of profiles through two of the major Miocene volcanic areas of the region, the neighboring Huantraico and La Matancilla plateaus, including new Ar-40/Ar-39 age results of major and trace elements as well as Nd, Sr and Pb isotopic data. Four million years of eruptions from 24.4 +/- 0.3 Ma (2 sigma) of alkali olivine basalts with OIB-type incompatible trace element enrichments at La Matancilla (similar to 36.50 degrees S) provide evidence for the presence of back-arc mantle devoid of subduction-related components. In contrast, the lower Huantraico lavas (similar to 37.30 degrees S) require an atypical back-arc mantle, almost devoid of arc-like components (e.g. low La/Ta = 15-18 and Ba/La = 12-18), but with a more depleted isotopic signature (e.g. Sr-87/Sr-86, 0.7033-0.7037) than observed elsewhere in the Andean back-arc. The Lower to Upper Series development in the Huantraico sequence represents a gradual change from basaltic to trachyandesitic back-arc lavas with a weak but temporally increasing arc geochemical signature (e.g. La/Ta = 15-21; Ba/La = 12-45), which is accompanied by Sr, Nd and Pb isotopic compositions approaching present day values of the Andes arc. The compositional change is accompanied by a gradually decreasing role for garnet in the mantle source, a decreasing degree of melting, but also simultaneously increasing influence from subducted fluids, probably as the slab geometry changes through time. The volcanism at Huantraico ceased when a flat slab was established around 15 Ma. (C) 2013 Elsevier B.V. All fights reserved.}},
  author       = {{Dyhr, Charlotte T. and Holm, Paul M. and Llambias, Eduardo J. and Scherstén, Anders}},
  issn         = {{0024-4937}},
  keywords     = {{Back-arc/arc transition; Flat slab subduction; Ar-40/Ar-39 dating}},
  language     = {{eng}},
  pages        = {{67--83}},
  publisher    = {{Elsevier}},
  series       = {{Lithos}},
  title        = {{Subduction controls on Miocene back-arc lavas from Sierra de Huantraico and La Matancilla and new Ar-40/Ar-39 dating from the Mendoza Region, Argentina}},
  url          = {{http://dx.doi.org/10.1016/j.lithos.2013.08.007}},
  doi          = {{10.1016/j.lithos.2013.08.007}},
  volume       = {{179}},
  year         = {{2013}},
}