Subduction controls on Miocene back-arc lavas from Sierra de Huantraico and La Matancilla, Argentina and new 40Ar/39Ar dating from the Mendoza Region, Argentina
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Subduction controls on Miocene back-arc lavas from Sierra de Huantraico and La Matancilla, Argentina and new 40Ar/39Ar dating from the Mendoza Region, Argentina. / Dyhr, Charlotte Thorup; Holm, Paul Martin; Llambias, Eduardo J.; Scherstén, Anders.
In: Lithos, Vol. 179, 2013, p. 67-83.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - Subduction controls on Miocene back-arc lavas from Sierra de Huantraico and La Matancilla, Argentina and new 40Ar/39Ar dating from the Mendoza Region, Argentina
AU - Dyhr, Charlotte Thorup
AU - Holm, Paul Martin
AU - Llambias, Eduardo J.
AU - Scherstén, Anders
PY - 2013
Y1 - 2013
N2 - Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquén 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 LaMatancilla plateaus, including new 40Ar/39Ar 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 (2σ) of alkali olivine basalts with OIB-type incompatible trace element enrichments at La Matancilla (~36.50°S) provide evidence for the presence of back-arc mantle devoid of subduction-related components.In contrast, the lower Huantraico lavas (~37.30°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. 87Sr/86Sr, 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, adecreasing 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.
AB - Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquén 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 LaMatancilla plateaus, including new 40Ar/39Ar 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 (2σ) of alkali olivine basalts with OIB-type incompatible trace element enrichments at La Matancilla (~36.50°S) provide evidence for the presence of back-arc mantle devoid of subduction-related components.In contrast, the lower Huantraico lavas (~37.30°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. 87Sr/86Sr, 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, adecreasing 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.
U2 - 10.1016/j.lithos.2013.08.007
DO - 10.1016/j.lithos.2013.08.007
M3 - Journal article
VL - 179
SP - 67
EP - 83
JO - Lithos
JF - Lithos
SN - 0024-4937
ER -
ID: 45830709