Thermodynamic modelling of continental arc‑adjacent magmatism: the Loicas Trough, N. Patagonia, Argentina
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Thermodynamic modelling of continental arc‑adjacent magmatism : the Loicas Trough, N. Patagonia, Argentina. / Traun, Marie Katrine; Waterton, P.; Søager, N.; Waight, T. E.; Iannelli, S. B.; Folguera, A.; Litvak, V. D.
I: Contributions to Mineralogy and Petrology, Bind 179, Nr. 4, 2024.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Thermodynamic modelling of continental arc‑adjacent magmatism
T2 - the Loicas Trough, N. Patagonia, Argentina
AU - Traun, Marie Katrine
AU - Waterton, P.
AU - Søager, N.
AU - Waight, T. E.
AU - Iannelli, S. B.
AU - Folguera, A.
AU - Litvak, V. D.
PY - 2024
Y1 - 2024
N2 - Continental arcs are associated with volcanism concentrated into two main belts—the main arc and back arc, often separated by fold and thrust belts. The Loicas Trough, Argentina, is a post-orogenic extensional feature that obliquely cuts the fold and thrust belts. The trough hosts large Pliocene–Holocene volcanic centres, including Domuyo and Tromen, that lie between the main arc and back arc and thus provide a rare window into this setting. We present major and trace element data for the Loicas Trough, which we combine with geochemical modelling using the Magma Chamber Simulator (MCS) to explore the origin and evolution of the volcanism. The lavas display a wide continuous range from alkaline basalts to subalkaline rhyolites. Trace elements reveal variable extents of arc enrichment (2 < Nb/U < 28), which correlate with proximity to the trench and differentiation indices. Our results and MCS models indicate that the Loicas Trough parental magmas formed from compositionally zoned mantle. Best-fit models indicate that the differentiation occurs at middle and upper crustal levels, in sharp contrast to lower crustal hot zones beneath main arcs. Assimilation of partial crustal melts drives compositional evolution and obscures source signatures. Pure or high fraction end-member partial crustal melts are also identified at Domuyo based on their low Ba (~ 250 ppm) and moderate Sc contents (~ 8 ppm). We find evidence of similar lavas in transtensional settings adjacent to continental arcs worldwide, which do not adhere to the main versus back arc volcanism binary. We suggest the term arc-adjacent magmatism, where compositions are mainly controlled by extensive assimilation and reworking in the middle to upper crust.
AB - Continental arcs are associated with volcanism concentrated into two main belts—the main arc and back arc, often separated by fold and thrust belts. The Loicas Trough, Argentina, is a post-orogenic extensional feature that obliquely cuts the fold and thrust belts. The trough hosts large Pliocene–Holocene volcanic centres, including Domuyo and Tromen, that lie between the main arc and back arc and thus provide a rare window into this setting. We present major and trace element data for the Loicas Trough, which we combine with geochemical modelling using the Magma Chamber Simulator (MCS) to explore the origin and evolution of the volcanism. The lavas display a wide continuous range from alkaline basalts to subalkaline rhyolites. Trace elements reveal variable extents of arc enrichment (2 < Nb/U < 28), which correlate with proximity to the trench and differentiation indices. Our results and MCS models indicate that the Loicas Trough parental magmas formed from compositionally zoned mantle. Best-fit models indicate that the differentiation occurs at middle and upper crustal levels, in sharp contrast to lower crustal hot zones beneath main arcs. Assimilation of partial crustal melts drives compositional evolution and obscures source signatures. Pure or high fraction end-member partial crustal melts are also identified at Domuyo based on their low Ba (~ 250 ppm) and moderate Sc contents (~ 8 ppm). We find evidence of similar lavas in transtensional settings adjacent to continental arcs worldwide, which do not adhere to the main versus back arc volcanism binary. We suggest the term arc-adjacent magmatism, where compositions are mainly controlled by extensive assimilation and reworking in the middle to upper crust.
KW - Andes
KW - Continental volcanism
KW - MELTS
KW - Magma chamber simulator
KW - Transtension
KW - Whole rock geochemistry
KW - andes
KW - continental volcanism
KW - magma chamber simulator
KW - melts
KW - transtension
KW - whole rock geochemistry
U2 - 10.1007/s00410-023-02082-0
DO - 10.1007/s00410-023-02082-0
M3 - Journal article
VL - 179
JO - Contributions to Mineralogy and Petrology
JF - Contributions to Mineralogy and Petrology
SN - 0010-7999
IS - 4
ER -
ID: 376932265