Tectono-metamorphic evolution of a convergent back-arc

The Famatinian orogen, Sierra de Quilmes, Sierras Pampeanas, NW Argentina

Melanie A Finch, Roberto F Weinberg, Pavlina Hasalova, Raul Becchio, Maria Gabriela Fuentes, Allen Kennedy

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Back-arcs are hot regions of enduring weakness in the hinterland of subduction zones that are commonly sites of strain localization, forming mobile belts that, in some cases, develop into mountain belts. Their evolution results from their strength, a function of thickness, heat flux, and stresses. Contractional back-arcs may be too weak to form thick crusts, whereas in other cases, they can thicken considerably and lead to mountain building. The stress and thermal histories of back-arcs can be retrieved from investigation of the relationships between deformation and metamorphism. The 490–430 Ma Famatinian orogen of the Sierras Pampeanas is associated with a back-arc that has a complex development. We focus on the Sierra de Quilmes within the northern section of the back-arc and present new structural data tied to anatexis and constrained by geochronology. We find that low-pressure–high-temperature conditions prevailed over an ∼35 m.y. thermal peak between 497 and 461 Ma, as indicated by U/Pb ages of monazite. Anatexis coincided with thrusting to the west and northwest, as evidenced by leucosomes in axial planes of folds and in thrust planes. As rocks were thrust upward, they cooled, melt solidified, and deformation localized into two major thrust zones. These record the same thrust-to-the-west or northwest kinematics as the earlier syn-anatectic deformation and ultimately placed hot rocks over cold ones. Continuous thrusting during cooling from peak metamorphism, accompanied by strain localization, is consistent with a number of shear zones in the northern Sierras Pampeanas. The low-pressure metamorphic assemblages indicate that shortening was not accompanied by pronounced crustal thickening, suggesting that the lithosphere was too hot, and the partially melted crust was too weak for substantial stacking.
Original languageEnglish
Pages (from-to)1602-1621
Number of pages20
JournalGeological Society of America Bulletin
Volume129
Issue number11-12
DOIs
Publication statusPublished - Nov 2017

Cite this

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title = "Tectono-metamorphic evolution of a convergent back-arc: The Famatinian orogen, Sierra de Quilmes, Sierras Pampeanas, NW Argentina",
abstract = "Back-arcs are hot regions of enduring weakness in the hinterland of subduction zones that are commonly sites of strain localization, forming mobile belts that, in some cases, develop into mountain belts. Their evolution results from their strength, a function of thickness, heat flux, and stresses. Contractional back-arcs may be too weak to form thick crusts, whereas in other cases, they can thicken considerably and lead to mountain building. The stress and thermal histories of back-arcs can be retrieved from investigation of the relationships between deformation and metamorphism. The 490–430 Ma Famatinian orogen of the Sierras Pampeanas is associated with a back-arc that has a complex development. We focus on the Sierra de Quilmes within the northern section of the back-arc and present new structural data tied to anatexis and constrained by geochronology. We find that low-pressure–high-temperature conditions prevailed over an ∼35 m.y. thermal peak between 497 and 461 Ma, as indicated by U/Pb ages of monazite. Anatexis coincided with thrusting to the west and northwest, as evidenced by leucosomes in axial planes of folds and in thrust planes. As rocks were thrust upward, they cooled, melt solidified, and deformation localized into two major thrust zones. These record the same thrust-to-the-west or northwest kinematics as the earlier syn-anatectic deformation and ultimately placed hot rocks over cold ones. Continuous thrusting during cooling from peak metamorphism, accompanied by strain localization, is consistent with a number of shear zones in the northern Sierras Pampeanas. The low-pressure metamorphic assemblages indicate that shortening was not accompanied by pronounced crustal thickening, suggesting that the lithosphere was too hot, and the partially melted crust was too weak for substantial stacking.",
author = "Finch, {Melanie A} and Weinberg, {Roberto F} and Pavlina Hasalova and Raul Becchio and Fuentes, {Maria Gabriela} and Allen Kennedy",
year = "2017",
month = "11",
doi = "10.1130/B31620.1",
language = "English",
volume = "129",
pages = "1602--1621",
journal = "Geological Society of America Bulletin",
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Tectono-metamorphic evolution of a convergent back-arc : The Famatinian orogen, Sierra de Quilmes, Sierras Pampeanas, NW Argentina. / Finch, Melanie A; Weinberg, Roberto F; Hasalova, Pavlina; Becchio, Raul; Fuentes, Maria Gabriela; Kennedy, Allen.

In: Geological Society of America Bulletin, Vol. 129, No. 11-12, 11.2017, p. 1602-1621.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Tectono-metamorphic evolution of a convergent back-arc

T2 - The Famatinian orogen, Sierra de Quilmes, Sierras Pampeanas, NW Argentina

AU - Finch, Melanie A

AU - Weinberg, Roberto F

AU - Hasalova, Pavlina

AU - Becchio, Raul

AU - Fuentes, Maria Gabriela

AU - Kennedy, Allen

PY - 2017/11

Y1 - 2017/11

N2 - Back-arcs are hot regions of enduring weakness in the hinterland of subduction zones that are commonly sites of strain localization, forming mobile belts that, in some cases, develop into mountain belts. Their evolution results from their strength, a function of thickness, heat flux, and stresses. Contractional back-arcs may be too weak to form thick crusts, whereas in other cases, they can thicken considerably and lead to mountain building. The stress and thermal histories of back-arcs can be retrieved from investigation of the relationships between deformation and metamorphism. The 490–430 Ma Famatinian orogen of the Sierras Pampeanas is associated with a back-arc that has a complex development. We focus on the Sierra de Quilmes within the northern section of the back-arc and present new structural data tied to anatexis and constrained by geochronology. We find that low-pressure–high-temperature conditions prevailed over an ∼35 m.y. thermal peak between 497 and 461 Ma, as indicated by U/Pb ages of monazite. Anatexis coincided with thrusting to the west and northwest, as evidenced by leucosomes in axial planes of folds and in thrust planes. As rocks were thrust upward, they cooled, melt solidified, and deformation localized into two major thrust zones. These record the same thrust-to-the-west or northwest kinematics as the earlier syn-anatectic deformation and ultimately placed hot rocks over cold ones. Continuous thrusting during cooling from peak metamorphism, accompanied by strain localization, is consistent with a number of shear zones in the northern Sierras Pampeanas. The low-pressure metamorphic assemblages indicate that shortening was not accompanied by pronounced crustal thickening, suggesting that the lithosphere was too hot, and the partially melted crust was too weak for substantial stacking.

AB - Back-arcs are hot regions of enduring weakness in the hinterland of subduction zones that are commonly sites of strain localization, forming mobile belts that, in some cases, develop into mountain belts. Their evolution results from their strength, a function of thickness, heat flux, and stresses. Contractional back-arcs may be too weak to form thick crusts, whereas in other cases, they can thicken considerably and lead to mountain building. The stress and thermal histories of back-arcs can be retrieved from investigation of the relationships between deformation and metamorphism. The 490–430 Ma Famatinian orogen of the Sierras Pampeanas is associated with a back-arc that has a complex development. We focus on the Sierra de Quilmes within the northern section of the back-arc and present new structural data tied to anatexis and constrained by geochronology. We find that low-pressure–high-temperature conditions prevailed over an ∼35 m.y. thermal peak between 497 and 461 Ma, as indicated by U/Pb ages of monazite. Anatexis coincided with thrusting to the west and northwest, as evidenced by leucosomes in axial planes of folds and in thrust planes. As rocks were thrust upward, they cooled, melt solidified, and deformation localized into two major thrust zones. These record the same thrust-to-the-west or northwest kinematics as the earlier syn-anatectic deformation and ultimately placed hot rocks over cold ones. Continuous thrusting during cooling from peak metamorphism, accompanied by strain localization, is consistent with a number of shear zones in the northern Sierras Pampeanas. The low-pressure metamorphic assemblages indicate that shortening was not accompanied by pronounced crustal thickening, suggesting that the lithosphere was too hot, and the partially melted crust was too weak for substantial stacking.

U2 - 10.1130/B31620.1

DO - 10.1130/B31620.1

M3 - Article

VL - 129

SP - 1602

EP - 1621

JO - Geological Society of America Bulletin

JF - Geological Society of America Bulletin

SN - 0016-7606

IS - 11-12

ER -