INVESTIGADORES
VUJOVICH Graciela Irene
artículos
Título:
Metamorphic evolution of migmatites from the deep Famatinian arc crust exposed in Sierras Valle Fértil-La Huerta, San Juan, Argentina.
Autor/es:
OTAMENDI, J.E., TIBALDI, A.M., VUJOVICH, G.I., VIÑAO, G.A.
Revista:
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Editorial:
Elsevier
Referencias:
Año: 2008 vol. 25 p. 313 - 335
ISSN:
0895-9811
Resumen:
Meta-supracrustal migmatitic packages in the Sierras Valle Fe´rtilLa Huerta of northwestern Argentina occur as wedge- or stripshaped
septa interlayered among mafic to intermediate igneous plutonic rocks. Meta-supracrustal rocks were metamorphosed under
granulite-facies conditions during the development of the Famatinian magmatic arc, and are among the structurally deepest rocks
exposed within the belt dominated by Ordovician plutonism. Petrographic analysis, mineral chemistry and whole rock geochemistry
of granulite-facies migmatites are used to argue that the meta-supracrustal packages comprise a sequence of pelitic to quartzo-feldspathic
sedimentary rocks that achieved peak metamorphic PT conditions of 5.27.1 kbar and 770840 C. There are no resolvable differences
in peak PT conditions for migmatites separated 70 km along strike of the Sierras Valle Fe´rtil and La Huerta, suggesting that similar
levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent
chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints
to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration
partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage
(mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heatingcooling
cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures,
and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that
when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 2025 km beneath the Ordovician surface.
Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31 and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent
chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints
to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration
partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage
(mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heatingcooling
cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures,
and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that
when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 2025 km beneath the Ordovician surface.
Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31 and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
in peak PT conditions for migmatites separated 70 km along strike of the Sierras Valle Fe´rtil and La Huerta, suggesting that similar
levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent
chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints
to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration
partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage
(mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heatingcooling
cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures,
and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that
when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 2025 km beneath the Ordovician surface.
Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31 and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent
chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints
to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration
partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage
(mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heatingcooling
cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures,
and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that
when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 2025 km beneath the Ordovician surface.
Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31 and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
PT conditions of 5.27.1 kbar and 770840 C. There are no resolvable differences
in peak PT conditions for migmatites separated 70 km along strike of the Sierras Valle Fe´rtil and La Huerta, suggesting that similar
levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent
chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints
to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration
partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage
(mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heatingcooling
cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures,
and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that
when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 2025 km beneath the Ordovician surface.
Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31 and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent
chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints
to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration
partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage
(mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heatingcooling
cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures,
and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that
when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 2025 km beneath the Ordovician surface.
Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31 and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
PT conditions for migmatites separated 70 km along strike of the Sierras Valle Fe´rtil and La Huerta, suggesting that similar
levels of the Famatinian paleo-arc crust are currently exposed in these ranges. Idioblastic poikilitic garnets displaying weak to absent
chemical zoning profiles developed at or close to the peak metamorphic stage are used in conjunction with petrogenetic grid constraints
to interpret the prograde evolution. At the time the supracrustal rocks experienced maximum thermal conditions, they underwent dehydration
partial melting. Microtextural features show that felsic melt (leucosome) back reacted with the adjacent coexisting mineral assemblage
(mesosome). These observations are interpreted as evidence that the migmatites evolved through a continuous heatingcooling
cycle with minor pressure change. This is consistent with the general lack of reaction textures denoting decompression at high temperatures,
and with the possibility that in some migmatites retrograde reactions formed staurolite. Collectively, these features indicate that
when the migmatites attained peak thermal conditions, the deepest exposed arc crust was about 2025 km beneath the Ordovician surface.
Comparing these results with metamorphic studies elsewhere in the Famatinian arc between 31 and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
and 32S. indicates that much of
the main-arc records primarily prograde PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.
PT trajectories associated with a regional contact metamorphism, but that specific locations in
the back-arc, main-arc and accretionary wedge also record post-peak retrogression during crustal exhumation. These differences are
attributed to the fact that a collisional orogeny closely followed the cessation of arc magmatism, a collision we infer to be associated
with the accretion of a Laurentian terrane to the Gondwana margin. The results of this study therefore provide important insights into
the geodynamic context of the formation and closure of the central segment of the Famatinian magmatic arc.