We conducted a magnetotelluric (MT) study from Paleoproterozoic Rio de la Plata Craton, in Urugua... more We conducted a magnetotelluric (MT) study from Paleoproterozoic Rio de la Plata Craton, in Uruguay, toward Paleozoic-Mesozoic Paraná Basin, in Brazil. The 850-km-long MT transect comprises 35 evenly spaced broadband electromagnetic soundings sites. In the Paraná Basin, 11 additional long-period measurements were acquired to extend the maximum depth of investigation. All data were inverted using two-and three-dimensional approaches obtaining the electrical resistivity structure from the surface down to 200 km. The Rio de la Plata Craton is >200-km thick and resistive (~2,000 Ωm). Its northern limit is electrically defined by a lithosphere scale lateral transition and lower crust conductive anomalies (1-10 Ωm) interpreted as a Paleoproterozoic suture at the southern edge of Rivera-Taquarembó Block. The latter is characterized by an approximately 100-km thick and moderate resistive (>500 Ωm) upper mantle. The Ibaré shear zone is another suture where an ocean-ocean subduction generated the 120-km thick and resistive (>1,000 Ωm) São Gabriel juvenile arc. Proceeding northward, a 70-to 80-km thick, 150-km wide, and inclined resistive zone is imaged. This zone could be remnant of an oceanic lithosphere or island arcs accreted at the southern border of Paraná Basin. The MT transect terminates within the southern Paraná Basin where a 150-to 200-km-thick less resistive lithosphere (<1,000 Ωm) may indicate refertilization processes during plate subduction and ocean closure in Neoproterozoic-Cambrian time. Our MT data support a tectonic model of NNE-SSW convergence for this segment of SW Gondwanaland.
New high-resolution airborne magnetic data of Uruguay allowed constructing new maps concerning th... more New high-resolution airborne magnetic data of Uruguay allowed constructing new maps concerning the spatial distribution of dyke swarms, main faults and other magnetic bodies, which compose the Uruguayan Shield. We combined geophysical analyses (vertical derivatives, upward continuation, Euler deconvolution), structural analyses of the magnetic maps and previous geological data in order to discriminate the main structural features of the Uruguayan Shield and contribute to a better understanding of its tectonic evolution. The magnetic maps revealed several outstanding features in the Uruguayan Shield. The Paleoproterozoic dyke swarm is larger, denser, more widespread and complex than originally thought, suggesting a possible plume origin. In addition, a new Mesozoic dyke swarm, as complex as the previous one, was identified crosscutting the Paleoproterozoic dyke swarm and the Neoproterozoic orogenic structures. Moreover, this swarm is connected to volcanic calderas in the Merín basin, and shows displacements along Neoproterozoic shear zones, in the magnetic maps, revealing its brittle reactivation during Mesozoic times. The new observations clarify how Proterozoic basement structures controlled the development of the Mesozoic rift. Paleoproterozoic dyke swarms were reactivated as normal faults and Neoproterozoic structures hindered the rift growth, deflecting the deformation in transcurrent movements. Meanwhile, the Mesozoic dyke swarm was developed in a perpendicular direction to the Neoproterozoic structures. Moreover, these findings contradict the current rift model for Uruguay and rise a new model in which the Mesozoic rift developed as two rift basins connected by a central transfer zone, generated by the reactivation of Dom Feliciano Belt structures, between the Sierra Ballena and Sarandí del Yí Shear Zones.
This dataset presents .edi files from 35 magnetotelluric broadband and 11 long period soundings a... more This dataset presents .edi files from 35 magnetotelluric broadband and 11 long period soundings across central Uruguay and southern Brazil. This data collection was financially supported by FAPESP Thematic Projects 2012/06082-6 and 2009/50493-8. Impedances in this new version (2.2) are in field units instead of SI (version 1).
A U-Pb SHRIMP zircon geochronological study was carried out in the Nico Pérez Terrane in the cent... more A U-Pb SHRIMP zircon geochronological study was carried out in the Nico Pérez Terrane in the central-eastern portion of Uruguay with the aim of constraining its geological evolution and its cratonic affinity. Nico Pérez Terrane is made up by a mosaic of tectonic blocks with diferente lithologies and sizes. This terrane is limited to the west by the Piedra Alta Terrane through the Sarandí del Yí shear zone, and to the east, is in tectonic contact through the Retamosa thrust with the Dom Feliciano Belt (Brasiliano orogenic cycle). Lithologically, the Nico Pérez Terrane is composed by medium to high grade metamorphic rock contained in three tectonic blocks (Pavas, Valentines and Rivera blocks) represented mainly by granitoids, as well as ortho and parametamorphic rocks, such as amphibolites, metapyroxenites, BIFs, schists, quartzites with fuchsite, among others. Archean inheritance, Rhyacian, Statherian, and Neoproterozoic magmatic ages are reported here. Similar ages, which show Archa...
SOLIS DE MATAOJO GRANITIC COMPLEX: EVIDENCES OF SINCOLLISIONAL MAGMATISM RELATED TO SUBDUCTION. T... more SOLIS DE MATAOJO GRANITIC COMPLEX: EVIDENCES OF SINCOLLISIONAL MAGMATISM RELATED TO SUBDUCTION. The scope is to provide a model for the génesis and emplacement of the Solis de Matapjo Granitic Complex (SW Dom Feliciano Belt). A subsequent period to continental colusión, with generation of calk-alkaline magmatism related to oceanic crust dehydration, is proposed.
The aim of this work is to propose a new stratigraphic scheme of the Barriga Negra Formation, in ... more The aim of this work is to propose a new stratigraphic scheme of the Barriga Negra Formation, in order to solve the controversies in one of the most discussed units of Uruguay. Here, we introduce a new map (unmodified since 1984) and amend the stratigraphic profile for the Barriga Negra Formation, establishing the correct sequence, order and thickness, dividing it in four members (Volcaniclastic, Arkosic Conglomerate, Calcareous Conglomerate and Petromictic Conglomerate Member). We describe by first time the presence of basal volcanic and volcanoclastic rocks that implies a tectonic active environment. Volcaniclastic rock dating yield an U-Pb concordia age of 633 ± 3.4 Ma. Moreover, we show that this unit has no stratigraphic continuity with other units that previously were used to constrain its stratigraphic position, age and paleoenvironment. We confirm unequivocally that the unit is as a continental conglomeratic sequence deposited in arid and active tectonic conditions, and not transitional passive margin deposits as some works claim. Finally, we revisit the metamorphism, deformation, stratigraphy, structural relationships of this unit and identify new basement units. As consequence of this new evidence, we reexamine its correlation with other regional units. This work is also a key to understand the chaotic stratigraphic proposals of Uruguay..
New geologic and geochronologic data of Paso del Dragón Complex (PDC) located at Northeastern Uru... more New geologic and geochronologic data of Paso del Dragón Complex (PDC) located at Northeastern Uruguay is analyzed. Two lithodemic units are described and characterized, La Micaela Schists and Cerro La Tuna Serpentinites. La Micaela Schists represent 80% of PDC and it comprises a metavolcano-sedimentary succession poly-deformed, composed by muscovite-quartz-feldspathic schists, quartzites, and felsic meta-volcanic rocks. Cerro La Tuna Serpentinites represents 20% of PDC and it comprises mafic-ultramafic rocks, also deformed and metamorphosed, composed by serpentinites, varied magnesian schists, hosted by La Micaela Schists. The complex is hosted to the north and west by the Granitic belt of the Dom Feliciano Belt that includes poly-intrusive plutons known from south to north as Aiguá, Cuchilla Dionisio and Sierra de los Ríos batholiths classified as high-K calc-alkaline pre-to post-collisional granitoids. Relevant U-Pb LA-ICP-MS analyses of metamorphic/detrital zircon grains from migmatitic-gneissic basement suggest an age of ca. 668 Ma for the metamorphic event associated with the migmatization process. The deposition and metamorphism age for La Micaela Schists lithodeme are ca. 590 Ma and 570 Ma respectively. The Complex is interpreted as remains of sedimentary and magmatic units generated in an arc-related environment tectonically emplaced within the granites. Their generation, deformation and metamorphism, mainly of Ediacaran age, are associated to the Western Gondwana assembly. This thrust sheet could be regarded as a dismembered ophiolite as previously suggested by other authors.
Highlights-Mesozoic mafic dykes and sills related to the Paraná Magmatic Province occur in the ce... more Highlights-Mesozoic mafic dykes and sills related to the Paraná Magmatic Province occur in the central north portion of Uruguay.-According to their geochemical behavior can be distinguished two groups of sills and related dykes that underwent different evolutionary processes-Isotopic data and trace element geochemistry point out an enriched mantle source for both groups-The source shows an important subduction and crustal signature
ABSTRACT: This work is the result of a multiyear effort to use field geology to describe litholog... more ABSTRACT: This work is the result of a multiyear effort to use field geology to describe lithologies, to establish contact relationships and to create a sketch of the tectonic evolution of the Meso- to Neoproterozoic metasedimentary successions within the Schist Belt of the Dom Feliciano Belt. This low-grade metamorphic cover rests on the high-grade metamorphic basement of the La China and Las Tetas complexes. This basement is Archean-Paleoproterozoic in age. The Schist Belt is overlapped unconformably by the Barriga Negra formation. The Lavalleja complex and the Barriga Negra formation both deformed together during the D2 deformation event (~ 570 -540 Ma), but the Barriga Negra only partially recorded the D2 transpressive event, whereas the Lavalleja complex was affected by both the D1 tangential event and the D2 event. Event D1 would have developed a fold nappe with vergence to the south. This hypothesis is supported by different structures: (i) recumbent and upright folds oriente...
We conducted a magnetotelluric (MT) study from Paleoproterozoic Rio de la Plata Craton, in Urugua... more We conducted a magnetotelluric (MT) study from Paleoproterozoic Rio de la Plata Craton, in Uruguay, toward Paleozoic-Mesozoic Paraná Basin, in Brazil. The 850-km-long MT transect comprises 35 evenly spaced broadband electromagnetic soundings sites. In the Paraná Basin, 11 additional long-period measurements were acquired to extend the maximum depth of investigation. All data were inverted using two-and three-dimensional approaches obtaining the electrical resistivity structure from the surface down to 200 km. The Rio de la Plata Craton is >200-km thick and resistive (~2,000 Ωm). Its northern limit is electrically defined by a lithosphere scale lateral transition and lower crust conductive anomalies (1-10 Ωm) interpreted as a Paleoproterozoic suture at the southern edge of Rivera-Taquarembó Block. The latter is characterized by an approximately 100-km thick and moderate resistive (>500 Ωm) upper mantle. The Ibaré shear zone is another suture where an ocean-ocean subduction generated the 120-km thick and resistive (>1,000 Ωm) São Gabriel juvenile arc. Proceeding northward, a 70-to 80-km thick, 150-km wide, and inclined resistive zone is imaged. This zone could be remnant of an oceanic lithosphere or island arcs accreted at the southern border of Paraná Basin. The MT transect terminates within the southern Paraná Basin where a 150-to 200-km-thick less resistive lithosphere (<1,000 Ωm) may indicate refertilization processes during plate subduction and ocean closure in Neoproterozoic-Cambrian time. Our MT data support a tectonic model of NNE-SSW convergence for this segment of SW Gondwanaland.
New high-resolution airborne magnetic data of Uruguay allowed constructing new maps concerning th... more New high-resolution airborne magnetic data of Uruguay allowed constructing new maps concerning the spatial distribution of dyke swarms, main faults and other magnetic bodies, which compose the Uruguayan Shield. We combined geophysical analyses (vertical derivatives, upward continuation, Euler deconvolution), structural analyses of the magnetic maps and previous geological data in order to discriminate the main structural features of the Uruguayan Shield and contribute to a better understanding of its tectonic evolution. The magnetic maps revealed several outstanding features in the Uruguayan Shield. The Paleoproterozoic dyke swarm is larger, denser, more widespread and complex than originally thought, suggesting a possible plume origin. In addition, a new Mesozoic dyke swarm, as complex as the previous one, was identified crosscutting the Paleoproterozoic dyke swarm and the Neoproterozoic orogenic structures. Moreover, this swarm is connected to volcanic calderas in the Merín basin, and shows displacements along Neoproterozoic shear zones, in the magnetic maps, revealing its brittle reactivation during Mesozoic times. The new observations clarify how Proterozoic basement structures controlled the development of the Mesozoic rift. Paleoproterozoic dyke swarms were reactivated as normal faults and Neoproterozoic structures hindered the rift growth, deflecting the deformation in transcurrent movements. Meanwhile, the Mesozoic dyke swarm was developed in a perpendicular direction to the Neoproterozoic structures. Moreover, these findings contradict the current rift model for Uruguay and rise a new model in which the Mesozoic rift developed as two rift basins connected by a central transfer zone, generated by the reactivation of Dom Feliciano Belt structures, between the Sierra Ballena and Sarandí del Yí Shear Zones.
This dataset presents .edi files from 35 magnetotelluric broadband and 11 long period soundings a... more This dataset presents .edi files from 35 magnetotelluric broadband and 11 long period soundings across central Uruguay and southern Brazil. This data collection was financially supported by FAPESP Thematic Projects 2012/06082-6 and 2009/50493-8. Impedances in this new version (2.2) are in field units instead of SI (version 1).
A U-Pb SHRIMP zircon geochronological study was carried out in the Nico Pérez Terrane in the cent... more A U-Pb SHRIMP zircon geochronological study was carried out in the Nico Pérez Terrane in the central-eastern portion of Uruguay with the aim of constraining its geological evolution and its cratonic affinity. Nico Pérez Terrane is made up by a mosaic of tectonic blocks with diferente lithologies and sizes. This terrane is limited to the west by the Piedra Alta Terrane through the Sarandí del Yí shear zone, and to the east, is in tectonic contact through the Retamosa thrust with the Dom Feliciano Belt (Brasiliano orogenic cycle). Lithologically, the Nico Pérez Terrane is composed by medium to high grade metamorphic rock contained in three tectonic blocks (Pavas, Valentines and Rivera blocks) represented mainly by granitoids, as well as ortho and parametamorphic rocks, such as amphibolites, metapyroxenites, BIFs, schists, quartzites with fuchsite, among others. Archean inheritance, Rhyacian, Statherian, and Neoproterozoic magmatic ages are reported here. Similar ages, which show Archa...
SOLIS DE MATAOJO GRANITIC COMPLEX: EVIDENCES OF SINCOLLISIONAL MAGMATISM RELATED TO SUBDUCTION. T... more SOLIS DE MATAOJO GRANITIC COMPLEX: EVIDENCES OF SINCOLLISIONAL MAGMATISM RELATED TO SUBDUCTION. The scope is to provide a model for the génesis and emplacement of the Solis de Matapjo Granitic Complex (SW Dom Feliciano Belt). A subsequent period to continental colusión, with generation of calk-alkaline magmatism related to oceanic crust dehydration, is proposed.
The aim of this work is to propose a new stratigraphic scheme of the Barriga Negra Formation, in ... more The aim of this work is to propose a new stratigraphic scheme of the Barriga Negra Formation, in order to solve the controversies in one of the most discussed units of Uruguay. Here, we introduce a new map (unmodified since 1984) and amend the stratigraphic profile for the Barriga Negra Formation, establishing the correct sequence, order and thickness, dividing it in four members (Volcaniclastic, Arkosic Conglomerate, Calcareous Conglomerate and Petromictic Conglomerate Member). We describe by first time the presence of basal volcanic and volcanoclastic rocks that implies a tectonic active environment. Volcaniclastic rock dating yield an U-Pb concordia age of 633 ± 3.4 Ma. Moreover, we show that this unit has no stratigraphic continuity with other units that previously were used to constrain its stratigraphic position, age and paleoenvironment. We confirm unequivocally that the unit is as a continental conglomeratic sequence deposited in arid and active tectonic conditions, and not transitional passive margin deposits as some works claim. Finally, we revisit the metamorphism, deformation, stratigraphy, structural relationships of this unit and identify new basement units. As consequence of this new evidence, we reexamine its correlation with other regional units. This work is also a key to understand the chaotic stratigraphic proposals of Uruguay..
New geologic and geochronologic data of Paso del Dragón Complex (PDC) located at Northeastern Uru... more New geologic and geochronologic data of Paso del Dragón Complex (PDC) located at Northeastern Uruguay is analyzed. Two lithodemic units are described and characterized, La Micaela Schists and Cerro La Tuna Serpentinites. La Micaela Schists represent 80% of PDC and it comprises a metavolcano-sedimentary succession poly-deformed, composed by muscovite-quartz-feldspathic schists, quartzites, and felsic meta-volcanic rocks. Cerro La Tuna Serpentinites represents 20% of PDC and it comprises mafic-ultramafic rocks, also deformed and metamorphosed, composed by serpentinites, varied magnesian schists, hosted by La Micaela Schists. The complex is hosted to the north and west by the Granitic belt of the Dom Feliciano Belt that includes poly-intrusive plutons known from south to north as Aiguá, Cuchilla Dionisio and Sierra de los Ríos batholiths classified as high-K calc-alkaline pre-to post-collisional granitoids. Relevant U-Pb LA-ICP-MS analyses of metamorphic/detrital zircon grains from migmatitic-gneissic basement suggest an age of ca. 668 Ma for the metamorphic event associated with the migmatization process. The deposition and metamorphism age for La Micaela Schists lithodeme are ca. 590 Ma and 570 Ma respectively. The Complex is interpreted as remains of sedimentary and magmatic units generated in an arc-related environment tectonically emplaced within the granites. Their generation, deformation and metamorphism, mainly of Ediacaran age, are associated to the Western Gondwana assembly. This thrust sheet could be regarded as a dismembered ophiolite as previously suggested by other authors.
Highlights-Mesozoic mafic dykes and sills related to the Paraná Magmatic Province occur in the ce... more Highlights-Mesozoic mafic dykes and sills related to the Paraná Magmatic Province occur in the central north portion of Uruguay.-According to their geochemical behavior can be distinguished two groups of sills and related dykes that underwent different evolutionary processes-Isotopic data and trace element geochemistry point out an enriched mantle source for both groups-The source shows an important subduction and crustal signature
ABSTRACT: This work is the result of a multiyear effort to use field geology to describe litholog... more ABSTRACT: This work is the result of a multiyear effort to use field geology to describe lithologies, to establish contact relationships and to create a sketch of the tectonic evolution of the Meso- to Neoproterozoic metasedimentary successions within the Schist Belt of the Dom Feliciano Belt. This low-grade metamorphic cover rests on the high-grade metamorphic basement of the La China and Las Tetas complexes. This basement is Archean-Paleoproterozoic in age. The Schist Belt is overlapped unconformably by the Barriga Negra formation. The Lavalleja complex and the Barriga Negra formation both deformed together during the D2 deformation event (~ 570 -540 Ma), but the Barriga Negra only partially recorded the D2 transpressive event, whereas the Lavalleja complex was affected by both the D1 tangential event and the D2 event. Event D1 would have developed a fold nappe with vergence to the south. This hypothesis is supported by different structures: (i) recumbent and upright folds oriente...
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