Papers by Pedro Oyhantcabal
Supplementary electonic material 1. Petrography description of some granitic plutons and stocks c... more Supplementary electonic material 1. Petrography description of some granitic plutons and stocks cropping out at both sides of the Sierra Ballena Shear Zone in the south-eastern section of the Dom Feliciano Belt in Uruguay. Supplementary electronic material 2. Processing and analytical methods implemented during the laboratory processing of the samples described in this manuscript.
Journal of South American Earth Sciences, Apr 1, 2021
Abstract The Sierra de Aguirre Fm. in southern Uruguay constitutes one of several post-collisiona... more Abstract The Sierra de Aguirre Fm. in southern Uruguay constitutes one of several post-collisional basins of the Dom Feliciano Belt, preserving an important volcanic record associated with this protracted stage of the orogenic system. This study combines new stratigraphic, structural, geochronological and isotopic geochemical results, together with a reassessment of the available geochemical data, to present new insights in the evolution and sources of the basin, as well as a contextualization of it within the post-collisional development of the belt. The opening of the basin was related to a major discontinuity within the belt, with geometrical features suggesting an inverted half-graben structure. Stratigraphic and petrographic studies indicate that the Sierra de Aguirre Fm. preserves the original unconformity with its basement, and represent distal volcanic deposits. U–Pb SHRIMP-IIe zircon ages establish an interval of ca. 10 m.y. for the filling of the basin, between 581.7 ± 5.1 Ma and 571 ± 8 Ma. After the end of deposition, the basin underwent folding associated with the development of axial plane cleavage under lower greenschist facies conditions. This event is interpreted to represent regional transpression recorded also in nearby shear zones between 570 and 560 Ma, as constrained by new K–Ar ages in muscovite and white mica fine fractions. Geochemical and isotopic signature indicate dominant crustal sources for the volcanism, compatible with the basement of the eastern domain of the Dom Feliciano Belt, supporting a trend also observed in the coeval plutonic magmatism.
Journal of South American Earth Sciences, Jun 1, 2021
International Journal of Earth Sciences, Dec 26, 2017
Journal of South American Earth Sciences, Dec 1, 2021
Precambrian Research, Jun 1, 2020
Regional geology reviews, 2018
The Nico Perez Terrane of Uruguay and southeastern Brazil is characterized by an important compon... more The Nico Perez Terrane of Uruguay and southeastern Brazil is characterized by an important component of Archean crustal growth and extensive post-Archean crustal reworking recorded in Paleoproterozoic zircon magmatic crystallization ages in widely distributed granitic orthogneisses. Supracrustal blocks of an older Neoarchean to Siderian sedimentary cover including BIFs, quartzites and marbles are preserved only as minor relics. Additionally, an intraplate Mesoproterozoic record includes anorthosite complexes, metagabbros, amphibolites, felsic volcanic rocks and sediments assumed to correspond to a stable platform cover. Rocks with similar isotopic features occur also as basement inliers and roof pendants in the batholiths of the Dom Feliciano Belt. Two different subterranes are recognized in the Nico Perez Terrane, separated by the north-northeast-trending Cacapava–Sierra de Sosa Shear Zone. The granulite-facies Valentines Rivera and Santa Maria Chico granulitic complexes crop out in the western side of the shear zone and were less reworked during the Neoproterozoic, while the Pavas Block of Uruguay and several basement inliers in the Tijucas Terrane and Pelotas Batholith of Brazil were strongly reworked. Cooling ages, extensive shear zones and granite intrusions document this reworking that was probably facilitated by a thin lithosphere. The Nico Perez Terrane represents a fragment of the Congo Craton separated during the Neoproterozoic.
Journal of the Geological Society, Mar 7, 2017
Earth-Science Reviews, Oct 1, 2018
Journal of the Geological Society, Oct 28, 2009
... Scientific Editing By Quentin Crowley. Next Section. Abstract: New UPb sensitive high ... 57... more ... Scientific Editing By Quentin Crowley. Next Section. Abstract: New UPb sensitive high ... 571 ± 8 Ma). Transpression and coeval high-K calc-alkaline magmatism is recorded in the Maldonado granite dated at 564 ± 7 Ma. The following ...
Regional geology reviews, 2018
Crustal-scale shear zones are ubiquitous in most Brasiliano–Pan-African belts of southwestern Gon... more Crustal-scale shear zones are ubiquitous in most Brasiliano–Pan-African belts of southwestern Gondwana and they resulted from the assembly of the Rio de la Plata, Congo and Kalahari cratons. In the Dom Feliciano Belt, the Sierra Ballena-Dorsal do Cangucu-Major Gercino shear zone system and Sarandi del Yi Shear Zone are the most prominent structures, and they share a common history with shear zones of the Kaoko Belt, such as the Purros and Three Palms Mylonite Zones. The Purros Mylonite Zone, in turn, can be traced further south in the Damara Belt, where it is correlated with the Ogden Mylonite Zone. All these orogen-parallel shear zones underwent ductile deformation mostly at c. 630–580 Ma. However, further shearing is recorded in both the Kaoko and Dom Feliciano Belts at c. 550 Ma, thus being coeval with shearing along the Colenso Fault of the Saldania Belt. Though the Brasiliano–Pan-African Orogeny led to a relative stabilization of the South American and African continental crust by the early Paleozoic, shear zones were subsequently reactivated under brittle conditions during the Phanerozoic. These fault zones were particularly active during the opening of the South Atlantic Ocean in the Cretaceous, controlling magmatism emplacement, basin development and crustal exhumation. Shear zones thus played a major role not only during the Neoproterozoic assembly but also during the subsequent break-up of Gondwana.
Regional geology reviews, 2018
The Dom Feliciano Belt is an orogenic association that extends from southern Brazil to Uruguay pa... more The Dom Feliciano Belt is an orogenic association that extends from southern Brazil to Uruguay parallel to the Atlantic coastline for over 1100 km. It was assembled in the Neoproterozoic, during the Brasiliano orogenic cycle, and is the result of interaction between the Rio de la Plata, Congo and Kalahari cratons, together with several microplates, juxtaposed along major shear zones. Along its extension, the Dom Feliciano Belt is exposed in three sectors: in the Brazilian states of Santa Catarina and Rio Grande do Sul, and in Uruguay. The blocks that acted as direct forelands to the belt in South America are smaller fragments to the main cratons: Luis Alves and Nico Perez. Three main lithotectonic domains are recognized in the belt, from east to west: a granitic batholith, a metasedimentary sequence and an association of foreland basins. Basement inliers are common, and evidence intense reworking and magmatism during the Neoproterozoic. Cryogenian to Ediacaran granitogenesis is widespread and voluminous, and usually displays an evolutionary tendency from medium- to high-K calc-alkaline, finishing with alkaline magmatism. The early evolution of the Dom Feliciano Belt is recorded in the Sao Gabriel Terrane, in which convergent tectonics is associated with intense juvenile magmatism, ophiolite complexes and accretion between 870 and 680 Ma. This is followed by two more deformational phases, identified in all three sectors. A convergent phase is associated with the deformation of the metavolcano-sedimentary complexes, shear zone nucleation and granitic magmatism associated with high-grade collisional metamorphism. This stage is constrained between c. 650–620 Ma in Santa Catarina and Rio Grande do Sul, and between c. 630–600 Ma in Uruguay. The last stage marks a transition to strike-slip deformation, with common shear zone reactivation associated with refolding in the metamorphic associations and widespread post-collisional granitic and volcanic magmatism. This phase is predominant from 610 to 550 Ma. The opening of the foreland basins was initiated during this period, probably associated with transtension along the main structures. Late-stage deformation and magmatism is common until 550–540 Ma. Abundant geochronological data have been added to the Dom Feliciano Belt in the last decades, leading to more precise time constraints for most of the geologic processes in the orogen. Details of its tectonic model, however, are still matters of debate, in terms of both the setting of its main units and its position into the assembly of southwestern Gondwana.
Precambrian Research, Feb 1, 2022
EGUGA, Apr 1, 2012
ABSTRACT Different building stones of the Cologne Cathedral show a large variation of weathering ... more ABSTRACT Different building stones of the Cologne Cathedral show a large variation of weathering phenomena. The Drachenfels trachyte, which was the construction material for the medieval part of the cathedral, shows significant surface deterioration, back-weathering coexisting with flaking, crumbling or the massive formation of gypsum crusts. Wolff (1992) first mentioned the negative interferences between the Schlaitdorfer sandstone and the Londorfer basalt lava or the Drachenfels trachyte and the Krensheimer muschelkalk. Crust formation on limestone, sandstone, and volcanic rock from the Cologne Cathedral as well as from the Xanten and Altenberg Cathedral are investigated. These three buildings are located in different areas and exposed to varying industrial, urban, and rural environmental situations. The material investigated range from dark grey to black framboidal crusts. This 3 to 10 mm thick cauliflower-like form of gypsum crust incorporates particles from the pollution fluxes. It covers the stone surface and mainly occurs at sites protected from wind and direct rain. Secondly, thin laminar black crusts trace the stone surface and may cover complete sections of the building's structure not necessarily preferring protected sites. This kind of crust seems to have very strong bonds between the thin black crust and the stone surface. Major and trace element distribution show an enrichment of sulfur, indicating the presence of gypsum, lead and other typical pollutants (arsenic, antimony, bismuth, tin etc.), which generally can be linked to traffic and industry. This indicates that even though the SO2 emission has decreased due to i.e. stronger regulations of waste incineration plants and the ban of leaded petrol, the pollutants are still present in the crusts on the building stones. From systematic SEM observations it becomes evident that the total amount of pollution is less pronounced in the Altenberg and Xanten Cathedrals as compared with the Cologne Cathedral. The formation of gypsum occurs at lower amounts in Altenberg, which correlates well with the measured SO2 content. On the other hand, the increasing H2O content in the trachyte and the crusts correlates well with an increasing phyllosilicate formation. Through the combination of different analytical techniques it was possible to clearly distinguish samples from the industrial or rural environment. If the data is compared to actual pollutant emissions, the analyzed samples imply present but also past pollution fluxes. Thus, the soiled zones of the built environment can function as environmental indicators.
Journal of Metamorphic Geology
The Dom Feliciano Belt of southern Brazil and Uruguay represents part of a larger Neoproterozoic ... more The Dom Feliciano Belt of southern Brazil and Uruguay represents part of a larger Neoproterozoic orogenic system formed during the amalgamation of Western Gondwana. The hinterland and foreland domains in parts of the belt preserve deformation structures and metamorphic assemblages that developed during early crustal thickening from c. 650 Ma. However, the metamorphic history of the southern foreland, in Uruguay, and its relationship with the hinterland, is not so well understood. We show that metamorphism in the southern hinterland is characterized by near‐isothermal decompression from ~10 kbar (~770°C) down to ~6 kbar, reflecting exhumation from depths of ~40 km during convergent thrusting and crustal thickening. This metamorphic event and associated magmatism is constrained by garnet Lu–Hf and zircon U–Pb dating to c. 655–640 Ma, supporting age and P–T constraints from previous studies. In contrast, prograde metamorphism in the foreland supracrustal rocks reached maximum lower‐amp...
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Papers by Pedro Oyhantcabal