Metamorphic evolution of Raspas complex (Ecuador) and its relation with a J-K belt of melanges in NW of the South American plate.

2020 ◽  
Author(s):  
Mayda Arrieta-Prieto ◽  
Carlos Zuluaga-Castrillón ◽  
Oscar Castellanos-Alarcón ◽  
Carlos Ríos-Reyes
Keyword(s):  
High Pressure ◽  
Subduction Zones ◽  
Mineral Chemistry ◽  
White Mica ◽  
Petrographic Analysis ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Subduction Channel ◽  
Southern Ecuador

<p>High-pressure complexes along the Earth's surface provide evidence of the processes involved in both the crystallization of rocks in the subduction channel and its exhumation. Such processes are key to understand the dynamics and evolution of subduction zones and to try to reconstruct P-T trajectories for these complexes.</p><p>Previous studies on the Raspas complex (southern Ecuador) agree to state that it is composed of metamorphic rocks, mainly blueschists and eclogites, containing the mineral assemblage: glaucophane + garnet + epidote + omphacite + white mica + rutile ± quartz ± apatite ± pyrite ± calcite; which stabilized in metamorphic conditions of high pressure and low temperature. Additionally, the Raspas Complex has been genetically related to accretion and subduction processes of seamounts, which occurred in South America during the Late Jurassic - Early Cretaceous interval; and the exhumation of the complex was related to subduction channels. However, the evidence presented in the existing literature makes little emphasis on the reconstruction of thermobarometric models for the rocks of this complex.</p><p>By combining petrographic observations, whole-rock chemistry, and mineral chemistry in this work; it was possible to determine that pressure values of 10 ± 3 Kbar and temperature values of 630 ± 30 ° C, (obtained by simulations with THERMOCALC®) correspond to an event of retrograde metamorphism, suffered by the complex during its exhumation. This theory is complemented by the specific textures (that suggest this retrograde process) observed during petrographic analysis, such as amphibole replacing pyroxene, garnet chloritization, plagioclase crystallization and rutile replacement by titanite.</p><p>The results obtained, together with the thermobarometry data published for the Arquía complex in Colombia, allow us to establish a P-T trajectory, that may suggest a genetic relationship between these two complexes as a result of the tectonic processes associated with an active subduction margin that affected the NW margin of the South American plate at the end of the Jurassic.</p><p> </p>

scholarly journals Analysis of Colombian Seismicity as a Way to Explain and Understand The Bucaramanga Nest

2018 ◽  
Vol 3 (3) ◽  
pp. 134
Author(s):  
Wilmer Emilio García Moreno
Keyword(s):  
Subduction Zones ◽  
Focal Mechanisms ◽  
Fault System ◽  
Benioff Zone ◽  
South American ◽  
Lateral Extension ◽  
The South ◽  
Contour Map ◽  
South American Plate ◽  
High Seismicity

Colombia is region with high seismicity due to the convergence of Panama Block, Nazca and Caribbean plates with the South American Plate, however there is a complex area named The Bucaramanga Nest which was the motive of this research means of its complexity, being that there have been different studies which have not been able to explain the reason of this phenomenon, for that motive this work has as objective finding this answer by the use of 3679 earthquake information in Colombia, with a Mw higher than 3.5. Having information from all the earthquakes, they were localized on its epicenters to notice how they were distributed, after that, five lines were chosen to make, along them, The Benioff Zone, obtaining the geometry of the slabs for Nazca and Caribbean plates, knowing the angle of subduction of them and how it changed, also, thirty earthquakes near the five lines were selected to see the focal mechanisms along the slabs and knowing the fault system in The Bucaramanga Nest. Beside all it was said before, it was modeled an approximation of the subduction zones by a contour map along the studied region. At the end, it was able to reach an answer about the reason of why The Bucaramanga Nest happened, defining its vertical and lateral extension too.

scholarly journals The Origin of Back-Arc Spreading in The Eastern Edge of Scotia Plate

2016 ◽  
Vol 5 (1) ◽  
pp. 21
Author(s):  
Indra Budi Prasetyawan
Keyword(s):  
Subduction Zones ◽  
Sandwich Plate ◽  
Magnetic Anomalies ◽  
South American ◽  
The South ◽  
Origin And Evolution ◽  
Bathymetric Data ◽  
Scotia Ridge ◽  
Back Arc ◽  
Eastern Edge

The origin and evolution of  back-arc spreading in the eastern edge of Scotia Plate will be discussed in this paper. The Scotia Plate is a tectonicplate on the edge of the South Atlantic and Southern Ocean, located between the South American and Antartic plates. The East Scotia Ridge (ESR) in the eastern edge of Scotia Plate, forned due to subduction of the South American plate beneath the South Sandwich plate along the South Sandwich Island arc. The methods and techniques of data acquisition used were data from absolution motions and data from magnetic anomalies and bathymetric data. Magnetic anomalies and  bathymetric data that used in this paper consist of two sets data. First, magnetic anomalies and  bathymetric data which were obtained by aboard HMS Endurance in the 1969-70 austral summer, and the second, magnetic anomalies and  bathymetric data which were obtained after removal of the International Geomagnetic Reference Field (IGRF). Absolution motion analyses in the subduction zones of Sandwich plate results that form back-arc spreading in East Scotia Ridge showing high deformation for slow moving upper plates. Where back-arc spreading is associated with upper plate retreat that reaches 26.9 mm/year and have back-arc deformation style consistent with upper plate absolute. Key Words: Geological oceanography, Scotia plate, back-arc spreading

Geodynamic study of the north of the Andes block (Colombia, Panama, Ecuador and Venezuela) through gnss-gps: models of displacements, models of deformation and definition of local and regional geodynamic structures.

2020 ◽  
Author(s):  
Berrocoso Manuel ◽  
Del Valle Arroyo Pablo Emilio ◽  
Colorado Jaramillo David Julián ◽  
Gárate Jorge ◽  
Fernández-Ros Alberto ◽  
...  
Keyword(s):  
South America ◽  
Seismic Activity ◽  
Great Part ◽  
Velocity Model ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Northern Andes ◽  
Velocity Models ◽  
The North

<p>The northwest of South America is conformed by the territories of Ecuador, Colombia and Venezuela. Great part of these territories make up the Northern Andes Block (BAN). The tectonic and volcanic activity in the northwest of South America is directly related to the interaction of the South American plate, and the Nazca and Caribbean plates, with the Maracaibo and Panama-Chocó micro plates. The high seismic activity and the high magnitude of the recorded earthquakes make any study necessary to define this complex geodynamic region more precisely. This work presents the velocity models obtained through GNSS-GPS observations obtained in public continuous monitoring stations in the region. The observations of the Magna-eco network (Agustín Codazzi Geographic Institute) are integrated with models already obtained by other authors from the observations of the GEORED network (Colombian Geological Service). The observations have been processed using Bernese software v.52 using the PPP technique; obtaining topocentric time series. To obtain the speeds, a process of filtering and adjustment of the topocentric series has been carried out. Based on this velocity model, regional structures have been defined within the Northern Andes Block through a differentiation process based on the corresponding speeds of the South American, Nazca and Caribbean tectonic plates. Local geodynamic structures within the BAN itself have been established through cluster analysis based on both the direction and the magnitude of each of the vectors obtained. Finally, these structures have been correlated with the most significant geodynamic elements (fractures, faults, subduction processes, etc.) and with the associated seismic activity.</p>

scholarly journals Measuring the seismic risk along the Nazca-Southamerican subduction front: Shannon entropy and mutability

2019 ◽  
Author(s):  
Eugenio E. Vogel ◽  
Felipe G. Brevis ◽  
Denisse Pastén ◽  
Víctor Muñoz ◽  
Rodrigo A. Miranda ◽  
...  
Keyword(s):  
Shannon Entropy ◽  
Seismic Risk ◽  
Background Activity ◽  
Large Earthquake ◽  
South American ◽  
The South ◽  
Nazca Plate ◽  
South American Plate ◽  
Major Earthquake ◽  
Similarities And Differences

Abstract. Four geographical zones are defined along the trench that is formed due to the subduction of the Nazca Plate underneath the South American plate; they are denoted A, B, C and D from North to South; zones A, B and D have had a major earthquake after 2010 (8.0), while zone C has not, thus offering a contrast for comparison. For each zone a sequence of intervals between consecutive seisms with magnitudes ≥ 3.0 is formed and then characterized by Shannon entropy and mutability. These methods show correlation after a major earthquake in what is known as the aftershock regime but they show independence otherwise. Exponential adjustments for these parameters reveal that mutability offers a wider range for the parameters characterizing the recovery to the values of the parameters defining the background activity for each zone before a large earthquake. It is found that the background activity is particularly high for zone A, still recovering for Zone B, reaching values similar to those of Zone A in the case of Zone C (without recent major earthquake) and oscillating around moderate values for Zone D. It is discussed how this can be an indication for more risk of an important future seism in the cases of Zones A and C. The similarities and differences between Shannon entropy and mutability are discussed and explained.

scholarly journals Flat subduction dynamics and deformation of the South American plate: Insights from analog modeling

Tectonics ◽  
2008 ◽  
Vol 27 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Nicolas Espurt ◽  
Francesca Funiciello ◽  
Joseph Martinod ◽  
Benjamin Guillaume ◽  
Vincent Regard ◽  
...  
Keyword(s):  
South American ◽  
The South ◽  
South American Plate ◽  
Analog Modeling
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