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Accretionary and post-accretionary cooling, exhumation and tectonic history of the central and western Andes of Colombia

English title Accretionary and post-accretionary cooling, exhumation and tectonic history of the central and western Andes of Colombia
Applicant Spikings Richard A.
Number 107596
Funding scheme Project funding
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geochemistry
Start/End 01.04.2005 - 31.03.2008
Approved amount 175'550.00
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Keywords (9)

Northern Andes; terrane accretion; thermochronology; geochronology; geochemistry; Caribbean Plateau; exhumation; accretion; Nortern Andes

Lay Summary (English)

Lead
Lay summary
The cordilleras of the Northern Andean Segment (NAS) are a juxtaposition of ocean island arcs, an oceanic plateau and rocks of the paleo-continental margin. This project aims to determine the pre-, syn- and post-accretionary history of individual terranes in Colombia, with an emphasis on determining the timing and duration of accretionary events, and quantifying cooling and exhumation rates prior to and during periods of Andean orogenesis.
A major, N-S trending, regional scale, topographic depression (Interandean Valley) exists along a suture between oceanic and continental provinces throughout the NAS, although the nature of its basement is unknown. Published hypotheses propose that the valley is composed of microplates and can be considered as a separate terrane(s), (Toussaint & Restrepo, 1994). However, we suggest that this interpretation is incorrect because it is based on inaccurate radiometric data and limited geochemical analyses. Spikings et al. (2005) proposed that the valley is floored by a regional scale, tectonised zone defined by a mélange, which has captured rocks from both the continental and oceanic provinces.
The project applicants, and a single PhD student have completed a sampling survey along several traverses across the Central and Western cordilleras and the Interandean Valley in Colombia. A thermochronological (40Ar/39Ar, fission-track and (U-Th)/He)) study of various mineral phases extracted from crystalline rocks is being combined with petrological studies to constrain the thermal, faulting and exhumation history of fault blocks within the cordilleras. This work is being combined with geochemical and geochronological analyses of crystalline rocks that are exposed within the Interandean Valley in Colombia and Ecuador to assess their origin, timing of crystallisation, and cooling and exhumation histories.
The acquired data and interpretations are being used to develop hypotheses for the accretionary and post-accretionary history of oceanic terranes, the ocean-continent suture and the Central Cordillera of Colombia. These hypotheses will be compared with published models of the geological history of the Ecuadorian Andes and their interaction with the Caribbean Plate. The hypotheses will be tested against the kinematics of the present day and relic subducting and approaching oceanic plate to check if significant upper-plate tectonic episodes such as sudden increases in exhumation rate, correspond to tectonic rearrangements or subducted heterogeneities in the Nazca and Farallon plates. The final aim is to propose a coherent geological model for the NAS and to further assess the influence of the Caribbean Plate on this region.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

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Associated projects

Number Title Start Funding scheme
134443 Thermochronology and Tectonics of the Northern Andes (Colombia and Ecuador) 01.04.2011 Project funding
117359 Acquisition of a Fission Track Analytical Facility 01.07.2007 R'EQUIP
128146 Upgrading the 40Ar/39Ar facility at the University of Geneva 01.01.2010 R'EQUIP
119871 Thermochronology and tectonics of the Northern Andes (Colombia and Ecuador) 01.04.2008 Project funding

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