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Probing lithosphere processes through geochemical and geochronological studies - Permian / Triassic intracontinental rifting and Jurassic subduction-related magmatism in Southern Peru

English title Probing lithosphere processes through geochemical and geochronological studies - Permian / Triassic intracontinental rifting and Jurassic subduction-related magmatism in Southern Peru
Applicant Schaltegger Urs
Number 124332
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 Geochronology
Start/End 01.04.2009 - 31.03.2012
Approved amount 410'213.00
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Keywords (19)

zircon; U-Pb geochronology; Permian; Triassic; Andes; Peru; magmatism; geochemistry; U-Pb dating; Ar-Ar dating; subduction; Jurassic; intracontinental rifting; geochronology; South America; volcanic arc; extension; back-arc; U-Pb

Lay Summary (English)

Lead
Lay summary
This proposal seeks funding to continue research on the pre-Andean evolution of the South American active margin in Peru using geochemical and geochronological tools. We have gained new ideas about the evolution of the Peruvian segment of the Andean margin, from the first traces of orogenic magmatism in the mid-Proterozoic, to Jurassic peralkaline magmatism at the onset of modern Andean orogenic dynamics. Detrital zircons in metasedimentary sequences as well as the magmatic record of the Eastern Cordillera testify the existence of different mobile belts along the proto-Andean margin: Grenvilian/Sunsás (1.3-0.8 Ga), pre-Braziliano (0.77-0.66 Ga), Braziliano-Panafrican (0.65-0.55 Ga) and Famatinian/Pampean (0.65-0.45 Ma), and the Gondwanide orogenies (0.35-0.20 Ga). Initial Hf isotopic compositions of dated zircons allow quantification of crustal growth over time during different geotectonic settings: the results indicate that during continental arc stages reworking of the pre-existing crust is the main process, and only during the post-tectonic, extensional stages (Neo-Proterozoic, Permo-Triassic, Late Triassic, Early Jurassic) subordinate volumes of juvenile melts were accreted at the base of the crust. The latter were enough to compensate for the periods of crustal reworking, but not important enough to produce significant crustal growth along the proto-Andean margin.With this proposal we intend to focus on two well-defined topics of general interest:Subproject A The birth and death of an intracontinental rift: the Mitu Group in southern Peru: The southern part of the Eastern Cordillera is characterized by the development of a large Triassic to early Jurassic intracontinental rift. With a PhD project, we plan to study the timing and rates of crustal thinning, basin subsidence and magma emplacement. Rifting terminated in the early Jurassic after emplacement of an anorogenic peralkaline volcanic and plutonic suite, offering insight into the contribution of crustal vs. mantle sources over time in an evolving and eventually aborted continental rift.Subproject B The Jurassic magmatic arc in southwestern Peru: The Triassic-Jurassic transition is characterized by the abortion of the Mitu rift and renewed subduction-related magmatism in a magmatic arc along the present-day coastline. We intend to study, with a PhD project, the transition from the extensional geodynamic scenario forming the Mitu Rift to renewed subduction and subsequent magma production, in terms of timing and sources of magmatic liquids. Understanding the timing and nature of Jurassic arc magmatism will also explain the lack of Jurassic rocks north of Lima.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Characterisation of Triassic rifting in Peru and implications for the early Disassembly of western Pangaea
Spikings Richard, Reitsma M.J., Boekhout F., Miskovic A., Ulianov A., Chiaradia M., Gerdes A., Schaltegger U. (2016), Characterisation of Triassic rifting in Peru and implications for the early Disassembly of western Pangaea, in Gondwana Research, 35, 124-143.
Mesozoic arc magmatism along the southern Peruvian margin during Gondwana breakup and dispersal
Boekhout F, Spikings R, Sempere T, Chiaradia M, Ulianov A, Schaltegger U (2012), Mesozoic arc magmatism along the southern Peruvian margin during Gondwana breakup and dispersal, in LITHOS, 146, 48-64.
Crustal growth along a non-collisional cratonic margin: A Lu-Hf isotopic survey of the Eastern Cordilleran granitoids of Peru
Miskovic A, Schaltegger U (2009), Crustal growth along a non-collisional cratonic margin: A Lu-Hf isotopic survey of the Eastern Cordilleran granitoids of Peru, in EARTH AND PLANETARY SCIENCE LETTERS, 279(3-4), 303-315.
Tectonomagmatic evolution of Western Amazonia: Geochemical characterization and zircon U-Pb geochronologic constraints from the Peruvian Eastern Cordilleran granitoids
Miskovic A, Spikings RA, Chew DM, Kosler J, Ulianov A, Schaltegger U (2009), Tectonomagmatic evolution of Western Amazonia: Geochemical characterization and zircon U-Pb geochronologic constraints from the Peruvian Eastern Cordilleran granitoids, in GEOLOGICAL SOCIETY OF AMERICA BULLETIN, 121(9-10), 1298-1324.

Collaboration

Group / person Country
Types of collaboration
Université de Lausanne Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Université Paul Sabatier Toulouse France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
INGEMMET, Lima Peru (South America)
- in-depth/constructive exchanges on approaches, methods or results
J W Goethe Universität Frankfurt Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Swiss Geoscience Meeting Talk given at a conference A late Paleozoic back-arc basin on the western Gondwana margin: age and geodynamic setting of Permo-Carboniferous sedimentary rocks of South-East Peru 11.11.2011 Zürich, Switzerland Schaltegger Urs; Spikings Richard A.;
Goldschmidt Conference Talk given at a conference Tracing the late Paleozoic to early Mesozoic crustal evolution of coastal Southern Peru 14.08.2011 Prague, Czech Republic, Czech Republic Boekhout Flora; Spikings Richard A.; Schaltegger Urs;
EGU General Assembly Talk given at a conference New geochronological constraints on the Late Paleozoic to Jurassic of coastal southern Peru 03.04.2011 Vienna, Austria, Austria Schaltegger Urs; Spikings Richard A.; Boekhout Flora;
15th Congreso Peruano de Geologia Talk given at a conference Constraining the age of the Mitu Group, south-east Peru: U-Pb ages of detrital and igneous zircons 27.09.2010 Cusco, Peru, Peru Spikings Richard A.; Schaltegger Urs; Reitsma Martje Jel;
EGU General Assembly Talk given at a conference Constraining the age of the Mitu Group, South-East Peru – U-Pb ages of detrital and igneous zircons 02.05.2010 Vienna, Austria, Austria Reitsma Martje Jel; Spikings Richard A.; Schaltegger Urs;
Swiss Geoscience Meeting Talk given at a conference The temporal evolution of the Mitu group, south-easr Peru – first U-Pb data 20.11.2009 Neuchâtel, Switzerland Reitsma Martje Jel; Schaltegger Urs; Spikings Richard A.;


Associated projects

Number Title Start Funding scheme
116572 Probing lithosphere processes thtough geochemical and geochronological studies - Permian / Triassic intracontinental rifting and Jurassic subduction-related magmatisme in Southern Peru 01.04.2007 Project funding
128146 Upgrading the 40Ar/39Ar facility at the University of Geneva 01.01.2010 R'EQUIP

Abstract

This proposal seeks funding to continue research on the pre-Andean evolution of the South American active margin in Peru using geochemical and geochronological tools. During the five previous years of this research project, we have gained new ideas about the evolution of the Peruvian segment of the Andean margin, from the first traces of orogenic magmatism in the mid-Proterozoic, to Jurassic peralkaline magmatism at the onset of modern Andean orogenic dynamics. Detrital zircons in metasedimentary sequences as well as the magmatic record of the Eastern Cordillera testify the existence of different mobile belts along the proto-Andean margin: Grenvilian/Sunsás (1.3-0.8 Ga), pre-Braziliano (0.77-0.66 Ga), Braziliano-Panafrican (0.65-0.55 Ga) and Famatinian/Pampean (0.65-0.45 Ma), and the Gondwanide orogenies (0.35-0.20 Ga). The latter gave rise to a 800 km long magmatic belt in the Eastern Cordillera, with a compositional evolution from Pennsylvanian arc-related intrusions, followed by Permo-Triassic post-collisional, extension-related granites and late Triassic S-type, rift-related granites in the southernmost Cordillera de Carabaya. Initial Hf isotopic compositions of dated zircons allow quantification of crustal growth over time during different geotectonic settings: the results indicate that during continental arc stages reworking of the pre-existing crust is the main process, and only during the post-tectonic, extensional stages (Neo-Proterozoic, Permo-Triassic, Late Triassic, Early Jurassic) subordinate volumes of juvenile melts were accreted at the base of the crust. The latter were enough to compensate for the periods of crustal reworking, but not important enough to produce significant crustal growth along the proto-Andean margin. Our conclusion is that the proto-Andean margin stayed during more than 1 billion years in a supra-subduction position at the leading edge of Western Gondwana. Neither supra-subduction magmatism nor vertical accretion of residual mantle melts at the base of the crust, but only lateral accretion of juvenile terranes (arcs, plateaus or juvenile crust) are proposed to be suitable processes to lead to significant crustal growth.The successful approach using isotopic tracing and dating motivates us to continue research on the pre-Andean evolution of the South American margin. With this proposal we intend to focus on two well-defined topics of general interest:Subproject A The birth and death of an intracontinental rift: the Mitu Group in southern Peru: The southern part of the Eastern Cordillera is characterized by the development of a large Triassic to early Jurassic intracontinental rift (Mitu Group). With a PhD project, we plan to study the timing and rates of crustal thinning, basin subsidence and magma emplacement. We hope to provide answers to the questions of when and how transtension and finally rifting replaced Carboniferous orthogonal subduction and magmatism, was the crustal thinning caused by a highly oblique direction of the subducting plate or by the response of the South American continent to Pangea breakup. Rifting terminated in the early Jurassic after emplacement of an anorogenic peralkaline volcanic and plutonic suite, offering insight into the contribution of crustal vs. mantle sources over time in an evolving and eventually aborted continental rift.Subproject B The Jurassic magmatic arc in southwestern Peru: The Triassic-Jurassic transition is characterized by the abortion of the Mitu rift and renewed subduction-related magmatism in a magmatic arc along the present-day coastline, and in the interior of the Arequipa massif south of 12°S. Numerous continuous sections indicate that an early bimodal volcanic suite may be transitional from extensional/transtensional tectonics and that calc-alkaline arc magmatism resumes in the middle Jurassic. We intend to study, with a PhD project, the transition from the extensional geodynamic scenario forming the Mitu Rift to renewed (orthogonal) subduction and subsequent magma production, in terms of timing and sources of magmatic liquids. Understanding the timing and nature of Jurassic arc magmatism will also explain the lack of Jurassic rocks in the enigmatic “craton-free zone”, north of 12°S (north of Lima).To carry out the proposed research, we are requesting 30 months of salary to complete the PhD project of M. Reitsma (project A), and 27 months for the PhD project of F. Boekhout (project B).
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