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U-Pb geochronologic evidence for the evolution of the Gondwanan margin of the north-central Andes

U-Pb geochronologic evidence for the evolution of the Gondwanan margin of the north-central Andes
U-Pb geochronologic evidence for the evolution of the Gondwanan margin of the north-central Andes
We investigated the Neoproterozoic–early Paleozoic evolution of the Gondwanan margin of the north-central Andes by employing U-Pb zircon geochronology in the Eastern Cordilleras of Peru and Ecuador using a combination of laser-ablation–inductively coupled plasma–mass spectrometry detrital zircon analysis and dating of syn- and post-tectonic intrusive rocks by thermal ionization mass spectrometry and ion microprobe. The majority of detrital zircon samples exhibits prominent peaks in the ranges 0.45–0.65 Ga and 0.9–1.3 Ga, with minimal older detritus from the Amazonian craton. These data imply that the Famatinian-Pampean and Grenville (= Sunsas) orogenies were available to supply detritus to the Paleozoic sequences of the north-central Andes, and these orogenic belts are interpreted to be either buried underneath the present-day Andean chain or adjacent foreland sediments. There is evidence of a subduction-related magmatic belt (474–442 Ma) in the Eastern Cordillera of Peru and regional orogenic events that pre- and postdate this phase of magmatism. These are confirmed by ion-microprobe dating of zircon overgrowths from amphibolite-facies schists, which reveals metamorphic events at ca. 478 and ca. 312 Ma and refutes the previously assumed Neoproterozoic age for orogeny in the Peruvian Eastern Cordillera. The presence of an Ordovician magmatic and metamorphic belt in the north-central Andes demonstrates that Famatinian metamorphism and subduction-related magmatism were continuous from Patagonia through northern Argentina to Venezuela. The evolution of this extremely long Ordovician active margin on western Gondwana is very similar to the Taconic orogenic cycle of the eastern margin of Laurentia, and our findings support models that show these two active margins facing each other during the Ordovician.
Gondwana, Andes, Peru, geochronology, zircon, Paleozoic
0016-7606
697-711
Chew, D.M.
aa7ab8e2-9db6-4da7-8bb6-8cb6c1d68521
Schaltegger, U.
41d5729c-d18e-43cc-a95f-dbe841b43461
Kosler, J.
dd424612-ec13-48cd-a88a-41ce1155c969
Whitehouse, M.J.
97a11c20-e57f-46ad-a865-9771aa5a4081
Gutjahr, M.
822f4505-967f-4b6c-8aa3-628888362c01
Spikings, R.A.
ea4e6d4c-cb56-45a9-b771-c3ee4e2d1dfd
Miskovic, A.
f0993b5e-67bf-4196-9e33-d4d90c2eb425
Chew, D.M.
aa7ab8e2-9db6-4da7-8bb6-8cb6c1d68521
Schaltegger, U.
41d5729c-d18e-43cc-a95f-dbe841b43461
Kosler, J.
dd424612-ec13-48cd-a88a-41ce1155c969
Whitehouse, M.J.
97a11c20-e57f-46ad-a865-9771aa5a4081
Gutjahr, M.
822f4505-967f-4b6c-8aa3-628888362c01
Spikings, R.A.
ea4e6d4c-cb56-45a9-b771-c3ee4e2d1dfd
Miskovic, A.
f0993b5e-67bf-4196-9e33-d4d90c2eb425

Chew, D.M., Schaltegger, U., Kosler, J., Whitehouse, M.J., Gutjahr, M., Spikings, R.A. and Miskovic, A. (2007) U-Pb geochronologic evidence for the evolution of the Gondwanan margin of the north-central Andes. Geological Society of America Bulletin, 119 (5-6), 697-711. (doi:10.1130/B26080.1).

Record type: Article

Abstract

We investigated the Neoproterozoic–early Paleozoic evolution of the Gondwanan margin of the north-central Andes by employing U-Pb zircon geochronology in the Eastern Cordilleras of Peru and Ecuador using a combination of laser-ablation–inductively coupled plasma–mass spectrometry detrital zircon analysis and dating of syn- and post-tectonic intrusive rocks by thermal ionization mass spectrometry and ion microprobe. The majority of detrital zircon samples exhibits prominent peaks in the ranges 0.45–0.65 Ga and 0.9–1.3 Ga, with minimal older detritus from the Amazonian craton. These data imply that the Famatinian-Pampean and Grenville (= Sunsas) orogenies were available to supply detritus to the Paleozoic sequences of the north-central Andes, and these orogenic belts are interpreted to be either buried underneath the present-day Andean chain or adjacent foreland sediments. There is evidence of a subduction-related magmatic belt (474–442 Ma) in the Eastern Cordillera of Peru and regional orogenic events that pre- and postdate this phase of magmatism. These are confirmed by ion-microprobe dating of zircon overgrowths from amphibolite-facies schists, which reveals metamorphic events at ca. 478 and ca. 312 Ma and refutes the previously assumed Neoproterozoic age for orogeny in the Peruvian Eastern Cordillera. The presence of an Ordovician magmatic and metamorphic belt in the north-central Andes demonstrates that Famatinian metamorphism and subduction-related magmatism were continuous from Patagonia through northern Argentina to Venezuela. The evolution of this extremely long Ordovician active margin on western Gondwana is very similar to the Taconic orogenic cycle of the eastern margin of Laurentia, and our findings support models that show these two active margins facing each other during the Ordovician.

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More information

Published date: May 2007
Additional Information: Times Cited: 38
Keywords: Gondwana, Andes, Peru, geochronology, zircon, Paleozoic

Identifiers

Local EPrints ID: 191625
URI: https://eprints.soton.ac.uk/id/eprint/191625
ISSN: 0016-7606
PURE UUID: 1cc66e79-c64e-42a8-bd19-aed32edd5a0c

Catalogue record

Date deposited: 23 Jun 2011 08:36
Last modified: 16 Jul 2019 23:27

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