Mafic and ultramafic crustal fragments of the southwestern Precordillera terrane and their bearing on tectonic models of the early Paleozoic in western Argentina

J. Steven Davis; Sarah M Roeske; William C McClelland; Suzanne M Kay

doi:10.1130/0091-7613(2000)28<171:MAUCFO>2.0.CO;2

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Mafic and ultramafic crustal fragments of the southwestern Precordillera terrane and their bearing on tectonic models of the early Paleozoic in western Argentina

Journal article

Peer reviewed

Mafic and ultramafic crustal fragments of the southwestern Precordillera terrane and their bearing on tectonic models of the early Paleozoic in western Argentina

J. Steven Davis, Sarah M Roeske, William C McClelland and Suzanne M Kay

Geology (Boulder), Vol.28(2), pp.171-174

02/2000

DOI: 10.1130/0091-7613(2000)28<171:MAUCFO>2.0.CO;2

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Abstract

New U-Pb zircon ages and initial Nd isotope data from mafic and ultramafic rocks that have been tectonically imbricated on the southwest margin of the Precordillera terrane, western Argentina, indicate that these rocks do not constitute a single ophiolite pseudostratigraphy as previously thought. Rock units include Late Proterozoic (576+ or -17 Ma) microgabbro and Silurian (418+ or -10 Ma) sills, both of which have initial Nd isotope values of +6.0 to +7.3 and identical trace element geochemistry indicating formation in extensional settings. Late Ordovician (450+ or -20 Ma) layered gabbro has a distinct initial Nd isotope value of +0.6. It intrudes quartzofeldspathic gneiss and tectonized ultramafic rocks; this assemblage represents the deep part of a continental margin volcanic arc that formed on the eastern margin of Chilenia, as the ocean basin west of the Precordillera terrane began to close in the Middle Ordovician. The new tectonic interpretations generally support existing hypotheses that the Precordillera terrane rifted and drifted from southeastern Laurentia in the Cambrian to Early Ordovician and that the western margin of the Precordillera terrane represents a suture between two fragments of continental crust.

absolute age

Argentina

Bonilla Argentina

Cambrian

Chilenia

continental crust

continental drift

continental margin

Cortaderas Argentina

crust

dates

fragments

gabbros

geochemistry

IGCP

Igneous and metamorphic petrology

igneous rocks

imbricate tectonics

intrusions

isotopes

Laurentia

lower Paleozoic

mafic composition

metals

microgabbro

neodymium

nesosilicates

ophiolite

Ordovician

orthosilicates

outcrops

Paleozoic

plate tectonics

plutonic rocks

Portillo Argentina

Pozos Argentina

Precordillera

rare earths

rifting

silicates

sills

Silurian

Solid-earth geophysics

South America

suture zones

tectonics

terranes

U/Pb

ultramafic composition

western Argentina

zircon

zircon group

Details

Title: Subtitle: Mafic and ultramafic crustal fragments of the southwestern Precordillera terrane and their bearing on tectonic models of the early Paleozoic in western Argentina
Creators: J. Steven Davis - University of California, Davis
Sarah M Roeske - University of California, Davis
William C McClelland - University of Idaho
Suzanne M Kay - Cornell University
Resource Type: Journal article
Publication Details: Geology (Boulder), Vol.28(2), pp.171-174
Publisher: Geological Society of America (GSA)
DOI: 10.1130/0091-7613(2000)28<171:MAUCFO>2.0.CO;2
ISSN: 0091-7613
eISSN: 1943-2682
Language: English
Date published: 02/2000
Academic Unit: Earth and Environmental Sciences
Record Identifier: 9984229305402771

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