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The occurrence and timing of high-pressure metamorphism on Margarita Island, Venezuela: A constraint on Caribbean–South America interaction

By
Walter V. Maresch
Walter V. Maresch
1
Institute of Geology, Mineralogy & Geophysics
,
Ruhr-University Bochum, 44780 Bochum
,
Germany
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Rolf Kluge
Rolf Kluge
2
Institute of Mineralogy, Münster University
,
Corrensstrasse 24, 48149 Münster
,
Germany
3
Present address:
AQUANTA Hydrogeologie GmbH & Co. KG, Kirchplatz 1, 48301 Nottuln
,
Germany
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Albrecht Baumann
Albrecht Baumann
2
Institute of Mineralogy, Münster University
,
Corrensstrasse 24, 48149 Münster
,
Germany
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James L. Pindell
James L. Pindell
4
Tectonic Analysis Ltd.
Chestnut House, Duncton, Sussex GU28 0LH
,
UK
5
Department of Earth Science
,
Rice University
,
Houston, TX 77002
,
USA
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Gabriela Krückhans-Lueder
Gabriela Krückhans-Lueder
2
Institute of Mineralogy, Münster University
,
Corrensstrasse 24, 48149 Münster
,
Germany
6
Present address:
Tornescher Weg 150, 25436 Uetersen
,
Germany
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Klaus Stanek
Klaus Stanek
7
Institute of Geology
,
TU Bergakademie Freiberg, 09596 Freiberg
,
Germany
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Published:
January 01, 2009

Abstract

The metamorphic rock sequences exposed on the Island of Margarita, Venezuela, located in the southeastern corner of the Caribbean Plate margin, are composed of a high-pressure/low-temperature (HP/LT) nucleus subducted to at least 50 km depth, now structurally overlain by lower-grade greenschist-facies units lacking any sign of high-pressure subduction-zone metamorphism. The HP/LT nucleus involves protoliths of both oceanic (metabasalts and intimately associated carbonaceous schists of the La Rinconada unit; peridotite massifs) and continental affinity (metapelites, marbles and gneisses of the Juan Griego unit). All HP/LT units were joined together prior to the peak of high-pressure metamorphism, as shown by their matching metamorphic pressure–temperature evolution. The metamorphic grade attained produced barroisite as the regional amphibole. Glaucophane is not known from Margarita. Contrary to a widely propagated assumption, there are no major nappe structures post-dating HP/LT metamorphism anywhere within the high-pressure nucleus of Margarita Island. U–Pb zircon dating of key tonalitic to granitic intrusive rocks provides the following constraints: (1) the Juan Griego unit is heterogeneous and contains Palaeozoic as well as probable Mesozoic protolith; (2) the peak of HP/LT metamorphism, that is maximum subduction, is younger than 116–106 Ma and older than 85 Ma, most probably c. 100–90 Ma, a time span during which the southeastern Caribbean/South American border was clearly a passive margin. The assembly of Margaritan protoliths and their HP/LT overprint occurred far to the west in northwestern South America, a scenario completely in accord with the details of the Pacific-origin model outlined by Pindell & Kennan. Juxtaposition of the greenschist-facies units occurred after exhumation into mid-crustal levels after c. 80 Ma.

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Contents

Geological Society, London, Special Publications

The Origin and Evolution of the Caribbean Plate

K. H. James
K. H. James
Aberystwyth University, Wales, UK
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M. A. Lorente
M. A. Lorente
Central University of Venezuela, Venezuela
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J. L. Pindell
J. L. Pindell
Tectonic Analysis Ltd, West Sussex, UK
Rice University, Texas, USA
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Geological Society of London
Volume
328
ISBN electronic:
9781862395763
Publication date:
January 01, 2009

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