Publications by authors named "Jean-Louis Paquette"

3 Publications

  • Page 1 of 1

The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting.

Sci Rep 2020 05 4;10(1):7486. Epub 2020 May 4.

Anton de Kom University of Suriname, Paramaribo, SA, Suriname.

We report the discovery of 173.4 Ma hotspot-related magmatic rocks in the basement of the Demerara Plateau, offshore French Guiana and Suriname. According to plate reconstructions, a single hotspot may be responsible for the magmatic formation of (1) both the Demerara Plateau (between 180 and 170 Ma) and the Guinea Plateau (circa 165 Ma) during the end of the Jurassic rifting of the Central Atlantic; (2) both Sierra Leone and Ceara Rises (mainly from 76 to 68 Ma) during the upper Cretaceous oceanic spreading of the Equatorial Atlantic ocean; (3) the Bathymetrists seamount chain since the upper Cretaceous. The present-day location of the inferred Sierra Leone hotspot should be 100 km west of the Knipovich Seamount.
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http://dx.doi.org/10.1038/s41598-020-64333-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7198611PMC
May 2020

The earliest evidence for modern-style plate tectonics recorded by HP-LT metamorphism in the Paleoproterozoic of the Democratic Republic of the Congo.

Sci Rep 2018 Oct 18;8(1):15452. Epub 2018 Oct 18.

Early Life Traces & Evolution-Astrobiology, Department of Geology, B18, University of Liège, 4000, Liège, Belgium.

Knowing which geodynamic regimes characterised the early Earth is a fundamental question. This implies to determine when and how modern plate tectonics began. Today, the tectonic regime is dominated by mobile-lid tectonics including deep and cold subduction. However, in the early Earth (4.5 to 2 Ga) stagnant-lid tectonics may also have occurred. The study of high pressure-low temperature (HP-LT) metamorphic rocks is important, because these rocks are only produced in present-day subduction settings. Here, we characterize the oldest known HP-LT eclogite worldwide (2089 ± 13 Ma; 17-23 kbar/500-550 °C), discovered in the Democratic Republic of the Congo. We provide evidence that the mafic protolith of the eclogite formed at 2216 ± 26 Ma in a rift-type basin, and was then subducted to mantle depths (>55 km) before being exhumed during a complete Wilson cycle lasting ca. 130 Ma. Our results indicate the operation of modern mobile-lid plate tectonics at 2.2-2.1 Ga.
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http://dx.doi.org/10.1038/s41598-018-33823-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6193989PMC
October 2018

The elusive Hadean enriched reservoir revealed by 142Nd deficits in Isua Archaean rocks.

Nature 2012 Nov;491(7422):96-100

Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, CNRS UMR 6524, IRD R 163, BP 10448, 63000 Clermont-Ferrand, France.

The first indisputable evidence for very early differentiation of the silicate Earth came from the extinct (146)Sm-(142)Nd chronometer. (142)Nd excesses measured in 3.7-billion-year (Gyr)-old rocks from Isua (southwest Greenland) relative to modern terrestrial samples imply their derivation from a depleted mantle formed in the Hadean eon (about 4,570-4,000 Gyr ago). As dictated by mass balance, the differentiation event responsible for the formation of the Isua early-depleted reservoir must also have formed a complementary enriched component. However, considerable efforts to find early-enriched mantle components in Isua have so far been unsuccessful. Here we show that the signature of the Hadean enriched reservoir, complementary to the depleted reservoir in Isua, is recorded in 3.4-Gyr-old mafic dykes intruding into the Early Archaean rocks. Five out of seven dykes carry (142)Nd deficits compared to the terrestrial Nd standard, with three samples yielding resolvable deficits down to -10.6 parts per million. The enriched component that we report here could have been a mantle reservoir that differentiated owing to the crystallization of a magma ocean, or could represent a mafic proto-crust that separated from the mantle more than 4.47 Gyr ago. Our results testify to the existence of an enriched component in the Hadean, and may suggest that the southwest Greenland mantle preserved early-formed heterogeneities until at least 3.4 Gyr ago.
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http://dx.doi.org/10.1038/nature11565DOI Listing
November 2012