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1. Mineral systems prospectivity modelling for gold and nickel in the Halls Creek Orogen, Western Australia

Author

Fariba Kohanpour, Mark Lindsay, Fred Jourdan, Weronika Gorczyk, Marc Poujol, Sandra Occhipinti, The University of Western Australia (UWA), Curtin University [Perth], Planning and Transport Research Centre (PATREC), Géosciences Rennes (GR), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), MRIWA Project, Australian Research Council, DARE ARC ITTC, Geological Survey of Western Australia, Panoramic Resource Ltd, Australian Government Department of Industry, Innovation and ScienceCooperative Research Centres (CRC) Programme, Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)

Subjects
geography, geography.geographical_feature_category, Lithology, 020209 energy, Geochemistry, Geology, Orogeny, 02 engineering and technology, Structural basin, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Craton, Prospectivity mapping, Geochemistry and Petrology, 0202 electrical engineering, electronic engineering, information engineering, Economic Geology, Shear zone, 0105 earth and related environmental sciences, Terrane, [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
Abstract

International audience; Geodynamic models, geological-geophysical interpretations, and isotope analysis illustrate that there are links between the nickel and gold mineral systems in the Halls Creek Orogen, Western Australia. Whole-rock Nd and 40Ar/39Ar analysis of rocks throughout the region, when compared with the geodynamic models suggest that nickel and gold mineralization in the Halls Creek Orogen can be related to basin development and subsequent basin closure during the convergence of North Australian Craton and Kimberley Craton, respectively. Whole-rock Nd analysis confirmed the input of juvenile melts in the centre of the orogen before the 1835–1805 Ma Halls Creek Orogeny, supporting the upwelling of decompression mantle melts during the basin development. These analyses also revealed the spatial links between nickel and gold mineralization and lithological units with positive εNd values. Spatially the link between these mineral systems appears to be related to the presence of deep-seated shear zones that formed early in the history of the orogen and were later reactivated. The results of geodynamic models, geophysical interpretation, and isotopic analysis are used to understand the critical processes in the gold and nickel mineralization, which are presented by predictor maps. The GIS-based knowledge-driven fuzzy logic method used to integrate the predictor maps and create the prospectivity maps. Herein we show that mafic-ultramafic units prospective for nickel mineralization formed by upwelling of decompression mantle melt during crustal thinning and extension during basin development, and typically consist of the most juvenile magmas in the region. Whereas, gold deposits formed during the compressional regime and basin closure, and are located along a major shear zone separating two terranes. This deep crustal-scale shear zone is implied to be the site of multiple stages of deformation that acted as fluid migration pathways during basin closure and subsequent collision. Another critical element that appears to be related to gold prospectivity is the presence of lithologies with a juvenile signature. In contrast to nickel analyses which are closely related to mafic-ultramafic units, the source component seems less influential when attempting to target orogenic gold deposits.

Published
2020
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2. The Central Atlantic Magmatic Province (CAMP) in Morocco

Author

Fida Medina, Alberto Zanetti, Mohamed Khalil Bensalah, Andrea Marzoli, Hervé Bertrand, Laurie Reisberg, Massimo Chiaradia, Hind El Hachimi, Sarah I Brownlee, Christian Tegner, Tiberio Cuppone, Renaud E. Merle, Nasrrddine Youbi, Fred Jourdan, Sara Callegaro, Joshua Davies, Paul R. Renne, Abdelkader Mahmoudi, Giuliano Bellieni, Stefano Crivellari, Christine Meyzen, Dipartimento di Geoscienze [Padova], Universita degli Studi di Padova, Laboratoire de Sciences de la Terre (LST), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Université Cadi Ayyad [Marrakech] (UCA), Laboratoire de Mécanique et Technologie (LMT), École normale supérieure - Cachan (ENS Cachan)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Section des Sciences de la Terre, Université de Genève (UNIGE), Western Australian Argon Isotope Facility, Department of Applied Geology & JdL-CMS, Curtin University [Perth], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC), Istituto di Geoscienze e Georisorse, Pavia, Centro de Geologia [Lisboa], Universidade de Lisboa (ULISBOA), Università degli Studi di Padova = University of Padua (Unipd), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Instituto Dom Luiz, Universidade de Lisboa = University of Lisbon (ULISBOA), Centre for Earth Evolution and Dynamics [Oslo] (CEED), Department of Geosciences [Oslo], Faculty of Mathematics and Natural Sciences [Oslo], University of Oslo (UiO)-University of Oslo (UiO)-Faculty of Mathematics and Natural Sciences [Oslo], University of Oslo (UiO)-University of Oslo (UiO), Swedish Museum of Natural History (NRM), Department of Earth Sciences [Geneva], Université de Genève = University of Geneva (UNIGE), Wayne State University [Detroit], Department of Applied Geology [Perth], CNR Istituto di Geoscienze e Georisorse [Pavia] (IGG), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), deceased, Université Moulay Ismail (UMI), Berkeley Geochronology Center (BGC), Department of Earth and Planetary Sciences [Univ California Davis] (EPS - UC Davis), University of California [Davis] (UC Davis), University of California (UC)-University of California (UC), Instituto de Geociências [São Paulo], Universidade de São Paulo = University of São Paulo (USP), Université Chouaib Doukkali (UCD), and Aarhus University [Aarhus]

Subjects
010504 meteorology & atmospheric sciences, EASTERN NORTH-AMERICA, ANTI-ATLAS, Lava, RE-OS, Large igneous province, Geochemistry, geochronology, 010502 geochemistry & geophysics, 01 natural sciences, WEST-AFRICAN CRATON, TRIASSIC-JURASSIC BOUNDARY, Layered intrusion, Sill, Geochemistry and Petrology, MASS-EXTINCTION EVENT, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, ddc:550, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, geography, SR-ND ISOTOPE, geography.geographical_feature_category, TRACE-ELEMENT, FREETOWN LAYERED COMPLEX, large igneous province (LIP), crustal contamination, Morocco, Geophysics, 13. Climate action, CONTINENTAL FLOOD BASALTS, Central Atlantic Magmatic Province (CAMP), basalt petrogenesis, Geology
Abstract

The Central Atlantic Magmatic Province (CAMP) is a large igneous province (LIP) composed of basic dykes, sills, layered intrusions and lava flows emplaced before Pangea break-up and currently distributed on the four continents surrounding the Atlantic Ocean. One of the oldest, best preserved and most complete sub-provinces of the CAMP is located in Morocco. Geochemical, geochronologic, petrographic and magnetostratigraphic data obtained in previous studies allowed identification of four strato-chemical magmatic units, i.e. the Lower, Intermediate, Upper and Recurrent units. For this study, we completed a detailed sampling of the CAMP in Morocco, from the Anti Atlas in the south to the Meseta in the north. We provide a complete mineralogical, petrologic (major and trace elements on whole-rocks and minerals), geochronologic (40Ar/39Ar and U–Pb ages) and geochemical set of data (including Sr–Nd–Pb–Os isotope systematics) for basaltic and basaltic–andesitic lava flow piles and for their presumed feeder dykes and sills. Combined with field observations, these data suggest a very rapid (

Published
2019
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3. Ultraprecise age and formation temperature of the Australasian tektites constrained by 40 Ar/ 39 Ar analyses

Author

Ela Eroglu, Fred Jourdan, Sébastien Nomade, Michael T.D. Wingate, Al Deino, Curtin University [Perth], Planning and Transport Research Centre (PATREC), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Paléocéanographie (PALEOCEAN), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Geological Survey of Western Australia, Berkeley Geochronology Center (BGC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Geophysics, 010504 meteorology & atmospheric sciences, Space and Planetary Science, 010502 geochemistry & geophysics, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 01 natural sciences, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience

Published
2018
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4. New 40Ar/39Ar ages and revised 40K/40Ar* data from nephelinitic–phonolitic volcanic successions of the Trindade Island (South Atlantic Ocean)

Author

Christophe Renac, Mauro Cesar Geraldes, Gustavo Luiz Campos Pires, Anderson Costa dos Santos, Fred Jourdan, Reiner Neumann, Everton Marques Bongiolo, programa de pos-graduacao em geologia, insituto de geociencias, universidade federal do rio de janeiro, Universidade do Estado do Rio de Janeiro - Faculdade de Geologia, Géoazur (GEOAZUR 7329), Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), Western Australian Argon Isotope Facility (WAAIF), The Institute for Geoscience Research [Perth] (TIGeR), School of Earth and Planetary Science [Perth - Curtin university], Curtin University [Perth], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC)-Curtin University [Perth], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC)-School of Earth and Planetary Science [Perth - Curtin university], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC), Centre for Mineral Technology (CETEM), Ministère de la Science et Technologie, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Western Australian Argon Isotope Facility, Department of Applied Geology & JdL-CMS, Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)

Subjects
geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Pleistocene, Ephemeral key, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Volcanism, 010502 geochemistry & geophysics, 01 natural sciences, Plume, Paleontology, Geophysics, Volcano, 13. Climate action, Geochemistry and Petrology, South American Plate, Period (geology), 14. Life underwater, Cenozoic, Geomorphology, Geology, 0105 earth and related environmental sciences
Abstract

International audience; The Trindade Island is located in the South Atlantic Ocean, 1170 km from the Brazilian coast and represents the eastern end of the submarine E–W Vitória–Trindade Chain. This is interpreted as the Trindade plume track beneath the South American plate during the Cenozoic. Almeida (1961) recognized five volcanogenic successions at Trindade in decreasing age: the Trindade Complex (TC) and the Desejado (DF), Morro Vermelho (MV), Valado (VF) and Paredão (PF) formations, composed of nephelinitic to phonolitic effusive-pyroclastic deposits, dykes and necks. Here, we present new 40Ar/39Ar ages and re-evaluation of available 40K/40Ar* data that, coupled with previous petrological information, allowed us to reconstruct the volcanic history of the island (i.e., 3.9–0.25 Ma) distinguishing near synchronous volcanic episodes and solving several stratigraphic uncertainties reported in the literature.The geochronological dataset show that the nephelinitic–phonolitic volcanism at Trindade was discontinuous throught time, being marked by periods of high volcanic activity and periods of quiescence, which suggests variable melt production and eruption rates. The peak of the volcanic activity occurred between 3.9 and 2.5 Ma (i.e., Lower Pliocene to Lower Pleistocene) that is represented by the TC, which correspond to the largest volume of volcanic deposits preserved in the island. The volcanic activity slows down progressively from 2.5 Ma to cease at ca. 1.6 Ma, period that is represented by the DF. This volcanism was followed by a quiescent period that lasted until the ephemeral nephelinitic volcanism of the MV (no age), VA (no age) and PF (ca. 0.25 Ma). Thus, the volcanic activity in Trindade was ceased completely at ca. 0.25 Ma, event registered in the uppermost volcanic deposits of the PF and that represents the last volcanic activity in the Brazilian territory.

Published
2016
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5. YBCs sanidine: A new standard for 40Ar/39Ar dating

Author

Huile Feng, Wenbei Shi, Lin Wu, Sébastien Nomade, Fei Wang, Haiqing Sang, Ching-Hua Lo, Rixiang Zhu, Liekun Yang, Hervé Guillou, Fred Jourdan, State Key Laboratory of Lithospheric Evolution (SKL), Institute of Geology and Geophysics [Beijing] (IGG), Chinese Academy of Sciences [Beijing] (CAS)-Chinese Academy of Sciences [Beijing] (CAS), Curtin University [Perth], Planning and Transport Research Centre (PATREC), National Taiwan University [Taiwan] (NTU), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Paléocéanographie (PALEOCEAN), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Geochemistry and Petrology, Neutron flux, Geochronology, Mineralogy, Geology, Sanidine, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

article i nfo Ar/ 39 Ar geochronology New standard YBCs sanidine The 40 Ar/ 39 Ar dating technique is based on neutron fluence monitors (standards). Recent investigation demon- 40 Ar/ 39 Ar dating. Aliquots were distributed to four international laboratories for analysis and intercalibration. The results show that YBCs crystals are homogenous in K content, 40 Ar⁎/ 39 ArK (F-value) and age at the single grain level. The standard deviations of the F-value and age have small ranges from 0.29% to 0.53% and from 0.42% to 0.52%, respectively. These show that YBCs is a suitable standard for 40 Ar/ 39 Ar geochronology. The

Published
2014
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6. Pliocene to Pleistocene vertical movements in the forearc of the Lesser Antilles subduction: insights from chronostratigraphy of shallow-water carbonate platforms (Guadeloupe archipelago)

Author

Jean-Len Léticée, Jean-Frédéric Lebrun, L. De Min, P. Münch, Auran Randrianasolo, Fred Jourdan, Chrystèle Verati, J.-M. Lardeaux, François Demory, B. Smith, Frédéric Quillévéré, Mihaela Carmen Melinte-Dobrinescu, Jean-Jacques Cornée, Dynamique de la Lithosphere, Géosciences Montpellier, Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Bassins, Université des Antilles et de la Guyane (UAG), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), National Institute of Marine Geology and Geo-ecology (GeoEcoMar ), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Manteau et Interfaces, Curtin University [Perth], Planning and Transport Research Centre (PATREC), Université des Antilles et de la Guyane (UAG)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), National Institute for Marine Geology and Geo-ecology (GeoEcoMar ), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), and Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)

Subjects
geography, Piacenzian, geography.geographical_feature_category, Pleistocene, Subduction, [SDE.MCG]Environmental Sciences/Global Changes, Geology, Late Miocene, Paleontology, chemistry.chemical_compound, chemistry, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Archipelago, Carbonate, 14. Life underwater, Chronostratigraphy, Forearc, Lesser Antilles subduction
Abstract

An integrated stratigraphic study was conducted on the shallow water carbonate platforms of the Guadeloupe archipelago to refine the tectonic evolution of the Lesser Antilles forearc. The carbonate platforms are now dated to the Zanclean–Calabrian interval, and their demise occurred between 1.5 and 1.07 Ma. The precise chronostratigraphy allows dating of the main extensional tectonic events since the late Miocene. An initial episode occurred during the late Miocene, related to the reactivation of inherited N130°E-trending shear zones, and led to the emergence of most parts of the forearc. Subsequently, Zanclean to early Piacenzian carbonate platforms developed in association with a general subsidence of the forearc. During the late Piacenzan, a second extensional episode occurred. At this time La Desirade underwent major uplift and emergence whereas most of the forearc remained submerged. Prior to 1.07 Ma, a third north–south extensional episode occurred and led to the final demise of the carbonate platforms. Thus the forearc was characterized by general subsidence since the early Pliocene interrupted by three main extensional episodes and related differential uplifts. This suggests that the Lesser Antilles subduction is probably erosive north of latitude 15°N since c . 5 Ma, related to aseismic ridge subduction. Supplementary data: Planktonic foraminiferal assemblages, calcareous nannofossil taxa associations, 40 Ar/ 39 Ar geochronological data and palaeomagnetic data are available at www.geolsoc.org.uk/SUP18724.

Published
2014
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7. Advances in 40 Ar/ 39 Ar dating: from archaeology to planetary sciences – introduction

Author

Darren F. Mark, Fred Jourdan, Chrystèle Verati, Western Australian Argon Isotope Facility, Department of Applied Geology & JdL-CMS, Curtin University [Perth], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC), NERC Argon Isotope Facility [Glasgow], Natural Environment Research Council (NERC)-Scottish Universities Environmental Research Centre (SUERC), University of Edinburgh-University of Glasgow-University of Edinburgh-University of Glasgow, Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Scottish Universities Environmental Research Centre (SUERC), University of Glasgow-University of Edinburgh-University of Glasgow-University of Edinburgh-Natural Environment Research Council (NERC), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Planetary science, 13. Climate action, Research council, Environmental research, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Geology, Ocean Engineering, Center (algebra and category theory), Archaeology, ComputingMilieux_MISCELLANEOUS, Water Science and Technology
Abstract

FRED JOURDAN1*, DARREN F. MARK2 & CHRYSTELE VERATI3 Western Australian Argon Isotope Facility, JdL Center & Department of Applied Geology, Curtin University, Perth, WA6845, Australia Natural Environment Research Council Argon Isotope Facility, Scottish Universities Environmental Research Centre, East Kilbride, G75 0QF, UK Universite de Nice Sophia Antipolis, GEOAZUR, Bât. 1, 250 rue Albert Einstein, Sophia Antipolis, 06560 Valbonne, France

Published
2014
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8. Isotopic fractionation of Cu in tektites

Author

Pierre Beck, Christian Koeberl, Fred Jourdan, Philippe Telouk, Frédéric Moynier, McDonnell Center for Space Sciences, Washington University in Saint Louis (WUSTL), Department of Earth and Planetary Sciences [St Louis], Department of Lithospheric Research [Wien], Universität Wien, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Western Australian Argon Isotope Facility, Department of Applied Geology & JdL-CMS, Curtin University [Perth], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC), Planning and Transport Research Centre (PATREC), Laboratoire de Sciences de la Terre (LST), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), NASA-Laser program : NNX09AM64G, Austrian Science Foundation : P18862-N10, Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Washington University in St Louis, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], LIBYAN DESERT GLASS, [SDE.MCG]Environmental Sciences/Global Changes, Mineralogy, Flux, COPPER, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Fractionation, 010502 geochemistry & geophysics, 01 natural sciences, SOURCE MASS-SPECTROMETRY, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Volatiles, 0105 earth and related environmental sciences, IMPACT GLASSES, Tektite, Continental crust, AUSTRALASIAN TEKTITES, Trace element, TRACE-ELEMENT, Libyan desert glass, NONG-TYPE TEKTITES, IVORY-COAST TEKTITES, SILICATE MELTS, 13. Climate action, IRON-METEORITES, Geology, Earth (classical element)
Abstract

International audience; Tektites are terrestrial natural glasses of up to a few centimeters in size that were produced during hypervelocity impacts on the Earth's surface. It is well established that the chemical and isotopic composition of tektites is generally identical to that of the upper terrestrial continental crust. Tektites typically have very low water content, which has generally been explained by volatilization at high temperature; however, the exact mechanism is still debated. Because volatilization can fractionate isotopes, comparing the isotopic composition of volatile elements in tektites with those of their source rocks may help to understand the physical conditions during tektite formation. Interestingly, volatile chalcophile elements (e.g., Cd and Zn) seem to be the only elements for which isotopic fractionation is known so far in tektites. Here, we extend this study to Cu, another volatile chalcophile element. We have measured the Cu isotopic composition for 20 tektite samples from the four known different strewn fields. All of the tektites (except the Muong Nong-types) are enriched in the heavy isotopes of Cu (1.98 < delta(61)Cu < 6.99) in comparison to the terrestrial crust (delta(65)Cu approximate to 0) with no clear distinction between the different groups. The Muong Nong-type tektites and a Libyan Desert Glass sample are not fractionated, (delta(65)Cu approximate to 0) in comparison to the terrestrial crust. To refine the Cu isotopic composition of the terrestrial crust, we also present data for three geological reference materials (delta(65)Cu approximate to 0). An increase of delta(65)Cu with decreasing Cu abundance probably reflects that the isotopic fractionation occurred by evaporation during heating. A simple Rayleigh distillation cannot explain the Cu isotopic data and we suggest that the isotopic fractionation is governed by a diffusion-limited regime. Copper is isotopically more fractionated than the more volatile element Zn (delta(66/64)Zn up to 2.49 parts per thousand). This difference of behavior between Cu and Zn is predicted in a diffusion-limited regime, where the magnitude of the isotopic fractionation is regulated by the competition between the evaporative flux and the diffusive flux at the diffusion boundary layer. Due to the difference of ionic charge in silicates (Zn(2+) vs. Cu(+)), Cu has a diffusion coefficient that is larger than that of Zn by at least two orders of magnitude. Therefore, the larger isotopic fractionation in Cu than in Zn in tektites is due to the significant difference in their respective chemical diffusivity. (C) 2009 Elsevier Ltd. All rights reserved.

Published
2010
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9. Major and trace element and Sr, Nd, Hf, and Pb isotope compositions of the Karoo large igneous province, Botswana-Zimbabwe: lithosphere vs mantle plume contribution

Author

Ali B Kampunzu, Gilbert Féraud, Fred Jourdan, Janne Blichert-Toft, Hervé Bertrand, U. Schärer, Laboratoire de Sciences de la Terre (LST), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Basalt, geography, geography.geographical_feature_category, Fractional crystallization (geology), 010504 meteorology & atmospheric sciences, Polybaric melting, Large igneous province, Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, Mantle (geology), Mantle plume, Craton, Geophysics, 13. Climate action, Geochemistry and Petrology, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Flood basalt, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

Journal of Petrology, v. 48, n. 6, p. 1043-1077, 2007. http://dx.doi.org/10.1093/petrology/egm010; International audience; We report major and trace element abundances for 147 samples and Sr, Nd, Hf, and Pb isotope compositions for a 36 sample subset of basaltic lava flows, sills, and dykes from the Karoo continental flood basalt (CFB) province in Botswana, Zimbabwe, and northern South Africa. Both low- and high-Ti (TiO2 < 2 wt % and > 2 wt %) rocks are included. MELTS modeling shows that these magmas evolved at low pressure (1 kbar) through fractional crystallization of gabbroic assemblages. Whereas both groups display enrichment in light rare earth elements (LREE) relative to heavy REE (HREE) and high field strength elements, and systematic negative Nb anomalies, they differ in terms of contrasting middle REE (MREE) to HREE fractionation, which is greater for the high-Ti basalts. This reflects different depths of melting of slightly enriched mantle sources: calculations suggest that the low-Ti basalts were generated by melting of a shallow spinel-bearing (2 % spinel) lherzolite, whereas the high-Ti magmas originated from a deeper-seated garnet-bearing (2–7% garnet) lherzolite. In most isotope plots, the high-Ti lavas together with the picrites define a common trend from Bulk Silicate Earth (BSE) to compositions with strongly negative ɛNdi and ɛHfi akin to those of some nephelinites and lamproites. The low-Ti rocks are shifted from BSE-like to more radiogenic Sr isotope ratios, indicative of upper crustal contamination. Trace element and isotope characteristics of the Karoo magmas require a combination of enrichment processes (subduction induced?) and long-term isolation of the mantle sources. We propose two distinct scenarios to explain the origin of the Karoo province. The first calls for polybaric melting of spatially heterogeneous, partially veined, sub-continental lithospheric mantle (SCLM). Calculations show that mixing between SCLM (∼BSE) and a strongly Nd–Hf unradiogenic nephelinite-like component (sediment input?) could account for the compositional variations of most of the high-Ti group lavas, whereas the mantle composition responsible for the low-Ti magmas is more likely to be similar to a vein-free, metasomatically enriched SCLM component. The second scenario involves mixing between two end-members represented by the SCLM and its deep-seated alkalic veins and a sub-lithospheric (asthenospheric- or ocean island basalt-like?) mantle plume. In this case, the data are compatible with an increasing mantle plume contribution as the plume rises and expands through the lithosphere. Regardless of which of the two scenarios is invoked, the spatial distribution of the low- and high-Ti magmas matches the relative positioning of the cratons and the Limpopo belt in such a way that strong control of the lithosphere on magma composition and distribution is a mandatory requirement of any petrogenetic model applied to the Karoo CFB.

Published
2007
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10. Karoo large igneous province: Brevity, origin, and relation to mass extinction questioned by new 40Ar/39Ar age data

Author

Hervé Bertrand, Gilbert Féraud, G. Tshoso, Bernard Le Gall, Fred Jourdan, Michael K. Watkeys, Ali Bashira Kampunzu, Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Sciences de la Terre (LST), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL)

Subjects
Extinction event, 010504 meteorology & atmospheric sciences, Earth science, Large igneous province, Geology, Geodynamics, 010502 geochemistry & geophysics, 01 natural sciences, Mantle plume, 13. Climate action, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Magmatism, Flood basalt, Plume model, 0105 earth and related environmental sciences
Abstract

The peak activities of continental flood basalts are currently considered as huge and brief (∼1 m.y.) magmatic events, with strong implications for geodynamics and biotic turnover. New 4 0 Ar/ 3 9 Ar dates on the Karoo flood basalts (southern Africa) show a longer duration of magmatism (∼8 m.y., with 6 m.y. for the main volume) with an apparent south-to-north migration, along with briefer distinctive pulses inside the province. This suggests that the Karoo province does not fit the general plume model invoked for most continental flood basalts (including the Karoo) and may explain the absence of a major contemporaneous mass extinction.

Published
2005
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11. The Okavango giant mafic dyke swarm (NE Botswana): its structural significance within the Karoo Large Igneous Province

Author

Fred Jourdan, W. Vétel, Jérôme Dyment, Hervé Bertrand, Charly Aubourg, G. Tshoso, Ali B Kampunzu, Bernard Le Gall, Gilbert Féraud, Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géosciences Marines (LGM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Sciences de la Terre (LST), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de tectonique (LT), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Botswana, 010504 meteorology & atmospheric sciences, Proterozoic, Large igneous province, Archean, Swarm behaviour, Structure, Geology, 15. Life on land, Karoo Large Igneous Province, 010502 geochemistry & geophysics, 01 natural sciences, Mantle plume, Giant mafic dyke swarm, Okavango, Sedimentary rock, Mafic, Petrology, Geomorphology, 0105 earth and related environmental sciences, Terrane
Abstract

The structural organization of a giant mafic dyke swarm, the Okavango complex, in the northern Karoo Large Igneous Province (LIP) of NE Botswana is detailed. This N110°E-oriented dyke swarm extends for 1500 km with a maximum width of 100 km through Archaean basement terranes and Permo-Jurassic sedimentary sequences. The cornerstone of the study is the quantitative analysis of N>170 (exposed) and N>420 (detected by ground magnetics) dykes evidenced on a ca. 80-km-long section lying in crystalline host-rocks, at high-angle to the densest zone of the swarm (Shashe area). Individual dykes are generally sub-vertical and parallel to the entire swarm. Statistical analysis of width data indicates anomalous dyke frequency (few data

Published
2005
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12. The Karoo triple junction questioned: evidence from Jurassic and Proterozoic Ar-40/Ar-39 ages and geochemistry of the giant Okavango dyke swarm (Botswana)

Author

Jean-Jacques Tiercelin, G. Tshoso, H. Bertrand, Gilbert Féraud, Fred Jourdan, B. Le Gall, Ali B Kampunzu, P. Capiez, Géoazur (GEOAZUR 6526), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Nice Sophia Antipolis (1965 - 2019) (UNS), and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Rift, 010504 meteorology & atmospheric sciences, Proterozoic, Triple junction, Geochemistry, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, Mantle plume, Paleontology, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Phanerozoic, Earth and Planetary Sciences (miscellaneous), engineering, Flood basalt, Plagioclase, Mafic, Geology, 0105 earth and related environmental sciences
Abstract

The lower Jurassic Karoo–Ferrar magmatism represents one of the most important Phanerozoic continental flood basalt (CFB) provinces. The Karoo CFB province is dominated by tholeiitic traps and apparently radiating giant dyke swarms covering altogether ca. 3×106 km2. This study focuses on the giant N110°-trending Okavango dyke swarm (ODS) stretching over 1500 km across Botswana. This dyke swarm represents the main (failed) arm of the so-called Karoo triple junction that is generally considered as a key marker of the impingement of the Karoo starting mantle plume head. ODS dolerites yield six new plagioclase 40Ar/39Ar plateau (and miniplateau) ages ranging from 178.7±0.7 and 180.9±1.3 Ma. The distribution of the ages along a narrow Gaussian curve suggests a short period of magmatic activity centered around 179 Ma, i.e., ∼5 Ma younger than the emplacement age of Karoo mafic magmas in the southern part of the Karoo CFB province (∼184). This age difference indicates that Karoo magmatism does not represent a short-lived event as is generally the case for most CFB but lasted at least 5 Ma over the whole province. In addition, small clusters of plagioclase separated from 28 other dykes and measured by “speedy” step-heating experiments (with mostly two to three steps), gave either “Karoo” or Proterozoic ages. Integrated ages of the Proterozoic rocks range from 851±6 to 1672±7 Ma, and one plateau age (959.1±4.6 Ma) and one possibly geologically significant weighted-mean age (982.7±4.0 Ma) were obtained. Proterozoic and Karoo mafic rocks are petrographically similar, but Proterozoic dykes display clear geochemical differences (e.g., TiO2 2.1%). Geochemical data combined with available Ar/Ar dates allow the identification of the two groups within a total set of 77 dykes investigated: ∼10% of the bulk ODS dykes are Proterozoic. Thus, the Jurassic Karoo ODS dykes were emplaced along reactivated Proterozoic structures and there is no pristine Jurassic Nuanetsi triple junction as commonly proposed. This throws into doubt the validity of the “active plume head” Karoo CFB rift models as being responsible for the observed “triple junction” dyke geometry.

Published
2004
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