Comparison of 40Ar-39Ar conventional and laser dating of biotites from the North Trégor Batholith

Ruffet, Gilles; Féraud, Gilbert; Amouric, M.

doi:10.1016/0016-7037(91)90138-u

Cited by 118 publications

(70 citation statements)

References 24 publications

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“…Heating steps were performed with a CO 2 Synrad  laser (Ruffet et al, 1991(Ruffet et al, , 1995. The five argon isotopes and the background baselines were measured in eleven cycles, in peak- All ages are reported at the 1 level.…”

Section: Methodsmentioning

confidence: 99%

The age of supergene manganese deposits in Katanga and its implications for the Neogene evolution of the African Great Lakes Region

Putter

Ruffet

Yans

et al. 2015

Ore Geology Reviews

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International audienceSupergene manganese deposits commonly contain K-rich Mn oxides with tunnel structure, such ascryptomelane, which are suitable for radiometric dating using the 39Ar–40Ar method. In Africa, Mn depositshave been dated by this method for localities in western and southern parts of the continent, whereas onlysome preliminary data are available for Central Africa. Herewe present new39Ar–40Ar ages for Mnoxide samplesof the Kisenge deposit, in southwestern Katanga, Democratic Republic of the Congo. The samples represent supergeneMn oxide deposits that formed at the expense of primary Paleoproterozoic rhodochrosite-dominatedcarbonate ores. Main phases of Mn oxide formation are dated at c. 10.5 Ma, 3.6 Ma and 2.6 Ma for a core thatcrosses a mineralized interval. The latter shows a decrease in age with increasing depth, recording downwardpenetration of a weathering front. Surface samples of the Kisenge deposits also record a ≥c.19.2 Ma phase, aswell as c. 15.7 Ma, 14.2 Ma and 13.6 Ma phases. The obtained ages correspond to distinct periods of paleosurfacedevelopment and stability during the Mio-Pliocene in Katanga. Because Katanga is a key area bordered to theNorth by the Congo Basin and to the East by the East African Rift System, these ages also provide constraintsfor the geodynamic evolution of the entire region. For the Mio-Pliocene, the Kisenge deposits record ages thatare not systematically found elsewhere in Africa, although the 10.5–11 Ma event corresponds to a roughly simultaneousevent in the Kalahari Manganese Field, South Africa. The rest of the Katanga paleosurface record differssomewhat fromrecords for other parts of Africa, forwhich older, Eocene ages have been obtained. This differenceis most probably related to the specific regional geodynamic context: uplift of the East African Plateau, with associatederosion, and the opening of the East African Rift System at c. 25 Ma are events whose effects, in thestudy area, interfere with those of processes responsible for the development of continent-wide paleosurfaces

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Section: Methodsmentioning

confidence: 99%

The age of supergene manganese deposits in Katanga and its implications for the Neogene evolution of the African Great Lakes Region

Putter

Ruffet

Yans

et al. 2015

Ore Geology Reviews

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“…It gives a partially discordant age spectrum, characterized by argon loss at low experimental temperature and a small bump at intermediate temperature (e.g. Ruffet et al, 1991 for a possible explanation of this shape). An integrated age of 290 F 4 Ma has been calculated over 90% of the argon released, which corresponds to the Carboniferous -Permian boundary, and is slightly older than an early K -Ar age from the Sögüt granitoid (272 Ma, C ßogulu and Krummenacher, 1967).…”

Section: Geochronologymentioning

confidence: 99%

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction

Okay

Monod

Monié

2002

Lithos

152

100

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Triassic eclogite and blueschist facies rocks occur as a thrust sheet, 25-km long and over 2-km thick, in an Eocene fold-andthrust belt in northwest Turkey along the İzmir -Ankara suture. The thrust sheet consists mainly of metabasites with minor marble, phyllite and metachert, and rare lenses of serpentinite. The common blueschist facies mineral assemblage in the metabasites is sodic amphibole + epidote + albite + chlorite + phengite F garnet. Sodic amphibole commonly shows replacement by barroisite, and there is continuous petrographic transition from blueschist -metabasites to barroisite-bearing epidoteamphibolites. Eclogite with the mineral assemblage of garnet + sodic pyroxene + sodic -calcic amphibole + epidote is found only in one locality. P -T conditions of the epidote -blueschist facies metamorphism are estimated as 450 F 50 jC and 11 F 2 kbar. The blueschist formation was followed by a decrease in pressure and increase in temperature, leading to the development of barroisite-bearing epidote -amphibolites. Phengite, sodic amphibole and barroisite Ar/Ar ages from three metabasic rocks range between 215 and 205 Ma, and indicate Late Triassic high-pressure metamorphism. The Triassic blueschists in northwest Turkey constitute part of a much larger allochthonous tectonic unit of Triassic mafic volcanic rocks. They probably represent the upper layers of a Triassic oceanic plateau, which was accreted to the Laurasian margin during the latest Triassic. The close spatial association of the Triassic and Cretaceous blueschists along the İzmir -Ankara suture suggests that the suture represents a long-lived plate boundary of Late Palaeozoic to early Tertiary age. D

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“…The step-heating experiment procedure was described in details by Ruffet et al (1991Ruffet et al ( , 1995. The single grains were heated for analyses with a continuous argon-ion laser.…”

Section: Ar-39 Ar Analytical Proceduresmentioning

confidence: 99%

Offshore Oligo-Miocene volcanic fields within the Corsica-Liguria Basin: Magmatic diversity and slab evolution in the western Mediterranean Sea

Réhault

Honthaas

Guennoc

et al. 2012

Journal of Geodynamics

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The European and Corsica-Sardinia margins of the Ligurian Sea (western Mediterranean) have been affected by a geochemically diverse igneous activity, offshore and onshore, since the Eocene. This magmatism occurred in a global subduction-related framework. On the European side, the oldest Tertiary magmatism dated at ca. 35 Ma was mainly calc-alkaline. It included the emplacement of plutonic bodies of adakitic affinity, such as the quartz microdiorite laccolith locally referred to as "esterellite". Younger magmatic events on-land within the whole Ligurian domain were mostly medium-K or K-rich calc-alkaline. Miocene volcanic activity was important in Sardinia, where andesites and ignimbrites were erupted during several magmatic cycles. In Corsica, it was minor although it emplaced lamprophyres near Sisco at 15 Ma.Dredging and diving cruises conducted in the Ligurian Sea during the last thirty years allowed us to collect a number of submarine samples. We discuss here their geochemistry (major and trace elements) and their whole-rock K-Ar ages and mineral 40 Ar-39 Ar plateau ages.Around 15 Ma, minor amounts of adakitic lavas were emplaced off southwestern Corsica, in the deepest part of the Liguria-Corsica Basin. They rested over the thinnest southwestern Corsica Hercynian continental crust. Closer to the coast, contemporaneous calc-alkaline rocks erupted 2 on a less thinned crust. The adakitic events could be indicative of either the final stages of active subduction, or alternatively of a slab tearing linked to the southeastern retreat and steepening of the slab. The latter event could be connected with the end of the Corsica-Sardinia block drifting and its correlative eastern collision.Younger volcanic effusions, dated at 14-6 Ma, occurred mostly northwest and north of Corsica. K-rich calc-alkaline basalts, shoshonites and K-rich trachytes were emplaced during this period, and alkali basalts erupted as early as 12 Ma in Sardinia. In the Toulon area, alkali basalts dated at 7-6 Ma represent the last onshore activity just before the Messinian crisis, and the Pliocene alkali basaltic outpouring in Sardinia. We propose to link these latter volcanic events to the development of a slab window in a post-collisional tectonic framework.

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Comparison of 40Ar-39Ar conventional and laser dating of biotites from the North Trégor Batholith

Cited by 118 publications

References 24 publications

The age of supergene manganese deposits in Katanga and its implications for the Neogene evolution of the African Great Lakes Region

The age of supergene manganese deposits in Katanga and its implications for the Neogene evolution of the African Great Lakes Region

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction

Offshore Oligo-Miocene volcanic fields within the Corsica-Liguria Basin: Magmatic diversity and slab evolution in the western Mediterranean Sea

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