Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa

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dc.contributor.authorMoyen J.-F.
dc.contributor.authorStevens G.
dc.contributor.authorKisters A.
dc.date.accessioned2011-05-15T16:02:07Z
dc.date.available2011-05-15T16:02:07Z
dc.date.issued2006
dc.description.abstractAlthough plate tectonics is the central geological process of the modern Earth, its form and existence during the Archaean era (4.0-2.5 Gyr ago) are disputed. The existence of subduction during this time is particularly controversial because characteristic subduction-related mineral assemblages, typically documenting apparent geothermal gradients of 15°C km-1 or less, have not yet been recorded from in situ Archaean rocks (the lowest recorded apparent geothermal gradients are greater than 25°C km -1). Despite this absence from the rock record, low Archaean geothermal gradients are suggested by eclogitic nodules in kimberlites and circumstantial evidence for subduction processes, including possible accretion-related structures, has been reported in Archaean terrains. The lack of spatially and temporally well-constrained high-pressure, low-temperature metamorphism continues, however, to cast doubt on the relevance of subduction-driven tectonics during the first 1.5 Gyr of the Earth's history. Here we report garnet-albite-bearing mineral assemblages that record pressures of 1.2-1.5 GPa at temperatures of 600-650°C from supracrustal amphibolites from the mid-Archaean Barberton granitoid-greenstone terrain. These conditions point to apparent geothermal gradients of 12-15°C-similar to those found in recent subduction zones-that coincided with the main phase of terrane accretion in the structurally overlying Barberton greenstone belt. These high-pressure, low-temperature conditions represent metamorphic evidence for cold and strong lithosphere, as well as subduction-driven tectonic processes, during the evolution of the early Earth. © 2006 Nature Publishing Group.
dc.description.versionArticle
dc.identifier.citationNature
dc.identifier.citation442
dc.identifier.citation7102
dc.identifier.issn280836
dc.identifier.other10.1038/nature04972
dc.identifier.urihttp://hdl.handle.net/10019.1/12320
dc.subjectGeology
dc.subjectGeothermal energy
dc.subjectHigh pressure effects
dc.subjectLow temperature effects
dc.subjectMineral resources
dc.subjectRocks
dc.subjectGeological processes
dc.subjectGeothermal gradients
dc.subjectMetamorphism
dc.subjectSubduction
dc.subjectSupracrustal amphibolites
dc.subjectTectonics
dc.subjectamphibole
dc.subjectArchean
dc.subjectgeothermal gradient
dc.subjectkimberlite
dc.subjectmetamorphism
dc.subjectplate tectonics
dc.subjectsubduction
dc.subjectarticle
dc.subjectevolution
dc.subjectgeographic and geological phenomena
dc.subjectgeological time
dc.subjectlow temperature
dc.subjectmetamorphosis
dc.subjectpriority journal
dc.subjectSouth Africa
dc.subjectAfrica
dc.subjectBarberton
dc.subjectMpumalanga
dc.subjectSouth Africa
dc.subjectSouthern Africa
dc.subjectSub-Saharan Africa
dc.titleRecord of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa
dc.typeArticle
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