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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Africa
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Southern Africa
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Barberton greenstone belt (15)
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Kaapvaal Craton (6)
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South Africa
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Mpumalanga South Africa
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Barberton Mountain Land (4)
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Transvaal region (4)
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Witwatersrand (3)
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Swaziland (1)
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Zimbabwe
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Belingwe greenstone belt (1)
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Arctic region
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Greenland
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Isua Belt (1)
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West Greenland (1)
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Australasia
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Australia (1)
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Canada
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Eastern Canada
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Ontario (1)
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North America
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Canadian Shield
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Superior Province
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Wabigoon Belt (1)
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commodities
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barite deposits (2)
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metal ores
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antimony ores (1)
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gold ores (3)
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mineral deposits, genesis (2)
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elements, isotopes
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carbon
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C-13/C-12 (2)
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isotope ratios (2)
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isotopes
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stable isotopes
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C-13/C-12 (2)
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Cr-53/Cr-52 (1)
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O-18/O-16 (1)
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S-34/S-32 (2)
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-
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metals
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antimony (1)
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chromium
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Cr-53/Cr-52 (1)
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hafnium (1)
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platinum group
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iridium (1)
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silver (1)
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oxygen
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O-18/O-16 (1)
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sulfur
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S-34/S-32 (2)
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fossils
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cyanobacteria (1)
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geochronology methods
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paleomagnetism (1)
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Sm/Nd (1)
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U/Pb (4)
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U/Th/Pb (1)
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geologic age
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Precambrian
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Archean
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Fig Tree Group (20)
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Neoarchean
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Amitsoq Gneiss (1)
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Paleoarchean (2)
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Central Rand Group (1)
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Onverwacht Group (6)
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Pongola Supergroup (1)
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Transvaal Supergroup (1)
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igneous rocks
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igneous rocks
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plutonic rocks
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granites (2)
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ultramafics (1)
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volcanic rocks
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komatiite (2)
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metamorphic rocks
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metamorphic rocks
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gneisses (1)
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metasedimentary rocks
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metasandstone (1)
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metasiltstone (1)
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metavolcanic rocks (2)
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turbidite (2)
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meteorites
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meteorites
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stony meteorites
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chondrites
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carbonaceous chondrites (1)
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minerals
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arsenides
-
arsenopyrite (1)
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carbonates
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siderite (1)
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minerals (1)
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oxides
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hematite (1)
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maghemite (1)
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silicates
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orthosilicates
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nesosilicates
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zircon group
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zircon (6)
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sheet silicates
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clay minerals (1)
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-
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sulfides
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arsenopyrite (1)
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Primary terms
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absolute age (6)
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Africa
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Southern Africa
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Barberton greenstone belt (15)
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Kaapvaal Craton (6)
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South Africa
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Mpumalanga South Africa
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Barberton Mountain Land (4)
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Transvaal region (4)
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Witwatersrand (3)
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Swaziland (1)
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Zimbabwe
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Belingwe greenstone belt (1)
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-
-
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Arctic region
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Greenland
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Isua Belt (1)
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West Greenland (1)
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-
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Australasia
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Australia (1)
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barite deposits (2)
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Canada
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Eastern Canada
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Ontario (1)
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-
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carbon
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C-13/C-12 (2)
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crust (4)
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crystal chemistry (1)
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deformation (2)
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economic geology (3)
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faults (2)
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folds (1)
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fractures (1)
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geochemistry (5)
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geochronology (1)
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igneous rocks
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plutonic rocks
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granites (2)
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ultramafics (1)
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volcanic rocks
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komatiite (2)
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-
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inclusions
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fluid inclusions (2)
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intrusions (3)
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isotopes
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stable isotopes
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C-13/C-12 (2)
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Cr-53/Cr-52 (1)
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O-18/O-16 (1)
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S-34/S-32 (2)
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-
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metal ores
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antimony ores (1)
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gold ores (3)
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metals
-
antimony (1)
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chromium
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Cr-53/Cr-52 (1)
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hafnium (1)
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platinum group
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iridium (1)
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silver (1)
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metamorphic rocks
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gneisses (1)
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metasedimentary rocks
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metasandstone (1)
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metasiltstone (1)
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metavolcanic rocks (2)
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metamorphism (3)
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metasomatism (2)
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meteorites
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stony meteorites
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chondrites
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carbonaceous chondrites (1)
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-
-
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mineral deposits, genesis (2)
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minerals (1)
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North America
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Canadian Shield
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Superior Province
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Wabigoon Belt (1)
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-
-
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oxygen
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O-18/O-16 (1)
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paleogeography (1)
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paleomagnetism (1)
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paragenesis (1)
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petrology (1)
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Precambrian
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Archean
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Fig Tree Group (20)
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Neoarchean
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Amitsoq Gneiss (1)
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Paleoarchean (2)
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Central Rand Group (1)
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Onverwacht Group (6)
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Pongola Supergroup (1)
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Transvaal Supergroup (1)
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sedimentary petrology (2)
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sedimentary rocks
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chemically precipitated rocks
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chert (3)
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iron formations
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banded iron formations (1)
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jaspilite (1)
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clastic rocks
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arenite
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quartz arenite (1)
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black shale (1)
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graywacke (2)
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mudstone (1)
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sandstone (1)
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-
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sedimentary structures
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biogenic structures
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stromatolites (1)
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graded bedding (1)
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planar bedding structures
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ripple drift-cross laminations (1)
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sole marks (1)
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turbidity current structures (1)
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sedimentation (3)
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stratigraphy (1)
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structural geology (1)
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sulfur
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S-34/S-32 (2)
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tectonics (3)
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sedimentary rocks
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sedimentary rocks
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chemically precipitated rocks
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chert (3)
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iron formations
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banded iron formations (1)
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jaspilite (1)
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clastic rocks
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arenite
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quartz arenite (1)
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-
black shale (1)
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graywacke (2)
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mudstone (1)
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sandstone (1)
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-
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turbidite (2)
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-
sedimentary structures
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sedimentary structures
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biogenic structures
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stromatolites (1)
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graded bedding (1)
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planar bedding structures
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ripple drift-cross laminations (1)
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sole marks (1)
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turbidity current structures (1)
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-
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sediments
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turbidite (2)
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Fig Tree Group
Progressive accretion recorded in sedimentary rocks of the 3.28–3.23 Ga Fig Tree Group, Barberton Greenstone Belt
Silver Isotopes as a Source and Transport Tracer for Gold: A Reconnaissance Study at the Sheba and New Consort Gold Mines in the Barberton Greenstone Belt, Kaapvaal Craton, South Africa
Mineral transformations during thermal demagnetization of sideritic jasper mesobands in jaspilites of the ~3.25 Ga Fig Tree Group in the Barberton Greenstone Belt, Kaapvaal craton (South Africa)
Detrital zircon geochronology of sandstones of the 3.6–3.2 Ga Barberton greenstone belt: No evidence for older continental crust
Gold on the Kaapvaal Craton, outside the Witwatersrand Basin, South Africa
Crustal fracturing and chert dike formation triggered by large meteorite impacts, ca. 3.260 Ga, Barberton greenstone belt, South Africa
U–Pb and Hf isotope data of detrital zircons from the Barberton Greenstone Belt: constraints on provenance and Archaean crustal evolution
This review of the current knowledge of impact spherule layers in the Barberton greenstone belt, together with new petrographic, geochemical, and field data on a number of impact and volcanic spherical particle horizons, highlight a number of problems with the proposition of frequent and large meteorite impacts during mid-Archean times. Field data indicate that some of the four previously proposed impact spherule layers may be laterally correlative units that may have formed from the same impact event. Petrographic work reveals the presence of volcaniclastic particles associated with some spherule layers, while other layers not regarded as impact deposits contain clasts commonly observed in the spherule beds. Major and trace element compositions of spherule layers reflect the composition of the immediate host rocks. The existing platinum group element and chromium isotope data are difficult to reconcile with the current knowledge of the composition of meteoritic debris. A thorough discussion of these problems is necessary before meaningful estimates of Archean impact flux and bolide diameters should be attempted.
Carbon and sulfur isotopes have been measured on samples from four Archean greenstone belts dating from 3.8 Ga to 2.7 Ga, in order to trace metabolic changes as life evolved over this one-billion-year period. In the Isua Greenstone Belt (3.8 Ga), Greenland, δ 34 S in sulfide minerals from sedimentary sequences range from −3.8‰ to +3.4‰. δ 13 C red measured in BIFs, turbidites and conglomerates vary from −29.6‰ to −14.7‰; this range permits us to hypothesize the presence of hyperthermophilic and chemotrophic species in transient settings, or possibly pelagic photoautotrophic microbes, or both. In the Barberton Greenstone Belt, South Africa, sulfide minerals show δ 34 S values from +1.5‰ to +5.6‰. Black shales have δ 13 C red values from −32.4‰ to −5.7‰, suggesting that oxygenic photosynthetic and sulfate-reducing bacteria were present by ca. 3.24 Ga. The δ 13 C red measured in the stromatolites of Steep Rock Lake (3.0 Ga), Ontario, Canada, are from −30.6‰ to −21.6‰, giving clear evidence for occupation of a shallow water environment by cyanobacteria. The wide isotopic ranges for δ 34 S in sulfides from −21.1‰ to +16.7‰ and for δ 13 C red in carbon-rich cherts and black shales from −43.4‰ to −7.2‰ in the Belingwe Greenstone Belt, Zimbabwe, indicate that photosynthetic microbial mat communities were well established at 2.7 Ga. In these well-preserved Late Archean formations, modern-style biological sulfur and carbon cycles may have been in operation. The δ 34 S and δ 13 C red ranges, respectively 37‰ and 36‰, indicate a great variety of biological processes interacting with each other.