Early Precambrian Basic Magmatism

1 Introduction: basic magmatism and crustal evolution.- 1.1 Early thermal and magmatic history of the Earth.- 1.2 Early Precambrian oceans and greenstone belts.- 1.3 Continental crust and the major basic intrusions.- I General Aspects.- 2 Archaean basic magmas.- 2.1 Distribution of Archaean basic volcanic suites.- 2.1.1 Greenstone belts.- 2.1.2 High-grade gneiss terranes.- 2.2 Komatiites.- 2.3 Tholeiitic basalts.- 2.4 Komatiitic basalts.- 2.5 Petrogenesis.- 2.5.1 Komatiites.- 2.5.2 Komatiitic basalts.- 2.5.3 Tholeiitic basalts.- 2.5.4 Archaean ‘oceanic’ basic magmatism.- 2.6 The Archaean mantle.- 2.6.1 Mantle evolution.- 2.6.2 Mantle heterogeneity.- 2.7 Phanerozoic analogues of Archaean mafic volcanism.- 2.7.1 Komatiites.- 2.7.2 Komatiitic basalts.- 2.7.3 Tholeiitic basalts.- 2.8 Concluding remarks.- 3 Geochemical characteristics of Precambrian basaltic greenstones.- 3.1 Introduction.- 3.2 Classification of greenstone basalts.- 3.3 Geochemical characteristics.- 3.4 Precambrian mantle sources.- 3.5 Discussion.- 3.5.1 Selective preservation of lithological assemblages.- 3.5.2 Early and late Archaean greenstone basalts.- 3.5.3 The Archaean–Proterozoic boundary.- 3.6 Conclusions.- 4 Early Precambrian layered intrusions.- 4.1 Introduction: intrusion and crystallisation mechanisms.- 4.2 The Bush veld Complex.- 4.2.1 Regional setting.- 4.2.2 Intrusion form.- 4.2.3 Lithology.- 4.2.4 Mineralogy.- 4.2.5 Parental magma.- 4.3 The Stillwater Complex.- 4.3.1 Regional setting.- 4.3.2 Intrusion form.- 4.3.3 Lithology.- 4.3.4 Mineralogy.- 4.3.5 Parental magma.- 4.4 Dyke-like layered intrusions.- 4.4.1 Great Dyke of Zimbabwe.- 4.4.2 Finnish layered intrusions.- 4.4.3 Jimberlana intrusion.- 4.5 Archaean anorthosite complexes.- 4.6 Other layered intrusions.- 4.6.1 Kaapvaal craton.- 4.6.2 Yilgarn Block.- 4.6.3 Pilbara Block.- 4.6.4 Superior Province.- 4.7 Tectonic setting and petrogenesis.- 4.8 Concluding remarks.- 5 Noritic magmatism.- 5.1 Introduction: high-Mg basic rock types.- 5.2 Mineralogy.- 5.3 Geochemistry.- 5.4 Petrogenesis.- 5.4.1 Komatiites, SHMB, ‘U’-type magmas, norites and boninites.- 5.4.2 Chemical mobility and alteration.- 5.4.3 Fractional crystallisation.- 5.4.4 Degree of partial melting.- 5.4.5 Magma mixing.- 5.4.6 Crustal contamination.- 5.4.7 Mantle metasomatism.- 5.4.8 KREEP: a lunar analogue?.- 5.5 Concluding remarks.- 6 Mantle evolution.- 6.1 Introduction.- 6.2 Mantle processes.- 6.2.1 Convection.- 6.2.2 The lithosphere.- 6.2.3 Geoid anomalies and convection scales.- 6.2.4 Magmatism.- 6.3 Thermal evolution of the mantle.- 6.3.1 Geological evidence.- 6.3.2 The thermal state: convection models.- 6.3.3 Initial thermal state and ‘magma oceans’?.- 6.4 Melting in the early Precambrian mantle.- 6.4.1 Melt production at higher temperatures.- 6.4.2 Heat loss by melting.- 6.4.3 Komatiites.- 6.5 Chemical evolution of the early mantle.- 6.5.1 Chemical reservoirs.- 6.5.2 The growth of geochemical resevoirs.- 6.5.3 Mantle chemistry: primitive mantle and crustal depletion.- 6.5.4 The timing of crustal growth.- 6.5.5 U–Th–Pb systematics: crustal or lower mantle recycling?.- 6.5.6 Crust formation.- 6.6 Conclusions.- 7 Lunar magmatism.- 7.1 Introduction.- 7.2 Lunar highland rocks.- 7.2.1 Anorthosites.- 7.2.2 Mg-suite.- 7.2.3 Petrogenesis.- 7.3 Mare basalts.- 7.3.1 Petrography and mineralogy.- 7.3.2 Volcanic glasses.- 7.3.3 Age of mare basalts.- 7.3.4 Origin of mare basalts.- 7.4 KREEP basalts.- 7.5 Comparison with terrestrial magmatism.- 7.5.1 Anorthosites.- 7.5.2 Basalts.- 7.6 Concluding remarks.- 8 Mineralisation associated with early Precambrian basic magmatism.- 8.1 Introduction.- 8.2 Nickel mineralisation: Archaean volcanic suites.- 8.2.1 The komatiite–sulphide association.- 8.2.2 Typical greenstone belts.- 8.2.3 Kambalda and Scotia deposits.- 8.2.4 Summary and genetic models.- 8.3 Gold mineralisation in volcanic suites.- 8.3.1 Gold production from basic rocks.- 8.3.2 Lode deposits.- 8.3.3 Crustal setting.- 8.3.4 Role of basic magmatism.- 8.3.5 Gold and tholeiitic versus calc-alkaline magmatism: an Archaean enigma?.- 8.4 Chromite mineralisation: major layered intrusions.- 8.4.1 Stratigraphy.- 8.4.2 Textures.- 8.4.3 Geochemistry.- 8.4.4 Petrogenesis.- 8.5 Platinum group elements (PGE): layered complexes.- 8.5.1 Reef characteristics.- 8.5.2 Geochemistry.- 8.5.3 Petrogenesis.- 8.6 Closing remarks.- II Regional Syntheses.- 9 Early Precambrian basic rocks of the USA.- 9.1 Introduction.- 9.2 The Minnesota–Wisconsin region.- 9.2.1 Early Archaean suites.- 9.2.2 Late Archaean basic metavolcanics.- 9.2.3 Early Proterozoic rocks.- 9.2.4 Tectonic implications.- 9.3 Wyoming Province: Archaean metavolcanic rocks.- 9.3.1 Early Archaean.- 9.3.2 Late Archaean.- 9.4 Wyoming Province: intrusive rocks.- 9.4.1 Southern Idaho, northern Utah and Nevada.- 9.4.2 Black Hills, South Dakota.- 9.4.3 Southern Wyoming and northern Colorado.- 9.4.4 Stillwater Complex and minor intrusions, Beartooth Mountains.- 9.4.5 Tobacco Root and neighbouring mountains, southwestern Montana.- 9.4.6 Bighorn Mountains.- 9.4.7 Teton Mountains.- 9.4.8 Wind River Range.- 9.4.9 Owl Creek Mountains.- 9.4.10 Granite, Seminoe, Ferris, Casper and northern Laramie Mountains.- 9.4.11 Summary of basic intrusive rocks, Wyoming Province.- 9.5 Early to mid-Proterozoic metavolcanic belts of western central USA.- 10 Early Precambrian basic rocks of the Canadian Shield.- 10.1 Introduction.- 10.2 Superior Province.- 10.3 Granite–greenstone terranes.- 10.3.1 Platform sequences.- 10.3.2 Mafic plain volcanism.- 10.3.3 Arc volcanism.- 10.3.4 Pull-apart basins.- 10.3.5 Late-stage mafic magmatism.- 10.4 Mafic–ultramafic intrusions.- 10.4.1 Platform terranes.- 10.4.2 Arc terranes.- 10.5 Slave Province.- 10.6 Rae Province.- 10.7 Post-tectonic dykes.- 10.8 Summary and conclusions.- 11 Early Precambrian basic rocks of Greenland and Scotland.- 11.1 Introduction.- 11.2 Age and distribution of the basic rocks.- 11.2.1 Archaean suites.- 11.2.2 Proterozoic units.- 11.3 Early Archaean volcanism: the Isua–Akilia association.- 11.4 Mid-Archaean basic magmatism.- 11.4.1 Ameralik dykes.- 11.4.2 Metavolcanic suites.- 11.4.3 Fiskenaesset-type gabbro–anorthosite complexes.- 11.4.4 ‘Intra-Nûk’dykes.- 11.4.5 Archaean basic rocks of Scotland.- 11.5 Early Proterozoic basic magmatism.- 11.5.1 Ketilidian, Nagssugtoqidian and Rinkian volcanics, Greenland.- 11.5.2 Early Proterozoic basic dyke swarms of Greenland.- 11.5.3 Loch Maree Group metavolcanics, northwest Scotland.- 11.5.4 Early Proterozoic intrusive basic rocks of Scotland.- 11.6 Basic magmatic evolution and crustal growth in the North Atlantic craton.- 12 Early Precambrian basic rocks of the Baltic Shield.- 12.1 Introduction.- 12.2 The Archaean domain.- 12.3 Lapponian Supergroup (earliest Proterozoic).- 12.4 Early Proterozoic layered gabbroic complexes.- 12.5 Supracrustal belts marginal to the Lapland Granulite Complex.- 12.6 Karelian Supergroup (early Proterozoic).- 12.7 Marginal zone of the Svecofennian Domain.- 12.7.1 Karelidic Schist Belt.- 12.7.2 Early Proterozoic ophiolitic (?) complexes.- 12.8 Basic rocks of the Svecofennian Domain.- 12.8.1 Northern Province.- 12.8.2 Southern Province.- 12.8.3 Central Province.- 12.9 Syn- and post-orogenic intrusions.- 12.10 Concluding remarks.- 13 Early Precambrian basic rocks of China.- 13.1 Introduction.- 13.2 Distribution, metamorphism and age.- 13.2.1 Eastern Hebei Province: the Qianxi Group.- 13.2.2 Shandong Province: the Taishan Complex.- 13.2.3 Northeastern China (Manchuria): the Anshan Group.- 13.2.4 Inner Mongolia (Yingshan region): the Jining and Wulashan Groups.- 13.2.5 Shanxi (Taihang–Wutai–Luliang region): the Fuping and Wutai Groups.- 13.2.6 Henan Province: the Dengfeng and Taihua Groups.- 13.3 Geochemistry and petrogenesis.- 13.3.1 Bulk-rock chemistry and trace element differentiation.- 13.3.2 REE geochemistry.- 13.3.3 Nb anomalies.- 13.4 Implications for early continental evolution.- 13.4.1 Nd-Sr isotopic constraints.- 13.4.2 Amphibolite–TTG gneiss relationships.- 13.5 Conclusions.- 14 Early Precambrian basic rocks of Australia.- 14.1 Introduction.- 14.2 Distribution and stratigraphy.- 14.2.1 Archaean rocks.- 14.2.2 Proterozoic mobile belts and dyke swarms.- 14.3 Diversity of basic magmatism.- 14.3.1 Komatiites.- 14.3.2 Tholeiites.- 14.3.3 Siliceous high-Mg basalts (SHMB) and high-Mg basalts (HMB).- 14.3.4 Calc-alkaline mafic rocks.- 14.4 Magmatic and thermal evolution.- 14.4.1 Earliest Archaean (4.2–3.8 Ga).- 14.4.2 Early to mid-Archaean (3.6–2.9 Ga).- 14.4.3 Late Archaean (2.9–2.5 Ga).- 14.4.4 Early Proterozoic (2.7–1.8 Ga).- 14.5 Petrogenetic synthesis.- 15 Early Precambrian basic rocks of India.- 15.1 Introduction.- 15.2 The Dharwar craton.- 15.2.1 Greenstone belts.- 15.2.2 High-grade ultrabasic–basic complexes.- 15.2.3 Anorthosite complexes.- 15.2.4 High-grade basic lenses.- 15.2.5 Dykes.- 15.3 The Singhbhum craton.- 15.4 The Aravalli craton.- 15.5 Discussion.- 15.5.1 Geochemical variation of basic rocks with metamorphic grade.- 15.5.2 Early Precambrian basic magmatism and the evolution of the Indian Shield.- 16 Early Precambrian basic rocks of Africa.- 16.1 Introduction.- 16.2 Distribution of Archaean rocks in Africa.- 16.3 North and West Africa.- 16.3.1 Uweinat Inlier.- 16.3.2 Reguibat Rise.- 16.3.3 Guinea Rise.- 16.3.4 Greenstone belts of Sierra Leone.- 16.4 Equatorial Africa.- 16.4.1 Zaire granite–greenstone terrane.- 16.4.2 Tanzania granite–greenstone terrane.- 16.4.3 Greenstone belts of Equatorial Africa.- 16.5 Southern Africa.- 16.5.1 Zimbabwe.- 16.5.2 Kaapvaal Craton.- 16.5.3 Barberton greenstone belt.- 16.5.4 Pongola Supergroup.- 16.5.5 Ventersdorp Supergroup.- 16.6 Tectonic settings.- 16.7 Final comment.- 17 Early Precambrian basic rocks of South America.- 17.1 Introduction.- 17.2 Archaean basic volcanism.- 17.2.1 Imataca Complex, Venezuela.- 17.2.2 Bimodal volcanism, Serra dos Carajás.- 17.3 Archaean greenstone belts.- 17.3.1 Crixás greenstone belt.- 17.3.2 Rio das Velhas greenstone belt.- 17.3.3 Piumhi greenstone belt.- 17.3.4 Morro do Ferro greenstone belt.- 17.3.5 Greenstone belts of the southeastern Guaporé Shield.- 17.4 Proterozoic greenstone belts.- 17.4.1 Mazaruni Group, Guyana.- 17.4.2 Paramacca Series, French Guiana.- 17.4.3 Vila Nova and Serra do Navio belts, Amapá, Brazil.- 17.4.4 Rio Itapicuru greenstone belt.- 17.5 Early Precambrian mafic–ultramafic plutonic complexes.- 17.5.1 Cana Brava complex.- 17.5.2 Niquelândia complex.- 17.5.3 Barro Alto complex.- 17.5.4 Americano do Brasil layered complex.- 17.5.5 Caraiba complex.- 17.5.6 Rio do Jacare sill.- 17.5.7 Jacurici River Valley and Campo Formoso complexes.- 17.5.8 Mafic intrusive complexes of the Guiana Shield.- 17.6 Proterozoic dyke swarms and sills.- 17.6.1 Avanavero Suite.- 17.6.2 Mafic dyke swarms.- 17.7 Conclusions.- References.