Unraveling the record of successive high grade events in the Central Zone of the Limpopo Belt using Pb single phase dating of metamorphic minerals

被引:171
作者
Holzer, L
Frei, R
Barton, JM
Kramers, JD
机构
[1] Univ Bern, Min Pet Inst, Grp Isotopengeol, CH-3012 Bern, Switzerland
[2] Rand Afrikaans Univ, Dept Geol, ZA-2006 Johannesburg, South Africa
关键词
Archean; geochronology; granulite facies; Limpopo Belt; Palaeoproterozoic; Pb isotopes; polymetamorphic;
D O I
10.1016/S0301-9268(97)00058-2
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
Dating of relic metamorphic assemblages can provide important information about the timing and character (metamorphic grade and/or PT-evolution) of early high grade episodes in polymetamorphic provinces. Using Pb stepwise leaching of metamorphic silicates, we have dated multiple granulite facies metamorphic episodes in the Central Zone (CZ) of the Limpopo Belt. Ages of 2.52 Ga were obtained from sillimanite and cogenetic garnet and ages of about 2.01 Ga from titanite, garnet and clinopyroxene. Together with new and published conventional age data fi om accessory phases and in the context of combined petrological and structural data, these results lead us to a reinterpretation of the tectono-metamorphic history of the CZ. Three distinct high grade events at about 3.2-3.1 Ga, 2.65-2.52 Ga and 2.0 +/- 0.05 Ga are recognized. Each of these is suggested to correspond to a tectonic episode of distinct character: (a) for the 3.2 Ga event magmatic activity can mainly be identified (best represented, for example, by the Sand River Gneisses or the Messina Layered Intrusion), The field relationships concerning the tectono-metamorphic history of this Early-Archean event are largely erased by al least two high grade metamorphic overprints. (b) Late-Archean (similar to 2.6-2.52 Ga) low pressure granulite facies metamorphism was associated with voluminous granitic and charnockitic plutonism. The anticlockwise P-T evolution of these granulites probably reflects deep crustal processes, associated with magmatic underplating (or in-plating), contemporaneous with vertical crustal growth of the Zimbabwe craton around 2.6 Ga. (c) During the Proterozoic event (similar to 2.05-1.95 Ga) tectonic thickening was caused by the collision of the Kaapvaal and Zimbabwe cratons. The CZ was squeezed between these two cratons and as a consequence underwent high pressure granulite facies metamorphism with a clockwise P-T evolution. The structural, metamorphic and geochronological data can be best explained with a tectonic model that describes this final event as a dextral transpressive orogeny. (C) 1998 Elsevier Science B.V.
引用
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页码:87 / 115
页数:29
相关论文
共 66 条
[1]  
BAHNEMANN KP, 1972, THESIS PRETORIA
[2]  
Barker O B., 1983, Spec. Publ. geol. Soc. S. Afr, V8, P181
[3]  
Barton J.M., 1983, SPEC PUBL GEOL SOC S, V8, P19
[4]   ISOTOPIC AND REE CHARACTERISTICS OF THE INTRUSIVE CHARNOENDERBITE AND ENDERBITE GEOGRAPHICALLY ASSOCIATED WITH THE MATOK PLUTON, LIMPOPO BELT, SOUTHERN AFRICA [J].
BARTON, JM ;
DOIG, R ;
SMITH, CB ;
BOHLENDER, F ;
VANREENEN, DD .
PRECAMBRIAN RESEARCH, 1992, 55 (1-4) :451-467
[5]   THE SIGNIFICANCE OF RB-SR AGES OF BIOTITE AND PHLOGOPITE FOR THE THERMAL HISTORY OF THE CENTRAL AND SOUTHERN MARGINAL ZONES OF THE LIMPOPO BELT OF SOUTHERN AFRICA AND THE ADJACENT PORTIONS OF THE KAAPVAAL CRATON [J].
BARTON, JM ;
VANREENEN, DD .
PRECAMBRIAN RESEARCH, 1992, 55 (1-4) :17-31
[6]   Petrography age and origin of the Schiel alkaline complex, northern Transvaal, South Africa [J].
Barton, JM ;
Barton, ES ;
Smith, CB .
JOURNAL OF AFRICAN EARTH SCIENCES, 1996, 22 (02) :133-145
[7]   THE SIGNIFICANCE OF 3000-MA GRANULITE-FACIES MAFIC DIKES IN THE CENTRAL ZONE OF THE LIMPOPO BELT, SOUTHERN AFRICA [J].
BARTON, JM ;
VANREENEN, DD ;
ROERING, C .
PRECAMBRIAN RESEARCH, 1990, 48 (03) :299-308
[8]   The Messina Layered Intrusion, Limpopo Belt, South Africa: An example of in-situ contamination of an Archean anorthosite complex by continental crust [J].
Barton, JM .
PRECAMBRIAN RESEARCH, 1996, 78 (1-3) :139-150
[9]   GEOLOGY, AGE, AND TECTONIC SETTING OF THE MESSINA LAYERED INTRUSION,LIMPOPO MOBILE BELT, SOUTHERN-AFRICA [J].
BARTON, JM ;
FRIPP, REP ;
HORROCKS, P ;
MCLEAN, N .
AMERICAN JOURNAL OF SCIENCE, 1979, 279 (10) :1108-1134
[10]  
BARTON JM, 1994, GEOLOGY, V22, P1035, DOI 10.1130/0091-7613(1994)022<1035:DMEITL>2.3.CO