The Mavuradonha Layered Complex: Neoproterozoic ... - ArchiMeD

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1 Introduction 4 100 00 km Lusaka MD CI MMC MMC Mt. Darwin UK Great Dyke UG Harare Legend Chewore Inlier CI granite cover Makuti metamorphic complex MMC supracrustal rocks Mesoproterozoic Urungwe klippe UK Zambezi belt (and adjacent parts of the Mocambique belt) Zambezi Allochthonous Terrane Paleoproterozoic Umkondo Group UG reworked basement Archean craton Mwembeshi Dislocation MD Fig. 1-2. The Zambezi belt of Zimbabwe and Zambia; modified after Hanson et al. (1994).
1 Introduction 5 Moreover, the structural trends of the Irumide belt rather support the interpretation that the Zambezi belt evolved during the closure of an intracontinental basin (Hanson et al., 1988b; Hanson, 2003; Kröner, 1977b; 1983) than by closure of a wide ocean, since similar structures can be found on both sides of the Zambezi belt. In addition, the Zambezi belt contains extensive tracts of remobilised sialic basement which are structurally overlain by large masses of supracrustal rocks (Leitner & Phaup, 1974; Wilson et al., 1993; Hanson et al., 1993). However, it should be considered that the direct correlation between Irumide belt and Choma-Kalomo block was recently discounted on the basis of new SHRIMP zircon ages that indicate different histories of these older terranes (DeWaele et al., 2003). The Mwembeshi dislocation, often described as a major shear zone, did not have much influence on the formation of the transcontinental mobile belt (Katongo & Tembo, 1999; Porada & Berhorst, 2000). Moreover, the Mwembeshi dislocation is interpreted as a remobilised shear-zone predating the Pan-African orogeny. These arguments led to the suggestion that the Zambezi belt evolved as a narrow intracratonic basin which was filled with shallow-water sediments and bimodal volcanic rocks (Wilson et al., 1993, Munyanyiwa et al., 1997). These bimodal volcanic rocks (Leitner & Phaup, 1974; Wilson et al., 1993; Hanson et al., 1993; Munyanyiwa et al., 1997) reflect initial extension-related magmatism. Daly (1986) proposed a linked array of different aulacogens, pull-apart basins and shallow oceanic basins for the development of the Zambezi belt. These basins were closed at different times in the Neoproterozoic. As described in Porada & Berhorst (2000) several small-scale basins evolved into larger basins on the western flank of Rodinia, partly with an oceanic character as formed in the Lufilian Arc and partly remaining as intracratonic basins as in the Zambezi belt and in the Damara belt. Because of the presence of ophiolites, eclogites and other high-pressure rocks, the model suggesting a Red Sea type setting is another possible explanation for the Pan- African geotectonic setting in southern Africa (Porada, 1989). In this model, two rifts evolved into an ocean, whereas the third branch remained as an intracratonic failed rift. This failed rift may be represented in the eastern part of the Zambezi belt in Zimbabwe, whereas in the Zambezi belt of Zambia, the Lufilian Arc and the Damara belt the rifts evolved into oceans. Dirks et al. (1998) suggested a model for the evolution of the Zambezi belt, comprising two major tectono-thermal events based on structural analysis in NE- Zimbabwe. In their interpretation an extensional event occurred between 900 and 800 Ma, accompanied by extension-related magmatism. More than 300 Ma later compressional tectonics led to the formation of the Pan-African Zambezi belt at around 500 Ma. These two major events are corroborated by recently available age data (Hahn et al., 1991; Goscombe et al., 1997; 2000; Vinyu et al., 1997; 1999).
Page 1 and 2: The Mavuradonha Layered Complex: Ne
Page 3 and 4: All views and results presented in
Page 5 and 6: Table of contents Acknowledgements
Page 7 and 8: 6.2.3.4 Summary and interpretation
Page 9 and 10: This project was part of the Mainz-
Page 11 and 12: utile ages ranging from 526 ± 7 to
Page 13 and 14: Alter von 899 ± 46 Ma untermauert.
Page 15 and 16: 1 Introduction 1 1 Introduction 1.1
Page 17: 1 Introduction 3 1993). In the West
Page 21 and 22: 1 Introduction 7 Zambezi Belt Mount
Page 23 and 24: 1 Introduction 9 metamorphosed unde
Page 25 and 26: 1 Introduction 11 on minerals with
Page 27 and 28: 2 Geology of the study areas 13 Zam
Page 29 and 30: 2 Geology of the study areas 15 The
Page 31 and 32: Plate I Plate I-1: View at the land
Page 33 and 34: Plate I Plate I-3: Layering in the
Page 35 and 36: Plate I Plate I-5: Compositional la
Page 37 and 38: Plate I Plate I-7: Shearzone within
Page 39 and 40: 2 Geology of the study areas 25 def
Page 41 and 42: 2 Geology of the study areas 27 Two
Page 43 and 44: 3 Analytical methods 29 3 Analytica
Page 45 and 46: 3 Analytical methods 31 Mineral sep
Page 47 and 48: 3 Analytical methods 33 U-Pb rutile
Page 49 and 50: 3 Analytical methods 35 microscopic
Page 51 and 52: 4 Petrology and metamorphic evoluti
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4 Petrology and metamorphic evoluti
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5 Geochemistry 79 a) Gabbro / Norit
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5 Geochemistry 81 Chimwaya Hill Inl
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31 28 25 22 19 16 13 10 2.5 1.6 1.4
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5 Geochemistry 85 25 20 15 10 5 Ga
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5 Geochemistry 87 The trace element
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5 Geochemistry 89 1000 900 800 700
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5 Geochemistry 91 600 500 400 300 2
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5 Geochemistry 93 proposed for gabb
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5 Geochemistry 95 1000 900 800 700
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6 Geochronology and zircon-cathodol
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6 Geochronology and zircon cathodol
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6 Geochronology and zircon cathodol
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7 Sm-Nd, Rb-Sr and Pb-Pb isotopic s
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8 Petrogenetic and geotectonic impl
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9 Interpretation in the regional co
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References 164 References ARANOVICH
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References 166 COMPSTON, W., WILLIA
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References 168 GRAHAM, C.M. and POW
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References 170 JOHN, T., SCHENK, V.
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References 172 KROGH RAVNA, E. (200
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References 174 MEZGER, K., HANSON,
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References 176 POLLER, U. (1999): A
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References 178 TEERTSTRA, D.K. and
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Appendix 180 Appendix A-I Geology o
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Appendix A-I. Geology of the study
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Appendix A-I. Geology of the study
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Appendix A-II. Analytical methods v
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Appendix A-II. Analytical methods v
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Appendix A-III. Petrology and metam
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Appendix A-III. Petrography and met
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Appendix A-IV. Geochemistry xlviii
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Appendix A-IV. Geochemistry l Table
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Appendix A-IV. Geochemistry lii Tab
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Appendix A-IV. Geochemistry liv Tab
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Appendix A-IV. Geochemistry lvi Tab
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Appendix A-IV. Geochemistry lviii T
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Appendix A-V. Geochronology and cat
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Appendix A-VI. Sm-Nd, Rb-Sr and Pb-
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Appendix A-VI. Sm-Nd, Rb-Sr and Pb-
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Curriculum vitae 181 Curriculum Vit
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