The Mavuradonha layered complex [Elektronische Ressource] : neoproterozoic emplacement and Pan-African granulite facies metamorphism in the Zambezi Allochthonous Terrane of the Mt. Darwin Area, Zambezi belt, NE-Zimbabwe / Mario Müller

Mam

Informations

• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2004
• Nombre de lectures: 29
• Langue: English
• Poids de l'ouvrage: 24 Mo

Extrait

The Mavuradonha Layered Complex:
Neoproterozoic emplacement and
Pan-African granulite-facies metamorphism in the
Zambezi Allochthonous Terrane of the Mt. Darwin Area,
Zambezi belt, NE-Zimbabwe








Dissertation
zur Erlangung des Grades
„Doktor der Naturwissenschaften“
am Fachbereich für Geowissenschaften
der Johannes Gutenberg-Universität in Mainz






Mario Müller
geboren in Speyer am Rhein

Mainz 2004
























Tag der mündlichen Prüfung: 07.05.2004























All views and results presented in this thesis are those of the author, unless stated
otherwise.


Ich versichere, dass ich die vorliegende Arbeit selbständig und nur unter Verwendung der
angegebenen Quellen und Hilfsmittel verfasst habe.



Mühlhausen, den 30. Januar 2004 And I think to myself, what a wonderful world ....
L. ArmstrongTable of contents

Acknowledgements .......................................................................................................... I
Abstract .........................................................................................................................III
ZusammenfassungV
1 Introduction .......................................................................................................1
1.1 Geological evolution of Gondwana ............................................................................... 1
1.2 The Zambezi belt ........................................................................................................... 2
1.2.1 General geology............................................................................................................. 2
1.2.2 The Zambezi belt in NE-Zimbabwe .............................................................................. 6
1.3 Previous work ................................................................................................................ 9
1.4 Aim of this thesis ......................................................................................................... 10
2 Geology of the study areas12
2.1 Geology of the Mavuradonha Mountain range............................................................ 12
2.2 of the inlier.................................................................................................... 25
2.2.1 Nyamhanda Inlier ........................................................................................................ 25
2.2.2 Chimwaya Hill Inlier ................................................................................................... 27
3 Analytical methods..........................................................................................29
4 Petrology and metamorphic evolution ..........................................................36
4.1 Petrography - mineral assemblages and textures ......................................................... 36
4.1.1 Mavuradonha Layered Complex ................................................................................. 36
4.1.1.1 Serpentinite.................................................................................................................. 37
4.1.1.2 Metapyroxenites .......................................................................................................... 37
4.1.1.3 Amphibolites................................................................................................................ 38
4.1.1.3.1 Garnet-bearing amphibolites........................................................................................ 38
4.1.1.3.2 Garnet-free amphibolites ............................................................................................. 38
4.1.1.4 Fine-grained metagabbros............................................................................................ 39
4.1.1.5 Coarse-grained metagabbros 39
4.1.1.6 Garnet-bearing metagabbros 40
4.1.1.7 Leuco-metagabbros and leuco-amphibolites ............................................................... 40
4.1.1.8 Meta-anorthosites ........................................................................................................ 41
4.1.1.9 Pegmatites.................................................................................................................... 41
4.1.2 Nyamhanda Inlier and Chimwaya Hill Inlier 45
4.1.2.1 Amphibolites................................................................................................................ 45
4.1.2.1.1 Garnet-bearing amphibolites........................................................................................ 45
4.1.2.1.2 Garnet-free amphibolites ............................................................................................. 46
4.1.2.2 Metagabbros 46
4.1.2.2.1 Chimwaya Hill Inlier ................................................................................................... 46
4.1.2.2.2 Nyamhanda Inlier ........................................................................................................ 47 4.1.3 Ocellar Gneiss.............................................................................................................. 53
4.2 Mineral chemistry of samples from the Mavuradonha Layered Complex .................. 53
4.2.1 Garnet ..........................................................................................................................54
4.2.2 Pyroxene ...................................................................................................................... 60
4.2.2.1 Clinopyroxene 60
4.2.2.2 Orthopyroxene ............................................................................................................. 62
4.2.2.3 Pigeonite 62
4.2.3 Plagioclase ................................................................................................................... 63
4.2.4 Amphibole 64
4.2.5 Scapolite 65
4.3 PT evolution of the Mavuradonha Layered Complex.................................................. 65
4.3.1 Granulite-facies PT conditions .................................................................................... 65
4.3.2 Retrograde PT evolution.............................................................................................. 71
4.3.3 PT conditions calculated using TWQ .......................................................................... 72
4.4 Summary and interpretation of textures and PT-evolution of the Mavuradonha
Layered Complex......................................................................................................... 75
5 Geochemistry ...................................................................................................78
5.1 Classification of the metagabbros................................................................................ 80
5.2 Major and trace element variations.............................................................................. 81
5.2.1 Mavuradonha Layered Complex ................................................................................. 81
5.2.2 Nyamhanda Inlier and Chimwaya Hill Inlier............................................................... 86
5.3 TiO , LIL and HFS element correlations..................................................................... 90 2
5.4 Summary and interpretation......................................................................................... 90
5.4.1 Mavuradonha Layered Complex 90
5.4.2 Nyamhanda Inlier and Chimwaya Hill Inlier 93
6 Geochronology and zircon-cathodoluminescence ........................................97
6.1 Cathodoluminescence imaging .................................................................................... 97
6.2 Zircon U-Pb and Pb-Pb geochronology....................................................................... 99
6.2.1 Mavuradonha Layered Complex ................................................................................. 99
6.2.1.1 Metagabbro sample ZZB 123 ...................................................................................... 99
6.2.1.2 Ferro-metagabbro sample ZZB 166........................................................................... 106
6.2.1.3 Summary of age interpretation for zircons from the Mavuradonha Layered
Complex..................................................................................................................... 107
6.2.2 Pegmatites within the Mavuradonha Layered Complex............................................ 109
6.2.2.1 ZZB 60: pegmatite, northern Mavuradonha Mountains 109
6.2.2.2 ZZB 128: pegmatite, south of the Mavuradonha Mts................................................ 109
6.2.2.3 Interpretation.............................................................................................................. 112
6.2.3 Ocellar Gneiss............................................................................................................ 112
6.2.3.1 ZIM 30 (Fig. 6-9 a & b; Fig. 6-10 a) ........................................