The Mavuradonha Layered Complex: Neoproterozoic ... - ArchiMeD

More documents

Recommendations

Info

2 Geology of the study areas 26 2 Legend Fig. 2-2. Geology of the Nyamhanda Inlier (1) and the Chimwaya Hill Inlier (2) (modified after Bache et al. 1983). 1 Ruya Granitic Gneiss Wadze Gneiss Chironga Gneiss Ocellar Gneiss Amphibolite Metagabbro/metanorite corona-textured metagabbro/ olivin-metagabbro fault 0 5 km 1 : 100 000
2 Geology of the study areas 27 Two smaller gabbroic bodies are exposed in the NE and SE and form distinct hills. The metagabbro in the NE is surrounded by amphibolites, whereas gneisses enclose the metagabbro in the SE. Amphibolites occur as both garnet-free and garnet-bearing varieties. Some of the amphibolites are enriched in plagioclase, whereas other types are mafic, hornblende-rich varieties. The latter are interpreted to be of metamorphic origin. The amphibolites are always in contact with the underlying gneisses. Intrusive relationships between the gneisses and the metagabbroic rocks were not observed. The metagabbro/amphibolite associations in the Nyamhanda Inlier form NW trending ridges. This trend is also observed in the gneisses and probably marks the orientation of the fold axes. The observed layering and foliation in the amphibolites and the gneisses are tilted to the W and E, depending on the occurrence in the fold limbs, with a predominant dip of 60°-80°. This foliation most likely represents the first deformation event in these rocks of the Nyamhanda Inlier. In the gneisses a lineation is developed in addition to the foliation, which plunges 65° to the SE. The second deformational event marks the folding of the gabbroic rocks and the gneisses. A further folding and refolding of pre-existing folds is observed in the gneisses. High-grade shearzones showing ductile deformation are a common feature in the inlier. These shearzones are assumed to be the result of the third deformation event because all units are affected by these shearzones. 2.2.2 Chimwaya Hill Inlier A small metagabbro (Fig. 2-2) crops out at Chimwaya Hill (1296 m), which is located in the Mavuradonha Mountain range. The Chimwaya Hill Inlier shows the same field appearances as the metagabbros in the Mavuradonha Layered Complex and Nyamhanda Inlier. The contact between gneisses at the base and the metagabbros is marked by amphibolites. Intrusive relationships between the gneisses and the mafic complex are not preserved. Metagabbros and amphibolites display an inherited igneous layering, grading from fine-grained dark coloured to coarse-grained leucocratic varieties. Two types of gneisses are exposed surrounding the metagabbros. The migmatitic Chironga Gneiss, also exposed in the Nyamhanda Inlier, occurs in direct neighbourhood to the metagabbroic rocks, but the contact is not exposed. The second gneiss is the muscovite-bearing and garnet-rich Wadze Gneiss, which is exposed in the outer part of this inlier. Characteristic for this gneiss is the formation of a deep depression due to intense shearing and weathering. Shearing is marked by the formation of a distinct foliation and elongated clinopyroxenes in the metagabbros. The foliation dips around 60° to the NE. These sheared metagabbros are
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 and 18: 1 Introduction 3 1993). In the West
Page 19 and 20: 1 Introduction 5 Moreover, the stru
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: 2 Geology of the study areas 25 def
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
Page 57 and 58: Am II-1 II-2 Pl II-3 Grt Pl Cpx Cpx
Page 63 and 64: Plate III 49 Plate III-8: Corona te
Page 65 and 66: Pl III-4 Am III-5 III-6 Am Pl Am Op
Page 91 and 92:
4 Petrology and metamorphic evoluti
Page 93 and 94:
5 Geochemistry 79 a) Gabbro / Norit
Page 95 and 96:
5 Geochemistry 81 Chimwaya Hill Inl
Page 97 and 98:
31 28 25 22 19 16 13 10 2.5 1.6 1.4
Page 99 and 100:
5 Geochemistry 85 25 20 15 10 5 Ga
Page 101 and 102:
5 Geochemistry 87 The trace element
Page 103 and 104:
5 Geochemistry 89 1000 900 800 700
Page 105 and 106:
5 Geochemistry 91 600 500 400 300 2
Page 107 and 108:
5 Geochemistry 93 proposed for gabb
Page 109 and 110:
5 Geochemistry 95 1000 900 800 700
Page 111 and 112:
6 Geochronology and zircon-cathodol
Page 113:
Page 116 and 117:
6 Geochronology and zircon cathodol
Page 120 and 121:
Page 122 and 123:
Page 125 and 126:
6 Geochronology and zircon cathodol
Page 127:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
7 Sm-Nd, Rb-Sr and Pb-Pb isotopic s
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
8 Petrogenetic and geotectonic impl
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
9 Interpretation in the regional co
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
References 164 References ARANOVICH
Page 180 and 181:
References 166 COMPSTON, W., WILLIA
Page 182 and 183:
References 168 GRAHAM, C.M. and POW
Page 184 and 185:
References 170 JOHN, T., SCHENK, V.
Page 186 and 187:
References 172 KROGH RAVNA, E. (200
Page 188 and 189:
References 174 MEZGER, K., HANSON,
Page 190 and 191:
References 176 POLLER, U. (1999): A
Page 192 and 193:
References 178 TEERTSTRA, D.K. and
Page 194 and 195:
Appendix 180 Appendix A-I Geology o
Page 196 and 197:
Appendix A-I. Geology of the study
Page 198 and 199:
Appendix A-I. Geology of the study
Page 200 and 201:
Appendix A-II. Analytical methods v
Page 202 and 203:
Appendix A-II. Analytical methods v
Page 204 and 205:
Appendix A-III. Petrology and metam
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
Page 220 and 221:
Page 222 and 223:
Page 224 and 225:
Appendix A-III. Petrography and met
Page 226 and 227:
Page 228 and 229:
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Appendix A-IV. Geochemistry xlviii
Page 244 and 245:
Appendix A-IV. Geochemistry l Table
Page 246 and 247:
Appendix A-IV. Geochemistry lii Tab
Page 248 and 249:
Appendix A-IV. Geochemistry liv Tab
Page 250 and 251:
Appendix A-IV. Geochemistry lvi Tab
Page 252 and 253:
Appendix A-IV. Geochemistry lviii T
Page 254 and 255:
Appendix A-V. Geochronology and cat
Page 256 and 257:
Page 258 and 259:
Page 260 and 261:
Page 262 and 263:
Appendix A-VI. Sm-Nd, Rb-Sr and Pb-
Page 264 and 265:
Appendix A-VI. Sm-Nd, Rb-Sr and Pb-
Page 266:
Curriculum vitae 181 Curriculum Vit
show all

The Mavuradonha Layered Complex: Neoproterozoic ... - ArchiMeD

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?