Evolution of the lithospheric mantle in NE Angola: implications for diamond exploration

345 Pages·2017·14.45 MB·English

Evolution of the lithospheric mantle in NE Angola:
implications for diamond exploration

Montgarri Castillo i Oliver

ADVERTIMENT. La consulta d’aquesta tesi queda condicionada a l’acceptació de les següents condicions d'ús: La difusió
d’aquesta tesi per mitjà del servei TDX (www.tdx.cat) i a tra vés del Dipòsit Digital de la UB (diposit.ub.edu) ha estat
autoritzada pels titulars dels drets de propietat intel·lectual únicament per a usos privats emmarcats en activitats
d’investigació i docència. No s’autoritza la seva reproducció amb finalitats de lucre ni la seva difusió i posada a disposició
des d’un lloc aliè al servei TDX ni al Dipòsit Digital de la UB. No s’autoritza la presentació del seu contingut en una finestra
o marc aliè a TDX o al Dipòsit Digital de la UB (framing). Aque sta reserva de drets afecta tant al resum de presentació de
la tesi com als seus continguts. En la utilització o cita de parts de la tesi és obligat indicar el nom de la persona autora.

ADVERTENCIA. La consulta de esta tesis queda condicionada a la aceptación de las siguientes condiciones de uso: La
difusión de esta tesis por medio del servicio TDR (www.tdx.cat) y a través del Repositorio Digital de la UB
(diposit.ub.edu) ha sido autorizada por los titulares de los derechos de propiedad intelectual únicamente para usos
privados enmarcados en actividades de investigación y docencia. No se autoriza su reproducción con finalidades de lucro
ni su difusión y puesta a disposición desde un sitio ajeno al servicio TDR o al Repositorio Digital de la UB. No se autoriza
la presentación de su contenido en una ventana o marco ajeno a TDR o al Repositorio Digital de la UB (framing). Esta
reserva de derechos afecta tanto al resumen de presentación de la tesis como a sus contenidos. En la utilización o cita de
partes de la tesis es obligado indicar el nombre de la persona autora.

WARNING. On having consulted this thesis you’re accepting the following use conditions: Spreading this thesis by the
TDX (www.tdx.cat) service and by the UB Digital Repository (diposit.ub.edu) has been authorized by the titular of the
intellectual property rights only for private uses placed in investigation and teaching activities. Reproduction with lucrative
aims is not authorized nor its spreading and availability from a site foreign to the TDX service or to the UB Digital
Repository. Introducing its content in a window or frame foreign to the TDX service or to the UB Digital Repository is not
authorized (framing). Those rights affect to the presentation summary of the thesis as well as to its contents. In the using or
citation of parts of the thesis it’s obliged to indicate the name of the author.
Evolution of the lithospheric
mantle in NE Angola:
implications for diamond
exploration
BY
MONTGARRI CASTILLO I OLIVER
APPENDICES
TABLE OF CONTENTS: APPENDICES

CHAPTER 2. GEOLOGICAL SETTING
A2.1. General overview of the geology of Angola A2-1

CHAPTER 3. METHODOLOGY
A3.1. Sample catalogue A3-1
A3.2. Table of the standards used for EMP calibration A3-7
A3.3. Table of the major-element composition of the standards A3-8
A3.4. Tables of the trace-element composition of the NIST 610, NIST 612, PGEA and BCR
standards used in trace-element analysis of silicates, ilmenite, chromite and perovskite A3-12
A3.5. Table of the U-Pb analyses of the standards GJ-1, 91500 and Mud Tank zircons A3-38
A3.6. Table of the measured Sr-Nd ratios in the Ice River perovskite standard A3-41
A3.7. XRD diffractograms of the groundmass of the kimberlites A3-45

CHAPTER 4. PETROGRAPHY OF THE KIMBERLITES
A4.1. Tables of the major-element composition of minerals found in the studied
kimberlites (phlogopite, chromite, carbonate, serpentine, rutile) A4-1
A4.2. XR diffractograms of the kimberlite matrix A4-23

CHAPTER 5. AGE AND PETROGENESIS OF THE KIMBERLITES
A5.1. Table of major-element composition of perovskites of the Angolan kimberlites A5-1
A5.2. Table of trace-element composition of perovskites of the Angolan kimberlites A5-26
A5.3. Table of the U-Pb isotope data of perovskites of the Angolan kimberlites A5-32
A5.4. Table of the Sr-Nd isotope data of perovskites of the Angolan kimberlites A5-41

CHAPTER 6. PETROGRAPHY AND COMPOSITION OF THE MANTLE
XENOLITHS
A6.1. Detailed petrographic description of the studied xenoliths A6-1
A6.2. Table of the mineral major-element composition in the studied xenoliths A6-27
A6.3. Table of the mineral trace-element composition in the studied xenoliths A6-83
CHAPTER 7. STRUCTURE OF THE SCLM: A THEROMBAROMETRIC
APPROACH
A7.1. Modelling of the SCLM: calculation of the local geotherm A7-1
A7.2. Table of the major- and trace-element composition of the garnet xenocrysts A7-12

CHAPTER 9. EVOLUTION OF THE DIMs AND ITS APPLICATION TO
DIAMOND EXPLORATION
A9.1. Table of major-element composition of ilmenite A9-1
A9.2. Table of trace-element composition of ilmenite A9-45

PUBLICATION
Castillo-Oliver, M., Galí, S., Melgarejo, J.C., Griffin, W.L., Belousova, E., Pearson, N.J., Watangua, M.,
O’Reilly, S.Y., 2016. Trace-element geochemistry and U-Pb dating of perovskite in kimberlites of
the Lunda Norte province (NE Angola): petrogenetic and tectonic implications. Chem. Geol.
doi:10.1016/j.chemgeo.2015.12.014
CHAPTER 2.
GEOLOGICAL SETTING OF THE LUNDA
NORTE PROVINCE
APPENDIX
A2.1. General overview of the geology of Angola

APPENDIX 2.1. General overview of the geology of Angola
A general overview of the geology of Angola and its evolution is summarised in this document,
based on the information compiled by A.O. Gonçalves (2007). Therefore the reader is referred to his thesis
for an exhaustive description of the Angolan geology and the corresponding.

Four Archaean shields or blocks have been identified within Angola: Maiombe, Angolan, Kasai
and Bangweulo. Each one is defined by a characteristic stratigraphic sequence and was differently
affected by the magmatic, metamorphic and deformation events linked to the Precambrian orogenies.
As a consequence, the lithology of the Precambrian basement is complex and diverse around Angola
(table A2.1a). In general terms, the crystalline Archean basement is usually divided into the Upper
Group, composed of gneiss, plagiogneiss, quartzites and amphibolites; and the Lower Group,
characterised by lower grade of metamorphism. During the extensional Limpopo-Liberian cycle (2700
± 200 Ma), sedimentary rocks of different origin were deposited in the basins of the four main Angolan
shields. All these rocks are nowadays totally metamorphised as a consequence of the subsequent
orogenies and they occur as metaschists, metabasites, quartzites, marbles and metagreywackes.
The Eburnean cycle (2-2.2 Ga) is characterised by a more complex lithology than the
underlying series (table A2.1b). On one side it includes the “troughs” facies, or greenstone belts,
composed of thick vulcanosedimentary series developed within the tectonic depressions and only
affected by a low grade metamorphism (green schist facies). These belts are divided into two main units
(Lulumba and Uonde Groups) and its formation is thought to be a consequence of a collision-
subduction process between the Eburnean Craton (2000Ma) and the older Chaillu (2500Ma) and Cassai
(2700Ma) cratons (Bellutini et al., 1983). At the same time, thinner layers of terrigenous rocks were
deposited in the regional folds. The stratigraphic sequence varies in each Archean block, but it can
roughly be defined by an interbedding of conglomerate, sandstone, limestone, phyllite, schist and
quartzite layers, differing in thickness. Associated with the Eburnean orogeny, several magmatic
episodes took place, leading to the intrusion of the Quibala granites, the Matala red granites, porhpyritc
granites, volcanic and subvolcanic rocks and dolerites.
Throughout the Kibaran cycle (1.4-1 Ga), the Congo craton boundary was importantly affected
by extensional processes, leading to the development of thick sedimentary (carbonate and clastic) layers
in the West Congo alaucogen. In the other areas, this extension was responsible for the intrusion of
A2-1
A2.1. General overview of the geology of Angola

basic and ultrabasic magmas. Among these, it is worth mentioning the formation of the Cunene
complex in the southern part of the Angolan shield. In this anorthositic complex, the largest one in the
world of its kind (15000 km2), at least 5 kimberlitic intrusions have been described. These Proterozoic
chimneys would explain the occurrence of alluvial diamonds in the southern Angolan rivers.
Interestingly, the diamonds found in this area clearly differ in colour, purity, size and morphology from
the ones found in north-eastern Angola (Gonçalves, 2007).
During the Panafrican Orogeny (῀590 My), Western Gondwana was formed as a consequence
of the collision of the Congo and Brasil cratons (Alkmim et al., 2006). In the West Congo alaucogen,
the sedimentary sequence corresponding to the Panafrican cycle is divided into three main series (ie.
Terreiro, Alto Chiloango and Schist-carbonated Groups) as described in table A2.1c.
The Phanerozoic cover is composed of subhorizontal, little deformed and non-metamorphised
sedimentary rocks of platform origin (table A2.1d). During the Gondwana breakup (190-60 Ma) thick
and large sedimentary levels were deposited in the basins created as a result of this extension. (i.e. Karroo
Fm). Also as a consequence of the Atlantic opening, oceanic margin basins started to develop, resulting
in the formation of the Angolan Perioceanic Depression in the Jurassic, accompanied by a progressive
deposition of marine sedimentary series. In the continent, this extensional regime triggered the
development of the Lucapa corridor, as well as important basic and ultrabasic intraplate magmatic
episodes within this rift. Not surprisingly, most of the alkaline, kimberlitic and carbonatitic intrusions
found in Angola are known to be Cretaceous based both on stratigraphic evidences and isotope studies.
Discordantly overlying these intrusions and the previously deposited materials are the Calonda
Formation (Aptian-Albian) and the Kalahari Group (Paleogene-Neogene). They constitute the largest
sedimentary cover in Angola and are mainly composed of polymictic conglomerates, sandstones and
mudstones of continental origin.
A2-2
A2.1. General overview of the geology of Angola

Table A2.1a. Stratigraphy and tectonomagmatic activity in the different craton shields in Angola during the Archean cycles (2700 - >3000 Ma)

A2-3
A2.1. General overview of the geology of Angola

Table A2.1b. Stratigraphy and tectonomagmatic activity in the different craton shields and greenstone belts in Angola
during the Eburnean cycle (2000 - 2200 Ma)

A2-4
A2.1. General overview of the geology of Angola

Table A2.1c. Stratigraphy and tectonomagmatic activity in Angola during the Kibarian (1000 - 1400 Ma) and the Panafrican (῀580Ma) orogenic cycles.

A2-5