Alkaline Igneous Rocks and potential Critical Metal deposits in Angola
Workshop and fieldtrip, September 2019
In September, the St Andrews team took part in a workshop and fieldcourse in Angola, hosted by the Universidade Agostinho Neto (UAN) in Luanda. The purpose of our trip was to outreach our work on alkaline igneous rocks and to learn more about similar rocks found in Angola. Our visit started with a day workshop on frontiers in the study of alkaline silicate rocks and carbonatites, which included presentations by Prof Adrian Finch and myself (University of St Andrews) and by Pete Siegfried of GeoAfrica Consultants (based in Namibia). GeoAfrica and St Andrews are both partners within the HiTech AlkCarb consortium, funded by the European Union. Our visit was funded by the SFC ODA Global Challenges Research Fund as the first step in assessing opportunities for future collaborations between Angola and St Andrews for sustainable development of their mineral resources. The workshop was hosted by the Universidade Agostinho Neto at their campus in central Luanda on the Avenida Marginale, and was followed by 5 days of fieldwork in an underexplored nepheline syenite complex (Nejoio) in the remote northern part of the Namibe province.
- 12 Sep 2019 Alkaline Igneous Magmatism workshop at UAN in Luanda
- 15-20 Sep 2019 Fieldcourse in the Nejoio complex, Namibe Province, Southern Angola
The workshop in Luanda was attended by about 60 geologists working in Angola, including representatives from the University, the Angolan Oil company Sonangol, recent Angolan graduates and many of the geology, geophysics and engineering students from the Agostinho Neto University. At the workshop we presented scientific work on magmatic roof zones (Adrian), mineralisation processes in peralkaline systems in Greenland (myself), and on carbonatites in Namibia and South Africa (Pete Siegfried, GeoAfrica Prospecting Services).
Faculty of Sciences, Universidade Agostinho Neto, Marginale Luanda
Students of UAN showing us around the geological museum in Luanda
Adrian speaking at Agostinho Neto
Bay of Luanda
Fieldtrip Nejoio complex, South Angola
The workshop in Luanda was followed by a 5 day fieldtrip looking at peralkaline igneous rocks at the Nejoio complex in Southern Angola. We were based in the town of Camacuio in Namibe Province, roughly 6 hours north of Lubango, and at a c. 3.5 hour drive from the field site which lies on the land of the Muhumbi people. This visit was an opportunity for us to learn more about working in Angola and also to assist the Angolan geologists with the interpretation of their geology using our experience of similar rocks from Greenland, Brazil and Namibia. The group included Finch, Borst and Siegfried accompanied by Professor Aurora Bambi of the Universidade Agonstinho Neto in Luanda. The course was also attended by two recent geology graduates from St Andrews (Geraldine Tchimbali and Antonia dos Santos) and four current geology students from the Agostinho Neto University (Andre Eugenio, Egidio Lopes, Elizabeth Faria and Sergio Azevedo) who will use the field course as part of their undergraduate dissertations.
Local guides (and St Andrews graduate Geraldine) leading the way to Nejoio, viewed from the South
It was a pleasure and a privilege for us to work alongside the geologists from the Agostinho Neto University in Luanda, allowing us insights into the complex and fascinating geology of Angola, and allowing Angolan geologists access to the expertise we have acquired from rocks elsewhere in the world. A key objective of the project was to place Angolan geology within the broader regional context of South West Africa (i.e. South Africa, Namibia, Angola).
Some of the students and our guides on the Nejoio complex. Looking northeast, the large peralkaline Lutala complex (Sierra de Neve) can be seen in the background
View from one the highest points on Nejoio’s outer ring
Complex crosscutting and deformation relationships at the margin of the intrusion
Beautiful scenery on the road from Lubango to Camucuio in the Namibe province
Meeting Soba Nangolo, chief of the Muhumbi people
Looking at crystal alignment in sodalite syenites of the Nejoio alkaline complex, Angola
Laminated sodalite feldspar syenite
Our local guides leading the way
Nejoio is spelled in different ways, including N’DJOIO, NANDJOIO AND NEDJOIO, following attempts to translate locality names in the Kimbundu language into Portuguese. We have used Nejoio to be consistent with existing scientific literature by Rodrigues et al.
Research on Nejoio was carried out thanks to kind permission of Soba (Chief) Nangolo of the Muhumbi People on whose land the complex lies.
The fieldwork and attendance by BORST and FINCH were sponsored by the SFC ODA GLOBAL CHALLENGES RESEARCH FUND.
The attendance of Peter Siegfried was supported by the HITECH ALKCARB project, funded through the European Union h+Horizon 2010 Research and Innovation Programme (#689909)
Brazillian Rare Earth symposium – University of São Paulo
On 6 to 10 November 2017, the St Andrews team (Nicky Horsburgh, Adrian Finch and myself) attended the Brazilian SOS RARE symposium on Rare Earth Elements, held at the Institute of Geosciences, University of São Paulo. The symposium was organized by Prof. Daniel Atencio and Prof. Marcello Andrade (University of São Paulo) and comprised a series of invited talks followed by field excursions to famous Brazilian carbonatite and peralkaline localities.
Prof. Marcello Andrade kicked off the meeting with a presentation on Raman spectroscopy to fingerprint REE minerals. Dr Andrezza de Almeida Azzi (USP) introduced us to the fascinating geology and mineralogy of the Poços de Caldas alkaline complex. She catalogued many REE minerals from old sample collections of former Poços de Caldas mining sites, many of which are not properly documented to date. Prof. Daniel Atencio gave us a preview of the bewildering mineralogy of the Araxa and Jacupiranga carbonatites.
After lunch and an enjoyable visit to the local mineral museum, Prof. Hermi Felinto de Brito from the Institute of Chemistry (USP) talked about the luminescent properties of RE3+ compounds and the synthesis of persistent luminescent Eu, Tb and Tm materials which can luminesce up to 24 hours after being excited, offering many applications in for example traffic and emergency signalization. Prof. Brito also demonstrated how they synthesize RE3+compounds at high temperature using just a simple microwave oven.
Prof. Henrique Kahn of the Mining & Engineering department of the LCT-Polytechnic School (USP) presented work on metallurgical processing and mineralogical characterization of REE-rich lateritic soils from various Brazilian carbonatite localities. The last three talks were given by us from St Andrews. Prof. Adrian Finch spoke about REE and HFSE mineralisation in magmatic roof zones and applications of luminescence studies to understand hydrothermal alteration and mineralization processes. I presented on the pseudomorphic replacement of eudialyte in the Ilímaussaq complex, including new evidence for late-magmatic REE-HFSE remobilisation from trace element and Sm/Nd isotopic data of microdrilled pseudomorphs (work by my MSc student Mathijs vd Ven). Nicky Horsburgh gave the last talk, on luminescence studies of REE minerals. Nicky demonstrated that mineral luminescence is strongly provenance dependent, illustrating the need for site-specific luminescence studies if we are to apply luminescence as an automated sorting or core logging tool.
Keen to bring out our geological hammers, we ventured north of São Paulo on day two to see some rocks in the field. After a long bus journey, enjoying the luscious green scenery, we arrived at an amazing lujavrite outcrop in the northern part of the Poços de Caldas alkaline complex. This is one of the few places with good solid rock exposures, not obscured by the thick tropical weathering profile that covers much of the complex. The coarse grained lujavrite shows strong magmatic foliation fabrics defined by coarse feldspar laths wrapped in fine needles of aegirine (photo), which is a testament of the low viscosity melt and possibly subsolidus deformation and recrystallisation. The rock is peppered with large (5–6 cm) purple to pink eudialyte which overgrow the foliation fabric, resembling textures seen in the naujaite of the Ilímaussaq complex. We managed to collect a number of samples for further mineralogical studies and comparison to Greenland samples.
St Andrews Team: Nicky, Adrian, Me
Araxa, a lateritised carbonatite and the worlds largest Nb mine
Villiaumite (NaF) – a water soluble agpaitic mineral and yellow Hainite-(Y)
Large poikilitic eudialyte in nepheline syenites from Pocos de Caldas, Brazil
My current position is funded by the SoS RARE consortium, which has now entered its third and final year.
SoS RARE is a consortium project funded by NERC and EPSRC under the Security of Supply of Mineral Resources (SoS Minerals) science programme, running from 2015 to 2019. The research team includes 17 investigators from six UK universities and research institutes (Camborne School of Mines, Brighton, Sheffield, Leeds, St Andrews, Sao Paolo, BGS), with ten industry partners and eight core international research collaborators.
More information about SoS RARE can be found on the official website.