Madagascar fieldwork

View across the Ambohimirahavavy Complex from one of the pit sites. Photo Copyright Kathryn Goodenough
With the local labourers, above Ankatafa. Photo Copyright Kathryn Goodenough
Mineralised pegmatite outcrop near Ankatafa. Photo Copyright Eva Marquis
Field camp on the football field at Tsarabanja. Photo Copyright Kathryn Goodenough
Our whole field team at the Manongarivo camp. Photo Copyright Kathryn Goodenough
Manongarivo_Camp: Sunset at the Manongarivo camp. Photo Copyright Eva Marquis
Driving away from Manongarivo Reserve. Photo Copyright Kathryn Goodenough

On 15th September 2016 the SoS RARE team of Kathryn Goodenough, Guillaume Estrade, Megan Barnett and Eva Marquis travelled to Madagascar for our second field campaign. There were two main aims of the trip: 1) to collect laterite samples for SoS RARE research on the processing of ion adsorption deposits and the microbiology of the laterites; 2) to expand the rock sample set collected during last year’s reconnaissance trip, in order to improve our understanding of the underlying bedrock mineralization across the Ampasindava Alkaline Province.

On arrival in Antananarivo we were greeted (at midnight!) by our Malagasy colleagues Rocky and Fetra. The first two days were spent in Antananarivo, where we gathered supplies for our journey north and organized our fieldwork plans and permits to visit the study areas, including meetings with colleagues at Tantalus Rare Earths AG. We also met up with PhD researchers Sheree Armitstead and Morgan Blades from the University of Adelaide. It was great meeting other researchers interested in the geology of Madagascar, especially as there is still so much to learn and resolve about the geological history of this unique island.

On the morning of the 18th September we met our drivers and our cook Francis, and set off on the two-day drive to Ambanja in NW Madagascar. Once in Ambanja, we had a day spare whilst Francis finalized the field supplies, and we spent it visiting Mont Sambirano, a small complex where eudialyte-bearing phonolites had been recorded. On the 21st September we departed Ambanja for the Tantalus field camp at Betaimboay, situated in the SE of the Ambohimirahavavy Complex. This peralkaline igneous complex has been heavily weathered and is covered in thick laterites, which represent the most interesting REE mineralization in the Tantalus prospect. Our priority for this area was to collect samples from several pits dug into the laterite from different elevations and above varying bedrock lithologies. For the digging of the pits we employed a number of local villagers who dug at an incredible rate, easily cutting through the upper pedolith and saprolite layers in the laterite. This rate of work resulted in five pits being dug, sampled and remediated (including planting a palm tree on top of one) within 5 days. On the last day of pitting, Kathryn and Megan supervised the dig, enabling Guillaume and Eva to investigate the fantastic outcrops of peralkaline granitic pegmatites along the coast near Ankatafa.

On the 27th September we packed up our camp and travelled to Tsarabanja in the north of the Ambohimirahavavy Complex, an area with less REE mineralization in the laterite, which is valuable for comparison with the more mineralized zone to the south. Most of the team travelled to the new camp in the 4 x 4s but Guillaume, Fetra and a guide walked the 22 km, investigating the geology along the way. For our camp, the town elders kindly gave us use of the football field, which at least was almost flat. In such far flung villages we certainly provided a great deal of entertainment for the locals, and we even introduced a group of the younger kids to the delights of Danger Mouse. As we only had two days of field time, the fieldwork was focused on outcrops in two main rivers close to the margins of the complex, one associated with a notable magnetic high.

On the 30th September we packed and made the bumpy journey back to Ambanja to meet colleagues from the University of Antananarivo, and prepare for our expedition to the Manongarivo Complex (last studied in the 1960s). Perfect timing meant we were back in Ambanja for Megan’s birthday for which Francis treated us with a fabulous cake! The next day, on Guillaume’s recommendation, we took a day trip to the island of Nosy Be to hunt down some vanilla. On the way back we even managed some sampling of the Ankify Complex, finding wonderful syenite blocks with magma mingling textures on the side of the road.

On the 3rd October we departed Ambanja for the Manongarivo Special Reserve, and camped for two nights at the village of Beraty, before moving our camp some way up the mountain to the edge of the reserve. Slash and burn agriculture is prohibited in the reserve, so the lower slopes are covered by vanilla and coffee plantations that pass into primary rainforest higher up the slopes. The best outcrops are to be found in the rivers coming off the mountain, and in the first few days we found some amazing exposures of porphyritic trachytes, pegmatite and aplite dykes and syenites. However, the terrain where we were working is rather challenging, and on 7th October Megan unfortunately slipped and fell while investigating outcrops in a river, leading to fairly serious injury. A makeshift stretcher allowed her to be carried back to camp, and after a nervous 24 hour wait she was successfully evacuated by a helicopter arranged by Assistance Plus, a medical aid agency in Antananarivo. She was then flown onto La Réunion where she was treated for her injuries, and she subsequently returned to the UK in late October where she is recovering fully.

Following the incident the remaining members of the field team returned to Ambanja and thence back to Antananarivo. The samples took priority in the 4x4s and the majority of the team returned by the 'taxi brousse', which was remarkably fast! Back in Tana, we arranged export permits and shipping of the samples. We spent the last day in Madagascar having a wonderful meal prepared by Francis, enjoying our remaining hours in Tana and saying goodbye to all those people who made our trip a success. We would like to thank all of our Madagascan field team for their help and support in the field – we really couldn’t have done the work without them.

Eva Marquis and Kathryn Goodenough, October 2016


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