Day 2 saw us head to the south-west side of St Lucia, towards the town of Soufriere and the towering Pitons, two ancient volcanic plugs that dominate the landscape.
The area around Soufriere and the Pitons is mostly jungle, making finding outcrops (especially cumulate bearing ones!) rather difficult. We began our search in some road cuts en route to the town of Soufriere, through some massive pyroclastic density current deposits from the Soufriere Volcanic Centre (the most recent phase of activity on the island). Unfortunately our morning of searching yielded no cumulates from any of these outcrops – at this point we realised how lucky we were to have found so many on day 1!
We stopped for lunch by the pitons, before heading on to the Belfond quarry, the site of a Soufriere Volcanic Centre dacite lava dome. Here we were much more successful, as the quarry had recently excavated more of the dome, leaving rock piles full of cumulates and cumulate like mushy material. Our samples here included “mafic crystal clots” (zones of interlocking crystals dominated by mafic minerals such as amphibole and pyroxene) included in the dacite magma, plagioclase and amphibole dominated cumulates with aligned minerals, and enclaves of mafic magma within the felsic host dacite. The presence of such enclaves and mafic crystal clots may indicate that mixing of mafic and felsic magmas occurred before the eruption of the dacitic done-forming magma. It wasn’t all plain sailing however, as we were forced to retreat to the car several times due to torrential rain!
The remainder of the afternoon was spent driving around the jungle below the Pitons on steep winding roads hunting for small roadcut outcrops. “Rachel” (our hired Kia Rio) did well to make it up the steep slopes to get us to the localities, but the heavily weathered outcrops meant that we were unable to find any more useful samples. We ended the day with a seafood dinner in Marigot Bay, before reflecting on a successful couple of days sampling in St Lucia.
The next few days will be spent on St Vincent, where we plan to collect even more cumulates, the most mafic lavas in the Lesser Antilles, and climb to the crater of La Soufriere volcano.