The village of Bribri, Costa Rica is located at the Panamanian border. Outcropping 5-7 km to the south-west are two elongate bodies of alkaline volcanic rocks ~1.5-2.0 km in length, the northernmost trending east-west and the other north-south. Country rocks are sedimentary rocks from the Miocene-Pleistocene. Magmatic rocks are described as alkaline basalts appearing grey to black with porphyritic pyroxene, olivine, minor amphibole. Biotite is found accompanying notable amounts of nepheline and sodalite in some samples. These rocks are believed to have formed from backarc magmatism from the subduction at the Cocos Ridge, behind the Cordillera de Talamanca in the Limon Basin. Geochemical data including whole rock major and trace element, and stable isotopic data can be found in Abratis (1998).