HR: 0830h
AN: V31E-0982    [PDF]
TI: Mantle Xenoliths of Cerro Mercedes, Costa Rica, Central America
AU: * Lindsay, F N
EM: flindsay@rci.rutgers.edu
AF: Rutgers University, Geological Sciences Wright Labs 610 Taylor Road, Piscataway, NJ 08854 United States
AU: Carr, M J
EM: carr@rci.rutgers.edu
AF: Rutgers University, Geological Sciences Wright Labs 610 Taylor Road, Piscataway, NJ 08854 United States
AU: Herzberg, C T
EM: herzberg@rci.rutgers.edu
AF: Rutgers University, Geological Sciences Wright Labs 610 Taylor Road, Piscataway, NJ 08854 United States
AU: Feigenson, M D
EM: feigy@rci.rutgers.edu
AF: Rutgers University, Geological Sciences Wright Labs 610 Taylor Road, Piscataway, NJ 08854 United States
AB: Mantle peridotite occurs as xenoliths in lavas and bombs at Cerro Mercedes, a Plio-Quaternary potassic alkaline basalt volcano approximately 70 km behind the volcanic front of northern Costa Rica (Tournon and Alvarado, 1997). Mineral exploration led to the first discovery of abundant mantle xenoliths in Central America (Vargas and Alfaro, 1992). The compositions of 71 xenoliths recovered in January 2003 include dunite, harzburgite, lherzolite and olivine websterite. Twenty xenoliths have a diameter of at least 3 cm. The nodules are abundant in basalt outcrops and the rare bombs. In spite of substantial soil development in a rain forest environment, both xenoliths and host lava remain well preserved. Olivine, pyroxenes and spinel are common, plagioclase is present and garnet appears to be absent. There is no obvious shearing or deformation and several pyroxenes are as much as 1 cm in diameter. The mineralogy suggests a relatively shallow upper mantle source, within either the lithosphere or possibly the uppermost asthenosphere. Cerro Mercedes, at latitude $10\deg$ 58' N and longitude $82\deg$ 21' W, lies along the Rio San Juan, which is locally the border between Nicaragua and Costa Rica, Central America. This location approximately coincides with a boundary between dominantly depleted mantle to the northwest and OIB or Galapagos-like mantle to the southeast. We will use mineralogical data to better define the likely depths and oxidation states of representative nodules and isotopic data to define the type of mantle source.
DE: 1025 Composition of the mantle
DE: 3640 Igneous petrology
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting