HR: 0800h
AN: V41B-1447    [Abstracts]
TI: 40Ar/39Ar Dating in Western Nicaraguan volcanics: New Constraints for the Volcanic Gap
AU: * Saginor, I
EM: saginor@rci.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscatoway, NJ 08854 United States
AU: Carr, M J
EM: carr@rci.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscatoway, NJ 08854 United States
AU: Swisher, C
EM: cswish@rci.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscatoway, NJ 08854 United States
AU: Turrin, B
EM: turrin@rci.rutgers.edu
AF: Rutgers University, 610 Taylor Rd, Piscatoway, NJ 08854 United States
AB: The active volcanic arc in western Nicaragua is separated from the Miocene arc by a temporal gap in the volcanic record, during which little or no volcanic material was erupted. Because the precise timing and duration of this gap has been poorly constrained, current fieldwork has focused on locating samples that may have erupted close to or even during this apparent hiatus in activity. New 40Ar/39Ar dates suggest that the volcanic production was limited or nonexistent between 1.6 and 7 Ma. However, this time span assumes that the oldest erupted material from the active arc has been sampled, which is almost certainly not the case. Even if we assume that this material is accessible to be sampled, the older lavas in this area have often been severely weathered by the humid Central American climate and are unsuitable for argon dating. Ash accumulation in ocean cores suggest that the gap may be no more than 2 or 3 my, another indication that more complete sampling of the area is needed. Once the age of the volcanoes in the active arc is known, they can be more easily compared to those in Costa Rica, where volcano age vs. volume plots indicate that the volcanoes have been growing at a constant rate for several million years and where no apparent gap exists. A similar correlation in volcano age vs. volume is not evident in Nicaragua, however this may also be related to incomplete sampling due to a lack of exposed outcrops coupled with intense weathering of older lavas. For these reasons, it may be difficult to estimate the duration and timing of the volcanic gap in Nicaragua with precision.
DE: 1140 Thermochronology
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005