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Honduras Geology (12/5/97)
A Geochemical Arc-Transect: Honduras, Central America
L C Patino, M J Carr, M D Feigenson (Geol. Sciences, Rutgers
University, New Brunswick, NJ 08903: 908-932-2044; patino@zodiac.rutgers.edu)
(currently at 206 Natural Science Bldg., Geological Science Dept., Michigan
State University, East Lansing, MI 48824-1115 email: patinol@pilot.msu.edu)
Geochemical traverses across volcanic arcs can reveal changes in source
composition and degree of melting to generate magmas. Across Honduras there
are differences in the geochemistry of Quaternary basalts from three regions
(30, 120, 160 Km. behind the front). The area closest to the trench, Zacate
Grande, has LILE enrichment, HFSE depletion, and significant amount of
10Be in the lavas clearly indicating involvement of subducted material.
Low La/Yb ratios in basalts from this region indicate that these lavas
formed by relatively high degrees of melting. The effects of subducted
material are not seen in samples from Lake Yojoa, 160 Km. behind the arc.
The alkali basalts from this region appear to derived from a MORB-source
based on their isotopic signature, low 87Sr/86Sr and high 143Nd/144Nd.
Modest LREE/HREE ratios indicate that the lavas from this region are the
product of low degree melting of depleted mantle. Near Tegucigalpa, the
intermediate area 120 Km. behind the arc, the effects of assimilation-fractional
crystallization are evident. The LILE and HFSE patterns for basalts from
Tegucigalpa imply that subducted material could have been a component of
the original magmas, which were modified by assimilation of crustal material.
The changes in geochemistry among the three regions are gradational
and step-like. Ba/La ratios gradually decrease with increasing distance
behind the front until mantle like values are reached. HFSE concentrations
are low for basalts closer to the front, but the values drastically increase
for lavas from the region 160 Km. behind the front.
In: EOS (Trans. Am. Geophys. Un.), v. 74, no. 16 p. 349, 1993.
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