The geochemistry of young volcanism throughout western Panama and southeastern Costa Rica; an overview
The geochemistry of young volcanism throughout western Panama and southeastern Costa Rica; an overview
Journal of the Geological Society of London (August 1992) 149 (4): 569-579
- absolute age
- adakites
- alkaline earth metals
- aseismic margins
- basalts
- Cenozoic
- Central America
- chemical composition
- Costa Rica
- igneous rocks
- isotope ratios
- isotopes
- K/Ar
- lithosphere
- metals
- Nd-144/Nd-143
- neodymium
- oceanic lithosphere
- Panama
- plate tectonics
- Quaternary
- rare earths
- Sr-87/Sr-86
- stable isotopes
- strontium
- subduction
- volcanic rocks
- volcanism
- western Panama
- southeastern Costa Rica
Oblique aseismic subduction below this region has produced arc- related volcanism over the last 2 m.y. The volcanism consisted of andesites to rhyolites but mainly dacites, and has geochemical characteristics suggesting a metamorphosed basaltic source. It is suggested that thesubduction of young oceanic crust set up conditions under which the slab melted rather than the overlying mantle wedge. The melts are sometimes associated with a few rare young high-Nb basalts, but there is no obvious link between them through differentiation. Numerous representative rock analyses for major, trace and REE are tabulated, together with K/Ar dates for 28 rocks. The eruption of these rocks with slab-melt compositions and high-Nb basalts was preceded by a 2-3 m.y. period of relative quiescence. Prior to this, there was a 7 m.y. period of calc- alkaline volcanism typical of the present-day magmatism (associated with a distinctive Benioff zone) found throughout the Central American arc. The abrupt transition in volcanism with time from an early calc-alkaline sequence to a later sequence of high- Nb basalt with these andesites, dacites and rhyolites resulting from slab-melt (and thereby comparable with the rocks of Adak Island, Alaska) may record a change in the tectonic setting of W Panama and SE Costa Rica over the past 12 m.y.