Síntesis geocronológica del magmatismo, metamorfismo y metalogenia de Costa Rica, América Central

a comprehensive compilation of 651 (since 1968) radiometric ages determinations (415 40ar/39ar, 211 k/ar, 5 u/th, 4 rb/sr, 2 u/pb, and 13 fission track thermochronology ages using zircon) provides a complete picture of the igneous stratigraphy of costa rica, and information about the age of the major metamorphic and metalogenic events in the region. igneous rocks of late jurassic to middle eocene age (~ 160 to ~ 41 ma), mainly accreted ophiolites. at the beginning of campanian time (~ 71 ma), the actual subduction zone was established, represented by volcanosedimentary rocks of basic to felsic composition. however, voluminous subalkaline, primary volcanic rocks appeared only after ~ 29 ma. intrusive to hypabyssal granitic to gabboic plutons, stocks, equivalent dykes and sills, are widely exposed in the talamanca range (~ 12.4 - 7.8 ma), cerros de escazú (~ 6.0 - 5.9 ma), and fila coste？a (~ 18.3 - 16.8 and ~ 14.8 - 11.1 ma), tapantí-montes del aguacate-carpintera (~ 4.2 - 2.2 ma) and guacimal (~ 6.4 - 5.2 ma). arc rocks between 29 and 11 ma are known in the san carlos plains and in southern costa rica. the location and age of the igneous rocks indicated that there was a 20°counterclockwise rotation of the arc (termed as proto-volcanic front) between 15 and 8 ma, with a pole of rotation centered on southern costa rica. this rotation is attributed to deformation in the overriding plate (shortening in the south coeval with extension in the nw), accompanied by trench retreat in the south. at ~ 3.45 ma arc-related volcanism shut off in southern part of the region, but local acid-adakite volcanism persisted in the talamanca range (4.2 - 0.95 ma) due to the subduction of the cocos ridge. the paleo-volcanic front is represented by arc-related rocks (8 - 3.5 ma) along the length of costa rica, parallel to but in front of the modern arc. this activity was followed by the monteverde (2.1 - 1.1 ma) andesitic/basaltic effusive event, which progressively, retreated to the ne. thu