Geochemistry and tectonic setting of igneous and metaigneous rocks of northern Venezuela

Abstract

Northern Venezuela consists of a complex series of dismembered east-westtrending deformed belts that defi ne the southern edge of the Caribbean plate. This contribution uses petrologic and geochemical data to defi ne the tectono-magmatic affi liation of some of the belts. These include (1) mid-oceanic-ridge basalts (MORB) included within a mélange composed primarily of passive margin sediments in the Cordillera de la Costa belt, (2) Jurassic sublithospheric mantle and MORB in the Tinaco-Tinaquillo belt, (3) island-arc tholeiites of the Villa de Cura belt, and (4) oceanic island basalts and island-arc intrusive rocks on Gran Roque island, part of the Venezuelan and Dutch Leeward Antilles. Two of the belts (Cordillera de la Costa and Villa de Cura) were metamorphosed in subduction zones then exhumed and thrust onto the margin of Venezuela. The other two belts (Tinaco-Tinaquillo and Leeward Antilles) were obducted onto the edge of Venezuela. These different units record the complex evolution of the Caribbean plate: initial rifting, which formed the protoCaribbean seafl oor (MORB) and Great Arc of the Caribbean, followed by a reversal in subduction polarity caused by the overthickened crust of the Caribbean large igneous province, followed in turn by exhumation and/or obduction of the units and their subsequent emplacement onto northern Venezuela. In the Venezuelan islands, island arc activity continued through the Tertiary.

Tectonomagmatic setting and provenance of the Santa Marta Schists, northern Colombia: Insights on the growth and approach of Cretaceous Caribbean oceanic terranes to the South American continent

“…Correlative intra-oceanic fragments with associated continental inputs in their sediments are found in the Guajira Peninsula from northeastern Colombia (Weber et al, in press), the Netherland Antilles (Thompson et al, 2004;Wright and Wyld, 2004) and the Venezuelan coast (Stöckhert et al, 1995;Ostos and Sisson, 2005). These elements are therefore possibly related to a common arc formed in the front of the Caribbean plate.…”

“…Different types of mafic volcanites and ophiolite fragments have been found within the southern margin of the Caribbean, including island arc, MORB, rift, transitional continental and oceanic plateau remnants (reviews in Giunta et al, 2002;Thompson et al, 2004;Ostos and Sisson, 2005;Weber et al, in press). Their affinity and accretion have provided major insights on the tectonic evolution of the Caribbean oceanic plate and its relation with the South American continent.…”

The role of syntectonic sedimentation in the evolution of doubly vergent thrust wedges and foreland folds

“…Ostos and Sisson, 2005). Thin-skinned thrusting evolved from inverted fault systems during continued deformation through Miocene (c.f.…”

Thermochronology and tectonics of the Leeward Antilles: Evolution of the southern Caribbean Plate boundary zone

“…The oldest rocks on Gran Roque are amphibolites (Figure 6), which are derived from either MORB [ Santamaría and Schubert , 1974; Ostos and Sisson , 2005] or oceanic plateau rocks [ Giunta et al , 2002], and crystallized at 130 ± 14 Ma (K/Ar [ Santamaría and Schubert , 1974]). These are intruded by gabbros which were later metamorphosed to lower greenschist facies.…”

“…These are intruded by gabbros which were later metamorphosed to lower greenschist facies. Undeformed quartz diorites, pegmatites and aplites of island arc affinity [ Santamaría and Schubert , 1974; Giunta et al , 2002; Ostos and Sisson , 2005] extensively intruded the amphibolites and gabbros (Figure 6) at 65 ± 3.6 Ma (K/Ar [ Santamaría and Schubert , 1974]). The only exposed sedimentary cover on Gran Roque is Quaternary.…”