Magmatic rock series and high-pressure metamorphism as constraints on the tectonic history of the southern Caribbean

Abstract

The contact relationships between metabasalts (eclogites, glaucophanites, prasinites, etc.) and the enclosing mica schists in the Venezuelan Coast Ranges favour a common petrological history for both. Mineralogical disequilibria, such as replacement textures and mineral zoning in the metabasic assemblages, can all be related to a single metamorphic cycle. Relict deuteric/late magmatic hornblende epitaxially overgrown by the barroisitic amphibole of this metamorphic event shows that the latter has been the only regional metamorphic episode to have affected these rocks. The high-pressure character of the metamorphism is a logical consequence of overthrusting related to collision of the Aruba-Blanquilla island arc with the South American continental margin. The well-defined stratigraphy and detailed radiometric dating of intrusive rocks in the Netherlands Antilles indicate that this collision took place in the Coniacian/Campanian interval.The igneous rocks of the Netherlands Antilles, which are considered to form part of the colliding arc, consist largely of submarine volcanics, as well as a tonalite/gabbro batholith. These rocks range in age from middle Albian to Coniacian. The volcanics of Curaçao and Aruba are composed of basalts with a MORB chemistry and are oceanic in origin. Nevertheless, these sequences differ from "normal" oceanic crust by their thickness, chemical homogeneity and the non-depleted nature of the source, thus suggesting that they were fed by a prolific chondritic mantle plume. The volcanics of Bonaire range from basalt to rhyolite in composition and are chemically related to the primitive island arc series. An important characteristic is the high initial water content of these magmas, *Present address: Geological Survey of the Netherlands, Spaarne 17, Haarlem, The Netherlands. D. J. Beets and Others as shown by the geometry and mineralogy of the flows. The tonalite/gabbro batholith on Aruba is of calc-alkaline composition. The similarity in chemistry between the volcanics of Bonaire and the Villa de Cura Group of the Venezuelan mainland supports the view that the latter is an overthrust remnant of the colliding arc. Comparison with the metabasalts of the La Rinconada Group of Margarita Island is equivocal.Existing paleomagnetic evidence indicates that the arc underwent a 90° north-south to east-west rotation shortly before collision, and that the colliding arc extended via the Aves Ridge into the Greater Antilles. The age of the oldest volcanics of this arc, and thus the age of its origin, is uncertain. Most data favour formation in the Early Cretaceous, but a Late Jurassic age is also possible. Consequently, two alternative models for the evolution of the arc are proposed: one in which the arc forms as a lengthening Central American "isthmus" in response to opening of the Caribbean in the Late Jurassic, and a second in which the arc originates in the Pacific in the Early Cretaceous. In order to collide with the northern as well as southern margin of the Caribbean, the arc must have lengthened...

Geodynamic significance of the Raspas Metamorphic Complex (SW Ecuador): geochemical and isotopic constraints

“…In Venezuela, the Siquisique ophiolites of Middle Jurassic age (Bartok et al, 1985) are considered petrologically comparable to the oceanic plateau assemblages of the Curac ß ao island (Donnelly et al, 1990), while Beets et al (1984) postulate that the Margarita HP metabasic rocks (Sisson et al, 1997) are tholeiites of Late Jurassic age, possibly of MORB affinity. The Aptian -Albian La Rinconada unit (Margarita island, Venezuela) comprises HP gneisses and eclogites of MORB chemistry metamorphosed at ca.…”

Crustal structure of the South American–Caribbean plate boundary at 67°W from controlled source seismic data

“…The arc consists of plutonic, volcanic and volcaniclastic rocks of oceanic plateau and island arc origin [Beets et al, 1984], related to the subduction of the Proto-Caribbean plate. On the basis of the continuity of free-air gravity anomalies along the plate margin (Figure 1c), it has been inferred that the Leeward Antilles arc represents the westward extinct continuation of the Lesser Antilles volcanic island arc [Mann, 1999].…”

The Curaçao Lava Formation: Samples of the Oldest and Most Primitive Magmas from the Galapagos Plume

“…An angular unconformity separates this formation from an approximately 2 km thick section of pelagic, silicarich, and clastic sediments (Knip Group) and turbidites (Midden Curacao Formation). These units contain a minor amount of volcanics apparently of subduction affinity (Beets et aL, 1984), however it is the lower, CLF which is of interest to the current study.…”

“…In the uppermost half of the sequence the pillow lavas are interrupted by hyaloclastite units and the intrusion of sills and dykes. Beets et al(1984) noted that this 5 km section of magmas shows some evidence for decreasing lava density with height, with picritic and olivine tholeiitic rocks occurring towards the bottom (MgO 8-31 wt%) and the upper half of the sequence dominated by olivine and ol___pl__+px tholeiitic magmas (MgO 5-10 wt%). A narrow (only a few metres thick) intercalation of sediment contains ammonites of middle Albian age (Weidmann, 1978) which, despite some confusion with the results of K-Ar dating, suggests that the CLF is approximately 100 Ma old.…”

“…The crust now forming the basement of the Caribbean is believed to have been transported from its site of formation in the Pacific by processes of eastward subduction (e.g., Malfait and Dinkelman, 1972;Burke et al, 1978;Beets et al, 1984;Duncan and Hargraves, 1984). Duncan and Hargraves (1984) re-evaluated the origin of the Caribbean crust using plate reconstructions relative to the hotspot reference frame.…”