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Conveners: A. García Casco and M. Iturralde-Vinent

Participants: Edward Lidiak (USA), John Lewis (New Zealand), Antonio García Casco (Spain), Rafael Torres Roldan (Spain), Concepción Lázaro (Spain), Joaquín Proenza (Spain), Claudio Marchesi (Italy), Carlos Garrido (Spain), Fernando Gervilla (Spain), Kenya Núñez Cambra (Cuba), Manuel Iturralde-Vinent (Cuba).

The aim of the Carib-WGGP meeting was to present and debate new unpublished results of different ongoing projects that are studying the petrology and geochronology of igneous and metamorphic rocks in the Greater Antilles. These projects cover the Virgin Islands and Puerto Rico (E. Lidiak and W. Jolly), Hispaniola (J. Lewis and colleagues), Western Cuba (J. Proenza, J. Melgarejo, F. Gervilla, C. Garrido, C. Marchesi, and colleagues), and Cuban petrology and geochronology of metamorphic complexes (A. García Casco, R. Torres Roldan, C. Lázaro, K. Núñez, M. Iturralde-Vinent, and colleagues). In the introductory session, M. Iturralde-Vinent presented an overview of the Greater Antillean so-called ophiolites, discussed the problem of the interpretation of the presumed allochthonous terranes in the Caribbean, and with the active participation of other Carib-WGGP members, examined in detail the main characteristics of the Caribbean Plate.

Tectonic model of Pindell and Kennan (2002)
The tectonic model of Pindell and Kennan was discussed in light of new data and new field observations that were presented by the various participants at the meeting. Particular emphasis was placed on trying to integrate this new information into a viable model of Caribbean Plate Tectonics. Discussions were open and very interesting, so we all enhanced our knowledge on the geology of the northern Caribbean. Our discussions also indicate that important data are missing from key areas of the northern Caribbean in order to produce a well-based Plate Tectonic Model.

Future research should be directed to address the problem of the age and petrology of the igneous and metamorphic complexes of the northern Caribbean, applying the latest development in the respective fields. Currently, research projects are studying these problems in Cuba, the Dominican Republic and Puerto Rico and the Virgin Islands. However, it is also extremely important to investigate the igneous and metamorphic complexes of Haiti, which have not been studied for a long time.

As a great finale for the meeting, we participated in a field excursion to the Betic Cordillera and visited a number of outcrops of the Ronda subcontinental peridotites and related rocks.

We reached the following main conclusions as a result of debate and discussion at the Workshop:

1. Many features of Northern Caribbean geology are not properly addressed by the model of Pindell and Kennan (2002). This model must be elaborated in greater detail, and modified in several aspects, in order to account for these new data. Some of these modifications will be clear in the following paragraphs.

2. The mafic-ultramafic bodies that crops out along the northern Caribbean present much more complex settings and diversity in genesis than previously thought. The Cuban northern ophiolites (?), for example, are to be restricted, as a structural-genetic term, to those outcrops found between Cajalbana (NW Cuba) and HolguÌn (NE Cuba). These rocks encompass both suprasubduction and plateau (?) crustal sections. The Cuban northeastern ophiolites, formerly considered as part of the northern ophiolites, must be placed independently as the MayarÌ-Cristal and Moa-Baracoa massifs. Now they are identified as suprasubduction representing an arc/back arc crustal pair, and their present tectonic position is different from the ophiolites elsewhere in Cuba.

3. In Cuba (Margot and Guira de Jauco), as well as in the Jurassic Duarte complex of Hispaniola, within distinct geological contexts, occur mafic and metamorphic rocks that are interpreted as plateau basalts. But the age of the protolith of the Cuban occurrences need to be refined. Margot basalts have been recently dated as Cenomanian-Turonian (Pszczólkowski, 2002).

4. Metamorphic soles of Cuban ophiolites have been identified in Eastern Cuba. New structural and age data of these rocks indicate a complex emplacement history, with different steps during the Late Cretaceous starting, at least, in the Turonian.

5. The Sierra del Convento (Southeastern Cuba) has been considered as part of the northern ophiolites. However, new petrologic data suggest that it represent an accretionary subduction complex with HP/LT metamorphic rocks that should be placed as an independent tectonic element. On-going research in similar complexes, such as La Corea in Mayari-Cristal, show some compositional similarities with Sierra del Convento, adding complexities to previous interpretations.

6. The Median belt of Hispaniola, as originally defined by Carl Bowin, includes magmatic and metamorphic complexes of different types of suprasubduction environments as well as rocks of oceanic plateau setting. Such amalgamation of igneous and metamorphic rocks has no counterpart in any other place within the northern Caribbean. On the other hand, in central Hispaniola, the Early and Late Cretaceous arc complexes outcrop as independent, apparently non-related belts.

7. The available data from SW Puerto Rico's mafic-ultramafic complexes indicate that there are three belts that contain mafic rocks of either N-MORB or pre-arc, within-plate origin and Jurassic through Early Cretaceous radiolarian cherts. These rocks pre-date the subduction complex in western Puerto Rico, and probably have no counterpart in the northern Caribbean.

8. In all of the Greater Antilles occur isochronous arc-related volcano-plutonic bodies that crop out independently and generally juxtaposed against the mafic-ultramafic belts. The relationships between these two main geologic setting is as yet poorly understood. Are they paired arcs (?), or are they just different structural-compositional belts within an arc complex?

9. The extensive amount of new geochemical data from the Cretaceous volcano-plutonic (arc) complexes in the Virgin Islands suggest that the geological situation is more complex that previously understood. Virgin Islands yield an Early Cretaceous Primitive Island Arc complex, well known to occur also in eastern Puerto Rico, Hispaniola and Cuba. Nevertheless, the structural relationships between these Virgin Island rocks and those of eastern Puerto Rico are not yet clear.

10. The extensive amount of new and existing geochemical and geochronological data from the volcano-plutonic (arc) rocks in Puerto Rico allow the distinction of two main arc complexes (possible terranes), separated by a major NW-SE fault system. The Northeastern Puerto Rican suspect terrane (?) contains several stages of volcano-plutonic activity, from Albian to Middle Eocene, related to a subduction zone located toward the north and dipping southward. The Southwestern Puerto Rican suspect terrane (?) consists of an arc complex of Santonian to Middle Eocene age that is related to a north-dipping subduction zone located to the south.

11. The Paleocene-Eocene arc complex in Cuba generally is not genetically related to the Cretaceous arc complexes or mafic-ultramafic bodies, and probably was generated by an independent subduction zone. On the other hand, there are no obvious relationships between the Paleocene-Eocene arc rocks of eastern Cuba (Sierra Maestra) and Hispaniola, or between rocks of similar age in Hispaniola and Puerto Rico.

12. The Paleocene-Eocene pyroclastic-sedimentary rocks of northeastern Cuba (Sabaneta and related Formations), genetically related to the isochronous volcanic arc centers in the Sierra Maestra of southeastern Cuba, are also recorded from the Cayman Rise (ODP) and Imbert Formation of Hispaniola.

13. Late Eocene and younger arc rocks occur in Virgin Island, and have no counterpart elsewhere within the northern Caribbean. Probably belong to the Lesser Antilles arc.

14. It was realized that the occurrence of late Tertiary arc-related magmatic rocks in Hispaniola (Padre Las Casas, Valle Nuevo) has not found an explanation in any recent Caribbean Plate Tectonic Model.

15. We examined the significance of the Cuban SW terranes (Escambray, Pinos and Guaniguanico), and found them to represent fragments of Jurassic (?) -Cretaceous continental margin complexes mixed with oceanic crustal elements. Some of the metamorphism of these terranes involved and represent collision with the western segment of the volcanic arc in pre-Latest Cretaceous time (< 70 ± 2 Ma). We found that each terrane represent a distinct collisional setting, and has no counterpart in other places of the northern Caribbean. The original location of these terranes, along the North American Continental Margin, has not found yet an agreement in terms of their precise position.

Reference
Pszczólkowski, A. 2002. The Margot Formation of western Cuba: a volcanic and sedimentary sequence of (mainly) Cenomanian-Turonian age/ Bull. Polish Acad. Sc., Earth Sciences 50(2):193-205.

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Last revised: October 31, 2003