MULTI-PHASE EVOLUTION OF THE CARIBBEAN PLATE THROUGH PLUME, ACCRETIONARY, AND COLLISIONAL TECTONICS

1. MULTI-PHASE EVOLUTION OF THE CARIBBEAN PLATE THROUGH PLUME, ACCRETIONARY, AND COLLISIONAL TECTONICS Contribution to: IGCP 433 16^ International Caribbean Geological Conference, Barbados, June 2002 Giuseppe GIUNTAand Yldirim DILEK Dipartimento Geologia, Università Palermo, Italia Geology Department, Miami University, Oxford, USA (Withthe collaboration of Daniela Cutrupia)

2. The Caribbean Plate evolutionary history , from the Jurassic-Early Cretaceous until the Present times, was realized through plume, accretionary and collisional tectonics. The Ophiolitic units involved in the main Terranes which constitute the Northern, Southern and Western margin of the plate record the stages of this evolution. We will try to treat the main steps of the tectonic evolution of the Caribbean Plate with the objective of stressing the recognized regional constraints and the related problematics, taking in the account the models of Giunta, Giunta and Beccaluva, Iturralde Vinent, Mann, Meschede and Frisch, Pindell, Ross and Scotese, Stephan, et al. (and references therein).

3. The Western margin is a mosaic of different blocks reciprocally juxtaposed and facing the Middle American Trench, whereas both the Northern and Southern margins are wide shear zones (the former sinistral , the latter dextral) along which the Terranes are dismenbered.

4. The Caribbean Terranes record various tectono-magmatic, metamorphic and deformative events Along the Caribbean Plate’s margins have been recognized several types of “ophiolites”. Most of them have been originated at convergent plate borders, as suprasubduction-ophiolites, and underlie IAT and IAC volcanics, or in places are crosscut by granodioritic and tonalitic intrusives. MOR ophiolites subordinately occur, mainly either in narrow belts or in blocks included in melange-like sequences. The OIB ophiolites are prevalent, representing a thickened oceanic crust of a plateau structure, as well as in the Colombia and Venezuela Basins. Moreover, a sub-continental magmatism, with WPT affinity, characterizes some portions of the continental crust, which does not clearly represent the extension of NOAM and SOAM. modified from Beccaluva et al., and Giunta et al., (2000; 2001; 2002)

6. The geotectonic elements were originated and in turn played in the most representative stages of the Caribbean geodynamic history

7. Proto-Caribbean stage related to spreading and plume tectonics The proto-Caribbean oceanic crust was generated in an intra-American setting with an Atlantic affinity at an equatorial latitude near Central America since the Late Jurassic. It was thickened at its western end by plume related magmatism in an easternmost Pacific setting during the Cretaceous, acquiring an irregular oceanic plateau character. Cartoon-models are modified from Giunta et al., (2000; 2001; 2002)

8. Eo-Caribbean stages related to subduction-accretionary tectonics: Intraoceanic subduction zones (and in few cases sub-continental) were initiated within the proto-Caribbean-Atlantic domain during the middle-Late Cretaceous that produced HP/LT metamorphic complexes and volcano-plutonic sequences with IAT and IAC affinities (1^ eo-Caribbean phase)

9. Since the Late Cretaceous, the progressive wedging of the Caribbean oceanic plateau eastwards between the North and South Americas, created a compressional regime along its eastern edge, facilitating an oblique westward subduction of the proto-Caribbean oceanic crust beneath itself (2^ eo-Caribbean phase)

10. Caribbean stage related to collisional tectonics: West of the plateau, continental fragments (i.e., Chortis) and volcanic arc complexes (i.e., Chorotega, Choco) in the upper plate of an east-dipping subduction zone delineated an accretionary orogenic system at the western margin of the Caribbean Plate. Large-scale tear faulting along the northern and southern margins of the Caribbean Plate facilitated eastwards dispersion and uplifting of the subduction-accretion systems, in the Late Cretaceous-Tertiary. The modern Caribbean Plate is mainly represented by the Cretaceous plateau crust, trapped in the current Colombia and Venezuela basins, and in places deformed at its edges

11. FACTS AND CURRENT PROBLEMS ?

12. This arrangement can be related to the progressive insertion of the Caribbean Plateau between NOAM and SOAM, leading to the Collisional stage. Facts: a) the ophiolitic belts occur between the Caribbean Plateau and Continents, or between Cont. Blocks, b) no granitoid magmatism intrudes the NOAM and SOAM, c) the ophiolitic belts overthrust through foredeep basins, or are juxtaposed against the continents, in transpressional stress-field; Should demonstrate that: - no Caribbean plateau no Caribbean plate; - no classical Cordilleran type tectonics.

13. This arrangement can be related to the diachronous shifting of two triple-points, leading to the Late Cretaceous accretionary stage strictly followed by the collisional stage (2^ eo-Caribbean stage).

14. COLLISIONAL SHEAR ZONES EVOLUTION RELATED TO THE OPPOSITE TRIPLE-POINTS SHIFTING, SINCE THE LATE CRETACEOUS Facts: a) a strongly oblique intraoceanic subduction occurred, with westward-directed sinking below the Caribbean plateau, b) the granitoid-tonalitic arc magmatism seems to be related with this eastward shifting of two triple-junctions at the opposite endings of the Aves-Lesser Antilles arc, with different mechanisms in the northern and southern margins, c) the strike-slip faulting led to lateral dispersion of different terranes; should demonstrate a kinematic evolution close related with the eastward drifting of the Caribbean plateau, trapped between NOAM and SOAM. -what are the main differences between the northern and southern margins ? -and why they occur? -how can the northern margin be related to the US cordilleras ? -how can the southern margin be related to the northern Andes ?

15. The Late Cretaceous accretionary stage can be supposed in the cross-sectional cartoons Accrect. Facts: a)the granitoid magmatism intrudesthe inner portion of the ophiolitic wedges and/or flakes, the hangingwall plate of subduction system, and continental blocks, b) the architecture of the ophiolitic belts is either simple (from the base:MORandmelanges,SSZ-IATto IAC), orcomplicated byinsertion of continental blocks(i.e.: Escambray, Caucagua-El Tinaco),in places involved in subduction zones, c) the metamorphism shows facies which range from green shist and anphibolite to blue shist and eclogite, starting from middle Cretaceous, d) the exumation and subsequent obduction have been realized in a strike slip tectonic regime (either transpressional or transtensional), starting from the middle-Late Cretaceous; They would demonstrate two main episodes of subduction, mainly intraoceanic, and in places subcontinental, or involving rifted continental blocks. In this context would be one subduction older than the Late Cretaceous. SSZ MORB Accrect. Plateau MORB Collision. MORB Collision. Plateau MORB Collision. MORB

16. The 1^ eo-Caribbean phase is the most problematic to reconstruct: Our model represents only a tentative of regional reconstruction, and we can assert that this cannot be the right solution. In fact, at the moment there are no solutions at some main problems: (1) the Early Cretaceous paleogeography and morphology of the margins of the North and South American continents and minor blocks; (2) the sinking direction of the subducted oceanic slabs; (3) the locations of and relationships between the intraoceanic and sub-continental subduction zones. -which paleogeography can we envisage in the different subduction settings ? -is it possible to infer only one continous subduction process ?

17. Different models can be envisaged in cross-sectional cartoons: one of the first-order problem would be: A or B FLIP OR NO FLIP OF THE SUBDUCTION? A or B

18. For example, in the Southern Caribbean Plate margin of Venezuela 3 models can be supposed for the mid-Cretaceous (1° eo-Carib. Ph.), based on the main constraints which characterize the Caribbean Plate, which are: 1) the occurrence of a double arc magmatism and related SSZ allowed by the Early and Late Cretaceous convergences, and in complicated relationships with subcontinental subduction systems;2) at least three different subduction settings; 3) the HP-LT assemblages in oceanic, SSZ and continental lithospheres; 4) an atypical evolution of the early volcanic arc; 5) the irregular distribution of the second magmatic arc; 6) differences in retrograde evolutions connected to the exhumation of the ophiolitic units, also of SSZ, may be allowed by a strike-slip tectonics; 7) the supposed oblique exhumation of the subduction elements; 8) the different obduction and emplacement on the hangingwall plates. (from Giunta et al., AAPG, 2002)

19. A or A1 In conclusion, we should find much more constraints than we have, to demonstrate the sequential order of the events which led to a true kinematic evolution during the eo-Caribbean stages. Which philosophy shall we decide to follow ?? then B and C

20. We have collected a series of pieces of the Caribbean puzzle, then we have tried to assemble them in different stages Perhaps we are now trapped in the reconstruction itself !!