This study focuses on a Cretaceous Caribbean example of juvenile additions to the continental crust. The basaltic-tonalitic rock association studied is reminiscent of greenstone belts, which are believed to represent some of the earliest continental crust. The basaltic Aruba Lava Formation is part of the Cretaceous (predominantly 91 - 88 Ma) Caribbean oceanic plateau, which moved into the Caribbean region from the Pacific. The thick succession of submarine-to-emergent volcanic and sedimentary rocks on Aruba implies an intra-oceanic origin, and new petrographic, geochemical and isotopic data are all consistent with derivation of the Aruba Lava Formation from a mantle plume. Intrusion of a predominantly tonalitic batholith (dated as 85 - 82 Ma) occurred concurrently with deformation of the Aruba Lava Formation. The batholith is interpreted as having formed in response to the earliest stages of subduction beneath the plateau. This occurred subsequent to a subduction polarity reversal caused by the reluctance of the Caribbean oceanic plateau to be subducted. Subduction-derived mafic magmas, originating from the remnant mantle plume source region, were added to the plateau crust, where they triggered intracrustal partial melting and tonalite generation. This work demonstrates that rapid crustal growth can occur via accretion of oceanic plateaux: this mechanism does not require the presence of pre-existing crust, and may be analogous to the mechanism that generated the earliest continental nuclei. Addition of subduction-derived melts to the accreted material "ripens" the embryonic continent; this can happen within a few million years after the initial accretion event. Mantle plumes play an important part in transfer of mass and thermal energy from the mantle to the crust, and in reorganising tectonic plates. This allows reprocessing, remelting, and ripening of mantle-derived basalts to generate continental crust.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:696647 |
| Date | January 1999 |
| Creators | White, Rosalind Vanessa |
| Publisher | University of Leicester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/2381/30440 |
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