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HALOKINESIS AND MINIBASIN DEVELOPMENT LINKED TO MANTLE MAGMATICS AND VOLCANIC PLUMBING SYSTEMS, CABO FRIO AREA, OFFSHORE BRAZIL

Texto do resumo

Jurassic, Cretaceous and Palaeogene extrusive and intrusive magmatics have been well documented in Pre-salt and Post-salt sections of the Santos and Campos basins, offshore Brazil. Magmatic types and age dating for some of them have been ascertained from exploration wells. The links between sources of magma and their related plumbing systems remain to be established, as does the role of magmatic loading locally driving halokinesis and forming post-salt minibasins in the Cabo Frio area.
Seismic images from deep crustal (2D) and shallower high-resolution 3D reflection seismic of the Cabo Frio area, tied to exploration wells at the limit between the Santos and Campos basins, were interpreted to show the main seismic facies and discontinuities and to identify magmatic geobodies in the rift and post-rift sections. Gravity and magnetic data were also used to help and confirm the interpretations made on seismic, more specifically to determine the nature and structure of the continental crust.
The seismic facies and their geometries allow interpretation of presalt synrift half-graben clastics; late rift and sag carbonates; salt; post-salt deposits such as turbidites and sediment drift; magmatic plutons in the basement; intrusions with saucer sills; possible flood lava flows, and volcanoes. Geological features identified comprise the Moho; numerous magmatic intrusions in the pre-rift basement and rift to post-rift sections; magmatic plumbing or feeder systems to vents or volcanoes and minibasin development linked to halokinesis resulted from the post-salt emplacement of magmatic bodies.
Small mantle plutons linked to intrusions and volcanic plumbing systems have been identified in the basement. The comparison of pluton locations with gravity and magnetic anomaly maps tests and confirms the interpretations made on seismic.
The post-salt magmatic loads driving salt movement may be linked to specific intrusions. Intrusive plumbing systems fed by the plutons were active at different times, with younger events possibly reactivating earlier systems. Loading caused by post-salt intrusions resulted in salt movements and created half-graben sedimentary minibasins. The seismic stratigraphy of post-salt sedimentary minibasins, tied to wells, shows the timing of the emplacement of intrusive and extrusive loads.
Intrusive and extrusive magma in the Cabo Frio area are sourced by small plutons in the basement above the Moho, in support of the hypothesis of a transitional to magmatic rather than continental crust. Plumbing systems feeding intrusions and extrusions may have been active intermittently. Post-salt loading of magmatics enhanced salt tectonics and locally created post break-up minibasins.

Palavras Chave

Santos Basin; Magmatism; salt tectonics; Minibasins