Brazilian Equatorial Margin: evidences of magmatic intrusion and alteration of host rock from well data

2020 ◽  
Author(s):  
Andre Aquino da Silva ◽  
Yoe Alain Reyes Perez ◽  
Helenice Vital
Keyword(s):  
Host Rock ◽  
Plate Motion ◽  
South American ◽  
South American Plate ◽  
Magmatic Intrusion ◽  
Magmatic Rocks ◽  
Fernando De Noronha ◽  
Volcanic Islands ◽  
Well Data ◽  
Rock Alteration

<p>The mechanisms of magmatic intrusion is very complex and are commonly associated to pristine unconformities (weak spots) on the crust that ease its emplacement on the form of sills or dikes. When occurring on the Oceanic crust these weak spots may led to the formation of volcanic islands (such as Fernando de Noronha, on the Brazilian Equatorial Margin-BEM), submarine highs. Alignment of such features are related to Plate motion and the set of volcanos of Fernando de Noronha Ridge are considered a consequence of the westward motion of the South American Plate. Occurrence of magmatic rocks were found on a set of offshore wells at different depths and away of submarine highs. These magmatic emplacement suggests be related to a deep plume-fed mechanism which is the source of all sills found on the wells, as well as the volcanic highs occurring of the BEM. The lateral extents of the sills is greatly influenced by the presence of faults when preceding the intrusion, during which also occurred incorporation of parts of the host rock as xenoliths. On the well logs it is possible to observe changes on sonic slowness for the same lithotype when close to the sills, which indicates rock alteration due to the magmatic intrusion.</p>

Hot spot volcanic tracks and their implications for south American plate motion, Campos basin (Rio de Janeiro state), Brazil

2005 ◽  
Vol 18 (3-4) ◽  
pp. 383-389 ◽  
Author(s):  
Antonio Thomaz Filho ◽  
Pedro de Cesero ◽  
Ana Maria Mizusaki ◽  
Joana Gisbert Leão
Keyword(s):  
Rio De Janeiro ◽  
Hot Spot ◽  
Plate Motion ◽  
South American ◽  
South American Plate ◽  
Campos Basin ◽  
Janeiro State

scholarly journals Subduction initiation in the Scotia Sea region and opening of the Drake Passage: when and why?

2021 ◽  
Author(s):  
Suzanna van de Lagemaat ◽  
Merel Swart ◽  
Bram Vaes ◽  
Martha Kosters ◽  
Lydian Boschman ◽  
...  
Keyword(s):  
South America ◽  
Subduction Zone ◽  
Continental Crust ◽  
Drake Passage ◽  
Plate Motion ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Scotia Sea ◽  
The Antarctic

<p>During evolution of the South Sandwich subduction zone, which has consumed South American plate oceanic lithosphere, somehow continental crust of both the South American and Antarctic plates have become incorporated into its upper plate. Continental fragments of both plates are currently separated by small oceanic basins in the upper plate above the South Sandwich subduction zone, in the Scotia Sea region, but how fragments of both continents became incorporated in the same upper plate remains enigmatic. Here we present an updated kinematic reconstruction of the Scotia Sea region using the latest published marine magnetic anomaly constraints, and place this in a South America-Africa-Antarctica plate circuit in which we take intracontinental deformation into account. We show that a change in fracture zone orientation in the Weddell Sea requires that previously inferred initiation of subduction of South American oceanic crust of the northern Weddell below the eastern margin of South Orkney Islands continental crust, then still attached to the Antarctic Peninsula, already occurred around 80 Ma. We propose that subsequently, between ~71-50 Ma, the trench propagated northwards into South America by delamination of South American lithosphere: this resulted in the transfer of delaminated South American continental crust to the overriding plate of the South Sandwich subduction zone. We show continental delamination may have been facilitated by absolute southward motion of South America that was resisted by South Sandwich slab dragging. Pre-drift extension preceding the oceanic Scotia Sea basins led around 50 Ma to opening of the Drake Passage, preconditioning the southern ocean for the Antarctic Circumpolar Current. This 50 Ma extension was concurrent with a strong change in absolute plate motion of the South American Plate that changed from S to WNW, leading to upper plate retreat relative to the more or less mantle stationary South Sandwich Trench that did not partake in the absolute plate motion change. While subduction continued, this mantle-stationary trench setting lasted until ~30 Ma, after which rollback started to contribute to back-arc extension. We find that roll-back and upper plate retreat have contributed more or less equally to the total amount of ~2000 km of extension accommodated in the Scotia Sea basins. We highlight that viewing tectonic motions in a context of absolute plate motion is key for identifying slab motion (e.g. rollback, trench-parallel slab dragging) and consequently mantle-forcing of geological processes.</p>

scholarly journals Velocity field across the Southern Caribbean Plate Boundary and estimates of Caribbean/South-American Plate Motion using GPS Geodesy 1994-2000

2001 ◽  
Vol 28 (15) ◽  
pp. 2987-2990 ◽  
Author(s):  
Omar J. Pérez ◽  
Roger Bilham ◽  
Rebecca Bendick ◽  
José R. Velandia ◽  
Napoleón Hernández ◽  
...  
Keyword(s):  
Velocity Field ◽  
Plate Boundary ◽  
Plate Motion ◽  
South American ◽  
Caribbean Plate ◽  
South American Plate ◽  
Gps Geodesy ◽  
Southern Caribbean

scholarly journals Hotspot swells and the lifespan of volcanic ocean islands

2020 ◽  
Vol 6 (1) ◽  
pp. eaaw6906 ◽  
Author(s):  
Kimberly L. Huppert ◽  
J. Taylor Perron ◽  
Leigh H. Royden
Keyword(s):  
Residence Time ◽  
Plate Motion ◽  
Tectonic Plate ◽  
Mantle Sources ◽  
Volcanic Islands ◽  
Ocean Islands

Volcanic ocean islands generally form on swells—seafloor that is shallower than expected for its age over areas hundreds to more than a thousand kilometers wide—and ultimately subside to form atolls and guyots (flat-topped seamounts). The mechanisms of island drowning remain enigmatic, however, and the subaerial lifespan of volcanic islands varies widely. We examine swell bathymetry and island drowning at 14 hotspots and find a correspondence between island lifespan and residence time atop swell bathymetry, implying that islands drown as tectonic plate motion transports them past mantle sources of swell uplift. This correspondence argues strongly for dynamic uplift of the lithosphere at ocean hotspots. Our results also explain global variations in island lifespan, which influence island topography, biodiversity, and climate.

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