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Artigos em revistas ► internacionais com arbitragem

 

Referência Bibliográfica


TRIPPANERA, D., PORRECA, M., RUCH, J., PIMENTEL, A., ACOCELLA, V., PACHECO, J., SALVATORE, M. (2014) - Relationships between tectonics and magmatism in a transtensive/transform setting: An example from Faial Island (Azores, Portugal). Geological Society of America Bulletin, 126 (1/2): 164-181, doi: 10.1130/B30758.1.​

Resumo


​The relationships between tectonics and hotspot-related magmatism in transform/ transtensive settings are poorly known. The Azores archipelago, lying where the trans- form plate boundary between the Nubian and Eurasian plates meets the Mid-Atlantic Ridge, is a rare site to investigate these re- lationships. The distinct tectono-magmatic features of Faial make it the ideal island to focus the study. Here, we analyze the rela- tionships between tectonics and magmatism, using remote-sensing, fi eld, and paleomag- netic analyses. Dominant WNW-ESE–trend- ing lineaments correspond to major faults with transtensive dextral motion and NE- SW opening, probably related to the nearby transtensive Terceira Rift. Most (~60%) dikes, vent elongations, and alignments are parallel to this system. The lavas forming the basement of the distinctive WNW-ESE– trending Pedro Miguel graben strike paral- lel to the graben axis, dipping outward with a tilt consistent with that of paleomagnetic data. These lavas are dissected by the WNW- ESE–trending transtensive faults. Therefore, the graben consists of outward-tilted fault- bounded blocks, forming two opposite-verg- ing dominoes. Its estimated stretching factor (β = 1.35) and mean extension rate (between 3.4 and 8.2 mm/yr) are similar or slightly larger than those of Terceira Rift, to the east. Part of the graben extension may be magma induced, via diking. We suggest that: (1) Faial, along with the nearby Pico Island, is a major locus of extension within the Azores, directly above the imaged hotspot; and (2) the Faial- Pico magmatic segment constitutes the offset, westward magmatic continuation of the Ter- ceira Rift. The segment opening highlights the importance of extensional strain along magmatic transtensive plate boundaries.

Observações


Anexos