FN Archimer Export Format
PT J
TI Deep structure of the Pará-Maranhão/Barreirinhas passive margin in the equatorial Atlantic (NE Brazil)
BT 
AF ASLANIAN, Daniel
   Gallais, Flora
   Afilhado, Alexandra
   Schnurle, Philippe
   Moulin, Maryline
   Evain, Mikael
   Dias, Nuno
   Soares, Jose
   Fuck, Reinhart
   da Cruz Pessoa Neto, Otaviano
   VIANA, Adriano
AS 1:1;2:1;3:2,3;4:1;5:1;6:1;7:2,3;8:4;9:4;10:5;11:5;
FF 1:PDG-REM-GM-LGS;2:PDG-REM-GM-LGS;3:;4:PDG-REM-GM-LGS;5:PDG-REM-GM-LGS;6:PDG-REM-GM-LGS;7:;8:;9:;10:;11:;
C1 Ifremer, Department of Marine Geosciences, BP 70, Plouzané, France
   ISEL - Instituto Superior de Engenharia de Lisboa, Lisboa, Portugal
   IDL – Instituto Dom Luis, Lisboa, Faculdade das Ciências da Universidade de Lisboa, 1749-016, Lisboa, Portugal
   Instituto de Geociencias, Universidade de Brasília, Campus Darcy Ribeiro, 70910-900, Brasilia, Brazil
   Petrobras, Cenpes Research Center, Rio de Janeiro, Brazil
C2 IFREMER, FRANCE
   ISEL, PORTUGAL
   INST DOM LUIZ, PORTUGAL
   UNIV BRASILIA, BRAZIL
   PETROBRAS, BRAZIL
SI BREST
SE PDG-REM-GM-CTDI
   PDG-REM-GM-LGG
   PDG-DFO-NSE-ASTI
   PDG-REM-GM-LCG
   PDG-REM-RDT-SIIM
   PDG-REM-GM-LAD
   PDG-REM-GM-LGS
IN WOS Ifremer UPR
   copubli-europe
   copubli-int-hors-europe
   copubli-sud
IF 2.453
TC 11
AC the MAGIC Team
UR https://archimer.ifremer.fr/doc/00690/80240/83315.pdf
LA English
DT Article
CR MAGIC
BO Pourquoi pas ?
DE ;Northeast Brazil;Crustal structure;Lower continent a l crust;Proto-oceanic;Wide-angle seismic;Para-maranhao;barreirinhas margin;Equatorial atlantic ocean;Passive margin
AB The Pará-Maranhão/Barreirinhas margin, North Brazil, is a pull-apart passive margin, with two strike-slip borders, formed during the opening of the Equatorial Atlantic Ocean during Cretaceous time. Its geometry and evolution are speculative due to the lack of information on the crustal structure and the crustal nature. We present here the E-W profiles of the MAGIC (Margins of brAzil, Ghana and Ivory Coast) deep seismic experiment, a joint project between French and Brazilian universities, research institutes and the industry. Fifty-six Ocean Bottom Seismometers (OBS) and a 4.5 seismic streamer were deployed at sea along 2 of the 5 MAGIC profiles. One profile was extended onshore by installing 8 land stations. We perform forward modelling through combined interpretation of the multichannel seismic and of the main reflected and refracted of these phases recorded by the OBSs. The final P-wave velocity models reveal distinct structural domains from onshore Brazil towards the Atlantic Ocean characterized by variations of the crustal thicknesses and velocities: (1) an unthinned continental crust below the São Luís Craton, where the crust is 33 km thick, (2) a 60 km wide necking domain below the Ilha de Santana Platform; (3) offshore, east of the continental slope, a 10 km-thick deep sedimentary basin underlain by a 5 km thick crust with velocity of 6.2–6.9 km/s that we interpret as an exhumed lower continental crust, on the top of an Anomalous Velocity Layer (AVL) probably made of intrusions of mantle-derived melts into the lower continental crust, or a mixture of them; (4) eastwards, the limit of the previous domain is marked by NW-SE aligned volcanoes and the disappearance of the AVL. The sedimentary succession becomes thinner (6 km) overlaying a proto-oceanic crust characterized by seismic velocities higher than “normal” oceanic crust in its upper part, but in continuity with the velocity described in the previous domain; (5) followed by a more characteristic but thin oceanic crust. The middle/lower continental crust seems not only to have a crucial role in the genesis of the passive margin but also to be involved in the genesis of the first oceanic crust. The passage to a typical oceanic crust seems to have occurred progressively by steps: first in the deeper layer by the setup of more and more intrusions of mantle-derived melts at the base of the crust or mixture of exhumed lower crust and mantle, producing a domain of proto-oceanic crust, then by the emplacement of an upper 1-2 km-thick layer with typical oceanic characteristics. 
PY 2021
PD OCT
SO Journal Of South American Earth Sciences
SN 0895-9811
PU Elsevier BV
VL 110
UT 000685120000001
DI 10.1016/j.jsames.2021.103322
ID 80240
ER

EF