Author(s):
Lourenço, Nuno 
; Pinto de Abreu, Manuel ; Madureira, Pedro ; Pinto Ribeiro, Luísa
Date: 2008
Persistent ID: http://hdl.handle.net/10174/2420
Origin: Repositório Científico da Universidade de Évora
Subject(s): EMEPC/G3 cruise; Azores and Great Meteor seamounts
Description
During May/June 2007, the Cruise EMEPC/Açores/G3/2007 was sailed aboard the
SV Kommandor Jack in the scope of Portuguese Program for the Extension of the
Continental Shelf. The Cruise, mainly focused on geological sampling, comprised a
1st leg lasting five days, at the Terceira rift zone and S. Jorge Island flank and a 2nd
leg which lasted twenty-four days at the Atlantis, Plato, Hyeres and Great Meteor
Seamounts located south of the Azores region, in the Mid-Atlantic Ridge off-axis
domain. A multidisciplinary national team of 19 scientists, from 7 Portuguese Universities
and National Research Institutes participated in the cruise. Disciplines involved
comprised geology, geophysics, geochemistry, hydrography, biology, environmental
chemistry and oceanography. Furthermore science outreach initiatives complemented
the cruise, as ship track and summary of operations have been published in a daily
basis on Google Earth for follow up by schools and general public.
The cruise comprised 2605 NM of surveying by EM120 swath bathymetry and
gravimetry, including two short systematic surveys, east of Terceira Island and at
the Great Meteor southern flank. Some magnetic data was also collected. Other sea
operations comprised sediment coring, micro and macro biology sampling and CTDrosettes
on the water column. The main objective of the cruise was to perform dredges
on seamounts and within the Azores rift zone. 48 dredge operations (67% with recoveries)
were performed and about 6 tons of material was collected.
Along axis in the Terceira rift, within clear Brunhes magnetic anomaly seafloor, very
fresh basalt samples along with highly altered basaltic breccias from possible monogenic
volcanic cones were recovered. These data implies that accretion processes are
highly discontinuous spatial and temporally within this ultra-slow rift system. Within
the seamounts, the recovered lithotypes are carbonate rocks (s.l), sedimentary and
volcanic breccias, as well as generally altered basaltic rocks. Considering the depth
range of individual dredging operations and the nature of the recovered materials, the
seamounts seem to present a fairly constant geological cross section, ranging from
massive basalts near the relief base, followed by a wide zone dominated by volcanic
and/or breccias. The tops of Irving, Hyeres and Great Meteor are defined by a shallow
flat were some wave rounded carbonate cobbles were recovered, therefore corroborating
marine abrasion, as suggested in other studies.
The data recovered in the different disciplines is presently being analysed. Some results
from major and trace element geochemistry have however been achieved and are
presented in Madureira et al and Ribeiro et al. abstracts (this meeting).
