Raj. Trouw et al., Deformational evolution of a Cretaceous subduction complex: Elephant Island, South Shetland Islands, Antarctica, TECTONOPHYS, 319(2), 2000, pp. 93-110
New structural data from Elephant Island and adjacent islands are presented
with the objective to improve the understanding of subduction kinematics i
n the area northeast of the Antarctic Peninsula. On the island, a first def
ormation phase, D-1, produced a strong SL fabric with steep stretching and
mineral lineations, partly defined by relatively high pressure minerals, su
ch as crossite and glaucophane. D-1 is interpreted to record southward subd
uction along an E-W trench with respect to the present position of the isla
nd. A second phase, D-2, led to intense folding with steep E-W-trending axi
al surfaces. The local presence of sinistral C'-type sheer bands related to
this phase and the oblique inclination of the L-2 stretching lineations ar
e the main arguments to interpret this phase as representing oblique sinist
ral transpressive shear along steep, approximately E-W-trending shear zones
, with the northern (Pacific) block going down with respect to the southern
(Antarctic Peninsula) block. The sinistral strike-slip component may repre
sent a trench-linked strike-slip movement as a consequence of oblique subdu
ction. Lithostatic pressure decreased and temperature increased to peak val
ues during D-2, interpreted to represent the collision of thickened oceanic
crust with the active continental margin. The last deformation phase, D-3,
is characterised by post-metamorphic kink bands, partially forming conjuga
te sets consistent with E-W shortening and N-S extension. The rock units th
at underlie the island probably rotated during D-3, in Cenozoic times, toge
ther with the trench, from an NE-SW to the present ENE-WSW position, during
the progressive opening of the Scotia Sea. The similarity between the stra
in orientation of D-3 and that of the sinistral NE-SW Shackleton Fracture Z
one is consistent with this interpretation. (C) 2000 Elsevier Science B.V.
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