IDEAN   23403
INSTITUTO DE ESTUDIOS ANDINOS "DON PABLO GROEBER"
Unidad Ejecutora - UE
artículos
Título:
Late Cretaceous arc rocks in the Andean retroarc region at 36.5°S: Evidence supporting a Late Cretaceous slab shallowing
Autor/es:
SPAGNUOLO, MAURO G.; FOLGUERA, ANDRES; LITVAK, VANESA D.; ROJAS VERA, EMILIO; RAMOS, VICTOR A.
Revista:
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Amsterdam; Año: 2012 p. 44 - 56
ISSN:
0895-9811
Resumen:
This work is focused in a group of subvolcanic bodies and lava domes
located in the retroarc region of the southern Central Andes in an area
between 35.5 and 37.5S, whose age and composition were poorly
constrained. These bodies are aligned, parallel to the Andean orogenic
front some 150 km east of the Present arc front. These rocks had
initially been assigned to the Neogene, but new Ar/Ar ages here
presented indicate a Late Cretaceous age. Moreover, their chemistry
reflects a linkage with the asthenospheric wedge, with weakly evolved
arc signature. This imposes a new interpretation of the tectonic setting
for these latitudes. When compared Late Cretaceous arc rocks with
Neogene ones some similarities and differences are found. Partially
superimposed along this segment of the Andes, a Neogene shallow
subduction setting had been proposed in the area. In this context we
compare these new identified centers with other nearby of Late
Cretaceous age, as well as with arc-related Neogene volcanic rocks. Our
analysis showed that these centers may have evolved under different
conditions in relation to the slightly older ones located immediately to
the southwest and to the younger ones (Late OligoceneeEarly Miocene)
found in this segment These volcanic centers may constitute the
westernmost Late Cretaceous arc front emplaced over the eastern slope of
the Andes in coincidence with a volcanic gap during the latest
Cretaceous/Eocene times time in the adjacent Chilean sector at these
latitudes. The occurrence of two shallow subduction episodes along the
same segment, associated with two definite cycles of crustal thickening
at the time of foreland arc expansion is discussed.