INVESTIGADORES
MARTINEZ DOPICO Carmen Irene
artículos
Título:
Crustal segments in the North Patagonian Massif, Patagonia: An integrated perspective based on Sm-Nd isotope systematics
Autor/es:
MARTÍNEZ DOPICO, C.I.; LÓPEZ DE LUCHI, M.G.; RAPALINI, A.E.; KLEINHANNS, I.
Revista:
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Año: 2011 vol. 31 p. 324 - 341
ISSN:
0895-9811
Resumen:
New insights on the Paleozoic evolution of the continental crust in the North Patagonian Massif are presented
based on the analysis of SmeNd systematics. New evidence is presented to constrain tectonic
models for the origin of Patagonia and its relations with the South American crustal blocks. Geologic,
isotopic and tectonic characterization of the North Patagonian Massif and comparison of the Nd parameters
lead us to conclude that: (1) The North Patagonian Massif is a crustal block with bulk crustal average ages
between 2.1 and 1.6 Ga TDM (Nd) and (2) At least three metamorphic episodes could be identified in the
Paleozoic rocks of the North Patagonian Massif. In the northeastern corner, Famatinian metamorphism is
widely identified. However field and petrographic evidence indicate a Middle to Late Cambrian metamorphism
pre-dating the emplacement of the ca. 475 Ma granitoids. In the southwestern area, are apparent
425e420 Ma (?) and 380e360 Ma metamorphic peaks. The latter episode might have resulted from the
collision of the Antonia terrane; and (3) Early Paleozoic magmatism in the northeastern area is coeval with
the Famatinian arc. Nd isotopic compositions reveal that Ordovician magmatism was associated with
attenuated crust. On the southwestern border, the first magmatic recycling record is Devonian. Nd data
shows a step by step melting of different levels of the continental crust in the Late Palaeozoic. Between 330
and 295 Ma magmatism was likely the product of a crustal source with an average 1.5 Ga TDM (Nd).
Widespread magmatism represented by the 295e260 Ma granitoids involved a lower crustal mafic source,
and continued with massive shallower-acid plutono volcanic complexes which might have recycled an
upper crustal segment of the Proterozoic continental basement, resulting in a more felsic crust until the
Triassic. (4) SmeNd parameters and detrital zircon age patterns of Early Paleozoic (meta)-sedimentary
rocks from the North Patagonian Massif and those from the neighboring blocks, suggest crustal continuity
between Eastern Sierras Pampeanas, southern Arequipa-Antofalla and the northeastern sector of the North
Patagonian Massif by the Early Paleozoic. This evidence suggests that, at least, this corner of the North
Patagonian Massif is not allochthonous to Gondwana. A Late Paleozoic frontal collision with the southwestern
margin of Gondwana can be reconcilied in a para-autochthonous model including a rifting event
from a similar or neighbouring position to its post-collision location. Possible Proterozoic or Early Paleozoic
connections of the NPM with the Kalahari craton or the western Antartic blocks should be investigated.