INVESTIGADORES
FOLGUERA TELICHEVSKY Andres
artículos
Título:
Geochemical and tectonic evolution of Late Cretaceous to early Paleocene magmatism along the Southern Central Andes (35-36°S)
Autor/es:
IANNELLI, SOFÍA B.; FENNELL, LUCAS M.; LITVAK, VANESA D.; LUCÍA, FERNÁNDEZ PAZ; ALFONSO, ENCINAS; ANDRÉS, FOLGUERA
Revista:
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Año: 2018
ISSN:
0895-9811
Resumen:
Late Cretaceous-early Paleocene magmatism at Southern Central Andes is represented by incomplete andnot well-preserved outcrops. A recent U-Pb age from a volcano-sedimentary sequence in the southernAndes of Mendoza province (35300S) led to identify Late Mesozoic-Early Cenozoic magmatism, whichwas not previously registered. We focus on the petrological and geochemical characterization of thissequence, informally named as Los Angeles Unit (67 Ma). This magmatic association comprises basalticand andesitic lava flows interbedded with volcanic breccias and lithic sandstones; all of them intruded bysubvertical basaltic dykes. Geochemically, the volcanic rocks are mainly tholeiitic with an arc-likesignature and high LILE relative to HFSE content. A general enrichment in incompatible elements isseen towards the upper and younger lava flows, associated with a more alkaline character in theyoungest ones. A regional comparison among Los Angeles Unit and other Late Cretaceous-Paleocene arcmagmatic series along the Southern Central Andes (35-41S) shows that the studied sequence has aweaker arc-like signature and less slab-fluid influence than in coeval southern units. This contrastinggeochemical behavior is proposed to be a consequence of the subduction of the Farallon-Aluk spreadingridge beneath the studied latitudes (35300S) at ~70 Ma. Thus, the enrichment seen along the volcanicsequence together with the alkaline-like signature seen in the younger volcanic levels of Los Angeles Unitwould be related to the subduction of anhydrous oceanic crust and potentially the incipient developmentof a slab window. Similar geochemical features are seen to the south in the magmatic expressions of thenorthern Eocene Pilcaniyeu Belt outcrops (~40S; 44 Ma), as they show a limited arc-like signature andan intraplate-like composition. The segmented geometry of the Farallon-Aluk spreading ridge and itsprogressive migration from north to south is considered to be the main cause of the development ofcontrasting magmatic associations during time and space.