The Miocene Magmatism in the Malargüe and Chos Malal Fold and Thrust Belts

LITVAK, VANESA D.; FOLGUERA, ANDRÉS; FERNÁNDEZ PAZ, LUCÍA; LITVAK, VANESA D.; FOLGUERA, ANDRÉS; FERNÁNDEZ PAZ, LUCÍA; IANNELLI, SOFÍA B.; IANNELLI, SOFÍA B.

Opening and Closure of the Neuquén Basin in the Southern Andes

Springer, Cham

Año: 2020; p. 449 - 465

Late Oligocene to Pliocene magmatism at the latitudes of Malargüe and Chos Malal fold and thrust belts, in the Neuquén Basin, is distributed from the mainAndean axis to the retroarc zone. While arc magmatism maintained relatively similarcompositional and geochemical features during late Oligocene to Pliocene times,major variations are seen in volcanic sequences developed in the retroarc zone, dueto the development of a shallowsubduction regime by mid-late Miocene times. Thus,late Oligocene-early Miocene period is characterized by an extensional regime thatconditioned mainly tholeiitic magmas in the main Andean axis and alkaline intraplatemagmas in the retroarc zone. Early-late Miocene marks a change to compressionaltectonics in the Andean margin. Main arc magmatism showed a change to clearerarc, calc-alkaline signature, while retroarc magmatism showed the progressing inputof slab-derived products as the shallow subduction regime triggered the eastwardmigration of the asthenospheric wedge. Thus, arc-derived lavas expanded into themid to far retroarc zone (~69° 30 to 68° 30)with arc-like andesitic to dacitic compositions.With the progressive influence of the shallow subduction regime, arc-derivedproducts reached almost 500 km away from the Chilean trench at 36° S by latestMiocene-Pliocene. By the middle Pliocene, re-steepening of the slabconditionedextensional tectonics that favored awidespread alkaline volcanism in the present-dayPayenia retroarc and rhyolitic calderas in the main arc zone. After 3.5 Ma, retroarcmagmatism at the latitudes of the Malargüe and Chos Malal fold and thrust belts lackof clear arc-related geochemical features.