Structure and evolution of volcanic plumbing systems in fold-and-thrust belts: A case study of the Cerro Negro de Tricao Malal, Neuquén Province, Argentina

DERYA GÜRER; GALLAND, OLIVIER; FERNANDO CORFU; LEANZA, HÉCTOR A.; SASSIER, CAROLINE

GEOLOGICAL SOCIETY OF AMERICA BULLETIN

GEOLOGICAL SOC AMER, INC

Lugar: Boulder; Año: 2015 p. 1 - 18

0016-7606

ABSTRACTMagma ascent and emplacement in compressionaltectonic settings remain poorlyunderstood. Geophysical studies show thatvolcanic plumbing systems in compressionalenvironments are vertically partitioned intoa deep level subject to regional compressionand a shallow level subject to local extension.Such vertical partitioning has also been documentedfor the plumbing systems of mud volcanoes,implying common, yet unresolved,underlying processes. In order to better constrainthe mechanisms governing this depthpartitioning of emplacement mechanisms,we studied the structure and evolution of theCerro Negro intrusive complex emplaced inthe Chos Malal fold-and-thrust belt in thefoothills of the Neuquén Andes, Argentina.The Cerro Negro intrusive complex consistsof sills and N-S?striking dikes that crosscutthe sills. The most prominent structures inthe study area are N-S?trending folds, andboth E- and W-vergent thrusts. We providenew U-Pb ages of 11.63 ± 0.20 Ma and11.58 ± 0.18 Ma for sills and 11.55 ± 0.06 Mafor a dike, which show that the Cerro Negrointrusive complex was emplaced in a shortperiod of time. Our ages and field observationsdemonstrate that the emplacementof the Cerro Negro intrusive complex wascoeval with the tectonic development of theChos Malal fold-and-thrust belt. This impliesthat the dikes were emplaced perpendicularto the main shortening direction. The systematiclocations of the dikes at the anticlinalhinges suggest that their emplacement wascontrolled by local, shallow stresses relatedto outer-arc stretching at the anticlinal hinge.We conclude that folding-related outer-arcstretching is one mechanism responsible forthe vertical partitioning of igneous plumbingsystems in compressional tectonic settings.I