Pliocene-Quaternary deformation and magmatism at the southern margin of the Puna plateau, Argentine Andes

dc.contributor.advisorMarrett, Randall
dc.creatorBaldwin, Austin Kyle
dc.date.accessioned2021-02-02T20:43:21Z
dc.date.available2021-02-02T20:43:21Z
dc.date.issued2005
dc.description.abstractNew fault data and mapping of volcanic rocks from northwestern Argentina's Cordillera de San Buenaventura, a Pliocene-Quaternary, E-W trending volcanic range at the southern margin of the Puna plateau adjacent to the modern volcanic arc at 27°S, reveal numerous tectonomagmatic characteristics unique in the region. Faults in the Cordillera de San Buenaventura dominantly strike ENE-WSW, with lengths reaching at least 30-40 km. Fault motion, where measurable, has been normal, commonly with a right-lateral component. Some faults displace alluvium and dated Plio-Quaternary non-explosive lava domes and flows, intermediate in composition, with throws of 1-100 m, whereas other faults do not affect overlying volcanics. Previous studies in the surrounding southern Puna have reported Pliocene-Quaternary NNW-SSE extension along N-S to NNE-SSW striking right-slip faults commonly associated with volumetrically-minor mafic monogenetic cinder cones and flows. Explosive eruptions with intermediate compositions have also characterized the southern Puna during the Pliocene-Quaternary. Volcanics erupted during this time period in the Cordillera de San Buenaventura lack both mafic and explosive tendencies. The new data, combined with existing data, suggest that the Cordillera de San Buenaventura overlies a shallow magma chamber, which thermally weakened the upper crust and promoted the growth of the observed ENE-WSW striking normal and oblique-slip faults during the Pliocene-Quaternary. The new faults created right-stepping extensional transfers by linking preexisting NNE-SSW striking right-slip faults. Decreased horizontal stress at these transfers facilitated magma ascent from the underlying chamber. Periodic breaches of the magma chamber cupola by slip on faults prevented magmatic fluid accumulation and explosive eruptions. Mafic magma ascending beneath the Cordillera de San Buenaventura pooled in the shallow magma chamber, where it assimilated silica-rich crustal material and differentiated, eventually reaching the surface with an intermediate composition. In surrounding areas, where no shallow magma chamber existed, rising magmas reached the surface with mafic compositions. The high topography of the Cordillera de San Buenaventura may be the combined effect of mechanical doming by the shallow magma chamber, thermal uplift, isostatic elevation of an extensional transfer block, and local accumulation of Plio-Quaternary volcanicsen_US
dc.description.departmentEarth and Planetary Sciencesen_US
dc.format.mediumelectronicen_US
dc.identifier.urihttps://hdl.handle.net/2152/84576
dc.identifier.urihttp://dx.doi.org/10.26153/tsw/11555
dc.language.isoengen_US
dc.relation.ispartofUT Electronic Theses and Dissertationsen_US
dc.rightsCopyright © is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en_US
dc.rights.restrictionRestricteden_US
dc.subjectPlioceneen_US
dc.subjectQuaternaryen_US
dc.subjectDeformationen_US
dc.subjectMagmatismen_US
dc.subjectPuna plateauen_US
dc.subjectArgentinaen_US
dc.subjectAndesen_US
dc.titlePliocene-Quaternary deformation and magmatism at the southern margin of the Puna plateau, Argentine Andesen_US
dc.typeThesisen_US
dc.type.genreThesisen_US
thesis.degree.departmentGeological Sciencesen_US
thesis.degree.disciplineGeological Sciencesen_US
thesis.degree.grantorUniversity of Texas at Austinen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science in Geological Sciencesen_US

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