Detrital and volcanic zircon U-Pb ages from southern Mendoza (Argentina): an insight on the source regions in the northern part of the Neuquén Basin

MAXIMILIANO NAIPAUER; FELIPE TAPIA; JOSÉ MESCUA; MARCELO FARIAS; MARCIO PIMENTEL; VICTOR A. RAMOS

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2015 vol. 64 p. 434 - 451

0895-9811

The infill of theNeuquén Basin recorded the Meso-Cenozoic geological and tectonic evolution ofthe southern Central Andes being an excellent site to investigate how thepattern of detrital zircon ages varies trough time. In this work we analyze theU-Pb (LA-MC-ICP-MS) zircon ages from sedimentary and volcanic rocks related tosynrift and retroarc stages of the northern part of the Neuquén Basin. Thesedata define the crystallization age of the synrift volcanism at 223 ± 2 Ma(Cerro Negro Andesite) and the maximum depositional age of the original synriftsediments at ca. 204 Ma (El Freno Formation). Two different pulses of riftingcould be recognized according to the absolute ages, the oldest developed duringthe Norian and the younger during the Rhaetian-Sinemurian. The source regionsof the El Freno Formation show that the Choiyoi magmatic province was the mainsource rock of sediment supply. An important amount of detrital zircons withTriassic ages was identified and interpreted as a source area related to thesynrift magmatism. The maximum depositional age calculated for the TordilloFormation in the Atuel-La Valenciana depocenter is at ca. 149 Ma; as well as inother places of the Neuquén Basin, the U-Pb ages calculated in the LateJurassic Tordillo Formation do not agree with the absolute age of theKimmeridgian-Tithonian boundary (ca. 152 Ma). The main source region ofsediment in the Tordillo Formation was the Andean magmatic arc. Basementregions were also present with age peaks at the Carboniferous, Neoproterozoic,and Mesoproterozoic; these regions were probably located to the east in the SanRafael Block. The pattern of zircon ages summarized for the Late JurassicTordillo and Lagunillas formations were interpreted as a record of the magmaticactivity during the Triassic and Jurassic in the southern Central Andes. Awaning of the magmatism is inferred to have happened during the Triassic. Theevident lack of ages observed around ca. 200 Ma suggests cessation of thesynrift magmatism. The later increase in magmatic activity during the EarlyJurassic is attributed to the onset of Andean subduction, with maximum peaks atca. 191 and 179 Ma. The trough at ca. 165 Ma and the later increase in the LateJurassic could be explained by changes in the relative convergence rate in theAndean subduction regime, or by the shift to a more mafic composition of themagmatism with minor zircon fertility.