Geochronology of the late Pliocene to recent volcanic activity in the Payenia

GUDNASON, J.; HOLM, P.; SOAGER, N.; LLAMBIAS, E.J.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2012 vol. 37 p. 191 - 201

0895-9811

Eighteen samples originating from monogenetic cones and larger complexes in the back-arc Payenia volcanic province, in Mendoza Argentina, have been dated by the 40Ar/39Ar method. Groundmass and plagioclase separates give plateau ages, ranging from 20.7
0.5 to 0.06
0.02 Ma. Payenia has been divided into six sub*elds based on the new and literature radiometric ages: Payún Matrú, Río Colorado, Llancanelo, and Nevado volcanic *elds, the Northern segment and the Andes retro-arc group. Fifteen samples are younger than 2.83 Ma and show correlation between geographic position and age. Eruption centres younger than 0.5 Ma are concentrated to the west of 69 Wwith few exceptions among new and literature data. This westward shift of activity supports the rollback theory for the subducting Nazca plate since the late Pliocene. Furthermore, a northward progression of volcanism on the San Rafael block from 2.8 Ma to around 0.5 Ma is recognized. We conclude that rollback was initiated in the southern part of Payenia in the early Pliocene and progressed >200 km northwards during the Pliocene-Pleistoceneperiod creating conditions for hydrous magma generation beneath the eastern part of Payenia. The long lived activity of the Payún Matrú complex is ascribed to the presence of a thermal anomaly in the underlying asthenosphere which could be plume-like.40Ar/39Ar method. Groundmass and plagioclase separates give plateau ages, ranging from 20.7
0.5 to 0.06
0.02 Ma. Payenia has been divided into six sub*elds based on the new and literature radiometric ages: Payún Matrú, Río Colorado, Llancanelo, and Nevado volcanic *elds, the Northern segment and the Andes retro-arc group. Fifteen samples are younger than 2.83 Ma and show correlation between geographic position and age. Eruption centres younger than 0.5 Ma are concentrated to the west of 69 Wwith few exceptions among new and literature data. This westward shift of activity supports the rollback theory for the subducting Nazca plate since the late Pliocene. Furthermore, a northward progression of volcanism on the San Rafael block from 2.8 Ma to around 0.5 Ma is recognized. We conclude that rollback was initiated in the southern part of Payenia in the early Pliocene and progressed >200 km northwards during the Pliocene-Pleistoceneperiod creating conditions for hydrous magma generation beneath the eastern part of Payenia. The long lived activity of the Payún Matrú complex is ascribed to the presence of a thermal anomaly in the underlying asthenosphere which could be plume-like.