Geochronology of the late Pliocene to recent volcanic activity in the Payenia back-arc volcanic province, Mendoza Argentina

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• 作者：Jó ; nas Gudnason^a ; ^{jonasjard@simnet.is} ; Paul Martin Holm^a ; ^{paulmh@geo.ku.dk} ; Nina Sø ; ager^a ; ^ns@geo.ku.dk ; Eduardo J. Llambí ; as^b ; ^{llambias@cig.museo.unlp.edu.ar}
• 关键词：Payenia ; 40Ar/39Ar ; Geochronology ; Back-arc ; Mendoza ; Volcanism
• 刊名：Journal of South American Earth Sciences
• 出版年：2012
• 期刊代码：50_08959811
• 类别：ear
• 出版时间：August, 2012
• 卷：37
• 期：Complete
• 页码：191-201
• 文件大小：1148 K

摘要

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聽卤聽0.5 to 0.06聽卤聽0.02聽Ma. Payenia has been divided into six subfields based on the new and literature radiometric ages: Pay煤n Matr煤, R铆o Colorado, Llancanelo, and Nevado volcanic fields, the Northern segment and the Andes retro-arc group. Fifteen samples are younger than 2.83聽Ma and show correlation between geographic position and age. Eruption centres younger than 0.5聽Ma are concentrated to the west of 69掳聽W with 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聽Ma to around 0.5聽Ma is recognized. We conclude that rollback was initiated in the southern part of Payenia in the early Pliocene and progressed >200聽km northwards during the Pliocene-Pleistocene period creating conditions for hydrous magma generation beneath the eastern part of Payenia. The long lived activity of the Pay煤n Matr煤 complex is ascribed to the presence of a thermal anomaly in the underlying asthenosphere which could be plume-like.