The eruptive chronology of the Yucamane-Calientes compound volcano: A potentially active edifice of the Central Andes (southern Peru)

Co-auteur étrangerInternational audienceWe reconstruct the eruptive chronology of the Yucamane–Calientes compound volcano in southern Peru based on extensive fieldwork and a large dataset of geochronological (K-Ar, 40Ar/39Ar, U-Pb, and 14C) and geochemical (major and trace element) analyses. This compound volcano is composed of two edifices that have experienced discontinuous volcanic activity from the middle Pleistocene to the Holocene. The Calientes volcano has been constructed in four successive stages: Calientes I is composed of andesitic lava flows dated at ~500 ka. Subsequently, the Callazas ignimbrite (Calientes II stage) was emplaced ~160–190 ka, followed by the main cone-building stage (Calientes III) at ~130–100 ka. Finally, the Holocene Calientes domes were emplaced and represent the last eruptive products of this edifice. The Yucamane volcano has been constructed in three stages: Yucamane I consists of a succession of andesitic lava flows exposed at the base of the volcano that are older than 40 ka. Yucamane II (~36–30 ka) comprises a thick sequence of block-and-ash-flow deposits that represents an episode of dome growth predating the younger Yucamane cone (Yucamane III) built after 20–25 ka. During the Holocene, Yucamane vulcanian to sub-Plinian activity has emplaced tephra-fall and pyroclastic-density-current deposits. The most recent explosive eruptions occurred ca. 3000 BP and emplaced a tephra-fall and pumice-flow deposits. Most samples from Calientes volcano are andesites and dacites (60.1–67.7 wt% SiO2), while rocks from Yucamane volcano are basaltic-andesites to dacites (53.4–66.9 wt% SiO2). The rocks have a mineral assemblage of plagioclase, amphibole, biotite, orthopyroxene, clinopyroxene, olivine, and Fe-Ti oxides. The analyzed samples are categorized within a high-K, calc-alkaline series. Calientes volcano erupted mostly andesitic magmas, but its history is punctuated by rare eruptions of silica-rich magmas. In contrast, Yucamane volcano follows a different trend characterized by a gradual decrease in silica content through post-glacial time, from the large (VEI 3) sub-Plinian andesitic eruption of ~3 ka to moderate (VEI ≤ 2) vulcanian eruptions of basaltic-andesitic. On the basis of such recurrent and recent (Holocene), low-to-moderate explosive activity, Yucamane must be considered an active and potentially threatening volcano, which may affect the province of Candarave with ~8000 inhabitants