Sr–Pb isotopes signature of Lascar volcano (Chile): Insight into contamination of arc magmas ascending through a thick continental crust

Abstract

In the Central Volcanic Zone of the Andean cordillera (CVZ), thickening of the continental crust 30 Ma ago led to the production of increasingly differentiated magmas. Better constrain on the interactions between ascending magmas and the thick continental crust are needed to understand the contamination processes and their implications on the geochemical diversity of arc magmas. Lascar volcano figures among the most active Quaternary volcano of the CVZ and yet geochemical studies on its volcanic products remain scarce. We lead major-, trace elements and Pb-Sr isotopes measurements on 10 Lascar samples representative of the different petrologic types (andesitic to dacitic) in order to better characterize the Pb-Sr isotopic signature and diversity of Lascar magmas yet defined based on only 8 samples.

Linking magmatic processes and magma chemistry during the post-glacial to recent explosive eruptions of Ubinas volcano (southern Peru)

“…Given the large uncertainties concerning the deep fractionation processes as well as the lower crustal compositions, we did not perform a quantitative analyse of these deep processes. However, this two-steps model has been applied on a regional Andean scale (Hildreth and Moorbath, 1988;Mamani et al, 2010;Blum-Oeste and Wörner, 2016;Ancellin et al, 2017) as well as to specific volcanic centres such as the Andahua monogenetic cones (Delacour et al, 2007), El Misti (Rivera et al, 2017), Ollagüe (Feeley and Davidson, 1994;Matioli et al, 2006), Nevados de Payachata (Davidson et al, 1990), and Lascar (Sainlot et al, 2020) in the CVZ; and Cotopaxi (Garrison et al, 2011) and Tungurahua volcanoes (Nauret et al, 2018) in the NVZ.…”

Geochronological evolution of the potentially active Iliniza Volcano (Ecuador) based on new K-Ar ages

“…In fact, the trace element contents of these units were unable to be reconciled with a parental melt with NS-I composition through a single fractional crystallization process, thus, implying the occurrence of an additional parental melt and a mixing process involving both magmas. The petrogenetic processes related to the origin of such silica-rich magmas are widely discussed as they could be produced by several processes including partial melting of the subducted slab and the metasomatism of the mantle wedge caused by the derived silicate melts (e.g., Bourdon et al, 2003;Samaniego et al, 2005Samaniego et al, , 2010Hidalgo et al, 2007Hidalgo et al, , 2012, crustal melting and/or assimilation of the lower crust (Garrison and Davidson, 2003;Garrison et al, 2006;Sainlot et al, 2020), and intra-crustal fractionation of the required high-pressure assemblages (e.g., Bryant et al, 2006;Chiaradia et al, 2009;Bellver-Baca et al, 2020).…”

Probing the hidden magmatic evolution of El Misti volcano (Peru) with the Pb isotope composition of fumaroles

“…A major outcome of AFC is that the isotopic variations of continental arc lavas often correlate with the degree of differentiation (De Paolo, 1981). The isotopic record of AFC is particularly clear along the CVZ where Pb isotope variations are controlled by the assimilation of Pb-rich rocks from the locally thick continental basement (e.g., Tilton and Barreiro, 1980;Wörner et al, 1992;Mamani et al 2008;Kiebala, 2008;Sainlot et al, 2020a). At El Misti, the Assimilation-Fractional Crystallization process translates in a decrease of 206 (Tilton and Barreiro, 1980;Barreiro and Clark, 1984;Mamani et al, 2008;Kiebala, 2008).…”