Across-arc geochemical variations in the Southern Volcanic Zone, Chile (34.5–38.0°S): Constraints on mantle wedge and slab input compositions

Abstract

31 32Crustal assimilation (e.g. Hildreth and Moorbath, 1988) and/or subduction erosion (e.g. Stern, 33 1991; Kay et al., 2005) are believed to control the geochemical variations along the northern 34 portion of the Chilean Southern Volcanic Zone. In order to evaluate these hypotheses, we present 35 a comprehensive geochemical data set (major and trace elements and O-Sr-Nd-Hf-Pb isotopes) 36 from Holocene primarily olivine-bearing volcanic rocks across the arc between 34.5-38.0°S, 37 including volcanic front centers from Tinguiririca to Callaqui, the rear arc centers of Infernillo 38Volcanic Field, Laguna del Maule and Copahue, and extending 300 km into the backarc. We also 39 present an equivalent data set for Chile Trench sediments outboard of this profile.

Evolution of the northwestern margin of the Basin and Range: The geology and extensional history of the Warner Range and environs, northeastern California

“…In addition, the Sr-, Nd-, Hf-, and Pb-isotope compositions of the mantle wedge are important factors in constraining the contribution of the mantle melt flux to the arc magmas in balance with the slab-liquid flux fractions of SED, AOC, and MwP (Jacques et al, 2013;Jacques et al, 2014;Kimura et al, 2010;. The estimation of the mantle composition (Table 3) is usually based on the isotope composition of a backarc basin basalt (BAB) (Kimura et al, 2010; or a basalt unaffected by the slab component of an arc .…”

“…The ABS3 and ABS4 models have been applied to NE and SW Japan in addition to the infant stage and present-day Izu-Bonin Arc Kimura et al, 2010;Li et al, 2013). The applications have been recently extended to the Kamchatka Arc (Portnyagin et al, 2015), Southern Chile Arc (Jacques et al, 2013;Jacques et al, 2014), New Zealand Arc (Rooney and Deering, 2014), ancient Mediterranean subduction systems (Beccaluva et al, 2013;Mattioli et al, 2012), and Earth's ancient subduction systems back to the Archean (3.5 Ga) (Kimura et al, 2016). This paper presents a description of the newly refined ABS5 model and its applications to cold NE Japan, hot SW Japan, and infant Izu-Bonin arcs.…”

Copahue Volcano and Its Regional Magmatic Setting

“…The Llaima and Tolhuaca samples have high New, analyzed at UCSC around the same time as results presented in Todd et al (2011). Analytical methods and performance provided therein c Varekamp et al (2006); Analytical methods and performance provided therein d Varekamp et al (2010); Analytical methods and performance provided therein e Sample and analyses from Jacques et al (2013) Ba/Nb and a deep negative Nb anomaly, with the Callaqui samples at lower Ba/Nb. With increasing depth to the Benioff zone, the Nb anomaly becomes less negative whereas the Ba/Nb values decrease to 40-90 for the Copahue rocks.…”

“…The overall rock chemistry and isotope compositions in this section of the Andes arc point to the usual source mixture of subducted Pacific Ocean sediment (PDS) and MORB type mantle (0.5-3 % bulk sediment mixing), with an additional low 206 Pb/ 204 Pb component in some magmas. This third component has EM1 characteristics and may represent the continental lithospheric mantle, lower crust, or other EM1-type mantle domains (Varekamp et al 2010;Soager et al 2013;Jacques et al 2013Jacques et al , 2014.…”

“…A small young cone occurs NE of Copahue (Troncon) and further to the northeast, the volcanoes Tromen and Domuyo are found, surrounded by many small lava flows and cinder cones (Zareski 2014). Some studies (Jacques et al 2013(Jacques et al , 2014 have documented regional cross arc trends over the Andes between 36°and 39°S, from the volcanic front volcanoes in Chile, through Copahue/Caviahue, to the back arc basalts all the way in the Payenia province, a more cratonic domain of volcanism (Soager et al 2013).…”