Mantle-drip magmatism beneath the Altiplano-Puna plateau, central Andes

Abstract

Convective removal of continental lithospheric roots has been postulated to be the primary mechanism of recycling lithospheric mass into the asthenosphere under large plateaux such as the Altiplano-Puna in the central Andes. Convective instabilities are especially likely to develop where there is extensive intermediate arc-like magmatism in the upper plate, as the residual masses complementing these magmatic products are typically denser than the underlying mantle. Mafi c volcanic rocks erupted on the central Andean Altiplano-Puna plateau during the past 25 m.y. contain evidence of this process. Here we use equilibration temperatures, age data, and geochemical constraints--primarily based on transition metals--to show that the most important source materials by mass for this mantle-derived magmatism are pyroxenites from the lower parts of the lithosphere, with only minor contributions from mantle peridotite. Pyroxenites are denser than typical upper mantle whether they are garnet bearing or not, and are therefore likely to contribute to destabilizing parts of the continental lithosphere. The pattern of melting is consistent with the process of foundering/dripping of small-scale (<50 km diameter) density anomalies in the lithosphere, where mafi c volcanic fi elds on the plateau represent the manifestations of individual drips.

40Ar-39Ar geochronology and petrogenesis of postcollisional trachytic volcanism along the İzmir-Ankara-Erzincan Suture Zone (NE, Turkey)*

“…The generation of these orientations was probably controlled by the extensional tectonics active along the whole scale of the Central and Eastern Pontides throughout the Middle Eocene time interval (Yilmaz et al, 1997a;Keskin et al, 2008;Arslan et al 2013). The generation of this extensional phase is interpreted as extensional collapse of the thickened continental crust along the IAESZ (Topuz et al, 2011); hence, similar extensional tectonics can also be triggered by delamination and lithospheric removal processes, which are exemplified in many regions worldwide (Sierra Nevada: Elkins-Tanton and Grove, 2003; Central Andes: Ducea et al, 2013).…”

Geochemistry and40Ar/39Ar geochronology of lavas from Tunupa volcano, Bolivia: Implications for plateau volcanism in the central Andean Plateau

“…10 and 6 Ma (Garzione et al, 2006) is controversial (e.g., Barnes and Ehlers, 2009), the removal of large amounts of mantle lithosphere has been implicated in the generation of the voluminous ignimbrites beneath the volcanic centers of Los Frailes and Gálan (Kay et al, 1994;Myers et al, 1998). Melting accompanying such large-scale foundering events may be dominated by asthenospheric upwelling, whereas the removal of smaller (50-1 km) blocks may result in the heating, dehydration, and melting of the mantle lithosphere, producing the smaller-volume, discrete episodes of central Andean Plateau magmatism (Drew et al, 2009;Ducea et al, 2013).…”

“…Based largely on seismic studies that suggest a dominantly felsic crustal composition and lower than expected thicknesses of mantle lithosphere in this region of intense crustal shortening (Whitman et al, 1996;Myers et al, 1998;Beck and Zandt, 2002;Yuan et al, 2002;McQuarrie et al, 2005), many researchers have argued for an important role for density-driven removal (delamination) of varying amounts of the mafic lower crust and mantle lithosphere beneath the central Andes. Although a magmatic response to lithospheric removal is generally expected in orogenic zones such as the central Andes (e.g., Kay, 1991, 1993;Elkins-Tanton, 2005), the petrogenetic sources and melting triggers are a matter of considerable debate (Kay et al, 1994;Davidson and de Silva, 1995;Hoke and Lamb, 2007;Jiménez and López-Velásquez, 2008;Drew et al, 2009;Kay and Coira, 2009;Ducea et al, 2013). In this study, we present new 40 Ar/ 39 Ar and whole-rock elemental data for the composite rear-arc Tunupa volcano of the Bolivian Altiplano, and we evaluate these data within the context of regional plateau volcanism.…”

Crustal deformation induced by mantle dynamics: insights from models of gravitational lithosphere removal

“…Houseman et al 1981;Kay & Kay 1993;Ducea & Saleeby 1996;Poudjom Djomani et al 2001;Jull & Kelemen 2001;Richards 2003;Saleeby et al 2003). On the basis of seismic tomography images, sedimentation records, magmatic history and other observations, lithosphere removal is inferred to have occurred in a number of regions, such as the Puna Plateau in South America (Ducea et al 2013), the Tien Shan orogen in Asia (Houseman & Molnar 2001) and the southern Appalachian orogen in North America (Biryol et al 2016).…”