The Cenozoic History of Volcanism and Hydrothermal Alteration in the Central Andean Flat-Slab Region: New ⁴⁰Ar-³⁹Ar Constraints from the El Indio–Pascua Au (-Ag, Cu) Belt, 29°20′–30°30′ S

Abstract

Ninety-three new 40 Ar-39

Geodynamic controls on the contamination of Cenozoic arc magmas in the southern Central Andes: Insights from the O and Hf isotopic composition of zircon

“…This is a particular problem in the southern Central Andes where some of the arc magmatic rocks (e.g., the Tilito Formation) have been affected by hydrothermal alteration (Bissig et al, 2001(Bissig et al, , 2003Kay and Mpodozis, 2001;Charchaflié et al, 2007;Litvak et al, 2007). A solution is to conduct high resolution, in-situ oxygen and hafnium isotopic analysis of the robust accessory mineral zircon and combine this with high resolution U-Pb dating and detailed cathodoluminescence imaging.…”

Southern Central Andes Neogene magmatism over the Pampean Flat Slab: implications on crustal and slab melts contribution to magma generation in Precordillera, Western Argentina

“…Afterward and due to the shallowing of the subducted slab, volcanic activity was strongly reduced by Latest Miocene in the former main arc, with the emplacement of the rhyolitic tuffs from Vacas Heladas Ignimbrites as the last significant arc volcanism, with K-Ar, Ar/Ar and U-Pb ages ranging between 5.5 to 6.0 Ma (Ramos et al, 1987;Kay et al, 1991;Bissig et al, 2001;Kay and Mpodozis, 2002;Litvak et al, 2007;Jones et al, 2016).…”

“…This volcanic activity was coeval with the main volcanic arc developed at these latitudes, over the present-day Pampean f lat-slab region of Southern Central Andes. The geodynamic evolution of the Paleogene to Neogene main volcanic arc has been studied in the last years on the basis of chemical, petrographic and radiometric ages relationships of the involved volcanic units (Kay et al, 1991(Kay et al, , 1999Kay and Mpodozis, 2002;Bissig et al, 2001Bissig et al, , 2003Litvak et al, 2007;Litvak and Poma, 2005Jones et al, 2016); however, magmatic activity developed at the same latitudes but in a back arc position is less known. These deposits include a sedimentary and pyroclastic rock sequence known as Lomas del Campanario Formation (Wetten, 1975(Wetten, , 2005Contreras et al, 1990) and lava f lows related to shallow intrusives, named Miocene Intrusives and Tertiary Intrusives (Cardó and Díaz, 1999;Cardó et al, 2007;Llambías et al, 1990).…”

“…To do that, we compare Lomas del Campanario Formation with two sets of rocks: one representative of the main arc magmatism at the same latitude and the other one, the back arc rocks at southern Puna latitude. The volcanic sequences selected with this purpose are those contemporaneous to the ones cropping out at Valle del Cura area in Cordillera Frontal, San Juan, Province: Cerro de las Tórtolas, Tambo Formations and Vacas Heladas Ignimbrite (Kay et al, 1991;Bissig et al, 2001;Litvak et al, 2007;Jones et al, 2016) and Cerro Blanco in Puna Austral (Montero López et al, 2010).…”

Temporal variations in the influence of the subducting slab on Central Andean arc magmas: Evidence from boron isotope systematics

“…Melt inclusions were analysed as they are protected by the surrounding host phenocryst phase from the effects of post depositional alteration, such as hydrothermal alteration (common at this locality; e.g., Bissig et al, 2001), as well as from late stage processes occurring in the melt during magma ascent (e.g., Schiano, 2003;Schmitt et al, 2002;Sobolev, 1996). The obtained melt inclusion data is combined with U-Pb and Ar-Ar ages (Jones, 2014) to constrain changes in the influence of the subducting slab on the source of southern Central Andean arc magmas with time, and to evaluate the potential causes of flat-slab subduction.…”