New insights into petrogenesis of Miocene magmatism associated with porphyry copper deposits of the Andean Pampean flat slab,Argentina

作     者：Silvia I.Carrasquero Nora A.Rubinstein Anabel L.R.Gómez Massimo Chiaradia Dénis Fontignie Victor A.Valencia 

作者机构：Facultad de Ciencias Naturales y Museo Universidad Nacional de La Plata Instituto de Geociencias básicas aplicadas y ambientales de Buenos Aires (IgeBA) Departamento de Ciencias Geológicas Facultad de Ciencias Exactas y NaturalesUniversidad de Buenos-CONICET Department of Earth Sciences University of Geneva School of Earth and Environmental Sciences Faculty Washington State University 

出 版 物：《Geoscience Frontiers》 (地学前缘（英文版）)

年 卷 期：2018年第9卷第5期

页      面：1565-1576页

核心收录：

学科分类：07[理学] 

基　　金：funded by Universidad de Buenos Aires (UBA-Cy T 20020090100182) FonCyT, Argentina (PICT-2014-1280) 

主　　题：Porphyry copper deposits 

摘      要：The Paramillos de Uspallata mining district located in the backarc region of the Pampean flat-slab segment(28°-33°S) features porphyry-type deposits genetically associated with Middle Miocene volcanics. This mineralizing magmatism comprising hydrothermally altered(sodic-calcic, potassic and phyllic alteration) subvolcanic and pyroclastic rocks of andesite-basaltic andesite and dacite-rhyolite composition with a typical arc signature, represents the eastward broadening of the Farellones arc by ~17 Ma. Its geochemistry also reveals a residual mineralogy of amphibole ± garnet with limited plagioclase fractionation resulting in an adakitic signal; however, according to the isotopic data collected in our study, the contributions of MASH(melting-assimilation-storage-homogenization) processes in the acquisition of this signal cannot be *** the broadening of the Farellones arc and its residual mineralogy e typical of relatively deep magmatic chambers e are consistent with a slab shallowing and outcoming crustal thickening *** tectonic scenario could be interpreted as a result of an early effect of the Juan Fernandez Ridge collision that was further to the north by ~17 Ma. Our findings suggest that magmas were fertile for porphyry type deposits during the early stages of the slab shallowing.