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标题：New insights into petrogenesis of Miocene magmatism associated with porphyry copper deposits of the Andean Pampean flat slab, Argentina
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作者：Silvia I. Carrasquero ; Nora A. Rubinstein ; Anabel L.R. Gómez 等
期刊名称：Geoscience Frontiers
印刷版ISSN：1674-9871
出版年度：2018
卷号：9
期号：5
页码：1565-1576
DOI：10.1016/j.gsf.2017.10.009
语种：English
出版社：Elsevier
摘要：AbstractThe 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 disregarded.Both the broadening of the Farellones arc and its residual mineralogy – typical of relatively deep magmatic chambers – are consistent with a slab shallowing and outcoming crustal thickening setting. This 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.Graphical abstractDisplay OmittedHighlights•New geochemical and isotopic data.•Middle Miocene mineralizing magmatism.•Adakitic signal resulting from amphibole ± garnet fractionation and MASH processes.•Slab shallowing geodynamic conditions.
关键词：KeywordsenPorphyry copper depositsPetrogenesisAdakitic signalBackarcCentral Andes