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Boron isotope composition of melt inclusions from porphyry systems of the Central Andes: a reconnaissance study
Author(s) -
Wittenbrink Jens,
Lehmann Bernd,
Wiedenbeck Michael,
Wallianos Alex,
Dietrich Andreas,
Palacios Carlos
Publication year - 2009
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.2008.00863.x
Subject(s) - geology , porphyry copper deposit , geochemistry , boron , tin , seawater , subduction , fluid inclusions , partial melting , inclusion (mineral) , quartz , melt inclusions , crust , mineralogy , paleontology , metallurgy , mantle (geology) , tectonics , oceanography , chemistry , materials science , organic chemistry
Quartz‐hosted melt inclusions from latite dykes of the Eocene El Salvador copper porphyry system in northern Chile display wide ranges in both boron concentration (15–155 p.p.m. B) and isotope composition (δ 11 B −7 to +12‰; n = 10), likely reflecting slab‐derived fluid input from seawater‐altered oceanic crust. In contrast, the major Miocene tin‐silver and tin porphyry systems in the Bolivian back‐arc region (Cerro Rico de Potosi, Chorolque, Llallagua) have distinctly different melt inclusion compositions with δ 11 B of −11.4 ± 2.7‰ ( n = 10), and magmatic boron enrichment up to several hundred p.p.m. B. The `seawater' signature in the El Salvador melt inclusions explains the oxidized mineral assemblage of the copper porphyry system, as opposed to the more reduced nature of the Bolivian tin porphyry systems, which reflect intracrustal melting of pelitic rocks.