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Anhydrite-bearing andesite and dacite as a source for sulfur in magmatic-hydrothermal mineral deposits

journal contribution
posted on 2023-05-16, 22:05 authored by Chambefort, I, Dilles, JH, Kent, AJR
Magmatic anhydrite from andesites and dacites occurs as inclusions in high- and low-aluminum amphibole and pyroxene and indicates that sulfate-saturated magmas spanned a period of six million years at Yanacocha, Peru. Magmatic anhydrite from Yanacocha and other sites is characterized by light rare earth element - enriched patterns and elevated strontium contents distinct from magmatic-hydrothermal anhydrite. Petrologic arguments suggest that the hydrous and oxidized Yanacocha magmas contained more than ∼1000 ppm sulfur both dissolved in the melt and as a separate sulfate phase, which is sufficient to provide all the sulfur for the genetically related giant sulfur-rich Yanacocha epithermal gold deposits. High-aluminum amphiboles contain unusual anhydrite with wormy and amoeboidal textures, which are tentatively interpreted to represent trapping of an immiscible CaSO4-water melt together with sulfur-rich apatite at a temperature of ∼950 °C and a water pressure >3 kbar: Such unusually sulfate-rich magmas may be required to produce sulfur-rich magmatic-hydrothermal mineral deposits. © 2008 The Geological Society of America.

History

Publication title

Geology

Volume

36

Issue

9

Pagination

719-722

ISSN

0091-7613

Department/School

School of Natural Sciences

Publisher

Geological Society of America

Place of publication

United State

Repository Status

  • Restricted

Socio-economic Objectives

Precious (noble) metal ore exploration

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