Premium
A new source of isotopically heavy sulphur in lode‐gold deposits of NW Spain: a batch volatilization process in the conversion of pyrite to pyrrhotite by contact metamorphism
Author(s) -
J. Arias,
Corretgé,
Igor M. Villa
Publication year - 1998
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 - 10.1046/j.1365-3121.1998.00181.x
Subject(s) - pyrite , pyrrhotite , geology , metamorphism , diagenesis , lode , metamorphic rock , geochemistry , volatilisation , sulfur , mineralogy , chemistry , metallurgy , materials science , organic chemistry
The conversion of pyrite to pyrrhotite is identified in this study as a new source of isotopically heavy sulphur in thermal domes. Contact metamorphism of a sequence of pyrite‐rich shales by the Penedela blind intrusion (NW Spain) causes the conversion of diagenetic pyrite to pyrrhotite at a temperature of 150 °C. This process occurred in a closed system with total consumption of the diagenetic pyrite and production of H 2 S‐rich fluids. The H 2 S liberated in this unidirectional reaction shows a relatively heavy δ 34 S, in agreement with a batch volatilization process. The mixture of this H 2 S‐rich fluids with derived sulphur from Lower Cambrian carbonates produced gold‐bearing pyrite at a temperature of 340 °C. The contribution from these two different sulphur sources was 86% and 14%, respectively. The metamorphic fluids migrated through permeable zones such as fractures and shear zones, producing a lode‐gold deposit.