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
✍ Scribed by Arias; Corretgé; Villa
- Book ID
- 104463204
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 278 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0954-4879
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✦ Synopsis
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.