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Pathways and distances of fluid flow during low‐grade metamorphism: evidence from pyrite deposits of the Cameros Basin, Spain
Author(s) -
AlonsoAzcárate,
Rodas,
Bottrell,
Raiswell,
José Ignácio Velasco
Publication year - 1999
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1046/j.1525-1314.1999.00202.x
Subject(s) - metamorphism , geology , pyrite , geochemistry , sedimentary depositional environment , chlorite , sedimentary rock , metamorphic rock , diagenesis , structural basin , mineralogy , geomorphology , paleontology , quartz
New geochemical and sulphur isotopic data are presented for a number of pyrite deposits from the Late Jurassic–Early Cretaceous Cameros Basin, Spain. The deposits were formed at, or close to, the peak of metamorphism and are always related to sandstone units in the mainly metapelite sequence. Iron remained immobile and conservative, pyrite iron being derived by sulphidation of chlorite in the host metapelites. Reduced sulphur, however, was supplied from two external sources: thermochemical reduction of sulphate and release of S during metamorphism of sedimentary sulphides. These sources provided isotopically heavy and light S, respectively, with variation in pyrite isotopic composition between different deposits resulting from differences in their relative importance at each site. During metamorphism, the sandstone units acted as aquifers, carrying the sulphidic pore waters to locations where permeability provided by syn‐depositional fractures on a scale of 0.5–5 m allowed its interaction with the metapelites. Transport distances for sulphide during metamorphism were of the order of hundreds of metres.