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Isotope Geochemistry of the Pb‐Zn‐Ba(‐Ag‐Au) Mineralization at Triades‐Galana, Milos Island, Greece
Author(s) -
Marschik Robert,
Bauer Tobias,
Hensler AnaSophie,
Skarpelis Nikos,
Hölzl Stefan
Publication year - 2010
Publication title -
resource geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 43
eISSN - 1751-3928
pISSN - 1344-1698
DOI - 10.1111/j.1751-3928.2010.00139.x
Subject(s) - geology , sphalerite , galena , geochemistry , hydrothermal circulation , isotopic signature , igneous rock , molybdenite , pyrite , mineralization (soil science) , sericite , mineralogy , isotope geochemistry , seawater , fluid inclusions , stable isotope ratio , isotope , oceanography , physics , quantum mechanics , seismology , soil science , soil water
The Pb‐Zn‐Ba(‐Ag‐Au) mineralization in the Triades and Galana mine areas is hosted in 2.5–1.4 Ma pyroclastic rocks, and structurally controlled mostly by NE‐SW or N‐S trending brittle faults. Proximal pervasive silica and distal pervasive sericite‐illite alteration are the two main alteration types present at the surface. The distribution of mineralization‐alteration in the district suggests at least two hydrothermal events or that hydrothermal activity lasted longer at Galana. The Sr isotope signature of sphalerite and barite ( 87 Sr/ 86 Sr = 0.709162 to 0.710214) and calculated oxygen isotope composition of a fluid in equilibrium with barite and associated quartz at temperatures of around 230°C are suggestive of a seawater hydrothermal system and fluid/rock interaction. Lead isotope ratios of galena and sphalerite ( 206 Pb/ 204 Pb from 18.8384 to 18.8711; 207 Pb/ 204 Pb from 15.6695 to 15.6976; 208 Pb/ 204 Pb from 38.9158 to 39.0161) are similar to those of South Aegean Arc volcanic and Aegean Miocene plutonic rocks, and compatible with Pb derived from an igneous source. Galena and sphalerite from Triades‐Galana have δ 34 S VCDT values ranging from +1 to +3.6‰, whereas barite sulfate shows δ 34 S VCDT values from +22.8 to +24.4‰. The sulfur isotope signatures of these minerals are explained by seawater sulfate reduction processes. The new analytical data are consistent with a seawater‐dominated hydrothermal system and interaction of the hydrothermal fluid with the country rocks, which are the source of the ore metals.