Isotope Geochemistry of the Pb-Zn-Ba(-Ag-Au) Mineralization at Triades-Galana, Milos Island, Greece

Abstract

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 (

New boron isotopic evidence for sedimentary and magmatic fluid influence in the shallow hydrothermal vent system of Milos Island (Aegean Sea, Greece)

“…These sulfur and carbon isotopes are consistent with those in Nisyros Island that are considered to be derived from rhyodacite magma (Gilhooly et al, 2014;Marini et al, 2002). Abundant metallic vein mineralizations distributed around Milos Island have been classified as Kuroko-type, seawater derived, shallow submarine or hybrid volcanogenic massive sulfide types epithermal system (Kilias et al, 2001;Liakopoulos et al, 2001;Marschik et al, 2010;Naden et al, 2005;Vavelidis and Melfos, 1998). Previous studies have revealed that the equilibrated reaction temperatures of fluid inclusions in metal-rich barite from Milos Island ranging from 260 to 340°C and salinity of 2-6 wt% NaCl equivalent, reflecting possible mixing of magmatic-hydrothermal metal-bearing brine and seawater (Vavelidis and Melfos, 1998).…”

“…This might be attributed to a flux of slab-derived liquids from subducted sediments (Elliott et al, 2006;Lou et al, 2014;Teng et al, 2004;Tomascak et al, 2008). These episodic injections of magmatic fluid/volatiles are also prime candidates in the formation of abundant metallic vein mineralization, ranging from submarine to subaerial environments (e.g., Alfieris et al, 2013;Kilias et al, 2001;Liakopoulos et al, 2001;Marschik et al, 2010;Naden et al, 2005;Vavelidis and Melfos, 1998).…”

Prospectivity Mapping for Epithermal Deposits of Western Milos Using a Fuzzy Multi Criteria Evaluation Approach Parameterized by Airborne Hyperspectral Remote Sensing Data

“…Kaolinite is generally more common in the advanced argillic alteration mineralisation in the Triades-Galana and Kondaros areas whereas phyllic alteration, characterised by sericite, quartz and pyrite is restricted to the area around Triades-Galana. The Zn-Pb-(Ag) deposits at Triades and neighbouring Galana were mined initially for lead and zinc, and later for silver [41]. The minerals at Triades includes galena and sphalerite and were deposited in multiple stages [34].…”

“…For prospectivity mapping, epiclastic aprons associated with andesitic-dacitic lava domes were considered favourable for epithermal mineralisation [34,[38][39][40][41][42]. A Digital Elevation Model (DEM) and a slope layer were generated from a 1:50,000 contour map.…”

Abstracts

“…The mineralisation at Triades is largely of massive galena veins, containing the majority of the Pb (Marschik et al, 2010), with minor sphalerite and pyrite viewable in hand specimen. This is hosted in brittle faults within a heavily baritised breccia, often showing evidence of repeated or continuous deposition of minerals (largely barite and quartz) from hydrothermal fluids.…”