@article{3185342,
    title = "The geology and mineralogy of the Stypsi porphyry Cu-Mo-Au-Re prospect,
Lesvos Island, Aegean Sea, Greece",
    author = "Voudouris, Panagiotis and Mavrogonatos, Constantinos and Melfos, and Vasilios and Spry, Paul G. and Magganas, Andreas and Alfieris, Dimitrios and and Soukis, Konstantinos and Tarantola, Alexandre and Periferakis, and Argyrios and Kolodziejczyk, Joanna and Scheffer, Christophe and and Repstock, Alexander and Zeug, Manuela",
    journal = "Ore Geology Reviews",
    year = "2019",
    volume = "112",
    publisher = "Elsevier",
    issn = "0169-1368",
    doi = "10.1016/j.oregeorev.2019.103023",
    keywords = "Porphyry-epithermal; Banded quartz veins; Gold; Re-rich molybdenite;
Lesvos; Greece",
    abstract = "The Stypsi Cu-Mo-Au-Re prospect, Lesvos island, is a shallow
porphyry-epithermal system hosted within a middle Miocene microgranite
porphyry, which was emplaced along NNE-, NW- and NE-trending structures,
within trachyandesites to trachydacites and felsic pyroclastics of the
Stypsi caldera. The mineralization comprises three stages: Stage I is
characterized by magnetite-actinolite +/- quartz in transitional and
banded quartz veins mostly developed within the microgranite and the
surrounding lavas related to calcic-potassic and propylitic alteration
of the host rocks. In the banded veins, quartz is botryoidal, suggesting
crystallization from a gel. Abundant vapor-rich inclusions in the bands
produce a dark grey to black color. Within the veins, magnetite,
chalcopyrite, bornite and native gold were followed in time by pyrite,
hematite, sphalerite and galena. Stage I mineralization was synchronous
and also postdates quartz formation in the veins, since it crosscuts
and/or fills vugs in the center of the veins. Sulfides are associated
with various combinations of K-feldspar, actinolite, epidote, chlorite,
and calcite gangue minerals. Pyrite-molybdenite-chalcopyrite (Stage II)
and late intermediate sulfidation epithermal veins (Stage III) overprint
earlier mineralization and alteration, and are associated with
sericite-calcite and sericite-kaolinite alteration of the porphyry
system and spatially associated lavas, respectively. Molybdenite is
widespread in the first two mineralization stages, with Re content
ranging from about 0.3 wt% in Stage I to 1.96 wt% in Stage H. A barren
silicic and advanced argillic (alunite-kaolinite) lithocap, is exposed
on top of the porphyry-style mineralization and is crosscut by
non-mineralized high-sulfidation epithermal chalcedony-barite veins.
Bulk ore analyses of surface samples from the Stypsi prospect yielded
values of up to 276 ppm Mo, 978 ppm Cu, up to 0.5 g/t Au, up to 3 g/t
Ag, and up to 70 ppb Pd and Re.
Fluid inclusion data indicate that the Stage I transitional and banded
quartz veins were deposited at 420 degrees C-530 degrees C and at
pressures up to 450 bars, from boiling hydrothermal fluids. The fluid in
the veins consists of a brine (40-61 wt% NaCl equiv) that coexists with
a lower salinity (6-14 wt% NaCl equiv) liquid phase and a low-density
vapor-rich fluid. Fluid inclusions in quartz of the Stage III
intermediate-sulfidation epithermal veins are characterized by
relatively low homogenization temperatures (231 degrees C-288 degrees C)
and salinities (up to 1.9 wt% NaCI equiv), which was the result of
subsequent dilution of the moderately saline fluids by circulating
meteoric water. This study verifies earlier works suggesting that
Au-enriched felsic magmas are able to crystallize Re-rich molybdenite,
and that Re may also be redistributed and enriched in later stages
during the deposition of porphyry-style mineralization. The Stypsi
prospect ressembles in many respects (e.g., Au grades, Cu/Mo ratios, the
Re content of molybdenite and the presence of ore-grade calcic-potassic
alteration), other porphyry Cu-MoRe-Au systems hosted in calc-alkaline
rocks in northeastern Aegean, Greece."
}