Mineralogical, Petrographical and Geochemical Study of the Stypsi Porphyry-Epithermal System, Lesvos Island, Greece

Postgraduate Thesis uoadl:2887659 344 Read counter

Unit:
Κατεύθυνση Μεταπτυχιακό Δίπλωμα
Library of the School of Science
Deposit date:
2019-12-16
Year:
2019
Author:
Periferakis Argyrios
Supervisors info:
Παναγιώτης Βουδούρης, Καθηγητής, ΕΚΠΑ, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος
Ανδρέας Μαγγανάς, Καθηγητής, ΕΚΠΑ, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος
Βασίλειος Μέλφος, Αναπληρωτής Καθηγητής, ΑΠΘ, Τμήμα Γεωλογίας
Original Title:
Mineralogical, Petrographical and Geochemical Study of the Stypsi Porphyry-Epithermal System, Lesvos Island, Greece
Languages:
English
Translated title:
Mineralogical, Petrographical and Geochemical Study of the Stypsi Porphyry-Epithermal System, Lesvos Island, Greece
Summary:
Lesvos Island comprises Lower Miocene, post-collisional volcanic to subvolcanic rocks with shoshonitic affinities overlying a metamorphic basement. The Stypsi porphyry-Cu-Mo-Au prospect is genetically related to a microgranite porphyry, which has intruded into trachyandesitic lavas of the Stypsi caldera. It comprises a stockwork of porphyry-style, black banded quartz- and quartz-actinolite veinlets associated with Na-Ca alteration, and a sericite-carbonate overprint related to IS epithermal quartz-carbonate veins. At higher topographic levels, a lithocap also hosts porphyry-style veinlets. Molybdenite, magnetite, pyrite, chalcopyrite, sphalerite, galena, bismuthinite and fahlores, are the metallic minerals of the porphyry mineralization. EPMA data indicate extremely high Re contents (up to 1.92 wt. %) in molybdenite, and low to moderate Fe contents (from 0.26 to 4.74 wt. %) in sphalerite. Fluid inclusion studies demonstrate coexistence of liquid- and vapor-rich inclusions in association with NaCl-bearing inclusions in the veinlets, suggesting that boiling occurred during the mineralization. Homogenization temperatures range between 344° and 510° C and salinities reach up to 44 % eq. NaCl. Bulk ore analyses revealed up to 843 ppm Cu, up to 76 ppm Mo, up to 0.5 ppm Au, up to 339 ppm Pb, up to 815 ppm Zn, up to 10 ppm Se, up to 4 ppm Te and Bi, and up to 23 ppm Sn. Quartz recrystallization from a silica gel is evidenced by botryoidal textures within banded quartz veinlets, a feature already described from porphyry-Au deposits. The late IS epithermal overprint, in the form of milky quartz-carbonate veins is controlled by NNE-trending faults, and extends further northwards to Megala Therma epithermal deposit, where fluorite in the veins and Au-Ag-Te enrichment occur.
Main subject category:
Science
Keywords:
Lesvos Island, Stypsi-Megala Therma, porphyry-epithermal mineralization
Index:
No
Number of index pages:
0
Contains images:
Yes
Number of references:
614
Number of pages:
213
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