Multistage alteration, mineralization and ore–forming fluid properties at the Viper (Sappes) Au–Cu–Ag–Te ore body, W. Thrace, Greece.

Abstract

The mineralogy of ore and hydrothermal alteration of the high-sulfidation enargite–Au–Ag–Te Viper (Thrace) orebody, and fluid inclusions, were studied in drillcore samples. The hydrothermal system has evolved through several stages from pre-ore advanced argillic I+vuggy silica alteration, ore-stage advanced argillic II+vuggy silica alteration and silicification that has developed to argillic alteration (sericite)+silicification through pH increase, and a return to acid conditions as crosscutting post-ore advanced argillic alteration III+silicification. Ore is characterized by early barren pyrite I corroded by: (i) enargite–Au± complex Pb–Bi–Cu sulfosalts, tellurides and selenides, coexisting with euhedral quartz, and (ii) zoned pyrite II distinguished by anomalous concentrations of Au, Cu, As, Te, Bi, Pb, Se, within vuggy quartz. High-grade gold ore is also intergrown with late brecciacementing and vein-type epithermal-like banded quartz+ pyrite. These alteration and mineralization observations are consistent with the changing composition, water fugacity, and density of an expanding column of metal-laden magmatic vapor, combined with changes in structural permeability. Part of the enargite─Au─ quartz assemblages have been probably quenched from sulfosalt melt at high─temperatures (>575°C). End product of the enargite–sulfhide–silica crystallization sequence is the formation of high-grade epithermal quartz-gold colloformbanded ore during cooling and/or dilution/mixing down to ~200°C.

Trace Elements in Magnetite from the Pagoni Rachi Porphyry Prospect, NE Greece: Implications for Ore Genesis and Exploration

“…The argon cooling gas flow rate was set to 16 L/min. Before starting an analysis, the system was calibrated to a NIST 612 reference glass measuring 139 27 Al, 29 Si, 43 Ca, 4 5Sc, 49 Ti, 51 V, 53 Cr, 55 Mn, 59 Co, 60 Ni, 63 Cu, 66 Zn, 69 Ga, 85 were quantitatively analyzed using the NIST 612 glass as an external standard while stoichiometric Fe (97% wt.% FeO) was the internal standard, since total concentration of minor elements is <3 wt.% (cf. Milani et al [60]).…”

“…A number of porphyry style deposits has been recognized in the broader area with the most important of them being the Konos Hill [31,[46][47][48][49], the Pagoni Rachi [50][51][52], and the Maronia [53] Cu-Mo-Re-Au systems, as well as the recently discovered porphyry Mo prospect in the Aisymi-Leptokarya area [45,54]. Epithermal-style mineralization in the area include, among others, the important Viper [55] and Perama Hill [56] Au-Ag deposits, as well as the St. Philippos [51][52][53][54][55][56][57] and Pefka [58] polymetallic deposits that have been exploited in the past. [30]; Mavrogonatos et al, [31]).…”

Mineralogical Study of the Advanced Argillic Alteration Zone at the Konos Hill Mo–Cu–Re–Au Porphyry Prospect, NE Greece

“…Hydrothermal alteration and mineralization occurring in the Kassiteres-Sapes district have been well-studied [23][24][25][26]35,[52][53][54]. Advanced argillic-altered lithocaps have been recognized at a number of sites [23].…”

“…The Konos Hill lithocap is deficient of any primary sulfides due to extensive supergene oxidation; however, it hosts a low-grade Au mineralization (see Section 4.3). On the contrary, nearby lithocaps at Agios Demetrios, Scarp, Viper, and Agia Barbara host significant high-sulfidation epithermal, gold-enargite mineralization, which is generally found in the western part of the study area [22][23][24][25][55][56][57]. Advanced argillic alteration assemblages evolve downwards through a transitional zone of quartz + alunite + pyrophyllite + sericite into a typical sericite-rich assemblage, which is the most widespread type of hydrothermal alteration in the district.…”

“…In Greece, several advanced argillic alteration lithocaps have been identified [20,21]. The best-known example is in the Kassiteres-Sapes district [22][23][24], where advanced argillic alteration zones host significant, high-to-intermediate-sulfidation ores (e.g., the Viper Au-Cu-Ag-Te deposit [25]), which overprint or form laterally to porphyry-style mineralization [23,26,27]. Other examples include the Mavrokoryfi [28] and Melitena [29] prospects in the Thrace district, northeastern Greece, as well as the Fakos and Stypsi prospects on Limnos and Lesvos islands, respectively [30][31][32].…”