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The Kallianos Au-Ag-Te deposit in Evia Island (Greece) comprises sixteen syntaxial veins that intersect the schists and marbles of the Cycladic Blueschist Unit. The veins are filled with quartz-I and quartz-II, contain two hypogene ore stages (stages I and II), and are surrounded by infrequent muscovite-chlorite alteration zones. A magmatic origin is deduced for the Kallianos Au-Ag-Te mineralization, based on stable (S, C, Si, O, and H) and radiogenic (Pb, Sr, and Rb) isotopes, and fluid chemistry. The veins were deposited under pressures of ~ 220 to ~ 145 bars and temperatures of ~ 260 to 120 °C, from almost neutral H2Te-bearing hydrothermal fluids with a salinity of 2.2 to 15.8 wt.% NaCl equivalent. The telluride mineralization related to stage II was deposited at ~ 180 °C and evolved from Au- through Bi- to Ag-bearing tellurides. The vein minerals precipitated by simple cooling of almost non-reactive fluids that retained their initial magmatic signature. Taking into account the magmatic origin of the Kallianos deposit, we examine two proximal areas with granodioritic and leucogranitic intrusions similar to those associated with base and precious metal mineralization at Lavrion (~ 8.3 to ~ 7.1 Ma) and Tinos Island (~ 15 to ~ 13 Ma), as potential sources for the Kallianos fluids. Rb-Sr geochronology dating of the distal Kallianos Au-Ag-Te veins gave an age range of 8.1 to 7.6 Ma, implying that an overlapping and channelized hydrothermal system was active at the northern part of the Attico-Cycladic Metallogenetic Massif, utilizing the CBU detachment zones as fluid pathways. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

The newly discovered Shuangjianzishan Ag-Pb-Zn deposit, with 145 Mt of ore grading 128.5 g/t Ag (locally up to 32,000 g/t) and 2.2 wt % Pb + Zn, is located in the Great Hinggan Range metallogenic belt, northeastern China, and is currently the largest Ag deposit in Asia. The Ag-Pb-Zn orebodies occur as veins and are hosted primarily by a Permian slate. Recent drilling and core logging have identified a partially Mo mineralized granite porphyry intrusion adjacent to the Ag-Pb-Zn mineralized veins. This well-preserved magmatic-hydrothermal system therefore offers an excellent opportunity to evaluate the possible temporal and genetic relationship between Mo-mineralized porphyry intrusions and Ag-Pb-Zn veins. Three primary paragenetic stages of veining have been recognized: (I) early pyrite + quartz ± K-feldspar, (II) main ore sulfide + sulfosalt + quartz + calcite + sericite + chlorite ± epidote, and (III) post-ore quartz. The silver mineralization occurs mainly in the late paragenetic part of Stage II, in which canfieldite (Ag8SnS6), argentite (Ag2S) and freibergite [(Ag, Cu)12Sb4S13] are the dominant Ag-bearing ore minerals. A combination of ore mineral chemical and sulfur isotope geothermometers and physicochemical calculations suggest that the Ag-Pb-Zn mineralization took place at a temperature of 250° to 200°C, a pH of 6.7 to 5.6, and a ∆logfO2 (HM) of –2.4 to –8.7. A conspicuous enrichment of Sn and Se in the ore, which is represented by minerals containing the metal suite Ag-Pb-Zn-(Cu-Sn-Se-Sb), likely reflects a close genetic association between the base metal mineralization and a magma. In situ analyses show that the δ34S values of the sulfides and Ag-bearing sulfosalts from the Ag-Pb-Zn mineralized veins vary from –4.67 to +2.44%◦; the mean value is –2.11 ± 1.49%◦ (n = 77). The calculated mean δ34SH2S value of the ore-forming fluid is –1.65 ± 0.83%◦, which is indicative of a magmatic sulfur source. In situ Pb isotope analyses of the ore minerals yielded a narrow range of values (206Pb/204Pb of 18.243–18.310, 207Pb/204Pb of 15.503–15.563 and 208Pb/204Pb of 38.053–38.203, n = 59). Comparisons to corresponding isotopic data for the various rock units in the area and sulfides from nearby ore deposits indicate that there were substantial contributions of Pb and other metals (e.g., Ag and Zn) to the Shuangjianzishan deposit from a Mesozoic granitic source. Diorite-granodiorite dikes and dacite are crosscut by the Ag-Pb-Zn veins, and therefore, predate ore formation. These rock units have zircon U-Pb ages of 250.2 ± 2.0 and 133.9 ± 1.4 Ma, respectively. A concealed, weakly Mo mineralized granite porphyry intrusion proximal to the Ag-Pb-Zn mineralized vein system yielded zircon U-Pb ages of 134.4 ± 1.0 (MSWD = 0.1) and 134.4 ± 1.0 Ma (MSWD = 0.2), for coarse- and fine-grained facies, respectively. These ages are indistinguishable within the uncertainty from the zircon ages for the dacite and a granite intrusion ~2 km north of the mineralized veins, which has a weighted mean zircon U-Pb age of 135.2 ± 1.4 Ma (MSWD = 0.78). Molybdenite from three quartz vein/veinlet samples hosted by slate immediately above the porphyry intrusion yielded Re-Os model ages from 136.3 ± 0.9 to 133.7 ± 1.2 Ma and a weighted mean Re-Os age of 134.9 ± 3.4 Ma. Finally, three pyrite samples separated from the Ag-Pb-Zn mineralized veins have a weighted mean Re-Os model age of 135.0 ± 0.6 Ma. The very similar zircon U-Pb ages for the Mo-mineralized granite porphyry and dacite, and Re-Os ages for molybdenite and pyrite in the Shuangjianzishan ore district indicate that the Mesozoic magmatic-hydrothermal activity was restricted to a relatively short time interval (~136–133 Ma). They also suggest that the weakly Mo mineralized granite porphyry was likely the source of the fluids and metals that produced the Ag-Pb-Zn mineralization. Based on our geological observations and an extensive analytical database, a model is proposed for the genesis of the giant Shuangjianzishan Ag-Pb-Zn deposit in which the ore-forming fluid and its metals (i.e., Ag, Pb, and Zn) were exsolved during crystallization of the final phase of a composite granite porphyry intrusion. This fluid transported metals to the distal parts of the system, where they were deposited in preexisting faults or fractures created by the withdrawal of magma during the waning stages of the magmatic-hydrothermal event. The present study of the Shuangjianzishan Ag-Pb-Zn deposit and those of other magmatic-hydrothermal ore deposits in the region provide compelling evidence that the widespread Mesozoic felsic magmatism and Ag-Pb-Zn mineralization in the southern Great Hinggan Range took place in an intracontinental extensional tectonic setting, which was synchronous with, and spatially associated to, Paleo-Pacific slab rollback and lithospheric delamination and thinning. ©2020 Society of Economic Geologists, Inc.