Physicochemical conditions of deposition and origin of carbonate-hosted base metal sulfide mineralization, Thermes ore-field, Rhodope Massif, northeastern Greece

Kalogeropoulos, S. I.; Kilias, Stephanos P.; Arvanitidis, Nikos

doi:10.1007/s001260050048

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“…The Rhodope massif of northern Greece and southern Bulgaria hosts a range of metallic deposits: (1) carbonate replacement and skarn Pb-Zn(± Au ± Ag) mineralization (i.e., Madan and Thermes, Olympias, Madem Lakkos) (Kalogeropoulos et al, 1989(Kalogeropoulos et al, , 1996Nebel et al, 1991;Frei, 1995;Kilias et al, 1996;Kaiser-Rohrmeier et al, 2004;Marchev et al, 2005); (2) volcanic-hosted epithermal Pb-Zn-Cu(± Au-Ag) mineralization (i.e., Madjarovo); epithermal polymetallic (Ag, Te, Bi, Sn, Mo, base metals) and Au-Ag mineralization (i.e., Sappes, Perama Hill) (Shaw and Constantinides, 2001;Lescuyer et al, 2003;Voudouris et al, 2006;Rice et al, 2007), and porphyry Cu-Mo mineralization (Maronia) (Melfos et al, 2002); (3) sedimentary rock-hosted epithermal Au-Ag deposits (Ada Tepe, Surnak, Kuklitza prospects, Rosino, Stremtsi) (Marchev et al, 2005;Marton et al, 2007;2010), and (4) nonsulfide Zn (Pb, Ag) ores (Thassos) (Boni and Large, 2003) (Fig. 1).…”

Section: Regional Geologic and Metallogenic Frameworkmentioning

confidence: 99%

Marble-Hosted Submicroscopic Gold Mineralization at Asimotrypes Area, Mount Pangeon, Southern Rhodope Core Complex, Greece

Eliopoulos¹,

Kilias²

2011

Economic Geology

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Gold mineralization at Asimotrypes, Mount Pangeon, Greece, occurs within amphibolite facies rocks of the Southern Rhodope Core Complex, one of the largest metamorphic core complexes in the world. Exhumation of the complex resulted from middle Eocene to middle Miocene northeast-southwest-oriented extension in the northern Aegean and was controlled by the Kerdylion detachment zone. Host rocks are mylonitic, impure dolomite marbles of marine provenance (δ 13 C = 1.9-2.9‰), which are intercalated with paramica schists, and amphibolites, and intruded by early Miocene syntectonic granitoids. In the Asimotrypes area, metamorphic rocks and granitoids exhibit flat mylonite-type ductile fabrics with consistent top-to-the-southwest sense of shear, as does the entire Complex. Two mineralogically similar and spatially coincident gold mineralization styles, with a supergene overprint, exist: (1) strata-bound replacement bodies that contain up to 17 ppm gold, concentrated at and controlled by the intersections of several hydrothermally altered top-to-the-southwest marble mylonites, with crosscutting northwest-southeast to east-west-trending high-angle brittle normal faults and fractures, and (2) structurally controlled quartz veins, pods, and lenses with 4 to 13 ppm gold, which occur along the northwest-oriented subvertical brittle structures; the latter crosscut the ductile shear foliation of the host rocks, together with the granitoids, and dip steeply to the southwest. Gold-bearing replacement bodies typically occur as discordant wide halo adjacent to the centrally located brittle structures. Ductile top-to-the-southwest shear zones and crosscutting brittle structures are considered contemporaneous within the regional extensional deformation and exhumation history of the core complex host rocks. The distribution of gold mineralization is related to the geometry of the brittle structures, strongly suggesting that faults acted as major fluid feeder conduits during gold mineralization. Hydrothermal alteration associated with the auriferous bodies and veins, overprinting the metamorphic rocks at Asimotrypes, consists of quartz, muscovite (sericite), chlorite, calcite (dedolomite), and sulfide minerals (locally, as much as 35 vol %). Gangue quartz occurs as (1) peripheral banded quartz with mylonitic texture, (2) dominant gold-bearing jasperoidal quartz, and (3) late, fine drusy quartz. The gold assemblage consists of arsenopyrite (41.7-43 wt % As; electron microprobe analyses) and arsenian pyrite encompassed by jasperoidal quartz; chalcopyrite, galena, tetrahedrite-tennantite, and sphalerite are trace phases. Secondary ion mass spectrometry (SIMS) spot analyses revealed that gold in replacement ore is submicroscopic and occurs in arsenopyrite and arsenian pyrite (As = 0.01-3.8 wt %), ranging from 0.5 to 29 ppm (mean = 11.6 ppm), and 0.14 to 11 ppm (mean = 2.3 ppm), respectively. Supergene overprint includes colloidal goethite + hematite containing native gold grains (size range, 20-40 µm) and lesser covellite, malachite, cerruss...

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