The Gersdorffite-Bismuthinite-Native Gold Association and the Skarn-Porphyry Mineralization in the Kamariza Mining District, Lavrion, Greece

Abstract

Vein-type Pb-Ni-Bi-Au-Ag mineralization at the Clemence deposit in the Kamariza and “km3” in the Lavrion area, was synchronous with the intrusion of a Miocene granodiorite body and related felsic and mafic dikes and sills within marbles and schists in the footwall of (and within) the Western Cycladic detachment system. In the Serpieri deposit (Kamariza area), a porphyry-style pyrrhotite-arsenopyrite mineralized microgranitic dike is genetically related to a garnet-wollastonite bearing skarn characterized by a similar base metal and Ni (up to 219 ppm) enrichment. The Ni–Bi–Au association in the Clemence deposit consists of initial deposition of pyrite and arsenopyrite followed by an intergrowth of native gold-bismuthinite and oscillatory zoned gersdorffite. The zoning is related to variable As, Ni, and Fe contents, indicating fluctuations of arsenic and sulfur fugacity in the hydrothermal fluid. A late evolution towards higher sulfur fugacity in the mineralization is evident by the deposition of chalcopyrite, tennantite, enargite, and galena rimming gersdorffite. At the “km3” locality, Ni sulfides and sulfarsenides, vaesite, millerite, ullmannite, and polydymite, are enclosed in gersdorffite and/or galena. The gersdorffite is homogenous and contains less Fe (up to 2 wt.%) than that from the Clemence deposit (up to 9 wt.%). Bulk ore analyses of the Clemence ore reveal Au and Ag grades both exceeding 100 g/t, Pb and Zn > 1 wt.%, Ni up to 9700 ppm, Co up to 118 ppm, Sn > 100 ppm, and Bi > 2000 ppm. The “km3” mineralization is enriched in Mo (up to 36 ppm), Ni (>1 wt.%), and Co (up to 1290 ppm). Our data further support a magmatic contribution to the ore-forming fluids, although remobilization and leaching of metals from previous mineralization and/or host rocks, through the late involvement of non-magmatic fluid in the ore system, cannot be excluded.

The Lavrion Mines: A Unique Site of Geological and Mineralogical Heritage

“…According to Bonsall et al [40], the skarn-related metallic content changes with the proximity to the Plaka granodiorite; magnetite and magnetite-hematite are closer to the granodiorite in the Upper marbles, while the assemblages pyrite-pyrrhotite and sphalerite-pyrite-galena occur in the Kamariza schists, farther away from the granodiorite. A minor skarn occurrence is located along the contact of the above-mentioned microgranite body and the Lower marble at the Serpieri mine [69]. It is a garnet-rich skarn, with andradite, wollastonite, apatite, and magnetite being part of the prograde mineral assemblage.…”

“…It is a garnet-rich skarn, with andradite, wollastonite, apatite, and magnetite being part of the prograde mineral assemblage. Calcite, actinolite, epidote, chlorite, quartz, and hematite, as well as pyrite, chalcopyrite, and pyrrhotite formed during the retrograde stage [69].…”

“…Based on their mineralogical composition and preliminary geochemical data, they are classified as microdiorites and microgranites, respectively [69]. According to Marinos and Petrascheck [9], the largest dikes in the Kamariza area outcrop north of the "Serpieri 1" shaft, between the "Serpieri 1", the "Hilarion 1" shafts, and the south of the Hilarion orebody (Figure 2c).…”

“…The granodiorite and the dikes within the Kamariza and the Lavrion units are metaluminous to peraluminous and are classified as both I-and S-type granites [40,65,67,69] (Figure 4). Radiometric dating performed on several granitoid rocks from the footwall and the hanging wall of the detachment fault in Lavrion area provide ages for the igneous activity at Lavrion between 9.4 to 7.3 Ma [57,65,67].…”

“…Porphyry-type mineralization also occurs in the Serpieri deposit at Kamariza (operated during the modern mining era at Lavrion), where microgranite dikes are crosscut by stockworks hosting pyrrhotite, arsenopyrite, pyrite, and galena. The veinlets are related to carbonate-sericite alteration of the host rock, which overprints secondary biotite and K-feldspar, being part of an earlier potassic alteration event [69].…”