Regional similarities in lead isotopes and trace elements in galena of the Cyclades Mineral District, Greece with implications for the underlying basement

Wind, Sandra; Schneider, David; Hannington, Mark D.; McFarlane, Christopher R.M.

doi:10.1016/j.lithos.2020.105559

Cited by 17 publications

(10 citation statements)

References 94 publications

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“…The origin of As and Hg in the Milos mineralization can only be speculated: Wind et al [131] proposed that enrichments in As, Tl, and Hg, which were observed in deposits that occur in the hanging wall of major detachment faults (e.g., Milos), may be related to leaching from associated supra-detachment sediments of the Miocene conglomeratic sequence. However, according to Katsouri et al [128], the volcanic arc crust is probably the source of As for the Paleochori Bay hydrothermal system, and Price et al [46] suggested that the extremely high As contents of the Paleochori Bay fluids are due to leaching of the As-rich metamorphic basement.…”

Section: Comparison With Other On-shore Milos Mineralization and Sources Of As And Hg In The Fluidsmentioning

confidence: 99%

Arsenian Pyrite and Cinnabar from Active Submarine Nearshore Vents, Paleochori Bay, Milos Island, Greece

et al. 2020

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Active, shallow-water (2–10 m below sea level) and low temperature (up to 115 °C) hydrothermal venting at Paleochori Bay, nearshore Milos Island, Greece, discharges CO2 and H2S rich vapors (e.g., low-Cl fluid) and high-salinity liquids, which leads to a diverse assemblage of sulfide and alteration phases in an area of approximately 1 km2. Volcaniclastic detritus recovered from the seafloor is cemented by hydrothermal pyrite and marcasite, while semi-massive to massive pyrite-marcasite constitute mounds and chimney-like edifices. Paragenetic relationships indicate deposition of two distinct mineralogical assemblages related to the venting of high-Cl and low-Cl fluids, respectively: (1) colloform As- and Hg-bearing pyrite (Py I), associated with marcasite, calcite, and apatite, as well as (2) porous and/or massive As-rich pyrite (Py II), associated with barite, alunite/jarosite, and late-stage hydrous ferric oxides. Mercury, in the form of cinnabar, occurs within the As-rich pyrite (Py I) layers, usually forming distinct cinnabar-enriched micro-layers. Arsenic in colloform pyrite I shows a negative correlation with S indicating that As1− dominates in the pyrite structure suggesting formation from a relatively reducing As-rich fluid at conditions similar to low-sulfidation epithermal systems. On the contrary, As3+ dominates in the structure of porous to massive pyrite II suggesting deposition from a sulfate-dominated fluid with lower pH and higher fO2. Bulk sulfide data of pyrite-bearing hydrothermal precipitates also show elevated As (up to 2587 ppm) together with various epithermal-type elements, such as Sb (up to 274 ppm), Tl (up to 513 ppm), and Hg (up to 34 ppm) suggesting an epithermal nature for the hydrothermal activity at Paleochori Bay. Textural relationships indicate a contemporaneous deposition of As and Hg, which is suggested to be the result of venting from both high-salinity, liquid-dominated, as well as CO2- and H2S-rich vapor-dominated fluids that formed during fluid boiling. The CO2- and H2S-rich vapor that physically separated during fluid boiling from the high-salinity liquid led to calcite formation upon condensation in seawater together with the precipitation of As- and Hg-bearing pyrite I. This also led to the formation of sulfuric acid, thereby causing leaching and dissolution of primary iron-rich minerals in the volcaniclastic sediments, finally resulting in pyrite II precipitation in association with alunite/jarosite. The Paleochori vents contain the first documented occurrence of cinnabar on the seafloor in the Mediterranean area and provide an important link between offshore hydrothermal activity and the onshore mercury and arsenic mineralizing system on Milos Island. The results of this study therefore demonstrate that metal and metalloid precipitation in shallow-water continental arc environments is controlled by epithermal processes known from their subaerial analogues.

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Section: Comparison With Other On-shore Milos Mineralization and Sources Of As And Hg In The Fluidsmentioning

confidence: 99%

Arsenian Pyrite and Cinnabar from Active Submarine Nearshore Vents, Paleochori Bay, Milos Island, Greece

et al. 2020

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“…As a result of slab roll-back, orogenic collapse and the opening of the Aegean back-arc basin allowed for the post-orogenic exhumation of the crust as metamorphic core complexes, such as in the Cyclades, associated with voluminous magmatism [46]. Three major units, the Cycladic basement, the Cycladic blueschist unit, and the Upper tectonic unit, can be distinguished, from bottom to top, in the Attic-Cycladic belt (e.g., [46,47,52], Figure 1b), with two of them, mainly the Cycladic blueschist-and the Upper tectonic units, being exposed in the Lavrion area. In addition, the so-called Basal unit is exposed on Amorgos, Samos, and Evia islands (Figure 1b).…”

Section: Regional Geologymentioning

confidence: 99%

“…The aim of this article is to expand on previous work and summarize the current state of knowl-edge on the geology, the mineralization, and the supergene mineralogy of the Lavrion deposit and to highlight its unique geological, mineralogical, archaeological, mining, and educational features. [46], Wind et al [47], Grasemann et al [48], and modified after Ottens and Voudouris [5]. The location of the Sigri at Lesvos, Psiloritis, Chelmos-Vouraikos, Vikos-Aoos, and Sitia UNESCO Global Geoparks are shown, while the Lavrion area is marked with a red square in Figure 1b and described in detail in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 1. Geological map of (a) Greece and (b) the Attic-Cycladic belt from Jolivet et al[46], Wind et al[47], Grasemann et al[48], and modified after Ottens and Voudouris[5]. The location of the Sigri at Lesvos, Psiloritis, Chelmos-Vouraikos, Vikos-Aoos, and Sitia UNESCO Global Geoparks are shown, while the Lavrion area is marked with a red square in Figure1band described in detail in Figure2.…”

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

et al. 2021

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The Lavrion area corresponds to the western part of the Attic-Cycladic metamorphic belt, in the back-arc region of the active Hellenic subduction zone. Between the Eocene and the Miocene, metamorphic rocks (mainly marbles and schists) underwent several stages of metamorphism and deformation due to collision and collapse of the Cycladic belt. Exhumation during the Miocene was accommodated by the movement of a large-scale detachment fault system, which also enhanced emplacement of magmatic rocks, leading to the formation of the famous Lavrion silver deposits. The area around the mines shows the stacking of nappes, with ore deposition mainly localized within the marbles, at marble-schist contacts, below, within, or above the detachment. The Lavrion deposit comprises five genetically-related but different styles of mineralization, a feature never observed in another ore deposit elsewhere, containing the highest number of different elements of any known mining district. The local geology, tectonic, and magmatic activity were fundamental factors in determining how and when the mineralization formed. Other key factors, such as the rise and the fall of sea level, which resulted from climate change over the last million years, were also of major importance for the subsequent surface oxidation at Lavrion that created an unmatched diversity of secondary minerals. As a result, the Lavrion deposit contains 638 minerals of which Lavrion is type-locality for 23 of them, which is nearly 12% of all known species. Apart from being famous for its silver exploitation, this mining district contains more minerals than any other district on Earth. The unique geological, mineralogical, and educational (mining, archaeological, and environmental) features suggest that it is highly suitable to be developed as a future UNESCO Global Geopark.

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“…Other authors consider this an entirely greenschist facies metamorphic event (Cao et al, 2018). The CBU has been subdivided into the eclogite facies Upper (UCBN) and blueschist facies Lower Cycladic Blueschist nappes (LCBN), separated by the synorogenic Trans‐Cycladic Thrust (Figure 1b; Grasemann et al, 2018; Wind et al, 2020).…”

Section: Geological Settingmentioning

confidence: 99%

Lateral Termination of a Cycladic‐Style Detachment System (Hymittos, Greece)

et al. 2020

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The bedrock of Hymittos, Attic peninsula, Greece, exposes a pair of low-angle crustal-scale ductile-then-brittle detachment faults. The uppermost detachment fault separates sub-greenschist facies phyllite and marble of a Pelagonian Zone hanging wall, from greenschist facies metasedimentary schist, calc-schist, and marble correlated to the Cycladic Blueschist Unit. A second, structurally lower detachment fault subdivides the metamorphic rocks of the Cycladic blueschist unit footwall into middle and lower units. There is a marked step in metamorphic grade between the sub-greenschist facies uppermost package, and the middle-to-upper greenschist facies middle and lower packages. A suite of new white mica 40 Ar/ 39 Ar and zircon (U-Th)/He dates indicates accommodation of deformation along these faults occurred from the late Oligocene to the late Miocene with both faults active during the middle Miocene. The structures have clear top-S/SSW kinematics determined from flanking folds, sigmoids, shear bands, stair-stepping of strain shadows on porphyroclasts, and SCC' fabrics. The ductile-to-brittle deformation of the structures, morphology of the massif, and the increase in metamorphic grade suggest these low-angle structures are part of a major, crustal-scale extensional complex, located at the northwest end of the West Cycladic Detachment System, that accommodated Miocene bivergent exhumation of Attic-Cycladic metamorphic core complexes in the central Aegean. Taken together, the above data suggest that multiple coeval detachment branches may form in areas with high strain gradients to accommodate the mechanically necessary termination of Cycladic-style detachment systems.

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Regional similarities in lead isotopes and trace elements in galena of the Cyclades Mineral District, Greece with implications for the underlying basement

Cited by 17 publications

References 94 publications

Arsenian Pyrite and Cinnabar from Active Submarine Nearshore Vents, Paleochori Bay, Milos Island, Greece

Arsenian Pyrite and Cinnabar from Active Submarine Nearshore Vents, Paleochori Bay, Milos Island, Greece

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

Lateral Termination of a Cycladic‐Style Detachment System (Hymittos, Greece)

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