Athanassios Katerinopoulos

A mineralogical petrographic and geochemical study of samples from wells in the geothermal field of Milos Island (Greece)

Abstract This paper presents a study of hydrothermal alteration on Milos island, Greece. Examination of cores and cuttings from the two drill sites, obtained from a depth of about 1100 m in Milos geothermal field, showed that the hydrothermal minerals occurring in the rock include: K-feldspar, albite, chlorite, talc, diopside, epidote, muscovite, tremolite, kaolinite, montmorillonite, alunite, anhydrite, gypsum, calcite, and opaque minerals. The chemical composition of the minerals (104 analyses) was determined with Electron Probe Microanalysis. The composition of the hydrothermal fluid was determined and correlated with the mineralogy. Isotopic ratios of C and O for one calcite sample taken from 341 m depth were determined and used for geochemical calculations. A number of reactions feasible at the P—T conditions of the geothermal field are given to establish the chemical evolution of the hydrothermal fluid. The distribution of the hydrothermal minerals indicates the dilution of the K-, Na-, Cl-rich hydrothermal fluid of the deep reservoir by a Ca-, Mg-rich cold water at a shallower level.

Pb2(AsO2OH)Cl2, a new phase from the Lavrion ancient slags, Greece: occurrence and characterization

Abstract Transparent prismatic crystals of Pb2(AsO2OH)Cl2 were collected in black metallurgical slag on the coast in the Punta Zeza area, 3 km south of the town of Lavrion, Greece. Analyses by energy-dispersive X-ray spectrometry (EDS) provided the following chemical composition: PbO 73.04, As2O3 15.97, Cl 11.42, O=Cl -2.58, total 97.85 wt.%. The empirical formula calculated on the basis of As = 1 is HxPb2.03(AsO3)1.00Cl1.995 (x = 0.96). The infrared spectrum of Pb2(AsO2OH)Cl2 has characteristic AsO33- bands at 707 and 594 cm-1, O-H stretching vibrations at 3310 and 2900 cm-1 and a band at 1107 cm-1 which is assigned to As-O-H bending vibrations. The structure, which is monoclinic P21/m, a = 6.4235(8), b = 5.5399(7), c = 9.321(1) Å, β = 90.767(2)°, V = 331.67(7) Å3, R1 = 0.035, is identical to that of synthetic Pb2(AsO2OH)Cl2 and contains two symmetrically unique Pb sites and one As site. The crystal structure is based on [Pb2AsO2OH]2+ double chains interconnected via weak Pb-Cl bonds to produce a three-dimensional framework which is closely related to that of Pb oxysalt minerals containing [O2Pb3]2+ chains of oxocentred [OPb4]6+ tetrahedra including mendipite, damaraite, rickturnerite and plumboselite.

Hilarionite, Fe23+(SO4)(AsO4)(OH) · 6H2O, a new supergene mineral from Lavrion, Greece

A new mineral, hilarionite, ideally Fe23+ (SO4)(AsO4)(OH) · 6H2O, has been found in the Hilarion Mine, Agios Konstantinos, Kamariza, Lavrion district, Attiki Prefecture, Greece. It was formed in the oxidation zone of a sulfide-rich orebody in association with goethite, gypsum, bukovskyite, jarosite, melanterite, chalcanthite, allophane, and azurite. Hilarionite occurs as light green (typically with an olive or grayish tint) to light yellowish green spherulites (up to 1 mm in size) and bunches of prismatic to acicular “individuals” up to 0.5 mm long that are in fact near-parallel or divergent aggregates of very thin, curved fibers up to 0.3 mm long and usually lesser than 2 μm thick. The luster is silky to vitreous. The Mohs’ hardness is ca. 2. Hilarionite is ductile, its “individuals” are flexible and inelastic; fracture is uneven or splintery. D(meas) = 2.40(5), D(calc) = 2.486 g/cm3. IR spectrum shows the presence of arsenate and sulfate groups and H2O molecules in significant amounts. The Mössbauer spectrum indicates the presence of Fe3+ at two six-fold coordinated sites and the absence of Fe2+. Hilarionite is optically biaxial (+), α = 1.575(2), γ = 1.64(2), 2V is large. The chemical composition (electron microprobe, average of 7 point analyses; H2O determined by modified Penfield method) is as follows, wt %: 0.03 MnO, 0.18 CuO, 0.17 ZnO, 33.83 Fe2O3, 0.22 P2O5, 18.92 As2O5, 22.19 SO3, 26.3 H2O, total is 101.82%. The empirical formula calculated on the basis of 15 O is: (Fe1.903+Cu0.01Zn0.01)Σ1.92[(SO4)1.24(AsO4)0.74(PO4)0.01]Σ1.99(OH)1.01 · 6.03H2O. The X-ray powder diffraction data show close structural relationship of hilarionite and kaňkite, Fe23+(AsO4)2 · 7H2O. Hilarionite is monoclinic, space group C2/m, Cm or C2, a = 18.53(4), b = 17.43(3), c = 7.56(1) Å, β = 94.06(15)°, V = 2436(3) Å3, Z = 8. The strongest reflections in the X-ray powder diffraction pattern (d, Å-I[hkl]) are: 12.66–100[110],

The Lavrion Mines

7.60 - 6[00\bar 1]

The crystal structure of the compound Pb6Cu+(AsO3)2Cl7 discovered in the ancient slags of Lavrion, Greece

, 5.00–10[22l],

Agardite-(Nd) NdCu6(AsO4)3(OH)6·3H2O from the Hilarion Mine, Lavrion, Greece: mineral description and chemical relations with other members of the agardite-zalesiite solid-solution system

4.70 - 10[31\bar 1]