Geology and Origin of Supergene Ore at the Lavrion Pb‐Ag‐Zn Deposit, Attica, Greece

Abstract

The Lavrion carbonate-hosted Pb-Ag-Zn deposit in southeast Attica, Greece, consisted of signifi cant nonsulfi de ore bodies. The polymetallic sulfi de mineralization was subjected to supergene oxidation, giving rise to gossan. The principal non-sulfi de minerals of past economic importance were smithsonite, goethite and hematite. The supergene mineral assemblages occupy secondary open spaces and occur as replacement pods within marble. Calamine and iron ore mainly fi lled open fractures. X-ray diffraction and scanning electron microscopy of samples of oxidized ore indicate complex gossan mineralogy depending on the hypogene mineralogy, the degree of oxidation and leaching of elements, and the local hydrologic conditions. Bulk chemical analysis of the samples indicated high ore-grade variability of the supergene mineralization. On multivariate cluster analysis of geochemical data the elements were classifi ed into groups providing evidence for their differential mobilization during dissolution, transport and re-precipitation. The mode of occurrence, textures, mineralogy and geochemistry of the non-sulfi de mineralization confi rm that it is undoubtedly of supergene origin: the product of infl ux into open fractures in the country rock of highly acidic, metal-rich water resulting from the oxidation of pyrite-rich sulfi de protore. Dissolution of carbonates led to opening of the fractures. Mineral deposition in the supergene ore took place under near-neutral to mildly acidic conditions. The supergene dissolution and re-precipitation of Fe and Zn in the host marble increased metal grades and separated iron and zinc from lead, thereby producing economically attractive deposits; it further contributed to minimization of pollution impact on both soil and ground water.

Natural contamination by As and heavy metals in soil, their bio-accumulation and potential sources: the case of a travertine limestone quarry, Greece

“…Although any continuity between the famous ancient mines of Grammatiko and Lavrio is not obvious, underground mining at Grammatiko revealed geological and structural relationships between the host rocks and the "ferromanganese formation" [16] or gossan [17] that resemble those located at the Lavrio mine.…”

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-zálesíite solid-solution system

“…Ore mineralogy demonstrates that most of the Kamariza ore has formed by moderately to low-saline hydrothermal fluids at intermediate to high sulphidation conditions. Subsequent oxidation of the primary sulphides resulted in a development of an extensive supergene minerals zone from which hundreds of mineral species have been described (Katerinopoulos and Zissimopoulou 1994;Baumgartl and Burow 2002;Skarpelis and Argyraki 2009). Formation of the different supergene mineral species and assemblages was controlled mainly by near-neutral to mildly acidic conditions, variable P CO 2 , metal and sulphate ion activities and Eh (Skarpelis and Argyraki 2009).…”

Metallic mineral resources of Greece

“…The Olympias deposit is generally strata bound or fracture controlled and in places stratiform. Its main mineral constituents are pyrite, galena, sphalerite and arsenopyrite with quartz, calcite and rhodochrosite as gangue minerals [10][11][12]. In Skra Kilkis the probable reserves of base and precious metals include: 4.7 mt of sulphides with 7.7% Zn+Pb, containing 172,000 t Zn, 113,000 t Pb and 80 t Ag.…”

“…Silver has been also detected in Chalkidiki (Olympias, Stratoni), Evros (Perama Hill, Kirki), Thassos, Skra Kilkis, etc. [7,10,11,13,19]. In Skra Kilkis the probable reserves of base and precious metals include: 4.7 mt of sulphides with 7.7% Zn+Pb, containing 172,000 t Zn, 113,000 t Pb and 80 t Ag.…”