Troodos Ophiolite โ€“ Mining Potential of Cyprus โ€“ Restoration of the Asbestos Mine โ€“ Case Study

The Troodos Ophiolite consists of four stratigraphic units, in ascending order: Plutonics (mantle sequence and cumulates), Intrusives, Volcanics and Chemical sediments.

The mantle sequence consists of the residuals after the partial melting of the upper mantle and the formation of basaltic magma, from which the remaining rocks of the ophiolite are derived. It is mainly composed of harzburgite and dunite with 50-80% of the original minerals altered to serpentine, forming serpentinite rock (with or without concentrations of asbestos) where alteration is almost complete.

The cumulate rocks are the products of crystallisation and concentration of crystals on the floor of the magma chamber, beneath the sea-floor spreading zone. The main cumulate rocks are dunite with or without chromite concentrations, wehrlite, pyroxenite, gabbro and plagiogranite, in small discontinued occurrences.

The intrusive rocks (Sheeted Dyke Complex - Diabase) have a basaltic to doleritic composition and were formed by the solidification of magma in channels which intruded the oceanic crust and fed the submarine extrusion of lavas on to the sea floor.

The volcanics consist of two series of pillow lavas and lava flows, mainly of basaltic composition. The pillow lavas have a characteristic spherical to ellipsoidal pillow shape, 30-70 cm in diameter, which were formed as a result of submarine volcanic activity. Between the intrusive rocks and the pillow lavas a transitional zone known as the Basal Group occurs. Dykes dominate the Basal Group while pillows are less common.

The Perapedhi Formation is composed of umber (chemical sediment), radiolarites and radiolaritic shales. These were the first sediments to be deposited over the ophiolite rocks as a result of hydrothermal activity (hot solutions rich in Fe and Mn) and sedimentation on the sea floor.

MINERAL RESOURCES

Directly associated with the Troodos ophiolite are the massive sulphides, chromite and asbestos mineral deposits. These ore deposits were formed in different stratigraphic units of the ophiolite (lavas, dunite and harzburgite, respectively) and have been exposed because of uplift, resulting in the discovery and exploitation of copper since antiquity.

In addition, Cyprus has significant industrial mineral deposits. These include gypsum (used in cement production), brick clays, umber, ochre and terra verte (natural pigments), marls and chalks (cement production), bentonitic clays (various industrial uses), building stone, celestite, magnesite and aggregates. The production of aggregates relies on the crushing of diabase and carbonate rocks (reefal limestone and calcarenite).

Restoration of the Asbestos Mine โ€“ case study

Cyprus is regarded as one of the most ancient sources of asbestos. The asbestos outcrops attracted the interest of people, due to its characteristic fibrous texture. The usage of asbestos was found quickly, utilising its natural properties, particularly during the Classical and Roman periods, when it was used for the manufacturing of shrouds for the cremation of the dead, shoes, and wicks for lamps.

Modern exploitation begins in 1904, when chrysotile was used extensively in construction. Until 1988, when the mine closed, it is estimated that 130 million tonnes of rock had been excavated, producing one million tonnes of asbestos fibres.

This lengthy operation period affected the natural environment of the area with direct and indirect impact. The main environmental problems include the very large mine pit, the extensive waste dumps with steep, in places unstable slopes, the complete destruction of the pine forest of the area as well as the air pollution (from the presence of the fibres) and the surface water that drains in dams further downstream. All these changes have possible consequences on the safety and health of the people who reside in the nearby villages.

Following the end of the mining activities, the government undertook rehabilitation works. These works began in the autumn of 1995 under the guidance of a multidisciplinary team consisting of a geologist, a geotechnical engineer, a forester, a mining engineer, a town planner, a health inspector, and an environmental scientist.

The work structured around a Restoration Plan, aims mainly for the stability of the waste dumps, reforestation and re-vegetation of restored areas. The stability of the waste dumps involves an extensive reprofiling and landscaping. Reforestation aims for the restoration of the natural landscape and the rehabilitation of the environment at the mine site. The various works, such as soil movement (500,000 m3ย ) and revegetation (12 tonnes of seeds and 80,000 trees), contribute to the stability of the waste dumps, but also to the drastic decrease of the asbestos fibres on the surface and in the air.

On the edge of the Amiantos mine, a Botanical Garden was created by the Forestry Department, which includes plant exhibitions with various sections, a children's activity area and a Visitor's Center. The old school building of the mine is under restoration for an ongoing project for the establishment of the Troodos mountain as a Geopark.

According to the Restoration Plan, the waste dump stability works and the restoration of the area (3.3 km2) will be completed by 2020, while the reforestation and re-vegetation works will continue until completed. Under the guidance of the Asbestos Technical Committee, a master plan for the future uses of the mine area is under preparation and will be completed in early 2014. The Government has undertaken the entire cost of the Restoration Plan.

Eleni Georgiou Morisseau, Director of Geological Survey Department of Cyprus