Integrated magnetotelluric (MT) and transient electromagnetic (TEM) studies of structural control on massive sulphide mineralisation in part of Northeastern Troodos Ophiolite Complex, Cyprus

摘要

The massive Fe- and Cu-sulphide mineralisation is the most valuable economic resource in the Troodos and has been explored and exploited mainly through exploratory drilling around ancient slags, gossans and old workings. The exhaustion of these superficial guides has meant a shift to locating orebodies at depth. Direct detection of orebodies by traditional geophysical methods has been difficult. Structures parallel and perpendicular to the spreading axes in the region are thought to control the localisation of the sulphide deposits. Their identification should aid indirect detection of mineralisations.;Prior to speculation on possible geological meanings of data from an area not known for sulphide mineralisation, 33 MT and 48 TEM soundings were performed at Klirou, a known area of buried massive sulphide mineralisation. The joint MT/TEM methods identified the low resistivity lithological unit that hosts the mineralisation and the bounding faults, demonstrating their usefulness in mapping the lithological units and structures that host and control these mineralisations. Coincident IP and geological or geochemical anomalies could then be used to locate the orebodies.;In Ayia Marina area, 37 MT and 68 TEM soundings were undertaken. Some ENE structures corresponding to the western flank of Mitsero graben, where the extrusion of the Troodos sulphide-bearing lavas is envisaged to have taken place, have been confirmed by ground MT/TEM surveys. The occurrence of olivine-bearing rocks north of Ayia Marina and the existence of an andesite plus 2 km north-northwest of Ayia Marina suggest that the interpreted low resistivity zone in the area may correspond to a prospective zone for massive sulphide occurrence.