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ADVANCED TECTONIC AND GEOCHEMICAL METHODS FOR CHROME EXPLORATION IN OPHIOLITES, GREECE

Objective

The objective of the project is to generate predictive models for chromite exploration in Greek ophiolites.
A follow up study was made on initial indications that geochemistry can be successfully applied as an exploration methodology for chrome exploration on scales ranging from that of discrimination between ophiolitic complexes to that of drill site location. Research has suggested several new geochemical tools; these have been developed and applied within on going exploration programmes.

Structural and petrologic discriminants developed in the previous programming periods were applied to vast unexplored ophiolitic terranes in the Pindos and Othris ophiolites; over a 1000 square km have been mapped and 'rated' as to orebearing potential.

The research showed a concurrence of geochemical and tectonic investigations in locating areas of high potential. Both methods spot east Mavrovouni in Pindos as a likely ore host; both are capable of recognizing a metalliferous zone in Vourinos and targeting an exploration bore hole. Compared to the cost of hard rock drilling, both are cost effective. The cost of a typical borehole (200 m at 15000 drachmas/m) is 3000000 drachmas. The cost of a 20 day field study (tectonic analysis and geochemical sampling) plus follow up geochemistry is half the cost. Thus, the price of applying field based methodology to a potential chrome ore district is more than offset by the elimination of a single ill targeted borehole.
A general model will be developed on ophiolitic ores by a systematic study of structural and petrologic controls on the presence of chrome ores in the Pindos, Othris, Vourinos, Chalkidiki and Euvian ophiolitic complexes. This model will provide the basis of a new chrome ore exploration technology applicable to any ophiolitic system.

Structural studies will comprise the following tasks.
Firstly, delineation of peridotite tectonic domains capable of preserving chrome ore bodies in the Pindos, Othris and Chalkidiki ophiolites. This includes: field work; mapping; sampling for mineralogical and geochemical analysis; interpretation of structural data; and production of geological and structural maps for each selected area. This first task is aimed at reducing the surface of the zones to be explored.
Secondly, microfabric analysis of potential host terrane at Vourinos, (laboratory work on oriented samples, approximately 100 samples from surface exposures); 3-dimensional reconstruction of the host terrane.
Thirdly, petrofabric study of ridgecrest environment suitable for chromite areas (e.g. mantle diapirs, ridge axis) at Vourinos.
The second and third tasks are aimed at determining the possible geometry of the orebodies and to orientate the positioning of boreholes in favourable areas for chromium orebodies.

Geochemical studies will be carried out in the above mentioned selected area and will consist of the following. .SP 0 Firstly,petrologic feasibility studies (using major and trace element analyses and mineralogical studies) on ophiolite chrome potential by recognition of boninitic series from studies of crustal sequence ophiolitic rocks (cumulates). Target areas are Chalkidiki, Othris, and Pindos ophiolites.
Secondly, development of geochemical criteria for recognizing boninite related peridotite within the mantle series at Pindos, Chalkidiki,and Vourinos. A data base will be set up and will correlate analyses derived from all Greek ophiolites under study with emphasis on Vourinos.
Thirdly, analyses (geochemical, microprobe, mineralogical) for use in determining the fertility of a specific volume of dunite at Vourinos. This will be performed on drill core samples. Approximately 200 samples will be analyzed. Dunites known for their fertility will be compared with sterile dunites. Indicators of fertility will be determined.
Fourthly, statistical and systematic study of spinel geochemistry anomalies (microprobe analyses) around chromium ore bodies (2 sites at Vourinos, about 10 profiles per site with a sample collected each 20 m, each profile will consist of 5 samples).

Aeromagnetic and satellite imagery reconnaissance studies using existing data will be completed for the Chalkidiki and Euvian ophiolites. These studies will help the structural studies at small scale.

Funding Scheme

CSC - Cost-sharing contracts
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Coordinator

INSTITUTE OF GEOLOGY AND MINERAL EXPLORATION
Address
70,Messoghion Street 70
115 26 Athens
Greece

Participants (3)

Metallurgical Industrial Research andTechnological Development Center SA
Greece
Address
Industrial Area
38500 Volos
National and Kapodistrian University of Athens
Greece
Address
Panepistimioupolis
15784 Athens
UNIVERSITY OF DURHAM
United Kingdom
Address
South Road, Science Laboratory
DH1 3LE Durham