POLYPHASE TECTONICS AS TOOL FOR EXPLORATION OF CHROMITE ORES HOSTED BY ULTRAMAFIC ROCKS OF BULQIZA ULTRAMAFIC MASSIF, ALBANIA

The Albanian ophiolites of the Mirdita Zone represent remnants of Mesozoic oceanic lithosphere within the Dinaride-Albanian- Hellenide segment of the Alpine orogenic system.

Most recent studies distinguish two different rock associations forming the Western (WOB) and Eastern Ophiolite Belt (EOB).

Bulqiza Ultramafic massif that covers an area of c. 350 km2 hosting the principal mined ores (Bulqiza-Batra, Thekna etc. with more than 22.6 Mt @ 40% Cr₂ O3) belongs to the Eastern Ophiolite Belt (EOB).

The ores are considered as podiform chromite ores characterized by relatively small sizes, irregular shapes and limited lateral continuity.

In the structural point of view Bulqiza-Batra chromite deposit is widely accepted to be hosted by an overturned antiform, with easterly vergence, 4.5 km long, 1.2 to 1.5 km wide and 0.5 to 1.7 km down dip with an axial orientation strike 330⁰. The antiform was thought to be restricted to the east by a southwesterly dipping normal fault over an area 3.8kmlong and 0.25 km wide (Bulqiza-Batra geologists). More recently are described steep southwesterly dipping normal faults at west limb and east directed thrusts at the eastern limb of anticlinorium (e.g Happel et al., 1998).

Exploration works performed by Empire Mining Corporation at Bulqiza-Batra-Thekna ore field and NW at Qafe Burreli carried out during 2008-2011years indicated for high developed west directed polyphase thrusting tectonics that led to new interpretation of the structural setting of the chromite mineralization in the Bulqiza-Batra-Thekna system- the secondary fold within west dipping homocline displaced by thrust faults, with eastern and western extension of chromite ores.