The exploration of Rosia Montana fold deposit, Rosia Montana, Romania


The Rosia Montana gold deposit is located in western Romania within the
Apuseni Mountain area of Transylvania. The deposit is situated approximately 65
kilometers west of the regional center of Alba-Iulia, within the province of Alba, at
elevations of up to 1100 meters above sea level. The Rosia Montana deposit contains a
current resource of 400.41 million tonnes (Mt) at an average grade of 1.3 grams per
tonne (g/t) gold (Au) and 6.0 g/t silver (Ag) for a total (measured, indicated and
inferred) contained resource of 16.1 million ounces of gold (Moz) and 73.3 Moz of silver.
The resource was calculated using a 0.6 g/t Au cut-off, a 20 × 20 × 10 meter block
size and ordinary kriging. The current proven and probable reserve contains 218 Mt
at a grade of 1.52 g/t Au and 7.5 g/t Ag for total contained metal of 10.6 Moz Au and
52.3 Moz Ag.
The deposit at Rosia Montana occurs within Miocene age dacite intrusions and
maar-diatreme related breccias. Early alteration and mineralization consists of low
sulfidation style epithermal mineralization characterized by quartz-adularia-illite
and pyrite. Precious metals generally are disseminated within quartz-pyrite veinlets
and cemented breccias. Later mineralization is associated with more intermediate sulfidation
style epithermal carbonate-quartz and trace base-metal veins and disseminations.
The dacite bodies and lake sediments are cut by numerous phreato-magmatic
breccias; pre-, syn- and post-mineralization in age. Precipitation of precious metals
occurred as a result of boiling. The maar-diatreme complex intrudes Cretaceous age
interbedded shales and sandstones with subordinate conglomerate units that are of
shallow marine and deltaic origin and overlie Paleozoic sedimentary and metamorphic
rocks. These sedimentary rocks also contain precious metal mineralization.
Argon-argon dating of secondary adularia has aged mineralization at between 12.71
and 13.24 Ma.

SKU: 2005-54 Category:

Additional information


Primary Author

G.V. O'Connor





Deposit Type

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