Su Sinibidraxiu Mine, Monte Tamara mining area, Nuxis, South Sardinia Province, Sardinia, Italyi

Regional Level Types
Su Sinibidraxiu Mine	Mine
Monte Tamara mining area	Mining Area
Nuxis	Municipality
South Sardinia Province	Province
Sardinia	Autonomous Region
Italy	- not defined -

Su Sinibidraxiu mine, located on the NW edge of the Monte Tamara ridge, ~2 km north of the San Pietro mine, ws active since the late 19th Ccntury until the second half of the 20th Century and exploited Zn–Pb–Cu–As ores.

The mine can be accessed underground by an E–W stope of 200 m in length, excavated primarily in the Cambrian carbonate rocks of the Gonnesa Formation. The thermal recrystallisation increases eastwards, and limestone–dolostone grade into marbles with sporadic disseminations of Zn–Pb sulfides. In the main orebody is a 1 m thick and 4 m large, vertical and flattened chimney hosted in dolomitic marbles. This is located at the intersection between two NNE–SSW and ESE–WSW striking fractures, and extends for ~60 m upwards to the surface, where it presents as a small gossan deposit. In the underground exposure, five zones (1-5) can be recognised. Zone 1 is a 30 cm thick arsenopyrite + scheelite + Ca–Mg-carbonates association. Arsenopyrite is the most abundant mineral occurring as lustrous grey, idiomorphic and centimetre-sized crystals, intergrown with carbonates and milky-white idiomorphic scheelite crystals. Scheelite ranges from few mm to 2 cm in size and can be distinguished from carbonates under short-wave ultraviolet light. In the 20 cm thickzone 2, arsenopyrite, carbonates and quartz are the most abundant minerals, with subordinate scheelite and sphalerite. Arsenopyrite, less abundant than in zone 1, is enclosed in a pale greenish carbonates and quartz matrix forming large radiate/fibrous aggregates. Scheelite here occurs as millimetre- to centimetre-sized grains, scattered irregularly inside the carbonates–quartz aggregates. Arsenopyrite decreases gradually towards zone 3 in favour of a sphalerite ± scheelite association in the carbonates–quartz matrix, here assuming a brownish-green colour and forming larger radiate aggregates (2 cm in diameter). Centimetre-sized grains of dark sphalerite are observed at the core of the aggregates, resembling cockade-type textures. Scheelite disseminations within these cockades become more sporadic. Zone 4 is an arsenopyrite + calcite veinlet marking the contact between the ore and marbles. Lastly, irregular veinlets and pockets of massive sulfides of zone 5, consisting of sphalerite, arsenopyrite, chalcopyrite, galena and pyrite associated with calcite–dolomite and baryte, crosscut the other associations.

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References