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Borba 2

PROJECTS

Overview

The Borba 2 exploration permit consists of four projects and is located 160 km east by road from Lisbon and is approximately 70 Km east of Évora, the district capital. The recognized potential of this sector to host precious-metal and base metal mineralization is enhanced by the presence of abundant Cu and/or Au mineral occurrences in shear zones and in epithermal systems associated with intra-Ordovician volcanism.

The Borba 2 permit covers an area of 328.5 sq. km and represents an elongated polygon with the longest side near 40 km long, and the widest part of approximately 11km. The permit is granted by the State for a total period of five years, including a three-year initial contract, followed by another two-year extension period.

History

The Rio Tinto Group explored the area for epithermal gold deposits during the early 1980’s. They were followed by Carnon Holdings Ltd, in the early 1990’s, by Auvista Minerals during the period 1996-1998, by Rio Narcea Gold Mines in a JV with Kernow Resources (2005-2007) and more recently by Colt Resources.

MIGUEL VACAS

Highlights

  • Shallow secondary copper minerals in brecciated zones and impregnations in black/grey shales in the oxide zone, including Malachite, Libethenite, Crisocola, Atacamite and Covelite.
  • Primary cupriferous, almost exclusively associated with brecciated zones with Chalcopyrite + quartz + carbonate from 80 metres depth.
  • Mined via open pit in the 1980’s—approx. 900 tons of copper metal in concentrate produced at an average grade of 2.1% Cu.
  • The halting of mining operations at Miguel Vacas in 1990 was due to the financial difficulties of its holding company Minargol, which went bankrupt as a result of their tin mining operation in Argozelo (Northern Portugal).
  • The deposit remains open along strike and down dip.   Mineralization is traced over 1.7 km.

BUGALHO COPPER (Au) MINE

History

The mine was registered in 1866 and has operated intermittently until around 1900. There are records for a total of nine mine levels, down to a total depth of 200m.

Geology 

Silurian dark-grey shales with intercalations of black cherts, quartzites and graphitic phyllites adjacent to a major NE-SW deep seated fault zone (Messejana fault).



Structure 

Quartz-cemented breccias emplaced on east branch of the fault zone. Mineralization associated with a 1km long section of the fault zone. Includes three main veins that have been mined in the past: 

  • Vein 1 (main vein) – N50ºE/80 o NW, up to 1.2 m thick, mined over 800m along strike.
  • Vein 2 – NS/50 o E, average 1.3m thickness.
  • Vein 3 – NS/90 o; no records on thickness. The mineralization is from a wide NE-SW trending anastomosing shear zone that can be mapped on 5 km long strike.

Past Exploration Results 

Dump samples of silicified and sheared acid tuffs from the Bugalho mine area assayed up to 10.97 g/t Au, 5.36% Cu and 20 g/t Ag.

  • Six out of 18 samples assayed >/= 2.7 g/t Au. Peak Cu assays returned 20.19%.

Mineralization 

Primary Copper mineralization: chalcopyrite and pyrite and accessory arsenopyrite within quartz carbonate breccia matrix. Supergene Copper mineralization includes malaquite, hematite and skorodite. Gold seems to be mainly associated with arsenopyrite.

Almagreira Gold Target

Previous Exploration

Two holes completed by Rio-Tinto. Hole PAM-1 includes an interval of 5.45 m grading 1.53 g/t Au, including 2.47m grading 2.44 g/t Au. The highest individual value obtained came from a gossanous quartz-dolomite altered marble grading 5.77 g/t over an intercept of 0.75m. Banded carbonatization and low-temperature silica alteration occur thoroughly in the hole. Zones of poor recovery are interpreted to represent karst fill features.

Hole PAM-2, located in the same zone includes an intercept of 17m grading 0.5 g/t Au, including an interval of 2 m grading 3.7 g/t Au. The mineralized zone coincides with sections of intense silica-carbonate alteration with several massive gossan zones and localized fresh sulphide dissemination (chalcopyrite and pyrite).

Mineralization

Gold epithermal mineralization occurs in altered volcanics and carbonates and is mainly controlled by an E-W structure, that extends at least 400 metres along strike and is open at depth. The mineralized zone occupies the core of a second order anticline with acid volcanics flanked by Silurian shales, phyllites and graphitic phyllites.

Mostardeira Cu-Au Mine

Previous Exploration 

Channel sampling by Rio Narcea Gold Mines in 2016 highlights:

  • 18.6m grading 0.8 g/t Au, 0.3% Cu and 20 g/t Ag – Including:
    • 4.9 m grading 2.1 g/t Au, 0.76 % Cu and 64 g/t Ag

Mineralization 

Wide (5-10 meter thick) anastomosing WSW-ESE trending vein system at least 700 m along strike. This shear zone has been historically mined for Cu.