In July 2017, the Atalaya Mining Plc. announced that it had executed the option to acquire 10% of the share capital of Cobre San Rafael, a wholly owned subsidiary of Explotaciones Gallegas S.L. This acquisition was part of an earn-in agreement, structured in four phases, allowing the Group to progressively increase its stake in CSR up to 80%.
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Summary:
The Touro deposit is hosted in a continuous, highly deformed and metamorphosed horizon of metabasite and paragneiss of the Arinteiro Unit (Ordenes Complex). This horizon outcrops along the flanks and hinge zone of a broad north plunging antiformal structure for at least 8km along strike and up to 2km across strike. It extends beyond the project area and is open to depth.
The Arinteiro Unit is composed mainly by metabasites with minor lenses of ultramafic rocks and paragneisses (Gomez Barreiro, 2007). The mineralogy, grain size, and homogeneity of the metabasites are variable, most of the rock types are hornblende-plagioclase rocks with or without garnet (almandine), clinopyroxene (salite), and quartz. The rocks have undergone varying degrees of cataclasis commonly associated with retrogressive greenschist facies assemblages. The metabasites are strongly deformed showing tectonic banding, intrafoliar folds and oriented nematoblastic texture. Very locally, relict igneous textures have been described supporting the theory of a gabbroic protolith (Castineiras et al., 2002; Gomez Barreiro, 2007).
The metasediments of the O Pino Unit lie above and below the metabasites that have been interpreted as representing a flysh sequence (Gomez Barreiro, 2007). This unit is composed mainly of paragneisses with predominant greywacke composition. Minor pelitic metasediments, biotitic shists (sometimes rich in graphite), and amphibolite gneisses are also described in this unit.
According to Atalaya Mining, there is a main horizon of paragneiss in the project area with an estimated thickness of around 400m that hosts metabasites that are represented mainly by amphibolites interbedded within the metasediments. The metabasites appear to represent a single level event of volcanic or subvolcanic origin. The thickness of the amphibolite horizon based on the drilling data of Atalaya Mining, varies from a few meters to up to 90 m.
Rock weathering is limited to a few meters below the surface.
Mineralization.
The ore zone consists of one or two mineralized horizons of disseminated mineralization closely associated with coarse grained garnet amphibolite that is poor in calcium. Garnet content is up the 90% of the volume of the rock (garnetite). The garnet amphibolite grades into non-mineralized normal amphibolite with decreasing garnet content.
The whole amphibolite horizon is surrounded by metasediments, mainly paragneisses that are normally barren or weakly mineralized although mineralized paragneiss has been described in Arca and Monte das Minas in the lower paragneiss.
In general, the ore bodies are tabular, shallow dipping, very consistent and continuous in terms of geometry but with variable thickness. The mineralization hosting amphibolitic metabasites are composed by gedrite, almandine and minor staurolite, and albite-oligoclase.
The mineralization is represented in order of abundance by pyrrhotite, chalcopyrite and minor pyrite and sphalerite. Williams (1983) described evidences of pre- and syn-deformation in garnets and sulphides (pyrrhotite and chalcopyrite).
The sulphides in the amphibolite are mainly disseminated and aligned with foliation planes, are either interstitial to amphibole crystals, infill the cracks of garnet porphyroblasts together with quartz, concentrated in pressure/strain shadows, or form veinlets parallel to the rock schistosity, with quartz, chlorite, and carbonates.
The semi-massive sulphide horizon is represented by rounded fragments of the host rocks within a pyrrhotite matrix with lesser amounts of chalcopyrite and minor pyrite and sphalerite. Massive sulphide orebodies in shear zones are also described in Fornas and Manoca, further west of Touro. The zinc contents increase significantly in this type of mineralization compared with the disseminated ore type.
Seven open pits will be developed around the arc of mineralization at Touro: Arca, Arinteiro-Vieiro, Bama, Brandelos, and three separate pits in the Monte de las Minas area.
The mineralization at Arinteiro is hosted in a single ore zone of garnet amphibolite of roughly N-S to N20E orientation and dipping around 25° to the East. The mineralized garnet amphibolite is flanked by paragneiss in both hanging wall and footwall.
Average thickness of the ore zone ranges from 20 meters up to a maximum of 56 meters (mineralized intersection in drill hole IAR11) and it appears to end at depth towards the east. Average grade is 0.62% Cu. Sulfide mineral assemblage is represented by pyrrhotite, chalcopyrite and minor pyrite.
The Arinterio deposit is aligned with and extends to the Vieiro deposit to the north along a N170 trend.
Vieiro is located immediately north of Arinteiro deposit. The mineralization is also hosted in garnet amphibolite that occurs as interdigitated lenses within the paragneisses, therefore making the geometry of the orebody more complex than Arinteiro. This complexity is responsible for significant variations in thickness of the ore zone. The general dip of the ore zone is 25° to the east, but on the northern side of the deposit the structure plunges around 15° to the north.
Maximum ore zone thickness intercepted by Atalaya Mining drilling is 56 meters at 0.60% Cu with the best grade intersection of 16 meters at 1.46% Cu.
Bama is located on the hinge zone and western limb of the anticline. Mineralization is also hosted in garnet-rich amphibolite and flanked by paragneisses. It consists of disseminated pyrrhotite and chalcopyrite. Thickness of the mineralized ore zone varies from 15 meters up to 60 meters.
In Atalaya's opinion, the main Bama ore zone has a "graben-like" geometry that is thought to be associated to synsedimentary faults. The shape of the orebody is gently adapted from the margin of the deposit to the center, where the orebody has a greater thickness.
Brandelos is located in the western limb of the anticline and dips gently to the west about 10° to 20°. The ore zone is hosted in garnet amphibolite and flanked above and below by paragneisses. The ore zone forms a tabular lens with thickness varying between 15 to 50 meters and average grade of 0.40% Cu. Brandelos is the western extension of the Bama ore zone and remains open to depth down-dip to the west.
Area is located in the west-central part of the Project area and connects with Monte das Minas to the north.
Drilling has identified the occurrence of several mineralized lenses, of which the biggest one is located on the western part of Arca. The ore zones are sub-horizontal in the central area, and dip 20°-30° to west in the western side. Most of the lenses are garnet amphibolite with thickness varying from 10 meters up to 100 meters with an average grade of 0.42% Cu. The thickest drill hole intersection of Atalaya Mining drilling is 112 meters at 0.46% Cu. The lower mineralized horizon is represented by breccia textured semi-massive sulphides hosted in paragneiss.
Monte das Minas is located in the northern zone of the project area, mostly in the hinge zone of the antiform, this deposit is the extension of the Arca ore zone.
The deposit consists of up to 5 lenses of disseminated sulfides, the upper ones hosted in garnet amphibolite and the lower one in paragneiss. The lenses are sub-horizontal and occur at shallow depths, ranging in width between 10 meters and 60 meters. Average grade is 0.45% Cu, although there are some high-grade zones with up to 1% Cu.