The Gaby-Totito project is in the Chilean Coastal IOCG Belt, approximately 40km north of the city of La Serena in Coquimbo province. It represents a mid- stage copper-iron-gold-cobalt exploration project, with significant drill intersections to date from 12 holes for 4,058m. Combined with available geophysical datasets (IP and ground magnetic), these intersections indicate the presence of a large well-mineralised kilometre-scale IOCG system at the Gaby target. The best copper intersections from historic drilling are as follows:
- LH-RC-07 – 285m @ 0.40% copper, 0.08 g/t gold, 23.5% iron and 259 ppm cobalt from 100m depth (start of assaying), including 52m @ 0.60% copper, 0.12 g/t gold, 25.1% iron and 302ppm cobalt from 190m.
- LH-RC-06 – 36m @ 0.66% copper, 0.14 g/t gold, 32.1% iron and 328 cobalt from 196m depth, and 36m @ 0.46% copper, 0.11 g/t gold, 31.2% iron and 304 ppm cobalt from 264m.
Both of these intersections are from holes on the northernmost drill section, with the mineralisation open to the north under thin gravel cover. Tribeca’s immediate focus is on testing the extent and grade of the mineralisation to the north, with the geophysical data (IP chargeability) suggesting mineralisation continues under the thin gravel cover.
The project comprises 12 mining permits for a total of 822 hectares, adjacent to the company’s Caballo Blanco project (Fig. 1). A five-year option to purchase 100% of the project is held by Tribeca’s majority-owned Chilean subsidiary, Bluerock SpA. Bluerock is owned 62.5% by Tribeca Resources and 37.5% by a group of private investors.
Geology and Mineralisation
The Gaby target is located in the floor of the Choros valley, with outcropping to sub-cropping Jurassic-Cretaceous host rocks locally covered by thin gravels. The outcrop is dominated by aphanitic or porphyritic andesites (Fig. 1) (interpreted as equivalents to the Formacion Punta del Cobre – Belmar, 2010) and granite, granodiorite or diorite of the Complejo San Juan. These units are locally mylonitised or brecciated.
Alteration is variable, but commonly strong and dominated by albite-amphibole-magnetite±epidote, locally with pyrite and chalcopyrite, or oxide copper where weathered. The alteration may be pervasive (commonly the case with albite and or magnetite) or comprise veins and stockworks (Fig. 2).
The district hosts the trace of the Atacama Fault Zone, which is comprised of a set of broadly north-south-trending wrench faults, some of which have associated breccia zones mapped in the Sernegeomin 1:100,000 scale geological mapping within the district. The trend of the main magnetite alteration system at the target is north-south, with the copper mineralisation better developed in the northern portion where this trend intersects a northwest-trending alteration and fault system that extends from the La Higuera historic mining zone to the southeast (Fig. 1). The mineralisation drilled to date at the Gaby target comprises a classic magnetite-dominated IOCG system, with chalcopyrite as the dominant copper sulphide, disseminated and in veins, and with gangue minerals comprising pyrite-magnetite-amphibole-albite and epidote. The geometry of the mineralised body is not well constrained based on drilling to date but is most likely a steeply east-dipping NNW-trending tabular body of minimum 100m thickness (at the +0.25% Cu level on section 6734500N).
Ground magnetic and Induced Polarisation (IP) surveying was completed by Peregrine at the Gaby target in 2004-2005, with lesser additional IP surveying completed in 2008. The line spacing of the 2004-2005 ground magnetic survey was 200m, with the IP survey lines spaced at 400m. The additional IP surveying in 2008 brought the IP line spacing down to 200m in the western portion of the grid.
The geophysical data indicates the system is iron (magnetite) dominated in the southern portion (the 0.5 SI magnetic susceptibility inversion shell is shown in Fig. 3), whilst the highest chargeability is to the north of the main magnetic anomaly, interpreted as coincident with a hematite-dominant northern part of the system. The copper grade increases towards the peak of the chargeability anomaly, which remains untested for 750m (based on the 20 mV/V iso-surface) under thin gravel cover to the north. Given the increasing copper grade and the untested geophysical anomaly this northern zone is a high priority target.
Twelve reverse circulation holes were drilled in 2005 for 4,058m, with three holes having diamond tails. The drill chips have been secured for all or part of 8 of the 12 holes, but the diamond core is no longer available. The significant intersections from the drilling are summarised in Table 1.
Assay data from the northernmost drill section is plotted in Figure 4. Hole RCH-LH-07 intersected a 285m interval of copper-gold-iron mineralisation, interpreted through correlation with the next drill section to the south (6734400N) as a steeply east-dipping mineralised zone. A further higher grade interval was intersected in hole RCH-LH-06 (36m @ 0.66% copper, 0.14 g/t gold, 32.1% iron from 196m) approximately 200m to the east, but the geometry or relationship of the two mineralised zones is unclear.
Review of the drill chips suggest the base of oxidation in this area is between 24-34m downhole depth.
Metallurgical Test Work
G&T Metallurgical Services Ltd completed a metallurgical test work program in 2006. The program comprised optical mineralogy, grinding, flotation and magnetic separation test work, assaying, and reporting. The work indicated the mineralisation intersected to date at Gaby is amenable to production of a copper concentrate and a high grade magnetite product (66-70% Fe) through standard flotation and magnetic separation techniques, with further potential to produce a cobalt-rich pyrite concentrate.
Belmar, 2010. Informe Mapa geológico y de Alteraciones Distrito La Higuera, Internal report for Minera Peregrine S.C.M.
Competent Persons Statement
The information on this webpage is based on information reviewed by Dr. Paul Gow, Executive Director of Tribeca Resources Chile. Dr. Gow is a Member of the Australasian Institute of Mining and Metallurgy (AusIMM) and the Australian Institute of Geoscientists (AIG), and has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person under the 2012 Edition of the Australasian Code for reporting of Exploration Results, Mineral Resources and Ore Reserves.
The JORC 2012 Table 1 for information on this page and the associated news release can be downloaded in the associated release dated 3 April 2019 and available here.