The Marimaca copper oxide project, located in the Antofagasta Region of northern Chile, close to the coast and major infrastructure, is a 1 hour drive north of the Port of Antofagasta and 22 kilometres from the port of Mejillones. It is 14 kilometres from the Antofagasta to Tocopilla paved highway (and is centred on UTM coordinates: 374,800 E and 7,434,900-N).
No previous exploration drilling had been done on this property prior to Coro’s involvement. in this property. Broad zones of copper oxide mineralization, well-exposed on the hillside, were being mined by local artisanal miners via open pit methods. Coro’s experienced exploration team recognised that this property would provide a significant and low-risk target that met the Coro criteria - a viable leachable copper oxide resource which could be rapidly defined, in an excellent location, all of which could ensure limited impediments for an expeditious development.
In August 2016, following a 60-drill hole exploration program, Coro announced the new discovery at Marimaca.
A maiden resource estimate for the Marimaca 1-23 claim only was released in January 2017 and updated and expanded in April 2018. Additional resource potential is present on adjacent 100% Coro controlled properties and Coro intends to aggressively explore this during 2018-19 with a view to materially increasing the resource base of the Marimaca project.
Coro can acquire a 75% interest in a local Chilean private company, Compañia Minera Newco Marimaca (“CMNM”) which owns the Marimaca 1-23 mining claim, on completion of the following terms;
- 51% interest earned with a $125,000 payment together with completion of a NI43-101 resource estimate and engineering study that demonstrates the technical and economic feasibility of producing a minimum of 1,500 tonnes per year of copper cathode by August 6th 2018 at Coro’s cost.
- An additional 24% interest may be earned by Coro upon obtaining financing for the project construction or by vending into CMNM a processing plant with a minimum capacity of 1,500 tonnes per year cathode copper.
- The owner’s interest will comprise a 15% interest free carried to commencement of commercial production and a 10% participating interest subject to dilution. The owners at their election may request Coro to loan them the equity portion corresponding to their 10% interest, if any, recoverable by Coro from 100% of the project’s free cash flow after debt repayments.
- Coro retains a first right of refusal
Coro also owns, is acquiring or has optioned a 100% interest in other mining properties covering the Marimaca project and its surroundings.
In 2017, Coro completed the acquisition of Minera Rayrock Ltda, owner of the Ivan SXEW (Solvent Extraction Electrowinning) plant with a capacity to produce 10,000 tonne per year of copper cathode, which could be used to process ore from the Marimaca copper oxide project. This plant operated from 1995 until 2012, at which time it was put on care and maintenance. The plant’s associated water rights and environmental & operating permits, some of which require updating, were included in the purchase agreement. Through the Rayrock acquisition, Coro also acquired 38,283 hectares (95,000 acres) of mineral claims on which the seller retains a 2% net smelter return (NSR). Coro acquired Rayrock for a total consideration of US$6.4 million plus an existing closure obligation of approximately US $4.5 million.
Geology and Mineralization
Marimaca is located in a belt of Mesozoic age copper deposits known as the Coastal Copper Belt, which range in (pre-mining) size from Mantos Blancos at approximately 500 million tonnes to Ivan at roughly 50 million tonnes. They occur in a variety of host rocks and have differing morphologies, but have a common Cu-Ag primary mineralogy zoned from bornite outwards to chalcopyrite and pyrite, deep oxidation and frequently, secondary enrichment.
Mineralization at Marimaca is hosted by and is related to a Jurassic intrusive complex which has been strongly affected by brittle structural deformation. These structures have a variety of orientations, with east dipping, north south orientations being dominant, that have allowed the introduction of primary sulphide mineralization, mainly chalcopyrite. Subsequent secondary enrichment resulted in the formation of a thick chalcocite blanket which is areally more extensive than the underlying primary mineralization. Continued erosion and uplift resulted in the enrichment blanket being almost entirely oxidised, again with additional dispersion of copper oxides within the structurally prepared areas. The existing resource base at Marimaca is confined to the copper oxides which have been subdivided into brochantite, chrysocolla ,copper wad domains as well as to some minor remnant mixed/enriched material.
The leachable mineralization (oxides and mixed/enriched material) is open to the north and south of the current resources.
A maiden mineral resource estimate (NI43-101 compliant), was completed by NCL Ingeniería y Construcción S.A., Chile for Marimaca in late 2016 and released in January 2017.
http://sedar.com/DisplayCompanyDocuments.do?lang=EN&issuerNo=00025132 - Technical Report for the Marimaca Copper Project, Antofagasta Province, Region II Chile, filed 24 February 2017, file size 5,972k
A significantly increased resource estimate was announced in April 2018
The resource estimate was completed by a third-party, NCL Ingeniería y Construcción at a variety of cut-off grades and the resources at a 0.20% CuT cut-off grade, presented in the following table:
|Measured + Indicated||46,754||0.65||0.44||303,698||203,869|
CuT: total copper tonnes
CuS: acid soluble copper tonnes
In Pit Resource
To demonstrate the potential economic viability of the Marimaca claim resource, a series of Whittle pit optimizations was completed utilizing appropriate operating costs, results obtained from metallurgical test work, and a variety of copper prices. The resources were estimated only for oxide and mixed-enriched copper mineralization which can be processed by heap leaching (HL) and run of mine (ROM) leaching to produce cathode copper. Due to their differing metallurgical characteristics, the resources were categorised according to mineral type. No resources were estimated for primary sulphide mineralization, occurring in deeper portions of the deposit. At a $3.50/lb long term copper price, the in pit resource was estimated to be
|Measured & Indicated|
As with the earlier 2017 resource estimate, the in pit resource is constrained by the Marimaca property limits, such that all blocks occurring outside the property were assigned a 0%CuT grade. Accordingly, the pit contains 68,271kt of waste and has a strip ratio of 1.4:1.
Sergio Rivera, Vice President of Exploration, Coro Mining Corp, a geologist with more than 32 years of experience and a member of the Colegio de Geologos de Chile and of the Instituto de Ingenieros de Minas de Chile, was responsible for the design and execution of the exploration program and is the Qualified Person for the purposes of NI 43-101. Alan Stephens, FIMMM, President and CEO, of Coro Mining Corp, a geologist with more than 40 years of experience, and a Qualified Person for the purposes of NI 43-101, is responsible for the contents of this website page.