Josemaría Copper-Gold Project

  • Asset Overview

    The Josemaría deposit is located in the Andes Mountains of  San Juan Province, Argentina. The project is located about 10km from the Chilean border and the shortest access to the Project is from Copiapó Chile, a driving distance of about 170 km, or three hours.  Access from Argentina is by major provincial highways and dirt roads from the city of San Juan, Argentina.  Copiapó has a population of approximately 150,000 people, an airport with daily scheduled flights to Santiago and Antofagasta, and companies that offer mining and exploration services.  While farther away, San Juan, Argentina, is also a major mining centre with good mining services available.

    The climate in the Project area is dry to arid and the temperatures are moderate to cold.  Annual precipitation is about 250 mm, with snow at higher altitudes in the winter.  Exploration fieldwork is generally carried out from mid-October to early May.  It is anticipated that once, and if a mine is developed and constructed, mining operations would be conducted year-round.

  • Geological Profile

    Josemaria is a copper-gold (Cu-Au) porphyry system. 

    The copper-gold mineralization at Josemaria is mostly hosted by a Miocene porphyry system which forms an elongated body with minimum dimensions of 800 to 900 m north-south, 600 to 700 m east-west and 600 to 700 m vertically. The porphyry has been dated at approximately 24.7 Ma. The deposit is centered on a composite porphyry stock, which intrudes rhyolitic volcanic and tonalitic plutonic rocks of assumed Permo-Triassic age. The earlier, more intensely quartz- ± magnetite-veined porphyry phases and nearby wall rocks display a telescoped sequence of alteration-mineralization zones, from shallow advanced argillic (mainly quartz-pyrophyllite) and underlying sericitic to deeper chlorite-sericite and minor remnant potassic; all are mineralized, but the highest copper and gold grades are present as a low-arsenic, high-sulfidation assemblage in the quartz-pyrophyllite and quartz-sericite alteration. The outermost parts of the copper-gold-zone are overlapped by a pronounced molybdenum-bearing annulus.

    The deposit was partially unroofed, and then covered within 2 m.y. by redbed conglomerate and sandstone capped by felsic tuff and lava. Following erosional removal of the volcanosedimentary strata from the northern and central parts of the deposit, a north-trending, post-mineral fault zone localized an economically important zone of supergene chalcocite enrichment in the northern part of the deposit. 

    The Josemaria deposit remains open to the south, beneath a thickening cover of post-mineral volcanic rocks, and also at depth.

    A detailed description of the Josemaria deposit geology was published in the May 2019 edition of Economic Geology and can be accessed here.

  • Exploration History


    Josemaria is a grass roots discovery made by Josemaria Resources Inc.  (formerly NGEx Resources Inc., “NGEx”) during the initial drilling campaign in 2004.  The first hole drilled encountered 280 metres grading 0.61% copper and 0.51 g/t gold, clearly indicating that a significant copper-gold deposit had been found.


    Work programs conducted at Josemaria include geological mapping; soil, rock-chip, and talus sampling; a number of geophysical surveys including induced polarization (IP)–resistivity, magnetometer, and Mount Isa Mine’s Distributed Acquisition System methodology (MIMDAS) surveys; reverse circulation (RC) and core drilling, and Mineral Resource estimation.  A number of environmental baseline studies have also been undertaken. 


    Ten drilling campaigns have been carried out at the Josemaria deposit, from 2003 to 2019. Drilling at the Josemaria deposit to date totals 71,720 m in 171 drill holes, of which 48 holes (17,535 m) are RC holes, and 123 holes (54,185 m) are core holes.

  • PFS Summary

    Pre-Feasibility Study

    Pre-Tax NPV (8%) & IRR $2.9Billion NPV
    21.4% IRR
    After-Tax NPV (8%) & IRR $2.0Billion NPV
    18.7% IRR
    Undiscounted After-Tax Cash Flow (LOM) $6.6 Billion
    Payback Period from start of processing
    (undiscounted, after-tax cash flow)
    3.4 Years
    Metal Prices Assumed $3.00/lb Cu
    $1,300/oz Au
    $20.00/oz Ag
    Initial Capital Expenditures (rounded) $2,761 Million
    LOM Sustaining Capital Expenditure (excluding closure) $860 Million
    LOM C-1 Cash Costs (By-Product) $1.26/lb CuEq
    Nominal Process Capacity 150,000 t/d
    Mine Life 20 Years
    Average Annual Metal Production (rounded)
    First 3 Years
    (full production)
    Life of Mine
    170,000 t Cu 125,000 t Cu
    350,000 oz Au 230,000 oz Au
    1,000,000 oz Ag 790,000 oz Ag
    LOM Average Process Recovery 86% Cu
    71% Au
    59% Ag

    Mining and Processing

    The Pre-feasibility Study for the Josemaría Copper-Gold Project, San Juan Province Argentina – Dec 19, 2018 (effective Nov 20, 2018), contemplates conventional open pit mining methods using autonomous haul trucks.  Mine planning incorporates stockpiling strategies to focus on the early extraction of the highest-grade ore in addition to deferring waste stripping.  Including pre-stripping, the open pit will be in operation for 23 years, delivering ore to the mill for 20 years, with a life of mine strip ratio of 0.71:1.   A maximum mining rate of approximately 115 Mt per year (including waste) is required to provide the nominal 150,000 tonnes per day of ore to the mill.  A total of 1,008 Mt of ore is expected to be processed over the life of the mine.

    Primary crushed ore will be transported via surface conveyor to a coarse ore stockpile, and then transferred to the process plant.   The process considers the use of HPGR’s as part of a three-stage crushing circuit, followed by conventional ball mill grinding and sulphide flotation.  Design throughput is 150,000 tonnes per day.  Water obtained from the concentrate thickener, tailings thickener and concentrate filter will be recovered and sent back to the process plant to be used as make-up water.

    The proposed PFS production schedule and metal production profile is shown on the attached figures.  Note: the project assumes a 30-month construction period, which would begin mid-way through Year 1.

    PFS Economic Results

    Technical Reports

    PFS - Full Technical Report

    Pre-Feasibility Study, December 2018

    Reserve Statement from PFS, December 2018

    Resource Statement from PFS, December 2018

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