Siembra Minera (Brisas-Cristinas) Project

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Mine TypeOpen Pit
StagePreliminary Economic Assessment
  • Gold
  • Copper
  • Silver
Mining Method
  • Truck & Shovel / Loader
Mine Life... Lock
SnapshotThe Project is a combination of the Brisas and Cristinas properties into a single project now called the Siembra Minera Project.


Gold Reserve Inc. 45 % Indirect
Corporacion Venezolana De Mineria, S.A. 55 % Indirect
Empresa Mixta Ecosocialista Siembra Minera, S.A (operator) 100 % Direct
The operating company Empresa Mixta Ecosocialista Siembra Minera, S.A., which holds the rights to the Siembra Minera Project, is a mixed capital company with 55% being owned by a Venezuelan state entity [owned by the Bolivarian Republic of Venezuela through the Corporación Venezolana de Minería] and 45% by GR Mining Barbados, Inc., a wholly-owned subsidiary of Gold Reserve Inc.

Deposit type

  • Porphyry


A possible deposit analogy is of a copper porphyry forming over a magmatic source (yet to be discovered) that was very rich in boron. A peraluminous granite might fit the boron requirements and a sufficient volume of basaltic/andesitic rock could provide the copper. Thin lenses of high Cu and Mo extending away along bedding/foliation planes could be the result of periodic high confining pressures within the Blue Whale that forced mineralizing fluids outward along these planes. The fluids replaced crystals and lithic fragments, evidence of which can be viewed in drill core.

There are four distinct types of gold and copper mineralization present at Brisas, defined by geometry, associated minerals, and the gold-copper ratio. These zones are the Blue Whale body, disseminated gold + pyrite ± copper, disseminated high copper, and shear-hosted gold. Only the first three types are encountered within the proposed pit geometry.

The Blue Whale mineralized body is a discrete, sharply bounded, flattened, cigar-shaped feature that trends more or less parallel to the local schistosity and plunges approximately 35° southwest.

Mineralogically, the Blue Whale is a sericite- tourmaline-pyrite-chalcopyrite-quartz schist, with a smaller volume of quartz-tourmaline-sulphide breccia.

The bulk of mineralization occurs in disseminated, coalescing, lensoid bodies, and high in gold and in most cases low in copper. These bodies lie almost exclusively in the lapilli-rich, rapidly alternating sequence of tuffaceous units and are clearly aligned along foliation. Together, these lenses form a generally well defined mineralized band, which mimics the dip of the foliation/bedding and remains open at depth. It remains at a similar thickness from the northern concession boundary for a distance of 1.4 km south, after which, it tapers rapidly. Alteration minerals characteristic of these lenses are epidote, chlorite, secondary biotite, and sericite.

Stratiform lenses of high copper with or without high gold underlie the gold+pyrite lenses described above. These lenses outcrop in the northern part of the deposit, and plunge to the south in a manner similar to the Blue Whale and high gold/low copper lenses but with variable dips.

Shear-hosted gold occurrences exist in the southern part of the concession, running parallel to the foliation as with mineralization further north. Stratigraphically, they occur above the large disseminated lenses previously described. The gold and copper grades are erratic and discontinuous.

In terms of classification, Cristinas has been assigned to shear zone-hosted systems by some geologists, and to a porphyry association by others; however, several key elements of the Cristinas deposit must be satisfied in any attempt to classify the deposit.

The main two styles of mineralization present at Cristinas are:
1. Stratiform mineralization at Conductora, Morrocoy, and Cordova.
2. Hydrothermal breccia-hosted mineralization at Mesones-Sofia.

The Conductora (including Cuatro Muertos and Potaso), Morrocoy, and Cordova areas contain over 95% of the gold resource at Cristinas.

Mineralization occurs in a greater than three- kilometre long, north-trending zone that dips moderately (30° to 40°) to the west, sub-parallel to the volcanic stratigraphy and to the pervasive (S1) cleavage. Gold mineralization is associated with a sulphide assemblage that consists essentially of pyrite and chalcopyrite.

Mineralization in Mesones-Sofia is concentrated in the quartz-tourmaline-sulphide-calcite vein breccias and extends laterally into the adjacent country rocks. The breccias are sufficiently closely spaced that the country rock between them also constitutes ore in the central part of Mesones-Sofia. Grades in the country rock on the periphery of the system decrease as the distance between the breccias increase.

Discrete auriferous quartz veins are located adjacent to the Cristinas deposit. Such veins include the Los Rojas and Albino veins that lie approximately one kilometre to the east of the Conductora area, and the Hofman vein, which lies about one kilometre to the west of the Cordova area. These veins consist of quartz with gold mineralization associated with pyrite (there is no appreciable chalcopyrite). The veins have chlorite selvages about 50 cm wide. Although gold mineralization in these veins does not constitute part of the Cristinas resource, they are considered to be genetically related, and peripheral, to the Cristinas deposit.



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Mining Methods


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CommodityProductUnitsAvg. AnnualLOM
Gold Payable metal koz 83637,639
Gold Metal in conc./ doré koz 38,127
Copper Payable metal M lbs 713,198
Copper Metal in concentrate M lbs 3,339
Silver Payable metal koz 36916,615
Silver Metal in conc./ doré koz 17,085

Operational metrics

Daily mining capacity 400,000 t *
Daily processing capacity 182,000 t *
Stripping / waste ratio 1.16 *
Waste tonnes, LOM 2,320,350 kt *
Ore tonnes mined, LOM 2,004,741 kt *
Total tonnes mined, LOM 4,325,091 kt *
Tonnes processed, LOM 2,004,741 kt *
* According to 2018 study.

Production Costs

Credits (by-product) Gold USD -262 / oz *  
Site cash costs (produced) Gold USD 495 / oz *  
Cash costs Gold USD 542 / oz *  
Cash costs Gold USD 280 / oz * **  
Total cash costs Gold USD 428 / oz * **  
All-in sustaining costs (AISC) Gold USD 483 / oz * **  
Assumed price Copper USD 3 / lb *  
Assumed price Silver USD 17 / oz *  
Assumed price Gold USD 1,300 / oz *  
* According to 2018 study / presentation.
** Net of By-Product.

Operating Costs

OP mining costs ($/t mined) USD 1.36 *  
OP mining costs ($/t milled) USD  ....  Subscribe
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* According to 2018 study.

Project Costs

MetricsUnitsLOM Total
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OP OpEx $M USD  ......  Subscribe
Processing OpEx $M USD 9,881
G&A costs $M USD 2,654
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Heavy Mobile Equipment


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Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Mar 16, 2018
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