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Camino Rojo |
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Zacatecas, Mexico |
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Au Ag
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Camino Rojo gold - silver deposit is located in the Municipality of Mazapil, State of Zacatecas, near the village of San Tiburcio, 190 km NE of the city of Zacatecas, 48 km SSW of the town of Concepcion del Oro, Zacatecas and ~550 km NNW of Mexico City (#Location: 24° 9' 49"N, 101° 29' 52"W).
The deposit is interpreted to represent intrusive related, clastic sedimentary strata hosted, polymetallic Au, Ag, As, Zn and Pb mineralisation, although only Au and Ag are of potential economic significance.
For a brief overview of the distribution and character of the deposits in the carbonate replacement and related vein/breccia Pb-Zn-Ag belt in Mexico and the western United States, and links to other deposits of that belt, see the Regional Setting section of the Fresnillo record.
The Camino Rojo Au-Ag-Zn-Pb deposit is located at the boundary between the Mesa Central physiographic province and the Sierra Madre Oriental fold and thrust belt in central Mexico, between splays of the regional, NW trending San Tiburcio fault zone. The bedrock geology of the Camino Rojo deposit area is almost entirely masked by colluvial cover which overlies folded marine limestone of Late Jurassic to Cretaceous ages. Mineralisation at Camino Rojo is hosted by Cretaceous submarine sedimentary, dominantly clastic, rocks. The principal host to mineralisation is the Caracol Formation, a rhythmically interbedded sequence of weakly calcareous turbiditic sandstones, siltstones and shales. The underlying Indidura Formation, comprises regularly bedded reduced siltstones and shales, whilst the unit below that, the Cuesta del Cura limestone is now recrystallised to white fine grained marble, and hosts a minor amount of sulphide mineralisation, but are inconsequential hosts of oxide mineralisation. For more detail on the stratigraphy see the Peñasquito record.
Mineralisation corresponds to zones of sheeted sulphidic veins and veinlet networks, creating a bulk-mineable deposit. It is situated above, and extends down into, a zone of feldspathic hornfels developed in the sedimentary strata, and in variably mineralised dacitic dykes. Drill core inspection suggests the mineralisation is multi-phase, comprising up to 4 separate but related pulses, and is controlled by bedding and fracturing. The sandy and silty beds of the Caracol Formation turbidite sequence are preferentially mineralised, where disseminated and semi-massive stringers of pyrite are also observed, interpreted to be the result of their greater porosity and permeability relative to the enclosing shale beds. The presence of fracturing in these permeable units suggests hydraulic over-pressuring. Basal turbiditic sandstone beds are often preferentially mineralised. The discordant open space filling fractures and structurally controlled breccia zones host banded sulphide veins and sulphide matrix breccias, whilst some higher grade vein and breccia zones are localised along the margins of dacitic dykes. Mineralisation in drill core has been recorded over vertical intervals of >400 m, distributed over a broad NE-SW elongated zone that is ~300 m wide and 700 m long. Skarn mineralisation has been encountered in the deeper portions of the system with geologic and geochemical characteristics interpreted to be consistent with those of a distal oxidised gold skarn deposit.
Oxidation varies from complete in the uppermost 100 to 150 m of the deposit, generally underlain or surrounded by mixed oxide and sulphide mineralisation for a further ~100 m. The latter occurs where oxidation is complete along fracture zones and within permeable strata, but only poorly developed to absent in the remainder of the rock. This zone is generally underlain by a sulphide zone in which no oxidation is observed. The sandy layers of the turbiditic sequence are preferentially oxidised, creating a stratigraphically interlayered sequence of oxide and sulphide material at the cm scale, with oxidation along structures affecting all strata. Thus, as the coarser permeable clastics of the Caracol Formation are also preferentially mineralised, the gold bearing portion of the rock in the transition zone of mixed oxidation is preferentially oxidised leading to near complete oxidation, whilst the gold poor impermeable and weakly fractured facies are largely unoxidised. Consequently the metallurgical characteristics for gold extraction in the mixed oxide/sulphide zone is similar to that of the upper completely oxidised material.
NI 43-101 compliant Ore Reserves and Mineral Resources at Camino Rojo as at 7 June 2019 (Orla Mining Resources and Reserves 2022 Report) were:
Proved + Probable reserves
67.363 Mt @ 0.73 g/t Au, 14.5 g/t Ag, for 49 t of gold and 980 t of silver.
Measured + Indicated resources
Oxide - 96.640 Mt @ 0.71 g/t Au, 12.7 g/t Ag,
Sulphide - 258.803 Mt @ 0.88 g/t Au, 7.4 g/t Ag, 0.07% Pb, 0.26% Zn,
TOTAL - 353.443 Mt @ 0.83 g/t Au, 8.8 g/t Ag, for 294 t of gold and 3110 t of silver.
Inferred resources
Oxide - 4.355 Mt @ 0.86 g/t Au, 5.8 g/t Ag,
Sulphide - 56.564 Mt @ 0.87 g/t Au, 7.5 g/t Ag, 0.05% Pb, 0.23% Zn,
TOTAL - 60.919 Mt @ 0.87 g/t Au, 7.4 g/t Ag, for 53 t of gold and 450 t of silver.
NOTE: Mineral Resources are inclusive of Ore Reserves.
The information in this summary is largely drawn from "Gray, M.D. and Defilippi, C.E., 2018 - CSA NI 43-101 Technical Report on the Camino Rojo Gold Project, Municipio of Mazapil, Zacatecas, Mexico; Prepared by Kappes, Cassiday and Associates for Orla Mining Ltd., 77p."
The most recent source geological information used to prepare this decription was dated: 2018.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Camino Rojo
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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