Machado Geology


Cosigo's Machado project in the Taraira Gold Belt lies within the far southwestern edge of the Neblina successor foreland basin. Deposits within this basin were derived from the Trans-Amazonian mountain range and inferred northern sources and are dominantly mature deltaic and shallow-marine sandstones. Metasedimentary strata underlying the Machado project area are thought to belong to a group of Roraima-like outliers for which ages between 1.55 and 1.81Ga (1 Ga = 1 Billion years) have been determined at various locations. In the Machado project area the metasedimentary strata forms a ca. 1000 m-thick moderately SW-dipping monoclinal sequence assigned to the La Pedrera Formation. Throughout the region these strata have been folded into a sequence of northerly-trending anticlines and synclines. The SW-dipping strata on Cosigo's Machado project have been interpreted as the eastern limb of a syncline in which the western flank forms the neighbouring Serrania Agua Blanca.

In-situ primary gold mineralization in the Taraira Gold Belt occurs along the folded N- to NNW-trending ridges, which are comprised predominantly of quartz-arenite with minor mudstone/siltstone intercalations and metaconglomerate beds. Gold mineralization on the Machado project appears widespread along Serrania Machado ridge. Native gold is readily panned from the project area, generally in areas of minor excavations and mine workings and also from creeks which drain Cosigo's project. Grains of native gold up to 5mm in size have been observed in rock samples from the project. The Taraira Gold Belt is therefore, at least in part, a coarse gold environment characterized as one where gold grains of more than 0.1mm in diameter occur and are often erratically distributed.

Gold mineralization on the Machado property occurs as:
  • Stratabound, disseminated gold, of inferred paleoplacer and/or remobilized paleoplacer origin;
  • Epigenetic cross-cutting quartz vein-related and structurally-hosted gold;
  • Recent placer deposits, generated locally from hard-rock sources.
Cosigo believes that re-mobilization and re-deposition of detrital gold by hydrothermal solutions possibly during regional metamorphism may have been an important mechanism of gold concentration in the Taraira Gold Belt. Similar processes are known from other paleoplacer districts, such as the legendary Witwatersrand district in South Africa.

Primary gold mineralization identified to date on the Machado project appears to be strongly controlled by stratigraphy and associated with hematite-dominant Fe-oxidation. Geological mapping suggests that this oxidized zone continues along strike for more than 20 km within the Machado project. Gold mineralization is also associated with cross-cutting structures. Higher grade zones seem preferentially developed at intersections between quartz arenite strata and steeply dipping faults. Gold mineralization is locally known to be of bonanza grade, making these faults an important consideration when planning exploration programs.

Dr. Joseph Montgomery, P.Eng., Executive Vice-President of Cosigo, is a Qualified Person under NI 43-101 and is responsible for the design and execution of the programs carried out by Cosigo in the Taraira Gold Belt. Dr. Montgomery has reviewed and approved the technical content of this website for compliance with NI 43-101. The technical information included on this website is sourced from "Technical Report, Machado Project, Vaupes Department, Colombia" prepared for Horseshoe Gold Mining Inc. by Raymond M. Ashley, P.Geoph. and dated January 16, 2011.