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Location | Ownership | Geology | History | Work by Kings Minerals 2004-2006 | Mineral Resources | Cross Sections | Preliminary Pit Outlines | Next Steps | Exploration Potential | Quality Control | Property Reports | Property Maps
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| | GEOLOGY
The San Anton Property is located within the Mesozoic Sierra Madre Oriental terrain and 80 km north of the west northwest trending Late Miocene Trans-Mexico Neovolcanic Belt. The Sierra Madre Oriental terrain is a thin skinned fold-thrust belt of Laramide age (Late Cretaceous-Early Tertiary). High level felsic intrusions emplaced into the western two thirds of the terrain provided the mechanism for hydrothermal activity and mineral deposition. The San Anton Property is known to host a variety of styles of mineral deposits, including porphyry gold-rich copper deposits, intrusion-related gold deposits, epithermal silver-gold deposits, and gold-copper skarn deposits. All of these styles of mineralization are known to occur within the property concessions held by SAM. Historic mining within the San Anton de las Minas area was concentrated on epithermal veins. However, the main area of present interest is the large low grade bulk mineable gold-silver-copper deposit at Cerro del Gallo where a significant mineral resource has been identified.The Cerro del Gallo gold-silver-copper deposit lies within an inlier of deformed clastic sediments and volcanic rocks of probable Triassic-Jurassic age. At Cerro del Gallo, an ash-flow tuff sequence has been intruded by a small elongated upright felsic stock of dacitic to tonalitic composition. The enclosing host rocks have undergone strong pervasive hydrothermal alteration generating a new potassic fine grained replacement assemblage of quartz, K-feldspar, sericite, biotite, pyrite, pyrrhotite, and chalcopyrite. Gold mineralization is concentrated within a gold-rich annulus within wallrock proximal to the felsic intrusion. A gold-bearing skarn has been intersected in drilling south of Cerro del Gallo. Other targets peripheral to the Cerro del Gallo hydrothermal alteration zone remain to be tested. These include coincident magnetic and 3D-induced polarization anomalies on the flanks of the alteration system. | | |
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| | Deposit Types | | | | The Cerro del Gallo gold-silver-copper deposit can be considered to be a member of a distinct subclass of "reduced" porphyry-style copper-gold mineralization. These reduced porphyry copper-gold deposits lack primary hematite, magnetite and sulphate minerals, but contain abundant hypogene pyrrhotite, commonly have carbonic ore fluids, and are associated with ilmenite-bearing, reduced I-type granitoids. Cerro del Gallo displays all these features. In addition, there is a consistent pattern of higher temperature potassic alteration overprinted by lower temperature propylitic-style mineral alteration. Propylitic alteration boundaries are gradational and irregular, and more widespread than potassic alteration. This alteration pattern is consistent with many other porphyry copper-gold deposits throughout the world. Tellurium-bearing minerals are also common in porphyry copper-gold deposits, as they are at Cerro del Gallo. The Cerro del Gallo gold-silver-copper deposit also has characteristics supporting an intrusion related gold system ("IRGS") model. IRGS deposits are typically found in continental tectonic settings inboard of convergent plate boundaries, often where the regional metallogeny is characterized by tungsten-tin magmatic provinces, felsic intrusives have an intermediate oxidation state between ilmenite and magnetite series with a gold-enriched metal assemblage derived from igneous fractionation, and a distinctive metallogenic signature of gold, bismuth, tin and tungsten. Hydrothermal fluids are carbonic, and pyrrhotite is common. Peripheral mineralization to Cerro del Gallo consists of epithermal low sulphidation silver-gold vein-breccia deposits occurring dominantly in north northwest trending structures (Carmen-Providencia), but also east northeast (Ave de Gracia) and west northwest (La Paz) trending structures. These structures were the focus of historic mining and prospecting activities. These epithermal vein-type deposits are common in the Mexican silver-rich metallogenic belt and have been the major source of Mexican silver production. The Valenciana mine on the Veta Madre (Mother Vein), located 23 km west of the San Anton Property, was arguably one of the richest epithermal vein systems in the world. | | |
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| | Mineralization | | | | Both felsic intrusive and tuff wallrocks are mineralized at Cerro del Gallo. Mineralization is disseminated and vein or fracture controlled and extends from 200m to 400m outward from the felsic intrusive. Fluid overpressuring led to brittle fracturing of these rocks and subsequent development of an extensive network of fine fractures and stockwork vein development. There are at least two periods of fracturing and veining. The strongest mineralization is associated with quartz stockwork veining within the wallrock annulus around the felsic stock, and diminishes outward accompanied by reduced fracture density and quartz veining. Sulphides make up less than 2% by volume of the mineralized rocks. Mineralization is zoned concentrically around the felsic intrusive with higher grade gold mineralization within a wallrock annulus proximal to the felsic intrusion, and higher grade copper mineralization outwards of the gold zone. In general there is an antipathetic relationship between gold and copper grade. Zinc mineralization is anomalous outside the copper zone. Metal zonation boundaries are gradational and there is an overlap in the gold-copper zone and the copper-zinc zone. Molybdenite is rarely observed, but where present is found in the felsic intrusive and silicified contact with the wallrock tuffs. | | |
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