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Peñasquito is a world class deposit within an intrusive related breccia body (pipe) complex and associated fracture systems. In the region, Tertiary granodioritic intrusive stocks cut through Paleozoic schist which are unconformably overlain by a thick sequence of Mesozoic limestone, shale and siltstone. The intrusive activity produced a variety of breccia bodies. These breccia bodies were later intruded by felsic dikes.
Peñasquito is a very large mineral system. Mineralization at Peñasquito is mostly in fractured and brecciated siltstone within, and adjacent to breccia bodies, associated intrusives and intrusive clast breccia. The Peñasco deposit is almost entirely within a breccia pipe with a one kilometer diameter. Within one kilometer to the southeast of the Peñasco breccia pipe is a second slightly smaller breccia pipe. On the western side of this second pipe is the Chile Colorado deposit. This deposit is entirely in fractured siltstone.
The ore minerals in both deposits consist of sphalerite, galena, argentite and minor chalcopyrite and pyrite. These ore minerals contain the gold, silver, lead and zinc that will be produced. The ore minerals occur along fractures, filling cavities between breccia fragments and disseminated in the intrusives. Gangue minerals are sparse and where present can consist of calcite, fluorite and rhodocrosite. The Peñasco deposit mineralization has been identified, to date in the eastern half of the Peñasco breccia body and to a depth of 800 meters. The western half remains to be tested. Mineralization has also been identifed adjacent and northwest of the Peñasco breccia pipe. This area is called Sotol and mineralization is associated with a northeast trending fracture zone, containing mostly gold and silver with little lead and zinc. Mineralization has also been identified in the Chile Colorado breccia pipe adjacent and east of the Chile Colorado deposit. The Chile Colorado deposit has less gold than at Peñasco. To date, higher gold concentrations have been recognized near pipe edges. This part of the Chile Colorado pipe has not been properly tested with drilling. Mineralization has also been identified on the eastern side of the Chile Colorado breccia pipe. This area is called Las Palmas and has been sparsely drilled. All of these areas of mineralization are part of one large mineralizing system that so far lacks thorough testing.
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