Exploring the Sierra Madre of Mexico for gold and base metals.
Submarine argillite occurs in large roof pendants above alkali granite in the southwestern part of the Property. The argillite is in thrust-fault contact with Mesozoic rocks to the northeast and in strike-slip fault contact with continental volcanics to the southeast. Basaltic andesite of probable Jurassic age is intercalated with easterly trending and steeply southerly dipping psammites in the center of the Property. Monzogabbro apparently intrudes Jurassic and older rocks.
The northeastern part of the Property is underlain by pyroclastic rocks that have a Campanian age of about 74 Ma measured using U-Pb isotopic dating methods of contained zircon under the supervision of Dr. Martín Valencia-Moreno of Universidad Nacional Autónoma de México (UNAM). These are correlated to the Socavón member of the Tarahumara Volcanic Arc. On the Property, the Socavón volcanics are perhaps 1000 meters thick and mostly dip northeasterly at about 50°.
A plutonic complex mineralized with chalcopyrite-molybdenite stockworks is the dominant geological feature of the western part of the Property. The most abundant rock type is hornblende granodiorite with a Paleocene age of 66.3 Ma measured from U-Pb isotopic dating of zircon by Dr. Martín Valencia-Moreno. Molybdenite was dated using Re-Os isotopic methods and yielded a near-identical age of 66.3 +/- 0.33 Ma.
The major structural element of the Property is a northeast trending fault (Cocolmeca Fault) that juxtaposes Paleocene bimodal rocks to the southeast against older rocks to the northwest. A U-Pb zircon date of 62.6 Ma was obtained from rhyolitic lapilli-tuff near Urrea Mine adit. Pyroclastic rocks are intercalated with shoshonitic trachyandesite lavas and intruded/overlain by flow-banded rhyolite flow-domes. Detailed stratigraphy with geochronological control is not available for this complex and highly mineralized volcanic pile.
Northwesterly trending extensional faults containing gold mineralization cut Paleocene and possibly younger pyroclastic rocks.
The most mafic plutonic rocks are chalcopyrite-mineralized quartz monzonites of unknown age exposed in the Arroyo Picachos near the southwest Property boundary. Other intrusions mainly form dikes and apophyses that cross-cut older plutonic and volcanic rocks. These include aplite, orbicular monzonite porphyry and cupiferous alkali quartz granite porphyry.
Finally, some of the youngest porphyries on the Property are porphyritic dikes with magnetic black xenoliths that appear similar to the 45 Ma Bolaños Dikes at Tayoltita. The structures intruded by these dikes can also be intruded by magnetic mafic dikes of possible Oligocene or Miocene age.