Small scale mining at the nearby North Star Mine started in the 1949 and continued until 1970. That mining sparked exploration activity, mainly in the form of geophysics and drilling, which was carried out by Asarco, Magma Copper and Phillips Petroleum in the 1960s and 1970s. Although a large zone of disseminated copper mineralization was found in the area east of the North Star Mine, it appears that this mineralization was not further assessed and it remains a largely untested, but prospective target.
Original exploration company records held by the Geological Survey of Arizona indicate past drilling at Cora intersected oxide copper mineralization over widths in excess of 100m, beneath shallow alluvial cover, over an area of at least 1km by 1km. Intervals include:
- DH5: 99.7m (327ft) @ 0.28% Cu, below 10.7m of alluvial cover (California Steel Co., 1950s)
- DH4: 39.6m (130ft) @ 0.38% Cu, below 47.2m of alluvial cover (California Steel Co., 1950s)
- DH1: 225.5m (740ft) @ 0.29% Cu, below 42.7m of alluvial cover (California Steel Co., 1950s)
Drilling results are historical in nature and have not been verified by a "qualified person" as defined by National Instrument 43-101. Drill locations are determined from maps with local grid coordinates of the day which cannot converted to modern coordinates with a high degree of accuracy. Results therefore should not be relied upon and should only be considered an indication of the mineral potential of the project.
Geological logs from holes drilled by Magma Copper Co. immediately west of Cora, indicate copper mineralization may be associated with highly altered, possible Laramide aged intrusions, consistent with a potential porphyry copper setting and analogous to many large copper deposits in Arizona.
Mapping by Magma Copper Co. identified propylitic, argillic and potassic alteration within Laramide-aged granite and monzonite intrusive rocks to the south of the North Star Mine and west of Cora, along with regular copper occurrences.
Geophysical surveys (gravity, CSAMT) were completed in the vicinity of the North Star mine by Equinox Exploration Corp in 2010 to map the thickness of cover. Based on this information, thickness of cover is expected to range between 50m and 100m at Cora.
Past exploration was predominantly focused on the fault-hosted North Star copper mine. Drilling identified a significant zone of structurally controlled copper oxide mineralization that extends below cover into the ground held by Aguila. Early explorers interpreted mineralization to be associated within detachment faults, however, a review of all available historical data by Aguila indicates a possible porphyry copper-molybdenum association.
The Aguila review noted:
- Diamond drill logs from Magma Copper Co. describe altered intrusive rocks (monzonite, diorite, latite porphyry) throughout several drill holes, with alteration described as argillic in nature, more consistent with a porphyry copper setting;
- The lack of reported specular hematite associated with mineralization is inconsistent with a detachment fault model as this is a very common accessory mineral in detachment fault hosted deposits in Arizona and Nevada;
- The local presence of Laramide aged intrusions, which are associated with all major porphyry copper deposits in Arizona; and
- The structural association with local porphyry deposits and intrusions.