Summary:
The Santa Cruz Copper Project consists of four separate areas of interest along a southwest-northeast trend which continues in line with the neighbouring historical Sacaton mine. These areas, from southwest to northeast, are referred to as (1) the Southwest exploration area, (2) the Santa Cruz deposit, (3) the East Ridge deposit, and (4) the Texaco deposit. Each of these deposits or areas represents portions of one or more porphyry copper systems that have been dissected and separated as a result of extensional Basin and Range normal faulting. Likewise, each area has experienced variable periods of erosion, supergene enrichment, fault displacement, and tilting into their present positions due to Basin and Range extensional faulting.
Mineral reserves have been identified for two deposits: Santa Cruz and East Ridge.
The Santa Cruz Copper Project is situated within the Southwestern Porphyry Copper Belt, which is home to numerous productive copper deposits.
Mineralization in the project area is divided into the following:
• Supergene copper oxide mineralization mainly consists of atacamite and chrysocolla, with smaller amounts of cuprous goethite, copper-bearing smectite clays, tenorite, cuprite, copper wad, and native copper.
• Secondary supergene sulphide mineralization is dominantly chalcocite, which replaces hypogene sulphide.
• Primary hypogene sulphide mineralization consists of chalcopyrite and molybdenite hosted within quartz-sulphide stringers, veins, and breccias.
Santa Cruz Deposit
The Santa Cruz deposit is approximately 2,000 m long and 700 m wide. Mineralization occurs from about 400 m below the surface at 0 m above sea level to a depth of approximately -600 m below sea level.
Supergene
The uppermost exotic copper mineralization is primarily hosted in overlying clastic and volcanic rocks. The supergene stratigraphy comprises zoned mineralization, with chrysocolla at the top, followed by atacamite, and then chalcocite. There is evidence of post-rotational supergene enrichment horizons, indicating two or more supergene sulphide events.
Hypogene
Primary sulphide mineralization includes chalcopyrite, pyrite, and minor molybdenite, which are hosted in quartz-sulphide stringers, veinlets, veins, and breccias. Additionally, finely to coarsely disseminated copper sulphides are found within vein envelopes associated with hydrothermal porphyry mineralization.
East Ridge Deposit
The East Ridge deposit consists of discrete subparallel zones. East Ridge North occurs as four dipping, subparallel zones from 4 to 8 m thick, 500 to 700 m long along strike, and 300 to 600 m extent along dip with an average dip of 35° to 45°. East Ridge South consists of two shallowly dipping, subparallel zones from 5 to 15 m thick, approximately 300 m long along strike and 600 m in extent down dip with an average dip of 15°.
Supergene
Correlative and partially displaced from the Santa Cruz deposit. Supergene sulphide mineralization consists of thin, stacked intervals displaced from those in the Santa Cruz deposit by Basin and Range faulting. Chrysocolla and atacamite is broadly distributed near the fault-controlled paleo valley between the Santa Cruz and East Ridge deposits.
Hypogene
Primary sulphide mineralization is correlative and displaced from the Santa Cruz deposit and includes broad zones of low to moderate density quartz-sulphide veins consisting of chalcopyrite, pyrite, and molybdenite. Small zones of mineralized hydrothermal breccia are in the north portion of East Ridge.
Texaco Deposit
The Texaco deposit is approximately 1,500 m long and 650 m wide. The highest intercept of mineralization occurs at about 450 m below surface at -50 m below sea level, while the deepest intercept is at approximately -720 m below sea level. The deposit is tabular and dipping, and these dimensions represent the highest and lowest intersections of mineralization with an average thickness of 150 m.
Supergene
Supergene mineralization at Texaco contains significantly less copper oxide and copper chloride mineralization compared to the Santa Cruz deposit, although a well-developed leached cap exists. Veined and disseminated chalcocite exists in sub-horizontal blankets that have been tilted due to faulting and extension.
Hypogene
Primary sulphide mineral assemblages consist of chalcopyrite, pyrite, molybdenite hosted in quartz-sulphide veins, veinlets, vein breccia and breccias, as well as fine to coarsely disseminated sulphides within vein envelopes. Chalcopyrite and pyrite occur as sulphide cement within breccias. Hypogene mineralization at Texaco forms a distinct zoning pattern of chalcopyrite-molybdenite to chalcopyrite to pyrite from core to shell.
Southwest Exploration Area
The dimensions of the Southwest exploration area are yet to be determined as the deposit boundaries remain undefined.
Supergene
Supergene mineralization at the Southwest exploration area consists of weakly disseminated and partially enriched sulphides with chalcocite and/or bornite rims.
Hypogene
Hypogene mineralization within the Southwest exploration area is characterized by limited drilling that encountered bedrock at approximately 1,000 m depth. Sulphide mineralization includes pyrite and chalcopyrite that occur as chemical cement within a magmatic-hydrothermal breccia and sparse quartz-sulphide veining.
Deposit Types
Porphyry Copper
Primary hypogene mineralization occurs as disseminations and in stockworks of veins, in hydrothermally altered, shallow intrusive complexes and their adjacent country rocks (Berger et al., 2008). Sulphides of the hypogene zone are dominantly chalcopyrite and pyrite. The hydrothermal alteration zones and vein paragenesis of porphyry copper deposits are well-known and provide an excellent tool for advancing exploration.
Supergene Enrichment
The project area has a history of oxidation and leaching that resulted in the formation of enriched chalcocite horizons, and later stages of oxidation and leaching, which modified the supergene copper mineralization by oxidizing portions of it in place and mobilizing some of the chalcocite to a greater depth. This process is associated with descending water tables and or erosion and uplift of the system, or changes in climate, or hydrogeological systematics.