In 2020, Pathfinder Development Corp., through its subsidiary Pathfinder Tonopah, acquired the Liberty Mine Complex.
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Summary:
The Hall(Liberty) complex is centered on a porphyry Cu-Mo system in the western flanks of the San Antonio Mountains. The Hall Stock is a multi-phase, southeasterly plunging quartz monzonite porphyry (66-70 Ma) that hosts much of the Cu-Mo mineralization. The porphyry intrudes a metamorphosed package of Late Paleozoic to Early Mesozoic sediments that have been variably mineralized by the porphyry system. Tertiary dikes and volcanics cut the porphyry mineralization, and some of these later intrusive bodies appear to be associated with later, structurally controlled silver mineralization.
Basin and range faults cut portions of the system. One of the more prominent structures is the northerly striking Liberty Fault, which dips to the west at ~40° and truncates the porphyry system to the West, bringing mineralized basement rock up against basin-fill alluvium and colluvium. Uplift and weathering of the Cu-Mo porphyry system resulted in the development of a near-surface and near-horizontal supergene copper blanket.
Mineralization in the hypogene Cu-Mo porphyry is dominated by molybdenite (MoS2) and chalcopyrite (CuFeS2). The dominant copper mineral in the supergene blanket is chalcocite (Cu2S) with minor chalcopyrite.
Mineralisation
Base metal mineralization in the Liberty deposit consists of molybdenite (MoS2), chalcopyrite (CuFeS2), chalcocite (Cu2S), galena (PbS), sphalerite (ZnS), tetrahedrite (Cu8Sb2S7), and pyrite (FeS2). Molybdenite occurs mainly in 0.1" to 1.2"-wide quartz veins and veinlets in amounts that range from 0.1% to more than 40% by volume, typically as a selvage on vein walls. Molybdenite is also found in wider (+1.2”) quartz veins, but these are much less common in occurrence. Chalcopyrite and pyrite also are common but lesser vein/veinlet constituents. Galena, sphalerite, and lesser tetrahedrite occur with quartz in separate generations of base metal veins and veinlets that were emplaced at the end of each mineralization pulse (Shaver, 1991).
In general, molybdenum-bearing quartz veins and veinlets are more concentrated along the margins of the Hall stock, forming an irregular shell or sleeve of higher grade mineralization around a lower grade core. However, the intensity of quartz veining does not correlate directly with higher grade molybdenum – barren quartz veins are common within the deposit. Disseminated molybdenite is rare, occurring only in a 100'- to 200'- thick portion of the North Hall stock as replacements in biotite and/or plagioclase sites (Shaver, 1991). In addition to quartz, minor gangue minerals present in the veins and veinlets include fluorite, scheelite, tourmaline, gearksutite, and creedite, with siderite, dolomite, and calcite occurring as vug fillings.
The average grade (0.080% Mo) of the quartz monzonite porphyry (Kqmp) is higher than the average grade (0.064% Mo) of the orthoclase-rich intrusive rocks (Kamp). Part of the reason for this may be that the Kamp is more prevalent in the interior portion of the stock, while Kqmp is the dominant rock type along this portion of the stock margins (particularly the west and southwest sides), where quartz-molybdenum veining is more
concentrated.
Although chalcopyrite can occur with molybdenite in minor amounts in veins and veinlets within the main body of molybdenum mineralization in the Hall stock, it is much more prevalent in quartz veins in the metasediments on the northeast and east sides of the stock. Here it occurs in the remnant of the copper-dominant shell that originally surrounded the Hall stock before it was tilted and disrupted by faulting. In addition to chalcopyrite, chalcocite occurs as disseminations and as secondary coatings on pyrite within a roughly horizontal blanket of secondary supergene copper enrichment just below the bottom of oxidation. Definition of this supergene copper blanket is based on a combination of reverse circulation and diamond core drill holes that penetrate this portion of the deposit and on pit bench exposures from mining by Equatorial in 2000 – 2002. The thickness of the supergene blanket ranges from a few feet to 170 ft, and averages approximately 85 ft. Although generally horizontal and laterally continuous, the supergene blanket is locally offset by post-mineral faulting, particularly towards the main body of molybdenum mineralization to west. Copper grades in the supergene zone range from 0.06% Cu to 1.71% Cu, and average around 0.31% Cu. Beneath the supergene blanket, the chalcopyrite content of the sulfide zone is generally very low.