The Christa occurrence, discovered in 1988, is located three kilometres east of the summit of Coquihalla Mountain near the headwaters of Jim Kelly Creek.
The Coquihalla Mountain area is underlain by intermediate to felsic flows and pyroclastic rocks assigned to the Late Oligocene to Early Miocene Coquihalla Formation, which unconformably overlie intrusive rocks of the Late Jurassic and Early Cretaceous Eagle Plutonic Complex.
The Christa occurrence consists of several small outcrops of quartz breccia hosting quartz veins and veinlets within a brecciated phase of the Eagle Plutonic Complex, which is here characterized by either muscovite granite or gneissic granodiorite. These rocks are overlain by younger tuff of the Coquihalla Formation less than 50 metres to the north. The main quartz breccia zone outcrops in a cliff, 3 to 7 metres in height, approximately 100 metres in length and oriented at 024 degrees with a dip of 25 degrees. Other scattered outcrops of quartz breccia have been identified to the southwest and northeast, along strike, over a total length of 335 metres.
The poorly sorted breccia comprises angular to subrounded, clear to milky quartz fragments, up to 30 centimetres in diameter, in a siliceous matrix. It hosts no visible sulphides, but limonite alteration, varying from one to five per cent of the total rock, has resulted in widespread pervasive orange staining. Local, less than five-millimetre wide grey quartz veins, cut both the fragments and the matrix, and are themselves cut by late milky quartz veins. Traces of electrum were tentatively identified in thin section.
There is very little difference mineralogically between the fragments and the matrix, both of which are made up of 70 to 80 percent quartz and 15 to 25 per cent sericite. This suggests that both were derived from the same material. Late quartz veins, and most probably pyrite, appear to have been introduced after brecciation occurred.
The breccia is believed to have been the product of various stages of a multi-phase process of diffuse silicification and sericitization, stockwork quartz veining, fragmentation, late quartz veining and further brecciation. The original protolith has not been determined.
In 1988, samples from an outcrop of quartz breccia are reported to have yielded up to 3.315 grams per tonne gold and 35.9 grams per tonne silver (Von Einsiedel (2012-05-30): Review of Technical Information and Proposed Exploration Program for the Christa-Aura Property).
In 1989, sixty three, 1.5-metre wide continuous chip samples across the largest quartz breccia outcrop averaged 0.514 grams per tonne gold and 5.4 grams per tonne silver, including a 13.5-metre interval which graded 1.034 grams per tonne gold and 9.6 grams per tonne silver (Assessment Report 20488).
In 2011, rock chip samples yielded values of up to 1.925 grams per tonne gold and 19.7 grams per tonne silver over 2.5 metres (Sample Area BB; Von Einsiedel (2012-05-30): Review of Technical Information and Proposed Exploration Program for the Christa-Aura Property).
Work History
During 1988 through 1990, Noranda completed programs of geological mapping, soil and rock sampling and geophysical surveys on the area.
In 2011, Longacre Resources Inc. completed a program of soil and rock sampling and an induced polarization survey on the area. The induced polarization survey indicated a distinctive chargeability response associated with the known area of mineralization and partially defined a much larger response below the exposed mineralized zone that exhibits the same chargeability response as the observed mineralization. The geophysical anomaly identified at depth is reported to appear to be much larger than the response associated with the observed mineralization and is open along strike to the northeast.
In 2018, Project One Resources Ltd. completed a program of airborne magnetic and radiometric surveys on the area as the Aura property.
