Chargeability anomalies in general reflect more conductive areas within rock formations and these chargeability anomalies in particular interpreted to reflect buried sulfide (potentially gold and copper bearing) mineralization typical of porphyry-type mineralization.
The 3-D IP survey ties in with the previous 2-D IP survey completed in 2016 over the main California zone and confirms that the previously mapped and sampled porphyry corridor (view geological map here) extends at least 5 km long and up to 2 km wide from the California zone southwest through the Jasper, Estrella, Purisima East and Purisima West targets.
Each of the 6 porphyry prospects along the corridor exhibit strong porphyry alteration and gold (copper) mineralization (view geochemical map here) within and adjacent to outcropping quartz-feldspar porphyry intrusions and diatreme breccias. The Jacobo target not covered by this 3-D IP survey appears to add an additional 2 km of length to the porphyry corridor to the southwest.
The 3-D survey encompassed 23.1 line km to cover the Purisima West, Purisima East and Estrella targets as well as an additional 4.5 line km of 2-D IP to tie into the 2-D IP survey conducted in 2016 (view 2016 IP chargeability map here). The benefit of 3-D IP surveys is to provide better definition of the size and shape of conductive or resistive bodies at depth.
Joey Wilkins, CEO and President commented “Our geological mapping and geochemical sampling delineated five mineralized porphyry targets southwest of the main California target. This new 3-D IP data gave us more than we had hoped for in defining several strong and large chargeability anomalies that coincide with our geological and geochemical targets. None of the Jacobo, Purisima West, Purisima East and Estrella targets have ever been drill-tested.”
The Purisima West target returned a strong geophysical response with IP chargeability anomalies starting at 25m depth and expanding in both size and strength down to 500m depth. The chargeability anomalies near surface coincide with gold soil anomalies related to outcropping magnetite-bearing gossans and extensive phyllic-argillic alteration in a felsic diatreme breccia. Low resistivities associated with high chargeabilities are thought to represent clay alteration with disseminated sulphides. Mixtures of high resistivity and high chargeability are interpreted to represent mineralized silicified zones. The airborne radiometric survey Total Count response at Purisima West is very strong, interpreted to be related to phyllic-argillic alteration. Molybdenum soil anomalies confirm the gold-copper porphyry target with highs up to 308 ppm Mo over an area measuring 500m by 600m.
Impressive chargeability anomalies were also detected under the outcropping diatreme breccias at Purisima East, coincident with gold soil anomalies. A +600m wide, horseshoe-shaped chargeability high surrounds the La Purisima Glory Hole mine where high-grade gold samples in rock returned up to 44.6 gpt in a 1.0m channel sample. Other chip samples running 0.62 to 5.94 gpt gold in the same area. The open cut, two declines and underground workings followed oxidized sedimentary breccias down to about 25m depth searching for visible gold. The resistivity response is complex, more conductive near surface around the La Purisima Glory Hole mine, more resistive from 75m to 250m, then conductive again from 300m to 500m depth. High resistivity is interpreted as silicified zones with vuggy silica as seen in high sulfidation systems and locally within the Purisima mine. Purisima East is capped by phyllic and argillic alteration, with indications of advanced argillic alteration (dickite) in samples from the Glory Hole. The target has very strong radiometric Total Count anomaly, supported by the presence of phyllic-argillic alteration.
The Estrella target contains multiple chargeability anomalies primarily in the northern half of the target from 25m to 150m depth and in the southern half at deeper depths. The northwest chargeability anomaly expands and migrates southeast to a sizeable deeper anomaly and most importantly, under post-mineral volcanic rocks. The chargeability anomaly measures 1.2km by 0.8 km with higher IP responses interpreted to represent disseminated sulfides. The 2-D data also show a clear resistivity change between the overlaying volcanics and underlaying basement rock with the development of a sizeable and circular chargeability IP anomaly with a central low. This anomaly is surrounded by anomalous gold-copper rock chip samples in basement rocks and has strong northwest-southeast trending magnetic highs interpreted as intrusions and/or magnetite/pyrrhotite bearing hornfels, which makes it a compelling buried porphyry target. The north end of Estrella has lower chargeability anomalies coincident with highly anomalous copper-gold rock chip samples and outcropping quartz feldspar porphyries surrounded by basement sediments containing stratified gossans.
QP Disclosure – The IP-Resistivity geophysical survey was conducted by SJ Geophysics Ltd in 2019, followed by extensive computer modelling and interpretation of the data to better understand the nature of the anomalies. The dataset includes Volterra 3-dimensional resistivity and chargeability models, depth slices of the 3-D data from 25m to 500m depths, as well as Volterra 2-dimensional inversions or pseudo-sections on the lines linking to the 2016 2-D IP survey. Joey Wilkins, P.G. and CEO/President of Aztec Minerals Corp. is the qualified person (QP) who reviewed the technical date herein and approved this news release.
About Aztec Minerals – Aztec is a mineral exploration company focused on the discovery of large mineral deposits in the Americas. Our core asset is the prospective Cervantes porphyry gold-copper property in Sonora, Mexico. The historic, district-scale Tombstone property hosts both bulk tonnage epithermal gold-silver as well as CRD massive sulfide silver-lead-zinc-copper mineralization in Cochise County, Arizona. Aztec’s shares trade on the TSX-V stock exchange (symbol AZT) and on the OTCQB (symbol AZZTF).
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