Jack Halloran, MSc
J. Halloran1, J. Hedenquist1, K. Hattori1, O. Hatton2
1Department of Earth and Environmental Science, University of Ottawa, Ottawa, Ontario, Canada
2ATEX Resources, Toronto, Ontario, Canada
The Valeriano porphyry-epithermal deposit is located in the Atacama Region of northern Chile, between the El Indio and Vicuña belts at ~4500 m elevation in the Frontal Cordillera. ATEX Resources Inc. acquired access to the property in 2021, and is presently in the fifth drill campaign to identify the resources. The deposit is associated with Miocene porphyry and biotite-hornblende granodiorite dikes. Valeriano is capped by a north-trending advanced argillic lithocap with epithermal mineralization. At the base of the lithocap, patchy pyrophyllite-alunite alteration formed due to cooling from white mica stability. Drillcore logging indicates that this alteration occurs as a carapace ~800-1200 m above the early porphyry intrusions. The intrusion-hosted porphyry mineralization is overlain by a polymictic magmatic-hydrothermal breccia, ranging from clast- to matrix-supported, with abundant angular fragments of early A- and B-type quartz veins as well as angular porphyry fragments; it is referred to as the Rock-Milled Breccia (RMB). The RMB is locally mineralized, but in the 2024 drilling program intercepted an interval of the RMB in drillhole ATXD26 that returned 122.0 m of 1.11 wt% Cu, 0.49 g/t Au, 2.7 g/t Ag and 348 g/t Mo, with anomalous concentrations of Te and Bi. Initial observations indicate that K-feldspar, biotite and magnetite is overprinted by white mica, chlorite, clay which occurs as halos to lavender quartz veins that cut the potassic alteration, and which is associated with high-grade mineralization. The highest-grade intervals within the ATXD26 RMB are associated with the destruction of magnetite by hematite-dominant alteration. Ongoing petrographic and mineralogical study (shortwave infrared spectroscopy, X-ray diffraction), and stable isotope analysis of S of coexisting sulfate-sulfide pairs for paleotemperature estimates, will characterize the alteration and mineralization of the high-grade interval of the RMB, to assist in targeting similar zones.