Pampa Metals (CSE: PM) (FSE: FIRA) (OTCQX: PMMCF) reported the reception of key radiometric dating and petrographic studies of quartz-veinlet stockwork samples from the Buenavista target at their Block 4 Project, which is located 110 km south of the Escondida mining district in the Cordillera de Domeyko porphyry belt in Northern Chile.
The Tertiary geological age date is an important addition to the attractiveness of the Buenavista Target. The most productive porphyry copper deposits along the Domeyko Cordillera mineral belt all have Tertiary-aged hydrothermal systems. This data point adds to the geological, geochemical, and geophysical information acquired by Pampa Metals, which comprise a compelling case for Buenavista to represent a priority drill target along the Domeyko Cordillera – the most productive copper belt in the world.
Paul Gill, CEO of Pampa Metals stated:
“We are delighted with the latest information from the Buenavista Target. Although no two porphyry systems are exactly the same, the overwhelming evidence to date is that there is a significant system to investigate by drilling at Buenavista, together with several other geophysical anomalies located within the property that appear to have a similar signature.”
Details & Key Findings
• Pampa Metals geologists selected valid samples of the central Buenavista porphyry and quartz-veinlet stockwork zone for radiometric age dating and petrographic studies, which were forwarded to the Chilean National Geological Institution (“Sernageomin”) and to a prominent Chilean petrographer with extensive experience in porphyry systems, respectively.
• A radiometric age date of 60.3 +/- 1.0 Ma (U-Pb; zircon) corresponds to the host rock of the porphyry-type quartz-veinlet stockwork with molybdenum anomalies found at the Buenavista target in Block 4 (see previous news releases dated June 23, May 24, May 3, March 15, 2022, and October 18, 2021).
• This confirms that the Buenavista target is a Tertiary-aged hydrothermal system.
• Petrographic studies of the age-dated rock sample show that it corresponds to a magmatic-phreatomagmatic breccia with dacite porphyry clasts, which is highly leached with a “vuggy silica” texture and evidence of silica, illite-sericite, quartz, alunite, and pyrophyllite hydrothermal alteration assemblages. Relicts of leached pyrite mineralization were also determined.
• At least three types of quartz veinlets were identified: i) saccharoidal quartz with bands of fluid and solid micro-inclusions; ii) gray crustiform quartz with bands of fluid and solid micro-inclusions and with the development of banded dark veins; and iii) low temperature veinlets comprising quartz in rosettes.
• All of these contain pyrite micro-inclusions, with late fractures occupied by goethite after coarse pyrite, and rare native gold flakes.
The Early Tertiary (Paleocene) age date obtained for the host rock porphyry at the Buenavista target in Block 4 would be the first for the Sierra Vaquillas Altas area in northern Chile. This age is equivalent to that of intrusions to the southeast at Cerros Corral de Alambre, and to that of volcanic rocks to the northwest in the western block of the El Profeta and Sierra de Varas faults, both of which have been associated with the magmatism of the widespread Chile-Alemania Formation.
A Paleocene age is considered the maximum age for the porphyry system at the Buenavista target, but may in fact represent the host rock for a younger porphyry event. This is a situation described for other porphyry deposits along the Cordillera de Domeyko porphyry belt, such as El Salvador located 115 km SSW of Block 4, where mineralizing porphyry intrusions from the Middle Eocene are intruded into Lower-Middle Paleocene magmatic rocks.
The petrographic study revealed successive pulses of hydrothermal infill, with at least three generations of porphyry-style quartz veinlets cutting through an initial phreatomagmatic brecciation event. Hydrothermal alteration associations indicate that the system is exposed at a relatively high level between the phyllic and epithermal transition, which is consistent with oxidised relicts of pyrite mineralization in the centre, together with evidence of quartz-sulfide structures with copper-gold-silver-arsenic values observed around the periphery of the Buenavista stockwork zone.
The geologic age date and petrographic study provide strong support for Pampa Metals’ plans for drill testing of the previously undrilled Buenavista target, in addition to previously reported results from geological mapping, ground magnetics surveying, and induced polarisation reconnaissance survey lines. Field collection of more than 2,500 soil samples centered on the Buenavista target has recently been completed, with results pending.
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