Encouraging Exploration Results At La Curva West Prospect
VANCOUVER - Mirasol Resources Ltd has received option payment confirming that OceanaGold Corporation (OGC) will continue into the 2nd year of the La Curva Joint Venture (JV), Santa Cruz Argentina. OGC has met the first-year minimum JV commitments and drilling 3,020 m at the Castora Trend.
Mirasol's President and CEO, Stephen Nano said, "We are pleased to continue working with the team at OceanaGold. Mirasol and OGC are currently designing an aggressive 2nd season drill program for La Curva project, which is anticipated to start in the 4th quarter of 2018. The program will provide a first pass drill test of exciting new targets at Curva West and a second phase of drilling on the Castora Trend focused at the SouthWest and Cerro Chato prospects."
Last season's drilling was concentrated on the Castora Trend where 3020 m of diamond core was drilled in 19 holes, including a follow-up deep stratgraphic drill hole to test for the presence of permissive hosts rocks a depth at the Cerro Chatto prospect. Drilling for last seasons exploration is interpreted to have intersected the upper portion of a Au dominated epithermal system with both lower-grade, broader zones of disseminated style Au+Ag mineralization and narrow, high-grade epithermal veinlets. Assays Results include, from the SouthWest prospect, 106.2 m at 0.61 g/t Au and 2.7 g/t Ag, from a dome margin breccia and up to 1.80 m at 6.88 g/t Au and 84.9 g/t Ag from banded epithermal veining.
In addition, Surface exploration from last season confirmed the presence of a prospective geological environment for epithermal Au+Ag mineralization at the undrilled Curva West and the Castora Trend SouthWest prospects. Hydrothermal alteration was shown to be associated with Jurassic-age rhyolite to dacite flow domes and dyke emplacement and is interpreted to be contemporaneous with development of a large syn-volcanic horst and graben structural setting. This geological setting is the outcome of regional scale crustal extension, that produces large scale normal faulting, a permissive structural environment that can foster significant vein development when associated with active epithermal systems as seen at the Curva project.
Geological mapping at Curva West has outlined epiclastic sedimentary breccia units hosting angular clasts (up to 5 m in diameter) of sinter, silicified volcanics crosscut by epithermal veining and individual clasts of Au+Ag bearing epithermal veins. The angular mineralized clasts cluster in specific sites along the fault-bounded margin and over the "roof" of a pre-volcanic Permo-Triassic age horst block, suggest minimal alluvial transport of the clasts and proximity to source.
Rock chip sampling of mineralized clasts at Curva West returned geochemically anomalous to high grades of Au+Ag with a best sample of 20.73 g/t Au and 18.0 g/t Ag. The mineralized clasts cluster in five target areas, often with distinctive vein textures and Au/Ag ratios, suggesting the presence of several distinct, potentially covered sources of Au+Ag mineralization.
PXRF geochemical grid soil sampling of the epiclastics over Curva West prospect delineated areas of coincident epithermal pathfinder (As+Sb+Hg ± base metals) anomalies in the soils often at sites coincident with clusters of Au+Ag bearing clasts. Handheld infrared spectrometer (IRSpec) alteration studies of the soils also showed the epiclastic matrix to be hydrothermally altered to an argillic mineral assemblage (kaolinite – dickite) characteristic of the upper levels of a classic epithermal alteration system.
The superposition of near-source Au+Ag mineralized vein clasts in an epiclastic sediment, where the sedimentary matrix has been hydrothermally altered, suggests erosion of the upper mineralized interval of an epithermal system, contemporaneous with the burial of the late stages of the active hydrothermal system, causing alteration of the epiclastic matrix. Similar geological settings have been documented for significant Jurassic age Au-Ag deposits elsewhere; including the Marianas-San Marcos vein system1 in Santa Cruz province, that hosts approximately 70 % of Au+Ag resources of the estimated 6.7 Moz Au equivalent reserves and resources in the Cerro Negro district, and the world-class Fruta del Norte Au+Ag deposit in Ecuador. The analogies in geological setting between Curva West / SouthWest and significant gold systems elsewhere, lends support for the drill testing of targets at the Curva Project.
3D models of ground magnetics and IP electrical geophysics were generated from a combination of existing Mirasol data and new surveys completed this season under the OGC JV. The models show features that support the horst and graben geological setting for Curva West and the SouthWest prospects, and have been integrated with other datasets to select and prioritize drill targets for this season's program.