On December 5, 2022, Heliostar entered into a share purchase agreement, as amended with Argonaut for the sale of all of the issued and outstanding shares of Aurea Mining Inc., a wholly-owned subsidiary of Argonaut, which through Aurea Mining’s wholly-owned subsidiary Minera Aurea S.A. de C.V., holds a 100% indirect interest in and to Ana Paula.
On March 28, 2023, Heliostar Metals Limited closed its transaction with Argonaut Gold Inc. in which it acquired, indirectly, the Ana Paula Gold Project. Heliostar now holds a 100% interest in the Ana Paula Gold deposit in Mexico.
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Summary:
Mineralization
At least two, and possibly three, mineralizing events are observed at the scale of the property, but the relationships and timing of these events is not currently known.
Mineral Deposition
In general, four gold depositional sites are recognized at Ana Paula (Gibson, 2012):
1. Quartz-sulphide and quartz-carbonate-sulphide veinlets, stockworks with sulphide clots and disseminations in both intrusions and hornfels.
2. Narrow semi-massive sulphide contact replacement of limestone or hornfels/skarn at the intrusion contacts.
3. Sulphide clots, rims and masses in narrow contact breccias hosted in intrusions at or near the sedimentary contacts and/or fault contacts.
4. Mineralization associated with a sulphide constituent within breccia matrix and with sulphide replacement textures within structurally controlled breccia formed oblique to the dominant northerly trending westerly dipping stratigraphy.
Mineralization at Ana Paula occurred during at least two different events or stages. The first event is characterized by gold-arsenic-(bismuth-tellurium), (or Au-As-(Bi-Te)), where mineralization is associated with intermediate intrusions emplaced into limestone. The second event locally cuts the first and is characterized by gold-silver-lead-zinc-mercuryantimony (or “Au-Ag-Pb-Zn-Hg-Sb”), containing locally zoned coarse sphalerite. There are also various quartz-calcite veins with epithermal textures, but the relative timing of these veins remains unclear.
Structures
The boundary between the Teloloapan and Platform terranes underlies the Ana Paula and surrounding mineral concessions. Medina (2010) described the contact zone as characterized by intense deformation and faulting, and placed the boundary on the eastern margin of the Ana Paula Project where it is interpreted as a north-striking leftlateral fault. Detailed structural work to verify this interpretation is currently underway.
Several structural observations may be important (Gibson, 2012).
1. Sedimentary rocks strike north to north-northwest with westerly dips of 45º to 75º.
2. Intrusive contacts are generally parallel to bedding in the sedimentary rocks.
3. Most of the structures observed at the surface in the area of drilling consist of folds in sedimentary rocks that are surrounded by intrusive rock.
4. Apparently minor faults are common at low angles to the bedding, in many cases located along contacts between sedimentary and intrusive rocks.
5. Larger-scale faults are not observed at surface nor have they been intersected in core, other than the faults commonly seen at and parallel to sedimentary-intrusive contacts.
6. Larger northeast and easterly trending structures (breccia, veins) are observed northeast of the main Ana Paula mineralization.
Deposit Types
Numerous gold deposits are located in present or ancient subduction zones of plate boundaries. Gold deposit types associated with convergent plate boundaries include: Au porphyry, sediment hosted, intrusion related, epithermal, and orogenic gold deposits.
Gold deposition at Ana Paula tends to occur, both contemporaneous with and post intrusion, exhibiting at least two mineralizing events. The earliest consists of Au-As-(Bi-Te) disseminated mineralization characterized by progressive mineralization over time through deposition of gold in breccias, stockworks, contact skarn (both endoskarn and exoskarn) and other replacement bodies.
The second mineralization event (Au-Ag-Pb-Zn-Hg-Sb) perhaps related to the epithermal style of alteration may be a later hydrothermal phase of the earliest intrusive event or may be younger.
The exact timing of gold deposition and the mechanism of deposition within the GGB and at Ana Paula are not yet fully understood and appears to vary among the known deposits, where each deposit shares important characteristics and differences. Intrusions at Ana Paula have been dated at 66.0 – 66.7 Ma ± 0.7-1.8 Ma (Valencia et al, 2008), which may also date the earliest onset on mineralization.
Results from Ana Paula suggest that the bulk of the gold deposition occurs with the dominant Au- As-(Bi-Te) mineralization, and is largely hosted in a northerly trending and westerly dipping corridor of intrusive rocks, at the contacts with sedimentary rocks and hornfels, and within important breccia bodies. Gold deposition within the highgrade core of the deposit is structurally controlled, located at the intersection of at least two fault structures and the host stratigraphy. Both skarn type massive and disseminated sulphide (arsenopyrite + pyrite) replacements and some epithermal overprinting have occurred but the extent and relationship to the oldest intrusive rocks have not been studied in detail.