DynaResource, Inc. operates its 100% owned San Jose de Gracia producing gold mine in México.
DynaResource, Inc. owns 100% of the outstanding shares of DynaResource de México, S.A. de C.V. ("DynaMexico”) which owns 100% of the mining concessions, equipment, camp, and related facilities that comprise the San Jose de Gracia mining project.
- subscription is required.
Summary:
Deposit Type
Exploration by Dyna de Mexico and its predecessors has focused principally on discovery and definition of a low-sulfidation epithermal gold-silver deposit. Mineral deposits of this type are well documented throughout the Sierra Madre Occidental.
Alteration patterns and fluid inclusion data studies show that precious metal precipitation generally occurs between 180 to 240° C, which corresponds to depths of 150 to 450 m below the paleosurface.
Mineralized Zones of the SJG Mine
San Pablo Zone
Control at San Pablo the main quartz vein-breccia currently has a strike length of almost 750 m and a down-dip extension of 500 m. The dip ranges from 10 to 39° towards 290°. This low angle, tabular structure, and the narrower, less continuous structures above and below it, were formed during horizontal-oblique compression resolved at some point in a prevailing transpressive phase. Fracture formation occurs within, above and locally below the unconformable contact between the rhyodacite volcanics and the metasedimentary basement.
The structures are observed at or close to the basement–rhyodacite contact and cut-up through the volcanic sequence towards the east-southeast, giving a sigmoidal form to the quartz vein-breccias. The quartz vein-breccias appear to lack favorable footwall or hanging wall lithologies and may be in contact with the andesite porphyry sills, metasedimentary rocks, rhyodacite and andesite. In its distal regions, the San Pablo structure can have a very low angle dip). Some footwall veinlets in the Gossan Cap can even be horizontal. The sigmoidal quartz vein breccias dilate between near-vertical north-trending controlling faults. Although the San Pablo structure has a 018° strike an 80 m wide high-grade zone, or shoot, that cuts across the mineralized structure has a strike of 065°. This disparity between the orientation of the vein and the strike of the high-grade shoot is caused by the fact that the vein mirrors the dip and dip direction of the basement-volcanics contact, which has a strike of 018°, whereas the hydrothermal fluids are sourced from a more steeply dipping fault down dip that has a 065° strike.
Tres Amigos Zone
In the Tres Amigos Mine, the main quartz vein-breccia with accompanying hanging wall and footwall stockwork currently has a strike length of 365 m and a down dip extension of 210 m. The dip of the quartz vein-breccia at surface is 54° towards 330°, i.e. the strike is 060°. Although this is a steeper dip than the San Pablo structure this vein was also emplaced during an episode of compression. The main quartz vein-breccia dips more steeply here as the unconformable contact between the metasedimentary rocks and the volcanics dips more steeply in this area and it is the unconformity and the bedding planes within the volcanic rocks that act as loci for vein emplacement. The 060° strike for this vein corresponds with the 065° striking high-grade shoot that transects the San Pablo structure.
Further evidence that the vein was formed during a phase of compression is shown by the change in dip from 54 to 27° in its central portion with an accompanying increase in thickness. Veins that become thicker as they become more shallowly dipping are formed during reverse fault movement and reverse fault movement implies compression. Vein extent upand down-dip is controlled by sub-vertical faults that have an average strike of 060°. As the mineralized structures approach the controlling faults they gradually reduce in thickness and eventually terminate at negligible thickness when the fault is contacted. It is theoretically possible, however, for more veins to form on the other sides of the controlling faults, both up-dip and down dip, and this has obvious implications for exploration. The only factor that limits downdip extension, for that is the one that troubles exploration the most, is the position of the current exploration horizon relative to the mineralization palaeohorizon. In other words, the structures may be there, but if they are at an elevation that was too deep for the optimum boiling process required for mineral deposition then they will be un-mineralized.
La Union-Mochomera Zone
The mineralization in La Union-Mochomera dips 10° to 30° towards 305°, and therefore has a similar orientation to the mineralization in the San Pablo structure and would have been formed during the same compressional environment. The structural interpretation of La UnionMochomera, compared with San Pablo, is hampered by its lower density of drilling, however. The La Union-Mochomera mineralization currently has a strike length of 400 m and a down dip extension of 350 m.
The La Union area differs from San Pablo in that the quartz vein-breccias are narrower, (the thickest quartz vein-breccia drill hole intercept being <2 m) and are less easily extrapolated up and down dip or between adjacent sections. In fact, only one section in the La Union area had appreciable inter-drill hole connectivity. Also, in contrast to San Pablo, the veins are mainly emplaced well above the unconformity within andesites, with no veins occurring at the rhyodacite basement contact.
Palos Chinos Zone
Only seven drill holes intercepted this trend, but vein orientation data obtained from underground plans show that the mineralization in this area has a similar trend to a 170° striking strike-slip fault that dips steeply to the west. This strike-slip fault is one of the three sinistral strike-slip faults which progressively displace the volcanic-basement contact progressively southeastwards. The veins underground dip between 41 and 64° to the southwest and were formed during sinistral transgressive movement along the 170° strike-slip fault. The mineralization has not been emplaced within this strike-slip fault however, the fault has acted as a controlling fault for compressive forces that have acted obliquely to it and the mineralization has been emplaced within the moderately dipping open space fractures that have resulted from this compression.
Purisima Zone
As with the Palos Chinos trend, the main controlling features at Purisima are the strike-slip faults that displace the volcanic-basement contact southeastwards. The Purisima trend is bounded by a 133° striking pair of parallel strike-slip faults 320 m apart that acted as the controlling faults on the mineralization which occurs between them. Sinistral transpression about these controlling faults causes the bounded strata to pop open in the vertical sense allowing the eventual, and probably simultaneous, emplacement of the epithermal mineralization.
La Prieta Zone
Underground visits at La Prieta have determined that the worked veins mainly have low angle dips and dip towards the north-northwest. In the majority of cases, the stopes occur entirely within the metasedimentary basement in close proximity to, and just above, the unconformable contact with the rhyodacite units above. The folded metasedimentary rocks dip steeply to the southwest in the stoped areas and at no point are the workings observed to exploit the bedding planes. This proves that, despite there being multiple planes of weakness in the sedimentary rocks to be exploited by vein emplacement, the overriding control on the eventual mineralization event are the low-angle voids formed during transpression. In the Rosario Mine, which connects to the La Prieta workings, veins are present within the rhyodacite unit and dip 36° to the northwest. Very little remnant vein material is visible in the stopes at La Prieta, and therefore the exact nature of the mineralization in this mine is not known. To date, only epithermal veinlets ~5 mm thick have been found in the stope walls but, to date, no quartz vein-breccia. The low-angle of dip shown in the workings implies that the veins were emplaced during a compressive phase.