Rock alterationsFor anyone interested in this type of info.
When searching for a new mineral deposit, especially one with heavy hydrothermal influences, it`s good if you can identify the following:
- faults
- structural controls of the deposits (perhaps partly controlled the fault structures)
- low-magnetic field readings
- rock intrusions into the host rock
- rock alterations
- positive soil samples
- positive loose rock or channel samples
- outcrops of bedrock at surface (if any)
The geophysical survey will help to identify some of this.
From the NR:
``The airborne survey ...... with the flight pattern designed around known mineral orientations and the Company's interpretations of important
structural controls at La Cigarra...........The high sensitivity aeromagnetic survey should detect
major structures and/or
underlying intrusions potentially associated with silver mineralization on the project. The Program will include radiometrics to aid in the identification and distribution of
alteration and the survey will also provide important geologic detail to help target more deep seated mineralization.``
Hot water from a source (like a hotspring or rain water) can dip down then eventually rise back up when the temperature gets extremely high (boiling). When it dips it can come into contact with (hot) mineralized magma. When it rises back up, and comes into contact with upper level rocks, it can be extremely hot. The boiling hot water then changes the colour of those rocks.
This process is known as alterations. It often provides important clues of where to locate a mineral deposit. The reason it can be so fruitful has to do with what the boiling water does on the way back up and what contents could be in the water. When the boiling water alters the upper level rocks with the heat, it also distributes any mineral content it might have collected from interactions with the magma at depth.
Typically, the altered rocks (the colour) gets stronger it gets closer to the richest parts of the mineral deposits.
The boiling water can go through whatever creases, cracks or faults are available. This is one reason why deposits are often found nearby to major faults. The faults can also provide a good travel lane at surface, as well as providing good mineral traps, and also maybe assist with structural controls.
The La Cigarra property is set up nicely with fault structures (all along the property).
The set up works nicely if the geophysical survey can identify low magnetic readings in the middle of or right next to a major fault line and also provide evidence of the rocks being altered within that area.
In addition, it works even better if the geophyical work can identify intrusives in the area, if not near-surface then at depth.
Intrusives can be very fruitful. They represent rocks that have intruded into the host rock. They can bring minerals with them. The intruded rock and the host rock are usually rocks of different ages. The area where 2 different rock types meet up is called the unconformity. This area can also be a good source for mineralization, as in the case at Red Lake Gold District (Ontario) - Goldcrop`s core area.
A good example of a prominent intrusive is Aurico`s Young-Davidson Mine (Matachewan, Ontario). That deposit is found within a syenite intrusive. I know for sure that the first 3 million gold ounces were found entirely within the intrusive, but perhaps all 5.5 million ounces also. That deposit goes down for 1.5km.
I wouldn`t be surprised if the Santa Barbara mine has intrusives at the 900m depth.
We`ll see what kinda info the geophysical studies La Cigarra provides.