Some further thoughts on Sara Alicia. In this post on the...

Some further thoughts on Sara Alicia. In this post on the geochem mag results I raised a few issues which have led me further down the rabbit hole of exploration - lots of data provided by AZS to interpret (geol, geochem, geophysics) if one has the time, inclination, and some knowledge.

INFORMATION ON SKARN TYPE DEPOSITS
My main starting point for this post was the idea that this is recognized as a Skarn Deposit and this 1992 report by Meinert gives a good summary of them.
For those interested I would recommend:
Summary and Intro page 145/6 and
Models and conclusions P158.

Starting at the tectonic scale there are these 4 models.



Type A is possible tectonic setting for Sara Alicia based on the Fe/Au/Co association.  While - this link may be dated now it shows such a subductive setting was possible.
[Aside: between 3:15 to 3:40 (70-50 Mya) they include the Chixulbub meteorite impact thought to have extinctified large dinosaurs - just a small dot at this scale though]

From AZS's description the model for Sara Alicia is probably something like A below (with a different erosion level).  A large intrusive with a dyke that extends out into the country rock and produces a skarn around it that has been intersected by the first 6 drill holes.  Subsequent deeper drilling (A la Promontorio/Alacran) for a porphyry source.....



Meinert p 156/7 gives examples of gold related skarns:


Apart from the sub-horizontal orientation the Fortitude example looks like it may be a variant of Sara Alicia with a dyke extending from the main intrusive. [Porter geo science description of Fortitude Mine - ? same mine as the example].

MAGNETICS AT SARA ALICIA
One thing that may be needed is to put Sara Alicia into a more regional context - 300x300m is not a large block and it is obvious the surrounding ground is going to be of some interest to AZS and others.

The above 2D magnetics has been processed to produce a 3D model (not provided by the company) which AZS hopes will mean even the Sara Alicia block could have a significant deposit.

I would expect a more regional magnetic survey and inversion model could produce an image something like this with a small block representing Sara Alicia for scale.


AZS have done magnetic susceptibility tests on the core from the drill holes which should provide petrophysical information that improves the accuracy of the magnetic inversion model.   Further drilling may also help directly with mineralisation or geo data.


Given the nature of skarn mineralisation mineral identification within related rocks is a specialised field beyond core photos and probably even the average geo without experience/training.
At a real guess a lot of the silvery metallic mineral in this image of polished core is probably magnetite (+-??pyrrhotite) but there must be cobalt and other sulphides present as well to account for up to 7% or so Co.

GEOCHEMISTRY GEOLOGY GENERAL COMMENTS
I was originally wondering about the effect of topography on the geochem. AZS gave some topo information with the drilling and it shows that the weak anomaly west of the drilling is down slope along a drainage and near a haul road.

The main anomaly though goes uphill from the workings and drilling and is open to the south and perhaps South East where the Au/Co geochem doesn't obviously correlate well with magnetics.

The topography and skarn nature of the ore probably answer the question of why the Au/Co geochem anomalies do not extend into the northern part of the tenement.  The magnetic interpretation suggests the magnetic body extends to depth under cover.
Limited drilling to date suggests a shallow dip.




Faulting is mentioned from surface mapping and schematically shown on the above topo map.


Apart from some weak ?weathering on the fractures in the DSA3 sample weathering is not deep judging from the polished core samples above.

No Cu/Ni geochem given....

SUMMARY
I hope the above is of some use as background material for Sara Alicia.  There are almost more questions than answers that come from it but some info to DYOR.

AZS have provided a ?limited selection of the cornucopia of information on Sara Alicia which leads down a rabbit hole of speculation that only drilling will give definitive answers on economics

Certainly an interesting project where the grades of Au and Co are high enough to potentially support even a modest mine within the confines of the existing tenement.

The presence of these ??unusual Au/Co rich skarns could lead to interesting discoveries in the area around Sara Alicia.

GLTAH