Summary:
All data is sourced from the Geology Report 2014 and has been translated from Spanish with the assistance of AI.
The Skarn deposit at Minera Sabinas is considered a mineral deposit associated with shallow magmatic systems emplaced in carbonate rocks; its formation is related to low-temperature magma fluids in the process of cooling and heat transfer. It is estimated that its formation temperature was over 350° C, characteristic of Zn-Cu skarns.
The general trend of the deposit is N-S, influenced by a granitic intrusive in the form of a dome, with a slight flexure in the southern part where it changes to NE 30° SW, with a dip varying from 30° to 65° to the W.
The polymetallic characteristic of the deposit is manifested in disseminated and massive forms in the ore minerals of Zinc, Copper, Silver, and Lead; these are always associated with ferrous minerals.
To the west of the deposit, a system of structures in the form of thin veins has been detected, consisting of calcite-quartz with dissemination and banding of sulfides (Pb, Ag, Zn) trending NW 35° SE with average dips of 40° to the SE; their formation is closely related to the skarn deposit due to their parallelism in dip.
In general, the mineralogical constitution of the deposit is defined as a broad silicified and skarn (silicated) zone, mainly composed of garnet of the grosularite-andradite variety with disseminated, massive, banded, and erratic mineralization mainly of Zinc-Copper, and some Silver-Lead. The host rock of the mineral body at the lower part is the granitic intrusive (Cerro La Gloria Formation) and at the upper part is the limestone (Cuesta del Cura Formation).
Due to its mineralization characteristics, shape, and dimensions, the deposit has been divided into several zones:
NW Zone
This is the most important zone due to its dimensions, located to the north of the deposit, trending North-South with a dip of 50° to the W. It does not have a regular geometric shape but can be defined as a "mantle" of skarn bent by the intrusive body, with a bifurcation at depth caused by the push of the granitic mass below elevation 540. Its approximate dimensions are 65 m wide, 350 m long, and 30 m thick.
San Fernando Zone
This zone is considered an independent body, located south of the NW Zone and below the East High Zone, trending NW 40° SE with a dip of 35° to the SW. It is defined as a concave parallel skarn mantle fractured by low-angle granitic intrusive dikes that structurally control it above and below. Its dimensions are 60 m wide, 300 m long, and thicknesses ranging from 8 m to 55 m.
This structure lies parallel to the lower part of the main Skarn body at a horizontal distance of 35.0 m, separated by the granitic intrusive. It consists of a broad silicated zone with grosularite and andradite garnets with disseminated, massive, banded, and erratic mineralization associated with the granodioritic intrusive that structurally controls it above and below.
East High Zone
This zone is located in the center of the deposit, bordering the East Zone to the W and the Nose Zone to the South. It trends NE 25° SW with a dip of 40° to the NW, also defined as a slightly concave skarn "mantle." Its dimensions are 35 m wide, 150 m long, and 15 m thick.
East Zone
This zone is located south of the NW Zone, continuing at depth with the East High Zone, trending NE 27° SW with a dip of 25° to the NW. It can also be defined as a skarn "mantle" with a tendency to become vertical at depth (below level 800). Its approximate dimensions are 40 m wide, 425 m long, and 20 m thick, known down to level 1,340. Identified through diamond drilling, we can only infer an erratic and local distribution of Zinc, Silver, and Copper minerals.
Nose Zone
This is the southernmost zone of the deposit, considered a continuation of the East High Zone, trending NE 40° SW with a dip of 65° to the NW. It can be defined as a thin skarn strip controlled by the geological contact of the intrusive in an elongated nose shape, close to 25 m from the projection of the Veta Grande del Bajo at some levels, containing two flanks (NE, SW).
Veta Grande del Bajo
This is the second most important massive sulfide structure at the Sabinas Mine, extending from the lower part of Veta Grande del Alto between levels 99 and 135. Originally developed at level 135 through faces 4520-N and 4520-S, it is now known both through diamond drilling and development down to level 690.
Veta Grande del Alto
Generally accompanied by an extensive silicified zone with disseminated sulfides towards the backs, it appears parallel to Veta Grande del Bajo and the contact of the intrusive at a variable distance of 10 to 90 meters, with dips ranging from 35° to 50° to the SW. At the upper levels of the mine, 99-135 and upwards, the mineralization extends in parts below the vein towards the intrusive. This vein represents the continuity towards the Sabinas Mine of the Ramal Ibarra and San Marcial system developed at the San Martín Mine and, together with the Veta del Bajo, represents great potential towards the NW - SE and lower levels of the Sabinas Mine. This structure is currently identified through diamond drilling down to elevation 840.
Veta San Luis
Mineralization appears disseminated, mainly sphalerite, galena, and chalcopyrite in a quartz-calcite matrix. At the lower levels of the mine, there is a marked increase in Lead, Zinc, and Copper sulfides, developed directly between levels 180 and 420, while diamond drilling has cut it down to level 920.
Cholita 1, Cholita 2, and Cholita 3 Veins
These structures have been identified as the mine has deepened, branching off above Veta Grande del Alto. Their mineralization appears disseminated, mainly sphalerite, galena, and chalcopyrite in a quartz-calcite matrix. They have been developed directly from levels 180 to 500, while diamond drilling has only cut Cholita 1 down to level 600.
The mineralization in the area is primarily Silver, Lead, Zinc, and Copper, found in fill and replacement veins. The veins and replacement bodies are composed of chalcopyrite, sphalerite, bornite, tetrahedrite, native silver, arsenopyrite, pyrrhotite, stibnite, and galena.
Mineralization
The mineralization of the area is based on silver, lead, zinc, and copper; which are found in filling and replacement veins. The veins and replacement bodies are composed of chalcopyrite, sphalerite, bornite, tetrahedrite, native silver, arsenopyrite, pyrrhotite, stibnite, and galena.
Sphalerite tends to deposit later and in larger quantities than Fe, Mo, As, Cu, but is strongly associated with marcasite and chalcopyrite. It is generally deposited after chalcopyrite, pyrite is observed both in early and late stages, very distant from the metamorphic aureole.
At depth, there is an increase of pyrrhotite-marcasite with a horizontal zoning similar to the previous one. Towards the SE end between Nueva mine and Sabinas, there is an increase of Ag, Pb, Zn in the massive skarn bodies.
Arsenic and Fluorite appear early, but are cut by quartz and chalcopyrite veins with potassic feldspar in the intrusive, appearing more abundantly in proximity to the endoskarn.
Bornite and Chalcopyrite occur together in the skarn, and are deposited at a similar time in replacement textures, prior to most other sulfides.
Pyrrhotite occurs near the intrusion at depth in the central part of the deposit, in the early stage of paragenesis.