Minera La Negra, S.A de C.V. owns 100% of the La Negra project and holds all of the titles, rights, benefits, and obligations to the La Negra project.
On January 09, 2023 Excellon Resources Inc. ("Company") has agreed to acquire all of the issued and outstanding shares of Minera La Negra, S.A de C.V., the Mexican company that holds title to La Negra.
On July 20, 2023 the Company unexpectedly received a notice of termination of the previously announced acquisition of the La Negra project from the seller, Dalu S.à r.l., an entity owned by an investment fund managed by Orion Resource Partners.
Excellon Resources Inc. cancelled the acquisition of Minera La Negra S.A. de C.V. from Dalu S.À R.L.
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Summary:
La Negra is classified as a Pb-Zn-Ag + Cu skarn.
Local Geology
The principal geologic unit in the vicinity of La Negra is the La Negra facies of the El Doctor Formation, which strikes N in the area of the mine but is interpreted to broadly follow the NW trend of the Piñón Anticline, the axis of which is a major through going structure. To the west, and potentially hosting NW extensions of the mineralization is the San Joaquín facies of the El Doctor Formation, which forms a N trending band approximately 150 m wide. To the west of this, and outside any zones of known mineralization is the foreslope Socavón facies of the El Doctor Formation.
There are several surface expressions of the intrusive, which are believed to be part of a larger regional batholith (although age dating has shown that the intrusive in the area of Zimapán is both older and deeper than the intrusives in the area of La Negra) and which tend to have a NE orientation. The four phases of skarn formation documented by Morrison have created a complex architecture which juxtaposes different styles of alteration. Thus, in the field, it is possible to see spurrite both within the intrusive and distal to it, and both in association with mineralized zones and away from them. Morrison (1982) observed a zonation pattern with proximal hedenbergite skarn transitioning to wollastonite exoskarn and distal garnet skarn in contact with recrystallized limestone, which contravenes the generally accepted zonation pattern for Pb-Zn skarns. This is possibly due to the aforementioned structural complications. Another important feature is the WNW trending Maravillas dike, which has a more felsic composition and is directly associated with zones of mineralization.
Although several authors (Gaytán Rueda 1975, Fraga 1984) have indicated that the orebodies of La Negra display clear metal zonation, with higher Pb-Zn + Ag at higher elevation giving way to more Curich ores with minor amount of silver at depth, more recent work has led to the conclusion that this zonation is more apparent than real, and is complicated by mineralizing controls, such as bedding, proximity to vertical structures. Some bodies in isolation show clear patterns of zonation, but depositwide trends are not clear.
Structure
The units in the area tend to follow the regional architecture, striking NW with fold axes along the same orientation, and dipping variably (40o-70o) to the SW. The main feature is the Piñón Anticline which strikes NW-SE and extends from the Zimapán district to the SE through the La Negra district and beyond to the NW. There are also minor NE trending structures that dip 40o to the SE but these are not well documented and it is unclear whether these have experienced much movement.
Alteration and Mineralization
Four stages of skarn formation were documented by Morrison (1982). The earliest phase consisted entirely of fine-grained subidioblastic spurrite, Ca5(SiO4)2CO3, an uncommon mineral of the nesosilicate group which entirely replaced the calcareous protolith. Significantly, spurrite is not present in the Zimapán district but is pervasive around La Negra, and points to shallower environment of formation. The second stage consists of a dense, albeit thin, zone of hedenbergite developed due to the diffusion of Ca into the intrusive, while the introduction of silica created a diffuse zone of diopside. The third stage of skarn formation took place under higher ????????O2 conditions leading to the formation of andradite, hematite, and wollastonite. The economic mineralization was formed in the final stage of skarn formation, which in addition to sulfides generated orthoclase, quartz, calcite and datolite, CaBSiO4(OH), another uncommon nesosilicate.
A polished thin section of unmineralized spurrite-wollastonite skarn was analyzed by Randall (1980). The skarn mineralization has completely replaced the original carbonates with subhedral wollastonite 40%, colorless low-Fe diopside 20%, anhedral to subhedral spurrite replacing wollastonite 8%, and euhedral porphyroblastic grossularite 5%.
A more detailed petrographic analysis of a polished thin section of an (unmineralized) wollastonite skarn by Randall (1980) from the Maravillas orebody indicates a prevalence of subhedral to euhedral wollastonite 30%, 30% anhedral quartz filling voids, highly birefringent anhedral to subhedral diopside 20%, grossularite partially replaced by wollastonite and diopside 15%, and 5% amorphous clay.
The principal minerals at La Negra consist of sphalerite (marmatite), galena, and chalcopyrite, with silver present as hessite [Ag2Te] in association with galena, although Le Couteur (2009) also identified argentite [Ag2S] and pyrargyrite [Ag3SbS3] in samples from the Monica zone. Other common, non-mineral sulfides include pyrite, minor pyrrhotite, lloelingite [FeAs2] and arsenopyrite, with Vassallo and Solorio-Munguía also reporting pentlandite, cubanite [CuFe2S3], freibergite [(Ag,Cu,Fe)12(Sb,As)4S13], polybasite [[(Ag,Cu)6(Sb,As)2S7][Ag9CuS4]], lillianite [Pb3-2xAgxBi2+xS6], and native bismuth (as 2µ grains/blebs entrained in galena). Le Couteur also identified needles of boulangerite [Pb5Sb4S11] in photomicrographs from the Luisa zone.
Mineralized Trends
The mineralization at La Negra displays a variety of orientations and dimensions and depends on the interplay between the intrusive and the surrounding limestones, but mantos and sheets appear to be the predominant morphology. The mineralized skarns can be narrow bodies that are less than one-meter wide, broad, lenticular zones of mineralization that are more than 20 m wide or, as in the case of the La Negra orebody, extensive tabular, subvertical orebodies that follow the contact between the intrusive and the limestone. There are also zones of mineralization that are tabular but subhorizontal, and broadly which follow the orientation of the bedding. These zones tend to have disseminated mineralization and lower grades.
Three, broad NW-trending zones of mineralization define the areas with higher grades. These are, from south to north, the so-called Northwest Trend that connects the La Negra orebody to the Alejandra/Blanca/San Onésimo areas and on to Valenciana, the Maravillas Trend that connects Bicentenario to Maravillas and the Cristo Rey trend that currently consists of El Alacrán and Trinidad but is unexplored to the NW. These zones are interpreted to follow the axial plane of the Piñón Anticline, with both intrusives and fluids exploiting these structures.
The (generally) lower-grade zones occur in between the three NW trends and are associated with subhorizontal limestone units in or near the fold nose. These zones include Gaby, Monica, Cobriza, Reyna, San Pedro and Buenaventura. These areas can be amenable to bulk mining methods, primarily room and pillar.