The TLP, LME and LMW mines have similar styles of mineralization. Mineralization at LMW is currently defined in 73 veins. The five largest veins, LM7, LM8, LM14, LM17W, and LM25, contain 25% of LMW’s current mineral resources. Sampling in workings along or across these veins indicates that a significant amount of the vein material is mineralized with massive, semi-massive and disseminated galena as well as minor amount of chalcopyrite and sphalerite. Vein widths range from 0.3 m to over 10 m. Other metallic minerals present in much smaller amounts include pyrite, hematite, and very sparse amounts of acanthite.
The veins at TLP mostly dip westward while those at LM dip steeply both east and west. Previous mining and stoping along TLP’s T1 and T2 vein structures indicate that the mineralization plunges shallowly to the north within structural zones extending hundreds of metres to a thousand metres or more along strike. The mineralization occurs as massive accumulations or disseminations in the veins. The galena often occurs as massive tabular lenses comprised of coarsely crystalline aggregates or fine-grained granular “steel galena” bodies, which can be up to 1.0 m thick and over 100 m along vertical and horizontal dimensions.
Most of the silver in the TLP-LM veins is present as microscopic inclusions in the galena. It appears that Ag:Pb ratios are distinctly different between veins of the northern TLP area (North Zone) and the southern TLP and LM area (South Zone). Based upon 15 verification samples collected for a previous Technical Report (Broili et al. 2008), veins in the South Zone appear to have much higher zinc contents and higher Ag:Pb ratios (90 to 130 grams silver for each percent lead) than veins from the North Zone (5 to 15 grams silver for each percent lead), as well as proportionally less gold. This difference could be the result of zonation or reflects differences in the level of exposure.
The veins occur in relatively permeable fault-fissure zones and are extensively oxidized from the surface to depths of about 80 m. Within this zone, the veins show many open spaces with conspicuous box-work lattice textures resulting from the leaching and oxidation of sulphide minerals. Secondary minerals present in varying amounts in this zone include cerussite, malachite and limonite. Beneath this oxide zone, sulphide minerals are mixed with secondary oxide minerals in the vein, with sulphides becoming increasingly abundant with depth until about 150 m, beyond which fresh sulphides are present with little or no oxidation.
Wall rock alteration consists of numerous quartz veinlets accompanied by sericite, chlorite, silicification, and ankerite on fractures. The vein systems appear to have better continuity and increasing mineralization with depth, and many veins exposed in the underground workings are often significantly richer in silver-lead-zinc than the same veins exposed at the surface. This could be due to either leaching from surface outcroppings or—the more likely explanation—to primary mineral zoning.