OTCPK:NGELF - Post by User
Comment by
realtyon Jan 05, 2019 11:37am
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Post# 29189940
RE:RE:Geology at Cortez - Similar to Hole 5
RE:RE:Geology at Cortez - Similar to Hole 5Breccia Associations Gold-bearing iron-sulfide minerals are concentrated within the matrix of monolithic and polylithic brecciated rocks along clast boundaries (Fig. 28A); however, it is also common to observe strongly mineralized clasts surrounded by a less mineralized matrix (Fig. 28B-D). For example, the clasts in Figure 28A are not mineralized; instead, the bright reflective Au-bearing iron-sulfide minerals are distributed along the clast boundary. In contrast, Figure 28B shows a clast that is opaque owing to pervasive Aubearing iron-sulfide mineralization and is more strongly mineralized than the surrounding matrix. Similarly, Figure 28C shows a cubic clast that is strongly mineralized by bright reflective Au-bearing iron-sulfide minerals and a less mineralized matrix. Figure 28D shows the extent of mineralization of the same clast under transmitted light. Above the clast, at the boundary between it and the next clast (within the drawn oval), there is a concentration of opaque carbonaceous material, illite, and fine-grained Au-bearing ironsulfide minerals. The Au mineralization is concentrated within the clast as well as at the clast boundary with the unmineralized clast (Fig. 28C-D). Because these samples were collected from drill core within heavily brecciated rocks, they may be mega-clasts within the breccia that contain smaller clasts and matrix. Two samples contain clasts that are strongly Au mineralized with a halo of disseminated Au-bearing iron-sulfide minerals within the matrix surrounding the clasts, shown as the opaque material in Figure 29A. These strongly mineralized clasts are black in hand sample (Fig. 29D, circled) and thin section (Fig. 29E, circled), making some breccia samples appear to be polylithic. It is not possible to determine the composition of the original clasts due to the extent of mineralization (Fig. 29B). An LA-ICP-MS transect through the clast and surrounding mineralized halo and matrix indicates significant Au within the clast as well as in the matrix (Fig. 29C). The Au-bearing ironsulfide minerals are concentrated within the clast; however, the matrix has sporadic Aubearing iron-sulfide mineralization. The trace element chemistry in the clast and matrix is similar (Fig. 29C).