Identification of Two Types of Metallogenic Fluids in the Ultra-Large Huize Pb–Zn Deposit, SW China

Figure 8

Documentation and sampling of Stope 15# in tunnel 1752 m in Kuangshanchang. (1) Oxidized Pb–Zn orebodies; (2) beige dolomites, with veined, porphyritic calcite developments; (3) light grey-to-grey-white medium-grained calcitic dolomite; (4) grey-to-dark-grey fine-grained limestones; (5) calcite. I. First stage ores are mainly coarse-grained pyrites with small quantities of deep brown sphalerites; II. Second stage ores are mainly brown sphalerites with small amounts of galena; III. Third stage ores, rose-colored sphalerite + galena. (a) Morphology of the orebody 0–5 m above head height in Stope 15# of tunnel 1752 m. Yellow-brown and reddish-brown Pb–Zn oxide orebodies were found on either side of the grey-black Pb–Zn sulfide ores, while yellow coarse-grained dolomites lie outside the ores. Several vein-shaped oxide ores were intercalated within the sulfide orebodies. (b) Morphology of the orebody 4 m into Stope 15# of tunnel 1752 m. The joint fractures are more developed in this area, the oxide orebodies formed through leaching, and sulfide orebodies occur in alternating layers. The top part of this wall is composed of ocher-red carbonates that are likely to have been produced during the later stages of hydrothermal metallogenesis. (c) Bottom part of the sulfide orebody 8 m into Stope 15# of tunnel 1752 m. The main mineral in this orebody is coarse-grained pyrite, with sporadic occurrences of deep-red sphalerites. (d) Top part of the sulfide orebody on the left wall, 8 m into Stope #15 of tunnel 1752 m. The main minerals in the orebody are yellow-brown to brown sphalerites, followed by galena. The sphalerites are distributed in porphyritic and vein-like shapes, with lead-grey star-like points of galena tightly associated with the sphalerite. (e) Sulfide orebody on the right wall, 8 m into Stope #15 of tunnel 1752 m, which we deduce to be the top part of the orebody, based on its occurrence. The main minerals found in this orebody are lead-grey-colored galena, followed by yellow-brown-colored sphalerite. The galena displays a porphyritic, vein-like distribution, while the sphalerites display a vein-like, spotted distribution. (f) Morphology of an oxide orebody and its adjacent rocks, 19.5 m into Stope 15# in tunnel 1752 m. (g) Interstratum fracture 46 m into Stope 15# of tunnel 1752 m. The surface of the fracture has a relaxed wave-like shape, and the fracture is 1–10 cm wide, is filled with yellow-brown fault gouge, and displays schistosity. This fracture acts as the boundary between the C₁b and C₁d strata. The hanging wall is composed of C₁b light grey-to-grey white calcitic fine-grained dolomite, while the footwall is composed of C₁d grey-to-dark grey limestone breccia cemented with clay, which appears to be lenticularized. The fracture is a left-lateral reverse shear fracture, with an orientation of NE45°∠40°SE.