Applications of the spectral induced polarization (SIP) method to mineral exploration are limited by our knowledge of the relationships among rock texture, mineral composition, and electrical properties. Laboratory SIP responses were measured on rock samples from the Canadian Malartic gold deposit. Field SIP responses were also measured at the outcrop scale, along a profile that intersects a well-studied mineralized zone. The mineralogy and the texture of sedimentary rocks from this deposit were quantitatively determined with mineral liberation analysis. A systematic decrease (Pearson r = -0.75) in total chargeability with increasing fraction of the sulfide mineral interfaces associated with feldspar minerals (namely, K-feldspar and albite) was observed. On the other hand, total chargeability increased with the fraction of sulfide mineral interfaces associated with carbonates and micas (Pearson r = 0.89). At Canadian Malartic, proximal alteration in the mineralized zones is marked by rocks that lack a foliation plane and that were subjected to pervasive K-feldspar, albite, and pyrite alteration. In contrast, distal alteration in sedimentary rocks is marked by biotite, albite, carbonate, and pyrite that are oriented along the regional S-2 foliation. In the least-altered (LA) sedimentary rocks, quartz and biotite are associated with pyrrhotite and ilmenite as the main sulfide and oxide mineral phases, respectively. SIP measurements conducted at district and outcrop scales and along a drill core indicated that proximally altered sedimentary rocks were characterized by low total chargeability values (0.27 +/- 0.01 to 0.42 +/- 0.02 in the laboratory and 0.21 +/- 0.04 in the field). In contrast, the LA sedimentary rocks were characterized by total chargeability values up to 0.72 +/- 0.07 in the laboratory and 0.38 +/- 0.06 in the field. We conclude that mineralized zones associated with this type of ore deposit are characterized by low chargeability anomalies.

The Proterozoic Vazante zinc silicate district in Minas Gerais, Brazil, hosts world-class hypogene willemite deposits in dolomitic rocks interbedded with siliciclastic rocks deposited in subtidal to supratidal environments. Willemite ore bodies are structurally controlled along regional NE-trending structures which are interpreted as being active during the Neoproterozoic Brasiliano orogeny. The hydrothermal alteration is characterized by an early stage of Fe-dolomite, which replaced the host dolomitic rocks, followed by precipitation of minor sphalerite and then hematite and willemite. Elements commonly enriched in the zinc ore include As, Ba, Be, Bi, Cd, Co, Fe, Ge, In, Mo, Ni, Sb, Se, U, V and W. Mineralogical, fluid inclusion and isotopic data indicates that mixing of S-poor metalliferous saline fluids with meteoric water favored the formation of willemite ore. Carbonaceous phyllites from the underlying thick siliciclastic sequence show evidence of early enrichment in zinc (and ore-related metals) and remobilization, respectively, prior to and during the Brasiliano orogenic event. This unit is interpreted as a possible source of ore-related elements. It is proposed that during the Brasiliano orogeny, hot (T > 170 °C) saline fluids (>15 wt % eq. NaCl) leached metals from siliciclastic source rocks and precipitated willemite ore in the overlying dolomitic sequence along structures that favored mixing with oxidizing meteoric water.

The metal-rich Vazante-Paracatu Mineral Belt, in central Brazil, hosts the Zn-Pb sulfide Morro Agudo District in the Mesoproterozoic (1.3–1.1 Ga) upper carbonate sequence of the Vazante Group. The Morro Agudo district is comprised of the Morro Agudo deposit and the Bento Carmelo, Sucuri, and Morro do Capão occurrences. This carbonate sequence also hosts the Fagundes, Ambrósia and Bonsucesso Zn-Pb sulfide deposits (northern part) and the zinc silicate Vazante and North Extension deposits (southern part). The structurally controlled, stratabound and stratiform styles of mineralization in the Morro Agudo orebodies have been variably classified as sedimentary exhalative, Irish-type and Mississippi Valley-type. In this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) spot analyses of sphalerite and galena from the Morro Agudo district revealed that red sphalerite (interpreted as the last stage) has higher Fe and Mn and lower Bi, Co, Cu, Ge, Hg, Tl compared to the other types of sphalerite, whereas the first generation of galena (Gn-I) is enriched in Ag, Cd, and Se and depleted in Cu and Mn relative to later galena (Gn-II). Mineral paragenesis and principal component analysis (PCA) of ore mineral composition suggest that the Morro Agudo, Sucuri and Morro do Capão mineralized zones formed by similar processes involving Zn-Pb mineralizing fluids with various compositions, comprising two main elemental associations: (1) Fe, As, In, Mn, Sb, Ag; and (2) Cd, Bi, Co, Ga, and Se. Bento Carmelo is distinguished in PCA by its unique dolomite-hosted sphalerite composition with elevated concentrations of Cu, Ge, Hg and likely formed from distinct fluids or processes. Temperatures of the mineralizing fluids for the Morro Agudo district range from 82 to 320 °C, calculated based on the trace element composition of sphalerite. The styles of mineralization and ore compositions are consistent with MVT deposits; however, fluid temperatures are hotter than typical MVT mineralizing fluids and may reflect a higher geothermal gradient or active advective fluid flow during the Brasiliano orogeny.

The Big Bulk Cu–Au porphyry system is located at the southern end of the Stewart–Iskut mineral district in the Stikine volcanic arc terrane, which hosts numerous Late Triassic to Early Jurassic porphyry Cu–Au and epithermal Au deposits, including the Kerr–Sulphurets–Mitchell (KSM) system. Although Big Bulk and KSM have historically been variably classified as alkaline or calc-alkaline systems within a syn-subduction setting, recent studies have proposed post-subduction, back-arc, or stalled-subduction emplacement associated with localized pull-apart basin development. Here, new lithogeochemical data from the Big Bulk stock are integrated with published data from the Sulphurets intrusions at KSM to constrain petrogenesis and assess commonly used magmatic-fertility criteria. Emplaced during the early stages of Hazelton arc volcanism, the Big Bulk stock is gabbroic to dioritic, subalkaline, and calc-alkaline to transitional in affinity, with enrichment in large-ion lithophile elements (LILE), pronounced negative Nb-Ta-Ti anomalies, and relatively low Nb/Yb and Ta/Yb ratios. Integrated with regional paleogeographic reconstructions, geochronological constraints, and comparison with contemporaneous Hazelton arc volcanic rocks, these characteristics favor emplacement in a proximal rear-arc to incipient back-arc setting that remained strongly influenced by active subduction and are less consistent with a mature back-arc or strongly enriched post-subduction setting. The Sulphurets intrusions are generally more evolved, predominantly dioritic and high-K calc-alkaline, and show greater enrichment in LILE and high-field-strength elements. Both mineralized suites show contrasting distributions on commonly cited porphyry Cu ± Au fertility diagrams (e.g., unprospective using La/Yb- and V/Sc-based criteria), but exhibit elevated Al₂O₃/TiO₂ values comparable to those of globally Cu ± Au-productive intrusions, although the Big Bulk stock extends to lower SiO₂ contents. These discrepancies may partly reflect differences in magma evolution within island-arc systems and highlight the limitations of applying fertility indicators developed largely from more evolved continental-arc suites to contrasting tectonomagmatic settings. Accordingly, the lithogeochemical characteristics shared by the mineralized Big Bulk and Sulphurets intrusions, including their elevated Al₂O₃/TiO₂ values, may provide a useful guide for exploration of similar systems within the Stikine terrane.