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The Hongtoushan Cu-Zn volcanogenic massive sulfide (VMS) deposit, located in the Hunbei granite–greenstone terrane of the North China Craton, has undergone a complex, multi-stage metallogenic evolution. The deposit comprises three main types of massive ores: Type-1 ores, characterized by a sulfide matrix enclosing granular quartz and dark mineral aggregates; Type-2 ores, distinguished by large pyrite and pyrrhotite porphyroblasts and a small amount of gangue minerals; and Type-3 ores, mainly distributed in the contact zone between the ore body and gneiss, featuring remobilized chalcopyrite and sphalerite filling the cracks of pyrite. The metallogenic process of the Hongtoushan deposit is divided into three main stages: (1) an early mineralization stage forming Type-1 massive ores; (2) a metamorphic recrystallization stage resulting in Type-2 massive ores with distinct textural features; and (3) a late-stage mineralization event producing Type-3 massive ores enriched in Cu, Zn, and other metals. This study integrates sulfur isotope, trace elements, and fluid inclusion data to constrain the sources of ore-forming materials, fluid evolution and metallogenic processes of the deposit. Sulfur isotope analyses of sulfide samples yield δ 34 S values ranging from −0.7 to 4.2 (mean: 1.8 ± 1.5, 1 σ), suggesting a predominant magmatic sulfur source with possible contributions from Archean seawater. Trace element analyses of pyrite grains from different ore types reveal a depletion of rare earth elements, Cu, and Zn in Type-2 massive ores due to metamorphic recrystallization, and a subsequent re-enrichment of these elements in Type-3 massive ores. Fluid inclusion studies allowed for identifying three types of ore-forming fluids: Type-1 (avg. T h : 222.9; salinity: 6.74 wt.% NaCl eqv.), Type-2 (avg. T h : 185.72; salinity: 16.56 wt.% NaCl eqv.), and Type-3 (avg. T h : 184.81; salinity: 16.22 wt.% NaCl eqv.), representing a complex evolution involving cooling, water–rock interaction and fluid mixing. This multi-disciplinary study reveals the interplay of magmatic, hydrothermal and metamorphic processes in the formation of the Hongtoushan VMS deposit, providing new insights into the fluid evolution and metallogenic mechanisms of similar deposits in ancient granite–greenstone terranes. [ABSTRACT FROM AUTHOR]

The axinite-bearing Gukjeon Pb–Zn deposit is hosted by the limestone, a member of the Jeonggaksan Formation, which, in turn, forms the part of the Jusasan subgroup of the Yucheon Group in the Gyeongsang Basin in the southeastern part of the Korean Peninsula. In this study, we attempted to interpret the spatial and temporal relationships among geologic events, including the mineralization of this deposit. We constructed a new 3D orebody model and suggested a relationship between skarn alteration and related mineralization. Mineralization timing was constrained using SHRIMP zircon age dating results combined with boron geochemistry on coeval intrusive rocks. Skarn alterations are restrictively found in several horizons of the limestone formation. The major skarn minerals are garnet (grossular), pyroxene (hedenbergite), amphibole (actinolite and ferro-actinolite), axinite (tizenite and ferro-axinite), and epidote (clinozoisite and epidote). The three stages of pre-skarn, syn-skarn, and post-skarn alteration are recognized within the deposit. The syn-skarn alteration is characterized by prograde metasomatic pyroxene and garnet, and the retrograde metasomatic amphibole, axinite, and epidote. Major skarn sulfide minerals are sphalerite, chalcopyrite, galena, and pyrite, which were predominantly precipitated during the retrograde stage and formed amphibole and axinite skarns. The skarn orebodies seem to be disc- or flat-shaped with a convex form at the central part of the orebodies. The vertical ascending and horizontal infiltration of boron-rich hydrothermal fluid probably controlled the geometry of the orebodies. Considering the whole-rock major, trace, and boron geochemical and geochronological results, the timing of Pb–Zn mineralization can be tightly constrained between the emplacement of boron-poor intrusion (fine-grained granodiorite, 82.8 Ma) and boron-rich intrusion (porphyritic andesite in Beomdori andesitic rocks, 83.8 Ma) in a back-arc basin setting. The boron for mineralization was sourced from late Cretaceous (Campanian), subduction-related magmatic rocks along the margin of the Pacific plate. [ABSTRACT FROM AUTHOR]

The Busang mineral prospect in Kalimantan, Indonesia, was reported to host a large Au resource until 1997 when it was revealed that drill core samples had been deliberately and systematically contaminated ("salted") with extraneous Au to falsify resource estimates. One month before the fraud was uncovered, Dr. G. Milligan, then professor emeritus of geology, visited the site to collect a suite of core samples for academic study that was deemed representative of the host rocks, alteration, and mineralization of the Busang Southeast Zone. These samples were re-examined here by optical microscopy, electron microprobe (EMPA), whole-rock geochemistry, and fluid inclusion microthermometry to characterize the subsurface geology and hydrothermal mineralization, and to assess reasons why the system is of uneconomic character. The host rocks were variably altered calc-alkaline porphyritic subvolcanic diorites, typical of the lithological units along the mineralized trend in the Kalimantan Gold Belt. Early hydrothermal mineralization with quartz-sulfide (pyrite, chalcopyrite, Cu-sulfosalts) stockwork veinlets associated with pervasive phyllic and propylitic alteration was overprinted by crudely banded quartz-carbonate-sulfide/sulfosalt (pyrite, sphalerite, chalcopyrite, galena, tennantite-tetrahedrite, bournonite-seligmannite) veins. The stockwork veins were associated with up to 140 ppb bulk rock Au, some of which was hosted by Cu-sulfosalts. Microthermometry on quartz-hosted aqueous fluid inclusion assemblages (FIA; n = 13) and single inclusions (non-FIA; n = 20) in quartz-carbonate-sulfide/sulfosalt veins yielded an overall range in homogenization temperatures (Th) between 179 °C and 366 °C and bulk salinities between 1.1 wt.% to 8.6 wt.% NaCl equivalent, with much smaller data ranges for individual FIA (e.g., FIA 3; 239.1 °C to 240.5 °C and 0.5 wt.% to 1.4 wt.% NaCl equivalent). Primary FIA along growth zones in quartz were identified, providing constraints on fluid characteristics at the time of quartz growth. Carbonate-hosted FIA (n = 3) and single inclusions (non-FIA; n = 3) in the same veins yielded Th between 254 °C and 343 °C and bulk salinities of 1.1 wt.% to 11.6 wt.% NaCl equivalent. Likewise, data ranges for individual FIA were much smaller. Many of the geological characteristics of the Busang Southeast Zone were compatible with a telescoped, intermediate-sulfidation epithermal system, having formed from diluted magmatic fluids that precipitated weak base metal mineralization. However, the system was unproductive with respect to Au and Ag, at least within the studied area. Of note, vein textures and fluid inclusion characteristics indicative of boiling or efficient fluid mixing—processes both considered critical for the formation of economic lode gold deposits—were absent in the samples. [ABSTRACT FROM AUTHOR]