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Micrometer- to submicrometer-scale indium-rich domains are preserved within sphalerite included in hornfels-hosted pyrrhotite from the Dulong polymetallic skarn, Yunnan, China. The nano-mineralogy of the ZnS-bearing blebs was investigated using scanning transmission electron microscopy on thinned foils extracted in situ from pyrrhotite. Indium incorporation in sphalerite occurs via the coupled substitution 2Zn2+ ↔ Cu+ + In3+; the results thus allow insights into phase relationships in the system ZnS-CuInS2 in which solubility limits are debated with respect to a cubic to tetragonal phase transition. The highest concentrations of In are measured in basket-weave domains from the smallest ZnS blebs or from un-patterned areas in coarser, irregular ZnS inclusions in pyrrhotite. Indium-rich domains contain 17–49 mol% CuInS2, whereas In-poor sphalerite contains <5 mol% CuInS2. Atomic-scale metal ordering observed in In-(Cu)-rich ZnS domains was modeled as mixed sites in a cubic structure with P4̅3m symmetry and empirical formula [(Cu,In,Zn)3(Zn0.5Fe0.5)]4S4. This sphalerite modification is distinct from the cubic-tetragonal phase transition reported elsewhere for analogous, synthetic phases with abundant planar defects. The Zn1.5Fe0.5CuInS4 nanophase described here potentially represents a Fe-bearing polymorph of Zn2CuInS4, considered as an end-member in the sakuraiite solid-solution series. At ≤50 mol% CuInS2 in the ZnS-CuInS2 system, incorporation of In via coupled In+Cu substitution is promoted within a cubic ZnS phase with lower symmetry than sphalerite rather than into the spatially coexisting chalcopyrite of tetragonal symmetry. Solid-state diffusion accounts for phase re-equilibration resulting in the basket-weave textures typical of In-(Cu)-rich domains in the smallest blebs, whereas fluid percolation assists grain coarsening in the irregular inclusions. The results show evidence for the existence of a more complex phase transition than previously recognized from experimental studies, and, intriguingly, also to a potential eutectic in the system ZnS-CuInS2. Pyrrhotite-bearing hornfels in skarns may concentrate In and other critical metals hosted in sphalerite and related sulfides due to the efficient scavenging from fluid by these minerals and the subsequent preservation of those included phases by sealing within the pyrrhotite matrix. [ABSTRACT FROM AUTHOR]

The article discusses a study on geological characteristics and genesis of Beiya gold-polymetallic deposit in Yunnan Province, China. It mentions that gold deposits are found in contact zone of the Beiya Formation carbonate rocks. It states that hydrothermal ores are composed of magnetite, chalcopyrite and pyrite. It also mentions that ore texture and structure showed that the metallogenic process of Beiya underwent skarnization method.

Abstract: Based on the chemical analysis data, Beiya Gold multi-metal Ore contains Au 2.17 g/t, Ag 59.36 g/t, Fe 38.51%, Cu 0.57%, Pb 2.00%, and Zn 0.48%. Chemical phase analysis shows that 95.72% Au exists as nature gold; 67.22% Fe exists as limonite and hematite, and only 23.65% exists as magnetite; 26.41% Cu exists as malachite and only 12.14% exists as sulfide minerals such as chalcopyrite and covellite; in the same way only 3.98% Pb exists as galena and 26.09% Zn exists as sphalerite. So the Systemic process mineralogy study is very necessary to guarantee separating these valuable elements from the ore reasonably and economically. Based on the process mineralogy research, reasonable technology flowsheet is worked out: the ore is ground to 90% under 0.074 mm, leaching Au firstly, then enriching Fe by low-intensity and high-magnetic separation. The Cu, Ag, Pb and Zn in the ore are unavailable now. [Copyright &y& Elsevier]

Abstract: The origin of zonal mineralization in porphyry copper deposit is important for understanding the mineralization processes. We propose a new, modified “orthomagmatic” genetic model for mineralization zoning in hypogene porphyry copper deposits. This new model is based on the features and formation mechanism of comb microfractures in quartz–chalcopyrite veins within pyrite vein from the Hongshan porphyry copper deposit in Zhongdian County, western Yunnan Province, SW-China. The main evidence for this model is volume expansion related to crystallization of chalcopyrite, magnetite and K-metasomatism in the deposit. Comb microfractures are well developed in quartz–chalcopyrite veins and are present as comb-quartz veinlets consisting of a zone of central longitudinal quartz overprinted by laterally grown quartz combs. Chalcopyrite fragments lie perpendicular to the central quartz veinlet and were dismembered by the quartz combs. The combed microfractures are typical tensional hydrofractures. The formation of the comb microfractures is related to volume expansion that was induced by crystallization of chalcopyrite from a chalcopyrite melt that resulted in the subsequent increase of volumetric pressure in the confined residual silica melt. The formation mechanism of the comb microfractures, including volume expansion induced by crystallization, increases volumetric pressure, hydrofracturing and fluid expulsion, and was the most likely process for zoning of minerals in hypogene porphyry copper deposits. Fabrics in the veins and veinlets are consistent with overpressuring and injection and are common structures that are directly related to volumetric pressure and crystallization of chalcopyrite and magnetite and K-metasomatism in hypogene porphyry copper deposits. The volume expansion ratio of chalcopyrite mineral to melt and that of magnetite mineral to melt are approximately 19vol.% and 20vol.%, respectively. The volume expansion rate of a monomolecular lattice is ⩾8vol.% for orthoclase replacing plagioclase. We suggest that zoning of mineralization in hypogene porphyry copper deposits is mainly related to hydrofracturing, migration and distribution of ore-forming fluids, including (1) the enclosure and formation of a mush core, (2) concentration of ore-forming fluids in the orthoclase shell, (3) K-metasomatism and pressure building, (4) hydrofracturing and migration of ore-forming fluids, and (5) prior crystallization of magnetite and chalcopyrite that will expel residual fluids upwards and outwards due to the change in volumetric pressure. [Copyright &y& Elsevier]

[Display omitted] • Skarn Cu mineralization is important in the Laochang deposit. • Silver, Se, In and Sn mainly occur as solid solution or lattice bound in sulfides (Ccp & Sph). • The δ34S values of sulfides indicate a magmatic source. • Skarn Cu mineralization was formed in a high-temperature, magmatic-hydrothermal fluid. Laochang is one of the main ore deposits in the world-class Gejiu polymetallic Sn district, Southwest China. Skarn Cu ore is an important mineralization type in the Laochang deposit. In this study, in situ trace element compositions of chalcopyrite and sphalerite and S isotope compositions of sulfide minerals (arsenopyrite, chalcopyrite, pyrrhotite and sphalerite) of the skarn Cu ore in the Laochang deposit are investigated. The results show that the studied chalcopyrite is enriched in Zn, Ag, In and Sn, and is depleted in Co, Ni, Ga, Ge, As, Cd, Sb, Bi and Pb. The sphalerite is enriched in Fe, Co, Cu, Ag, Cd, In and Bi and depleted in Ni, Ga, Ge, As, Sn, Sb, Tl and Pb. The high Fe, Cd and Co contents of the sphalerite indicate the simple substitution mechanism Zn2+↔ (Fe2+, Cd2+, Co2+). The S isotope compositions of arsenopyrite, chalcopyrite, pyrrhotite and sphalerite fall into a narrow range of − 2.9‰ to + 1.4‰, indicating a magmatic source of the sulfur. The high Sn contents (6.20 ~ 3339 μg/g) and moderate Cd/Zn ratio (0.009 ~ 0.023) of the chalcopyrite and the high In (271 ~ 723 μg/g) contents and Zn/Cd ratio (120 ~ 172) of the sphalerite imply that the skarn Cu mineralization in the Laochang deposit was influenced by high temperature, magmatic-hydrothermal fluids. [ABSTRACT FROM AUTHOR]

• Two stages of mineralization are identified in the Xiaotongchang deposit. • Syngenetic hydrothermal mineralization occurred at ca. 256 Ma. • Materials of basalt-hosted Cu deposit mainly originated from the Emeishan basalts. • A simple model of basalt-hosted copper deposit is proposed in the ELIP. The Xiaotongchang basalt-hosted copper deposit in Jinping, southern Yunnan Province, SW China, is located in the southern part of the Emeishan large igneous province. Here, we use Rb–Sr, Re–Os and S–Pb–C–O isotope data to constrain the age and genesis of the deposit. Petrological investigations reveal two main stages of mineralization. The early-stage is characterized by disseminated or massive sulfides in an assemblage of pyrite + chalcopyrite + quartz + albite + calcite. Rb-Sr isotopic dating of early-stage chalcopyrite yields an age of 256 ± 9.4 Ma (MSWD = 5.4), which is slightly younger than the eruption age of the Jinping basalts. The δ34S CDT values of the sulfides range from +5.8‰ to +7.7‰, suggesting that the metals of the early-stage copper mineralization originated from the Emeishan basalts and that the ore-forming fluids were contaminated by crustal rocks. These units may indicate that the early-stage orebodies represents syngenetic hydrothermal mineralization related to the eruption of Emeishan flood basalts. The late-stage mineralization is characterized by a pyrite + chalcopyrite + bornite + chalcocite + quartz + calcite assemblage that is developed in veins or breccia. The Re-Os isotopic dating of late-stage chalcopyrite samples reveals that they formed at 240–231 Ma. The Pb isotopic compositions ((206Pb/204Pb) t = 17.521–19.227, (207Pb/204Pb) t = 15.480–15.760, and (208Pb/204Pb) t = 37.778–38.731; t = 235 Ma) show that the late-stage copper orebodies have a heterogeneous source and originated mainly from the crust. The late-stage sulfides have higher δ34S CDT values (+7.9‰ to +10.7‰) than the early-stage sulfides. The narrow range of sulfur isotopic compositions of the sulfides associated with both stages and the Pb isotopic compositions of late-stage chalcopyrite indicate that some of the metals associated with late-stage mineralization originated from the Jinping basalts. The C–O isotopic compositions of calcite samples show that the magmatic hydrothermal fluids in the late stage flowed through and were contaminated by the Maokou limestone. Therefore, we suggest that the late-stage orebodies represent magmatic hydrothermal mineralization associated with the Late Triassic rhyolite porphyry and that the tectono-magmatic hydrothermal fluid remobilized copper from the basalts. The copper deposits formed at favourable interfaces within the basalt stratigraphy or in favorable structural locations. [ABSTRACT FROM AUTHOR]