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  • Mineralogical Society of America  (6)
  • Chemistry/Pharmacy  (6)
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  • Mineralogical Society of America  (6)
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  • Chemistry/Pharmacy  (6)
RVK
  • 1
    Online Resource
    Online Resource
    Effects of arsenic on the distribution and mode of occurrence of gold during fluid-pyrite interaction: A case study of pyrite from the Qiucun gold deposit, China
    Mineralogical Society of America ; 2022
    In:  American Mineralogist Vol. 107, No. 5 ( 2022-05-1), p. 914-929
    Details
    In: American Mineralogist, Mineralogical Society of America, Vol. 107, No. 5 ( 2022-05-1), p. 914-929
    Abstract: This paper presents the results of an investigation of the incorporation of Au within pyritic ore from the Qiucun epithermal Au deposit, China. The new data provide insights into the mode of occurrence of Au during fluid-rock interactions within epithermal systems. The distribution and mode of occurrence of Au within arsenian pyrite were investigated using a chemical and structural characterization-based approach combining laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) trace element analysis, megapixel synchrotron X-ray fluorescence analysis (MSXRF), and atom probe tomography (APT). The resulting data indicate that invisible Au is present at elevated concentrations in the form of a homogeneous solid solution within As-rich pyrite domains, which yields Au concentrations that positively correlate with As. Arsenic-induced lattice defects, such as stacking faults and the expansion of the pyrite unit cell, provide evidence of the effect of As on the incorporation of Au into pyrite. The nucleation and crystallization of electrum preferentially occurred at the fluid-pyrite reaction interface or along fractures and grain boundaries within the pre-existing pyrite. This study indicates that changes in physicochemical conditions (e.g., temperature, pH, and sulfur fugacity) during fluid-pyrite interactions are key controls on the development of nanometer- or micrometer-scale clusters of gold. The systematic compositional and textural observations documented in this study provide new insights into the mechanisms responsible for the different modes of occurrence of Au (ionic vs. particulate) and enable us to further understand the processes involved in the formation of Au mineralization.
    Type of Medium: Online Resource
    ISSN: 0003-004X , 1945-3027
    URL: Article
    DOI: 10.2138/am-2021-7675
    RVK:
    VA 1700
    Language: English
    Publisher: Mineralogical Society of America
    Publication Date: 2022
    detail.hit.zdb_id: 3514-2
    detail.hit.zdb_id: 2045960-9
    SSG: 13
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    The effect of elemental diffusion on the application of olivine-composition-based magmatic thermometry, oxybarometry, and hygrometry: A case study of olivine phenocrysts from the Jiagedaqi basalts, northeast China
    Mineralogical Society of America ; 2023
    In:  American Mineralogist Vol. 108, No. 8 ( 2023-08-1), p. 1449-1460
    Details
    In: American Mineralogist, Mineralogical Society of America, Vol. 108, No. 8 ( 2023-08-1), p. 1449-1460
    Abstract: Olivine compositions are widely used to constrain magmatic thermodynamic conditions such as magmatic temperature, oxygen fugacity, and H2O content. However, elemental diffusion may change the initial compositions and lead to large uncertainty on the estimation of these thermodynamic conditions. In this study, we conducted LA-ICP-MS elemental mapping and EPMA analysis of olivine phenocrysts and olivine-hosted spinel from the Jiagedaqi (JGD) alkaline basalts in northeast China to evaluate the influence of elemental diffusion on olivine-composition-based geothermometry, oxybarometry, and hygrometry. The JGD olivines show normal Fo [Mg/(Mg + Fe) × 100 in moles] zoning, with cores having Fo of 77–87 and rims having Fo of 67–73. The constant P contents from core to rim indicate that these compositional zonings were caused mainly by diffusion. Because Al is a slow-diffusing element and its content is relatively constant from core to rim, the temperature calculated by the Al-in-olivine thermometer is not influenced by elemental diffusion and preserves the JGD olivine crystallization temperature up to 1150 °C. The temperatures calculated using the Sc/Y-in-olivine thermometer, the oxygen fugacity calculated using the olivine–spinel oxybarometer, and the H2O content calculated on the basis of Ca partitioning between olivine and melt are strongly influenced by the diffusion of Fo, Sc/Y, and Ca. However, the compositional plateaus in olivine cores, which were not influenced by elemental diffusion, preserve the magmatic temperature (1150 °C), oxygen fugacity (QFM+1.4), and H2O content (4 wt%) that applied during the formation of the JGD olivines. Together, these findings suggest that the mantle source of the JGD basalts was metasomatized by fluids released from the subducted slab. This study highlights that elemental diffusion in olivine phenocrysts can strongly affect the application of olivine-composition-based geothermometers, oxybarometers, and hygrometers. However, primitive olivine cores that have not been influenced by diffusion preserve the initial magmatic thermodynamic conditions.
    Type of Medium: Online Resource
    ISSN: 0003-004X , 1945-3027
    URL: Article
    DOI: 10.2138/am-2022-8567
    RVK:
    VA 1700
    Language: English
    Publisher: Mineralogical Society of America
    Publication Date: 2023
    detail.hit.zdb_id: 3514-2
    detail.hit.zdb_id: 2045960-9
    SSG: 13
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Crystal chemistry of arsenian pyrites: A Raman spectroscopic study
    Mineralogical Society of America ; 2022
    In:  American Mineralogist Vol. 107, No. 2 ( 2022-02-1), p. 274-281
    Details
    In: American Mineralogist, Mineralogical Society of America, Vol. 107, No. 2 ( 2022-02-1), p. 274-281
    Abstract: A Raman spectroscopic study on the nature of As-S substitution in natural arsenian pyrite [Fe(S,As)2] is presented, covering a compositional range of 0.01–4.6 at% As. Three Raman-active modes were identified in the Raman spectrum of a nearly pure pyrite: Eg (344 cm−1), Ag (379 cm−1), and Tg(3) (432 cm−1). The Raman vibrational modes exhibit one-mode behavior, and the wavenumbers of optical modes vary approximately linearly with As content, correlating with the change in bond constants with increasing substitution of As for S. The linewidth of the Ag mode increases with increasing As substitution, which may be attributed to the increase in lattice strain associated with the substitution of As for S. This study provides experimental evidence for As-induced structural evolution of pyrite from being stable to metastable before decomposing into other phases. Our results, together with those of another Raman study of arsenian pyrite whose As substitution is more complex, indicate that one cannot use Raman band shifts to determine As content, but for a given As content, can characterize the nature of As substitution, i.e., As for S or As for Fe or both.
    Type of Medium: Online Resource
    ISSN: 0003-004X , 1945-3027
    URL: Article
    DOI: 10.2138/am-2021-7806
    RVK:
    VA 1700
    Language: English
    Publisher: Mineralogical Society of America
    Publication Date: 2022
    detail.hit.zdb_id: 3514-2
    detail.hit.zdb_id: 2045960-9
    SSG: 13
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Formation pathway of norsethite dominated by solution chemistry under ambient conditions
    Mineralogical Society of America ; 2021
    In:  American Mineralogist Vol. 106, No. 8 ( 2021-08-1), p. 1306-1318
    Details
    In: American Mineralogist, Mineralogical Society of America, Vol. 106, No. 8 ( 2021-08-1), p. 1306-1318
    Abstract: Recently dolomite analogs, including norsethite, kutnahorite, and PbMg(CO3)2, etc., have attracted much attention due to their dolomite-like crystallographic structure and the resulting potential in solving “dolomite problem.” Previous studies indicate that mechanisms that underlie the formation of norsethite exhibit some similarities to pathways of dolomite crystallization. However, the crystallization behavior of norsethite is still poorly understood, and the physicochemical factors regulating the process are not yet fully established. Herein, to determine the relationships between solution chemistry and formation pathway of norsethite, a series of experiments for the synthesis of norsethite from the solutions with different concentrations of Mg2+ and Ba2+ by a CO2 gas-diffusion method was carried out under ambient conditions. The morphology and phase composition of the products were investigated by a range of techniques, including XRD, FESEM, micro-Raman, and FTIR techniques. ICP-AES was used to monitor the evolution of the concentrations of Mg2+ and Ba2+ in the mineralization solutions. Our observations suggest that the formation pathway of norsethite strongly depends on Mg/Ba ratio in solution, and pure norsethite can directly crystallize from the solutions with Mg/Ba ratio ranging in 20–40. This is the first time to report the direct precipitation of dolomite analogs at ambient temperatures. It suggests that direct precipitation is a feasible pathway for cation ordering structure formation under ambient conditions.
    Type of Medium: Online Resource
    ISSN: 0003-004X , 1945-3027
    URL: Article
    DOI: 10.2138/am-2021-7348
    RVK:
    VA 1700
    Language: English
    Publisher: Mineralogical Society of America
    Publication Date: 2021
    detail.hit.zdb_id: 3514-2
    detail.hit.zdb_id: 2045960-9
    SSG: 13
    Location Call Number Limitation Availability
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Oxygen-fugacity evolution of magmatic Ni-Cu sulfide deposits in East Kunlun: Insights from Cr-spinel composition
    Mineralogical Society of America ; 2022
    In:  American Mineralogist Vol. 107, No. 10 ( 2022-10-3), p. 1968-1981
    Details
    In: American Mineralogist, Mineralogical Society of America, Vol. 107, No. 10 ( 2022-10-3), p. 1968-1981
    Abstract: In this study, we use Cr-spinel as an efficient indicator to evaluate the oxygen fugacity evolution of the Xiarihamu Ni-Cu deposit and the Shitoukengde non-mineralized intrusion. Oxygen fugacity is calculated using an olivine-spinel oxybarometer, with spinel Fe3+/ΣFe ratios determined by a secondary standard calibration method using an electron microprobe. Cr-spinel Fe3+/ΣFe ratios of the Xiarihamu Ni-Cu deposit vary from 0.32 ± 0.09 to 0.12 ± 0.01, corresponding to magma fO2 values ranging from ΔQFM+2.2 ± 1.0 to ΔQFM-0.6 ± 0.2. By contrast, those of the Shitoukengde mafic-ultramafic intrusion increase from 0.07 ± 0.02 to 0.23 ± 0.04, corresponding to magma fO2 varying from ΔQFM-1.3 ± 0.3 to ΔQFM+1.0 ± 0.5. A positive correlation between fO2 and Cr-spinel Fe3+/ΣFe ratios suggests that the Cr-spinel Fe3+/ΣFe ratios can be used as an indicator for magma fO2. The high fO2 (QFM+2.2) of the harzburgite in the Xiarihamu Ni-Cu deposit suggests that the most primitive magma was characterized by relatively oxidized conditions, and then became reduced during magmatic evolution, causing S saturation and sulfide segregation to form the Xiarihamu Ni-Cu deposit. The evolution trend of the magma fO2 can be reasonably explained by metasomatism in mantle source by subduction-related fluid and addition of external reduced sulfur from country gneisses (1.08–1.14 wt% S) during crustal processes. Conversely, the primitive magma of the Shitoukengde intrusion was reduced and gradually became oxidized (from QFM-1.3 to QFM+1.0) during crystallization. Fractional crystallization of large amounts of Cr-spinel can reasonably explain the increasing magma fO2 during magmatic evolution, which would hamper sulfide precipitation in the Shitoukengde intrusion. We propose that the temporal evolution of oxygen fugacity of the mantle-derived magma can be used as one of the indicators for evaluating metallogenic potential of Ni-Cu sulfide deposits and the reduction processes from mantle source to shallow crust play an important role in the genesis of magmatic Ni-Cu sulfide deposits.
    Type of Medium: Online Resource
    ISSN: 0003-004X , 1945-3027
    URL: Article
    DOI: 10.2138/am-2022-8050
    RVK:
    VA 1700
    Language: English
    Publisher: Mineralogical Society of America
    Publication Date: 2022
    detail.hit.zdb_id: 3514-2
    detail.hit.zdb_id: 2045960-9
    SSG: 13
    Location Call Number Limitation Availability
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    Online Resource
  • 6
    Online Resource
    Online Resource
    Enrichment of precious metals associated with chalcopyrite inclusions in sphalerite and pyrite
    Mineralogical Society of America ; 2024
    In:  American Mineralogist Vol. 109, No. 1 ( 2024-01-2), p. 150-156
    Details
    In: American Mineralogist, Mineralogical Society of America, Vol. 109, No. 1 ( 2024-01-2), p. 150-156
    Abstract: The results of investigations into enrichment of precious metals in sphalerite and pyrite from the Maluntou epithermal gold deposit, China, are reported. The obtained data suggest intimate associations of Au- and Ag-bearing nanoparticles with chalcopyrite inclusions in sphalerite and pyrite. The origins of chalcopyrite inclusions involved different hydrothermal processes, including recrystallization-driven phase separation from parent chalcopyrite-sphalerite solid solutions and replacement of pre-existing pyrite in the presence of Cu-bearing fluids. The chalcopyrite blebs/lamellae follow sphalerite {111} planes, which define a shared sulfur layer for both chalcopyrite and sphalerite. This study indicates that mixing and boiling during the evolution of ore-forming fluids for the Maluntou deposit are key processes for the abnormal enrichment of precious metals in sphalerite and pyrite. The chalcopyrite micro/nano inclusions enhanced enrichment of precious metals in sphalerite provides new insights into the controls on the enrichment of precious metals in sulfides.
    Type of Medium: Online Resource
    ISSN: 0003-004X , 1945-3027
    URL: Article
    DOI: 10.2138/am-2022-8636
    RVK:
    VA 1700
    Language: English
    Publisher: Mineralogical Society of America
    Publication Date: 2024
    detail.hit.zdb_id: 3514-2
    detail.hit.zdb_id: 2045960-9
    SSG: 13
    Location Call Number Limitation Availability
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    Online Resource
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