Reduced CO2 fluid as an agent of ore-forming processes: a case study of dolomite-replacement skarns at the Yoko-Dovyren massif)

The paper presents newly obtained geochemical data on outer-contact rocks and carbonatereplacement skarns of the Yoko-Dovyren layered ultramafic-mafic intrusion in the northern Baikal area. The rocks initially contained CO2-rich fluid with a high oxygen fugacity (up to NNO + 3–4), which was generated by the partial decomposition of dolomite and by reactions between SiO2 and carbonates. The skarn blue diopside is enriched in Pt (up to 0.2 ppm) and V (300 ppm), and the wollastonite zone of the skarns contains elevated Re concentrations (up to 0.4 ppm). The REE pattern of the contact-zone quartzite is identical to the REE patterns of phlogopite-bearing lherzolites from the lower contact part of the Yoko-Dovyren massif. These geochemical features of the rocks of the intrusion may be explained by the transfer and redeposition of material by reduced H2O-CO2 fluid. According to thermodynamic calculations, a reaction between H2O-CO2 fluid and high-Mg olivine at a subsolidus temperature of T = 950оC and pressure P = 2 kbar should result in a decrease in the oxygen fugacity to QFM – 2 and, hence, generate much CO. According to the calculations, a low oxygen fugacity (close to QFM + 0.7) can also be maintained by pyrrhotite oxidation with H2O and CO2 fluid components under cumulus P-T parameters. As a result of these reactions, the fluid should enrich in Pt extracted from magmatic sulfides, and this Pt can be redeposited in rocks, including those composing the skarn zones.

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Whole-rock and zircon evidence for evolution of the Late Jurassic high Sr/Y Zhoujiapuzi granite, Liaodong Peninsula, North China Craton

10.5194/se-2021-129 ◽

2021 ◽

Author(s):

Renyu Zeng ◽

Mark Allen ◽

Xiancheng Mao ◽

Jianqing Lai ◽

Jie Yan ◽

...

Keyword(s):

Oxygen Fugacity ◽

North China Craton ◽

Late Jurassic ◽

North China ◽

Early Stage ◽

Middle Part ◽

Source Rocks ◽

Geochemical Data ◽

Low Oxygen ◽

Liaodong Peninsula

Abstract. Middle-Late Jurassic high Sr/Y granitic intrusions are extensively exposed in the Liaodong Peninsula, in the eastern part of the North China Craton (NCC). However, the genesis of the high Sr/Y signature in these intrusions has not been studied in detail. In this study, we report results of zircon U-Pb dating, Hf isotopic analysis and zircon and whole-rock geochemical data for the Late Jurassic Zhoujiapuzi granite in the middle part of the Liaodong Peninsula. The Zhoujiapuzi granite is high-K (calc-alkaline) and peraluminous in nature, with high SiO2 (68.1–73.0 wt %) and Al2O3 (14.5–16.8 wt %), low in TFe2O3 (1.10–2.49 wt %) and MgO (0.10–0.44 wt %), and with high Sr/Y (19.9–102.0) and LaN/YbN (14.59–80.40). Morphological and chemical studies on zircon grains show that there are two stages of zircon growth, interpreted as magmatic evolution in two distinct stages. The early stage of zircons (ESZ) reflects a crystallization environment of low oxygen fugacity and high TZr-Ti (Ti-in-zircon thermometer values: 669–792 °C); the late stage of zircons (LSZ) formed with high oxygen fugacity and lower TZr-Ti (498–720 °C). LA-ICP-MS U-Pb zircon dating yielded the formation ages of the ESZ and LSZ of ~162 ± 1 Ma and ~158 ± 1 Ma, respectively, with similar εHf(t) values in the range of &minus26.3– −22.8. Interpretation of the elemental and isotopic data suggests that the Zhoujiapuzi granite was a I-type granite derived from partial melting of basement in the region: ~2.17 Ga Liaoji granites. The high Sr/Y signature is most likely inherited from these source rocks. Based on the geochemical features and regional geological data, we propose that the Liaodong Peninsula in the Late Jurassic was part of a mature continental arc, with extensive melting of thick crust above the Paleo-Pacific subduction zone.

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Experimental study of concentration dependence of Ta2O5 and Nb2O5 solubility in the alkaline and carbonate solutions at T=550oC, P=500 bar and low oxygen fugacity (Co-CoO buffer)

Vestnik Otdelenia nauk o Zemle RAN ◽

10.2205/2011nz000185 ◽

2011 ◽

Vol 3 (Special Issue) ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

N. P. Kotova

Keyword(s):

Experimental Study ◽

Oxygen Fugacity ◽

Concentration Dependence ◽

Low Oxygen ◽

Carbonate Solutions

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Lithospheric mantle refertilization by DMM-derived melts beneath the Cameroon Volcanic Line—a case study of the Befang xenolith suite (Oku Volcanic Group, Cameroon)

Contributions to Mineralogy and Petrology ◽

10.1007/s00410-021-01796-3 ◽

2021 ◽

Vol 176 (5) ◽

Author(s):

Sylvin S. T. Tedonkenfack ◽

Jacek Puziewicz ◽

Sonja Aulbach ◽

Theodoros Ntaflos ◽

Mary-Alix Kaczmarek ◽

...

Keyword(s):

Lithospheric Mantle ◽

Size Variation ◽

African Plate ◽

Cameroon Volcanic Line ◽

Origin And Evolution ◽

Volcanic Group ◽

Cenozoic Volcanism ◽

Composition Of Minerals ◽

Ree Patterns

AbstractThe origin and evolution of subcontinental lithospheric mantle (SCLM) are important issues of Earth’s chemical and physical evolution. Here, we report detailed textural and chemical analyses on a mantle xenolith suite from Befang (Oku Volcanic Group, Cameroon Volcanic Line), which represents a major tectono-magmatic structure of the African plate. The samples are sourced from spinel-facies mantle and are dominated by lherzolites. Their texture is cataclastic to porphyroclastic, and foliation defined by grain-size variation and alignment of spinel occurs in part of peridotites. Spinel is interstitial and has amoeboidal shape. Clinopyroxene REE patterns are similar to those of Depleted MORB Mantle (DMM) except LREEs, which vary from depleted to enriched. The A-type olivine fabric occurs in the subset of one harzburgite and 7 lherzolites studied by EBSD. Orthopyroxene shows deformation consistent with olivine. The fabric of LREE-enriched clinopyroxene is equivalent to those of orthopyroxene and olivine, whereas spinel and LREE-depleted clinopyroxene are oriented independently of host rock fabric. The textural, chemical and thermobarometric constraints indicate that the Befang mantle section was refertilised by MORB-like melt at pressures of 1.0–1.4 GPa and temperatures slightly above 1200–1275 °C. The olivine-orthopyroxene framework and LREE-enriched clinopyroxene preserve the protolith fabric. In contrast, the LREE-depleted clinopyroxene, showing discordant deformation relative to the olivine-orthopyroxene protolith framework, and amoeboidal spinel crystallized from the infiltrating melt. The major element and REEs composition of minerals forming the Befang peridotites indicate subsequent reequilibration at temperatures 930–1000 °C. This was followed by the formation of websterite veins in the lithospheric mantle, which can be linked to Cenozoic volcanism in the Cameroon Volcanic Line that also brought the xenoliths to the surface. This study therefore supports the origin of fertile SCLM via refertilization rather than by extraction of small melt fractions, and further emphasizes the involvement of depleted melts in this process.

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Application of the principal component analysis on geochemical data: a case study in the basement complex of Southern Ilesa area, Nigeria

Arabian Journal of Geosciences ◽

10.1007/s12517-010-0175-5 ◽

2010 ◽

Vol 4 (1-2) ◽

pp. 239-247 ◽

Cited By ~ 2

Author(s):

Emmanuel A. Ariyibi ◽

Samuel L. Folami ◽

Bankole D. Ako ◽

Taye R. Ajayi ◽

Adebowale O. Adelusi

Keyword(s):

Principal Component Analysis ◽

Principal Component ◽

Component Analysis ◽

Geochemical Data ◽

Basement Complex

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Protein Import into Hydrogenosomes of Trichomonas vaginalis Involves both N-Terminal and Internal Targeting Signals: a Case Study of Thioredoxin Reductases

Eukaryotic Cell ◽

10.1128/ec.00206-08 ◽

2008 ◽

Vol 7 (10) ◽

pp. 1750-1757 ◽

Cited By ~ 35

Author(s):

Marek Mentel ◽

Verena Zimorski ◽

Patrick Haferkamp ◽

William Martin ◽

Katrin Henze

Keyword(s):

Trichomonas Vaginalis ◽

Protein Import ◽

Atp Synthesis ◽

Antioxidant Systems ◽

Low Oxygen ◽

Oxygen Sensitive ◽

Targeting Signal ◽

Targeting Signals ◽

Thioredoxin Reductases

ABSTRACT The parabasalian flagellate Trichomonas vaginalis harbors mitochondrion-related and H2-producing organelles of anaerobic ATP synthesis, called hydrogenosomes, which harbor oxygen-sensitive enzymes essential to its pyruvate metabolism. In the human urogenital tract, however, T. vaginalis is regularly exposed to low oxygen concentrations and therefore must possess antioxidant systems protecting the organellar environment against the detrimental effects of molecular oxygen and reactive oxygen species. We have identified two closely related hydrogenosomal thioredoxin reductases (TrxRs), the hitherto-missing component of a thioredoxin-linked hydrogenosomal antioxidant system. One of the two hydrogenosomal TrxR isoforms, TrxRh1, carried an N-terminal extension resembling known hydrogenosomal targeting signals. Expression of hemagglutinin-tagged TrxRh1 in transfected T. vaginalis cells revealed that its N-terminal extension was necessary to import the protein into the organelles. The second hydrogenosomal TrxR isoform, TrxRh2, had no N-terminal targeting signal but was nonetheless efficiently targeted to hydrogenosomes. N-terminal presequences from hydrogenosomal proteins with known processing sites, i.e., the alpha subunit of succinyl coenzyme A synthetase (SCSα) and pyruvate:ferredoxin oxidoreductase A, were investigated for their ability to direct mature TrxRh1 to hydrogenosomes. Neither presequence directed TrxRh1 to hydrogenosomes, indicating that neither extension is, by itself, sufficient for hydrogenosomal targeting. Moreover, SCSα lacking its N-terminal extension was efficiently imported into hydrogenosomes, indicating that this extension is not required for import of this major hydrogenosomal protein. The finding that some hydrogenosomal enzymes require N-terminal signals for import but that in others the N-terminal extension is not necessary for targeting indicates the presence of additional targeting signals within the mature subunits of several hydrogenosome-localized proteins.

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Comparison of Magma Oxygen Fugacity and Zircon Hf Isotopes between Xianglushan Tungsten-Bearing Granite and Late Yanshanian Granites in Jiangxi Province, South China

Minerals ◽

10.3390/min10020106 ◽

2020 ◽

Vol 10 (2) ◽

pp. 106

Author(s):

Xing-Yuan Li ◽

Jing-Ru Zhang ◽

Chun-Kit Lai

Keyword(s):

Oxygen Fugacity ◽

South China ◽

Granitic Magma ◽

Geochemical Data ◽

Jiangxi Province ◽

Magmatic Zircon ◽

Late Mesozoic ◽

Icp Ms ◽

T Values ◽

Southern Jiangxi Province

Jiangxi Province (South China) is one of the world’s top tungsten (W) mineral provinces. In this paper, we present a new LA-ICP-MS zircon U-Pb age and Hf isotope data on the W ore-related Xianglushan granite in northern Jiangxi Province. The magmatic zircon grains (with high Th/U values) yielded an early Cretaceous weighted mean U-Pb age of 125 ± 1 Ma (MSWD = 2.5, 2σ). Zircon εHf(t) values of the Xianglushan granite are higher (−6.9 to −4.1, avg. −5.4 ± 0.7) than those of the W ore-related Xihuanshan granite in southern Jiangxi Province (−14.9 to −11.2, avg. −12.5 ± 0.9), implying different sources between the W ore-forming magmas in the northern and southern Jiangxi Province. Compiling published zircon geochemical data, the oxygen fugacity (fO2) of the late Yanshanian granitic magmas in Jiangxi Province (the Xianglushan, Ehu, Dahutang, and Xihuashan plutons) were calculated by different interpolation methods. As opposed to the W ore-barren Ehu granitic magma, the low fO2 of the Xianglushan granitic magma may have caused W enrichment and mineralization, whilst high fO2 may have led to the coexistence of Cu and W mineralization in the Dahutang pluton. Additionally, our study suggests that the absence of late Mesozoic Cu-Mo mineralization in the Zhejiang, Jiangxi, and Anhui Provinces (Zhe-Gan-Wan region) was probably related to low fO2 magmatism in the Cretaceous.

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An Examination of Transformation Techniques to Investigate and Interpret Multivariate Geochemical Data Analysis: Tellus Case Study

Quantitative Geology and Geostatistics - geoENV VII – Geostatistics for Environmental Applications ◽

10.1007/978-90-481-2322-3_21 ◽

2010 ◽

pp. 231-242 ◽

Cited By ~ 1

Author(s):

Jennifer McKinley ◽

Oy Leuangthong

Keyword(s):

Data Analysis ◽

Geochemical Data ◽

Transformation Techniques ◽

Geochemical Data Analysis

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Multi-Parametric Imaging of Etruscan Chamber Tombs: Grotte Di Castro Case Study (Italy)

Applied Sciences ◽

10.3390/app11177875 ◽

2021 ◽

Vol 11 (17) ◽

pp. 7875

Author(s):

Vincenzo Sapia ◽

Valerio Materni ◽

Federico Florindo ◽

Marco Marchetti ◽

Andrea Gasparini ◽

...

Keyword(s):

Geophysical Methods ◽

Geochemical Data ◽

Distribution Data ◽

Resistivity Tomography ◽

Resistivity Method ◽

Method Integration ◽

Radar Measurements ◽

Soil Measurements ◽

Ground Penetrating

A multi-parametric approach that involves the use of different geophysical methods coupled with geochemical data allowed us to identify undiscovered archeological burials in a funerary area of the Grotte di Castro Etruscan settlement. In particular, we tested the suitability of the capacitive resistivity method and the presence of Radon in soil for the identification of burials calibrating their outcomes over coincident survey profiles with standard geophysical techniques routinely applied for archaeological prospections. Soil Radon data were acquired both in a grid and along a profile to highlight anomalous gas concentrations, whereas electrical resistivity and ground-penetrating radar measurements were conducted on overlapping profiles to depict the electrical and electromagnetic subsurface distribution. Data integration showed a series of anomalies, suggesting the presence of multiple burials starting from a depth of approximately 1.5 m below the terrain surface. Slight anomalies of Radon in the soil were found to correspond to most of the recovered geophysical ones. Our results pointed out the effectiveness of geophysical method integration in archeological prospecting with the novelty of the joint use of Radon in soil measurements and capacitive resistivity tomography. The latter provided reliable results and can be considered as a standalone technique in archaeological surveys.

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Problems of iron gain and loss during experimentation on natural rocks: the experimental crystallization of five lunar basalts at low pressures

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1977.0120 ◽

1977 ◽

Vol 286 (1336) ◽

pp. 313-330 ◽

Cited By ~ 7

Keyword(s):

Oxygen Fugacity ◽

Glass Tube ◽

Oxide Content ◽

Low Oxygen ◽

Lunar Basalts ◽

Purity Iron ◽

High Purity Iron ◽

Low Pressures ◽

Melting Experiments ◽

Iron Bearing

It is extremely difficult to conduct melting experiments on iron-bearing silicate compositions under conditions where the oxygen fugacity and iron oxide content of the charges are controlled precisely at the relevant values, due to reactions between the charge, the container and the adjacent atmosphere. Possible effects are illustrated by discussion of the experimental data for five lunar basalts. At low oxygen fugacities the techniques using molybdenum capsules in an atmosphere whose oxygen fugacity is controlled by passage of a CO 2 /H 2 mixture, and that of enclosing (better, sealing) the charge inside a high purity iron capsule inside a sealed, evacuated silica glass tube yield results which are relatively close to the desired run conditions.

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