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Yanjing Chen - One of the best experts on this subject based on the ideXlab platform.

  • ore geology Fluid inclusions and four stage hydrothermal mineralization of the shangfanggou giant mo fe deposit in eastern qinling central china
    Ore Geology Reviews, 2013
    Co-Authors: Yan Yang, Yanjing Chen, Jing Zhang, Cheng Zhang
    Abstract:

    article i nfo The Eastern Qinling, Central China, containing more than 20 Mesozoic porphyry ± skarn systems, is the most important Mo province in the world. The Shangfanggou giant Mo deposit, Luanchuan County, Henan Province, is a porphyry-skarn system hosted in a lithologic association comprising carbonaceous sandstone, shale, carbon- ate and chert within the Neoproterozoic Luanchuan Group. Mo ores are mainly altered porphyry, skarn and hornfels, with minor altered gabbro. The mineralization process includes four stages, potassic alteration of the porphyry and skarnization of dolomite marble in stage 1, stockworks of quartz + molybdenite ± sulfide (stage 2), pyrite + quartz ± sulfides (stage 3), and carbonate ± quartz ± fluorite (stage 4), respectively. Mo mineralization was generally associated with strong silicification and/or phyllic alteration. The Fluid inclusions in minerals include three compositional types, i.e., CO2-bearing (C-type), aqueous (W-type) and daughter mineral-bearing (S-type). Minerals formed in stages 1 to 3 contain all the three types of FIs, but the stage 4 minerals only contain the W-type FIs. Oxides and Cu-phosphate are recognized as daughter minerals in S-type inclusions in minerals of stage 1, whereas the daughter sulfide and reducing gases such as CO, CH4 ,H 2 Sa nd C2H6 can be observed in quartz of stages 2 and 3, suggesting that the ore-forming Fluids were initially oxidizing and then evolved to reducing. Boiling Fluid inclusion assemblages can be observed in minerals formed in stage 2 or earlier, but not in stage 3 or later. Fluid Boiling caused CO2 escape, oxygen fugacity decrease and rapid precip- itation of ore minerals, and was a key factor causing Mo-mineralization at Shangfanggou. Data and interpreta- tions presented in this contribution show that the Fluids forming the Shangfanggou Mo deposit evolved from CO2-rich, high-salinity hypothermal, to CO2-poor, low-salinity epithermal (low-T). The Mo mineralization at theShangfanggoudepositmainlyoccurredatdepthof6.6-7.0 km,deeperthanthemajorityofporphyrysystems in volcanic arcs, which resulted from a CO2-rich magma-Fluid system originating from partial melting of thick- ened lower crust. The Shangfanggou mineral system developed during 158-134 Ma when the Yangtze-North China continental collision began to evolve from compression to extension. Magmatic hydrothermal deposits developed in a continental collision regime are generally formed by CO2-rich, high-salinity Fluids.

  • ore geology and Fluid inclusion geochemistry of the tiemurt pb zn cu deposit altay xinjiang china a case study of orogenic type pb zn systems
    Journal of Asian Earth Sciences, 2012
    Co-Authors: Li Zhang, Yi Zheng, Yanjing Chen
    Abstract:

    Abstract The Tiemurt Pb–Zn–Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of Fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330–390 °C with low salinities of 0.8–11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118–205 °C, and salinities of 1.4–3.4 wt.% NaCl eqv. This indicates that the ore Fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric Fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs homogenize at temperatures ranging from 270 to 330 °C, with two salinity clusters of 1.9–14.5 and 37.4–42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation resulted from Fluid Boiling, CO2-escape and transient oversaturation. The estimated trapping pressures of FIs range from 130 to 380 MPa, suggesting an alternating lithostatic–hydrostatic Fluid-system, controlled by a fault-valve at the depth of ∼13 km. Therefore, the Tiemurt Pb–Zn–Cu deposit is likely an example of orogenic Pb–Zn + Cu systems formed in collision orogeny, rather than a pre-collision VMS or Sedex system developed in Devonian; and a new metallogenic model is proposed to interpret the formation of the Tiemurt Pb–Zn–Cu deposit.

Li Zhang - One of the best experts on this subject based on the ideXlab platform.

  • co2 rich Fluid from metamorphic devolatilization of the triassic orogeny an example from the qiaxia copper deposit in altay nw china
    Geological Journal, 2014
    Co-Authors: Yi Zheng, Li Zhang, Huayong Chen, Dengfeng Li, Chengming Wang, Jing Fang
    Abstract:

    The Qiaxia Cu deposit occurs as veins controlled by NW-extending structures in the Devonian volcano-sedimentary Kelan Basin of the Altay orogenic belt, Xinjiang, China. Igneous and sedimentary strata exposed in the mining area have been subjected to greenschist-facies metamorphism represented by an assemblage of chlorite–epidote–biotite ± garnet ± amphibole. The hydrothermal ore-forming process can be divided into the early, middle and late stages, represented by banded magnetite-quartz, Cu-polymetallic-quartz veins and carbonate-quartz ± pyrite veinlets, respectively. The main ore minerals including chalcopyrite and other polymetallic sulphides are revealed to have mainly formed in the middle stage. Four types of Fluid inclusions (FIs), including aqueous (W-type), carbonic-aqueous (C-type), purely carbonic (PC-type) and daughter mineral-bearing (S-type), have been identified at the Qiaxia copper deposit. The early-stage quartz captures the C- and W-type primary FIs completely homogenized at temperatures of 335–388 °C with low salinities of 5.51–8.66 wt.% NaCl equiv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 122–239 °C, and salinities of 0.18–7.86 wt.% NaCl equiv. This indicates that the metallogenic system evolved from CO2-rich, metamorphic to CO2-poor, with the addition of late meteoric Fluid, and that a significant CO2-escape may have occurred during the evolution. The coexistence of all four types of FIs can only be observed in the middle-stage minerals, even in the microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs are homogenized at temperatures ranging mainly from 288 to 329 °C, with two salinity clusters of 3.39–11.75 wt.% NaCl equiv. and 38.93–46.37 wt.% NaCl equiv., respectively. The unique CO2-rich FIs including C- and PC-types in the middle stage implies the metal precipitation results from Fluid Boiling, CO2-escape and transient oversaturation primarily from metamorphic devolatilization. Hence, the Qiaxia Cu deposit can be taken as an example of an orogenic lode Cu system resulting from metamorphic devolatilization in Triassic continent-continental or intercontinental collision; and a deposit-scale metallogenic model has been proposed to interpret the mechanism of formation of the Qiaxia Cu deposit. Copyright © 2013 John Wiley & Sons, Ltd.

  • ore geology and Fluid inclusion geochemistry of the tiemurt pb zn cu deposit altay xinjiang china a case study of orogenic type pb zn systems
    Journal of Asian Earth Sciences, 2012
    Co-Authors: Li Zhang, Yi Zheng, Yanjing Chen
    Abstract:

    Abstract The Tiemurt Pb–Zn–Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of Fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330–390 °C with low salinities of 0.8–11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118–205 °C, and salinities of 1.4–3.4 wt.% NaCl eqv. This indicates that the ore Fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric Fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs homogenize at temperatures ranging from 270 to 330 °C, with two salinity clusters of 1.9–14.5 and 37.4–42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation resulted from Fluid Boiling, CO2-escape and transient oversaturation. The estimated trapping pressures of FIs range from 130 to 380 MPa, suggesting an alternating lithostatic–hydrostatic Fluid-system, controlled by a fault-valve at the depth of ∼13 km. Therefore, the Tiemurt Pb–Zn–Cu deposit is likely an example of orogenic Pb–Zn + Cu systems formed in collision orogeny, rather than a pre-collision VMS or Sedex system developed in Devonian; and a new metallogenic model is proposed to interpret the formation of the Tiemurt Pb–Zn–Cu deposit.

  • Ore geology and Fluid inclusion geochemistry of the Tiemurt Pb-Zn-Cu deposit, Altay, Xinjiang, China: A case study of orogenic-type Pb-Zn systems
    journal of asian earth sciences, 2012
    Co-Authors: Li Zhang, Yi Zheng, Chen Yanjing
    Abstract:

    The Tiemurt Pb-Zn-Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of Fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330-390 degrees C with low salinities of 0.8-11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118-205 degrees C, and salinities of 1.4-3.4 wt.% NaCl eqv. This indicates that the ore Fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric Fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs homogenize at temperatures ranging from 270 to 330 degrees C, with two salinity clusters of 1.9-14.5 and 37.4-42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation resulted from Fluid Boiling, CO2-escape and transient oversaturation. The estimated trapping pressures of FIs range from 130 to 380 MPa, suggesting an alternating lithostatic-hydrostatic Fluid-system, controlled by a fault-valve at the depth of 13 km. Therefore, the Tiemurt Pb-Zn-Cu deposit is likely an example of orogenic Pb-Zn + Cu systems formed in collision orogeny, rather than a pre-collision VMS or Sedex system developed in Devonian; and a new metallogenic model is proposed to interpret the formation of the Tiemurt Pb-Zn-Cu deposit. (C) 2011 Elsevier Ltd. All rights reserved.Geosciences, MultidisciplinarySCI(E)0ARTICLE,SI69-794

Chen Yanjing - One of the best experts on this subject based on the ideXlab platform.

  • Ore geology and Fluid inclusion geochemistry of the Tiemurt Pb-Zn-Cu deposit, Altay, Xinjiang, China: A case study of orogenic-type Pb-Zn systems
    journal of asian earth sciences, 2012
    Co-Authors: Li Zhang, Yi Zheng, Chen Yanjing
    Abstract:

    The Tiemurt Pb-Zn-Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of Fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330-390 degrees C with low salinities of 0.8-11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118-205 degrees C, and salinities of 1.4-3.4 wt.% NaCl eqv. This indicates that the ore Fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric Fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs homogenize at temperatures ranging from 270 to 330 degrees C, with two salinity clusters of 1.9-14.5 and 37.4-42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation resulted from Fluid Boiling, CO2-escape and transient oversaturation. The estimated trapping pressures of FIs range from 130 to 380 MPa, suggesting an alternating lithostatic-hydrostatic Fluid-system, controlled by a fault-valve at the depth of 13 km. Therefore, the Tiemurt Pb-Zn-Cu deposit is likely an example of orogenic Pb-Zn + Cu systems formed in collision orogeny, rather than a pre-collision VMS or Sedex system developed in Devonian; and a new metallogenic model is proposed to interpret the formation of the Tiemurt Pb-Zn-Cu deposit. (C) 2011 Elsevier Ltd. All rights reserved.Geosciences, MultidisciplinarySCI(E)0ARTICLE,SI69-794

Yi Zheng - One of the best experts on this subject based on the ideXlab platform.

  • co2 rich Fluid from metamorphic devolatilization of the triassic orogeny an example from the qiaxia copper deposit in altay nw china
    Geological Journal, 2014
    Co-Authors: Yi Zheng, Li Zhang, Huayong Chen, Dengfeng Li, Chengming Wang, Jing Fang
    Abstract:

    The Qiaxia Cu deposit occurs as veins controlled by NW-extending structures in the Devonian volcano-sedimentary Kelan Basin of the Altay orogenic belt, Xinjiang, China. Igneous and sedimentary strata exposed in the mining area have been subjected to greenschist-facies metamorphism represented by an assemblage of chlorite–epidote–biotite ± garnet ± amphibole. The hydrothermal ore-forming process can be divided into the early, middle and late stages, represented by banded magnetite-quartz, Cu-polymetallic-quartz veins and carbonate-quartz ± pyrite veinlets, respectively. The main ore minerals including chalcopyrite and other polymetallic sulphides are revealed to have mainly formed in the middle stage. Four types of Fluid inclusions (FIs), including aqueous (W-type), carbonic-aqueous (C-type), purely carbonic (PC-type) and daughter mineral-bearing (S-type), have been identified at the Qiaxia copper deposit. The early-stage quartz captures the C- and W-type primary FIs completely homogenized at temperatures of 335–388 °C with low salinities of 5.51–8.66 wt.% NaCl equiv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 122–239 °C, and salinities of 0.18–7.86 wt.% NaCl equiv. This indicates that the metallogenic system evolved from CO2-rich, metamorphic to CO2-poor, with the addition of late meteoric Fluid, and that a significant CO2-escape may have occurred during the evolution. The coexistence of all four types of FIs can only be observed in the middle-stage minerals, even in the microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs are homogenized at temperatures ranging mainly from 288 to 329 °C, with two salinity clusters of 3.39–11.75 wt.% NaCl equiv. and 38.93–46.37 wt.% NaCl equiv., respectively. The unique CO2-rich FIs including C- and PC-types in the middle stage implies the metal precipitation results from Fluid Boiling, CO2-escape and transient oversaturation primarily from metamorphic devolatilization. Hence, the Qiaxia Cu deposit can be taken as an example of an orogenic lode Cu system resulting from metamorphic devolatilization in Triassic continent-continental or intercontinental collision; and a deposit-scale metallogenic model has been proposed to interpret the mechanism of formation of the Qiaxia Cu deposit. Copyright © 2013 John Wiley & Sons, Ltd.

  • ore geology and Fluid inclusion geochemistry of the tiemurt pb zn cu deposit altay xinjiang china a case study of orogenic type pb zn systems
    Journal of Asian Earth Sciences, 2012
    Co-Authors: Li Zhang, Yi Zheng, Yanjing Chen
    Abstract:

    Abstract The Tiemurt Pb–Zn–Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of Fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330–390 °C with low salinities of 0.8–11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118–205 °C, and salinities of 1.4–3.4 wt.% NaCl eqv. This indicates that the ore Fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric Fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs homogenize at temperatures ranging from 270 to 330 °C, with two salinity clusters of 1.9–14.5 and 37.4–42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation resulted from Fluid Boiling, CO2-escape and transient oversaturation. The estimated trapping pressures of FIs range from 130 to 380 MPa, suggesting an alternating lithostatic–hydrostatic Fluid-system, controlled by a fault-valve at the depth of ∼13 km. Therefore, the Tiemurt Pb–Zn–Cu deposit is likely an example of orogenic Pb–Zn + Cu systems formed in collision orogeny, rather than a pre-collision VMS or Sedex system developed in Devonian; and a new metallogenic model is proposed to interpret the formation of the Tiemurt Pb–Zn–Cu deposit.

  • Ore geology and Fluid inclusion geochemistry of the Tiemurt Pb-Zn-Cu deposit, Altay, Xinjiang, China: A case study of orogenic-type Pb-Zn systems
    journal of asian earth sciences, 2012
    Co-Authors: Li Zhang, Yi Zheng, Chen Yanjing
    Abstract:

    The Tiemurt Pb-Zn-Cu deposit is hosted in a Devonian volcanic-sedimentary basin of the Altay orogenic belt, and is thus interpreted to have formed by sea-floor hydrothermal exhalation in previous studies. Our investigation discovered that the deposit is not stratiform or stratabound, but structure-controlled instead. The hydrothermal ore-forming process can be divided into the early, middle and late stage, represented by pyrite-quartz, polymetallic sulfide-quartz and carbonate-quartz veinlets, respectively. The early-stage veins and contained minerals are structurally deformed and brecciated, suggesting a compressional or transpressional tectonic regime. The middle-stage veinlets intrude and infill the fissures of the early-stage assemblages, and show no deformation, suggesting a tensional shear setting. The late-stage veinlets mostly infill open-space fissures that crosscut veins and replacements formed in the earlier stages. Four types of Fluid inclusions (FIs), including aqueous (type W), carbonic-aqueous (type C), pure carbonic (type PC) and solid-bearing (type S), are identified at the Tiemurt deposit. The early-stage minerals contain the C- and W-type primary FIs that are totally homogenized at temperatures of 330-390 degrees C with low salinities of 0.8-11.9 wt.% NaCl eqv.; whilst the late-stage quartz or calcite contains only the W-type FIs with homogenization temperatures of 118-205 degrees C, and salinities of 1.4-3.4 wt.% NaCl eqv. This indicates that the ore Fluid system evolved from CO2-rich, probably metamorphic to CO2-poor, meteoric Fluids; and that a significant CO2-escape must have occurred. All the four types of FIs can be only observed in the middle-stage minerals, and even in a microscopic domain of a crystal, representing an association trapped from a Boiling Fluid system. These FIs homogenize at temperatures ranging from 270 to 330 degrees C, with two salinity clusters of 1.9-14.5 and 37.4-42.4 wt.% NaCl eqv., respectively. This implies that metal precipitation resulted from Fluid Boiling, CO2-escape and transient oversaturation. The estimated trapping pressures of FIs range from 130 to 380 MPa, suggesting an alternating lithostatic-hydrostatic Fluid-system, controlled by a fault-valve at the depth of 13 km. Therefore, the Tiemurt Pb-Zn-Cu deposit is likely an example of orogenic Pb-Zn + Cu systems formed in collision orogeny, rather than a pre-collision VMS or Sedex system developed in Devonian; and a new metallogenic model is proposed to interpret the formation of the Tiemurt Pb-Zn-Cu deposit. (C) 2011 Elsevier Ltd. All rights reserved.Geosciences, MultidisciplinarySCI(E)0ARTICLE,SI69-794

Kuidong Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Fluid inclusion and isotopic c h o s and pb constraints on the origin of late mesozoic vein type w mineralization in northern guangdong south china
    Ore Geology Reviews, 2019
    Co-Authors: Hai Jiang, Shaoyong Jiang, Ningjun Peng, Kuidong Zhao
    Abstract:

    Abstract Northern Guangdong of South China occurs many large tungsten deposits, including Shirenzhang, Meiziwo and Yaoling quartz-vein type wolframite deposits. In this study, we carried out a detailed study on Fluid inclusions and C-H-O-S-Pb isotopic analyses of mineral separates for these three deposits, in order to resolve the origin and evolution of ore-forming Fluids and the ore deposition mechanism. The ore veins in these deposits present a similar mineral paragenesis that could be divided into three stages: (I) pre-ore stage, (II) syn-ore stage, and (III) post-ore stage. The pre-ore stage is the magmatic-hydrothermal transition stage, which is marked by Fluid exsolution from the highly fractionated granites, accompanied with potassic alteration and greisenization. The syn-ore stage can be further divided into two stages: silicate-oxide stage (stage II-1) that is characterized by significant tin-tungsten mineral deposition, and sulfide stage (stage II-2) that is characterized by abundant sulfide minerals deposition. The post-ore stage is dominated by quartz and fluorite. The three deposits show similar temperature and salinity variations for syn-ore and post-ore stages. In the Shirenzhang deposit, the Fluid temperature and salinity range from 239 to 301 ℃ and 1.4 to 8.7 wt% NaCl equiv in stage II-1, from 206 to 256 ℃ and 1.4 to 7.0 wt% NaCl equiv in stage II-2, and from 186-236 ℃ and 1.4 to 8.6 wt% NaCl equiv in stage III. In the Meiziwo deposit, the Fluid temperature and salinity range from 242 to 310 ℃ and 1.1 to 8.6 wt% NaCl equiv in stage II-1, from 196 to 252 ℃ and 1.4 to 8.1 wt% NaCl equiv in stage II-2, and from 188-234 ℃ and 1.2 to 7.3 wt% NaCl equiv in stage III. In the Yaoling deposit, the Fluid temperature and salinity range from 230 to 304 ℃ and 1.2 to 9.0 wt% NaCl equiv in stage II-1, from 203 to 258 ℃ and 1.4 to 6.5 wt% NaCl equiv in stage II-2, and from 184-231 ℃ and 1.6 to 8.3 wt% NaCl equiv in stage III. The ore-forming Fluids in the three deposits belong to a medium temperature, low-salinity H 2 O-NaCl system, with trace amounts of volatile components including CO 2 , CH 4 and N 2 . The C-H-O isotope data (δ 13 C CO2 = -18.9 to -6.7‰; δ 18 Owater = +1.1 to +6.3‰; δD H2O = -78 to -55‰) indicate that the ore-forming Fluids were mainly magmatic water, which might be modified by Fluid-rock interaction and mixing with meteoric water. Sulfur (δ 34 S = -7.0 to +0.3‰) and Pb isotope data ( 206 Pb/ 204 Pb = 18.531-18.693, 207 Pb/ 204 Pb = 15.728-15.753, 208 Pb/ 204 Pb = 38.902-39.081) suggest that the ore metal and sulfur are of magmatic origin. The involvement of both organic matter in metasedimentary rocks during Fluid-rock interaction and oxidized meteoric water may have been responsible for the negative δ 34 S and δ 13 C values. Fluid Boiling, Fluid-rock interaction and minor input of meteoric water might have been effective factors for the precipitation of wolframite, cassiterite and scheelite. The sulfide precipitation may have resulted from cooling and dilution of magmatic Fluids by mixing with meteoric water.