Research Article| March 01, 2019 Mineralogy, Fluid Inclusion, and Stable Isotope Studies of the Chengchao Deposit, Hubei Province, Eastern China: Implications for the Formation of High-Grade Fe Skarn Deposits Wei Li; Wei Li 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China2Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China Search for other works by this author on: GSW Google Scholar Guiqing Xie; Guiqing Xie 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China †Corresponding author: e-mail, xieguiqing@cags.ac.cn Search for other works by this author on: GSW Google Scholar Jingwen Mao; Jingwen Mao 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China Search for other works by this author on: GSW Google Scholar Qiaoqiao Zhu; Qiaoqiao Zhu 1Ministry of Natural Resources (MNR) Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences (CAGS), Beijing 100037, China Search for other works by this author on: GSW Google Scholar Jiahao Zheng Jiahao Zheng 3Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen 518055, China Search for other works by this author on: GSW Google Scholar Economic Geology (2019) 114 (2): 325–352. https://doi.org/10.5382/econgeo.2019.4633 Article history accepted: 13 Feb 2019 first online: 27 Mar 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Wei Li, Guiqing Xie, Jingwen Mao, Qiaoqiao Zhu, Jiahao Zheng; Mineralogy, Fluid Inclusion, and Stable Isotope Studies of the Chengchao Deposit, Hubei Province, Eastern China: Implications for the Formation of High-Grade Fe Skarn Deposits. Economic Geology 2019;; 114 (2): 325–352. doi: https://doi.org/10.5382/econgeo.2019.4633 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract The Chengchao Fe skarn deposit (280 Mt @ 45% Fe; nearly half of the total Fe reserve has an ore grade higher than 53 wt %) is the largest high-grade magnetite skarn deposit in the Middle-Lower Yangtze River metallogenic belt. The magnetite orebodies and skarns occur mainly along the contact zones between granitic (129 ± 2 Ma) rocks and diorite (133 ± 1 Ma) and Triassic strata. The paragenesis of the Chengchao deposit includes the following five stages: Na-K alteration stage (albite + K-feldspar), prograde skarn stage (garnet + pyroxene), retrograde skarn stage (magnetite + phlogopite + amphibole), sulfate-sulfide stage (anhydrite + pyrite ± garnet ± magnetite), and carbonate stage (calcite).Four generations of garnet and magnetite with distinct textures are recognized. The elemental compositions and fluid inclusion data of the three generations of garnet from the prograde skarn stage indicate fluctuating changes in the oxygen fugacity during their precipitation. Some magnetite grains from the retrograde skarn stage are characterized by well-developed zonation with respect to Al, K, Ca, and Si, with concentrations of up to hundreds of parts per million. The higher contents of (V + Ti) and (Al + Mn) in Mt2 relative to Mt1 (0.8 and 2,321 ppm for Mt1, and 182 and 10,315 ppm for Mt2, respectively) may be indicative of increasing fluid temperatures from episodic magmatic events. Fluid inclusion data show that the fluids responsible for the prograde skarn stage have high temperature (>750°C), high salinity (>50 wt % NaCl equiv) and high Fe concentration (e.g., magnetite and pyrite daughter crystals within garnet and pyroxene). Oxygen and hydrogen isotope data suggest that magmatic water was dominant during the prograde skarn stage and that increasing percentages of meteoric water were involved during later stages. Multiple episodic incursions of Fe-rich fluids, which were probably related to the emplacement of granitic rocks and diorite, were crucial for controlling the formation of the high-grade Chengchao Fe skarn deposit. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
The Katbasu Au-Cu deposit in the Chinese Western Tianshan is hosted in the ca. 355 Ma granite intrusion. This paper reports whole-rock geochemical and zircon Hf-O isotopic data for the granites and the mafic enclaves as well as in situ S isotopic data for the sulfides from the Katbasu Au-Cu deposit. Our results provide constraints on the petrogenesis and ore genesis of the Katbasu Au-Cu deposit. Geochemical characteristics suggest that the Katbasu granites are metaluminous rocks, exhibiting mineral assemblages and geochemical characteristics of I-type granites. The granites have positive zircon εHf(t) values of 7.1-10.2 and zircon δ18O values of 6.2-7.2‰, suggesting a juvenile crustal origin. Mixing processes between felsic and mafic magmas were involved in their generation. The mafic enclaves are enriched in LILEs and depleted in HFSEs, and have zircon εHf(t) values of 7.5-15.8 and zircon δ18O values of 5.4-6.9‰, suggesting that they were derived from a subduction-modified mantle and underwent subsequent crustal contamination and/or magma mixing processes. In situ S isotopic analyses show that pyrite grains from the pre-ore stage and post-ore stage have positive δ34S values of 7.0-8.5‰ and 8.2-9.0‰, respectively. Pyrite and chalcopyrite grains from an early magmatic-hydrothermal Cu-Au mineralization stage show δ34S values of 8.8-11.1‰, and pyrite grains from the main orogenic Au mineralization stage have positive δ34S values of 5.9-8.4‰. The heavy S isotope characteristics of magmatic-hydrothermal Cu-Au mineralization indicate that the magma source might be metasomatized by subduction materials, whereas the S isotope characteristics of the late orogenic gold mineralization suggest that the ore-forming materials mainly originated from the metamorphic devolatilization of the source rocks. The ca.352-349 Ma early magmatic-hydrothermal Cu-Au mineralization in the Katbasu deposit formed in a subduction tectonic setting, whereas the ca. 323-311 Ma late orogenic Au mineralization formed in an orogenic environment during the final stage of subduction.
Abstract The Cihai iron‐cobalt deposit is located in the southern part of the eastern Tianshan iron‐polymetallic metallogenic belt. Anomalous native gold and bismuth have been newly identified in Cinan mining section of the Cihai deposit. Ore formation in the deposit can be divided into three stages based on geological and petrographical observations: (I) skarn, with the main mineral assemblage being garnet‐pyroxene‐magnetite; (II) retrograde alteration, forming the main iron ores and including massive magnetite, native gold, native bismuth, and cobalt‐bearing minerals, with the main mineral assemblage being ilvaite‐magnetite‐native gold‐native bismuth; and (III) quartz‐calcite‐sulfide assemblage that contains quartz, calcite, pyrrhotite, cobaltite, and safflorite. Native gold mainly coexists with native bismuth, and they are paragenetically related. The temperature of initial skarn formation was higher than 340°C, and then subsequently decreased to ∼312°C and ∼266°C. The temperature of the hydrothermal fluid during the iron ore depositional event was higher than the melting point of native bismuth (271°C), and native bismuth melt scavenged gold in the hydrothermal fluid, forming a Bi‐Au melt. As the temperature decreased, the Bi‐Au melt was decomposed into native gold and native bismuth. The native gold and native bismuth identified during this study can provide a scientific basis for prospecting and exploration for both gold‐ and bismuth‐bearing deposits in the Cihai mining area. The gold mineralization in Cihai is a part of the Early Permian Cu‐Ni‐Au‐Fe polymetallic ore‐forming event, and its discovery has implications for the resource potential of other iron skarn deposits in the eastern Tianshan.
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