Abstract
The Tongkuangyu copper deposit, North China Craton, is hosted in a volcano-sedimentary sequence (ca. 2.2 Ga) that metamorphosed to the lower amphibolite facies at ca. 1.9 Ga. Petrographic observations revealed various metamorphic fabrics (mineral alignment and foliations) and several generations of biotite, chlorite, and pyrite. Sulfide Pb-Pb dating indicates that copper mineralization occurred at 1960+46/−58 Ma, younger than the zircon U-Pb age of the host metatuff (2180 Ma to 2190 Ma), but close to the timing of regional metamorphism (ca. 1.9 Ga). Electron probe analyses show that the biotites belong to the magnesium-rich variety, and were formed at 470 to 500 ° C based on Ti-in-biotite thermometry. Chlorites belong to ripidolite and pycnochlorite, and were formed at ca. 350 ° C based on the Al geothermometer. Pyrites in porphyry, metatuffs, and quartz veins have contrasting Ni and Co concentrations, pointing to a local remobilization. Hydrogen and oxygen isotopic analyses suggest that biotite and chlorite were formed by metamorphic waters whereas quartz records much lower δ D f l u i d values, reflecting the influence of meteoric water. Fluid inclusions in pyrite and chalcopyrite in metatuff and quartz vein contain extremely radiogenic 4 He and 40 Ar, indicating a crustal origin for the fluids. Sulfides show a magmatic sulfur isotopic signature, likely indicating the presence of preexisting volcanism-related sulfides. We proposed that the early layered copper sulfides formed during metamorphic retrogression at ca. 1.9 Ga and the late vein-type sulfides were derived from the remobilization of the earlier sulfides by infiltration of external fluids such as residual seawater and metamorphic fluids at shallow level.
Highlights
The Tongkuangyu copper deposit (>3 million tonnes of copper reserves) is one of the largest copper suppliers in Northern China, and has a mining history of nearly 3400 years dating back to theShang Dynasty [1]
Xie [3] suggested that the copper mineralization was related to sedimentation and subsequent metamorphic modification based on field observations of sulfide distribution
We proposed that the Tongkuangyu copper mineralizations are products of sulfide remobilization due to retrograde metamorphism
Summary
The Tongkuangyu copper deposit (>3 million tonnes of copper reserves) is one of the largest copper suppliers in Northern China, and has a mining history of nearly 3400 years dating back to theShang Dynasty [1]. The Tongkuangyu copper deposit (>3 million tonnes of copper reserves) is one of the largest copper suppliers in Northern China, and has a mining history of nearly 3400 years dating back to the. Based on the presence of porphyry, disseminated sulfides, and biotite–sericite alteration, Wang and Wen [2] inferred that it was formed by porphyry-related hydrothermal process. Xie [3] suggested that the copper mineralization was related to sedimentation and subsequent metamorphic modification based on field observations of sulfide distribution. Minerals 2019, 9, 443 electron probe microanalysis and related their formation with the exhalation of magmatic waters under seafloor. A genetic model involving porphyry mineralization with metamorphic modification was put forward and favored on the basis of sulfur isotopes [5], H-O isotopes [6], and Re-Os geochronology [7]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
