Comparison of natures of barren and fertile intrusions in the Kounrad ore district, Kazakhstan and its implication for mineralization
哈萨克斯坦科翁腊德矿集区贫矿和成矿岩体性质对比 及其对成矿的启示
Li C. Pan H. Suo Q. Chu X. Seitmuratova E.
2023Science Press
Yanshi Xuebao/Acta Petrologica Sinica
2023#39Issue 113263 - 3283 pp.
Numerous large to giant porphyry Cu deposits have developed in the Central Asian Orogenic Belt. Although these deposits usually developed large-scale magmatism at similar ages, there is usually only a few magmatism associated with mineralization. Therefore, distinguishing between mineralized and barren magmas in the ore district is crucial to prospecting. To investigate this question, this study performs textural and compositional analyses of apatite, amphibole, biotite, and plagioclase and whole-rock major element analyses of weakly altered rocks from the Carboniferous barren intrusions and fertile granodiorite porphyry in the Kounrad ore district, Kazakhstan. Results show that both the barren intrusions and fertile granodiorite porphyry are H20-rich (>~4%) oxidized (>~ΔNNO+1.63) magmas, which belong to the medium K or high K calcium-alkaline series rocks. Significant An values variations in plagioclase (ΔAn in the range of 26~34) and positive correlation with FeO content in barren intrusions suggest that it underwent magma mixing during the intrusion formation, whereas this process was not evident in the fertile granodiorite porphyry. Comparison of apatite, amphibole, and biotite compositions shows that the oxygen fugacity and H20 content of the fertile granodiorite porphyry is not significantly different from that of the barren intrusions, but the fertile granodiorite porphyry has higher Cl and S content. Studies on the texture and composition of magmatic minerals indicate that the magma that migrates to the shallow part of the crust still contains sufficient Cl, S, and metal elements is the key to the formation of porphyry Cu deposits in the Kounrad ore district. In Kounrad ore district, magmas with favorable Cu mineralization conditions (e.g., suitable oxygen fugacity, H20 content, and presence of mafic magma recharge) may lose Cl, S, and metal elements from the magma because of early fluid exsolution at deeper depths (e.g., barren gabbro, diorite, granodiorite), or the magma has a low Cl content and low Cu solubility, resulting in low ability to transport and enrich metal elements (e.g., barren granite), ultimately failing to form porphyry Cu deposits. The results of this study show that the Cl and S contents of magma in the Kounrad ore district are effective signs to distinguish fertile and barren intrusions, while the oxygen fugacity, H20 content, and F content of magma are no significant difference.
Amphibole , Apatite , Biotite , Central Asian Orogenic Belt , Plagioclase , Porphyry Cu deposit
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Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing, 100029, China
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
College of Earth Sciences, Changan University, Xian, 710054, China
Laboratory of Geological Formations, K Satpaev Institute of Geological Sciences, Almaty, 050010, Kazakhstan
Key Laboratory of Mineral Resources
Innovation Academy for Earth Science
College of Earth and Planetary Sciences
College of Earth Sciences
Laboratory of Geological Formations
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