Jin-Lei Sun, Zhong-Jie Bai, Hong Zhong, Xu Liu, Jing-Jing Zhu, Lan Chen, Wei-Guang Zhu
{"title":"冈底斯幼生下地壳生成过程中还原岩浆中的硫化物饱和:对西藏冈底斯带斑岩型铜金矿化的影响","authors":"Jin-Lei Sun, Zhong-Jie Bai, Hong Zhong, Xu Liu, Jing-Jing Zhu, Lan Chen, Wei-Guang Zhu","doi":"10.1007/s00126-024-01269-0","DOIUrl":null,"url":null,"abstract":"<p>The S saturation and oxidation states of arc magmas are important factors in the formation of porphyry Cu–Au deposits. The Milin juvenile lower crustal cumulates (86.7–84.3 Ma) in the Gangdese provide insights into how sulfide saturation and oxidation states control porphyry mineralization. Zircons from the cumulates have low Ce<sup>4+</sup>/Ce<sup>3+</sup> ratios (21–90) and reduced oxygen fugacities (ΔFMQ–1.8±0.5), which cannot be explained by fractional crystallization or crustal contamination, suggesting inheritance from a mantle source. Partial melting of the mantle under reduced conditions produced a sulfide-saturated primary arc magma with low chalcophile element contents owing to the residual sulfide in the mantle. The Milin lower crustal cumulates contain sulfides, indicating that the magma reached sulfide saturation in the early stages of magmatic differentiation. Based on our model, the primary arc magma before sulfide saturation contained 66.7 ppm Cu and 1.0 ppb Au. The residual magma after sulfide saturation in the lower crust contained 33–66 ppm Cu, 0.13–0.93 ppb Au; i.e., lower contents than those in arc basalts worldwide. Both these factors hindered the formation of Late Cretaceous large porphyry Cu–Au deposits in the Gangdese belt. Remelting of the Milin sulfide-rich cumulates can generate a Cu-rich andesitic magma only under high temperature and high-<i>fO</i><sub><i>2</i></sub> conditions, and a melt with low Cu content under low temperature even high-<i>fO</i><sub><i>2</i></sub> conditions. Thus, the temperature plays a crucial role in the remelting of the lower crust whether provide enough metals to match the Gangdese Miocene post-collisional porphyry Cu deposit.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"25 1","pages":""},"PeriodicalIF":4.4000,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Sulfide saturation in reduced magmas during generation of the Gangdese juvenile lower crust: Implications for porphyry Cu–Au mineralization in the Gangdese belt, Tibet\",\"authors\":\"Jin-Lei Sun, Zhong-Jie Bai, Hong Zhong, Xu Liu, Jing-Jing Zhu, Lan Chen, Wei-Guang Zhu\",\"doi\":\"10.1007/s00126-024-01269-0\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>The S saturation and oxidation states of arc magmas are important factors in the formation of porphyry Cu–Au deposits. The Milin juvenile lower crustal cumulates (86.7–84.3 Ma) in the Gangdese provide insights into how sulfide saturation and oxidation states control porphyry mineralization. Zircons from the cumulates have low Ce<sup>4+</sup>/Ce<sup>3+</sup> ratios (21–90) and reduced oxygen fugacities (ΔFMQ–1.8±0.5), which cannot be explained by fractional crystallization or crustal contamination, suggesting inheritance from a mantle source. Partial melting of the mantle under reduced conditions produced a sulfide-saturated primary arc magma with low chalcophile element contents owing to the residual sulfide in the mantle. The Milin lower crustal cumulates contain sulfides, indicating that the magma reached sulfide saturation in the early stages of magmatic differentiation. Based on our model, the primary arc magma before sulfide saturation contained 66.7 ppm Cu and 1.0 ppb Au. The residual magma after sulfide saturation in the lower crust contained 33–66 ppm Cu, 0.13–0.93 ppb Au; i.e., lower contents than those in arc basalts worldwide. Both these factors hindered the formation of Late Cretaceous large porphyry Cu–Au deposits in the Gangdese belt. Remelting of the Milin sulfide-rich cumulates can generate a Cu-rich andesitic magma only under high temperature and high-<i>fO</i><sub><i>2</i></sub> conditions, and a melt with low Cu content under low temperature even high-<i>fO</i><sub><i>2</i></sub> conditions. Thus, the temperature plays a crucial role in the remelting of the lower crust whether provide enough metals to match the Gangdese Miocene post-collisional porphyry Cu deposit.</p>\",\"PeriodicalId\":18682,\"journal\":{\"name\":\"Mineralium Deposita\",\"volume\":\"25 1\",\"pages\":\"\"},\"PeriodicalIF\":4.4000,\"publicationDate\":\"2024-04-24\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Mineralium Deposita\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1007/s00126-024-01269-0\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Mineralium Deposita","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1007/s00126-024-01269-0","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Sulfide saturation in reduced magmas during generation of the Gangdese juvenile lower crust: Implications for porphyry Cu–Au mineralization in the Gangdese belt, Tibet
The S saturation and oxidation states of arc magmas are important factors in the formation of porphyry Cu–Au deposits. The Milin juvenile lower crustal cumulates (86.7–84.3 Ma) in the Gangdese provide insights into how sulfide saturation and oxidation states control porphyry mineralization. Zircons from the cumulates have low Ce4+/Ce3+ ratios (21–90) and reduced oxygen fugacities (ΔFMQ–1.8±0.5), which cannot be explained by fractional crystallization or crustal contamination, suggesting inheritance from a mantle source. Partial melting of the mantle under reduced conditions produced a sulfide-saturated primary arc magma with low chalcophile element contents owing to the residual sulfide in the mantle. The Milin lower crustal cumulates contain sulfides, indicating that the magma reached sulfide saturation in the early stages of magmatic differentiation. Based on our model, the primary arc magma before sulfide saturation contained 66.7 ppm Cu and 1.0 ppb Au. The residual magma after sulfide saturation in the lower crust contained 33–66 ppm Cu, 0.13–0.93 ppb Au; i.e., lower contents than those in arc basalts worldwide. Both these factors hindered the formation of Late Cretaceous large porphyry Cu–Au deposits in the Gangdese belt. Remelting of the Milin sulfide-rich cumulates can generate a Cu-rich andesitic magma only under high temperature and high-fO2 conditions, and a melt with low Cu content under low temperature even high-fO2 conditions. Thus, the temperature plays a crucial role in the remelting of the lower crust whether provide enough metals to match the Gangdese Miocene post-collisional porphyry Cu deposit.
期刊介绍:
The journal Mineralium Deposita introduces new observations, principles, and interpretations from the field of economic geology, including nonmetallic mineral deposits, experimental and applied geochemistry, with emphasis on mineral deposits. It offers short and comprehensive articles, review papers, brief original papers, scientific discussions and news, as well as reports on meetings of importance to mineral research. The emphasis is on high-quality content and form for all articles and on international coverage of subject matter.