Geology and mineralization of the Yangla polymetallic orefield in northwestern Yunnan, SW China: Age, petrogenesis and rare-metal metallogenic implications of aplite dykes
{"title":"Geology and mineralization of the Yangla polymetallic orefield in northwestern Yunnan, SW China: Age, petrogenesis and rare-metal metallogenic implications of aplite dykes","authors":"","doi":"10.1016/j.oregeorev.2024.106315","DOIUrl":null,"url":null,"abstract":"<div><div>Aplite dykes commonly represent more evolved magma and are closely associated with rare metal mineralization. However, the multiphase magmatism and rare metal mineralization of aplite dykes in the Yangla orefield have not been well-constrained. Here, we present new data on the Linong aplite dykes and the associated Jiangbian granodiorite in the Yangla orefield, including data of zircon U-Pb age and Hf isotopes, and lithogeochemistry and Pb-Sr-Nd isotopes, in order to elucidate their emplacement age, petrogenesis, and rare metal mineralization potential. The three aplite dykes studied were emplaced at 214.3 ± 5.1 Ma, 209.2 ± 5.2 Ma, and 205.5 ± 3.4 Ma. These Late Triassic aplite dykes have high SiO<sub>2</sub> (75.81–76.94 wt%) and K<sub>2</sub>O (avg. 5.60 wt%) and are peralkaline–metaluminous (A/CNK = 0.86–0.93). They have high whole-rock (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> (0.6947–0.7094), ε<sub>Nd</sub>(t) (−6.26 to − 5.77), (<sup>206</sup>Pb/<sup>204</sup>Pb)<sub>t</sub> = 18.365–18.804, (<sup>207</sup>Pb/<sup>204</sup>Pb)<sub>t</sub> = 15.688–15.715, (<sup>208</sup>Pb/<sup>204</sup>Pb)<sub>t</sub> = 38.436–38.681, and zircon ε<sub>Hf</sub>(t) = − 8.10 to + 1.62. The Triassic (208–228 Ma) Jiangbian granodiorite is high-K calc-alkaline, metaluminous/weakly peraluminous (A/CNK = 0.52–1.19) with high Al<sub>2</sub>O<sub>3</sub> (12.49–16.74 wt%). They have high (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> (0.7075–0.7102), whole-rock ε<sub>Nd</sub>(t) (−6.12 to − 5.88), (<sup>206</sup>Pb/<sup>204</sup>Pb)<sub>t</sub> = 18.155–18.384, (<sup>207</sup>Pb/<sup>204</sup>Pb)<sub>t</sub> = 15.665–15.698, (<sup>208</sup>Pb/<sup>204</sup>Pb)<sub>t</sub> = 38.579–38.719, and zircon ε<sub>Hf</sub>(t) = − 4.20 to + 2.40. These geochemical features imply that both the aplite dykes and granodiorite have their primary magma derived from partial melting of the Proterozoic basement, with minor mantle input. The aplite samples have an average estimated crystallization temperature of 712 ℃, and relatively low magmatic oxygen fugacity ([log(fo<sub>2</sub>)] = − 21.98 to – 5.48, avg. = –17.05), which are slightly higher than that of most Triassic granitoids in the Yangla orefield. The result shows that the crystallization temperature and oxygen fugacity gradually increase, while the <sup>176</sup>Hf/<sup>177</sup>Hf and ε<sub>Hf</sub>(t) gradually decrease. Our new and published geochemical data from the Yangla granitoids reveal that the aplite dykes and granodiorite were formed in a post-collisional setting. Whole-rock Nb/Ta, Zr/Hf, Rb/Sr, Ba/Rb, and zircon REE features of the aplite dykes highly mimic those of typical Sn-W related granites, suggesting certain Sn-W rare metals mineralization potential in the Yangla orefield.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Ore Geology Reviews","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0169136824004487","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Aplite dykes commonly represent more evolved magma and are closely associated with rare metal mineralization. However, the multiphase magmatism and rare metal mineralization of aplite dykes in the Yangla orefield have not been well-constrained. Here, we present new data on the Linong aplite dykes and the associated Jiangbian granodiorite in the Yangla orefield, including data of zircon U-Pb age and Hf isotopes, and lithogeochemistry and Pb-Sr-Nd isotopes, in order to elucidate their emplacement age, petrogenesis, and rare metal mineralization potential. The three aplite dykes studied were emplaced at 214.3 ± 5.1 Ma, 209.2 ± 5.2 Ma, and 205.5 ± 3.4 Ma. These Late Triassic aplite dykes have high SiO2 (75.81–76.94 wt%) and K2O (avg. 5.60 wt%) and are peralkaline–metaluminous (A/CNK = 0.86–0.93). They have high whole-rock (87Sr/86Sr)i (0.6947–0.7094), εNd(t) (−6.26 to − 5.77), (206Pb/204Pb)t = 18.365–18.804, (207Pb/204Pb)t = 15.688–15.715, (208Pb/204Pb)t = 38.436–38.681, and zircon εHf(t) = − 8.10 to + 1.62. The Triassic (208–228 Ma) Jiangbian granodiorite is high-K calc-alkaline, metaluminous/weakly peraluminous (A/CNK = 0.52–1.19) with high Al2O3 (12.49–16.74 wt%). They have high (87Sr/86Sr)i (0.7075–0.7102), whole-rock εNd(t) (−6.12 to − 5.88), (206Pb/204Pb)t = 18.155–18.384, (207Pb/204Pb)t = 15.665–15.698, (208Pb/204Pb)t = 38.579–38.719, and zircon εHf(t) = − 4.20 to + 2.40. These geochemical features imply that both the aplite dykes and granodiorite have their primary magma derived from partial melting of the Proterozoic basement, with minor mantle input. The aplite samples have an average estimated crystallization temperature of 712 ℃, and relatively low magmatic oxygen fugacity ([log(fo2)] = − 21.98 to – 5.48, avg. = –17.05), which are slightly higher than that of most Triassic granitoids in the Yangla orefield. The result shows that the crystallization temperature and oxygen fugacity gradually increase, while the 176Hf/177Hf and εHf(t) gradually decrease. Our new and published geochemical data from the Yangla granitoids reveal that the aplite dykes and granodiorite were formed in a post-collisional setting. Whole-rock Nb/Ta, Zr/Hf, Rb/Sr, Ba/Rb, and zircon REE features of the aplite dykes highly mimic those of typical Sn-W related granites, suggesting certain Sn-W rare metals mineralization potential in the Yangla orefield.
期刊介绍:
Ore Geology Reviews aims to familiarize all earth scientists with recent advances in a number of interconnected disciplines related to the study of, and search for, ore deposits. The reviews range from brief to longer contributions, but the journal preferentially publishes manuscripts that fill the niche between the commonly shorter journal articles and the comprehensive book coverages, and thus has a special appeal to many authors and readers.