{"title":"扬子地块西部新发现的a型花岗岩及其地球化学特征:华南克拉通下脊俯冲的证据","authors":"Awei Mabi, Yanlong Li, Mingchun Zhang, Zhengxi Yang, Niuben Yu","doi":"10.1134/S0869591123060024","DOIUrl":null,"url":null,"abstract":"<p>Numerous Neoproterozoic granitic intrusions occur over a north-south distance of more than 700 km in the western Yangtze Block. In this paper, we use zircon U-Pb age, Lu-Hf isotopic, and whole-rock geochemical data to show that the Shimian granitic pluton, which was previously thought to be S-type granite in the area, is actually A-type granite. The selected fresh samples for this study are mainly porphyritic biotite monzogranites. They are weak peraluminous, A<sub>2</sub>-subtype granites, displaying high contents of SiO<sub>2</sub> and K<sub>2</sub>O, low CaO, and Na<sub>2</sub>O, with the characteristics of high silica, rich potassium, and low sodium. They are enriched in incompatible trace elements, but low in trace elements compatible in mafic silicates and feldspars, and they are chemically characterized by having high REE and Ga abundances and low Al, Ni, Ba, Sr, and Eu abundances. The major and trace element behavior suggests that the granites underwent the process of advanced fractional crystallization and were likely generated by crustal partial melting. Zircon U-Pb age shows the Shimian granitic pluton was emplaced at 728 ± 20 Ma. The studied granites yield an average <sup>176</sup>Hf/<sup>177</sup>Hf value of 0.282363 (ε<sub>Hf</sub> = 0.8) with a 94% confidence interval of 0.282334 to 0.282384 (ε<sub>Hf</sub> = −0.1 to 1.7), indicating that they are derived from the remelting of juvenile continental crust. We suggest that this newly identified A-type granite at Shimian, southwestern China, was more plausibly generated in an extensional setting as a result of slab window caused by ridge subduction, which can account not only for the formation of voluminous granitoids, but also for the basalts, boninitic pillow lavas, and SSZ-type ophiolites in western Yangtze Block.</p>","PeriodicalId":20026,"journal":{"name":"Petrology","volume":null,"pages":null},"PeriodicalIF":1.0000,"publicationDate":"2023-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Newly Identified A-type Granite in Western Yangtze Block and Its Geochemistry Characteristics: Evidence for Ridge Subduction beneath the South China Craton\",\"authors\":\"Awei Mabi, Yanlong Li, Mingchun Zhang, Zhengxi Yang, Niuben Yu\",\"doi\":\"10.1134/S0869591123060024\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Numerous Neoproterozoic granitic intrusions occur over a north-south distance of more than 700 km in the western Yangtze Block. In this paper, we use zircon U-Pb age, Lu-Hf isotopic, and whole-rock geochemical data to show that the Shimian granitic pluton, which was previously thought to be S-type granite in the area, is actually A-type granite. The selected fresh samples for this study are mainly porphyritic biotite monzogranites. They are weak peraluminous, A<sub>2</sub>-subtype granites, displaying high contents of SiO<sub>2</sub> and K<sub>2</sub>O, low CaO, and Na<sub>2</sub>O, with the characteristics of high silica, rich potassium, and low sodium. They are enriched in incompatible trace elements, but low in trace elements compatible in mafic silicates and feldspars, and they are chemically characterized by having high REE and Ga abundances and low Al, Ni, Ba, Sr, and Eu abundances. The major and trace element behavior suggests that the granites underwent the process of advanced fractional crystallization and were likely generated by crustal partial melting. Zircon U-Pb age shows the Shimian granitic pluton was emplaced at 728 ± 20 Ma. The studied granites yield an average <sup>176</sup>Hf/<sup>177</sup>Hf value of 0.282363 (ε<sub>Hf</sub> = 0.8) with a 94% confidence interval of 0.282334 to 0.282384 (ε<sub>Hf</sub> = −0.1 to 1.7), indicating that they are derived from the remelting of juvenile continental crust. We suggest that this newly identified A-type granite at Shimian, southwestern China, was more plausibly generated in an extensional setting as a result of slab window caused by ridge subduction, which can account not only for the formation of voluminous granitoids, but also for the basalts, boninitic pillow lavas, and SSZ-type ophiolites in western Yangtze Block.</p>\",\"PeriodicalId\":20026,\"journal\":{\"name\":\"Petrology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2023-11-27\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Petrology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://link.springer.com/article/10.1134/S0869591123060024\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Petrology","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1134/S0869591123060024","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Newly Identified A-type Granite in Western Yangtze Block and Its Geochemistry Characteristics: Evidence for Ridge Subduction beneath the South China Craton
Numerous Neoproterozoic granitic intrusions occur over a north-south distance of more than 700 km in the western Yangtze Block. In this paper, we use zircon U-Pb age, Lu-Hf isotopic, and whole-rock geochemical data to show that the Shimian granitic pluton, which was previously thought to be S-type granite in the area, is actually A-type granite. The selected fresh samples for this study are mainly porphyritic biotite monzogranites. They are weak peraluminous, A2-subtype granites, displaying high contents of SiO2 and K2O, low CaO, and Na2O, with the characteristics of high silica, rich potassium, and low sodium. They are enriched in incompatible trace elements, but low in trace elements compatible in mafic silicates and feldspars, and they are chemically characterized by having high REE and Ga abundances and low Al, Ni, Ba, Sr, and Eu abundances. The major and trace element behavior suggests that the granites underwent the process of advanced fractional crystallization and were likely generated by crustal partial melting. Zircon U-Pb age shows the Shimian granitic pluton was emplaced at 728 ± 20 Ma. The studied granites yield an average 176Hf/177Hf value of 0.282363 (εHf = 0.8) with a 94% confidence interval of 0.282334 to 0.282384 (εHf = −0.1 to 1.7), indicating that they are derived from the remelting of juvenile continental crust. We suggest that this newly identified A-type granite at Shimian, southwestern China, was more plausibly generated in an extensional setting as a result of slab window caused by ridge subduction, which can account not only for the formation of voluminous granitoids, but also for the basalts, boninitic pillow lavas, and SSZ-type ophiolites in western Yangtze Block.
期刊介绍:
Petrology is a journal of magmatic, metamorphic, and experimental petrology, mineralogy, and geochemistry. The journal offers comprehensive information on all multidisciplinary aspects of theoretical, experimental, and applied petrology. By giving special consideration to studies on the petrography of different regions of the former Soviet Union, Petrology provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.