{"title":"日本中新世花岗岩中锆石微量元素组成:M型、I型、S型和A型花岗岩中锆石的鉴别图","authors":"Yusuke Sawaki, Hisashi Asanuma, Shuhei Sakata, Mariko Abe, Takeshi Ohno","doi":"10.1111/iar.12466","DOIUrl":null,"url":null,"abstract":"<p>Detrital zircons demonstrate high resistance to alteration and, as such retain information about their formation ages and parental magmas for a long period of time. Geochemical researchers have proposed a wide variety of discrimination diagrams applicable to detrital zircons. In our research, we focused on the conventional classification scheme for granites (Mantle, M; Igneous, I; Sedimentary, S; and Alkaline, A types) and sought to characterize zircon trace-element compositions that are sensitive to differences among these granite types. To accomplish this, we examined trace-element compositions of zircons extracted from granitoids in the Ohmine granitic rocks and the Ashizuri plutonic complex in southwestern Japan. The zircons showed systematic differences in Nb/P, Ta/P, Ce/P, Ce/Nd, Y/P, Th/U, and Sc/Yb ratios and the Eu anomaly. Zircons in A-type granite are rich in Nb, Ta, Ce, and Y, and their signatures clearly reflect those elements in their parental bodies. Sc/Yb ratios of zircons in A-type granites are <0.1, which is similar to those of ocean-island-type zircons. Despite their high abundance at the whole-rock level, zircons in S-type granite are characterized by low Nb/P, Ta/P, and Th/U ratios. This is attributable to the depletion of Nb, Ta, and Th in the magma by ilmenite and monazite prior to zircon crystallization. In general, S-type granitic magmas exhibit reducing environments, which decrease the proportions of Ce<sup>4+</sup> and Eu<sup>3+</sup>. These effects lead to a low Ce/Nd ratio and a large negative Eu anomaly in S-type zircons. On the basis of these findings, we recommend the combined use of Nb/P–Ce/P or Ta/P–Ce/P crossplots and of Sc/Yb ratios to discriminate zircons in M-, I-, S-, and A-type granites. Although the crossplots are created using data from Miocene granitoids in Japan, the discrimination diagrams are based on the general features of each type of granite.</p>","PeriodicalId":14791,"journal":{"name":"Island Arc","volume":null,"pages":null},"PeriodicalIF":1.0000,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Zircon trace-element compositions in Miocene granitoids in Japan: Discrimination diagrams for zircons in M-, I-, S-, and A-type granites\",\"authors\":\"Yusuke Sawaki, Hisashi Asanuma, Shuhei Sakata, Mariko Abe, Takeshi Ohno\",\"doi\":\"10.1111/iar.12466\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Detrital zircons demonstrate high resistance to alteration and, as such retain information about their formation ages and parental magmas for a long period of time. Geochemical researchers have proposed a wide variety of discrimination diagrams applicable to detrital zircons. In our research, we focused on the conventional classification scheme for granites (Mantle, M; Igneous, I; Sedimentary, S; and Alkaline, A types) and sought to characterize zircon trace-element compositions that are sensitive to differences among these granite types. To accomplish this, we examined trace-element compositions of zircons extracted from granitoids in the Ohmine granitic rocks and the Ashizuri plutonic complex in southwestern Japan. The zircons showed systematic differences in Nb/P, Ta/P, Ce/P, Ce/Nd, Y/P, Th/U, and Sc/Yb ratios and the Eu anomaly. Zircons in A-type granite are rich in Nb, Ta, Ce, and Y, and their signatures clearly reflect those elements in their parental bodies. Sc/Yb ratios of zircons in A-type granites are <0.1, which is similar to those of ocean-island-type zircons. Despite their high abundance at the whole-rock level, zircons in S-type granite are characterized by low Nb/P, Ta/P, and Th/U ratios. This is attributable to the depletion of Nb, Ta, and Th in the magma by ilmenite and monazite prior to zircon crystallization. In general, S-type granitic magmas exhibit reducing environments, which decrease the proportions of Ce<sup>4+</sup> and Eu<sup>3+</sup>. These effects lead to a low Ce/Nd ratio and a large negative Eu anomaly in S-type zircons. On the basis of these findings, we recommend the combined use of Nb/P–Ce/P or Ta/P–Ce/P crossplots and of Sc/Yb ratios to discriminate zircons in M-, I-, S-, and A-type granites. Although the crossplots are created using data from Miocene granitoids in Japan, the discrimination diagrams are based on the general features of each type of granite.</p>\",\"PeriodicalId\":14791,\"journal\":{\"name\":\"Island Arc\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2022-10-12\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Island Arc\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1111/iar.12466\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Island Arc","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/iar.12466","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
摘要
碎屑锆石表现出很强的抗蚀性,因此可以长时间保留有关其形成时代和母岩浆的信息。地球化学研究人员提出了多种适用于碎屑锆石的判别图。在研究中,我们重点研究了花岗岩的常规分类方案(地幔,M;火成岩,我;沉积年代;和碱性,A型),并试图表征锆石微量元素组成,这些元素对这些花岗岩类型之间的差异很敏感。为了实现这一目标,我们研究了从日本西南部大明花岗质岩石和朝日深成杂岩中的花岗质中提取的锆石的微量元素组成。锆石的Nb/P、Ta/P、Ce/P、Ce/Nd、Y/P、Th/U、Sc/Yb比值及Eu异常均存在系统差异。a型花岗岩锆石富含Nb、Ta、Ce、Y等元素,其特征在母体中反映明显。a型花岗岩中锆石的Sc/Yb比值为<0.1,与洋岛型锆石相似。s型花岗岩锆石整体丰度较高,但具有较低的Nb/P、Ta/P和Th/U的特征。这是由于在锆石结晶之前,钛铁矿和独居石耗尽了岩浆中的Nb、Ta和Th。s型花岗岩岩浆总体上呈现还原环境,使Ce4+和Eu3+的比例降低。这些影响导致s型锆石Ce/Nd比值较低,Eu负异常较大。在此基础上,我们建议联合使用Nb/P - ce /P或Ta/P - ce /P交叉图和Sc/Yb比值来区分M型、I型、S型和a型花岗岩中的锆石。虽然交叉图是利用日本中新世花岗岩类的数据绘制的,但区分图是基于每种花岗岩的一般特征。
Zircon trace-element compositions in Miocene granitoids in Japan: Discrimination diagrams for zircons in M-, I-, S-, and A-type granites
Detrital zircons demonstrate high resistance to alteration and, as such retain information about their formation ages and parental magmas for a long period of time. Geochemical researchers have proposed a wide variety of discrimination diagrams applicable to detrital zircons. In our research, we focused on the conventional classification scheme for granites (Mantle, M; Igneous, I; Sedimentary, S; and Alkaline, A types) and sought to characterize zircon trace-element compositions that are sensitive to differences among these granite types. To accomplish this, we examined trace-element compositions of zircons extracted from granitoids in the Ohmine granitic rocks and the Ashizuri plutonic complex in southwestern Japan. The zircons showed systematic differences in Nb/P, Ta/P, Ce/P, Ce/Nd, Y/P, Th/U, and Sc/Yb ratios and the Eu anomaly. Zircons in A-type granite are rich in Nb, Ta, Ce, and Y, and their signatures clearly reflect those elements in their parental bodies. Sc/Yb ratios of zircons in A-type granites are <0.1, which is similar to those of ocean-island-type zircons. Despite their high abundance at the whole-rock level, zircons in S-type granite are characterized by low Nb/P, Ta/P, and Th/U ratios. This is attributable to the depletion of Nb, Ta, and Th in the magma by ilmenite and monazite prior to zircon crystallization. In general, S-type granitic magmas exhibit reducing environments, which decrease the proportions of Ce4+ and Eu3+. These effects lead to a low Ce/Nd ratio and a large negative Eu anomaly in S-type zircons. On the basis of these findings, we recommend the combined use of Nb/P–Ce/P or Ta/P–Ce/P crossplots and of Sc/Yb ratios to discriminate zircons in M-, I-, S-, and A-type granites. Although the crossplots are created using data from Miocene granitoids in Japan, the discrimination diagrams are based on the general features of each type of granite.
期刊介绍:
Island Arc is the official journal of the Geological Society of Japan. This journal focuses on the structure, dynamics and evolution of convergent plate boundaries, including trenches, volcanic arcs, subducting plates, and both accretionary and collisional orogens in modern and ancient settings. The Journal also opens to other key geological processes and features of broad interest such as oceanic basins, mid-ocean ridges, hot spots, continental cratons, and their surfaces and roots. Papers that discuss the interaction between solid earth, atmosphere, and bodies of water are also welcome. Articles of immediate importance to other researchers, either by virtue of their new data, results or ideas are given priority publication.
Island Arc publishes peer-reviewed articles and reviews. Original scientific articles, of a maximum length of 15 printed pages, are published promptly with a standard publication time from submission of 3 months. All articles are peer reviewed by at least two research experts in the field of the submitted paper.