Coeval formation and exhumation of metamorphic sole and ophiolite in the Saga ophiolitic mélange: Insights into subduction initiation of the Neo-Tethys

IF 3.5 2区 地球科学 Q1 GEOLOGY
Jie Shen, Jingen Dai, Kai Yang, Lingling Zhao, Wencang Zhang, Nadia Malaspina's, Pietro Sternai's
{"title":"Coeval formation and exhumation of metamorphic sole and ophiolite in the Saga ophiolitic mélange: Insights into subduction initiation of the Neo-Tethys","authors":"Jie Shen,&nbsp;Jingen Dai,&nbsp;Kai Yang,&nbsp;Lingling Zhao,&nbsp;Wencang Zhang,&nbsp;Nadia Malaspina's,&nbsp;Pietro Sternai's","doi":"10.1111/jmg.12776","DOIUrl":null,"url":null,"abstract":"<p>Subduction initiation is recorded by upper plate magmatism and lower plate metamorphism, that is, supra-subduction zone (SSZ) ophiolite–metamorphic sole pair. Here, we report geochemical and geochronological data as well as P–T calculations of amphibolites (metamorphic sole) and hornblende gabbros (SSZ ophiolite) from the Saga ophiolitic mélange in Tibetan Plateau. Amphibolites show trace element contents compatible with normal-mid-ocean ridge basalt (N-MORB), indicating that the protolith of amphibolite formed in a MOR setting. Instead, hornblende gabbros show significant high field strength elements (HFSEs) negative anomalies, enriched large ion lithophile elements (LILEs) and high zircon ε<sub>Hf</sub>(t) values, suggesting they formed by fluid-induced partial melting of a depleted mantle. Thermobarometry and phase equilibrium modelling suggest two stages of metamorphism for garnet–clinopyroxene amphibolites: (I) a peak metamorphic stage (~1.9 GPa and 1000°C) and (II) a retrograde metamorphic stage (1.1–1.6 GPa and 800–1000°C). Zircon U–Pb ages of amphibolite and hornblende gabbro are 128.8 ± 5.1 Ma and 128.1 ± 1.5 Ma, respectively, suggesting subduction initiation within the eastern Neo-Tethys occurred no later than 128 Ma and SSZ ophiolite formed at ~128 Ma. Apatite U–Pb ages of amphibolite and hornblende gabbro are 121.8 ± 2.1 Ma and 117.5 ± 4.5 Ma, respectively. Titanite U–Pb age of amphibolite is 122.2 ± 1.5 Ma. Overall, our data suggest that the metamorphic sole and SSZ ophiolite were exhumed since 128–118 Ma, and finally exhumed into the ophiolitic mélange.</p>","PeriodicalId":16472,"journal":{"name":"Journal of Metamorphic Geology","volume":"42 6","pages":"843-865"},"PeriodicalIF":3.5000,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Metamorphic Geology","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/jmg.12776","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

Subduction initiation is recorded by upper plate magmatism and lower plate metamorphism, that is, supra-subduction zone (SSZ) ophiolite–metamorphic sole pair. Here, we report geochemical and geochronological data as well as P–T calculations of amphibolites (metamorphic sole) and hornblende gabbros (SSZ ophiolite) from the Saga ophiolitic mélange in Tibetan Plateau. Amphibolites show trace element contents compatible with normal-mid-ocean ridge basalt (N-MORB), indicating that the protolith of amphibolite formed in a MOR setting. Instead, hornblende gabbros show significant high field strength elements (HFSEs) negative anomalies, enriched large ion lithophile elements (LILEs) and high zircon εHf(t) values, suggesting they formed by fluid-induced partial melting of a depleted mantle. Thermobarometry and phase equilibrium modelling suggest two stages of metamorphism for garnet–clinopyroxene amphibolites: (I) a peak metamorphic stage (~1.9 GPa and 1000°C) and (II) a retrograde metamorphic stage (1.1–1.6 GPa and 800–1000°C). Zircon U–Pb ages of amphibolite and hornblende gabbro are 128.8 ± 5.1 Ma and 128.1 ± 1.5 Ma, respectively, suggesting subduction initiation within the eastern Neo-Tethys occurred no later than 128 Ma and SSZ ophiolite formed at ~128 Ma. Apatite U–Pb ages of amphibolite and hornblende gabbro are 121.8 ± 2.1 Ma and 117.5 ± 4.5 Ma, respectively. Titanite U–Pb age of amphibolite is 122.2 ± 1.5 Ma. Overall, our data suggest that the metamorphic sole and SSZ ophiolite were exhumed since 128–118 Ma, and finally exhumed into the ophiolitic mélange.

萨嘎蛇绿混杂岩中变质鳎目岩和蛇绿混杂岩的共时形成和掘起:对新特提斯俯冲起始的见解
上板块岩浆作用和下板块变质作用(即超俯冲带(SSZ)蛇绿岩-变质鳎岩对)记录了俯冲的开始。在此,我们报告了青藏高原萨嘎蛇绿岩混杂区的闪长岩(变质鳎目岩)和角闪岩(SSZ蛇绿岩)的地球化学和地质年代数据以及P-T计算结果。闪长岩的微量元素含量与正中洋脊玄武岩(N-MORB)相符,表明闪长岩的原岩是在MOR环境中形成的。相反,角闪石辉长岩显示出显著的高场强元素(HFSEs)负异常、富集的大离子亲岩元素(LILEs)和高锆石εHf(t)值,表明它们是由贫化地幔的流体诱导部分熔融形成的。热压测量和相平衡模型表明石榴石-辉石闪长岩的变质作用分为两个阶段:(I)峰值变质阶段(~1.9 GPa 和 1000°C)和(II)逆行变质阶段(1.1-1.6 GPa 和 800-1000°C)。闪长岩和角闪长辉长岩的锆石U-Pb年龄分别为128.8 ± 5.1 Ma和128.1 ± 1.5 Ma,表明新特提斯东部的俯冲起始时间不晚于128 Ma,SSZ蛇绿岩形成于约128 Ma。闪长岩和角闪长辉长岩的磷灰石U-Pb年龄分别为121.8 ± 2.1 Ma和117.5 ± 4.5 Ma。闪长岩的榍石 U-Pb 年龄为 122.2 ± 1.5 Ma。总体而言,我们的数据表明,变质独居岩和SSZ蛇绿岩自128-118 Ma开始蜕变,最后蜕变成蛇绿岩混合体。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
CiteScore
6.60
自引率
11.80%
发文量
57
审稿时长
6-12 weeks
期刊介绍: The journal, which is published nine times a year, encompasses the entire range of metamorphic studies, from the scale of the individual crystal to that of lithospheric plates, including regional studies of metamorphic terranes, modelling of metamorphic processes, microstructural and deformation studies in relation to metamorphism, geochronology and geochemistry in metamorphic systems, the experimental study of metamorphic reactions, properties of metamorphic minerals and rocks and the economic aspects of metamorphic terranes.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信