Are zircons forever? On the problem of survival of inherited zircons in juvenile crust and lithospheric mantle

锆石是永恒的吗？

• 批准号: 252610233
• 负责人: Professor Dr. Alfred Kröner (†)
• 金额: --
• 依托单位: Institut für Geowissenschaften
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/252610233?language=en
• 关键词: zircons; forever; problem; survival; inherited

Earth sciences experienced a far-reaching revolution since ion microprobe technology (e.g. SHRIMP) and high-resolution ICP-MS were developed and routine in-situ U-Th-Pb analysis of domains in U-bearing minerals (e.g. zircon) became available. One of the mayor discoveries using SHRIMP was the occasional presence of inherited (xenocrystic) zircons, or cores of zircons, much older than the host rock. Such inherited grains were even found in juvenile igneous rocks generated and emplaced in intra-oceanic environments, far away from any continent. The presence of inherited zircons in these environments challenges our view of mantle geodynamics and suggests the existence of yet unknown recycling processes, possibly even involving the deep mantle. The problem of zircon inheritance is not yet fully understood and has not been seriously addressed despite its considerable implications for crustal evolution and mantle geodynamics. Therefore, resolving the origin and conditions of preservation of exotic zircon in seemingly juvenile, mantle-derived rocks is the target of this project. We will address this long-standing geological problem by taking into consideration various geodynamic settings (e.g., intra-oceanic fore-arc, arc, back-arc, mid-ocean ridge and ocean island) of different ages and by using rock samples from the Caribbean (Cuba and Grenada Islands), Galápagos, and Central Asia (Mongolia and Kyrgyzstan). We follow a novel approach in combining U/Pb age dating, Lu/Hf and O-isotopes in zircons, Re/Os isotopes in mantle-derived sulfides as well as chemical analyses (e.g. element/isotope distribution in zircons using SHRIMP II, LA/ICP/MS and EPMA) and the study of the chemical composition of mineral inclusions in zircon. The Hf and O isotope information will be obtained on SHRIMP-dated zircon grains. Whole rock geochemistry (major and trace elements) and mineral analysis will be routinely performed on rock samples from which the zircons are dated. We shall also study the detrital zircon population of intra-oceanic arc sediments from Cuba and Central Asia in order to compare the provenance ages with the age of inherited grains. These analytical methods will be complemented by experiments using piston cylinder and multi-anvil presses at Mainz and Frankfurt Universities, respectively. The Pb-diffusivity in reidite (high-pressure ZrSiO4 polymorph) will be investigated for the first time. The project will demonstrate how advanced small-domain geochronology, geochemistry and experimental petrology can be used to understand crust formation and evolution and mass-recycling at active plate margins.

自从离子微探针技术（如SHRIMP）和高分辨率ICP-MS的发展以及对含铀矿物（如锆石）中的畴进行常规原位U-Th-Pb分析以来，地球科学经历了一场意义深远的革命。使用SHRIMP的主要发现之一是偶尔存在比寄主岩石古老得多的继承（捕虏晶）锆石或锆石核。甚至在远离任何大陆的洋内环境中生成和侵位的年轻火成岩中也发现了这种遗传颗粒。在这些环境中继承锆石的存在挑战了我们对地幔地球动力学的看法，并表明存在未知的再循环过程，甚至可能涉及深部地幔。锆石的继承性问题还没有得到充分的理解，并没有得到认真的处理，尽管它对地壳演化和地幔地球动力学有相当大的影响。因此，解决外来锆石的起源和保存条件似乎年轻，幔源岩是这个项目的目标。我们将通过考虑各种地球动力学环境（例如，通过使用来自加勒比海（古巴和格林纳达群岛）、加拉帕戈斯和中亚（蒙古和吉尔吉斯斯坦）的岩石样本，对不同年代的大洋内弧前、弧、弧后、洋中脊和洋岛进行了研究。我们采用了一种新的方法，将U/Pb定年、锆石中的Lu/Hf和O同位素、幔源硫化物中的Re/Os同位素以及化学分析（如利用SHRIMP II、LA/ICP/MS和EPMA研究锆石中的元素/同位素分布）与锆石中矿物包裹体的化学成分相结合。锆石SHRIMP定年的Hf和O同位素信息将被获得。将对确定锆石年代的岩石样品进行全岩地球化学（主要和微量元素）和矿物分析。我们还将研究来自古巴和中亚的洋内弧沉积物中的碎屑锆石群，以便将物源年龄与继承颗粒年龄进行比较。这些分析方法将通过分别在美因茨大学和法兰克福大学使用活塞缸和多砧压力机的实验来补充。铅在reidite（高压ZrSiO 4多晶型）的扩散率将首次进行调查。该项目将展示如何利用先进的小域地质年代学、地球化学和实验岩石学来了解地壳的形成和演化以及活动板块边缘的物质再循环。

项目成果

Recycling in the subduction factory: Archaean to Permian zircons in the oceanic Cretaceous Caribbean island-arc (Hispaniola)

• DOI: 10.1016/j.gr.2017.09.010
• 发表时间: 2018-02
• 期刊: Gondwana Research
• 影响因子: 6.1
• 作者: L. Torró;J. Proenza;Y. Rojas‐Agramonte;A. Garcia‐Casco;Jin-Hui Yang;Yue-heng Yang

Recycling and transport of continental material through the mantle wedge above subduction zones: A Caribbean example

• DOI: 10.1016/j.epsl.2015.11.040
• 发表时间: 2016-02
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Y. Rojas‐Agramonte;A. Garcia‐Casco;A. Kemp;A. Kröner;J. Proenza;C. Lázaro;Dunyi Liu

A geotraverse across two paleo-subduction zones in Tien Shan, Tajikistan

• DOI: 10.1016/j.gr.2016.09.010
• 发表时间: 2017-07
• 期刊: Gondwana Research
• 影响因子: 6.1
• 作者: D. Konopelko;R. Seltmann;Yunus Mamadjanov;R. Romer;Y. Rojas‐Agramonte;Y. Rojas‐Agramonte;T. Jeffries;D. Fidaev;A. Niyozov

Detrital-zircon geochronology and provenance of the El Oro Metamorphic Complex, Ecuador: Geodynamic implications for the evolution of the western Gondwana margin

厄瓜多尔埃尔奥罗变质杂岩的碎屑-锆石年代学和物源：对西冈瓦纳边缘演化的地球动力学影响

• DOI: 10.1016/j.jsames.2018.12.010
• 发表时间: 2019
• 期刊: Journal of South American Earth Sciences
• 影响因子: 1.8
• 作者: Rojas-Agramonte;Villagómez-Díaz;Toulkeridis;Mertz-Kraus
• 通讯作者: Mertz-Kraus

Cryptic alkaline magmatism in the oceanic Caribbean arc (Camagüey area, Cuba)

加勒比海弧区的隐秘碱性岩浆作用（古巴卡马圭地区）

• DOI: 10.1016/j.lithos.2020.105736
• 发表时间: 2020
• 期刊: Lithos
• 影响因子: 3.5
• 作者: Torró;Cambeses;Rojas-Agramonte;Butjosa;Iturralde-Vinent;Lázaro;Garcia-Casco
• 通讯作者: Garcia-Casco