Oxygen isotopes in titanite and apatite, and their potential for crustal evolution research
Oxygen isotopes in titanite and apatite, and their potential for crustal evolution research
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DOI：
10.1016/j.gca.2019.04.002
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发表时间：
2019-06
影响因子：
5
通讯作者：
E. Bruand;C. Storey;M. Fowler;E. Heilimo;Eimf
中科院分区：
文献类型：
--
作者：
E. Bruand;C. Storey;M. Fowler;E. Heilimo;Eimf
锆石氧同位素分析通常与年代学和Hf同位素分析相结合，是了解大陆地壳演化的关键。在这篇文章中，我们通过证明它们的氧同位素系统是稳健的，并通过开发涉及O同位素和微量元素浓度的地球化学指标来更好地约束岩浆岩石成因，扩大了未勘探的副相（钛矿和磷灰石）的使用。与锆石相比，这些矿物的优势在于它们存在于演化程度较低的岩浆中，对火成岩作用和地壳变质作用更敏感。我们通过地质年代精心挑选的花岗岩类提供了钛矿、磷灰石和锆石的新数据：显生宙高Ba-Sr花岗岩（苏格兰加里东省）、太古代sanukitoids（芬兰卡累利阿省）和新元古代玄武岩-安山岩-英安岩-流纹岩套（BADR；根西岛，海峡岛）。结果表明：(1)所研究的副矿物的δ18O值不受晶体分馏的影响；(2)三种副矿物的δ18O值具有较强的相关性，表明磷灰石和钛矿能够忠实地记录岩浆δ18O；（三）这些副矿物还可以记录花岗岩类同岩浆期至岩浆期后的变质和/或流体循环事件。
Oxygen isotope analysis of zircon, often combined with geochronology and Hf isotope analysis, has been pivotal in understanding the evolution of continental crust. In this contribution, we expand the use of underexplored accessory phases (titanite and apatite) by demonstrating that their oxygen isotope systems can be robust, and by developing geochemical indicators involving O isotopes and trace element concentrations to better constrain magma petrogenesis. These minerals have the advantage over zircon of being present in less evolved magmas and being more responsive to igneous processes and crustal metamorphism. We present new data on titanite, apatite and zircon from carefully-selected granitoids through geological time: the Phanerozoic high Ba-Sr granites (Caledonian province, Scotland), Archean sanukitoids (Karelia province, Finland) and a Neoproterozoic basalt-andesite-dacite-rhyolite suite (BADR; Guernsey, Channel Island). We demonstrate: (i) that δ18O values of the studied accessory minerals are not affected by crystal fractionation, (ii) a strong correlation between δ18O in all three accessory minerals, showing that apatite and titanite can faithfully record the magmatic δ18O; (iii) that these accessory minerals can also record metamorphic and/or fluid circulation events during the syn- to post-magmatic history of granitoids.