Apatite trace element and isotope applications to petrogenesis and provenance
Apatite trace element and isotope applications to petrogenesis and provenance
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DOI：
10.2138/am-2017-5744
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发表时间：
2017
影响因子：
3.1
通讯作者：
E. Bruand;M. Fowler;C. Storey;J. Darling
中科院分区：
文献类型：
--
作者：
E. Bruand;M. Fowler;C. Storey;J. Darling
磷灰石是一种很好的岩石形成过程示踪剂，因为它可以包含大量对熔体演化敏感的元素（LREE-MREE, Sr, Pb, Mn，卤素，Nd同位素）。磷灰石中微量元素浓度和同位素比值的最新研究进展为研究岩浆成因和沉积物物源提供了新的工具。近年来的实验工作较好地表征了磷灰石的微量元素分配系数，这些元素分配系数对岩浆成分（如SiO2和铝饱和度指数值）的变化很敏感。花岗岩类中磷灰石的化学成分反映了寄主岩浆的组成，并提供了在整个岩石尺度上看不见的岩石形成过程的信息（混合、原位晶体分馏、交代）。磷灰石中的Nd同位素现在可以用LA-MC-ICP-MS分析，以约束地幔和地壳对所研究岩浆来源的贡献。这些最近的进展突出了利用辅助矿物了解火成岩过程的令人兴奋的新视野。在这篇文章中，我们使用了最近的数据汇编，表明基质中的磷灰石以及锆石和钛矿中的包裹体有助于了解母岩浆的性质和岩石成因。通过对磷灰石和钛矿的原位分析建立微量元素模型，利用适当的划分系数和仔细的成像，可以可靠地估计原始岩浆的组成。这为研究变质作用叠印的岩浆岩石成因提供了一种新的方法。它还为利用碎屑辅助矿物进行沉积物源的新研究提供了理论依据，如果将其应用于太古宙或冥古宙样品，它可能为研究早期地球过程提供一个强有力的新窗口。
Abstract Apatite is an excellent tracer of petrogenetic processes as it can incorporate a large range of elements that are sensitive to melt evolution (LREE-MREE, Sr, Pb, Mn, halogens, Nd isotopes). Recent advances in the understanding of trace element concentrations and isotope ratios in apatite provide a novel tool to investigate magmatic petrogenesis and sediment provenance. Recent experimental work has better characterized trace element partition coefficients for apatite, which are sensitive to changes in magma composition (e.g., SiO2 and the aluminum saturation index value). The chemistry of apatites from granitoids has been suggested to reflect the composition of the host magma and yield information about petrogenetic processes that are invisible at the whole-rock scale (mixing, in situ crystal fractionation, metasomatism). Nd isotopes in apatite can now be analyzed by LA-MC-ICP-MS to constrain mantle and crustal contributions to the source(s) of the studied magma. These recent advances highlight exciting new horizons to understand igneous processes using accessory minerals. In this contribution, we use a compilation of recent data to show that apatite in the matrix and as inclusions within zircon and titanite is useful for providing insights into the nature and petrogenesis of the parental magma.Trace element modeling from in situ analyses of apatite and titanite can reliably estimate the original magma composition, using appropriate partition coefficients and careful imaging. This provides a new way to look at magmatic petrogenesis that have been overprinted by metamorphic processes. It also provides the rationale for new investigations of sedimentary provenance using detrital accessory minerals, and could provide a powerful new window into early Earth processes if applied to Archean or Hadean samples.