A novel way to investigate the petrogenesis of ancient polymetamorphosed terranes is to study zircon‐hosted mineral inclusions, which are sensitive to melt evolution such as apatite. Recent contributions on such inclusions in unmetamorphosed granitoids can provide valuable petrogenetic information and, in turn, represent a way to circumvent effects of metamorphism. Yet the impact of metamorphism on apatite inclusion has never been studied in detail. To address the issue of chemical and isotopic preservation of primary signals in apatite crystals both in the matrix and armored within zircons, we have studied apatite crystals from four 3.6–4.0 Ga TTG granitoids from the Acasta Gneiss Complex (Canada). Our results demonstrate that U‐Th‐Pb isotope systematics in matrix apatite crystals were reset at 1.8–1.7 Ga (Wopmay orogen) whereas primary REE signatures were preserved in many crystals. In contrast, zircon‐hosted apatite inclusions all preserved primary REE signatures despite variable ages between 1.7 and 4.0 Ga. We interpret reset ages to be a consequence of metamorphism that managed to affect U‐Th‐Pb systematics because of advanced radiation damage accumulation in host‐zircon lattices. Only the most pristine zircon crystal has an apatite inclusion with a concordant age consistent with the magmatic age of the zircon (4.0 Ga). In addition, our results show that apatite crystals from TTG have distinct REE composition from post‐Archean granitoids apatites, that is preserved even in some apatites with reset ages. This capacity to retain primary information and discriminate granitoid types makes apatite a very valuable tool for reconstructing the nature and evolution of ancient crustal rocks through the use of detrital minerals.

中文翻译：

---

通过比较Eoarchean Acasta片麻岩复合体（加拿大）中的基质和锆石晶体，了解磷灰石中主要特征的保留

研究古代多变质地层岩石成因的一种新方法是研究锆石包裹的矿物包裹体，这些包裹体对磷灰石等熔体的演化敏感。对未变质的类固醇中此类夹杂物的最新贡献可提供有价值的岩石成因信息，进而代表一种规避变质作用的方法。然而，从未详细研究变质对磷灰石夹杂物的影响。为了解决基体和铠装锆石中磷灰石晶体中主要信号的化学和同位素保存问题，我们研究了来自Acasta Gneiss Complex（加拿大）的四个3.6–4.0 Ga TTG花岗岩中的磷灰石晶体。我们的结果表明，基体磷灰石晶体中的U-Th-Pb同位素系统重置为1.8-1。7 Ga（Wopmay造山带），而主要的REE标记保留在许多晶体中。相比之下，尽管年龄介于1.7和4.0 Ga之间，但锆石包裹的磷灰石包裹体均保留了主要的REE特征。我们将重置年龄解释为由于宿主体内先进的辐射损伤积累而成功影响了U-Th-Pb系统学的变质作用的结果。锆石晶格。只有最原始的锆石晶体才具有磷灰石包裹体，其年龄与锆石的岩浆年龄（4.0 Ga）一致。此外，我们的结果表明，TTG的磷灰石晶体具有与Archean花岗岩后的磷灰石不同的REE组成，即使在某些具有重置年龄的磷灰石中也可以保留。