Nineteen single-grain detrital garnet ages from a tributary to the French Broad River (North Carolina, USA) establish a novel approach to Sm-Nd detrital garnet geochronology wherein the equilibrium bulk-rock composition lost during weathering and transport is replaced with the composition of inclusions leached from within each garnet grain. Detrital garnet ages were compared to published detrital zircon and monazite ages from the same river tributary system. Results show that 87% of the zircons have inherited Proterozoic ages; only zircon rims give Paleozoic ages. Monazites are exclusively Ordovician (weighted average: 460.9 ± 3.0 Ma). Our new detrital garnet ages (and the detrital zircon rims) record younger ages spanning the Late Ordovician to Early Devonian, likely reflecting prolonged metamorphic heating. The weighted average age of the detrital garnet population is Silurian (430.1 ± 7.2 Ma). Statistical tests confirm that the garnet population is younger than the monazite. The new detrital garnet ages illuminate a previously uninterpreted Silurian tectonometamorphic signal in this region.

中文翻译：

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碎屑石榴石年代学：在美国南阿巴拉契亚山脉法国布罗德河支流中的应用

从支流到法国宽河（美国北卡罗来纳州）的19个单粒碎屑石榴石年龄建立了Sm-Nd碎屑石榴石地质年代学的新方法，其中风化和运输过程中失去的平衡块状岩石成分被替换为从每个石榴石颗粒中浸出的夹杂物。将碎屑石榴石年龄与同一河流支流系统中公布的碎屑锆石和独居石年龄进行比较。结果表明，87％的锆石已继承了元古代的年龄。只有锆石轮缘才具有古生代年龄。独居石专门为奥陶纪（加权平均值：460.9±3.0 Ma）。我们新的碎屑石榴石年龄（和碎屑锆石边缘）记录了奥陶纪晚期至泥盆纪早期的更年轻年龄，这可能反映了变质加热时间的延长。碎屑石榴石种群的加权平均年龄是志留纪（430.1±7.2 Ma）。统计测试证实石榴石种群比独居石年轻。新的碎屑石榴石年龄阐明了该地区以前未解释的志留纪构造变态信号。