Abstract There is a lot of debate surrounding the geodynamic environment of the Hadean Earth, and the only definitively known fragments from the first 500 Ma are detrital zircons. This makes the combination of natural and experimentally obtained data a powerful tool to unravel the chemistry of the early Earth. We have used an incompatible marker element, B, to partially derive the chemistry of the parent melts of the Hadean and modern zircons. We report an experimental calibration for temperature dependent B partitioning between zircon and a hydrous weakly peraluminous granitic melt. log 10 D B zrc / melt = − 1027 ± 372 T K − 2.011 ± 0.257 where DBzrc/melt is the zircon-melt partition coefficient for B and T is temperature in K. This calibration has been applied to natural samples, viz., Hadean zircons from the Jack Hills (JH), Australia, Phanerozoic zircons from the Lachlan Fold Belt (LFB), Australia and three pegmatitic zircons from Seiland Igneous province, Norway, Paicoma Canyon, California and Freeman Mine, North Carolina. Our results present direct evidence of B being present in the Hadean crust. The zircons from JH and LFB are rather poor in B (8–80 ppb), but comparable to each other, while the pegmatites have as much as ten times the [B] (~0.35–0.45 ppm). Application of our experimental calibration yields calculated B melt concentrations of 10–90 ppm for the JH and LFB zircons. Such values for melt [B] (concentrations) are similar to the modern upper continental crust (17 ppm) and volcanic arcs, but are high when to compared to OIBs (0.6–1.8 ppm) and MORBs (1.3 ppm). The Lachlan zircons have [B] values that are broadly similar to the detrital Hadean and Archean zircons, and these have been presented as a point of comparison between Hadean and modern zircons. The pegmatite zircons return calculated melt values (244–701 ppm) that are much higher than the parent melts of the Australian zircons. One of the pegmatite zircons show a variation in calculated Ti-in-zircon crystallization T from the core to the rim (716 °C – 916 °C). Two of the other zircons crystallized at 664 ± 14 °C and 598 ± 13 °C (2 s.e.; not taking into consideration a ~50oT uncertainty due to imperfectly constrained silica/titania activities) and show no intracrystalline variation in [B] or T. Finally, B has been proposed to have been a possible stabilizing agent for ribose aqueous solutions and could have played a part in the formation of carbohydrates and proteins which were building blocks for RNA. Our documented presence of B in the Hadean crust at calculated concentrations similar to a modern volcanic arc setting, makes the role of B in ribose stabilization at least possible on the primordial Earth.

中文翻译：

---

锆石和熔体之间的硼分配：深入了解冥河、现代弧和伟晶岩环境

摘要 围绕冥界地球的地球动力学环境存在很多争论，前 500 Ma 唯一确定的碎片是碎屑锆石。这使得自然数据和实验数据的结合成为解开早期地球化学的有力工具。我们使用了不相容的标记元素 B 来部分推导冥河和现代锆石母体熔体的化学成分。我们报告了锆石和含水弱过铝花岗岩熔体之间温度相关 B 分配的实验校准。log 10 DB zrc /melt = − 1027 ± 372 TK − 2.011 ± 0.257 其中 DBzrc/melt 是 B 的锆石-熔体分配系数，T 是以 K 为单位的温度。此校准已应用于天然样品，即冥河锆石来自澳大利亚杰克山 (JH)，来自澳大利亚拉克兰褶皱带 (LFB) 的显生宙锆石和来自挪威塞兰德火成岩省、加利福尼亚州派科马峡谷和北卡罗来纳州弗里曼矿的三块伟晶岩锆石。我们的结果提供了 B 存在于冥界地壳中的直接证据。来自 JH 和 LFB 的锆石的 B 含量相当差（8-80 ppb），但彼此可比，而伟晶岩的含量高达 [B] 的十倍（~0.35-0.45 ppm）。应用我们的实验校准计算得出 JH 和 LFB 锆石的 B 熔体浓度为 10-90 ppm。熔体 [B]（浓度）的这些值类似于现代上大陆地壳 (17 ppm) 和火山弧，但与 OIBs (0.6-1.8 ppm) 和 MORBs (1.3 ppm) 相比较高。Lachlan 锆石的 [B] 值与碎屑 Hadean 和太古代锆石大致相似，这些已被用作冥河和现代锆石之间的比较点。伟晶岩锆石返回的计算熔体值 (244–701 ppm) 远高于澳大利亚锆石的母体熔体。其中一颗伟晶岩锆石显示出从核心到边缘（716 °C – 916 °C）计算的锆石中钛结晶 T 的变化。其他两个锆石在 664 ± 14 °C 和 598 ± 13 °C 结晶（2 秒；未考虑由于二氧化硅/二氧化钛活性受限不完全而导致的~50oT 不确定性），并且在 [B] 或 T 中没有显示晶内变化最后，B 被认为是核糖水溶液的一种可能的稳定剂，并且可能在碳水化合物和蛋白质的形成中发挥了作用，这些碳水化合物和蛋白质是 RNA 的组成部分。