标题： 月球岩浆洋固化完成于44.3亿年前 显示英文标题

标题： Completion of Lunar Magma Ocean Solidification at 4.43 Ga

摘要： 月球岩浆洋的结晶产生了一个名为克里普（KREEP）的独特化学残余液体。 这种成分在月球近侧表现为一个大面积区域，在月球远侧南极-艾特肯盆地西北部可能还有一个较小的区域。 热模型估计月球岩浆洋（LMO）的结晶过程可能持续了10到200百万年，而放射性衰变系统的研究表明，LMO结晶完成的时间跨度超过160百万年且结果不一致。 我们发现，月球在距今4429±76百万年时已达到99%以上的结晶度，这意味着月球的形成年龄为4450百万年或更早。 通过使用176Lu-176Hf衰变系统（t1/2=37十亿年），我们发现具有不同U-Pb年龄的月球锆石初始176Hf/177Hf比值与它们从富含克里普的储层中结晶一致，该储层的初始176Lu/177Hf比值一直较低，约为0.0167，并在太阳系形成后约140百万年出现。 先前提出的月海玄武岩源区较年轻的模式年龄4.33Ga（太阳系形成后240百万年）可能反映了大型撞击事件的时间。 我们的研究结果表明，月球岩浆洋的结晶发生在月球仍受到行星胚胎和星子撞击的时候，这些行星胚胎和星子是行星吸积主阶段遗留下来的。 对从南极-艾特肯盆地带回样本的Lu-Hf模式年龄的研究将有助于评估克里普的横向连续性，并进一步理解其在月球早期历史中的意义。 显示英文摘要

摘要： Crystallization of the lunar magma ocean yielded a chemically unique liquid residuum named KREEP. This component is expressed as a large patch on the near side of the Moon, and a possible smaller patch in the northwest portion of the Moon's South Pole-Aitken basin on the far side. Thermal models estimate that the crystallization of the lunar magma ocean (LMO) could have spanned from 10 and 200 Myr, while studies of radioactive decay systems have yielded inconsistent ages for the completion of LMO crystallization covering over 160 Myr. Here, we show that the Moon achieved over 99 percent crystallization at 4429+/-76 Myr, indicating a lunar formation age of 4450 Myr or possibly older. Using the 176Lu-176Hf decay system (t1/2=37 Gyr), we found that the initial 176Hf/177Hf ratios of lunar zircons with varied U-Pb ages are consistent with their crystallization from a KREEP-rich reservoir with a consistently low 176Lu/177Hf ratio of 0.0167 that emerged ~140 Myr after solar system formation. The previously proposed younger model age of 4.33 Ga for the source of mare basalts (240 Myr after solar system formation) might reflect the timing of a large impact. Our results demonstrate that lunar magma ocean crystallization took place while the Moon was still battered by planetary embryos and planetesimals leftover from the main stage of planetary accretion. Study of Lu-Hf model ages for samples brought back from the South Pole-Aitken basin will help to assess the lateral continuity of KREEP and further understand its significance in the early history of the Moon.