Borg Lars E, Shearer Charles K, Asmerom Yemane, Papike James J
Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA.
Nature. 2004 Nov 11;432(7014):209-11. doi: 10.1038/nature03070.
Primordial solidification of the Moon (or its uppermost layer) resulted in the formation of a variety of rock types that subsequently melted and mixed to produce the compositional diversity observed in the lunar sample suite. The initial rocks to crystallize from this Moon-wide molten layer (the magma ocean) contained olivine and pyroxene and were compositionally less evolved than the plagioclase-rich rocks that followed. The last stage of crystallization, representing the last few per cent of the magma ocean, produced materials that are strongly enriched in incompatible elements including potassium (K), the rare earth elements (REE) and phosphorus (P)--termed KREEP. The decay of radioactive elements in KREEP, such as uranium and thorium, is generally thought to provide the thermal energy necessary for more recent lunar magmatism. The ages of KREEP-rich samples are, however, confined to the earliest periods of lunar magmatism between 3.8 and 4.6 billion years (Gyr) ago, providing no physical evidence that KREEP is directly involved in more recent lunar magmatism. But here we present evidence that KREEP magmatism extended for an additional 1 Gyr, based on analyses of the youngest dated lunar sample.
月球（或其最上层）的原始固化导致形成了各种岩石类型，这些岩石随后熔化并混合，从而产生了在月球样品组中观察到的成分多样性。从这个覆盖整个月球的熔融层（岩浆海）中结晶出的初始岩石含有橄榄石和辉石，其成分演化程度低于随后形成的富含斜长石的岩石。结晶的最后阶段，代表岩浆海最后百分之几的部分，产生了富含不相容元素的物质，包括钾（K）、稀土元素（REE）和磷（P）——即所谓的钾稀土磷矿（KREEP）。一般认为，钾稀土磷矿中放射性元素（如铀和钍）的衰变提供了近期月球岩浆活动所需的热能。然而，富含钾稀土磷矿的样品的年龄局限于38亿至46亿年前月球岩浆活动的最早时期，没有提供钾稀土磷矿直接参与近期月球岩浆活动的物理证据。但在此我们基于对最年轻的有年代测定的月球样品的分析，提出证据表明钾稀土磷矿岩浆活动又持续了10亿年。
