Anhedral metal grains of >micrometer size occur in many lunar rock types, including mare basalts, magnesian suite rocks (MGS), ferroan anorthosites (FAN), and impact melt rocks and breccias. Some metal grains are inherited from, or modified by, impactors striking the Moon into crustal materials. These grains have high Ni/Co resulting from the addition of chondritic or iron impactors. Metal grains in mare basalts, FAN, and MGS have Ni/Co ranging from >20 to <1, being generally distinct from impactor compositions. Nickel and Co behave as compatible elements in lunar melts, with parental melts having between ~40–50 ppm Co, ~40–60 ppm Ni, and Ni/Co ~1. These compositions suggest a bulk silicate Moon (BSM) with Ni some three times lower than in bulk silicate Earth. Modeling of Ni and Co during fractional crystallization of mafic mare basalt parental melts originating from a BSM source predicts high Ni/Co metals form during early olivine fractionation. The combined effects of pyroxene ± plagioclase crystallization and increasing but variable compatibility of Ni and Co during basaltic melt evolution can explain the generation of low Ni/Co metals in more differentiated mare basalts. High‐Ti mare basalts have metal with low Ni/Co, but the crystallization of ilmenite and armalcoite restricts the range of Ni and Co in metal. Collectively, these results are consistent with metal grains in mare basalts forming solely through endogenous processes. Measurement of metal grains represents a rapid way for determining endogenous (e.g., lunar interior melts) versus exogenous (e.g., impact contamination) processes acting on lunar samples. In turn, the presence of low Ni/Co metal grains in mare basalts supports their origin as uncontaminated partial melts originating from lunar mantle sources that may have experienced loss of Ni to a small lunar core.

中文翻译：

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月球岩石中的金属颗粒可指示火成和撞击过程

微米级以上的反面金属晶粒存在于许多月球岩石类型中，包括母马玄武岩，镁质套房岩石（MGS），铁锰钙铁矿（FAN）以及撞击熔岩和角砾岩。一些金属颗粒是从撞击月球撞击地壳材料的撞击器继承或修改的。这些晶粒由于添加了软骨或铁质撞击物而具有较高的Ni / Co。母玄武岩，FAN和MGS中的金属颗粒的Ni / Co范围> 20至<1，通常与冲击器组成不同。镍和钴在月球熔体中表现为相容元素，母体熔体中Co含量约为40-50 ppm，Ni含量约为40-60 ppm，Ni / Co含量约为1。这些成分表明，镍的体积比硅酸盐大块土低三倍。在源自BSM来源的镁铁质玄武岩母体熔体分步结晶过程中对Ni和Co的建模预测在橄榄石早期分馏过程中会形成高含量的Ni / Co金属。辉石±斜长石结晶和玄武质熔体演化过程中Ni和Co的相容性增加但可变的相容性的共同作用可以解释低分化母马玄武岩中低Ni / Co金属的生成。高钛母马玄武岩的金属中Ni / Co含量低，但是钛铁矿和水辉石的结晶限制了金属中Ni和Co的含量。总体而言，这些结果与仅通过内生过程形成的母马玄武岩中的金属晶粒一致。金属晶粒的测量代表了一种确定内源性（例如月球内部熔体）与外源性（例如月球内部熔体）的快速方法 撞击污染）作用于月球样品的过程。反过来，母马玄武岩中低Ni / Co金属晶粒的存在也支持了它们的起源，因为未污染的部分熔体来自月球地幔源，可能会损失Ni到小的月球核中。