The mineralogy of atmospheric silicate dust controls its interaction with clouds. K-feldspar has a remarkably high ice-nucleating activity, and its distribution may have influenced the global climate throughout Earth's history. However, long-term archives of past atmospheric feldspar are not known. Here, we investigate feldspar mineralogy, content, and grain size in pelagic clay cores. Sediments around Minamitorishima Island contain > 10 wt% of K-feldspar before ~ 35 Ma, which is five times more than the younger sediments. This distribution does not resemble other volcanic minerals or geochemically estimated volcanic input, suggesting that the K-feldspars are not associated with volcanic ash. The K-feldspars are present as isolated grains as well as pseudorhombohedral microcrystals indicative of authigenic overgrowth. On the other hand, they contain some Na, arguing against a purely authigenic origin. Grain size distributions of chemically separated quartz and feldspars show stratigraphic variation analogous to other North Pacific sites, further suggesting a link to eolian materials. Sediments from a South Pacific site also show K-feldspar enrichment over plagioclase before ~ 44 Ma, although the content relative to bulk sediment does not change much. We propose that the K-feldspar may be enriched in the wide area of the Pacific before ~ 30 to 40 Ma.

大气硅酸盐尘埃的矿物学控制其与云的相互作用。钾长石具有非常高的冰核活性，其分布可能影响了整个地球历史上的全球气候。然而，过去大气长石的长期档案尚不清楚。在这里，我们研究了远洋粘土岩心中的长石矿物学、含量和粒度。南鸟岛周围的沉积物在大约 35 Ma 之前含有 > 10 wt% 的钾长石，是较年轻的沉积物的五倍。这种分布与其他火山矿物或地球化学估计的火山输入不同，表明钾长石与火山灰无关。钾长石以孤立颗粒和假菱面体微晶形式存在，表明自生过度生长。另一方面，它们含有一些钠，反对纯粹的自生起源。化学分离的石英和长石的粒度分布显示出与其他北太平洋地点类似的地层变化，进一步表明与风成物质的联系。来自南太平洋地点的沉积物也显示出约 44 Ma 之前钾长石在斜长石上的富集，尽管相对于大量沉积物的含量变化不大。我们认为，钾长石可能在约 30 至 40 Ma 之前在太平洋广大地区富集。来自南太平洋地点的沉积物也显示出约 44 Ma 之前钾长石在斜长石上富集，尽管相对于大量沉积物的含量变化不大。我们认为，钾长石可能在约 30 至 40 Ma 之前在太平洋广大地区富集。来自南太平洋地点的沉积物也显示出约 44 Ma 之前钾长石在斜长石上富集，尽管相对于大量沉积物的含量变化不大。我们认为，钾长石可能在约 30 至 40 Ma 之前在太平洋广大地区富集。