Electronic Supplementary Materials - Data Tables from Timing of geological events in the lunar highlands recorded in shocked zircon-bearing clasts from Apollo 16

Apollo 16 soil-like regolith breccia 65745,7 contains two zircon-bearing clasts. One of these clasts is a thermally annealed silica-rich rock, which mineralogically has affinities with the High Alkali Suite (Clast 1), and yields zircon dates ranging from 4.08 to 3.38 Ga. The other clast is a KREEP-rich impact melt breccia (Clast 2) and yields zircon dates ranging from 3.97 to 3.91 Ga. The crystalline cores of both grains, which yield dates of <i>ca</i> 3.9 Ga, have undergone shock pressure modification at less than 20 GPa. We interpret that the U-Pb chronometer in these zircon grains has been partially reset by the Imbrium basin-forming event when the clasts were incorporated into the Cayley Plains ejecta blanket deposit. The zircon grains in Clast 1 have been partially decomposed, resulting in a breakdown polymineralic texture, with elevated U, Pb and Th abundances compared with those in the crystalline zircon. These decomposed areas exhibit younger dates around 3.4 Ga, suggesting a secondary high-pressure, high-temperature event, probably caused by an impact in the local Apollo 16 highlands area.

阿波罗16号类土壤角砾岩65745,7含有两块含锆石岩屑。其中一块为经热退火的富硅岩石（岩屑1），矿物学特征与高碱性岩套（High Alkali Suite）具有亲缘性，其锆石定年结果介于40.8亿至33.8亿年。另一块为富KREEP冲击熔融角砾岩（岩屑2），锆石定年结果介于39.7亿至39.1亿年。两块岩屑中锆石颗粒的结晶核定年结果约为39亿年，均经历了低于20吉帕（GPa）的冲击压力改造。我们认为，当这些岩屑被纳入凯伊平原溅射堆积层时，雨海盆地形成事件对这些锆石颗粒中的铀-铅同位素计时体系造成了部分重置。岩屑1中的锆石颗粒发生了部分分解，形成了分解后多矿物结构，其铀、铅及钍丰度相较于结晶态锆石更高。这些发生分解的区域定年结果偏年轻，约为34亿年，暗示曾发生过一次次级高压高温事件，该事件可能由阿波罗16号高地局部区域的一次撞击事件引发。