风暴洋晚期玄武岩厚度及规模研究

The Thickness and Scale of Late-stage Basalts in Oceanus Procellarum

风暴洋是月球最大的月海,分布着大面积的晚期(爱拉托逊纪)玄武岩,是研究月球晚期岩浆活动的良好场所.了解月球晚期玄武岩的厚度、体积乃至喷发通量对于了解风暴洋乃至月球晚期的热演化具有重要意义.爱拉托逊纪玄武岩富橄榄石和钛铁矿,其下伏的雨海纪玄武岩富辉石,这两类玄武岩的光谱特征差异十分明显,极易通过高光谱数据进行地层识别.基于月球矿物制图仪(Moon Mineralogy Mapper,M3)数据判断撞击坑是否穿透上覆地层,利用撞击坑挖掘法研究风暴洋爱拉托逊纪玄武岩的厚度,并绘制风暴洋地区晚期玄武岩的高分辨率厚度分布图.结果表明:风暴洋爱拉托逊纪玄武岩的平均厚度约为(24±2)–(88±2)m,最大厚度出现在阿利斯塔克坑(Aristarchus)西部,大多超过60 m,最小厚度值分布于研究区最南部,厚度约为28–31 m.嫦娥五号预定着陆区(吕姆克山,Mons Rumker)附近的厚度约为31–38 m.马里厄斯坑(Marius)以东的区域厚度约为35–45 m,远小于Weider等人所估测的100–300 m.风暴洋地区暴露的爱拉托逊纪玄武岩总体积约为1.39×10~4km3,仅占风暴洋地区玄武岩总体积的1.6%,表明爱拉托逊纪玄武岩浆活动较之雨海纪已极大减弱.

Oceanus Procellarum, the largest lunar mare, distributes large areas of Eratosthenian basalts. Research on the thickness, volume, and eruption flux of the late-stage basalts is essential for understanding the late thermal evolution of Oceanus Procellarum, even the Moon. The Eratosthenian basalts are rich in olivine and ilmenite, while the underlying Imbrian basalts are rich in pyroxene. Their significant spectral differences are easy to be distinguished using the hyperspectral data. We determined whether the crater has penetrated the overlying basalts layer by the Moon MinerMogy Mapper （M3） data, and estimated the thickness of Eratosthenian basalts in the Oceanus Procellarum using a crater excavation technique. A high-resolution thickness distribu- tion map of the last-stage basalts within the Oceanus Procellarum has been acquired. The results show that the average thickness of Eratosthenian basalts in the Oceanus Procellarum varies from -（24±2） m to -（88±2） m. Among them, the thickness of Eratosthenian basalts in the western Aristarchus is the greatest （〉 60 m）, whereas the southernmost study area has a minimum thickness of about 28-31 m. The basalt thickness at the Chang＇E-5 potential landing site is about 31-38 m. The thickness of Eratosthenian basalts in the eastern Marius is -35 to 45 m, which is much smaller than that of 100 to 300 m estimated by Weider et al. The total volume of Eratosthenian basalts is estimated to be -1.39 × 10^4 km3, which is only about 1.6% of all basalts in Oceanus Procellarum. This indicates that the magmatism in Eratosthenian period has been greatly weakened compared to the Imbrian period.