月球雨海北部陆地区域构造及其含义

月球雨海北部陆地是雨海多环盆地的第二层,平均高程约-1 km。DEM图像显示,大量来自虹湾与柏拉图月坑的掘积物使本地区高程变得非常不均一。统计了研究区内的月坑,并根据其深度与宽度之比(深宽比)将它们划分为4组。深宽比较小而扁率较大的月坑被认为是较古老的月坑。这些古老月坑分布于比较接近月海的位置。对研究区内线性构造的制图研究揭示了3个优选方位,分别是E—W、NEE—SWW和NW—SE向。这种分布样式与月球格子构造系统大致匹配,因而它们很可能形成于雨海事件之前。这些线性构造,包括断裂与月溪,在月海玄武岩泛滥时期为玄武质岩浆的侵入提供了大量通道。在研究区内一些地形较低的地点,玄武岩上侵并出露在月表,它们的FeO平均含量接近但是略低于月海玄武岩。总结了本地区的地质构造演化历史,并且推论月球上的确存在类月海的陆地。

Regional Structure of the Northern Land of the Lunar Mare Imbrium and the Implication

The northern land of the lunar Mare Imbrium is the second mountain ring around the Imbrium multi-ring basin,and the average elevation is about-1 km.Masses of the ejecta from Sinus Iridum and Crater Plato caused severely non-uniform elevation of this area,which is clearly shown by the DEM.The craters located in this area are counted and divided into four groups based on the depth/diameter ratios.The craters with less depth/diameter ratio and larger oblateness are regarded as older craters.The distributions of older craters are more close to the Mare.The mapping of lineaments in this area reveals three preferred orientations,i.e.E-W,NEE-SWW and NW-SE direction.The style of lineament distribution is roughly matched with the Lunar Grid System and likely formed before the Imbrium event.These lineaments,including fractures and rills,had supplied tunnels for the intrusion of basaltic magma during the period of mare basalt flooding.Some intruded basaltic magma extruded onto the surface of this land in several places with lower elevations.The average content of FeO of extruded magma is close to but lower than that of mare basalt.The features of the geological structure and evolution history of this area were summarized,and it could be concluded that there do exist mare-like lands on the Moon.