An analysis of differential impact melt‐crater scaling and implications for the terrestrial impact record
An analysis of differential impact melt‐crater scaling and implications for the terrestrial impact record
复制标题
DOI：
10.1111/j.1945-5100.1992.tb01074.x
复制
发表时间：
1992-12
期刊：
影响因子：
--
通讯作者：
R. Grieve;M. Cintala
中科院分区：
文献类型：
--
作者：
R. Grieve;M. Cintala
- 一段时间以来，人们已经知道，冲击熔体的体积（Vm）相对于瞬态空腔的体积（Vtc）随着冲击事件的幅度而增加。本文研究了这种现象对陆地撞击坑性质的影响。撞击熔化的模型被用来估计在15、25和50 km S-1的速度下，撞击花岗岩靶的过程中产生的熔化物的体积。在相同的撞击条件下形成的瞬态空洞的尺寸是根据目前的陨石坑比例关系计算的，这些关系是从陨石坑实验数据的尺寸分析中得出的。在陆地陨石坑观测到的熔体体积从文献中整理，并与各自的陨石坑的瞬时空腔直径（Dtc）配对，这些直径是通过建立经验关系确定的。该模型和观察到的熔体体积有非常相似的趋势，增加瞬态腔直径。这种Vm-Dtc关系，然后用来作出预测的性质的陆地陨石坑记录。特别地，随着撞击事件的大小的增加，熔化的深度接近瞬态空腔的深度。因此，空洞的底部，最终会在一个复杂的陨石坑中作为一个隆起的中心结构出现，将记录冲击应力，该应力将增加到部分熔化的最大值。地面记录的检查表明，在较大直径的中央结构中记录的冲击水平较高的总趋势;在100公里大小范围内的冲击结构记录部分熔融和泡状准原地目标岩在其中心。此外，随着熔化深度接近等于瞬态空洞底部达到的深度，瞬态空洞底部的强度将逐渐降低，结果是空洞修改和隆起将不会产生地形中心峰。同样，所观察到的陆地记录与这一预测并不一致，我们提供了差异熔体缩放作为一种可能的机制，从中央地形峰环的火山口直径增加的过渡。其他影响之一是，早期地球上1000公里大小范围内的撞击盆地可能不具有与月球上观察到的相同的多环形式。
— It has been known for some time that the volume of impact melt (Vm) relative to that of the transient cavity (Vtc) increases with the magnitude of the impact event. This paper investigates the influence that this phenomenon has on the nature of terrestrial impact craters. A model of impact melting is used to estimate the volume of melt produced during the impact of chondritic projectiles into granite targets at velocities of 15, 25, and 50 km S−1. The dimensions of transient cavities formed under the same impact conditions are calculated from current crater-scaling relationships, which are derived from dimensional analysis of data from cratering experiments. Observed melt volumes at terrestrial craters are collated from the literature and are paired with the transient-cavity diameters (Dtc) of their respective craters; these diameters were determined through an established empirical relationship. The model and observed melt volumes have very similar trends with increasing transient-cavity diameter. This Vm-Dtc relationship is then used to make predictions regarding the nature of the terrestrial cratering record. In particular, with increasing size of the impact event, the depth of melting approaches the depth of the transient cavity. As a consequence, the base of the cavity, which ultimately would appear as an uplifted central structure in a complex crater, will record shock stresses that will increase up to a maximum of partial melting. Examination of the terrestrial record indicates a general trend for higher recorded shock levels in central structures at larger diameters; impact structures in the 100-km size range record partially melted and vesiculated parautochthonous target rocks in their centers. In addition, as the depth of melting approaches a depth equivalent to that attained by the base of the transient cavity, the floor of the transient cavity will have progressively less strength, with the result that cavity modification and uplift will not produce topographic central peaks. Again, the observed terrestrial record is not inconsistent with this prediction, and we offer differential melt scaling as a possible mechanism for the transition from central topographic peaks to rings with increasing crater diameter. Among other implications is the likelihood that impact basins in the 1000-km size range on the early Earth would not have the same multi-ring form as observed on the moon.