High-pressure minerals in eucrite suggest a small source crater on Vesta.
High-pressure minerals in eucrite suggest a small source crater on Vesta.
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萤石中的高压矿物表明灶神星上有一个小型源坑
DOI：
10.1038/srep26063
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发表时间：
2016-05-16
影响因子：
4.6
通讯作者：
Yurimoto H
中科院分区：
文献类型：
--
作者：
Pang RL;Zhang AC;Wang SZ;Wang RC;Yurimoto H
陨石中的高压矿物是影响行星和小行星表面的冲击事件的重要记录。在维斯坦表面观察到广泛分布的撞击坑。然而，在Howardite-Eucrite-Diogenite（HED）陨石中发现的高压矿物很少。在这里，我们提出的第一个证据的组织，空位丰富的单斜辉石，和超级石榴石的eucrite西北非洲（NWA）8003。这些高压矿物的存在及其化学成分与柯石英和斯氏石英的组合表明，NWA 8003中熔体脉的凝固开始于>~10 GPa的压力，当压力降至<~8.5 GPa时停止。熔体脉中的冲击温度超过1900 °C。模拟结果表明，产生直径约3公里的撞击坑（不确定性系数为2）的冲击事件与足够高的压力有关，可以解释在NWA 8003中观察到的高压矿物的出现。这表明HED陨石含有类似的高压矿物，应该比以前认为的更频繁地被观察到。
High-pressure minerals in meteorites are important records of shock events that have affected the surfaces of planets and asteroids. A widespread distribution of impact craters has been observed on the Vestan surface. However, very few high-pressure minerals have been discovered in Howardite-Eucrite-Diogenite (HED) meteorites. Here we present the first evidence of tissintite, vacancy-rich clinopyroxene, and super-silicic garnet in the eucrite Northwest Africa (NWA) 8003. Combined with coesite and stishovite, the presence of these high-pressure minerals and their chemical compositions reveal that solidification of melt veins in NWA 8003 began at a pressure of >~10 GPa and ceased when the pressure dropped to <~8.5 GPa. The shock temperature in the melt veins exceeded 1900 °C. Simulation results show that shock events that create impact craters of ~3 km in diameter (subject to a factor of 2 uncertainty) are associated with sufficiently high pressures to account for the occurrence of the high-pressure minerals observed in NWA 8003. This indicates that HED meteorites containing similar high-pressure minerals should be observed more frequently than previously thought.