We report on the discovery of two high-pressure minerals, tuite and ahrensite, located in two small shock-induced melt pockets (SIMP 1 and 2) in the Zagami martian meteorite, coexisting with granular and acicular stishovite and seifertite. Tuite identified in this study has two formation pathways: decomposition of apatite and transformation of merrillite under high-P-T conditions. Chlorine-bearing products, presumably derived from the decomposition of apatite, are concentrated along the grain boundaries of tuite grains. Nanocrystalline ahrensite in the pyroxene clast in SIMP 2 is likely to be a decomposition product of pigeonite under high-P-T conditions by a solid-state transformation mechanism. The pressure and temperature conditions estimated from the high-pressure minerals in the shock-induced melt pockets are ~12–22 GPa and ~1100–1500 °C, respectively, although previous estimates of peak shock pressure are higher. This discrepancy probably represents the shift of kinetic relative to thermodynamic phase boundaries, in particular the comparatively small region that we examine here, rather than a principal disagreement between the peak shock conditions.

中文翻译：

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Zagami中tuite和ahrensite的出现及其对火星陨石冲击史的意义

我们报告了两种高压矿物 tuite 和 ahrensite 的发现，它们位于 Zagami 火星陨石的两个小冲击诱导熔体袋（SIMP 1 和 2）中，与粒状和针状 stishovite 和 seifertite 共存。本研究确定的 Tuite 有两种形成途径：磷灰石的分解和磷灰石在高 PT 条件下的转化。推测来自磷灰石分解的含氯产物沿着tuite晶粒的晶界集中。SIMP 2中辉石碎屑中的纳米晶钙镁石很可能是高PT条件下通过固态转变机制的白鸽石分解产物。从冲击引起的熔体袋中的高压矿物估计的压力和温度条件为~12-22 GPa 和~1100-1500°C，分别，尽管先前对峰值冲击压力的估计更高。这种差异可能代表了动力学相对于热力学相界的变化，特别是我们在这里检查的相对较小的区域，而不是峰值冲击条件之间的主要分歧。