Olivine-phyric shergottites represent primitive Martian magmas, but they commonly contain excess olivine and rarely represent primary mantle melts. Olivine chemistry, however, tracks magma evolution and preserves information on the original parent magma composition. Here, we investigate the applicability of the Al-in-olivine thermometer in tandem with olivine chemistry in a suite of 13 olivine-phyric shergottites to constrain the compositions and conditions of their mantle sources and parental magmas. We show that the Al-in-olivine thermometer is a robust method for constraining crystallization temperatures in shergottites, yielding temperatures in agreement with experimental work. In contrast, we do not recommend olivine–spinel thermometry relying on Mg-Fe in olivine, which underestimates crystallization temperatures by 160–380 °C. Olivine chemistry reveals distinct differences in Ni concentrations between shergottite groups, with enriched shergottites generally having higher Ni at a given forsterite (Fo) content. Nickel variations in terrestrial olivine are often accredited to contributions from a pyroxenite source; however, the same mechanism is not responsible for Ni variations in Martian olivine. Here, we favor a model for variable olivine modal abundance, caused by multiple melting episodes in the depleted mantle source, affecting Ni partitioning during melting to account for the Ni variations observed. In addition, we show that olivine Ni-Mn variations in depleted shergottites indicate variable petrogenetic histories and parental magmas. Tissint contains elevated Ni in olivine more similar to the enriched shergottites whereas DaG 1037 has elevated Mn in olivine suggesting an Mn-enriched parent magma relative to other depleted shergottites.

中文翻译：

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橄榄石和橄榄石中铝温度计中的镍锰变异性橄榄石-phyric shergottites

橄榄石-岩浆岩代表原始火星岩浆，但它们通常含有过量的橄榄石，很少代表原始地幔熔体。然而，橄榄石化学追踪岩浆演化并保留原始母岩浆成分的信息。在这里，我们研究了橄榄石中铝温度计与橄榄石化学一起在一组 13 种橄榄石-phyric shergottites 中的适用性，以限制其地幔来源和母岩浆的成分和条件。我们表明，橄榄石中的铝温度计是一种用于限制 Shergottites 结晶温度的稳健方法，其产生的温度与实验工作一致。相比之下，我们不建议依赖橄榄石中的 Mg-Fe 进行橄榄石-尖晶石温度测定，这会低估结晶温度 160-380 °C。橄榄石化学表明，在给定镁橄榄石 (Fo) 含量的情况下，富集的 Shergottite 通常具有更高的 Ni。陆地橄榄石中的镍变体通常被认为是辉石岩来源的贡献；然而，火星橄榄石中镍的变化不是由相同的机制造成的。在这里，我们支持可变橄榄石模态丰度的模型，这是由贫化地幔源中的多次熔化事件引起的，影响熔化过程中的 Ni 分配以解释观察到的 Ni 变化。此外，我们还表明，贫化的 Shergottites 中橄榄石 Ni-Mn 的变化表明了可变的岩石成因历史和母体岩浆。