Mineralogy of the Martian interior up to core-mantle boundary pressures
Mineralogy of the Martian interior up to core-mantle boundary pressures
复制标题
DOI：
10.1029/96jb03270
复制
发表时间：
1997-03-10
影响因子：
3.9
通讯作者：
Fei, YW
中科院分区：
文献类型：
--
作者：
Bertka, CM;Fei, YW
为了确定火星内部沿着高温热液的矿物学，多砧实验已经进行了一个模型火星地幔成分高达23.5 GPa。Dreibus和Wanke [1985]的火星地幔成分产生了一个由橄榄石+单斜辉石+斜方辉石+石榴石组成的上地幔，压力高达9 GPa。在9 GPa以上，斜方辉石不再存在。在13.5 GPa时，过渡区出现γ尖晶石。在15 GPa压力下，尖晶石与β相和/或γ尖晶石共存。到17 GPa时，单斜辉石完全被镁铝尖晶石取代，γ尖晶石的模态丰度增加，而β相则减少。在过渡带的大部分地区，主要的组合是伽马尖晶石+镁铝尖晶石。在钙钛矿稳定性场中完成的两个实验表明，下地幔由Mg-Fe硅酸盐钙钛矿、镁橄榄石和镁橄榄石组成。这些实验中不存在CaSiO 3-钙钛矿。火星下地幔的存在，Mg-Fe硅酸盐-钙钛矿型含矿带和稳定于火星下地幔中的相组合对火星内部的温度分布非常敏感。低温分布可以稳定下地幔中的斯铁闪石，或者由于在较低温度下形成钙钛矿所需的较高转变压力，它可能导致下地幔的缺失。无论假设的温度分布如何，火星上地幔和过渡带将占行星内部的更大比例，而不是地球内部的情况，因为火星的尺寸较小。
In order to determine the mineralogy of the Martian interior along a high-temperature areotherm, multianvil experiments have been performed with a model Martian mantle composition up to 23.5 GPa. The Dreibus and Wanke [1985] Martian mantle composition yields an upper mantle that consists of olivine + clinopyroxene + orthopyroxene + garnet at pressures up to 9 GPa. Above 9 GPa, orthopyroxene is no longer present. The transition zone is marked by the appearance of gamma spinel at 13.5 GPa. Up to 15 GPa, ciinopyroxene and majorite coexists with beta phase and/or gamma spinel. By 17 GPa, clinopyroxene is entirely replaced by majorite and the modal abundance of gamma spinel increases at the expense of beta phase. The dominant assemblage throughout most of the transition zone is gamma spinel + majorite. Two experiments completed in the perovskite stability field indicate that the lower mantle consists of Mg-Fe silicate-perovskite, magnesiowustite, and majorite. CaSiO3-perovskite is not present in these experiments. Both the presence of a Martian lower mantle, i.e., an Mg-Fe silicate-perovskite bearing zone, and the phase assemblage stable in the Martian lower mantle are very sensitive to the temperature profile of the interior. A low-temperature profile may stabilize stishovite the lower mantle or it may lead to the absence of the lower mantle because of the higher transition pressure required for forming perovskite at lower temperatures. Regardless of the temperature profile assumed, the Martian upper mantle and transition zone will account for a larger proportion of the planet's interior than is the case for the Earth's interior because of the smaller size of Mars.