Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92093, USA.
Department of Natural History, Royal Ontario Museum, Toronto, ON, M5S 2C6, Canada.
Nat Commun. 2018 Nov 15;9(1):4799. doi: 10.1038/s41467-018-07191-0.
Direct analysis of the composition of Mars is possible through delivery of meteorites to Earth. Martian meteorites include ∼165 to 2400 Ma shergottites, originating from depleted to enriched mantle sources, and ∼1340 Ma nakhlites and chassignites, formed by low degree partial melting of a depleted mantle source. To date, no unified model has been proposed to explain the petrogenesis of these distinct rock types, despite their importance for understanding the formation and evolution of Mars. Here we report a coherent geochemical dataset for shergottites, nakhlites and chassignites revealing fundamental differences in sources. Shergottites have lower Nb/Y at a given Zr/Y than nakhlites or chassignites, a relationship nearly identical to terrestrial Hawaiian main shield and rejuvenated volcanism. Nakhlite and chassignite compositions are consistent with melting of hydrated and metasomatized depleted mantle lithosphere, whereas shergottite melts originate from deep mantle sources. Generation of martian magmas can be explained by temporally distinct melting episodes within and below dynamically supported and variably metasomatized lithosphere, by long-lived, static mantle plumes.
通过将陨石送到地球，就可以直接分析火星的组成。火星陨石包括源自贫化至富集地幔源区的约 165 至 2400 百万年的辉玻陨石，以及由贫化地幔源区低度部分熔融形成的约 1340 百万年的辉橄无球粒陨石和纯橄无球粒陨石。尽管这些陨石对理解火星的形成和演化具有重要意义，但迄今为止，尚未提出一个统一的模型来解释这些不同岩石类型的成因。本文报道了辉玻陨石、辉橄无球粒陨石和纯橄无球粒陨石的一套连贯的地球化学数据集，这些数据集揭示了它们在源区方面的根本差异。与辉橄无球粒陨石或纯橄无球粒陨石相比，辉玻陨石在给定的 Zr/Y 比值下具有更低的 Nb/Y，这一关系与地球上的夏威夷主盾和再生火山作用几乎相同。辉橄无球粒陨石和纯橄无球粒陨石的组成与水合和交代的贫化地幔岩石圈的熔融一致，而辉玻陨石熔体则源自深部地幔源区。火星岩浆的产生可以通过动态支撑且具有不同程度交代作用的岩石圈内部和下方、具有长期存在的静态地幔羽流的、时间上不同的熔融事件来解释。
