We focused on reconciling Mg-suite petrogenesis considering KREEP-poor lunar meteorites (Gross et al., 2020), geochronology/mantle overturn (Borg et al., 2020), & the paucity of olivine-mantle in the remote sensing database (Melosh et al., 2017). https://twitter.com/OMGsuite/status/1303344717846007814

To do this, we modeled the chemistry of liquids generated by melting primary magma ocean cumulates during mantle overturn. We then modeled the crystallization of liquids generated by the melting model to see if we could reproduce the mineralogy of Mg-suite samples. We could.

How is this "new?" Many Mg-suite origin models invoke a troctolitic parent magma. But experiments show that troctolitic parent melts stabilize high-Al pink spinel (PST), which is only found in < 2% of all lunar troctolites (by mass). How then do common lunar troctolites form?

Previous mantle-origin models suffered from not being able to explain the highest Mg#s in lunar troctolites. But the highest Mg#s are reserved to PST; where we find the crystallization of mantle-derived melts reproduce mineralogy of common lunar troctolites

As a consequence, mantle-derived melts capable of reproducing Mg-suite mineralogy do not also reproduce gabbornorites(!), which are commonly tied to Mg-suite. However, this idea is not without precedent, as some very smart women lead research concluding similar in the 1980's.

So if Mg-suite melts are direct products of melting during overturn, why is there not more olivine-rich mantle exposed during basin forming impacts (Melosh et al., 2017)? Well, what if these melts were extracted from the interior akin to lunar picritic glass magmas?

Anyhow, hope this thread of tidbits was a fun lunch read, and do check out the paper for more details. As always, happy to discuss further! Have a wonderful Tuesday my fellow lunatics :)