The lunar magnesian suite, or MG suite, is a group of plutonic igneous rocks thought to represent the first post LMO episode of crust building on the moon. The MG suite is typically characterized by…

This federal contract award is for a grant to Towson University to conduct research on the lunar Mg-suite, a group of plutonic igneous rocks thought to represent the first post-Lunar Magma Ocean episode of crust building on the Moon. The research has three main tasks: 1) determine the global distribution of the Mg-suite through high-temperature petrologic experiments on the effects of KREEP on melting Mg-suite source materials, 2) measure mineral-melt partition coefficients to enable more accurate modeling of Mg-suite petrogenesis, and 3) study the mineralogy, geochemistry, and relationships among the 19 known Mg-suite samples from Apollo 17. The award was made by the National Aeronautics and Space Administration (NASA) under the Solar System Workings program, with a ceiling value of $113,967. The research aims to address key questions about the origin and global distribution of the lunar Mg-suite that remain unresolved. This award does not have a set-aside designation.

The lunar magnesian suite, or MG suite, is a group of plutonic igneous rocks thought to represent the first post LMO episode of crust building on the moon. The MG suite is typically characterized by primitive mineral major element compositions high MG s and evolved trace element compositions high TH, rees. In order to account for these paradoxical major and trace element compositions, the most successful models for its origin require planetary scale processes. Mass contributions from MG rich olivine from the deep mantle, plagioclase from the anorthositic crust, and the kreep reservoir are needed in MG suite source materials. Implicit in these models is a relative age relationship if the MG suite magmas intruded the anorthositic crust, they must be younger. However, recently determined high resolution age dating of MG suite rocks and crustal anorthosites has produced overlapping ages. This finding has been used to question magma ocean models of primary lunar crust formation and the age of the moon. Additionally, the ubiquity of a kreep component in MG suite samples collected in the procellarum kreep terrane PKT by apollo casts doubt on whether the MG suite was a global magmatic event. These observations raise important questions regarding our understanding of lunar geology 1 was MG suite magmatism a global event, or was IT limited to the PKT? 2 how biased is the apollo sample collection and how does IT affect our understanding of the early lunar crust? 3 what is the age relationship between anorthosites and the MG suite? 4 what are the petrologic relationships between MG suite samples? These knowledge gaps will be addressed with three science tasks. Task 1 addresses the global distribution of the MG suite with high temperature petrologic experiments designed to determine the effects of kreep on melting of MG suite source materials. Mixtures of olivine and plagioclase with appropriate compositions will be partially melted in a controlled atmosphere furnace with varying proportions of synthetic kreep. The results will constrain whether the kreep reservoir aides in the production of MG suite magmas and whether we should expect kreep free MG suite rocks in areas of the lunar highlands away from the PKT. In task 2, we will conduct a series of experiments to equilibrate olivine, plagioclase, orthopyroxene, and clinopyroxene with a melt composition similar to MG suite parental magmas. From these experiments, we will measure mineral melt partition coefficients for a suite of trace element directly relevant to MG suite magmas. This will enable more accurate modeling of MG suite petrogenesis and offer better constraints on its formation. Task 3 will focus on determining the geologic relationships among the 19 known MG suite samples from apollo 17. Of all the MG suite samples that currently have very reliable age determinations, all but 1 come from apollo 17. This task will consist of a thorough study of the mineralogy, mineral trace element geochemistry, textural relationships, and minor phase chemistry in the apollo 17 MG suite samples. This task will result in a comprehensive, internally consistent data set that will be used to assess whether inter sample relationships exist among the apollo 17 MG suite samples which may bias our interpretations of their ages and origin. The compositions of parental liquids will be calculated using published mineral melt trace element partitioning parameterizations and the experimentally determined partition coefficients from task 2. The tasks in this proposal are highly relevant to the solar system workings program, specifically the focus on surfaces and interiors. The science questions in the tasks here directly address issues of interior structure, mantle evolution, and volcanism focuses with the solar system workings program.