Planetary evolution: Moon a case study of thermal evolution

• Applicant: Dr. Vera Assis Fernandes, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265560107

Besides the Earth, the Moon provides the most comprehensive global data sets to understand the thermo-chemical evolution of a planetary body. This internal evolution of the Moon is expressed on the lunar surface by widespread basaltic volcanism. Composition and timing of lava emplacement can be determined by measuring mineralogical, chemical and isotopic composition and chronology rock samples. Together with global remote sensing data including images, topographic, spectral, chemical, and gravimetric data, this rock data can be placed into a selenologic context. So far global remote sensing images of the lunar surface suggest a 3.2 Ga lasting period of volcanism, but a significantly shorter period of only 1.8 Ga of volcanic activity was reported by radiometric ages from Apollo, and Luna mission samples and lunar meteorites. In contrast to gram sized Apollo mission samples, the mg sized rake samples from Apollo 15 basaltic regolith, and the Apollo 17 samples studied in the preceding period of this project, provide plenty of basaltic fragments that probably are more diverse and representative for the regional volcanic history. I aim to continue exploring this diversity in Apollo 15 regolith fragments by integrating (1) mineral and chemical composition (SEM, EMPA and LA-ICP-MS) with (2) 40Ar-39Ar chronologic data of the basalt fragments, and 3) in-situ U-Pb when accessory minerals are present. The aim is to evaluate the evolution of the lunar mantle heterogeneities. This integrated multidisciplinary strategy has not been fully explored.The new data obtained from Apollo 15 basaltic fragments, together with the data already acquired from Apollo 17 samples, represent two distinct lunar volcanic provinces, within and outside the Procellarum-KREEP Terrain, respectively. Lunar volcanism in these two distinct settings provides important constraints on the thermo-chemical evolution of the Moon, and the processes that generated these melts. Using the new mineralogical and chemical composition, and chronologic data together with mineral-melt partition coefficients, I aim to determine the thermo-chemical evolution of the mantle under the Imbrium and Serenitatis basins. Presently, the known elemental and isotopic variations of lunar samples cannot be completely modelled with the four distinct mantle reservoirs as sources for low- and high-Ti basalts, KREEEP rocks, and anorthosites. This seems indicative of heterogeneities within the lunar mantle and regional variations in the chemical evolution, and magma generation through time. The results will be used further in global 3D thermo-chemical models computed with the finite difference/finite volume code StagYY to better understand the magmatic evolution of a planet without plate tectonics.

• DFG Programme: Research Grants
• International Connection: China, Sweden, Switzerland, United Kingdom, USA
• Cooperation Partners: Professor Dr. Olivier Bachmann; Professor Dr. Ray Burgess; Dr. Lauren Cooper, Ph.D.; Dr. Marcel Guillong; Dr. Christian Liebske; Professor Dr. Clive Neal; Jakub Sliwinski; Dr. Joshua Snape; Professor Dr. Paul Tackley; Professor Dr. Martin Whitehouse, Ph.D.; Dr. Meng-Hua Zhu, Ph.D.