The Magmatic Evolution of Planetary Mantles
Planetary mantles make up by far the most massive portions of terrestrial planets. Because of this, their initial states, composition, and dynamic evolution dictate how planets evolve geologically. Although direct access to planetary mantles outside of Earth's through samples and seismology is practically or completely non-existent, the geochemistry of igneous rocks, the products of partial melting of planetary mantles, offers an enormous amount of information about the composition of planetary mantles and how they've evolved over 4.5 billions years.
The LMO and Formation of the Mg-Suite
The Moon is the best sampled planetary body other than Earth. Much of my lunar research is about understanding how the lunar mantle differentiated during the magma ocean phase, how it produced magmas immediately after that differentiation, and what factors contributed to how the Moon's mantle melted late in lunar history. In 2011, I published the first experimental simulation of lunar magma ocean crystallization, with an emphasis on how the composition of the early cumulate pile relates the first post-LMO intrusive magmas of the Mg-suite (pictured below). I proposed a model for these magmas where in the whole-mantle convection thought to occur due to density instabilities in the post-LMO cumulate pile causes hot, deep mantle dunites to rise to the base of the crust, interact with KREEP and crustal anorthosite, and then partially melt to form Mg-suite magmas. With my current NASA Solar System Workings grant, I am further testing these ideas with new experiments designed to understand how KREEP depresses the melting point of these hybrid cumulate packages and could lead to a greater volume of crust building magmas on the Moon's nearside.
The LMO and Formation of the Mg-Suite
The Moon is the best sampled planetary body other than Earth. Much of my lunar research is about understanding how the lunar mantle differentiated during the magma ocean phase, how it produced magmas immediately after that differentiation, and what factors contributed to how the Moon's mantle melted late in lunar history. In 2011, I published the first experimental simulation of lunar magma ocean crystallization, with an emphasis on how the composition of the early cumulate pile relates the first post-LMO intrusive magmas of the Mg-suite (pictured below). I proposed a model for these magmas where in the whole-mantle convection thought to occur due to density instabilities in the post-LMO cumulate pile causes hot, deep mantle dunites to rise to the base of the crust, interact with KREEP and crustal anorthosite, and then partially melt to form Mg-suite magmas. With my current NASA Solar System Workings grant, I am further testing these ideas with new experiments designed to understand how KREEP depresses the melting point of these hybrid cumulate packages and could lead to a greater volume of crust building magmas on the Moon's nearside.
The Lunar Mantle Through Time
The Moon was very geologically active soon after its formation and differentiation, but despite its small size, its mantle continued to partially melt and form magmas for billions of years. Crater counting suggests there are lavas on the Moon's surface as young as 1 billion years. The youngest samples we have from the Moon are three lunar meteorites that are ~3 billion years old and many models suggested that heat-producing KREEP reservoirs in the mantle were needed to create enough heat for partial melting this later in lunar history. In a series of papers, I used the geochemistry and radiogenic isotopic compositions of these meteoritic basalts, combined with high pressure, high temperature experiments to show that KREEP was not responsible for the mantle melting that formed this melts and that the lunar mantle was capable of partially melting late into lunar history.
Volatiles in Planetary Interiors
Magmatic volatiles such as fluorine, chlorine, and water are important during magmatic processes. The can affect the behavior of magmas, but their abundances and isotopic compositions can also record important information about the accretion, differentiation, and magmatic evolution of planets. In work lead by a number of long-term collaborators, we have investigated the volatiles compositions of the mantles and crusts of the Moon and Mars. One of our major findings, using the water contents of apatite in martian meteorites combined with their radiogenic isotopic compositions, is that planetary mantles incorporated and retain water and other volatiles during their high temperature accretion and differentiation.
The Moon was very geologically active soon after its formation and differentiation, but despite its small size, its mantle continued to partially melt and form magmas for billions of years. Crater counting suggests there are lavas on the Moon's surface as young as 1 billion years. The youngest samples we have from the Moon are three lunar meteorites that are ~3 billion years old and many models suggested that heat-producing KREEP reservoirs in the mantle were needed to create enough heat for partial melting this later in lunar history. In a series of papers, I used the geochemistry and radiogenic isotopic compositions of these meteoritic basalts, combined with high pressure, high temperature experiments to show that KREEP was not responsible for the mantle melting that formed this melts and that the lunar mantle was capable of partially melting late into lunar history.
Volatiles in Planetary Interiors
Magmatic volatiles such as fluorine, chlorine, and water are important during magmatic processes. The can affect the behavior of magmas, but their abundances and isotopic compositions can also record important information about the accretion, differentiation, and magmatic evolution of planets. In work lead by a number of long-term collaborators, we have investigated the volatiles compositions of the mantles and crusts of the Moon and Mars. One of our major findings, using the water contents of apatite in martian meteorites combined with their radiogenic isotopic compositions, is that planetary mantles incorporated and retain water and other volatiles during their high temperature accretion and differentiation.
Related Publications
Elardo, S.M. and Shahar, A. (2017) Non-chondritic iron isotope ratios in planetary mantles as a result of core formation. Nature Geoscience. 10, nr. 4, 317 - 321.
Link to Paper
Link to News and Views Article
Link to April Issue Cover Image
Link to Carnegie Press Release
McCubbin, F.M., Boyce, J.W., Srinivasan, P., Santos, A.R., Elardo, S.M., Filiberto, J., Steele, A., and Shearer, C.K. (2016) Heterogeneous distribution of H2O in the martian interior: Implications for the abundance of H2O in depleted and enriched mantle sources. Meteoritics and Planetary Science. 51, Nr.11, 2036-2060.
Link to Paper
Elardo, S.M., Shearer, C.K., Vander Kaaden, K.E., McCubbin, F.M., and Bell, A.S. (2015) Petrogenesis of primitive and evolved basalts in a cooling Moon: Experimental constraints from the youngest known lunar magmas. Earth and Planetary Science Letters 422, 126-137.
Link to Paper
McCubbin, F.M., Vander Kaaden, K.E., Tartèse, R., Klima, R.L., Liu, Y., Mortimer, J., Barnes, J.J., Shearer, C.K., Treiman, A.H., Lawrence, D.J., Elardo, S.M., Hurley, D.M., Boyce, J.W., and Anand, M. (2015) Volatiles (H, C, N, F, S, Cl) in the lunar mantle, crust, and regolith: Distribution, processes, sources, and significance. American Mineralogist 100, 1668-1707. Special Issue: Second Conference on the Lunar Highlands Crust and New Directions.
Invited Review Paper
Link to Paper
McCubbin, F.M., Shearer, C.K., Burger, P.V., Hauri, E.H., Wang, J., Elardo, S.M., and Papike, J.J. (2014) Volatile abundances of coexisting merrillite and apatite in the martian meteorite Shergotty: Implications for merrillite in hydrous magmas. American Mineralogist 99, 1347-1354.
Link to Paper
Link to Highlights and Breakthroughs Article
Tartèse, R., Anand, M., McCubbin, F.M., Elardo, S.M., Shearer, C.K., and Franchi, I.A. (2014) Apatites in lunar KREEP basalts: The missing link to understanding the H isotope systematics of the Moon. Geology 42, no. 4, 363-366.
Link to Paper
Elardo, S.M., Shearer, C.K., Fagan, A.L., Borg, L.E., Gaffney, A.M., Burger, P.V., Neal, C.R., Fernandes, V.A., and McCubbin, F.M. (2014) The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205. Meteoritics & Planetary Science 49, Nr. 2, 261-291.
Link to Paper
McCubbin, F.M., Elardo, S.M., Shearer, C.K., Smirnov, A., Hauri, E. K., and Draper, D. S. (2013) A petrogenetic model for the co-magmatic origin of chassignites and nakhlites: Inferences from chlorine-rich minerals, petrology, and geochemistry. Meteoritics & Planetary Science 48, Nr. 5, 819-853.
Link to Paper
Agee, C.B., Wilson, N.V., McCubbin, F.M., Ziegler, K., Polyak, V.J., Sharp, Z.D., Asmerom, Y., Nunn, M.H., Shaheen, R., Thiemens, M.H., Steele, A., Fogel, M.L., Bowden, R., Glamoclija, M., Zhang, Z., and Elardo, S.M. (2013) Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034. Science 339, 780-785.
Link to Paper
Link to Perspectives Article
McCubbin, F.M., Hauri, E.H., Elardo, S.M., Vander Kaaden, K.E., Wang, J., and Shearer, C.K. (2012) Hydrous melting of the Martian mantle produced both depleted and enriched Shergottites. Geology 40, no. 8, 683-686.
Link to Paper
McCubbin, F.M., Jolliff, B.L., Nekvasil, H., Carpenter, P.K., Zeigler, R.A., Steele, A., Elardo, S.M., and Lindsley, D.H. (2011) Fluorine and chlorine abundances in lunar apatite: Implications for heterogeneous distributions of magmatic volatiles in the lunar interior. Geochimica et Cosmochimica Acta 75, 5073-5093.
Link to Paper
Elardo, S.M., Draper, D.S., and Shearer, C.K. (2011) Lunar Magma Ocean crystallization revisited: Bulk composition, early cumulate mineralogy, and the source regions of the highlands Mg-suite. Geochimica et Cosmochimica Acta 75, 3024-3045.
Link to Paper
Link to Paper
Link to News and Views Article
Link to April Issue Cover Image
Link to Carnegie Press Release
McCubbin, F.M., Boyce, J.W., Srinivasan, P., Santos, A.R., Elardo, S.M., Filiberto, J., Steele, A., and Shearer, C.K. (2016) Heterogeneous distribution of H2O in the martian interior: Implications for the abundance of H2O in depleted and enriched mantle sources. Meteoritics and Planetary Science. 51, Nr.11, 2036-2060.
Link to Paper
Elardo, S.M., Shearer, C.K., Vander Kaaden, K.E., McCubbin, F.M., and Bell, A.S. (2015) Petrogenesis of primitive and evolved basalts in a cooling Moon: Experimental constraints from the youngest known lunar magmas. Earth and Planetary Science Letters 422, 126-137.
Link to Paper
McCubbin, F.M., Vander Kaaden, K.E., Tartèse, R., Klima, R.L., Liu, Y., Mortimer, J., Barnes, J.J., Shearer, C.K., Treiman, A.H., Lawrence, D.J., Elardo, S.M., Hurley, D.M., Boyce, J.W., and Anand, M. (2015) Volatiles (H, C, N, F, S, Cl) in the lunar mantle, crust, and regolith: Distribution, processes, sources, and significance. American Mineralogist 100, 1668-1707. Special Issue: Second Conference on the Lunar Highlands Crust and New Directions.
Invited Review Paper
Link to Paper
McCubbin, F.M., Shearer, C.K., Burger, P.V., Hauri, E.H., Wang, J., Elardo, S.M., and Papike, J.J. (2014) Volatile abundances of coexisting merrillite and apatite in the martian meteorite Shergotty: Implications for merrillite in hydrous magmas. American Mineralogist 99, 1347-1354.
Link to Paper
Link to Highlights and Breakthroughs Article
Tartèse, R., Anand, M., McCubbin, F.M., Elardo, S.M., Shearer, C.K., and Franchi, I.A. (2014) Apatites in lunar KREEP basalts: The missing link to understanding the H isotope systematics of the Moon. Geology 42, no. 4, 363-366.
Link to Paper
Elardo, S.M., Shearer, C.K., Fagan, A.L., Borg, L.E., Gaffney, A.M., Burger, P.V., Neal, C.R., Fernandes, V.A., and McCubbin, F.M. (2014) The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205. Meteoritics & Planetary Science 49, Nr. 2, 261-291.
Link to Paper
McCubbin, F.M., Elardo, S.M., Shearer, C.K., Smirnov, A., Hauri, E. K., and Draper, D. S. (2013) A petrogenetic model for the co-magmatic origin of chassignites and nakhlites: Inferences from chlorine-rich minerals, petrology, and geochemistry. Meteoritics & Planetary Science 48, Nr. 5, 819-853.
Link to Paper
Agee, C.B., Wilson, N.V., McCubbin, F.M., Ziegler, K., Polyak, V.J., Sharp, Z.D., Asmerom, Y., Nunn, M.H., Shaheen, R., Thiemens, M.H., Steele, A., Fogel, M.L., Bowden, R., Glamoclija, M., Zhang, Z., and Elardo, S.M. (2013) Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034. Science 339, 780-785.
Link to Paper
Link to Perspectives Article
McCubbin, F.M., Hauri, E.H., Elardo, S.M., Vander Kaaden, K.E., Wang, J., and Shearer, C.K. (2012) Hydrous melting of the Martian mantle produced both depleted and enriched Shergottites. Geology 40, no. 8, 683-686.
Link to Paper
McCubbin, F.M., Jolliff, B.L., Nekvasil, H., Carpenter, P.K., Zeigler, R.A., Steele, A., Elardo, S.M., and Lindsley, D.H. (2011) Fluorine and chlorine abundances in lunar apatite: Implications for heterogeneous distributions of magmatic volatiles in the lunar interior. Geochimica et Cosmochimica Acta 75, 5073-5093.
Link to Paper
Elardo, S.M., Draper, D.S., and Shearer, C.K. (2011) Lunar Magma Ocean crystallization revisited: Bulk composition, early cumulate mineralogy, and the source regions of the highlands Mg-suite. Geochimica et Cosmochimica Acta 75, 3024-3045.
Link to Paper
Cover photo: A backscattered electron image of an olivine phenocryst with a melt inclusion set in a fine grained groundmass in lunar basaltic meteorite NWA 032.