The research component in this CAREER award will focus on a series of experimental investigations of melt-rock reaction in Earth's heterogeneous upper mantle conditions. Partial melting of the Earth's upper mantle comprising peridotite and recycled crustal lithologies influences the thermal evolution of the planet, geochemical variability of the crust, differentiation of the interior, fluxes of key volatiles to the exosphere, and geophysical properties of the mantle. While isotopic and trace element geochemistry of erupted basalts have long-established the presence of subducted mid-ocean ridge basaltic (MORB) crust and continental sediment at mantle source regions of ocean island basalts (OIB), the identities of plausible lithologic heterogeneities and how such lithologies impart major element signatures on erupted lavas remain unresolved. Experiments thus far have mostly considered direct partial melting of various lithologies and not the reactive processes involving crust-mantle systems that should be ubiquitous in the convecting mantle. This experimental study will explore how subducted crustal lithologies-derived partial melts and peridotite reaction may produce a wide array of magma compositions and hybrid lithologies. These experiments will be conducted with the aid of piston cylinder (PC) and multi anvil (MA) devices, in order to constrain mantle hybridization via (1) MORB-eclogite-derived partial melts and fertile and depleted peridotite reaction, (2) metapelite-derived partial melts and peridotite reaction, and (3) partial melting of end member hybrid lithologies (modally altered peridotite and pyroxenites) produced by MORB/metapelite melt-peridotite interactions. Experiments are expected to span pressures and temperatures over which subducted crusts and sediments are partially molten but peridotite is unmolten. Major element compositions of reacted partial melts and reacted mineral assemblages will be determined as a function of depth, temperature, original crustal melt and peridotite compositions, extent of partial reactive crystallization, and melt-rock ratio. Furthermore, using high precision electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry, fractionation of elements such as first-row transition metals, Gallium, and Germanium will be determined with the goal of using these elements, in conjunction with major element equilibria, to constrain the mineralogic and lithologic heterogeneities of the basalt source regions.
This CAREER project integrates the PI's Earth science research and teaching through a range of educational outreach activities, professional and career developments of students, and contributions to the broad field of earth science research. The proposed experiments will generate key data relevant to a wide range of Earth science disciplines including petrology-geochemistry, mineral physics, geodynamics, and seismology. The outreach activities will include a 10-week summer internship for one local community college student typically from underrepresented and minority groups, each year, in the PI's experimental petrology lab and supporting one high school or middle school teacher every year for a 4-week lesson plans development on solid Earth topics and research experience in the experimental lab. These two outreach activities are in line with the mission of and organized in collaboration with School Science and Technology (SST) Programs of Rice University. In addition, contents and visuals depicting the motivation, concepts, results, and implications of the proposed research will be developed by the PI for the 'Teaching Petrology in the 21st Century' website, an open-access resource widely used by petrology instructors for both undergraduate and graduate curriculum across the globe. The research performed as part of this proposal will facilitate operation of a new MA lab and will thus contribute towards collection of new MA pressure calibration and assembly data to be shared with the COMPRES (Consortium for Materials Properties Research in Earth Sciences). The generated experimental data on crust-mantle hybridization (with or without volatiles) will contribute towards newer generation thermodynamic, mineral physics, and geodynamic models of mantle materials and processes. Finally, with partial support from Rice, it is planned to engage two PhD students and recruit as many as five Rice undergraduates in order to advance their academic journey and educational experiences.
