Nick Dygert

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• PhD, Brown University
• Associate Professor at University of Tennessee at Knoxville

Under geologically relevant conditions, Eu is a multivalent element, exhibiting divalent character in reduced systems and trivalent character in oxidized systems. Its mineral-melt and mineral-mineral partitioning behavior is sensitive to oxygen fugacity (fO2) and can be leveraged in oxybarometers that recover fO2s from natural samples if the partit...

Hybridization of the lunar mantle during the overturn (sinking) of Fe- and Ti–rich ilmenite-bearing clinopyroxenite cumulates (IBC) in the lunar interior is called upon to explain the high TiO2 abundances of lunar basalts. Chemical reactions that occur after juxtaposition of IBC and mantle peridotite are poorly constrained. We experimentally invest...

To gain insights into the composition and heterogeneity of Earth's interior, the partial pressure of oxygen (oxygen fugacity, or fO2) in igneous rocks is characterized. A surprising observation is that relative to reference buffers, fO2s of mantle melts (mid-ocean ridge basalts, or MORBs) and their presumed mantle sources (abyssal peridotites) diff...

Apatite, as an accessory phase in igneous and metamorphic rocks, has important petrological significance due to its capacity to accommodate appreciable amounts of many trace elements in its mineral structure. To better constrain trace element partitioning between apatite and silicate melts, we conducted experiments that produced apatites approachin...

Mercury has a compositionally diverse surface exhibiting geochemical terranes that represent different periods of igneous activity, suggesting diverse mantle source compositions. Mercury's juvenile mantle likely formed after fractional solidification of a magma ocean, which produced distinct mineralogical horizons with depth. To produce the diversi...

To investigate the role of Plag floatation efficiency on the formation of depleted Eu/Eu* signatures in lunar mantle sources, we model the fractionation of Eu in LMO mantle cumulates assuming different Plag floatation efficiencies. To calculate Eu fractionation during LMO solidification and subsequent melting, we develop new fO2-dependent Eu partit...

We report new measurements of trace element abundances within opx, cpx, and plag in six aubrites. We evaluate whether mineral grains are homogeneous and if paired phases equilibrated and have the potential to provide meaningful constraints on thermal histories.

Silicate liquid immiscibility (SLI) is a potential consequence of fractional crystallization of the lunar magma ocean (LMO). According to experimental work it may occur after ~97% LMO solidification. This abstract evaluates trace element and Sm-Nd and Lu-Hf isotope fractionation in a solidifying LMO, and residual magma ocean liquids and immiscible...

We present a model for the thermal evolution of asteroids that experience catastrophic fragmentation and reassembly into a gravitational aggregate. The three stage model comprises the initial radiogenic heating, fragmentation and cooling, and reassembly into a porous gravitational aggregate. The heat loss during catastrophic fragmentation is largel...

Apatite is an accessory mineral that is unique for its capacity to accommodate large amounts of trace elements, e.g., rare earth elements (REEs), and apatite-melt partition coefficients have been experimentally determined. However, because of the strong dependence of the valence state of middle REE Eu on oxygen fugacity (fO2), the partition coeffic...

The concentrations and distribution of heat producing elements (HPEs) (K, U, and Th) within planetary interiors determine thermal evolution. Previous studies conclude that the Moon is K depleted and U and Th enriched relative to chondritic meteorites; however, to our knowledge, estimated abundances of HPEs have not been tested in the context of rec...

Mantle peridotites are sampled at ophiolites with supra subduction zone and mid-ocean ridge type tectonic affinities, amagmatic mid-ocean ridge spreading centers, and more rarely, from anomalous exposures at mid-ocean ridge spreading centers with igneous crustal sections, e.g., Hess Deep. Here we assess similarities and differences in the thermal h...

Introduction: Primitive achondrites of the acapulcoite-lodranite clan (ALC) are residues of partial-melting that display a continuum of thermal metamorphism and partial-melting most likely set by burial depth within an internally-heated, primordial acapulcoite-lodranite parent body (ALPB). New major and trace element data from ALCs and the applicat...

Introduction: Apatite [Ca5(PO4)3(OH, F, Cl)] is an omnipresent accessory mineral in different kinds of rocks on Earth as well as other bodies in the Solar System [e.g., 1]. This work presents results of new apatite-melt partitioning experiments relevant to the lunar magma ocean (LMO), and a novel predictive model for apatite-melt trace element part...

Introduction: Cumulate mantle overturn is hypothesized to be a consequence of lunar magma ocean (LMO) solidification, where dense late stage cumulates composed of ilmenite (Ilm) and clinopyroxene (Cpx) sink into less dense underlying cumulates in Rayleigh-Taylor instabilities [1-5]. As the sinking Ilm and Cpx experience adiabatic compression, inter...

Introduction: Ilmenite-bearing cumulates (IBC) are thought to precipitate from a lunar magma ocean (LMO) after ~90%-98% solidification [1, 2]. IBC contain silicates (Cpx and plagioclase) and Fe-Ti oxides (e.g., ulvöspinel and ilmenite), giving them high density with respect to underlying cumulates. This gravitationally unstable density stratificati...

Introduction: Enstatite chondrites (ECs) and aubrites experienced thermal metamorphism and possible fragmentation and reassembly of their parent bodies [e.g. 1,2]. ECs and aubrites (enstatite achondrites) are highly reduced, sulfur-rich meteorites primarily composed of or-thopyroxene (opx), plagioclase (plg), clinopyroxene (cpx), silica polymorphs,...

Plagioclase in lunar anorthositic crust have rare earth element (REE) patterns and Eu abundances which cannot be directly produced by lunar magma ocean (LMO) solidification. This is surprising as the LMO is invoked to explain the mineralogy of the crust, and other lunar surface and interior properties. We explored geological processes subsequent to...

Tuesday, 17 October 2023 4:25 PM - 4:40 PM 326 (3, David L Lawrence Convention Center) Abstract Micah J. Jessup has been an outstanding and highly valued faculty member in the Department of Earth and Planetary Sciences during his 16-year career at the University of Tennessee, Knoxville (UTK). Micah arrived at UTK in 2007 as an assistant professor,...

Primitive achondrites of the acapulcoite–lodranite clan (ALC) are residues of partial melting that displays a continuum of thermal metamorphism and partial melting most likely set by burial depth within an internally heated, primordial acapulcoite–lodranite parent body (ALPB). New major and trace element data from eight ALC meteorites and the appli...

Enstatite‐rich meteorites, including the aubrites, formed under conditions of very low oxygen fugacity (ƒO2: iron‐wüstite buffer −2 to −6) and thus offer the ability to study reduced magmatism present on multiple bodies in our solar system. Elemental partitioning among metals, sulfides, and silicates is poorly constrained at low ƒO2; however, studi...

The transition from the gabbroic oceanic crust to the residual mantle harzburgites of the Oman ophiolite has been drilled at Holes CM1A and CM2B (Wadi Tayin massif) during Phase 2 of the International Continental Scientific Drilling Program Oman Drilling Project (November 2017–January 2018). In order to unravel the formation processes of ultramafic...

Introduction: Silicate inclusions in primitive achondrite winonaites and IAB iron meteorites record a complex history of heating, brecciation, fragmentation, and metamorphism. Stony winonaites and IAB irons are thought to come from the same parent asteroid because of their similar silicate mineralogy, mineral chemistry, and oxygen isotopic composit...

Introduction: Application of REE-in-two-pyroxene thermometry, two-pyroxene solvus thermometry and Ca-in-olivine thermometry to meteorites from H, L, LL chondrite and acapulcoite-lodranite parent bodies reveals fast (~1°C /y) cooling from peak or near-peak temperatures (temperature denoted as T below) [1,2]. Our previous work [1,3] shows that fast c...

Introduction: The classical lunar magma ocean (LMO) hypothesis argues that the lunar anorthosites form from floating LMO crystallized plagioclase [e.g., 1]. To evaluate the formation of the lunar anorthosites in the context of the magma ocean hypothesis, we modeled their Eu and REE contents using experimentally determined LMO solidification sequenc...

Cumulate mantle overturn is hypothesized to be a consequence of lunar magma ocean (LMO) solidification [1-5]. As dense ilmenite (ilm) bearing cumulates (IBC) sink through the lunar mantle and radiogenically heat, they will eventually pass their solidus and begin to melt. Melting the IBC would produce a Ti-rich ferrobasalt that reacts with the surro...

We investigate the rheological and microstructural properties of aggregates of ilmenite and olivine deformed in shear in a Griggs apparatus. The experiments constrain the effective viscosity of an ilmenite-bearing lunar mantle as a function of ilmenite content and shear strain. Ilmenite exhibits viscous anisotropy, deforming by basal slip in shear,...

Recent observations of rapid cooling rates at high temperatures in several ordinary chondrite and primitive achondrite meteorite groups suggest the fragmentation of their parent bodies near peak temperatures. We use analytic models for conductive cooling of collisional fragments to show that the actively cooling part of a fragment experiences simil...

We investigate the cooling histories of peridotites and gabbros from localities that expose oceanic lithosphere formed beneath two fast seafloor spreading centers: Hess Deep as recovered from IODP Expedition 345 and ODP Leg 147, and the Oman Ophiolite as sampled by the Oman Drilling Project, ICDP Expedition 5057 (OmanDP). At these locations, relict...

Over dispersed zircon LA-ICP-MS U-Pb dates in single samples of igneous rock present challenges for age interpretation as the distribution of dates cannot be assumed to represent a single zircon population and formation event. Additionally, assessing the role of lead loss in young zircons is difficult due to the near-linear slope of the 1:1 concord...

The lunar surface is ancient and well-preserved, recording Solar System history and planetary evolution processes. Ancient basin-scale impacts excavated lunar mantle rocks, which are expected to remain present on the surface. Sampling these rocks would provide insight into fundamental planetary processes, including differentiation and magmatic evol...

Mercury has a compositionally diverse surface that was produced by different periods of igneous activity suggesting heterogeneous mantle sources. Understanding the structure of Mercury's mantle formed during the planet's magma ocean stage could help in developing a petrologic model for Mercury, and thus, understanding its dynamic history in the con...

Interactions of hydrous fluids and melts with dry mantle rocks are known to result in metasomatic alteration of the lithospheric mantle. This work investigates such interactions that occurred beneath the Hangay Dome, Mongolia, in 22 mantle xenoliths, which were recovered from Cenozoic basalts at the Tsagan, Zala, Horgo, and Shavaryn-Tsaram localiti...

Introduction: A large body of work has come to the conclusion that ordinary chondrite (H, L, and LL) parent bodies accreted rapidly and then experienced decay heating followed by slow cooling, without further disruption [e.g., 1]. This so-called onion shell model has been challenged by recent geochemical observations showing that these bodies coole...

Introduction: New major and trace element data illuminate the magmatic and thermal evolution of the acapul-coite-lodranite parent body (ALPB). We observe major and trace element disequilibrium in the acapulcoite and transitional groups that provide evidence for melt infiltration and melt-rock reaction processes. In lodranites, which represent sourc...

The viscosity of ilmenite is an important parameter that is thought to have influenced the thermal and chemical evolution of the lunar cumulate mantle. We conduct deformation experiments on two different ilmenite compositions, ilmenite100 (FeTiO3) and ilmenite40 ((Fe0.4Mg0.6)TiO3), to investigate the influence of pressure and Mg‐content on the rheo...

The evolution and compositional structure of the lunar mantle has been extensively modeled but insufficiently constrained by observations. Here, we identify and characterize mantle materials exposed by the Moon's largest impact basin to better understand the composition, stratigraphy, and evolution of the upper mantle. The vast South Pole‐Aitken Ba...

The emplacement and formation of the lower crust at fast-spreading mid-ocean ridges is modeled by two proposed end-member scenarios: the gabbro glacier model, which assumes a mass of crystalline mush in a large crustal magma chamber, or the sheeted sill model, in which crust accretes by solidification of a series of sills continuously emplaced with...

Ordinary chondrites (OCs) are variably thermally metamorphosed meteorites thought to originate from at least three different parent bodies (H, L, and LL) in the Main Belt of asteroids. The thermal evolutions of OC parent bodies are frequently explained by the onion shell model; however, a competing hypothesis is the fragmentation-reassembly model....

Ordinary chondrites (OCs) are variably thermally metamorphosed meteorites thought to originate from three different asteroid parent bodies (H, L, and LL). Their thermal evolutions are frequently explained by the onion shell model; however, a competing hypothesis is the fragmentation-reassembly model. The onion shell model proposes an internally hea...

We report partition coefficients for Sr, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, and Th for plagioclase, pigeonite, and olivine experimentally grown from a lunar basaltic liquid at 1 bar and two different oxygen fugacities (fO2; fayalite-magnetite-quartz (FMQ) and the iron-wüstite (IW) oxygen buffers) at temperatures (Ts) of...

Introduction: Primitive achondrites include several groups of stony meteorites that are residues of low-degrees of partial melting, hence they have experienced higher temperatures (temps) than chondritic meteorites. Cosmochemical, oxygen isotope, and cosmic ray exposure age data for several primitive achondrite groups (and associated silicate-beari...

Geochemical investigation of lithospheric xenoliths to determine thermal or magmatic history of heating in the West Antarctic Rift System.

During the early evolution of the Moon, the lunar mantle is proposed to have undergone an event known as cumulate mantle overturn, where an initially shallow layer of ilmenite sank into an underlying olivine cumulate layer due to a large density and viscosity contrast [1]. It is unclear how the addition of low viscosity ilmenite to the lunar mantle...

Seismic observations show a reduced compressional‐wave velocity gradient at the base of the outer core relative to the preliminary reference Earth model and seismic wave asymmetry between the east‐west hemispheres at the top of the inner core. Here we propose a model for the inner core boundary (ICB), where a slurry layer forms through fractional c...

Ordinary chondrites (OCs) are thought to originate from three different parent bodies (H, L, LL). Their thermal evolutions are typically explained via two competing models; the classic onion shell model or the fragmentation-reassembly model. The onion shell model predicts that OC petrologic types (i.e., 3 to 6) develop with increasing temperature a...

Using the global experimental plagioclase-melt partitioning dataset, new lunar-relevant partitioning experiments and predictive plagioclase-melt partitioning models developed by [1], [2] parameterized an Eu-in-plagioclase-melt oxybarometer for igneous rocks. The oxybarometer successfully reproduces the calibration dataset spanning 15 orders of magn...

The West Antarctic Rift System produced extensive volcanism along the Transantarctic mountain range that delivered crustal and mantle xenoliths to the surface. Previous studies of Antarctic xenoliths largely focused on evaluating major and trace element variations to determine the compositions of mantle reservoirs beneath the rift system, which cou...

Lunar cumulate mantle overturn has been proposed to explain the abundances of TiO2 and heat‐producing elements (U, Th, and K) in the source region of lunar basalts. Ilmenite‐bearing cumulates (IBCs) that were formed near the end of lunar magma ocean solidification are the driving force for overturn. IBCs are enriched with dense TiO2 and FeO content...

Seismic observations show a reduced compressional-wave gradient at the base of the outer core relative to the preliminary reference Earth model and seismic wave asymmetry between the east-west hemispheres at the top of the inner core. Here, we propose a model for the inner core boundary (ICB), where a slurry layer forms through fractional crystalli...

Removal of mantle lithosphere by Rayleigh‐Taylor (R‐T) instabilities is invoked to explain the formation of high plateaus and mountain ranges. Here we report geochemical and microstructural observations from mantle xenoliths from Lunar Crater volcanic field, central Nevada, which we interpret to directly sample a R‐T instability beneath the Basin a...

Cumulate mantle overturn is thought to be a consequence of crystallization of the lunar magma ocean (LMO). In the model, dense ilmenite-bearing cumulates (IBC) that solidified from the last dregs of the of the crystallizing LMO flow into underlying low density early (mafic) magma ocean cumulates as viscous solids [1,2]. The overturn model has been...

We present new measurements of a Mercurian magma ocean analogue and use them to evaluate the efficiency of crystal fractionation from its magma ocean. Our analysis provides insights into Mercury’s dynamic history and the present-day composition of the crust.

Introduction: Thermal evolution models of asteroids are ground-truthed by estimates of temperatures (hereafter temps) and cooling rates from meteorite cosmochemical data [e.g., 1]. However, traditional geothermometers used to constrain the thermal evolution of meteorite parent bodies typically record blocking temps during cooling rather than peak o...

The transition from the crust to the mantle of Oman ophiolite was drilled at Holes CM1A and CM2B (Wadi Tayin Massif) during Phase 2 of the Oman Drilling Project (Nov. 2017-Jan. 2018). The 400m-long Hole CM1A core crosses from the lower crust, through the crust-mantle transition zone, into residual upper mantle peridotites. The 300m-long Hole CM2B c...

We present results of a thermometric investigation of samples from the upper mantle and lower crust at Hess Deep, a rift along the fast-spreading East Pacific Rise (EPR), which place constraints on crustal accretion beneath seafloor spreading centers. We measured major and trace elements in three crustal gabbros (plagioclase (plag) An# 80-85, clino...

The Spongtang ophiolite (Ladakh, NW India) constrains the nature of oceanic lithosphere before Indo-Asia collision and key stages in the development of the Himalayas. We report whole-rock ⁴⁰ Ar/ ³⁹ Ar and in situ zircon ²³⁸ U– ²⁰⁶ Pb ages from its crustal and upper and lower mantle sequences. Major and trace elements from harzburgite minerals sugge...

The ratio of 3He and 22Ne varies throughout the mantle. This observation is surprising because 3He and 22Ne are not produced in the mantle, are highly incompatible during mantle melting, and are not recycled back into the mantle by subduction of oceanic sediment or basaltic crust. Our new compilation yields average 3He/22Ne ratios of 7.5 ± 1.2 and...

Introduction: Models of the thermal evolution of meteorite parent asteroids are predicated on geothermometric estimates of temperatures and cooling rates achieved on those bodies [e.g., 1]. However, geothermometers used to constrain the thermal evolution of asteroids typically record blocking temperatures during cooling rather than peak or magmatic...

Much of the lunar crust is monomineralic, comprising >98% plagioclase. The prevailing model argues the crust accumulated as plagioclase floated to the surface of a solidifying lunar magma ocean (LMO). Whether >98% pure anorthosites can form in a flotation scenario is debated. An important determinant of the efficiency of plagioclase fractionation i...

Lunar cumulate mantle overturn and the subsequent upwelling of overturned mantle cumulates provide a potential framework for understanding the first-order thermochemical evolution of the Moon. Upwelling of ilmenite-bearing cumulates (IBCs) after the overturn has a dominant influence on the dynamics and long-term thermal evolution of the lunar mantl...

The current paradigm argues the Moon formed after a giant impact that produced a deep lunar magma ocean (LMO). After a period of turbulent convection, the LMO experienced fractional crystallization, causing the initially peridotitic liquid to evolve to a plagioclase-saturated ferrobasalt. The lunar crust, much of which comprises 93-98% pure anortho...

Ne are not produced in the mantle or fractionated by partial melting, and neither isotope is recycled back into the mantle by subduction of oceanic basalt or sediment. Thus, it is a surprise that large 3He/22Ne variations exist within the mantle and that the mantle has a net elevated 3He/22Ne ratio compared to volatile-rich planetary precursor mate...

The consequences of hydrous basaltic melts and peridotite interaction were examined experimentally in Au–Pd, Pt, and graphite capsules using the reaction couple method. Reactions between a hydrous basaltic andesite (4 wt% H2O) and dunite or lherzolite in an Au–Pd capsule at 1 GPa and 1200 °C produce a melt-bearing orthopyroxenite–dunite sequence. R...

Tabular dunite bodies are thought to represent remnants of high-porosity pathways for efficient melt extraction from the mantle. They form by melt–rock reaction, an important physical process that affects the compositions of dunite-hosted basaltic melts and the mantle they originate from. To better understand melt–rock interactions in dunite channe...

We present results from new deformation experiments and a dislocation creep flow law for synthetic ilmenite. The flow law predicts an effective viscosity more than three orders of magnitude lower than dry olivine at mantle stresses and temperatures. Using the flow law, we predict that lunar ilmenite-bearing cumulates (IBC) will be weakened by the p...