Curtis Williams

University of California, Davis | UCD · Department of Earth and Planetary Science

The Sari\c{c}i\c{c}ek howardite meteorite shower consisting of 343 documented stones occurred on 2 September 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sari\c{c}i\c{c}ek experienced a complex cosmic ray exposure history, exposed during ~12-14 Ma in a regolith near the surface of a parent asteroid, and t...

We report results from multi-anvil (MA) and laser-heated diamond anvil cell (LH-DAC) experiments that synthesize high-pressure phases, including bridgmanite, ferropericlase, stishovite, and ultramafic liquid, in the presence of an argon-rich fluid. The goal of the experiments is to constrain the equilibrium distribution of argon in magma ocean envi...

Significance We present a coordinated petrologic, mineral chemistry, and multi-isotopic investigation of individual chondrules to further elucidate the origins and formation histories of planetary materials. We show chondrules from certain meteorites that accreted in the outer Solar System contain an assortment of both inner and outer Solar System...

Earth has had a global magnetic field for at least 3.5 billion years, but if the iron-alloy in the core has high conductivity, it is difficult to explain this duration with energy from cooling and inner-core growth alone. Precipitation of light elements (e.g., magnesium, silicon, and oxygen) from Earth's core is a potential alternative energy sourc...

Calcium-aluminum-rich inclusions (CAIs) are the first solids to form in the early Solar System, and they exhibit nucleosynthetic anomalies in many isotope systems. The overwhelming majority of isotopic data for CAIs is limited to inclusions from the CV chondrite Allende and a few other CV, CO, CM, and ordinary chondrites. It is therefore important...

The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on September 2, 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic‐ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m siz...

Evidence for the capture of nebular gases by planetary interiors would place important constraints on models of planet formation. These constraints include accretion timescales, thermal evolution, volatile compositions and planetary redox states1–7. Retention of nebular gases by planetary interiors also constrains the dynamics of outgassing and vol...

Northwest Africa (NWA) 6704/6693 are medium- to coarse-grained achondrites with unique petrologic and geochemical traits that are distinct from the currently established meteorite groups. Here, we report on the extinct ²⁶Al-²⁶Mg and ⁵³Mn-⁵³Cr systems to establish fine-scale chronology of its formation and Cr and Ti isotopic anomalies to constrain t...

Northwest Africa (NWA) 7325 is an ungrouped achondrite that has recently been recognized as a sample of ancient differentiated crust from either Mercury or a previously unknown asteroid. In this work we augment data from previous investigations on petrography and mineral compositions, mid-IR spectroscopy, and oxygen isotope compositions of NWA 7325...

Detailed petrologic, geochemical and isotopic analyses of a new FUN CAI from the Allende CV3 meteorite (designated CMS-1) indicate that it formed by extensive melting and evaporation of primitive precursor material(s). The precursor material(s) condensed in a ¹⁶O-rich region (δ¹⁷O and δ¹⁸O ∼ -49‰) of the inner solar nebula dominated by gas of solar...

We present the results of laboratory experiments in which a forsterite-rich melt estimated to be a potential precursor of Allende CMS-1 FUN CAI was evaporated into vacuum for different lengths of time at 1900°C. The evaporation of this melt resulted in residues that define trajectories in chemical as well as magnesium, silicon and oxygen isotopic c...

We present here analyses of mass-independent effects in the Ti isotope ratios of 17 coarse-grained (compact Type A and Type B) calcium–aluminum-rich inclusions (CAIs) from the Allende CV3 chondrite utilizing a method developed for rapid measurement of Ti isotopes by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-...

Chemical differences between mid-ocean ridge basalts (MORBs) and ocean island basalts (OIBs) provide critical evidence that the Earth's mantle is compositionally heterogeneous. MORBs generally exhibit a relatively low and narrow range of He-3/He-4 ratios on a global scale, whereas OIBs display larger variability in both time and space. The primordi...

Supplementary Figures 1-3

We report Cr and Ti isotopic data for Allende CAIs and discuss the variability of Cr and Ti anomalies in the context of understanding r-process nucleosynthesis.

Introduction: Calcium-Aluminum-rich Inclusions (CAIs) are isotopically distinct from the rest of the Solar System for a large number of elements (e.g. [1], refs therein). This difference in isotopic character has been attributed largely to incomplete homogenization of nucleosynthetic anomalies in the nebular reservoir sampled by CAIs. Zirconium has...

Seismic tomography reveals the presence of two large, low shear velocity provinces (LLSVPs) in the lowermost mantle beneath Africa and the Pacific. Additional seismic studies provide evidence that these regions are compositionally-distinct from the surrounding, background mantle. The LLSVPs are hypothesized to be caused by ancient, more-primitive r...

In situ Mg-isotopic data for CMS-1 are reported along with a new set of vacuum experiments that were performed on its estimated precursor composition.

Results on vacuum evaporation experiments of Mg- and Si-rich CMAS melts are used to discuss evolution of chemical and isotopic compositions of FUN CAIs.

We report rare earth element abundances in the primary phases of Allende FUN CAI CMS-1. Implications are presented for the condensation of CMS-1 precursor material as well as fO2 conditions during subsequent melting of this material.

Recently, we reported on the Ti-, Si-, and Mg-isotopic compositions of a new FUN CAI, CMS-1. Here, we report on the O-isotopic composition of its primary phases.

The noble gas systematics observed in ocean island basalts (OIBs) relative to mid-ocean ridge basalts (MORBs), suggests OIBs preferentially sample a primordial reservoir located somewhere within Earth’s mantle. The lower mantle has been favored as a candidate reservoir, either in its entirety or discrete reservoirs located within it. Thermal plumes...

FUN CAIs preserve large isotopic anomalies in several neutron-rich isotopes including 50Ti, as well as extreme mass-dependent fractionations in Mg and Si. We report on the Ti, Si and Mg isotopic compositions of a new Allende FUN CAI designated CMS-1.

We report on the in situ measurement of titanium isotope ratios by LA-MC-ICPMS in nine Allende CAIs. Matrix-matched glass standards were synthesized and used for the correction of matrix-effects and isobaric interferences.

We have measured the Li isotopic composition in terrestrial pyroxene megacrysts by SIMS and MC-ICPMS to assess the role of matrix effects and their potential influence on the analysis of martian pyroxenes.

Os isotope ratios in pyrrhotite-bearing pelitic rocks of the ∼1.85 Ga Virginia Formation are variable, with perturbations linked to the emplacement of the ∼1.1 Ga Duluth Complex. Pyrrhotite in footwall rocks of the contact aureole show evidence for a mixing event at 1.1 Ga involving a low 187Os/188Os fluid. However, because rocks with perturbed pyr...

We report here Li, B and Be distributions in pyroxenes of three shergottites (Shergotty and Zagami, and SaU 005) and the nakhlite Yamato 000593 to assess the role of magmatic degassing, igneous fractionation and subsolidus diffusion processes in their petrogenesis.