Nicole Lunning | Smithsonian Institution (original) (raw)

Papers by Nicole Lunning

The Dominion Range 2010 howardite pairing group contains an evolved lithic clast of dacite compos... more The Dominion Range 2010 howardite pairing group contains an evolved lithic clast of dacite composition. The dacite contains an assemblage of plagioclase, quartz, and augite, with minor pigeonite, troilite, ilmenite, FeNi metal, K-feldspar, and phosphates. Primary augite occurs as >1 mm oikocrysts enclosing plagioclase. Quartz is abundant, comprising approximately 30% of the clast. Textural and geochemical characteristics support the hypothesis that the dacite is a primary igneous lithology, and represents a partial melt of the eucritic crust. Numerical modeling (MELTS) suggests 10–20% partial melting of a Juvinas source could have produced the dacite lithology; quantitative trace element modeling further supports crustal partial melting as the magma source for the dacite. The dacite likely formed as evolved-melt pockets, and thus represents a volumetrically minor lithology in the Vestan crust, although its formation provides direct support for a genetic relationship between Stannern and residual trend eucrites, and is the first identification of residual eucrite complementary melts. We propose the dacite clast is the first characterized sample of tertiary crust on Vesta.

The meteorites Graves Nunataks (GRA) 06128 and 06129 are igneous meteorites dominated by oligocla... more The meteorites Graves Nunataks (GRA) 06128 and 06129 are igneous meteorites dominated by oligoclase feldspar and have basaltic trachyandesite-like whole rock compositions. Formation of the GRA 06128/9 meteorites as primary melts on an oxidized planetesimal has been previously proposed (Day et al. 2009a, 2012a; Gardner-Vandy et al., 2013; Wang et al., 2014). We show experimentally that anhydrous partial melting of an oxidized R chondrite at IW to IW+1 between 1120– 1140 °C produces melts of GRA 06128/9-like compositions: intermediate SiO 2 and FeO concentrations that are enriched in volatile sodium. From a process perspective, GRA 06128/9-like magmas are complementary to partial melt residues such as olivine-rich brachinite and FeO-rich brachinite-like meteorites. Magmas of GRA 06128/9's composition can be generated under equilibrium conditions, as demonstrated by MELTS modeling, but only at temperatures 1140 °C. At lower degrees of partial melting liquids formed under equilibrium and non-equilibrium conditions follow distinct compositional pathways to reach GRA 06128/9-like melts. For lower degrees of melting, the non-equilibrium trend more closely resembles GRA 06128/9's composition. Phase abundance modeling indicates that GRA 06128/9-composition magmas form by 14–22% sili-cate melting of an oxidized R-chondrite. We conclude that GRA 06128/9-composition magmas can be generated at 1140 °C from partial melting of an oxidized chondritic precursor under both non-equilibrium and equilibrium conditions.

Abstract: This study investigates the roles of wind erosion and oxidation in the destruction of h... more Abstract: This study investigates the roles of wind erosion and oxidation in the destruction of histosols in the Sacramento-San Joaquin Delta. In this and analogous areas, elevation loss is commonly attributed to microbial oxidation of organic material; while wind erosion is ...

ABSTRACT Surface elevations of organic soils in peatlands in the Sacramento-San Joaquin Delta, Ca... more ABSTRACT Surface elevations of organic soils in peatlands in the Sacramento-San Joaquin Delta, California, have dropped by as much as fifteen meters since they were drained for agricultural use in the late 19th and early 20th centuries. In this and analogous areas, peat loss is commonly attributed to microbial oxidation of the organic material; while wind erosion is generally considered to be a minor factor. However, in the soil science literature it is widely accepted that organic soils are highly susceptible to wind erosion. The goal of this study is to investigate the competing roles of wind erosion and oxidation in the loss of peat in the Sacramento-San Joaquin Delta by using natural phytoliths found in these peat soils. Phytoliths are biogenic opal; unlike organic matter they are not removed by oxidation. Because of their size, mostly between 2-50 microns, phytoliths are very susceptible to aeolian removal and hence are potentially a good proxy for wind erosion. In this study we sampled peat from drained farmlands and nearby undrained wetlands of the Sacramento-San Joaquin Delta. Samples were treated using conventional phytolith extraction methods. Phytolith concentrations were determined by adding a known quantity (lycopodium spore tablet) of tracer to the phytolith extract (coarse silt fraction >20 microns) and counting the tracer along with the phytoliths. Compared to the phytolith concentrations in undrained peat, the phytolith concentrations should substantially increase in the drained soils as the organic matter oxidizes, unless wind is also eroding the peat. Preliminary results demonstrate an increase in phytolith concentrations for the portion of soil profile (top 45 cm) that has been mixed by agricultural equipment of the drained peat (mean=3.6x104 phytoliths/cm3) compared to the undrained wetland peat (mean=2.3x104 phytoliths/cm3.) However, this higher phytolith concentration in the drained peat is well below the expected phytolith concentration (3.4x105 phytoliths/cm3) if there had been no removal of phytoliths, suggesting that wind erosion is a contributor to the degradation of peat drained for farming.

2 Smithsonian Institution, NMNH, Washington, DC 20560, USA.

ABSTRACT Meteorites of the proposed MIL pairing group share major petrographic features, major-ph... more ABSTRACT Meteorites of the proposed MIL pairing group share major petrographic features, major-phase abundances, and mineral chemistries with one another, and differ individually and collectively from all other presently known nakhlites.

Introduction: Some meteorites sample separate portions of differentiated asteroids: iron meteorit... more Introduction: Some meteorites sample separate portions of differentiated asteroids: iron meteorites are likely core samples and basaltic achondrites are crustal samples. Even though these meteorites originate from as many as 150 geochemically distinct parent bodies [1], samples that represent the mantles of these differentiated asteroids are notably missing. The only exceptions are the pallasites, which may be mantle-core boundary samples .

There is great interest in restoring wetland habitat in the Sacramento-San Joaquin Delta of Calif... more There is great interest in restoring wetland habitat in the Sacramento-San Joaquin Delta of California in order to improve the status of sensitive species as well as to mitigate land-surface subsidence on historically farmed islands. Little is known about the rates of vertical peat accretion throughout the history of the Delta. This type of knowledge is critical for designing successful

2 Smithsonian Institution, NMNH, Washington, DC 20560, USA.