Ted Bunch | Northern Arizona University (original) (raw)

Papers by Ted Bunch

In this work we have searched for extraterrestrial (ET) helium (He) in fullerenes isolated from s... more In this work we have searched for extraterrestrial (ET) helium (He) in fullerenes isolated from several K/T boundary (KTB) sediments. Measurements of He in these KTB fullerene residues revealed He-3/He-4 ratios that can only be explained as ET in origin.

The paper describes a method for embedding, sectioning, and observing two types of extraterrestri... more The paper describes a method for embedding, sectioning, and observing two types of extraterrestrial materials, including hydrated interplanetary dust particles (IDPs) and carbonaceous chondrite meteorites. The technique, which produces large thin areas suitable for both high-resolution imaging and thin-film microanalysis, was applied to study the petrology of the IDP Ames-DE C86-11, the Murchison carbonaceous chondrite matrix, and the Allende dark inclusion. The technique makes it possible to maintain delicate interfaces, boundaries, and phase relationships between grains. Because phases are held in place, layer lattice silicates and other minerals with strong preferred orientations can be viewed in any orientation, including the orientation normal to their basal planes.

In addition to endogenic processes such as heating and aqueous activity, meteorite parent bodies ... more In addition to endogenic processes such as heating and aqueous activity, meteorite parent bodies were subjected also to exogenic processing brought about by the impact of the other solar-system objects. Such impacts can produce a variety of effects, ranging from shock metamorphism of individual mineral grains to production of breccias; i.e., rocks consisting of mixtures of disparate lithic units. The present paper reviews recent studies of such breccias, which have generated significant information about the accretional growth of parent bodies, as well as their evolution, composition, stratigraphy, and geological processing.

Meteoritics, 1972

The Seoni (India) chondrite is an H6 group ordinary chondrite that contains olivine (Fa, 19.7 mol... more The Seoni (India) chondrite is an H6 group ordinary chondrite that contains olivine (Fa, 19.7 mole%), orthopyroxene (Fs, 15.9 mole%), clinopyroxene, plagioclase (An, 10.3; Or, 5.6 mole%), together with chromite, troilite, kamacite, taenite, chlorapatite, and whitlockite. Recrystallization has been quite extensive as indicated by the presence of few remnant chondrules, low abundance of clinopyroxene and relatively high abundance of well formed plagioclase. Treatment of Fe2+ and Mg partitioning between clinopyroxene and orthopyroxene and between olivine and chromite indicates equilibration temperatures of between 875–920 °C.

Geochimica et Cosmochimica Acta, 1966

Abstract The material occurring as inclusions and the surrounding metallic matrix of a specimen o... more Abstract The material occurring as inclusions and the surrounding metallic matrix of a specimen of the Campo del Cielo meteorite have been examined in detail. The association of phases and the structure of the metallic portion indicate that the meteorite may be designated as a hexahedrite, or a very coarse octahedrite and that the samples examined had been severely deformed. The particular inclusions examined are composed of silicates associated with a large amount of opaque minerals and are separated from the metallic matrix by a complex interface region. Schreibersite, troilite and graphite are the principal components of the interface region, which contains, in addition, chromite, sphalerite and a calcium-rich phosphate. The texture of the minerals of the interface region indicates nonequilibrium conditions; in particular, an initial heating and then a relatively rapid cooling. Petrographie modal analyses of the silicates indicate an average of 37.9 volume per cent Forsterite, 35.3 vol. per cent chromediopside, 18.4 vol. per cent enstatite and 8.4 vol. per cent oligoclase. A mineral suite so composed is comparable to similar silicate inclusions occurring in predominantly metallic meteorites and also to some terrestrial rocks, but is not comparable to other known silicate meteorite assemblages.

Science, 1965

SOlE NOCE About 15 kilometers south of Gancedo, Chaco Province, in the same general region in whi... more SOlE NOCE About 15 kilometers south of Gancedo, Chaco Province, in the same general region in which these meteorites occur, three shallow depressions were discovered in 1913 by Manuel of Santillan Suairez. These, and a fourth at an unspecified location, were invesina tigated by Natgera in 1923 (8). Naigera believed the depressions to have been dug by Indians, and meteorites found pique in one to have been hidden there by them. Spencer, however, concluded in arth. 1933 that the depressions were meteorite impact craters (9). unch, lilton Argentine-American Expedition The earliest Spanish explorers to enter the region that now is northern Argentina heard marvelous stories from the Indians of a large block of iron that had supposedly fallen from the sky. The place where it lay was called Piguem Nonralta, or, in Spanish, Campo del Cielo (Field of the Sky or Heaven). In 1576 an expedition under Captain Hernain Mexia de Miraval visited the site, returning with a few small pieces of a very large mass, which came to be known as the Meson de Fierro (Large Table of Iron). Suspecting a silver deposit rivaling those of Peru, Bartolome Francisco de Maguna led expeditions to the site in 1774 and 1776. He estimated the Meson de Fierro to weigh about 500 quintales (23 metric tons) and brought back samples, which were found to be iron of extraordinary quality. To determine the workability of the deposit, expeditions were sent to the site in 1779 under Sergeant Major Francisco de Ibarra, and in 1783 under Royal Navy Lieutenant Miguel Rubin de Celis. In

We report abundant nanodiamonds in sediments dating to 12.9 ± 0.1 thousand calendar years before ... more We report abundant nanodiamonds in sediments dating to 12.9 ± 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from 10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.

ABSTRACT Northwest Africa (NWA) 4797 is an ultramafic Martian meteorite composed of olivine (40.3... more ABSTRACT Northwest Africa (NWA) 4797 is an ultramafic Martian meteorite composed of olivine (40.3 vol%), pigeonite (22.2%), augite (11.9%), plagioclase (9.1%), vesicles (1.6%), and a shock vein (10.3%). Minor phases include chromite (3.4%), merrillite (0.8%), and magmatic inclusions (0.4%). Olivine and pyroxene compositions range from Fo66-72,En58-74Fs19-28Wo6-15, and En46-60Fs14-22Wo34-40, respectively. The rock is texturally similar to "lherzolitic" shergottites. The oxygen fugacity was QFM-2.9 near the liquidus, increasing to QFM-1.7 as crystallization proceeded. Shock effects in olivine and pyroxene include strong mosaicism, grain boundary melting, local recrystallization, and pervasive fracturing. Shock heating has completely melted and vesiculated igneous plagioclase, which upon cooling has quench-crystallized plagioclase microlites in glass. A mm-size shock melt vein transects the rock, containing phosphoran olivine (Fo69-79), pyroxene (En44-51Fs14-18Wo30-42), and chromite in a groundmass of alkali-rich glass containing iron sulfide spheres. Trace element analysis reveals that (1) REE in plagioclase and the shock melt vein mimics the whole rock pattern; and (2) the reconstructed NWA 4797 whole rock is slightly enriched in LREE relative to other intermediate ultramafic shergottites, attributable to local mobilization of melt by shock. The shock melt vein represents bulk melting of NWA 4797 injected during pressure release. Calculated oxygen fugacity for NWA 4797 indicates that oxygen fugacity is decoupled from incompatible element concentrations. This is attributed to subsolidus re-equilibration. We propose an alternative nomenclature for "lherzolitic" shergottites that removes genetic connotations. NWA 4797 is classified as an ultramafic poikilitic shergottite with intermediate trace element characteristics.

Iturralde may have formed under natural circumstances unrelated to an impact. However, there is t... more Iturralde may have formed under natural circumstances unrelated to an impact. However, there is the presence of millions of clusters of glass beads in sediment.

Petrology of NWA 2626: A 31.07 gram crusted stone (Figure 1) purchased in Morocco in November 200... more Petrology of NWA 2626: A 31.07 gram crusted stone (Figure 1) purchased in Morocco in November 2004 is an olivine-orthopyroxene-phyric shergottite. Unlike similar specimens we have studied [1], NWA 2626 has cross-cutting glass-rich veinlets and pockets (Figure 2), probably produced by shock during ejection from Mars. Inside a thin weathering rind, the dark greenish specimen is composed of euhedral to subhedral olivine phenocrysts and preferentiallyoriented, prismatic low-Ca pyroxene phenocrysts in a groundmass of zoned pigeonite (Fs 26.4 W o 12.4 to Fs 34.1 Wo 12.4 ), maskelynite (An 66.0-71.0 Or 0.4 ), olivine (Fa 43.6-47.3 ), Ti-chromite (Cr/(Cr+Al) = 0.72-0.79, 9.2-19.8 wt.% TiO 2 ), chromite (Cr/(Cr+Al) = 0.71-0.86, 0.7-2.0 wt.% TiO 2 ), merrillite, ilmenite, ulvöspinel and pyrrhotite. Olivine phenocrysts are zoned from Fa 16.7 cores to Fa 43.3 rims, and pyroxene phenocrysts have irregular cores of orthopyroxene (as magnesian as Fs 17.9 Wo 2.4 , with ~0.03 wt.% TiO 2 and ~0.4 wt.% Al 2 O 3 ) mantled by pigeonite (Fs 25.4 Wo 4.4 to Fs 37.0 W o 12.7 ) with minor subcalcic augite (Fs 21.7-

Proceedings, annual meeting, Electron Microscopy Society of America

Interplanetary Dust Particles (IDPs) are a relatively new class of extraterrestrial materials whi... more Interplanetary Dust Particles (IDPs) are a relatively new class of extraterrestrial materials which are collected by high-flying aircraft in the stratosphere. The particles, ∼1.0-50 μm in size, enter the earth's atmosphere at ballistic velocities, but are sufficiently small to be decelerated without burning up. IDPs commonly have solar elemental abundances, and are thoughfto have undergone very little differentiation since the formation of the solar system. While these materials are called “particles,” they are in fact aggregates of a variety of mineral phases, glass, and carbonaceous material. Grains within IDPs commonly range from a few microns to a few tens of nanometers. The extraterrestrial origin of IDPs has been established by the discovery of solar flare tracks in some mineral grains, and recent D/H isotopic ratios recorded from individual particles. The source and formational history of the particles is a topic of active research. At present, the primary means of screen...

Scientific reports, Jan 30, 2017

Large quantities of impact-related microspherules have been found in fine-grained sediments retai... more Large quantities of impact-related microspherules have been found in fine-grained sediments retained within seven out of nine, radiocarbon-dated, Late Pleistocene mammoth (Mammuthus primigenius) and bison (Bison priscus) skull fragments. The well-preserved fossils were recovered from frozen "muck" deposits (organic-rich silt) exposed within the Fairbanks and Klondike mining districts of Alaska, USA, and the Yukon Territory, Canada. In addition, elevated platinum abundances were found in sediment analysed from three out of four fossil skulls. In view of this new evidence, the mucks and their well-preserved but highly disrupted and damaged vertebrate and botanical remains are reinterpreted in part as blast deposits that resulted from several episodes of airbursts and ground/ice impacts within the northern hemisphere during Late Pleistocene time (~46-11 ka B.P.). Such a scenario might be explained by encounters with cometary debris in Earth-crossing orbits (Taurid Complex) th...

Contributions to Mineralogy and Petrology

Electron microprobe analyses of orthopyroxene and Ca-clinopyroxene in 21 ordinary petrographic ty... more Electron microprobe analyses of orthopyroxene and Ca-clinopyroxene in 21 ordinary petrographic type 6 chondrites (7 H-, 8 L-, and 6 LL-group chondrites) result in differentKD (distribution coefficient) values for H-, L-, and LL-group chondrites, which suggest different equilibration temperatures for each group. If we consider the Blander model (Blander 1972), the differences in Fe-Mg distributions for these groups reflect only

Meteoritics, 1972

Geochimica et Cosmochimica Acta, 1966

Science, 1965

Proceedings, annual meeting, Electron Microscopy Society of America

Scientific reports, Jan 30, 2017

Contributions to Mineralogy and Petrology