The composition of the Earth

Knowledge of temperature and pressure, however qualitative, has been central to our views of geology since at least the early 19th century. In 1822, for example, Charles Daubeny presented what may be the very first “Geological Thermometer,” comparing temperatures of various geologic processes (Torrens 2006). Daubeny (1835) may even have been the first to measure the temperature of a lava flow, by laying a thermometer on the top of a flow at Vesuvius—albeit several months following the eruption, after intervening rain (his estimate was 390°F). In any case, pressure ( P ) and temperature ( T ) estimation lie at the heart of fundamental questions: How hot is Earth, and at what rate has the planet cooled. Are volcanoes the products of thermally driven mantle plumes? Where are magmas stored, and how are they transported to the surface—and how do storage and transport relate to plate tectonics? Well-calibrated thermometers and barometers are essential tools if we are to fully appreciate the driving forces and inner workings of volcanic systems.

This chapter presents methods to estimate the P-T conditions of volcanic and other igneous processes. The coverage includes a review of existing geothermometers and geobarometers, and a presentation of approximately 30 new models, including a new plagioclase-liquid hygrometer. Our emphasis is on experimentally calibrated “thermobarometers,” based on analytic expressions using P or T as dependent variables. For numerical reasons (touched on below) such expressions will always provide the most accurate means of P-T estimation, and are also most easily employed. Analytical expressions also allow error to be ascertained; in the absence of estimates of error, P-T estimates are nearly meaningless. This chapter is intended to complement the chapters by Anderson et al. (2008), who cover granitic systems, and by Blundy and Cashman (2008) and Hansteen and Klugel (2008), who consider additional methods …

Thermometers and Barometers for Volcanic Systems

We present new reference values for the NIST SRM 610–617 glasses following ISO guidelines and the International Association of Geoanalysts’ protocol. Uncertainties at the 95% confidence level (CL) have been determined for bulk- and micro-analytical purposes. In contrast to former compilation procedures, this approach delivers data that consider present-day requirements of data quality. New analytical data and the nearly complete data set of the GeoReM database were used for this study. Data quality was checked by the application of the Horwitz function and by a careful investigation of analytical procedures. We have determined quantitatively possible element inhomogeneities using different test portion masses of 1, 0.1 and 0.02 μg. Although avoiding the rim region of the glass wafers, we found moderate inhomogeneities of several chalcophile/siderophile elements and gross inhomogeneities of Ni, Se, Pd and Pt at small test portion masses. The extent of inhomogeneity was included in the determination of uncertainties. While the new reference values agree with the NIST certified values with the one exception of Mn in SRM 610, they typically differ by as much as 10% from the Pearce et al. (1997) values in current use. In a few cases (P, S, Cl, Ta, Re) the discrepancies are even higher.



Nous presentons des nouvelles valeurs de reference pour les verres NIST SRM 610–617 en suivant les recommandations de l’ISO et le protocole de l’IAG. Les incertitudes au niveau de confiance de 95% ont ete determinees a des fins d’analyse totale et de micro-analyse. Contrairement aux procedures de compilation precedentes, cette approche fournit des donnees qui tiennent compte des exigences actuelles dans la qualite des donnees. De nouvelles donnees analytiques et le jeu de donnees presque complet de la base de donnees GeoReM ont ete utilises pour cette etude. La qualite des donnees a ete verifiee par l’application de la fonction de Horwitz et par un examen minutieux des procedures analytiques. Nous avons determine quantitativement les possibles inhomogeneites d’element en utilisant des prises d’essai de masses differentes correspondant a 1, 0.1 et 0.02 μg. Bien que nous ayons evite les zones de bordure des disques de verre, nous avons trouve des inhomogeneites moderees pour plusieurs elements chalcophiles/siderophiles et des inhomogeneites flagrantes de Ni, Se, Pd et Pt pour les prises d’essai de petites masses. La mesure d’inhomogeneite a ete incluse dans la determination des incertitudes. Alors que les nouvelles valeurs de reference sont en accord avec les valeurs NIST certifiees a la seule exception du Mn dans SRM 610, elles sont generalement differentes, avec des ecarts de pres de 10%, des valeurs de Pearce et al. (1997) qui sont d’un usage courant. Dans quelques cas (P, S, Cl, Ta, Re), les ecarts sont encore plus eleves.

Determination of Reference Values for NIST SRM 610–617 Glasses Following ISO Guidelines

Data Reduction And Error Analysis For The Physical Sciences

Calibration of the geological time scale is achieved by independent radioisotopic and astronomical dating, but these techniques yield discrepancies of ∼1.0% or more, limiting our ability to reconstruct Earth history. To overcome this fundamental setback, we compared astronomical and 40 Ar/ 39 Ar ages of tephras in marine deposits in Morocco to calibrate the age of Fish Canyon sanidine, the most widely used standard in 40 Ar/ 39 Ar geochronology. This calibration results in a more precise older age of 28.201 ± 0.046 million years ago (Ma) and reduces the 40 Ar/ 39 Ar method9s absolute uncertainty from ∼2.5 to 0.25%. In addition, this calibration provides tight constraints for the astronomical tuning of pre-Neogene successions, resulting in a mutually consistent age of ∼65.95 Ma for the Cretaceous/Tertiary boundary.

https://science.sciencemag.org/content/sci/320/5875/500.full.pdf

Synchronizing Rock Clocks of Earth History

O and Mn-Cr Isotope Systematics of a Fayalite-Silica Particle from Comet Wild 2

Do Antarctic Meteorite Concentrations Reflect the Average Infall Rate

Overview Most meteorites (~86%) are chondrites, which are primitive rocks that have elemental compositions similar to that of the Sun. They are named for the millimeter-sized droplets of quenched silicate melt, called chondrules, that are particularly abundant in these meteorites. Chondrites come from the asteroid belt. They are physical mixtures of accreted components (chondrules, refractory inclusions, metal and sulfide, dust) whose characteristics and mineralogy we will describe. The classification of chondrites utilizes a combination of primary features (bulk chemical composition, oxygen isotopes) and secondary features (thermal metamorphism or aqueous alteration). About 14% of meteorites arriving on Earth consist of differentiated materials. Their compositions have been affected by melting and crystallization, and they include various kinds of achondritic meteorites, irons, and stony irons from the asteroid belt, along with lunar samples and Martian meteorites. Achondrites, so-named because they do not contain chondrules, are divided into two types. Primitive achondrites are the solid residues left behind after extraction of partial melts from chondritic material. Magmatic achondrites crystallized from the extracted melts or from completely melted and differentiated chondritic material. Irons and stony irons formed by separation of molten metal/sulfide from silicates. Lunar rocks include cumulates from the ancient highlands and mare basalts that flooded huge craters. Martian meteorites include basalts and cumulates formed from basaltic magmas. Primitive versus differentiated Cosmochemistry is the study of the chemical compositions of various solar system materials. Chondrites are the most abundant primitive samples.

Cosmochemistry: Meteorites: a record of nebular and planetary processes

GRAINS IN UNEQUILIBRATED ORDINARY CHONDRITES. A. Takigawa, R. M. Stroud, L. R. Nittler, E.P. Vicenzi, A. Herzing, C. M. O’D. Alexander, and G. R. Huss, Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015, USA, atakigawa@ciw.edu, Kyoto University, Kyoto, Japan, Naval Research Laboratory, Washington DC, USA, Smithsonian Institution, Suitland, MD, USA, National Institution of Standards and Technology, Gaithersburg, MD, USA, University of Hawai‘i at Mānoa, Honolulu HI, USA

Crystal Structure, Morphology, and Isotopic Compositions of Presolar Al2O3 Grains in Unequilibrated Ordinary Chondrites

Recent advances in active particle selection in the Heidelberg Van de r Graaf (VdG) dust accelerator have led to high-fidelity, low-backgro und calibrations of track sizes in aerogel as a function of particle size and velocity in the difficult regime above 10 km sec..1 and sub micron sizes. To the extent that the VdG shots are analogs for inters tellar dust (ISD) impacts, these new measurements enable us to place preliminary constraints on the ISD flux based on Stardust@home data.

/pdf/constraints-on-the-interstellar-dust-flux-based-on-stardust-3e1rllywu5.pdf

Gary R. Huss

Papers

O and Mn-Cr Isotope Systematics of a Fayalite-Silica Particle from Comet Wild 2

Do Antarctic Meteorite Concentrations Reflect the Average Infall Rate

Cosmochemistry: Meteorites: a record of nebular and planetary processes

Crystal Structure, Morphology, and Isotopic Compositions of Presolar Al2O3 Grains in Unequilibrated Ordinary Chondrites

Constraints on the interstellar dust flux based on Stardust@home search results