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

Introduction: The former presence of short-lived radionuclides (SLRs) in the early solar system ( 10 Be, 26 Al, 36 Cl, 41 Ca, 53 Mn, 60 Fe, 107 Pd, 129 I, and 182 Hf) is inferred from excesses in the abundances of their daughter nuclides in meteorites, linearly correlated with the abundances of parent elements [e.g.,1]. SLRs with mean lives <5 Myr can be produced either by energetic-particle irradiation or by stellar nucleosynthesis. Solar energetic-particle irradiation can produce the required amount of 10 Be and probably some other SLRs [2], but cannot produce the estimated initial abundance of 60 Fe in the solar system [3-5]. Because 60 Fe is produced efficiently only in stars, and its estimated abundance in the solar system cannot be explained by the steady-state abundance of 60 Fe in the interstellar medium, stellar nucleosynthesis prior to or shortly after the solar system formation should have contributed to the inventory of the solar-system SLRs. Several attempts have been made to find a suitable stellar source for the solar-system SLRs [e.g., 6-8]. Low-mass AGB stars produce insufficient amounts of 60 Fe [e.g., 8]. Models for intermediate-mass AGB stars may explain the abundances of 26 Al, 41 Ca and 60 Fe [8], but the rarity of encounters between molecular clouds and AGB stars [9] makes it implausible for an AGB star to be a source of SLRs in the solar system. Several nucleosynthetic models for SNe II [e.g., 10-13] indicate that 60 Fe may have been overproduced if all the 26 Al and 41 Ca in the solar system were provided by a SN II. Moreover, the abundance of 53 Mn inferred for SNe II is 10-100 times larger than that in the solar system. If a massive star exploded with less kinetic energy, most of 53 Mn synthesized in the incomplete Siburning layer may have undergone fallback onto a collapsing stellar core [12]. If this is the case, 53 Mn in the solar system should have been derived from another source, i.e., the continuous galactic nucleosynthesis. In this study, as a potential stellar source of SLRs with <5 Myr ( 26 Al, 41 Ca, 53 Mn, and 60 Fe) in the early solar system, we propose a SN II with mixing-fallback, where the inner region of the exploding star experienced mixing, some fraction of mixed materials is ejected, and the rest undergoes fallback onto the core [e.g., 13]. The mixing-fall back model well reproduces the abundance pattern of hyper metal-poor stars [13]. Methods: We calculated yields of nuclides in the ejecta from a SN II with mixing-fallback based on the nucleosynthesis model for a solar-metallicity massive star with the kinetic energy of explosion of 10 51 erg [13] using the mass of the inner mixing region (Mmix) and the fraction of materials ejected from the mixing region (q) as parameters. We assumed that the ejecta was mixed with protosolar materials (or the protoplanetary disk) with a dilution factor of f0, and that there was a time interval of between the SN II nucleosynthesis and the formation of the oldest solid objects in the solar system [6-8]. The f0 and were determined to minimize deviations of calculated abundances of 26 Al, 41 Ca, 53 Mn, and 60 Fe from their estimated initial abundances in the solar system. The abundance of 36 Cl was also calculated using determined f0 and to compare with the reported lower limit of 36 Cl abundance in the solar system. The cases for SNe II without mixing-fallback were calculated based on the models by [10-13] as well. Results: Figure 1 shows calculated initial abundances for the solar system of 26 Al, 36 Cl, 41 Ca, 53 Mn, and 60 Fe as a function of the mass of the exploding star. The abundances of SLRs inferred in non-fallback models are also shown for comparison. Compared to non-fallback models, where 53 Mn is overproduced and 26 Al is underproduced, the inferred abundances of 26 Al, 36 Cl, 41 Ca, 53 Mn, and 60 Fe in mixing-fallback models agree with their estimated solar-system abundances within a factor of 3 if mixing occurs within the C/O burning layer and the ejection fraction q of the mixed material is 0.001-0.01 (Fig. 2). However, if mixing occurs in the He-burning layer as well, i.e., larger Mmix, 53 Mn is overproduced and 60 Fe is underproduced (Fig. 2). If degree of mixing is small and mixing occurs only within the Si-burning layer, 53 Mn is overproduced and 26 Al is underproduced, as in the case for nonfallback models (Fig. 2). Note that the solar-system abundances of SLRs are well reproduced in a wide range of masses of the star (20-40 MSun) as long as the mixing-fallback occurs within the C/O burning layer. The f0 varies from ~10 -5 for smaller Mmix to ~10 -3

Contribution of a "Mixing-Fallback" Supernova to Short-Lived Radionuclides in the Solar System

IN CHONDRULES FROM CR CHONDRITES: LINKING OXYGEN FUGACITY AND O-ISOTOPE EVOLUTION. D. L. Schrader, H. C. Connolly Jr., D. S. Lauretta, K. Nagashima, and G. R. Huss. LPL, Univ. of Arizona, Tucson, AZ 85721, USA, Dept. Physical Sciences, Kingsborough Community College of CUNY, Brooklyn, NY 11235 and Earth and Environmental Sciences, The Graduate Center of CUNY, New York, NY 10024, Dept. Earth and Planetary Sciences, AMNH, New York, NY 110024, USA, HIGP, Univ. of Hawai‘i at Mānoa, Honolulu, HI 96822. Email: schrader@lpl.arizona.edu

Relationship Between FeO Content and ∆17O in Chondrules from CR Chondrites: Linking Oxygen Fugacity and O-Isotope Evolution

Cosmochemistry: Introduction to cosmochemistry

We have recently begun a major collaborative project to determine the relative abundances of meteorite types over geologic time using remnant extraterrestrial chrome-spinels. These grains resist weathering and are preserved in terrestrial limestone [1]. The assignment of chrome-spinels to meteorite types requires multiple tools and techniques. The combination of chemical composition, oxygen isotopes, and the mineralogy and chemical composition of inclusions within the chrome-spinel define the host meteorite type. This work concentrates on samples from the Jurassic (~160 Myr ago).

Using Micro-Beam Techniques to Infer Meteorite Abundances of the Jurassic

We report the petrology, O isotopic composition, and Al-Mg isotope systematics of a chondrule fragment from the Jupiter-family comet Wild 2, returned to Earth by NASA's Stardust mission. This object shows characteristics of a type II chondrule that formed from an evolved oxygen isotopic reservoir. No evidence for extinct 26Al was found, with (26Al/ 27Al)0 < 3.0 x 10^-6. Assuming homogenous distribution of 26Al in the solar nebula, this particle crystallized at least 3 Myr after the earliest solar system objects--relatively late compared to most chondrules in meteorites. We interpret the presence of this object in a Kuiper Belt body as evidence of late, large-scale transport of small objects between the inner and outer solar nebula. Our observations constrain the formation of Jupiter (a barrier to outward transport if it formed further from the Sun than this cometary chondrule) to be more than 3 Myr after calcium-aluminum-rich inclusionss.

Gary R. Huss

Papers

Contribution of a "Mixing-Fallback" Supernova to Short-Lived Radionuclides in the Solar System

Relationship Between FeO Content and ∆17O in Chondrules from CR Chondrites: Linking Oxygen Fugacity and O-Isotope Evolution

Cosmochemistry: Introduction to cosmochemistry

Using Micro-Beam Techniques to Infer Meteorite Abundances of the Jurassic

Incorporation of a Late-forming Chondrule into Comet Wild 2