An early giant planet instability recorded in asteroidal meteorites

Giant planet migration appears widespread among planetary systems in our Galaxy. However, the timescales of this process, which reflect the underlying dynamical mechanisms, are not well constrained, even within the solar system. Since planetary migration scatters smaller bodies onto intersecting orbits, it would have resulted in an epoch of enhanced bombardment in the solar system's asteroid belt. To accurately and precisely quantify the timescales of migration, we interrogate thermochronologic data from asteroidal meteorites, which record the thermal imprint of energetic collisions. We present a database of 40K-40Ar system ages from chondrite meteorites and evaluate it with an asteroid-scale thermal code coupled to a Markov chain Monte Carlo inversion. Simulations require bombardment in order to reproduce the observed age distribution and identify a bombardment event beginning ~11 million years after the Sun formed. Our results associate a giant planet instability in our solar system with the dissipation of the gaseous protoplanetary disk.Comment: 24 pages, 4 figures, 2 tables, 10 extended data items (8 figures, 2 tables). Under review at Nature Astronom

Regional trends and petrologic factors inhibit global interpretations of zircon trace element compositions

The trace element composition of zircon reveals information about the melt that they are derived from, as such, detrital zircon trace element compositions can be used to interrogate melt compositions, and thus the evolution of the continental crust in time and space. Here, we present a global database of detrital zircon compositions and use it to test whether average global trends for five common petrogenetic proxies truly represent secular changes in continental evolution. We demonstrate that the secular trend is broadly comparable across continental regions for Ti-in-zircon temperatures, but for other trace element ratios interrogated, secular trends are highly variable between continental regions. Because trace element ratios result from multiple petrologic variables, we argue that these petrogenetic proxies can be overinterpreted if projected to global geologic processes. In particular, we caution against the interpretation of crustal thickness from trace elements in zircon, and we argue that our results negate current hypotheses concerning secular changes in crustal thickness

Revisiting the discrimination and distribution of S-type granites from zircon trace element composition

Trace element compositions of zircon can be used to estimate the chemistry of their host magmas; as such they provide a useful tool in zircon provenance, and in the assessment of changing magma chemistries in time and space. Granites derived from the melting of sedimentary protoliths (S-types) have previously been discriminated by their P contents and P vs. REE+Y correlations, largely based on data from the Lachlan Fold Belt. Using a range of magmatic suites from different locations, we show that this discrimination commonly fails to discriminate S-type granite from others. We propose an alternative discrimination tool, based on a plot of Ce/U vs. Th/U, which makes use of low LREE/U and Th/U in metapelite-derived melts. Through coupled thermodynamic and accessory mineral saturation modelling, we demonstrate that these low ratios can be explained by monazite co-crystallisation. We demonstrate that Himalayan S-types, which are inferred to have formed from partial melting of metapelite, and thus can be classified as pure S-types, exhibit the lowest Ce/U and Th/U ratios, and overlap those of metapelitic zircon. Granites formed in oceanic arcs (I-types) and mantle-derived suites both have the highest Ce/U and Th/U ratios. Other S-types, such as those known to have mixed sedimentary and igneous protoliths, which we term Hybrid S-types, form a field overlapping pure I- and S-types. We use Ce/U versus Th/U to demonstrate the dominant I-type origin to early Earth (>3.6 Ga) zircon, and using a large detrital zircon database we assess the proportion of S-type zircon through Earth history. In contrast to previous findings, we find that the supercontinent Rodinia had a normal abundance of S-type zircon, as with other supercontinents, and that instead the period 1.7–1.2 Ga exhibits a marked low in S-type zircon, corresponding to fewer continental collisions

Curation and Analysis of Global Sedimentary Geochemical Data to Inform Earth History

Large datasets increasingly provide critical insights into crustal and surface processes on Earth. These data come in the form of published and contributed observations, which often include associated metadata. Even in the best-case scenario of a carefully curated dataset, it may be non-trivial to extract meaningful analyses from such compilations, and choices made with respect to filtering, resampling, and averaging can affect the resulting trends and any interpretation(s) thereof. As a result, a thorough understanding of how to digest, process, and analyze large data compilations is required. Here, we present a generalizable workflow developed using the Sedimentary Geochemistry and Paleoenvironments Project database. We demonstrate the effects of filtering and weighted resampling on Al2O3 and U contents, two representative geochemical components of interest in sedi-mentary geochemistry (one major and one trace element, respectively). Through our analyses, we highlight several methodological challenges in a "bigger data" approach to Earth science. We suggest that, with slight modifications to our workflow, researchers can confidently use large collections of observations to gain new insights into processes that have shaped Earth's crustal and surface environments

Chron.jl: A Bayesian framework for integrated eruption age and age-depth modelling

A model framework for the interpretation of mineral age spectra in stratigraphic contex

Geochemical Evolution of Earth’s Continental Crust

Earth’s unique continental crust represents the active interface between the deep earth and the surface earth system, and is crucial for the survival and diversification of life on Earth, both as a source for nutrients and a component in the silicate weathering feedback that stabilizes Earth’s equable climate on billion-year timescales. However, many open questions remain regarding the formation and secular temporal evolution of Earth’s crust – in part due to the extremely poorly-mixed nature of Earth’s continental crust such that compositional heterogeneity at any one point in geologic time typically dwarfs any systematic variation over time. New computational approaches enabled by the emergence of large, freely ac- cessible geochemical datasets provide a way to see through this heterogeneity and extract quantitative information about underlying processes and variables that drive the evolution of Earth’s crust over geologic time

Geochemical Evolution of Earth's Continental Crust

Earth’s unique continental crust represents the active interface between the deep earth and the surface earth system, and is crucial for the survival and diversification of life on Earth, both as a source for nutrients and a component in the silicate weathering feedback that stabilizes Earth’s equable climate on billion-year timescales. However, many open questions remain regarding the formation and secular temporal evolution of Earth’s crust – in part due to the extremely poorly-mixed nature of Earth’s continental crust such that compositional heterogeneity at any one point in geologic time typically dwarfs any systematic variation over time. New computational approaches enabled by the emergence of large, freely accessible geochemical datasets provide a way to see through this heterogeneity and extract quantitative information about underlying processes and variables that drive the evolution of Earth’s crust over geologic time

Isoplot.jl

For plotting and analysis of your isotopic ratio