February 2021 -- Shedding Light on the European Alps
The European Alps are one of the most studied orogens in the world. Research over last 30 years is forcing us to rethink our understanding of Alpine evolution: new concepts have emerged that question long-established paradigms. We will provide a petrological, geochemical, and tectonic overview of the Alpine Orogeny, from rifting and spreading to subduction and collision and, finally, to postcollisional uplift and erosion. In this issue, we shed light on the current debates regarding the origins of (ultra-)high-pressure metamorphism, the origins of syncollisional magmatism, and the evolution of rifting and ocean spreading. We also examine the consequences of the new interpretations on the dynamics of subduction and collision.
Growing slowly drip by drip through the millennia, stalagmites, stalactites, and flowstone—collectively known as speleothems—are some of the most fantastic mineral features in nature. Speleothems are also critical archives of past environments, and their study incorporates expertise from groundwater hydrogeology and geochemistry, atmospheric chemistry, climate science, geobiology, and even geophysics. Research on speleothem trace element and isotopic geochemistry, constituent organic compounds, noncarbonate minerals, and morphology can help illuminate paleoenvironmental conditions and document historical anthropogenic land-use changes. This issue of Elements will introduce the many ways that speleothems are used within the geoscience community to learn about natural Earth processes and our role in modifying them.
June 2021 -- Exploring Earth and Planetary Materials with Neutrons
For over half a century, the structural details and the dynamics of atomic arrangements in materials have been determined using neutron-based scattering and absorption measurements. Neutron scattering experiments have contributed valuable information on geological materials and how these interact with fluids. In situ studies of transformations and fundamental properties can emulate diverse environments from Earth’s surface to its deep interior. Potential growth of the “neutron community” is being realized with the development of new and improved neutron sources. This issue will familiarize the reader with the basic concepts of neutron scattering, the methods that are available to Earth scientists, provide a summary of facilities around the world, and give key applications of the technique.
A revolution in astronomical observation has expanded the horizon of geological processes out from the handful of rocky and icy bodies in our solar system to the now thousands of planets detected around other stars (“exoplanets”). A major result from this burgeoning field is that rocky planets are the most abundant. A remarkable ∼11% of Sun-like stars host planets similar in their size and incident flux to Earth, whilst many more planets may exist in states relevant to past periods of terrestrial evolution, either trapped as perpetual magma oceans or locked into a snowball climate. This issue will highlight the myriad opportunities exoplanets represent for investigating fundamental geological processes and the opportunities for the geosciences to contribute to this exciting young field.
Carbonatites are rare, but important, igneous rocks in the Earth’s crust. They are composed dominantly of the Ca, Mg, and Fe carbonates, along with many other minor and trace components. The popularity of high-tech devices—smart phones, electric motors for zero-emission vehicles, wind turbines for renewable energy—has led to a renewed focus on these enigmatic carbonatite magmas, because to make these devices requires rare earth elements and the majority of the world’s rare earth elements are associated with carbonatites. This issue explores the current models for how carbonatites form and evolve in the mantle or crust, the temporal and tectonic controls on their formation, why they are so enriched in rare earth elements, and what are their economically significant minerals.
December 2021 -- Heavy Stable Isotopes: From Crystals to Planets
Since their discovery in 1913, stable isotopes have become formidable tracers of physicochemical processes at all scales. Steady advances in mass spectrometry have allowed isotopic inquiries to move from the so-called “traditional” systems (i.e., H, C, N, O, and S) to heavier “nontraditional” systems (e.g., Fe, Mo, Ti, Zr, U) whose diverse geochemical characteristics are providing novel and complementary insights. Moving from micron-size systems (single crystals) to planetary-size bodies, the articles in this issue will explore the enormous range of temporal and physical scales over which heavy stable isotopes have provided paradigm-shifting insights into the evolution of our planet and solar system. We will also highlight new frontiers where novel stable isotope systematics appear particularly promising for unraveling long-standing questions.