February 2024 – Volume 20 Number 1
GUEST EDITORS
Mehmet Yesiltas and Yoko Kebukawa
PRINCIPAL EDITOR
Sumit Chakraborty
April 2024 – Volume 20 Number 2
GUEST EDITORS
Simon R. Wallis, Kazuhiro Miyazaki, and Ulrich Knittel
PRINCIPAL EDITOR
Becky Lange
June 2024 – Volume 20 Number 3
August 2024 – Volume 20 Number 4
October 2024 – Volume 20 Number 5
Extraterrestrial organic matter is found in various extraterrestrial environments and in various forms. It forms in a variety of locations through different mechanisms in space. As such, its nature, distribution, formation mechanisms and locations are of particular interest. Some organic molecules are even considered as key players for the emergence of life on Earth and possibly beyond. Therefore, their detection and characterization can contribute to the understanding of the early solar system evolution as well as the origin of life. Despite decades of work and research, there are still many questions and unknowns on this topic. The aim of this issue of Elements is to offer an overview of the concept of extraterrestrial organic matter as well as the latest scientific findings.
Subduction, where one plate dives beneath another, controls longterm wholeEarth cycling of rocks, fluids, and energy. Plates subduct faster than they heat up, making them the coldest parts of the Earth’s interior. Fluids released from these cold plates rise into hotter overlying rocks, forming magma that feeds surface volcanism. Cold deep conditions associated with subduction complemented by hot shallow conditions under volcanic arcs are reflected in the presence of pairs of metamorphic belts, representing sites of ancient subduction. This issue of Elements guides readers through a premier example of paired metamorphism: the Cretaceous SanbagawaRyoke metamorphic pair of Japan. Estimates of pressure, temperature, the age and duration of metamorphism, and the tectonic framework in which meta morphism took place help us to develop quantitative models—both for the evolution of SW Japan and subduction systems in general.
Hydrogen is the most abundant element in the universe and its distribution, transfer, and speciation in the deep Earth remain a fascinating topic of ongoing research. We review the most notable discoveries constraining the H cycle in the deep Earth. This includes new methods for detecting hydrogen, insights into the size of deep reservoirs, and new constraints from inclusions in ultradeep diamonds. Advances in seismic and magneto- telluric imaging provide unique data on the storage and mobility of water in Earth´s interior. Models of the early Earth and of its habitability critically depend on the behavior of hydrogen in a magma ocean–atmosphere system. Later in Earth history, water may have been essential for establishing plate tectonics, a phenomenon making Earth a unique planet.
Himalayan leucogranites crop out intermittently over 2000 km along the Himalayan crest in the Himalayan-Tibetan plateau. They constitute some of the most well-studied granites in the world. They are considered to be purely crustal-derived melts and indicators of collisional orogenesis, and have greatly improved our general understanding of crustal anatexis, differentiation of felsic magmas, and tectonic evolution of the Himalayan-Tibetan Orogen. They provide a rare opportunity to explore the feedback relationships among geodynamics, tectonics, and magmatism in a classic continental collisional context. In this issue, we will describe our current understanding of the petrogenesis and significance of the Himalayan leucogranites by focusing on their tectonic and geodynamic background, source rocks, petrology, geochemistry, and links to orogenesis and economic resources. This issue will not only summarize the state-of-the-art research on leucogranites but also present an example of how a multidisciplinary approach can be used to constrain the petrogenesis of granites and the associated mineralization and orogenic evolution.