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Author name: Brian Kendall

Reel-to-Reel Re-Os Records: Earth System Transactions Preserved in Sediments

Re-Os – Clock with Clout, Thematic Articles /

A unique feature of the Re-Os isotope system is its ability to provide precise and accurate depositional ages from organic-rich sedimentary rocks. Applications include geologic timescale calibration, stratigraphic correlation, and dating key events such as biological innovations, mass extinctions, carbon cycle perturbations, Snowball Earth glaciations, and atmospheric oxygenation. Multiple sediment types reveal temporal variations in the osmium isotope composition of seawater, driven by changes in osmium inputs from continental weathering, seafloor hydrothermal systems, and extraterrestrial material. These variations provide valuable information on climate–tectonic interactions, glacial–interglacial cycles, large igneous province magmatism, bolide impacts, and crustal evolution. Continental processes can be inferred from lake sediment records. These diverse applications highlight the central role of the Re-Os isotope pair in understanding Earth’s evolution.

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Sulfides and Their Little Darling, Molybdenite

Re-Os – Clock with Clout, Thematic Articles /

Rhenium-osmium geochronology of sulfides and its Os tracer accompaniment have taken their place among geochronometers, although the journey was not without doubters and disparagers. This review highlights several historical hurdles overcome in dating sulfides. The opening act was the debut of molybdenite, which provided an accessible radiometric clock and early insight into the accuracy of the 187Re decay constant. Once controversies surrounding newly minted and game-changing Re-Os molybdenite ages died down, the door flung wide open to begin dating other sulfides, most notably, arsenopyrite and pyrite. Applications sprinted from the ore geology community to constraining the timing of important events, from Earth’s oxygenation to the amalgamation of tectonic terranes. The power of Re-Os sulfide dating in crustal environments was unleashed.

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December 2025 --The Variscan Orogeny in Europe – Understanding Supercontinent Formation

The Variscan orogen formed between 380 and 300 million years ago through several accretionary and collisional cycles, culminating with the construction of the Pangea supercontinent. This process occurred via sequential opening and closure of oceanic basins, synchronous detachment of Gondwana derived continental ribbons, and their outboard amalgamation onto the Laurussia margin. The Variscan orogen is rather unique compared with other orogenic belts on Earth: its overthickened and dominantly magmatic crust in the central belt, surprisingly minor mantle involvement in the magmatic and geodynamic processes, coherent and pulsed magmatism along the collision suture, and its complex accretionary history. Because its final product, Pangea, is the youngest and best-understood supercontinent on Earth, the Variscan orogeny offers clues for understanding the mechanisms of supercontinent formation.