Search results for "subduction zones"
showing 4 items of 4 documents
Partitioning of nitrogen during melting and recycling in subduction zones and the evolution of atmospheric nitrogen
2019
Abstract The subduction of sediment connects the surface nitrogen cycle to that of the deep Earth. To understand the evolution of nitrogen in the atmosphere, the behavior of nitrogen during the subduction and melting of subducted sediments has to be estimated. This study presents high-pressure experimental measurements of the partitioning of nitrogen during the melting of sediments at sub-arc depths. For quantitative analysis of nitrogen in minerals and glasses, we calibrated the electron probe micro-analyzer on synthetic ammonium feldspar to measure nitrogen concentrations as low as 500 μg g−1. Nitrogen abundances in melt and mica are used together with mass balance calculations to determi…
Two-Stage Origin of K-Enrichment in Ultrapotassic Magmatism Simulated by Melting of Experimentally Metasomatized Mantle
2019
The generation of strongly potassic melts in the mantle requires the presence of phlogopite in the melting assemblage, while isotopic and trace element analyses of ultrapotassic rocks frequently indicate the involvement of subducted crustal lithologies in the source. However, phlogopite-free experiments that focus on melting of sedimentary rocks and subsequent hybridization with mantle rocks at pressures of 1&ndash
Polarity-reversal subduction zone initiation triggered by buoyant plateau obstruction
2022
Abstract Oceanic lithosphere worldwide is younger than ca. 200 Myr, suggesting that it must have been globally recycled by the recurrent formation of new subduction zones since the existence of subduction on Earth. However, postulated subduction zone initiation processes remain difficult to explain in many cases, and the specific geodynamic conditions under which these might occur are still largely unknown. We here use numerical models driven by the internal force balance of a subduction system to better understand the (geo)dynamics governing (intra-oceanic) polarity-reversal subduction zone initiation. This initiation mode assumes that the birth of a new subduction zone could be triggered …