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Modeling and Interpreting Zircon Record During Formation and Evolution in Crustal Magma Bodies by Dike/Sill Injectionsтезисы доклада Тезисы
- Авторы: Melnik O.E., Bindeman I.N., Utkin I.S.
- Сборник: American Geophysical Union (AGU) 2019 Fall Meeting
- Тезисы
- Год издания: 2019
- Издательство: AGU Publications
- Местоположение издательства: Вашингтон
- Первая страница: abstract #V51H-0148
- Аннотация: We present a model of magma bodies formation by injection of basaltic or hot rhyolitic magmatic dikes leading to their incremental accumulation into the plutons and magma chambers in the upper and middle crust. Our newly created 2D model simulates random or organized dike injection into a selected rock volume, calculation of magma and rock displacement based on analytical solution of an elastic problem of elliptical cavity expansion, a realistic melt phase diagrams for country rock and magma. Lagrangian particle transport is calculated in order to reduce numerical dissipation and avoid unphysical mixing. Thermal histories in individual batches of magma and country rock are recorded. We further combine this model with Bindeman and Melnik (2016, JPet, 57:437) zircon crystallization/dissolution software and compute zircon survival histories in each Lagrangian particle. The model also predicts shapes of realistic T-t histories, zircon age distribution in different portions within a progressively growing reservoir and generates output to estimate crustal vs mantle contributions (e.g. Hf and O isotopes in zircons). Simulations reveal that the rate of melt production is highly variable in space and time, eruptible magma batches form in clusters, period of initial magmatic incubation is followed by crustal rock melting and formation of a large volume of eruptible magma with high melt fraction. Upon termination of magma supply, basaltic melt rapidly solidifies while silicic country rock melt progressively and forms a melt halo around the injection region. Zircon survival is dependent on the flux rate and rhyolitic magma preserves more inherited zircons in the formed magma chamber. In the case of basaltic magma injection, large preexisting zircon crystals melt down completely and their old cores do not survive in the central part of intrusive region, while at periphery zircons in partly molten country rocks can preserve their cores. Model outputs are compared to published zircon age spectra for small to supervolcanic volume rhyolitic eruptions and plutons.
- Добавил в систему: Мельник Олег Эдуардович