Detail Anatexis and metamorphism of crustal rocks during magmatic accretion: Field and numerical results Bibliografi Author: Barboza, Scott Alan ; Ghiorgo, Mark (Advisor) Topik: GEOLOGY Bahasa: (EN )    ISBN: 0-599-15491-8     Penerbit: University of Washington     Tahun Terbit: 1998     Jenis: Theses - Dissertation Fulltext: 9916621.pdf (0.0B; 0 download) Abstract The generation of crustal melt and its subsequent segregation and ascent comprise a fundamental set of processes that results in the chemical differentiation of continental crust. Interpreting magmatic products and explaining their petrologic diversity requires a quantitative understanding of the physical and chemical factors that influence the generation of felsic melts in the source region. Crustal melting followed by the fractionation of refractory phases, and/or mixing crustal components with fractionated mantle-derived melts can cause compositional variability in the products of crustal magmatism. Both models of granitoid magmatism imply a change in the thermal conditions in the source region, a requirement that may be explained by the intrusion of sills of mantle-derived magma at or near the base of the crust (underplating). However, the response of crustal rocks to the intrusion of mafic magma (magmatic accretion) is not well understood. Variable estimates of the time and length scales of crustal melting following magmatic accretion have been obtained by different theoretical and numerical studies. Crustal melting models based on the assumption of near turbulent conditions within the intrusion have predicted rapid cooling and bulk melting of the overlying crustal rocks. The results of other numerical studies suggest lower rates of heat transfer and more limited crustal melting in response to underplating. An integrated approach linking the results of numerical simulations with field and geochemical observations is required to discriminate between the alternative models and yield a more complete model of crustal anatexis. In this study I present the results of a series of numerical and field studies. The numerical studies demonstrate that rapid convective heat transfer and bulk melting during magmatic accretion is a limiting case which may not be realized in the natural setting due to the complex chemical and rheological response of crustal rocks to the heat released during magmatic accretion. The field studies demonstrate that emplacement of even large volumes of mafic magma may be associated with only narrow contact aureoles of depleted rocks. These results demonstrate that magmatic accretion may not inexorably lead to regional metamorphism and widespread anatexis. Opini Anda Klik untuk menuliskan opini Anda tentang koleksi ini! Lihat Sejarah Pengadaan  Konversi Metadata   Kembali

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