Small-scale disequilibrium in a magmatic inclusion and its more silicic host
作者： Jon P. Davidson , Shanaka L. de Silva , Peter Holden , Alex N. Halliday
关键词: Geology 、 Geochemistry 、 Magma 、 Mafic 、 Plagioclase 、 Dacite 、 Basaltic andesite 、 Inclusion (mineral) 、 Silicic 、 Magma chamber 、 Earth-Surface Processes 、 Ecology (disciplines) 、 Earth and Planetary Sciences (miscellaneous) 、 Space and Planetary Science 、 Palaeontology 、 Forestry 、 Aquatic science 、 Atmospheric Science 、 Soil science 、 Geochemistry and Petrology 、 Geophysics 、 Oceanography 、 Water Science and Technology
摘要: Basaltic andesite inclusions and their host dacite from the Purico-Chascon complex in northern Chile are isotopically distinct. Textural characteristics of typical those resulting magma mingling. Serial sectioning across interface an inclusion its dacite, complemented by microdrill sampling detailed microprobe work, has enabled us to examine scale mixing chemical (isotopic trace element) disequilibrium. The results this work show that (1) composition is relatively homogeneous; (2) generally higher 87Sr/86Sr lower 143Nd/144Nd than enclave, but it heterogeneous on a small scale, probably “hybrid”; (3) isotopic marginal zone, apparently both sides weakly chilled interface, actually shows highest lowest 143Nd/144Nd; (4) large plagioclase crystals xenocrystic, with any other samples. These observations reconciled model evolution crustal chamber. In such scenario mafic overlain cap rhyolite—a partial melt dacitic ignimbrites which now underlie complex. Overturn system gives rise hybrid containing discrete inclusions.
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