![]() ![]() Sedimentary rocks during the Middle–Upper Eocene. Sediments of the Paleocene–Eocene and then continueĮxtensively with shallow submarine to sub-aerial basalticĪnd andesitic volcanics, related volcaniclastics and DAEV start with continental to shallow marine Volcanic–plutonic belt of the Central Iran structural (DAEV) is located at the northeastern edge of the Calculated residence time of magma in Qisir Dagh, based on 3D crystal size distribution data, and using growth rate G = 10-10 mm/s, varies between 457 and 685 years, that indicates a shallow depth (near surface) magma crystallization and subvolcanic nature of the studied samples. This is also supported by the formation of antiperthite lamellae, which was formed as the result of alkali feldspar exsolution in plagioclase. Or=0.9-66.97), suggesting complex process during the crystal growth. ![]() Chemical composition of plagioclase shows a wide variation in abundances of Anorthite-Albite-Orthoclase (An=0.31-64.58, Ab-29.26-72.13. Crystal size distribution diagrams point to the presence of at least two populations of plagioclase, indicating the occurrence of magma mixing and/or fractional crystallization during magma cooling. ![]() Based on microscopic studies, it is shown that 2-dimensional size average of plagioclase in the micromonzogabbros is 538 micrometers and its 3-dimensional shape varies between tabular to prolate. Considering the importance of plagioclase in reconstructing magma cooling processes, the size and shape distribution and chemical composition of this mineral were investigated. Microgranular and microporphyritic textures are well developed in these rocks. Micromonzogabbroic rocks in the region consist of plagioclase, alkaline feldspar and clinopyroxene as the major mineral phases and orthpyroxene, olivine, apatite and opaque minerals as the accessory minerals. The Qisir Dagh igneous complex occurs as a combination of volcanic and intrusive rocks in the south-east of the Sabalan volcano, north-west of Iran. Upon thermal equilibrium, the FMEs would have an increased crystal cargo, and the resulting touching framework would impart a solid-like behavior to the FME-forming magma, which would lead to a contrast in rheology, fragmentation, dragging and preservation of felsic replenishment batches as distinct enclaves. Thermal modeling suggests that a slightly more primitive, hotter magma would be thermally equilibrated with an evolved resident melt within weeks after mixing/mingling. Crystal size distributions (CSDs) of plagioclase in samples drilled from rinds and cores of three FMEs show that the rind samples are systematically finer-grained than the samples from the cores, which indicates that the FMEs cooled inwards and contradict interpretations that the FMEs are autoliths. These indicate that the enclaves derive from a similar source, although the melts from which they formed were probably hotter and chemically more primitive than their host granites. The FMEs are cm- to meter-sized, have spheric shapes, show corrugated contacts with the host granites, and have resorbed feldspars and deformed quartz crystals interpreted as xenocrysts set in a fine-grained groundmass. Nd-Sr isotope and textural data from felsic microgranitoid enclaves (FMEs), mafic microgranitoid enclaves (MMEs) and host granites from the Salto pluton, Itu Granitic Province, show that the cm-sized MMEs are dioritic, have medium-grained igneous textures and xenocrysts of alkali feldspar and quartz. However, microgranitoid enclaves span a wide range of compositions, and felsic varieties are also frequently reported. Microgranitoid enclaves (MEs) are considered to be remnants of such mixing processes, and the term has a well-established genetic implication. Magma mixing is widely recognized in contemporary petrology as one of the primary igneous processes. ![]()
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