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Crystal size distribution (CSD) in metamorphic rocks provide fundamental information about crystal nucleation and growth rate, growth time and the degree of overstepping. CSD data for garnet, staurolite, kyanite and andalusite crystals from the aureole demonstrate that the earliest formed of these minerals, garnet, has the highest population density and the shortest growth time. The last formed mineral, andalusite, has the lowest population density and longest growth time. Kyanite  and  staurolite  have  the  similar  population  density  and  growth  times  intermediate  between those of garnet and andalusite. These data demonstrate the effect of the degree of overstepping on the nucleation and growth rates of minerals during metamorphism.

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In this study, quantitative textural analysis and crystal size distribution on amphibole, plagioclase and quartz in amphibole phenocrysts were studid by microprobe and thermobarometry techniques, give some information about magma process in magma chambers. Petrographic studies with microprobe and crystal size distribution investigations in Neogene igneous rocks of SW Tehran, demonstrate that there are three populations of amphiboles related to different conditions of crystallization at different depths and point to existence of at least three magma chambers below the volcano in this area. The occurrences of plagioclase in lavas confirm that magma evolution have taken place at lower depth in a magma chamber near the surface of the earth and at the lower fugacity of water.

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The studied sample presents garnet textural sector-zoning as inclusions in two types in garnet schist from Morlaix, North-West Brittany, France. Crystal size distributions (CSD) of quartz crystals were measured in both types inclusions, in the matrix and strain shadows around garnet porphyroblasts using Back-scatter electron (BSE) images. The CSD plots of quartz crystals show an increase of average in sizes from type 1 inclusion,60mm, to the matrix,116 mm, and strain shadow,248 mm,. These differences could be explained of quartzes size distribution by many processes such as capturing by pophyroblast, crystal face, annealing and grain boundary migration 

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The crystal size distribution (CSD) of kyanite and staurolite from the Hamza Qassim and Khazai Bala mtapelites has been studied. All samples show linear CSD pattern for kyanite and nonlinear concave down (with two distinct parts) for staurolite. The linear CSD for kyanite defines high growth rate and equal granular crystals. Two segmental patterns for staurolites can show that they have formed as a result of two possibilities, first is differences on reactions which form the mineral and second is differences on responsible regional metamorphic phase. Although the first case has more evidences. The Gt and nucleation rate (J) for kyanites were 0.931 and -1.6 mm^-4. For staurolites the fine and coarse grain parts population density was
 5.25 mm^-4 and 6.1 mm^-4. Average growth rate at time (Gt) calculated values for fine and coarse staurolite crystals were 0.405mm.t and 0.763mm.t. Detail studies show that nucleation rate ratios for staurolite was 5.5 times more than kyanites, but kyanite crystals were about 2 times coarser than staurolites.      

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The Kahak- Abbasabad Eocene magmatic belt is situated in the northeast edge of Central Iran Zone and extended from Davarzan in the west of Sabzevar to Mayamey in the east of Shahrood. Rock units of the study area include an alternation of basic- intermediate volcanic rocks (olivine basalt, basalt, Trachybasalt, trachyandesitic basalt, trchyandesite and andesite) and pyroclastic–sedimentary rocks (varieties of tuffs, breccia, agglomerate, sandstone, shale, conglomerate, nummolitic limestone and tuffuceous limestone), which belong to Upper-Middle Eocene, and sedimentary rocks of Oligocene and Quaternary. The volcanic rocks of this belt form a continuous fractional series, originated from a same parental basaltic magma. Hence, the basaltic-andesitic lava flows are pyroxene porphyry, plagioclase porphyry and pyroxene-plagioclase porphyry; they are favorable for Crystal Size Distribution (CSD) studies. According to calculations of this research, plagioclase and pyroxene phenocrysts of the volcanic rocks have been grown in magmatic chamber in time range of 86.20 to 118.01 years with nucleation rates from 1.48×10^-10 to 1.56×10^-10 mms^-1and in time range of 3.21 ×10⁴ to 6.34×10⁴ years with nucleation rates from 0.55×10^-3 to 2×10^-5mms^-1, respectively.

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Plagioclase is the most abundant mineral in basaltic andesites in the north Gavkhouni. Olivine and pyroxene are the other rock forming mineral there. In their 3-dimensional shapes, they are unequal and varies between bladed to prolate. Plagioclase sometimes exhibit dusty texture, oscillatory zoning and sinusoid growth. Based on crystal size distribution data, the rate of crystal nucleation of plagioclase varies between 2.77*10^-8-3.07*10^-8 mm^-3s^-1 in 71.78 - 17.77 years. The results indicate the higher nucleation rate, rapid cooling and a short crystal residence time in the magma chamber. The crystal size distribution diagrams show the high frequency of smaller crystals and the coarsening of the average crystals. However, the presence of two populations of plagioclase indicates the interfering of new magma with the same chemical composition and new crystal population into the magma chamber. This event can increase the volume of the magma chamber pressure and eruption of the magma.

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The purpose of this study is to explore the influence of whole rock chemistry of metamorphic protolith on the crystal size distribution curve of garnet in metapelites. With this aim, perfect mosaical photograph from two groups of metapelites have been prepared: regional (Shahindezh schists) and contact (Dorbeh Oshnavieh aureole) metamorphic rocks image processed and their patterns illustrated. They show that the nuclei numbers in the hornfelses are one fourth of schists, but when they start to grow, it is more than 40 times. These content in addition to high degree of overstepping during regional poly-phase metamorphism, show the important role of effective water fluid presence at the contact aureole and inhibitor role of it at nucleation which help ion transportation on the nucleation sites. Considering the similar composition of garnet in two groups (almanden), it is the symptom of suitable whole rock composition of hornfelses per schists to garnet grew.  

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Considering the importance of plagioclase in reconstructing magma cooling processes, the size and shape distribution of this mineral is investigated for Chah - Musa sub-volcanic intrusion (NW Toroud- Semnan Province). The slopes of CSD diagrams, the natural logarithm of the density of the crystalline density (n) against the length of the crystal (L), show plagioclase phenocrysts available in this intrusion have been grown with rates of 1.4×10^-8 to 9.27×10^-9 mms^-1, in time limited 118.62 to 630.7 years. The calculated residence time of magma in Chah-Musa intrusion coincides with sub-volcanic nature of the studied samples. Crystal size distribution diagrams suggest presence of two populations of crystals that formed during the anneal period as well as during decompression, associated with separate nucleation regimes.