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首页> 外文期刊>Contributions to Mineralogy and Petrology >An experimental study of dissolution and precipitation of forsterite in a thermal gradient: implications for cellular growth of olivine phenocrysts in basalt and melt inclusion formation
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An experimental study of dissolution and precipitation of forsterite in a thermal gradient: implications for cellular growth of olivine phenocrysts in basalt and melt inclusion formation

机译：热梯度溶解和沉淀的实验研究：玄武岩中橄榄石异晶胞细胞生长的影响及熔融包合物形成

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The morphology of crystals in magmas strongly depends on the temperature regime of the system, in particular the degree of undercooling and the cooling rate. To simulate low degrees of undercooling, we developed a new experimental setup based on thermal migration, in which large cylinders of forsterite (single crystals) immersed in haplobasaltic melt were subjected to a temperature gradient. As forsterite solubility is sensitive to temperature, the forsterite on the high-temperature side undergoes dissolution and the dissolved components are transported toward the low-temperature side where a layer of newly grown forsterite forms (up to 340 mu m thick after 101 h). A striking feature is that the precipitation process does not produce a planar front of forsterite advancing at the expense of liquid: the growth front shows a fingered outline in planar section, with solid lobes separated by glass tubes that are perpendicular to the growth front. We ascribe this texture to cellular growth, a type of growth that had not been experimentally produced so far in silicate systems. We find that the development of cellular growth requires low degrees of undercooling (a few degrees C) and large crystal-liquid interfaces (similar to 1 mm across or more), and that it occurs at a growth rate of the order of 10(-9) m/s. We found natural occurrences of cellular growth on the rims of olivines from basanites, but otherwise cellular textures are poorly documented in natural volcanic rocks. Melt inclusions were produced in our experiments, showing that they can form in olivine at relatively slow rates of growth (10(-9) m/s or lower).
机译：岩浆中的晶体的形态强烈取决于系统的温度制度，特别是过冷却的程度和冷却速度。为了模拟低温度，我们开发了一种基于热迁移的新的实验装置，其中浸入了浸没在碘酰卤熔融中的大圆柱（单晶）的大气缸进行温度梯度。作为Forsterite溶解度对温度敏感，高温侧的鳍状件经历溶解，溶解组分朝向低温侧输送，其中一层新种植的Fortarite形式（101小时后高达340μm厚）。引人注目的特征是沉淀过程不会以液体为代价产生散热片的平面前线：生长前面显示平面部分的指状轮廓，用玻璃管分离的固体凸起，垂直于生长前沿。我们将这种质地归于细胞生长，这是迄今为止硅酸盐系统实验产生的一种增长。我们发现细胞生长的发展需要低冷却（几度C）和大的晶体液体界面（类似于1mm以上），并且它以10（ - ）的生长速度发生（ - 9）m / s。我们发现来自Basanites的橄榄石圆环的细胞生长的自然发生，但是在天然火山岩中的植物纹理较差。在我们的实验中产生了熔体夹杂物，表明它们可以在橄榄石中形成橄榄石，以相对缓慢的生长速度（10（-9）m / s或更低）。

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