Abstract
A series of melting-crystallization experiments on alkali basalt samples from Minqing, Fujian Province was carried out in dry and waterbearing systems at high pressures. A high-pressure melting curve was obtained. The results indicate that clinopyroxene crystallized from basalt melt at 13.5–23.7 kbar. spinel at 23.7–28.6 kbar and garnet at > 28.6 kbar. With increasing pressure, the CaSiO3 contents of clinopyroxenes increase; and the FeSiO3 decreases, but the chemical composition of garnet does not show any significant difference. The minerals are larger and euhedral in the water-bearing system. Therefore, we consider that natural megacrysts of the basalt can crystallize from the water-bearing basalt magma at high pressure. So the megacrysts may be derived from the upper mantle as a result of magmatic crystallization-fractionation under high pressure.
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This project was financially supported by the National Natural Science Foundation of China.
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Guohao, R., Hongsen, X. & Xiande, X. An experimental melting-crystallization study on basalt at high pressures. Chin. J. of Geochem. 10, 174–179 (1991). https://doi.org/10.1007/BF02837717
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DOI: https://doi.org/10.1007/BF02837717