Evolution of Intraplate Magmas: An Experimental Approach

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9902931LindsleyThe goal of this research is to (1) test the hypothesisthat a variety of magma suites associated with plumes and rifting might bedescended from a common parental (although not primitive) magma; (2)determine variations in magmatic fractionation trends that are controlledby different pressures and oxidation states; (3) assess possible relationsbetween melts associated with anorthosites; and (4) test whether thesolubility of carbon at moderate pressures can cause strong iron-enrichmentin some magmas. The experimental technique used is fractionalcrystallization experiments performed in piston-cylinder pressureapparatus, with a variety of pressures, sample containers, and imposedoxygen fugacities. Experimental products are examined using thepetrographic microscope, x-ray diffraction, and the electron probemicroanalyser. When reactions between minerals and melt occur, or when theproportion of crystals exceeds 50%, a new bulk composition will besynthesized, corresponding to the composition of the melt in the previousexperiment. This procedure permits evaluation of fractionalcrystallization as temperature is lowered, yet maintains a relatively highproportion of melt in each experiment, which is useful for microprobeanalysis and attainment of equilibrium.