ArticlesSpecial Mineral Studies

Crystallization of Some Lunar Mafic Magmas and Generation of Rhyolitic Liquid

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Science  30 Jan 1970:
Vol. 167, Issue 3918, pp. 610-612
DOI: 10.1126/science.167.3918.610


During crystallization of lunar crystalline rocks 10022 and 10024, augite changes in composition almost continuously from titanaugite (Ca36Mg47 Fe, 17 with TiO2 3 percent) to a very iron-rich variety (Ca9Mg5Fe86), pigeonite changes from Ca9Mg66Fe25 to Ca1OMg51Fe39, and olivine changes (in 10022) from Mg71Fe29 to Mg41Fe59, whereas plagioclase stays as bytownite. These compositional variations, as well as the textural relations, may be explained by rapid crystallization of undercooled magmas. The residual liquids found as mesostasis are rhyolitic, which suggests that fractional crystallization of some lunar mafic magmas can generate rhyolitic magmas. Melting experiments were made on crystalline rocks to determine liquidus temperatures and crystallizing phases.