Experimental petrology and petrogenesis of mare volcanics

作者：John Longhi · 发表于：Geochimica et Cosmochimica Acta · 年份：1992 · 被引用次数：202 · 研究领域：Geological and Geochemical Analysis、Geology and Paleoclimatology Research、Paleontology and Stratigraphy of Fossils

Mare volcanics consist of basalts and picritic pyroclastic glasses spanning a wide range of TiO2 concentration. The more primitive low-Ti basalts and picritic glasses have olivine alone on their lowpressure liquidi. Most of the chemical variation among the low-Ti basalts is the result of olivine fractionation in a series of parental MgO-rich liquids differing in TiO2 concentration. With one possible exception (Apollo 17 VLT) none of the picritic compositions is a suitable parent for any of the observed low-Ti basalts. Most of the chemical variation among the high-Ti basalts is the result of a series of magmas fractionated along the low-pressure olivine + armalcolite/ilmenite cotectic. All of the picritic high-Ti glasses have olivine alone on the liquidus, but none is a suitable parent for any of the basalts. Volcanics with intermediate TiO2 concentrations (5 to 10 wt%) are widespread in the maria, even though they are not well represented in the sample collections; however, there is no evidence either among the samples or from remote sensing studies of basalts with > 13 wt% TiO2 that would be expected as differentiates of the picritic glasses with the highest TiO2 concentrations. Controlled-cooling-rate crystallization studies on a variety of mare compositions have provided the basis for reconstructing the size and, in some cases, stratigraphy of mare flows. Groundmass textures, crystal size, crystal morphology, nucleation density, and zoning patterns have all been employed t...