![]() Mare basalts exhibit a wide range of composition resulting from nearsurface fractionation of chemically distinct primary basaltic magmas. This volcanic activity was possibly an extension of the thermal event that initiated pre-basin voleanism. Basin-associated eruption of mare basalts occurred during and following the late stages of catastrophic bombardment. Stage 5 is the late remelting of magma ocean cumulates and eruption of mare basalts. The KREEP basalts may be volcanic equivalents to both the Mg suite and alkali suite. The relationship between early stages of lunar voleanism and the contemporaneous plutonism is not clear. ![]() Sample analysis and remote sensing data indicate that early lunar voleanism (KREEP basalts and high-alumina basalts) was contemporaneous with periods of liiglilands plutonism and catastrophic bombardment of the hmar surface. The alkali suite could represent either the differentiation products of Mg suite parental magmas or a separate, but contemporaneous episode of basaltic magmatism. A KREEP and crustal signature was incorporated into these primitive basaltic magmas through assimilation near the base of the lunar crust or through melting of a hybridized mantle. Whereas the ferroan anorthositic crust was probably produced during the crystallization of a magma ocean, the slightly younger Mg suite and alkali suite plutonie rocks may have been generated by decompressional melting of early magma ocean cumulates during cumulate pile overturn. Stage 3 is the post-magma ocean highland magmatism. This resulted in transport of late-forming cumulates into the deep lunar mantle and mixing of magma ocean cumulates on a variety of scales. Soon after the crystallization of most of the lunar magma ocean, the cumulate pile experienced gravitational overturn. Stage 2 is the disruption of lunar magma ocean cumulates. Estimates for the tune over which melting and crystallization occurred range from tens to hundreds of millions of years. The extent of lunar melting and mantle processing depends strongly on the mechanisms that induced melting. Partial melting of the Moon soon after accretion was responsible for producing an anorthositic crust and a differentiated lunar interior. Stage I is early lunar differentiation and associated magmatism. In this review, we group magmatism into multiple stages of activity based on sampled rock types and evaluate the models for each stage. These reconstructions have illustrated the continous nature of lunar magmatism (from 4.6 to ~2.0 Ga) and the large influence of early differentiation and catastrophic bombardment on lunar mantle dynamics, magmatism, and eruptive style. Although incomplete because of the imperfect and somewhat random sampling of rock types by the Apollo and Luna missions (1969-1976), the history of lunar magmatism has been reconstructed by numerous researchers over the past three decades.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |