| Abstract [eng] |
The lunar felspathic breccia NWA 15352 has been studied in this work. Detailed petrological and microstructure investigation performed together with a Pb-Pb isotope analysis revealed the complexity of its composition and history. NWA 15352 is composed of various mineral fragments and different types of clasts embedded in a melt matrix where dominant minerals are Ca-rich plagioclases, olivines pyroxenes and ilmenite with a minor spinel, FeNi metals, sulfates and late phases such as zircon, phosphates and K-rich glass. Three types of clasts were identified: anorthosite clasts, breccia clasts and melt clasts. Fractures on the mineral surfaces, angular shape of minerals and partially melted clasts may evidence multiple, the impact event related, shock events that crushed, scattered, remelted and mixed different lithologies of lunar material present in the NWA 15352. The high An (>90) content in plagioclase reveals that some clasts were likely to originate from the lunar highlands while presence of Mg-rich spinel fragments may indicate that the material was excavated from the lunar upper mantle through the large impact events. The mixture of clasts linked both to the lunar highlands and mare basalts, points toward the most likely source region for the NWA 15352 to be some place at the mare-highland boundary. The Pb-Pb isotope analysis reveals a 3846 ± 44 Ma crystallization age of the lunar basalt clast associated with an Imbrium period while the crater counting ages of mare basalts overlap with the regions on the lunar near side: Mare Serenitatis, Mare Marginis, Mare Australe, and Fra Mauro Formation Unit near the Apollo 14 landing site. |
