Mineralogy and petrology of dikelets in the Station 7 boulder, Taurus-Littrow Valley, Apollo 17 Lunar Mission

Abstract

The Apollo 17 mission, launched December 7th, 1972, was the sixth and final human lunar surface landing of the Apollo Program. The Lunar Module Challenger touched down in the Taurus-Littrow Valley, near the Serenitatis impact structure. The mission returned 97 rock samples (~ 100 kg), 75 soil samples, and ~2200 photographs. The main focus of this thesis is a 3 m wide boulder at Station 7, located on the lower slope of the North Massif. The four main lithologies in the boulder are: (1) white noritic basalt cataelasite, (2) dark dikelets, (3) blue-grey breccia, and (4) vesicular, green-grey breccia. These lithologies correspond to samples 77215, 77075, 77115, and 77135, respectively. Two polished thin sections, 77075 and 77077, were loaned from the NASA Johnson Space Center. The mineralogy and microtextures of the samples were studiedbusing optical microscopy and analytical scanning electron microscopy, via energy dispersive spectrometry, with the purpose of determining the origin of the dikelets. Upon examination of the major element, trace element, and REE chemistry of the elastic dikelets and the noritic wallrock, it can be determined that the two Ethologies are not genetically related. Therefore, the dikelets were not derived from the noritic basalt wallrock but introduced as hot, fluidized injections of elastic, disaggregated material, possibly driven by hot vapour or gas generated during an impact event. The evolution of the station 7 boulder can be explained by either three or four impact cratering events. The three-impact hypothesis suggests that two impact events, followed by the Serenitatis event at 3.893 Ga, were responsible for the boulder evolution. The four-impact hypothesis suggests there were three pre-Serenitatis impact events that, together with the Serenitatis event, were responsible for the evolution of the station 7 boulder.