The Valence States of 3d: Transition Elements in Apollo 11 and 12 Rocks

Abstract

The absorption spectra of Apollo 11 fine-grained rocks, 10017 and 10022 are due entirely to pyroxene minerals. Spectral bands due to Fe³⁺, Fe²⁺, Cr³⁺ and Ti⁴⁺ and Ti³⁺ are detected. Single crystals of olivine in rocks 12021 and 12018 show bands due to Fe³⁺, Fe²⁺, Cr³⁺, Ti³⁺, Mn³⁺, and Mn²⁺. Pyroxenes in the same rocks exhibit band maxima of the same cationic species as in the olivines. Spectral shifts are noted due to anisotrophy of the crystal structures.

Heating sections 10017, 10022, and 12018 from the rock interiors at 200–225°C for 2 h caused large decreases in the spectral intensity of Fe³⁺, Cr³⁺ and Ti³⁺, indicating the following reaction:

Fe³⁺ + Cr³⁺ + Ti³⁺ → Fe²⁺ + Cr²⁺ + Ti⁴⁺

This suggests that Fe³⁺, Cr³⁺ and (a portion of) Ti³⁺ are not in equilibrium. It is most probable that they were produced subsequent to the formation of the rocks by a combination of secondary ionization processes following cosmic ray bombardment and by trace radioactivity present in the rocks.

An orange glass, 150 μ in diam and 50 μ thick contained in brecciated rock, 10048.44, exhibited 15 identifiable absorption bands related to Fe²⁺, Cr³⁺, Ti³⁺, Mn³⁺ or Mn²⁺ ions.

Plagioclase in 12021.65 has perfect transmission over the region studied. The limit of Fe³⁺ is in the order of < 1 ppm and Fe²⁺, 1000 ppm or less in this plagioclase single crystal of dimensions 0.6 mm × 0.2 mm × 30 μ.