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Experimental investigation of Apollo 16 “Rusty Rock” alteration by a lunar fumarolic gas
  • Christian J. Renggli,
  • Stephan Klemme
Christian J. Renggli
Institut für Mineralogie, Universität Münster, Institut für Mineralogie, Universität Münster

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Stephan Klemme
University of Muenster, University of Muenster
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The Apollo 16 sample 66095, named „Rusty Rock”, is enriched in volatile and moderately volatile elements. The impact melt breccia is characterized by the abundant occurrence of Fe-rich sulfide and chloride alteration phases, including FeS, ZnS and FeCl2. These phases have previously been interpreted to be the result of fumarolic alteration of the breccia. Here we present the results of two different experimental approaches, which aim to constrain the temperature conditions and the process under which the „Rusty Rock” alteration formed. The first experimental set-up assumes that the metals Zn, Cu and Fe were introduced into the rock by a C-O-S-Cl gas phase, and that the Fe-rich sulfides and chlorides were deposited from this gas phase. This “gas deposition” experiment suggests that the alteration assemblage formed over the temperature range of 538-638±5 °C. The second experimental set-up simulates a scenario, where Fe metal particles in the lunar rock react with a Zn-C-O-S-Cl gas phase at six different temperatures between 396±5 °C and 1005±5 °C. This latter “metal reaction” experiment resulted in the formation of sulfide and chloride coatings on the Fe metal chips. The „Rusty Rock” alteration phases FeCl2 and (Zn,Fe)S were abundantly present in the coating of the Fe metal chip reacted at 580±5 °C. Both experiments lead to results which are in agreement, providing a temperature of 580 ± 50 °C for the fumarolic alteration on the Moon, as observed in the Apollo 16 „Rusty Rock”.
Feb 2021Published in Journal of Geophysical Research: Planets volume 126 issue 2. 10.1029/2020JE006609