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A Renewed Search for Elusive Lunar GranophyresRecent remote sensing studies [e.g., 1-3] indicate that several un-sampled regions of the Moon have significantly higher concentrations of silicic material (also high in [K], [U], and [Th]) than sampled regions. Within these areas are morphological features that are best explained by the existence of chemically evolved volcanic rocks. Observations of silicic domes [e.g., 1-5] suggest that sizable networks of silicic melt were present during crust-formation. Because of these recent findings there is a renewed interest in the petrogenesis of lunar, felsic igneous rocks. Specific questions are: (1) when were these magmas generated?, and (2) what was the source material? The two main hypotheses for generating silicic melts on Earth are fractional crystallization or partial melting of preexisting crust. On the Moon silicic melts are thought to have been generated during extreme fractional crystallization involving end-stage silicate liquid immiscibility (SLI) [e.g. 6, 7]. However, SLI cannot account for the production of significant volumes of silicic melt and its wide distribution, as reported by the remote global surveys [1, 2, 3]. In addition, experimental and natural products of SLI show that U and Th, which are abundant in the lunar granites and seen in the remote sensing data of the domes, are preferentially partitioned into the depolymerized ferrobasaltic magma and not the silicic portion [8, 9]. If SLI is not the mechanism that generated silicic magmas on the Moon then alternative processes such as fractional crystallization (only crystal-liquid separation) or partial melting should be considered as viable possibilities to be tested.
Document ID
20130010074
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Mills, R. D. (NASA Johnson Space Center Houston, TX, United States)
Ross, D. K. (Jacobs Technologies Engineering Science Contract Group Houston, TX, United States)
Simon, J. I. (NASA Johnson Space Center Houston, TX, United States)
Irving, A. J. (Washington Univ. United States)
Date Acquired
August 27, 2013
Publication Date
January 1, 2013
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
JSC-CN-27971
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: The Woodlands, TX
Country: United States
Start Date: March 18, 2013
End Date: March 22, 2013
Sponsors: Lunar and Planetary Inst.
Distribution Limits
Public
Copyright
Public Use Permitted.

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