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Title: A Low Viscosity Lunar Magma Ocean Forms a Stratified Anorthitic Flotation Crust With Mafic Poor and Rich Units: Lunar Magma Ocean Viscosity

Abstract

Much of the lunar crust is monomineralic, comprising >98% plagioclase. The prevailing model argues the crust accumulated as plagioclase floated to the surface of a solidifying lunar magma ocean (LMO). Whether >98% pure anorthosites can form in a flotation scenario is debated. An important determinant of the efficiency of plagioclase fractionation is the viscosity of the LMO liquid, which was unconstrained. Here we present results from new experiments conducted on a late LMO-relevant ferrobasaltic melt. The liquid has an exceptionally low viscosity of 0.22 $$+0.11\atop{-0.19}$$to 1.45 $$+0.46\atop{-0.82}$$ Pa s at experimental conditions (1,300–1,600°C; 0.1–4.4 GPa) and can be modeled by an Arrhenius relation. Extrapolating to LMO-relevant temperatures, our analysis suggests a low viscosity LMO would form a stratified flotation crust, with the oldest units containing a mafic component and with very pure younger units. Old, impure crust may have been buried by lower crustal diapirs of pure anorthosite in a serial magmatism scenario.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [2]
  1. Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin TX USA; Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Knoxville TN USA
  2. Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin TX USA
  3. HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL USA
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
DOE - BASIC ENERGY SCIENCESNSFDOE-NNSAUNIVERSITY
OSTI Identifier:
1418040
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geophysical Research Letters; Journal Volume: 44; Journal Issue: 22
Country of Publication:
United States
Language:
ENGLISH
Subject:
58 GEOSCIENCES

Citation Formats

Dygert, Nick, Lin, Jung-Fu, Marshall, Edward W., Kono, Yoshio, and Gardner, James E.. A Low Viscosity Lunar Magma Ocean Forms a Stratified Anorthitic Flotation Crust With Mafic Poor and Rich Units: Lunar Magma Ocean Viscosity. United States: N. p., 2017. Web. doi:10.1002/2017GL075703.
Dygert, Nick, Lin, Jung-Fu, Marshall, Edward W., Kono, Yoshio, & Gardner, James E.. A Low Viscosity Lunar Magma Ocean Forms a Stratified Anorthitic Flotation Crust With Mafic Poor and Rich Units: Lunar Magma Ocean Viscosity. United States. doi:10.1002/2017GL075703.
Dygert, Nick, Lin, Jung-Fu, Marshall, Edward W., Kono, Yoshio, and Gardner, James E.. Tue . "A Low Viscosity Lunar Magma Ocean Forms a Stratified Anorthitic Flotation Crust With Mafic Poor and Rich Units: Lunar Magma Ocean Viscosity". United States. doi:10.1002/2017GL075703.
@article{osti_1418040,
title = {A Low Viscosity Lunar Magma Ocean Forms a Stratified Anorthitic Flotation Crust With Mafic Poor and Rich Units: Lunar Magma Ocean Viscosity},
author = {Dygert, Nick and Lin, Jung-Fu and Marshall, Edward W. and Kono, Yoshio and Gardner, James E.},
abstractNote = {Much of the lunar crust is monomineralic, comprising >98% plagioclase. The prevailing model argues the crust accumulated as plagioclase floated to the surface of a solidifying lunar magma ocean (LMO). Whether >98% pure anorthosites can form in a flotation scenario is debated. An important determinant of the efficiency of plagioclase fractionation is the viscosity of the LMO liquid, which was unconstrained. Here we present results from new experiments conducted on a late LMO-relevant ferrobasaltic melt. The liquid has an exceptionally low viscosity of 0.22 $+0.11\atop{-0.19}$to 1.45 $+0.46\atop{-0.82}$ Pa s at experimental conditions (1,300–1,600°C; 0.1–4.4 GPa) and can be modeled by an Arrhenius relation. Extrapolating to LMO-relevant temperatures, our analysis suggests a low viscosity LMO would form a stratified flotation crust, with the oldest units containing a mafic component and with very pure younger units. Old, impure crust may have been buried by lower crustal diapirs of pure anorthosite in a serial magmatism scenario.},
doi = {10.1002/2017GL075703},
journal = {Geophysical Research Letters},
number = 22,
volume = 44,
place = {United States},
year = {Tue Nov 21 00:00:00 EST 2017},
month = {Tue Nov 21 00:00:00 EST 2017}
}