Element diffusion rates in lunar granulitic breccias: Evidence for contact metamorphism on the Moon
-
Jillian A. Hudgins
and
Christopher D. Hawkes
Abstract
Lunar granulitic breccias are a group of clast-bearing impact-melt lithologies that have been brecciated, and then metamorphosed at high temperature (-1000 °C) to generate annealed (granoblastic to poikiloblastic) textures. They are ubiquitous among lunar samples, but occur in small volumes, typically as clasts in other lunar rocks. We have determined major, minor, and trace element diffusion profiles in olivines, orthopyroxenes, and clinopyroxenes from one Apollo 16 (60035), three Apollo 17 (77017, 78155, 79215), and two paired lunar meteorites (NWA 3163 and NWA 4881) by means of electron microscopy and electron probe microanalysis. The results show that relic igneous clasts exhibit an absence of, or limited, major element zoning, yet retain minor and trace element profiles. We exploit this characteristic to estimate the duration of high-temperature metamorphism responsible for their recrystallization. To achieve this we have completed pyroxene thermometry, element linescans, X‑ray mapping, and modeling of heating and cooling of hanging wall and footwall lithologies juxtaposed with a hot body. The high equilibration temperatures, moderately high siderophile contents, and time scales of metamorphism of the lunar granulites indicate that they were metamorphosed in relatively near-surface settings. Diffusion calculations indicate that most granulitic breccias were heated for 13 000-300 000 yr. We conclude that they formed above or beneath superheated impact-melt sheets associated with medium-size (100-200 km) craters.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- In situ stress-strain measurements in a deformation-DIA apparatus at P-T conditions of the upper part of the mantle transition zone
- Element diffusion rates in lunar granulitic breccias: Evidence for contact metamorphism on the Moon
- The crystal structure of franckeite, Pb21.7Sn9.3Fe4.0Sb8.1S56.9
- Ammonium vermiculite in schists from the Betic Cordillera (Spain)
- Natrolite is not a “soda-stone” anymore: Structural study of alkali (Li+), alkaline-earth (Ca2+, Sr2+, Ba2+) and heavy metal (Cd2+, Pb2+, Ag+) cation-exchanged natrolites
- Analysis of hydrogen in olivine by SIMS: Evaluation of standards and protocol
- New accurate elastic parameters for the forsterite-fayalite solid solution
- In-situ mid/far micro-FTIR spectroscopy to trace pressure-induced phase transitions in strontium feldspar and wadsleyite
- Structural study of the coherent dehydration of wadsleyite
- An atomic force microscopy study of diamond dissolution features: The effect of H2O and CO2 in the fluid on diamond morphology
- Unraveling the stacking structure in tubular halloysite using a new TEM with computer-assisted minimal-dose system
- High-pressure structural behavior of α-Fe2O3 studied by single-crystal X-ray diffraction and synchrotron radiation up to 25 GPa
- The IR vibrational properties of six members of the garnet family: A quantum mechanical ab initio study
- On the presence of OH defects in the zircon-type phosphate mineral xenotime, (Y,REE)PO4
- Cesium and strontium incorporation into zeolite-type phases during homogeneous nucleation from caustic solutions
- Electrical conductivity of albite at high temperatures and high pressures
- Crystal-chemical and structural characterization of fluorapatites in ejecta from Somma-Vesuvius volcanic complex
- In situ ion-microprobe determination of trace element partition coefficients for hornblende, plagioclase, orthopyroxene, and apatite in equilibrium with natural rhyolitic glass, Little Glass Mountain Rhyolite, California
- In situ FTIR investigations at varying temperatures on hydrous components in rutile
- Methods to analyze metastable and microparticulate hydrated and hydrous iron sulfate minerals
- Crystal chemistry of Ti-rich ferriallanite-(Ce) from Cape Ashizuri, Shikoku Island, Japan
- Replacement of pyrrhotite by pyrite and marcasite under hydrothermal conditions up to 220 °C: An experimental study of reaction textures and mechanisms
- Argandite, Mn7(VO4)2(OH)8, the V analogue of allactite from the metamorphosed Mn ores at Pipji, Turtmann Valley, Switzerland
- Murchisite, Cr5S6, a new mineral from the Murchison meteorite
