Year: 2014
Type: article
Abstract: Data obtained from Sm‐Nd and Rb‐Sr isotopic measurements of lunar highlands’ samples are renormalized to common standard values and then used to define ages with a common isochron regression algorithm. The reliability of these ages is evaluated using five criteria that include whether: (1) the ages are defined by multiple isotopic systems, (2) the data demonstrate limited scatter outside uncertainty, (3) initial isotopic compositions are consistent with the petrogenesis of the samples, (4) the ages are defined by an isotopic system that is resistant to disturbance by impact metamorphism, and (5) the rare‐earth element abundances determined by isotope dilution of bulk of mineral fractions match those measured by in situ analyses. From this analysis, it is apparent that the oldest highlands’ rock ages are some of the least reliable, and that there is little support for crustal ages older than approximately 4.40 Ga. A model age for ur‐KREEP formation calculated using the most reliable Mg‐suite Sm‐Nd isotopic systematics, in conjunction with Sm‐Nd analyses of KREEP basalts, is 4389 ± 45 Ma. This age is a good match to the Lu‐Hf model age of 4353 ± 37 Ma determined using a subset of this sample suite, the average model age of 4353 ± 25 Ma determined on mare basalts with the 146Sm‐142Nd isotopic system, with a peak in Pb‐Pb ages observed in lunar zircons of approximately 4340 ± 20 Ma, and the oldest terrestrial zircon age of 4374 ± 6 Ma. The preponderance of ages between 4.34 and 4.37 Ga reflect either primordial solidification of a lunar magma ocean or a widespread secondary magmatic event on the lunar nearside. The first scenario is not consistent with the oldest ages reported for lunar zircons, whereas the second scenario does not account for concordance between ages of crustal rocks and mantle reservoirs.
DOI: 10.1111/maps.12373
Language: English
Topic: Astro and Planetary Science
Subfield: Space and Planetary Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
Awards: G1356433355, G1603079603, G2145270357, G2717806384, THIS PROPOSAL PRESENTS FOUR NEW SCIENCE TASKS FOR OUR RESEARCH TEAM: 1) A STUDY OF VALENCE STATE PARTITIONING OF EU CR AND V BETWEEN PYROXENE AND A MARTIAN BASALT AS AFUNCTION OF OXYGEN FUGACITY (IW-1 TO FMQ) AND CRYSTALLIZATION HISTORY 2) A COMPARATIVE PLANETARY MINERALOGY STUDY OF SULFIDES IN BASALTS TO GAIN A BETTER UNDERSTANDING OF CHALCOPHILE ELEMENT BEHAVIOR IN DIFFERENT PLANETARY ENVIRONMENTS 3) A RECONSTRUCTION OF THE PETROGENETIC HISTORY OF OLIVINE MEGACRYSTS IN MARTIAN BASALTS TO GAIN INSIGHTS INTO THE PETROGENESIS OF "DEPLETED" AND "ENRICHED" SHERGOTTITES AND 4) COMBINED SIMS-TIMS STUDIES OF MARTIAN AND LUNAR METEORITES TO GAIN ADDITIONAL INSIGHTS INTO THE ORIGIN AND EVOLUTION OF PLANETARY MANTLES AND THE GENERATION AND HISTORY OF BASALTS FROM THESE TWO PLANETS. OUR DIVERSE RESEARCH BACKGROUNDS IN CRYSTAL CHEMISTRY MINERALOGY PETROLOGY AND GEOCHEMISTRY PROVIDE A STRONG FOUNDATION TO USE AN INTEGRATED APPROACH TO SOLAR SYSTEM PROBLEMS. THIS BACKGROUND COMBINED WITH EXPERIMENTAL PETROLOGY LABORATORIES (UNM AND JSC WITH INDIVIDUAL AND INDIVIDUAL) ELECTRON MICROPROBE (EMP UNM) SECONDARY ION MASS SPECTROMETRY (SIMS UNM) NANO-SIMS (CALTECH WITH INDIVIDUAL) TRANSMISSION ELECTRON MICROSCOPY (TEM UNM) THERMAL IONIZATION MASS SPECTROMETRY (TIMS LLNL WITH INDIVIDUAL) FOCUSED ION BEAM MICROSCOPY (FIB UNM) SYNCHROTRON MICROXANES AND SYNCHROTRON X-RAY FLUORESCENCE (XANES AND SXRF RESPEVTIVELY NATIONAL SYNCHROTRON LIGHT SOURCE AT ARGONNE NATIONAL LABORATORY WITHINDIVIDUAL) ENABLES US TO USE INNOVATIVE APPROACHES TO THE STUDY OF SOLAR SYSTEM MATERIALS. THE TASKS OUTLINED IN THIS PROPOSAL HAVE HIGH RELEVANCE TO THE COSMOCHEMISTRY PROGRAM AND NASA'S GOALS FOR THE EXPLORATION OF THE SOLAR SYSTEM. FULFILLING THESE TASKS WILL PROVIDE INSIGHTS INTO THE ORIGIN OF TERRESTRIAL PLANETS AND PROCESSES INFLUENTIAL IN THEIR EVOLUTION. FURTHER THESE PROPOSED STUDIES ARE RELEVANT TO THE GOALS IDENTIFIED BY THE NRC NAC LEAG AND MEPAG FOR THE EXPLORATION OF THE MOON AND MARS., G3669113783, G895790057, G991281326
OpenAlex ID: W2006145646