Rb-Sr, Sm-Nd and Lu-Hf isotope systematics of the lunar Mg-suite: the age of the lunar crust and its relation to the time of Moon formation.
نویسندگان
چکیده
New Rb-Sr, (146,147)Sm-(142,143)Nd and Lu-Hf isotopic analyses of Mg-suite lunar crustal rocks 67667, 76335, 77215 and 78238, including an internal isochron for norite 77215, were undertaken to better define the time and duration of lunar crust formation and the history of the source materials of the Mg-suite. Isochron ages determined in this study for 77215 are: Rb-Sr=4450±270 Ma, (147)Sm-(143)Nd=4283±23 Ma and Lu-Hf=4421±68 Ma. The data define an initial (146)Sm/(144)Sm ratio of 0.00193±0.00092 corresponding to ages between 4348 and 4413 Ma depending on the half-life and initial abundance used for (146)Sm. The initial Nd and Hf isotopic compositions of all samples indicate a source region with slight enrichment in the incompatible elements in accord with previous suggestions that the Mg-suite crustal rocks contain a component of KREEP. The Sm/Nd-(142)Nd/(144)Nd correlation shown by both ferroan anorthosite and Mg-suite rocks is coincident with the trend defined by mare and KREEP basalts, the slope of which corresponds to ages between 4.35 and 4.45 Ga. These data, along with similar ages for various early Earth differentiation events, are in accord with the model of lunar formation via giant impact into Earth at ca 4.4 Ga.
منابع مشابه
A combinedSm–Nd, Rb–Sr, and U–Pb isotopic study of Mg-suite norite 78238: Further evidence for early differentiation of the Moon
Lunar Mg-suite norite 78238 was dated using the Sm–Nd, Rb–Sr, and U–Pb isotopic systems in order to constrain the age of lunar magma ocean solidification and the beginning of Mg-suite magmatism, as well as to provide a direct comparison between the three isotopic systems. The Sm–Nd isotopic system yields a crystallization age for 78238 of 4334 ± 37 Ma and an initial e Nd value of 0.27 ± 0.74. T...
متن کاملMARE BASALT PETROGENESIS REVISITED: Rb/Sr, Sm/Nd and Lu/Hf FRACTIONATION FACTORS, MANTLE SOURCE REGIONS AND CRUSTAL CONTAMINATION
Introduction: Many questions regarding the petrogenesis of mare basalts remain unresolved. Trace element and isotope geochemists tend to view the range of mare basalt compositional groups as independent primary magmas and develop mantle melting models to explain the compositional diversity [e.g. 1, 2, 3]. On the other hand, petrologists view the mare basalt suites as non-primary and suggest tha...
متن کاملThe origin of geochemical diversity of lunar mantle sources inferred from the combined U–Pb, Rb–Sr, and Sm–Nd isotope systematics of mare basalt 10017
The results of our combined U–Pb, Rb–Sr, and Sm–Nd isotope study of mare basalt 10017 contribute to the understanding of the petrogenetic processes involved in the origin of geochemical diversity in lunar mare basalt sources, as well as the U–Pb isotope systematics of the Moon. The Rb–Sr, Sm–Nd, and U–Pb isotope systems yield concordant crystallization ages of 3.633 ± 0.057 Ga, 3.678 ± 0.069 Ga...
متن کاملRe-evaluating Nd/Nd in lunar mare basalts with implications for the early evolution and bulk Sm/Nd of the Moon
The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Marssized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures ...
متن کاملNEW Nd EVIDENCE FOR A NON-CHONDRITIC COMPOSITION OF THE MOON
Introduction: The coupled Sm-Nd systematics of lunar samples has been extensively studied for estimating the timescale of lunar differentiation [1-3]. The published datasets yield consistent ages for Nd isotopic closure within the lunar mantle of ~200 Myr after CAI formation. Although this time constraint is consistent with estimates derived from Hf-W chronometry of the Moon (>60 Myr after CAI ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
دوره 372 2024 شماره
صفحات -
تاریخ انتشار 2014