PGE, Re-Os, and Mo isotope systematics in Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth

2005 ◽  
Vol 69 (7) ◽  
pp. 1787-1801 ◽  
Author(s):  
C. Siebert ◽  
J.D. Kramers ◽  
Th. Meisel ◽  
Ph. Morel ◽  
Th.F. Nägler
Keyword(s):  
Redox Conditions ◽  
Early Earth ◽  
Early Proterozoic ◽  
Isotope Systematics

Granites and early Proterozoic crustal evolution in Sweden: evidence from SmNd, UPb and O isotope systematics

1985 ◽  
Vol 72 (4) ◽  
pp. 376-388 ◽  
Author(s):  
M.R. Wilson ◽  
P.J. Hamilton ◽  
A.E. Fallick ◽  
M. Aftalion ◽  
A. Michard
Keyword(s):  
Crustal Evolution ◽  
Early Proterozoic ◽  
O Isotope ◽  
Isotope Systematics

Isotopic evidence for the extent of early Proterozoic basement in Scotland and northwest Ireland

1991 ◽  
Vol 128 (4) ◽  
pp. 385-388 ◽  
Author(s):  
A. P. Dickin ◽  
D. R. Bowes
Keyword(s):  
Nd Isotope ◽  
Early Proterozoic ◽  
Isotopic Evidence ◽  
Gneiss Complex ◽  
Proterozoic Basement ◽  
Western Ireland ◽  
Isotope Systematics

AbstractTightly clustered Sm–Nd model ages, with an average of 1.96±0.02Ga, for the gneiss complex of Inishtrahull indicate coeval development with the earlyProterozoic gneiss terrane of Islay. The extent of this terrane, largely beneath the Dalradian Supergroup, is argued to be 100×600 km, from northeast Scotland to western Ireland. This is based on the distribution of dated basement in conjunction with Pb, Sr and Nd isotope systematics and inherited zircons in Caledonian granites of the region.

scholarly journals Chromium isotopes as a proxy for redox conditions on early Earth: Insights from Australian sedimentary rock records

2021 ◽  
Author(s):  
Juraj Farkas ◽  
Robert Klaebe ◽  
Geremiah Toledo ◽  
Jessica Stromberg ◽  
Sam Spinks ◽  
...  
Keyword(s):  
Sedimentary Rock ◽  
Redox Conditions ◽  
Early Earth

scholarly journals Redox control on chromium isotope behaviour in silicate melts in contact with magnesiochromite

2020 ◽  
Author(s):  
Pierre Bonnand ◽  
Emilie Bruand ◽  
Andrew Matzen ◽  
Matthew Jerram ◽  
Federica Schiavi ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Redox Conditions ◽  
Silicate Melt ◽  
Silicate Melts ◽  
Early Earth ◽  
Isotopic Compositions ◽  
High Temperature Processes ◽  
Lower Oxygen ◽  
Volatile Loss ◽  
Over Time

<p>Transition metals are of special interest for understanding the conditions of differentiation processes such as core formation. Those that have more than one oxidation state can also provide powerful constraints on changing redox conditions in the mantle over time. The ability to determine isotopic fractionations associated with differentiation processes has provided a new dimension to exploration of the conditions in the early Earth in particular. It has been recently shown that Cr isotope variations in igneous systems are strongly affected by redox conditions and chromite crystallisation.</p><p>In this study, we have investigated the variations in chemical composition and Cr isotopic compositions in both magnesiochromite and silicate melts during experiments performed under controlled redox conditions. The Cr isotopic compositions measured in the silicate melts in our experiments are strongly influenced by oxygen fugacity and experiments performed at 1300 °C and -12 < logfO<sub>2</sub> < -6 are correlated with fO<sub>2</sub>. This suggests that Cr isotopes are a powerful tool to study changes in redox conditions in high temperature processes. The Cr isotopic composition of silicate melt reacted under more oxidising conditions (logfO<sub>2</sub> > -6) are isotopically much lighter compared to melts reacted at lower oxygen fugacity. Three hypotheses are proposed to explain such variations: (i) a change in Cr bonding environment in the silicate melt (ii) a change in Cr bonding environment in the chromite (iii) volatile loss of Cr from the silicate melt. More work is needed to definitively determine the factors that control the isotopic behaviour of Cr in silicate melts.</p>

scholarly journals 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

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130246 ◽  
Author(s):  
Richard W. Carlson ◽  
Lars E. Borg ◽  
Amy M. Gaffney ◽  
Maud Boyet
Keyword(s):  
Source Region ◽  
Early Earth ◽  
Lunar Crust ◽  
Crust Formation ◽  
Crustal Rocks ◽  
Incompatible Elements ◽  
Isotopic Analyses ◽  
History Of ◽  
Isotope Systematics ◽  
Source Materials

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.

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