Re–Os isotope evidence for the composition, formation and age of the lower continental crust

Nature ◽  
10.1038/29966 ◽  
1998 ◽  
Vol 393 (6680) ◽  
pp. 58-61 ◽  
Author(s):  
A. E. Saal ◽  
R. L. Rudnick ◽  
G. E. Ravizza ◽  
S. R. Hart
Keyword(s):  
Continental Crust ◽  
Lower Continental Crust ◽  
Composition Formation ◽  
Isotope Evidence ◽  
Os Isotope

Os isotope systematics in Fogo Island: Evidence for lower continental crust fragments under the Cape Verde Southern Islands

2005 ◽  
Vol 219 (1-4) ◽  
pp. 93-113 ◽  
Author(s):  
Stéphane Escrig ◽  
Régis Doucelance ◽  
Manuel Moreira ◽  
Claude Jean Allègre
Keyword(s):  
Continental Crust ◽  
Cape Verde ◽  
Lower Continental Crust ◽  
Isotope Systematics ◽  
Os Isotope

New approaches to crustal evolution studies and the origin of granitic rocks: what can the Lu-Hf and Re-Os isotope systems tell us?

1996 ◽  
Vol 87 (1-2) ◽  
pp. 339-352 ◽  
Author(s):  
Clark M. Johnson ◽  
Steven B. Shirey ◽  
Karin M. Barovich
Keyword(s):  
Continental Crust ◽  
Isotope Ratios ◽  
Granitic Rocks ◽  
Nd Isotope ◽  
Volcanic Arcs ◽  
Depleted Mantle ◽  
Os Isotopes ◽  
Isotope System ◽  
Os Isotope

ABSTRACT:The Lu-Hf and Re-Os isotope systems have been applied sparsely to elucidate the origin of granites, intracrustal processes and the evolution of the continental crust. The presence or absence of garnet as a residual phase during partial melting will strongly influence Lu/Hf partitioning, making the Lu–Hf isotope system exceptionally sensitive to evaluating the role of garnet during intracrustal differentiation processes. Mid-Proterozoic (1·1–1·5Ga ) ‘anorogenic’ granites from the western U.S.A. appear to have anomalously high εHf values, relative to their εNd values, compared with Precambrian orogenic granites from several continents. The Hf-Nd isotope variations for Precambrian orogenic granites are well explained by melting processes that are ultimately tied to garnet-bearing sources in the mantle or crust. Residual, garnet-bearing lower and middle crust will evolve to anomalously high εHf values over time and may be the most likely source for later ‘anorogenic’ magmas. When crustal and mantle rocks are viewed together in terms of Hf and Nd isotope compositions, a remarkable mass balance is apparent for at least the outer silicate earth where Precambrian orogenic continental crust is the balance to the high-εHf depleted mantle, and enriched lithospheric mantle is the balance to the low-εHf depleted mantle.Although the continental crust has been envisioned to have exceptionally high Re/Os ratios and very radiogenic Os isotope compositions, new data obtained on magnetite mineral separates suggest that some parts of the Precambrian continental crust are relatively Os-rich and non-radiogenic. It remains unclear how continental crust may obtain non-radiogenic Os isotope ratios, and these results have important implications for Re-Os isotope evolution models. In contrast, Phanerozoic batholiths and volcanic arcs that are built on young mafic lower crust may have exceptionally radiogenic Os isotope ratios. These results highlight the unique ability of Os isotopes to identify young mafic crustal components in orogenic magmas that are essentially undetectable using other isotope systems such as O, Sr, Nd and Pb.

Formation and composition of the lower continental crust: Evidence from Scottish xenolith suites

1993 ◽  
Vol 98 (B1) ◽  
pp. 581-607 ◽  
Author(s):  
Alex N. Halliday ◽  
Alan P. Dickin ◽  
Robert N. Hunter ◽  
Gareth R. Davies ◽  
Tim J. Dempster ◽  
...  
Keyword(s):  
Continental Crust ◽  
Lower Continental Crust

Constraints on the seismic properties of the middle and lower continental crust

2011 ◽  
Vol 360 (1) ◽  
pp. 7-32 ◽  
Author(s):  
G. E. Lloyd ◽  
R. W. H. Butler ◽  
M. Casey ◽  
D. J. Tatham ◽  
D. Mainprice
Keyword(s):  
Continental Crust ◽  
Lower Continental Crust ◽  
Seismic Properties
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