| Autor: |
Söderlund, Ulf, Isachsen, Clark E., Bylund, Göran, Heaman, Larry M., Patchett, P. Jonathan, Vervoort, Jeff D., Andersson, Ulf B. |
| Předmět: |
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| Zdroj: |
Contributions to Mineralogy & Petrology; Sep2005, Vol. 150 Issue 2, p174-194, 21p |
| Abstrakt: |
The Palaeoproterozoic (1.90–1.60 Ga) crust of central Fennoscandia was intruded repeatedly by dolerite dikes and sills during the Neo- and Mesoproterozoic eons. We report 17 new baddeleyite U–Pb dates comprising six generations of dolerites (in Ma): The favoured tectonic model implies that the majority of these suites were related to active margin processes somewhere west (and possibly south) of the Fennoscandian Shield. Dolerite intrusions are interpreted to reflect discrete events of back-arc extension as the arc retreated oceanward. Initial Hf and Nd isotope compositions of the dolerite swarms fall between CHUR and normal-depleted mantle, and suggest a variably depleted and re-enriched mantle as the source for the here investigated 1.6 to 0.95 Ga old mafic rocks. Repeated recycling of older crustal components, mainly sediments (dominated by material with short residence ages) in earlier subduction systems may have been very efficient at producing geochemically and isotopically variably enriched lithospheric mantle sections beneath the Fennoscandian Shield. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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