The combined Lu-Hf and Sm-Nd mineral-whole rock, and zircon U-Pb, REE and Hf isotope study of ultra high pressure rocks from the CCSD program
Zusammenfassung der Projektergebnisse
Ultrahigh pressure (UHP) rocks from the Chinese Continental Scientific Drilling (CCSD) program were chosen to study the trace element and Lu-Hf isotope systems in combination with U-Th-Pb dating of distinct zircon domains. The results show that the combined use of trace element and U-Th-Pb isotope compositions of zircon and PT information from their mineral inclusions, allow the linkage between U-Pb ages and metamorphic reactions. Inherited and metamorphic zircons were distinguished based on cathodoluminescence imaging, mineral inclusions, trace element contents and Hf isotope composition. Up to three phases of zircon growth or re-crystallisation can be identified in a single sample. The ages are interpreted to date the time of 1) prograde and 2) UHP metamorphism during Middle Triassic subduction, and 3) retrograde metamorphism during Late Triassic exhumation. The Sulu orogen can be divided from south-east to north-west in a high-pressure crustal slice and two different ultrahigh-pressure crustal slices. All three crustal slices underwent different subduction and exhumation histories. Studies of the Hf isotope analyses of UHP zircon domains from different samples give new insights in the understanding of the behavior of the Lu-Hf system during UHP metamorphism. Inherited zircons of mainly middle Neoproterozoic ages have variable trace element pattern that are considerably different from those of metamorphic zircon domains. Lu-Hf and Sm-Nd grt-cpx isochrones from CCSD and Dabie eclogites yield surprisingly uniform ages that are in average about 6-8 Myr younger than the UHP zircon age. Why the different chronometers yield distinct ages could not been finally clarified.
Projektbezogene Publikationen (Auswahl)
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2006. SHRIMP U-Pb zircon dating from Sulu-Dabie dolomitic marble, eastern China: constraints on prograde, ultrahigh-pressure and retrograde metamorphic ages. Journal of Metamorphic Geology, Vol. 24. 2006, Issue 7, pp. 569–589.
Liu F.L., Gerdes A., Liou J.G., Xue H., Liang F.H.
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2007. Zoned zircon from eclogite lenses in marbles from the Dabie-Sulu UHP terrane, China: A unique record of ultra-deep subduction and fast exhumation. Acta Geologica Sinica (English Edition), Vol. 81. 2007, Issue 2, pp. 204–225.
Liu F.L., Gerdes A., Robinson P., Xue H.M., Ye J.G.
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2008. Rapid eclogitisation of the Dabie–Sulu UHP terrane: Constraints from Lu–Hf garnet geochronology. Earth and Planetary Science Letters, Vol. 273. 2008, Issues 1–2, pp. 203–213.
Schmidt, A., Weyer, S., Mezger, K., Scherer, E. E., Xiao, Y., Hoefs, J., & Brey, G. P.
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2008. SHRIMP U-Pb dating, trace element and the Lu-Hf isotope systematic of coesite-bearing zircon from amphibolite in SW Sulu UHP terrane, eastern China. Geochimica et Cosmochimica Acta, Vol. 72. 2008, Issue 12, pp. 2973–3000.
Liu F.L., Gerdes A., Zeng L., Xue H.
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2009. Unique coesite-bearing zircon from allanite-bearing gneisses: U-Pb, REE and Lu-Hf properties and implications for the evolution of the Sulu UHP terrane, China. European Journal of Mineralogy, Vol. 21. 2009, Number 6, pp. 1225-1250.
Liu F.L., Gerdes A., Liou, J.G., Liu, P.H.
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2010. Differential subduction and exhumation of crustal slices in the Sulu HP-UHP metamorphic terrane: insights from mineral inclusions, trace elements, U-Pb and Lu-Hf isotope analyses of zircon in orthogneiss. Journal of Metamorphic Geology, Vol. 27. 2009 Issue 9, pp. 805–825.
Liu F.L., Gerdes A., Xue H.M.
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2010. Zircon U-Pb ages, REE concentrations and Hf isotope compositions of granitic leucosome and pegmatite from the north Sulu UHP terrane in China: Constraints on the timing and nature of partial melting. Lithos, Vol. 117. 2010, Issues 1–4, pp. 247–268.
Liu F.L., Robinson P.T., Gerdes A., Xue, H.M., Liu, P.H., Liou, J.G.,
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2012. U-Pb, trace element and Lu-Hf properties of unique dissolution-recrystallization zircon from UHP eclogite in SW Sulu terrane, eastern China. Gondwana Research, Vol. 22. 2012, Issue 1, pp. 169–183.
Liu, F.L., Gerdes, A., Liu, P.H.
