Continental and Oceanic Crust Recycling-induced Melt-Peridotite Interactions in the Trans-North China Orogen: U-Pb Dating, Hf Isotopes and Trace Elements in Zircons from Mantle Xenoliths
Top Cited Papers
Open Access
- 16 December 2009
- journal article
- Published by Oxford University Press (OUP) in Journal of Petrology
- Vol. 51 (1-2), 537-571
- https://doi.org/10.1093/petrology/egp082
Abstract
We present the first finding of continental crust-derived Precambrian zircons in garnet/spinel pyroxenite veins within mantle xenoliths carried by the Neogene Hannuoba basalt in the central zone of the North China Craton (NCC). Petrological and geochemical features indicate that these mantle-derived composite xenoliths were formed by silicic melt–lherzolite interaction. The Precambrian zircon ages can be classified into three age groups of 2·4–2·5 Ga, 1·6–2·2 Ga and 0·6–1·2 Ga, coinciding with major geological events in the NCC. These Precambrian zircons fall in the field of continental granitoid rocks in plots of U/Yb vs Hf and Y. Their igneous-type REE patterns and metamorphic zircon type CL images indicate that they were not crystallized during melt–peridotite interaction and subsequent high-pressure metamorphism. The ∼2·5 Ga zircons have positive εHf(t) values (2·9–10·6), whereas the younger Precambrian zircons are dominated by negative εHf(t) values, indicating an ancient continental crustal origin. These observations suggest that the Precambrian zircons were xenocrysts that survived melting of recycled continental crustal rocks and were then injected with silicate melt into the host peridotite. In addition to the Precambrian zircons, igneous zircons of 315 ± 3 Ma (2σ), 80–170 Ma and 48–64 Ma were separated from the garnet/spinel pyroxenite veins; these provide evidence for lower continental crust and oceanic crust recycling-induced multi-episodic melt–peridotite interactions in the central zone of the NCC. The combination of the positive εHf(t) values (2·91–24·6) of the 315 Ma zircons with the rare occurrence of 302–324 Ma subduction-related diorite–granite plutons in the northern margin of the NCC implies that the 315 Ma igneous zircons might record melt–peridotite interactions in the lithospheric mantle induced by Palaeo-Asian oceanic crust subduction. Igneous zircons of age 80–170 Ma generally coexist with the Precambrian metamorphic zircons and have lower Ce/Yb and Th/U ratios, higher U/Yb ratios and greater negative Eu anomalies. The εHf(t) values of these zircons vary greatly from –47·6 to 24·6. The 170–110 Ma zircons are generally characterized by negative εHf(t) values, whereas the 110–100 Ma zircons have positive εHf(t) values. These observations suggest that melt–peridotite interactions at 80–170 Ma were induced by partial melting of recycled continental crust. The 48–64 Ma igneous zircons are characterized by negligible Ce anomalies, unusually high REE, U and Th contents, and positive εHf(t) values. These features imply that the melt–peridotite interactions at 48–64 Ma could be associated with a depleted mantle-derived carbonate melt or fluid.Keywords
This publication has 109 references indexed in Scilit:
- The Hf isotopic composition of zircon reference material 91500Chemical Geology, 2008
- Lu–Hf, in-situ Sr and Pb isotope and trace element systematics for mantle eclogites from the Diavik diamond mine: Evidence for Paleoproterozoic subduction beneath the Slave craton, CanadaEarth and Planetary Science Letters, 2007
- Speculations on the nature and cause of mantle heterogeneityTectonophysics, 2006
- Evidence for crustal components in the mantle and constraints on crustal recycling mechanisms: pyroxenite xenoliths from Hannuoba, North ChinaChemical Geology, 2002
- Thermal and petrological structure of the lithosphere beneath Hannuoba, Sino-Korean Craton, China: evidence from xenolithsLithos, 2001
- Two contrasting paleozoic magmatic belts in northern Inner Mongolia, China: petrogenesis and tectonic implicationsTectonophysics, 2000
- Relationships between Lu–Hf and Sm–Nd isotopic systems in the global sedimentary systemEarth and Planetary Science Letters, 1999
- Opening and Tectonic Evolution of the Paleo-Asian OceanInternational Geology Review, 1995
- Isotopic evidence from the Ivrea Zone for a hybrid lower crust formed by magmatic underplatingNature, 1990
- Assimilation of Ultramafic Rock in Subduction-Related Magmatic ArcsThe Journal of Geology, 1986