Petrology and geochemistry of spinel peridotite xenoliths from Hannuoba and Qixia, North China craton
Introduction
Archean cratons are underlain by mantle lithosphere that is thick, cold and refractory Jordan, 1975, Jordan, 1988, van der Hilst and McDonough, 1999. Such lithosphere has a high viscosity because it is cold and nearly anhydrous, and thus contributes significantly to craton stability Pollack, 1986, Hirth et al., 2000. However, not all regions of Archean-aged crust are underlain by such refractory mantle lithosphere, and these regions are characterized by a more protracted history of tectonism and magmatism than their cratonic counterparts. There are at least two possible reasons for the absence of thick mantle keels beneath Archean-aged crust: (1) they may have never formed, or (2) they may have formed but were subsequently removed.
An example of the first possibility is the Mojave terrain in SW U.S. Here, the crust has Paleoproterozoic to late Archean Nd model ages Bennett and DePaolo, 1987, Raymo and Calzia, 1998 but middle Proterozoic crystallization ages (Wooden and Miller, 1990). Mojavia is underlain by late Archean lithospheric mantle that is considerably more fertile and dense than typical cratonic mantle (Lee et al., 2001). Hence, this mantle lithosphere did not grow to the same thickness as that beneath Archean cratons. Lee et al. (2001) proposed that the thinner lithosphere beneath Mojavia failed to shield this small fragment of Archean lithosphere from tectonic reworking. This study demonstrated that thick lithospheric keels do not always form beneath Archean crust.
An example of the second possibility is the North China craton, where multiple lines of evidence (surface geology, xenolith studies, seismic and heat flow data) show that this craton formed with a thick lithospheric keel in the Archean that was subsequently removed (e.g., Menzies et al., 1993, Griffin et al., 1998). The timing and mechanisms of lithospheric mantle removal beneath the North China craton are yet to be fully understood.
The present paper reports the petrography, mineral chemistry, thermometry and major element compositions of spinel peridotite xenoliths from the Hannuoba and Qixia localities for which Os data have previously been reported (Gao et al., 2002). In addition, for the Hannuoba peridotites, we present trace element and Sr and Nd isotope geochemistry. We show that the Sr and Nd isotopes reflect recent metasomatic overprinting not related to the Tertiary hosts and that both Hannuoba and Qixia peridotites are indistinguishable in terms of their bulk compositions, despite the fact that their formation ages differ by nearly 2 billion years.
Section snippets
Geologic setting
The North China craton is divided into three regions based on geology, tectonic evolution and P–T–t paths of metamorphic rocks (Fig. 1; Kusky et al., 2001, Zhao et al., 2000, Zhao et al., 2001). The western block forms a stable platform composed of late Archean to Paleoproterozoic metasedimentary belts that unconformably overly Archean basement Wu et al., 1998, Li et al., 2000, Zhao et al., 2000. The latter consists of granulite facies tonalite–trondhjemite–granodiorite (TTG) gneiss and
Samples and previous work
The samples investigated here are spinel-facies peridotites from the Hannuoba and Qixia xenolith localities (Fig. 1). In this section, we review the xenolith associations at each locality and some results from previous investigations. A more complete discussion of previous results for the peridotite xenoliths, in the context of our new data, is provided in 6 Results, 7 Discussion.
Analytical methods
The xenoliths were sawn from their lava hosts and the cut surfaces were abraded with quartz in a sand blaster to remove any possible contamination from the saw blade. The samples were then disaggregated between thick plastic sheets with a rock hammer and reduced to powder using first an alumina disk mill followed by an alumina ring mill. A portion of the crushed fraction was sieved and clinopyroxene separates were handpicked under a binocular microscope to a purity of >98%. They were cleaned in
Hannuoba
The Hannuoba spinel-facies peridotites range from coarse- to medium-grained and have granuloblastic textures (Fig. 2). Most samples are massive, but a few show foliation defined by aligned spinel grains. In general, both clinopyroxene and orthopyroxenes are homogenous, showing no exsolution lamellae. All xenoliths show alteration along grain boundaries and fractures (typically pale brown serpentine), but the degree of alteration is highly variable from one sample to the next (Fig. 2). A
Whole rock major and trace element data
Major and trace element analyses of whole rock samples are reported in Table 3 and plotted in Fig. 3, Fig. 4, Fig. 5, Fig. 6. Both Hannuoba and Qixia peridotites show a considerable spread in major element compositions, ranging from fertile compositions approaching primitive mantle to refractory harzburgites with up to 45% MgO. These refractory compositions slightly overlap the compositional field of cratonic peridotites, as exemplified by samples from the Tanzanian craton Rudnick et al., 1994,
Origin of the peridotites and major element systematics
The major element, compatible and moderately incompatible trace element and mineral chemical data for the Hannuoba and Qixia spinel peridotite xenoliths reflect their origin as residues from variable degrees of partial melting of a primitive mantle composition Fig. 3, Fig. 4, Fig. 7. Based on major element systematics (Fig. 3; Table 3) and published experimental melting studies, these peridotites may reflect between 0% to 25% removal of a batch melt from a primitive mantle composition at
Conclusions
The data presented here, coupled with the previously published Os isotopic results for these same samples provide insights into the nature of the mantle lithosphere underlying the North China craton. The main conclusions are:
- (1)
The spinel peridoitite xenolith suites from Hannuoba and Qixia are compositionally indistinguishable from each other and yet markedly different from cratonic mantle lithosphere found beneath other Archean cratons.
- (2)
The lithospheric mantle beneath Hannuoba and Qixia formed by
Acknowledgements
We thank Mike Rhodes for providing some of the XRF whole rock analyses. David Lange and Phil Piccoli provided guidance in electron mircroprobe analyses. Trisha Fiore helped with electron microprobe analyses at Harvard and Xiao-min Liu with XRF and ICP–MS analyses in Xi'an. We thank Stephanie Schmidberger and an anonymous reviewer for very helpful comments. The EPMA used in this study at the University of Maryland was purchased with grants from Department of Defense-Army/ARO (DAAG 559710383) and
References (64)
- et al.
Depleted spinel harzburgite xenoliths in Tertiary dykes from east Greenland: restites from high degree melting
Earth and Planetary Science Letters
(1998) Compositional distinction between oceanic and cratonic lithosphere
Earth and Planetary Science Letters
(1989)- et al.
Thermal and petrological structure of the lithosphere beneath Hannuoba, Sino–Korean craton, China: evidence from xenoliths
Lithos
(2001) - et al.
The mineralogy, geochemistry and origin of lherzolite inclusions in Victorian basanites
Geochimica et Cosmochimica Acta
(1974) - et al.
Re–Os evidence for replacement of ancient mantle lithosphere beneath the North China craton
Earth and Planetary Science Letters
(2002) - et al.
Heat flow in the continental area of China: a new data set
Earth and Planetary Science Letters
(2000) - et al.
Seismic properties and densities of middle and lower crustal rocks exposed along the North China geoscience transect
Earth and Planetary Science Letters
(1996) - et al.
Geochemistry of lower crustal xenoliths from Neogene Hannuoba Basalt, North China craton: implications for petrogenesis and lower crustal composition
Geochimica et Cosmochimica Acta
(2001) - et al.
Composition of the earth
Chemical Geology
(1995) Cratonization and thermal evolution of the mantle
Earth and Planetary Science Letters
(1986)
Lower crustal xenoliths from Queensland, Australia: evidence for deep crustal assimilation and fractionation of continental basalts
Geochimica et Cosmochimica Acta
Small-scale Sr isotope investigation of clinopyroxenes from peridotite xenoliths by laser ablation MC–ICP–MS—implications for mantle metasomatism
Chemical Geology
Strontium and samarium diffusion in diopside
Geochimica et Cosmochimica Acta
Geochemistry of peridotite xenoliths in basalt from Hannuoba, Eastern China: implications for subcontinental mantle heterogeneity
Geochimica et Cosmochimica Acta
Isotopic characteristics of Hannuoba basalts, Eastern China—implications for their petrogenesis and the composition of subcontinental mantle
Chemical Geology
Sr, Nd and Pb isotopes of ultramafic xenoliths in volcanic rocks of Eastern China: enriched components EMI and EMII in subcontinental lithosphere
Earth and Planetary Science Letters
Hf–Nd–Sr isotopes and incompatible element abundances in island arcs: implications for magma origins and crust–mantle evolution
Earth and Planetary Science Letters
Evidence for crustal components in the mantle and constraints on crustal recycling mechanisms: pyroxenite xenoliths from Hannuoba, North China
Chemical Geology
A review of the geodynamic setting of large-scale Late Mesozoic gold mineralization in the North China craton: an association with lithospheric thinning
Ore Geology Reviews
Metamorphism of basement rocks in the Central Zone of the North China craton: implications for Paleoproterozoic tectonic evolution
Precambrian Research
Archean blocks and their boundaries in the North China craton: lithological, geochemical, structural and P–T path constraints and tectonic evolution
Precambrian Research
Geochemistry of Hannuoba basalts, eastern China—constraints on the origin of continental alkalic and tholeiitic basalt
Chemical Geology
Continental crust and lithospheric mantle interaction beneath North China: isotopic evidence from granulite xenoliths in Hannuoba, Sino–Korean craton
Lithos
Mantle cryptology
Geochimica et Cosmochimica Acta
Proterozoic crustal history of the western United States as determined by neodymium isotopic mapping
Geological Society of America Bulletin
Geothermobarometry in four-phase lherzolites: II. New thermobarometers, and practical assessment of existing thermobarometers
Journal of Petrology
Mantle xenoliths and alkali-rich host rocks in eastern China
The mineral chemistry of ultramafic xenoliths of Eastern China—implications for upper mantle composition and the paleogeotherms
Journal of Petrology
Zircon geochronology and rare earth element geochemistry of granulite xenoliths from Hannuoba
Chinese Science Bulletin
On and off the North China craton: where is the Archaean keel?
Journal of Petrology
Measured and calculated seismic velocities and densities for granulites from xenolith occurrences and adjacent exposed lower crustal sections: a comparative study from the North China craton
Journal of Geophysical Research, [Solid Earth]
1994 compilation of working values and sample description for 383 geostandards
Geostandards Newsletter
Cited by (554)
Deep mantle cycle of chalcophile metals and sulfur in subducted oceanic crust
2024, Geochimica et Cosmochimica ActaPreservation of Archean mafic lower continental crust worldwide
2024, Earth and Planetary Science LettersCircum-cratonic mantle archives the cumulative effects of plume and convergence events
2023, Geochimica et Cosmochimica Acta