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Comment on “Petrogenesis of post-orogenic syenites in the Sulu orogenic belt, east China: Geochronological, geochemical and Nd–Sr isotopic evidence” by Yang et al.
Chemical Geology 235 (2006) 191 – 194 www.elsevier.com/locate/chemgeo
Comment on “Petrogenesis of post-orogenic syenites in the Sulu orogenic belt, east China: Geochronological, geochemical and Nd–Sr isotopic evidence” by Yang et al. Zhi Xie ⁎, Quanzhong Li, Tianshan Gao CAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, AH 230026, PR China Received 22 November 2005; received in revised form 19 May 2006; accepted 24 May 2006 Editor: R.L. Rudnick
Keywords: Break-off; Pb Isotope; Dabie-Sulu orogenic belt; North China craton; Yangtze; Jianzishan
The Jiazishan complex is the only alkaline complex closely related to the continental collision between the North China and Yangtze cratons in the Sulu ultrahigh pressure metamorphic (UHPM) belt, eastern China. Recently, Yang et al. (2005) provided a petrogenetic model for the complex in which the parent magma was generated from melting subducted lithospheric mantle of the Yangtze craton. We believe that Pb isotopic data, not considered by Yang et al. (2005), are inconsistent with this hypothesis. We instead suggest that this complex formed from melts of North China craton lithospheric mantle that formed in response to slab break-off and accompanying asthenospheric upwelling. Our parallel study on the Jiazishan complex (Gao et al., 2004) found virtually the same trace element and Sr–Nd isotopic characteristics as Yang et al. (2005), such as enrichment in LILE and LREE and depletion in HFSEs, εNd(t) = − 13.6 to − 16.2, 87Sr/86Sr(t) = 0.7029–0.7067, suggesting that the complex was derived from an enriched lithospheric mantle. However, the geochemical data, esDOI of original article: 10.1016/j.chemgeo.2005.07.006. ⁎ Corresponding author. Tel.: +86 551 3607656; fax: +86 551 3607386. E-mail address: [email protected] (Z. Xie). 0009-2541/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.chemgeo.2006.05.012
pecially Pb isotopic data, do not support the hypothesis that the complex derived from partial melting of subducted Yangtze lithospheric mantle. The distinctive Pb isotopic data suggest that the complex was derived from the overlying North China craton during the Late Triassic. In the Late Mesozoic (about 120 to 160 Ma), lithospheric mantle beneath the North China and Yangtze cratons shared similar trace element characteristics, but different Sr–Nd–Pb isotopic ratios. In the central North China craton (that is, in the Jinan, Zouping and Taihangshan regions) where the sub-continental mantle was little affected by subducted materials from the Yangtze craton, the lithospheric mantle had an EM I character (Guo et al., 2001; Zhang et al., 2004). However, further south, Late Mesozoic basalts and mafic rocks from the MidLower Yangtze region and Dabie terrane had EM II type Sr–Nd isotopic characteristics (Li et al., 1998; Jahn et al., 1999; Chen et al., 2001; Xie et al., 2003). Along the southern margin of the North China craton, the lithospheric mantle also possesses EM II like Sr–Nd characteristics, such as shown by the Fangcheng basalt (Zhang et al., 2002). This is interpreted to be due to the involvement of the subducted Yangtze lithosphere (Jahn et al., 1999; Zhang et al., 2002, 2004). However, Sr–Nd isotopes are not diagnostic of the source of the Jiazishan complex, since
192
Z. Xie et al. / Chemical Geology 235 (2006) 191–194
Fig. 1. 206Pb/204Pb vs. 207Pb/204Pb plot for feldspars from the Jiazishan complex, compared with Late Mesozoic (120–160 Ma) basaltic and mafic intrusive rocks from the Yangtze and North China cratons. (Data of North China craton are from Zhang et al., 2004; Xie et al., unpublished data. Data of Yangtze craton and Fangcheng basalt are from Chen et al., 2001; Zhang et al., 2002; Yan et al., 2003,2005; Xie et al., unpublished data. Data of Dabie mafic rocks are from Wang et al., 2005; Xie et al. unpublished data). The fields of DMM, EM I, EM II and NHRL are taken from Zindler and Hart (1986), Pb evolution lines from Zartman and Doe (1981).
the Jiazishan data plot between the Yangtze and North 87 86 China craton fields in the εNd(t) vs. Sr/ Sr(t) plot (Yang et al., 2005; Gao et al., 2004). The distinction between the Mesozoic lithospheric mantle from the North China and Yangtze cratons is most clearly seen from Pb isotopes. The subcontinental lithospheric mantle of the Yangtze craton and the southern margin of the North China craton where it was affected by the subducted Yangtze materials have high 206 Pb/ 204 Pb > 17.50, reflecting a mixing of depleted mantle and EM II end members (Fig. 1; Chen et al., 2001; Zhang et al., 2002; Yan et al., 2003, 2005; Xie et al., unpublished data). In the central North China craton, mafic rocks show low 206Pb/204Pb < 17.5 (Fig. 1; Zhang et al., 2004; Xie et al., unpublished data). The low 207Pb/204Pb ratios (about 15.2–15.3) of these rocks suggest that assimilation of the lower crust cannot be entirely eliminated. The isotopic data for the Jiazishan complex are similar to those of the North Dabie terrane (Fig.1, this work; Gao et al., 2004,Yang et al., 2005). These similarities can be explained by a continental collisionwedging mode (Li and Yang, 2003; Wang et al., 2005), in which the lower crust and the lithospheric mantle on the southern margin of the North China craton wedged into the north margin of the Yangtze craton shortly after Triassic collision. The process caused a decoupling of the surface and subsurface geology in the Dabie-Sulu region. The subcontinental lithospheric mantle beneath the North Dabie terrane has characteristics of the North China craton, although surface rocks show Yangtze craton characteristics. The low 206 Pb/ 204 Pb ratios (< 17.3) of the mafic–ultramafic intrusions that crop
out in the northern part of the Dabie orogen suggest that lithospheric mantle underneath the northern Dabie has an affinity with the North China subcontinental lithosphere (Wang et al., 2005; Xie et al., unpublished data). Pb isotopic ratios of the Jiazishan complex (Table 1; 206 Pb/204Pb = 16.33–16.46; 207Pb/204 Pb = 15.37–15.43; 206 Pb/204Pb = 36.80–37.10) are significantly different from those of the Yangtze lithospheric mantle, and are similar to those of mafic rocks from the central North China craton Table 1 Pb isotopic ratios of feldspars from the Jiazishan complex Sample no. Lithology
206
207
208
02SD401 02SD402 02SD407 01SD178
16.416 16.417 16.464 16.457
15.427 15.406 15.423 15.382
36.911 36.861 37.101 36.902
16.432
15.368
36.877
16.455
15.374
36.872
16.345 16.328
15.399 15.416
36.800 36.835
02SD405 02SD408 01SD187 01SD192
Gabbro Gabbro Gabbro Pyroxene syenite Pyroxene syenite Pyroxene syenite Quartz syenite Granite
Pb/204Pb
Pb/204Pb
Pb/204Pb
Pb isotopic measurements were performed in the CAS Key Laboratory of Crust–Mantle Materials and Environments. Pb was separated by chromatography on Bio-Rad AG-1 × 8 anion exchange resin. Pb was loaded in 1.5 mol/L HCl + 0.65 mol/L HBr solution and then eluted using 1.0 mol/L HNO3. Pb isotopic ratios were analyzed on a Finnigan MAT-262 multi-collector thermal ionization mass spectrometer by static mode. Measured isotopic ratios were corrected for a mass fractionation of 0.01% per atomic mass unit determined by replicate measurements of reference material SRM 981. The ratios listed in the table were corrected for the minor in situ radiogenic component.
Z. Xie et al. / Chemical Geology 235 (2006) 191–194
and Dabie orogen, having a clear EM I affinity (Fig. 1) noted by Zindler and Hart (1986) to be characterized by unradiogenic 206Pb/204Pb ratios. Therefore, the Pb isotopic data suggest that the Jiazishan complex is not derived from the subducted Yangtze plate, but from the overlying North China plate. Two tectonic models have been suggested to explain the formation of the Jiazishan complex: partial melting of the overlying mantle wedge after the break-off of the subducted plate (Chen et al., 2003) and partial melting of the subducted slab resulting from lithospheric removal and crustal extension (Yang et al., 2005). Among many criteria that can be used to discriminate the two models, the source of the parent magma is crucial. According to the break-off model, when the Yangtze lithosphere was subducted towards the North China craton during the Triassic, opposing buoyancy forces led to extensional deformation in the subducted slab and slab break-off. Following the break-off, upwelling hot asthenospheric mantle intruded into the narrow rift, resulting in partial melting of the overlying North China lithospheric mantle, but not the subducted slab itself, thus forming the K-rich Jiazishan complex. The obvious similarity of Pb isotopic characteristics between the Jiazishan complex and North China craton clearly supports this model. In contrast, Yang et al. (2005) suggested that the complex was derived from lithospheric mantle of the subducted Yangtze craton, which melted during post-orogenic extension. Based on this model, the complex should share similar Pb isotopic characteristics with the Yangtze lithosphere (206 Pb/ 204 Pb = 17.649–18.603, 207 Pb/204 Pb = 15.422–15.623, 208 Pb/204Pb = 37.674–38.521; Chen et al., 2001; Yan et al., 2003, 2005; Xie, unpublished data). However, this is not the case (Table 1). Therefore, we strongly argue that the Jiazishan complex is formed by slab break-off, but not by post-orogenic extension. The break-off model has also been supported by many geochronological and geochemical works for Dabie-Sulu UHPM rocks (Li et al., 2000, 2005; Liu et al., 2004). Acknowledgement We are grateful to Dr. Roberta Rudnick for the helpful reviews on the early version of the manuscript. This work is supported by the National Science Foundation of China (40203004). References Chen, J.F., Yan, J., Xie, Z., Xu, X., Xing, F.M., 2001. Nd and Sr isotopic compositions of igneous rocks from the Lower Yangtze region in eastern China: constraints on sources. Phys. Chem. Earth, Part A 26, 719–731.
193
Chen, J.F., Xie, Z., Li, H.M, Zhang, H.D., Zhou, T.X., Park, Y.S., Ahn, K.S., Chen, D.G., Zhang, X., 2003. U–Pb zircon ages for a collision-related K-rich complex at Shidao in the Sulu ultrahigh pressure terrane, China. Geochem. J. 37, 35–46. Gao, T.S., Chen, J.F., Xie, Z., Yan, J., Qian, H., 2004. Geochemistry of Triassic igneous complex at Shidao in the Sulu UHP metamorphic belt. Acta Petrol. Sin. 20, 1025–1038 (in Chinese with English abstract). Guo, F., Fan, W.M., Wang, Y.J., Lin, G., 2001. Late Mesozoic intrusive complexes in North China Block: constraints on the nature of subcontinental lithospheric mantle. Phys. Chem. Earth 26, 759–771. Jahn, B.M., Wu, F.Y., Lo, C.H., Tsai, C.H., 1999. Crust–mantle interaction induced by deep subduction of the continental crust: geochemical and Sr–Nd isotopic evidence from post-collisional mafic–ultramafic intrusions of the northern Dabie Complex, central China. Chem. Geol. 157, 119–146. Li, S.G., Yang, W., 2003. Decoupling of surface and subsurface sutures in the Dabie Orogen and a continent-collisional lithospheric-wedging model: Sr–Nd–Pb evidences of Mesozoic igneous rocks in eastern China. China Sci. Bull. 48, 831–838. Li, S.G., Nie, Y.H., Hart, S.R., Zhang, Z.Q., 1998. Interaction between subducted continental crust and the mantle. II. Sr and Nd isotopic geochemistry of syncollisional mafic–ultramafic intrusions in Dabie Mountains. Sci. China (Ser. D) 41, 632–638. Li, S.G., Jagoutz, E., Chen, Y.Z., Li, Q.L., 2000. Sm–Nd and Rb–Sr isotopic chronology and cooling history of ultrahigh pressure metamorhic rocks and their country rocks at Shuanghe in the Dabie terrain, central China. Geochim. Cosmochim. Acta 64, 1077–1093. Li, S.G., Li, Q.L., Hou, Z.H., Yang, W., Wang, Y., 2005. Cooling history and exhumation mechanism of the ultrahigh-pressuremetamorphic rocks in the Dabie mountains, central China. Acta Petrol. Sin. 21, 1117–1124 (in Chinese with English abstract). Liu, F.L., Xu, Z.Q., Liou, J.G., Song, B., 2004. SHRIMP ages of ultrahigh-pressure and retrograde metamorphism of gneisses, south-western Sulu terrane, eastern China. J. Met. Wang, Y.J., Fan, W.M., Peng, T.P., Zhang, H.F., Guo, F., 2005. Nature of the Mesozoic lithospheric mantle and tectonic decoupling beneath the Dabie orogen, central China: evidence from 40Ar/39Ar geochronology, elemental and Sr–Nd–Pb isotopic compositions of Early Cretaceous mafic igneous rocks. Chem. Geol. 220, 165–189. Xie, Z., Chen, J.F., Zhang, X., Zhou, T.X., 2003. Geochemistry of Early Cretaceous basalt in the Xiaotian Basin, North Huaiyang region: evidence of enriched mantle. Bull. Mineral. Petrol. Geochem. 22, 26–31 (in Chinese with English abstract). Yan, J., Chen, J.F., Yu, G., Qian, H., Zhou, T.X., 2003. Pb isotopic characteristics of Late Mesozoic mafic rocks from the Lower Yangtze region: evidence for enriched mantle. Geol. J. China Univ. 9, 195–206 (in Chinese with English abstract). Yan, J., Chen, J.-F., Xie, Z., Yang, G., Yu, G., Qian, H., 2005. Geochemistry of Late Mesozoic basalts from Kedoushan in the middle and lower Yangtze regions: constraints on characteristics and evolution of the lithospheric mantle. Geochimica 34, 455–469 (in Chinese with English abstract). Yang, J.H., Chung, S.L., Wilde, S., Wu, F.Y., Chu, M.F., Lo, C., Fan, H.R., 2005. Petrogenesis of post-orogenic syenites in the Sulu orogenic belt, east China: geochronological, geochemical and Nd–Sr isotopic evidence. Chem. Geol. 214, 99–125. Zartman, R.E, Doe, B.R., 1981. Plumbotectonics — the model. Tectonophysics 75, 135–162.
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Zhang, H.F., Sun, M., Zhou, X.H, Fan, W.M., Zhai, M.G., Yin, J.F., 2002. Mesozoic lithosphere destruction beneath the North China Craton: evidence from major-, trace-element and Sr–Nd–Pb isotope studies of Fangcheng basalts. Contrib. Mineral. Petrol. 144, 241–253. Zhang, H.F., Sun, M., Zhou, M.F., Fan, W.M., Zhou, X.H., Zhai, M.G., 2004. Highly heterogeneous Late Mesozoic lithospheric mantle
beneath the North China Craton: evidence from Sr–Nd–Pb isotopic systematics of mafic igneous rocks. Geol. Mag. 141, 53–62. Zindler, A., Hart, S., 1986. Chemical geodynamics. Annu. Rev. Earth Planet. Sci. 14, 493–571.
Comment on “Petrogenesis of post-orogenic syenites in the Sulu orogenic belt, east China: Geochronological, geochemical and Nd–Sr isotopic evidence” by Yang et al. Zhi Xie ⁎, Quanzhong Li, Tianshan Gao CAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, AH 230026, PR China Received 22 November 2005; received in revised form 19 May 2006; accepted 24 May 2006 Editor: R.L. Rudnick
Keywords: Break-off; Pb Isotope; Dabie-Sulu orogenic belt; North China craton; Yangtze; Jianzishan
The Jiazishan complex is the only alkaline complex closely related to the continental collision between the North China and Yangtze cratons in the Sulu ultrahigh pressure metamorphic (UHPM) belt, eastern China. Recently, Yang et al. (2005) provided a petrogenetic model for the complex in which the parent magma was generated from melting subducted lithospheric mantle of the Yangtze craton. We believe that Pb isotopic data, not considered by Yang et al. (2005), are inconsistent with this hypothesis. We instead suggest that this complex formed from melts of North China craton lithospheric mantle that formed in response to slab break-off and accompanying asthenospheric upwelling. Our parallel study on the Jiazishan complex (Gao et al., 2004) found virtually the same trace element and Sr–Nd isotopic characteristics as Yang et al. (2005), such as enrichment in LILE and LREE and depletion in HFSEs, εNd(t) = − 13.6 to − 16.2, 87Sr/86Sr(t) = 0.7029–0.7067, suggesting that the complex was derived from an enriched lithospheric mantle. However, the geochemical data, esDOI of original article: 10.1016/j.chemgeo.2005.07.006. ⁎ Corresponding author. Tel.: +86 551 3607656; fax: +86 551 3607386. E-mail address: [email protected] (Z. Xie). 0009-2541/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.chemgeo.2006.05.012
pecially Pb isotopic data, do not support the hypothesis that the complex derived from partial melting of subducted Yangtze lithospheric mantle. The distinctive Pb isotopic data suggest that the complex was derived from the overlying North China craton during the Late Triassic. In the Late Mesozoic (about 120 to 160 Ma), lithospheric mantle beneath the North China and Yangtze cratons shared similar trace element characteristics, but different Sr–Nd–Pb isotopic ratios. In the central North China craton (that is, in the Jinan, Zouping and Taihangshan regions) where the sub-continental mantle was little affected by subducted materials from the Yangtze craton, the lithospheric mantle had an EM I character (Guo et al., 2001; Zhang et al., 2004). However, further south, Late Mesozoic basalts and mafic rocks from the MidLower Yangtze region and Dabie terrane had EM II type Sr–Nd isotopic characteristics (Li et al., 1998; Jahn et al., 1999; Chen et al., 2001; Xie et al., 2003). Along the southern margin of the North China craton, the lithospheric mantle also possesses EM II like Sr–Nd characteristics, such as shown by the Fangcheng basalt (Zhang et al., 2002). This is interpreted to be due to the involvement of the subducted Yangtze lithosphere (Jahn et al., 1999; Zhang et al., 2002, 2004). However, Sr–Nd isotopes are not diagnostic of the source of the Jiazishan complex, since
192
Z. Xie et al. / Chemical Geology 235 (2006) 191–194
Fig. 1. 206Pb/204Pb vs. 207Pb/204Pb plot for feldspars from the Jiazishan complex, compared with Late Mesozoic (120–160 Ma) basaltic and mafic intrusive rocks from the Yangtze and North China cratons. (Data of North China craton are from Zhang et al., 2004; Xie et al., unpublished data. Data of Yangtze craton and Fangcheng basalt are from Chen et al., 2001; Zhang et al., 2002; Yan et al., 2003,2005; Xie et al., unpublished data. Data of Dabie mafic rocks are from Wang et al., 2005; Xie et al. unpublished data). The fields of DMM, EM I, EM II and NHRL are taken from Zindler and Hart (1986), Pb evolution lines from Zartman and Doe (1981).
the Jiazishan data plot between the Yangtze and North 87 86 China craton fields in the εNd(t) vs. Sr/ Sr(t) plot (Yang et al., 2005; Gao et al., 2004). The distinction between the Mesozoic lithospheric mantle from the North China and Yangtze cratons is most clearly seen from Pb isotopes. The subcontinental lithospheric mantle of the Yangtze craton and the southern margin of the North China craton where it was affected by the subducted Yangtze materials have high 206 Pb/ 204 Pb > 17.50, reflecting a mixing of depleted mantle and EM II end members (Fig. 1; Chen et al., 2001; Zhang et al., 2002; Yan et al., 2003, 2005; Xie et al., unpublished data). In the central North China craton, mafic rocks show low 206Pb/204Pb < 17.5 (Fig. 1; Zhang et al., 2004; Xie et al., unpublished data). The low 207Pb/204Pb ratios (about 15.2–15.3) of these rocks suggest that assimilation of the lower crust cannot be entirely eliminated. The isotopic data for the Jiazishan complex are similar to those of the North Dabie terrane (Fig.1, this work; Gao et al., 2004,Yang et al., 2005). These similarities can be explained by a continental collisionwedging mode (Li and Yang, 2003; Wang et al., 2005), in which the lower crust and the lithospheric mantle on the southern margin of the North China craton wedged into the north margin of the Yangtze craton shortly after Triassic collision. The process caused a decoupling of the surface and subsurface geology in the Dabie-Sulu region. The subcontinental lithospheric mantle beneath the North Dabie terrane has characteristics of the North China craton, although surface rocks show Yangtze craton characteristics. The low 206 Pb/ 204 Pb ratios (< 17.3) of the mafic–ultramafic intrusions that crop
out in the northern part of the Dabie orogen suggest that lithospheric mantle underneath the northern Dabie has an affinity with the North China subcontinental lithosphere (Wang et al., 2005; Xie et al., unpublished data). Pb isotopic ratios of the Jiazishan complex (Table 1; 206 Pb/204Pb = 16.33–16.46; 207Pb/204 Pb = 15.37–15.43; 206 Pb/204Pb = 36.80–37.10) are significantly different from those of the Yangtze lithospheric mantle, and are similar to those of mafic rocks from the central North China craton Table 1 Pb isotopic ratios of feldspars from the Jiazishan complex Sample no. Lithology
206
207
208
02SD401 02SD402 02SD407 01SD178
16.416 16.417 16.464 16.457
15.427 15.406 15.423 15.382
36.911 36.861 37.101 36.902
16.432
15.368
36.877
16.455
15.374
36.872
16.345 16.328
15.399 15.416
36.800 36.835
02SD405 02SD408 01SD187 01SD192
Gabbro Gabbro Gabbro Pyroxene syenite Pyroxene syenite Pyroxene syenite Quartz syenite Granite
Pb/204Pb
Pb/204Pb
Pb/204Pb
Pb isotopic measurements were performed in the CAS Key Laboratory of Crust–Mantle Materials and Environments. Pb was separated by chromatography on Bio-Rad AG-1 × 8 anion exchange resin. Pb was loaded in 1.5 mol/L HCl + 0.65 mol/L HBr solution and then eluted using 1.0 mol/L HNO3. Pb isotopic ratios were analyzed on a Finnigan MAT-262 multi-collector thermal ionization mass spectrometer by static mode. Measured isotopic ratios were corrected for a mass fractionation of 0.01% per atomic mass unit determined by replicate measurements of reference material SRM 981. The ratios listed in the table were corrected for the minor in situ radiogenic component.
Z. Xie et al. / Chemical Geology 235 (2006) 191–194
and Dabie orogen, having a clear EM I affinity (Fig. 1) noted by Zindler and Hart (1986) to be characterized by unradiogenic 206Pb/204Pb ratios. Therefore, the Pb isotopic data suggest that the Jiazishan complex is not derived from the subducted Yangtze plate, but from the overlying North China plate. Two tectonic models have been suggested to explain the formation of the Jiazishan complex: partial melting of the overlying mantle wedge after the break-off of the subducted plate (Chen et al., 2003) and partial melting of the subducted slab resulting from lithospheric removal and crustal extension (Yang et al., 2005). Among many criteria that can be used to discriminate the two models, the source of the parent magma is crucial. According to the break-off model, when the Yangtze lithosphere was subducted towards the North China craton during the Triassic, opposing buoyancy forces led to extensional deformation in the subducted slab and slab break-off. Following the break-off, upwelling hot asthenospheric mantle intruded into the narrow rift, resulting in partial melting of the overlying North China lithospheric mantle, but not the subducted slab itself, thus forming the K-rich Jiazishan complex. The obvious similarity of Pb isotopic characteristics between the Jiazishan complex and North China craton clearly supports this model. In contrast, Yang et al. (2005) suggested that the complex was derived from lithospheric mantle of the subducted Yangtze craton, which melted during post-orogenic extension. Based on this model, the complex should share similar Pb isotopic characteristics with the Yangtze lithosphere (206 Pb/ 204 Pb = 17.649–18.603, 207 Pb/204 Pb = 15.422–15.623, 208 Pb/204Pb = 37.674–38.521; Chen et al., 2001; Yan et al., 2003, 2005; Xie, unpublished data). However, this is not the case (Table 1). Therefore, we strongly argue that the Jiazishan complex is formed by slab break-off, but not by post-orogenic extension. The break-off model has also been supported by many geochronological and geochemical works for Dabie-Sulu UHPM rocks (Li et al., 2000, 2005; Liu et al., 2004). Acknowledgement We are grateful to Dr. Roberta Rudnick for the helpful reviews on the early version of the manuscript. This work is supported by the National Science Foundation of China (40203004). References Chen, J.F., Yan, J., Xie, Z., Xu, X., Xing, F.M., 2001. Nd and Sr isotopic compositions of igneous rocks from the Lower Yangtze region in eastern China: constraints on sources. Phys. Chem. Earth, Part A 26, 719–731.
193
Chen, J.F., Xie, Z., Li, H.M, Zhang, H.D., Zhou, T.X., Park, Y.S., Ahn, K.S., Chen, D.G., Zhang, X., 2003. U–Pb zircon ages for a collision-related K-rich complex at Shidao in the Sulu ultrahigh pressure terrane, China. Geochem. J. 37, 35–46. Gao, T.S., Chen, J.F., Xie, Z., Yan, J., Qian, H., 2004. Geochemistry of Triassic igneous complex at Shidao in the Sulu UHP metamorphic belt. Acta Petrol. Sin. 20, 1025–1038 (in Chinese with English abstract). Guo, F., Fan, W.M., Wang, Y.J., Lin, G., 2001. Late Mesozoic intrusive complexes in North China Block: constraints on the nature of subcontinental lithospheric mantle. Phys. Chem. Earth 26, 759–771. Jahn, B.M., Wu, F.Y., Lo, C.H., Tsai, C.H., 1999. Crust–mantle interaction induced by deep subduction of the continental crust: geochemical and Sr–Nd isotopic evidence from post-collisional mafic–ultramafic intrusions of the northern Dabie Complex, central China. Chem. Geol. 157, 119–146. Li, S.G., Yang, W., 2003. Decoupling of surface and subsurface sutures in the Dabie Orogen and a continent-collisional lithospheric-wedging model: Sr–Nd–Pb evidences of Mesozoic igneous rocks in eastern China. China Sci. Bull. 48, 831–838. Li, S.G., Nie, Y.H., Hart, S.R., Zhang, Z.Q., 1998. Interaction between subducted continental crust and the mantle. II. Sr and Nd isotopic geochemistry of syncollisional mafic–ultramafic intrusions in Dabie Mountains. Sci. China (Ser. D) 41, 632–638. Li, S.G., Jagoutz, E., Chen, Y.Z., Li, Q.L., 2000. Sm–Nd and Rb–Sr isotopic chronology and cooling history of ultrahigh pressure metamorhic rocks and their country rocks at Shuanghe in the Dabie terrain, central China. Geochim. Cosmochim. Acta 64, 1077–1093. Li, S.G., Li, Q.L., Hou, Z.H., Yang, W., Wang, Y., 2005. Cooling history and exhumation mechanism of the ultrahigh-pressuremetamorphic rocks in the Dabie mountains, central China. Acta Petrol. Sin. 21, 1117–1124 (in Chinese with English abstract). Liu, F.L., Xu, Z.Q., Liou, J.G., Song, B., 2004. SHRIMP ages of ultrahigh-pressure and retrograde metamorphism of gneisses, south-western Sulu terrane, eastern China. J. Met. Wang, Y.J., Fan, W.M., Peng, T.P., Zhang, H.F., Guo, F., 2005. Nature of the Mesozoic lithospheric mantle and tectonic decoupling beneath the Dabie orogen, central China: evidence from 40Ar/39Ar geochronology, elemental and Sr–Nd–Pb isotopic compositions of Early Cretaceous mafic igneous rocks. Chem. Geol. 220, 165–189. Xie, Z., Chen, J.F., Zhang, X., Zhou, T.X., 2003. Geochemistry of Early Cretaceous basalt in the Xiaotian Basin, North Huaiyang region: evidence of enriched mantle. Bull. Mineral. Petrol. Geochem. 22, 26–31 (in Chinese with English abstract). Yan, J., Chen, J.F., Yu, G., Qian, H., Zhou, T.X., 2003. Pb isotopic characteristics of Late Mesozoic mafic rocks from the Lower Yangtze region: evidence for enriched mantle. Geol. J. China Univ. 9, 195–206 (in Chinese with English abstract). Yan, J., Chen, J.-F., Xie, Z., Yang, G., Yu, G., Qian, H., 2005. Geochemistry of Late Mesozoic basalts from Kedoushan in the middle and lower Yangtze regions: constraints on characteristics and evolution of the lithospheric mantle. Geochimica 34, 455–469 (in Chinese with English abstract). Yang, J.H., Chung, S.L., Wilde, S., Wu, F.Y., Chu, M.F., Lo, C., Fan, H.R., 2005. Petrogenesis of post-orogenic syenites in the Sulu orogenic belt, east China: geochronological, geochemical and Nd–Sr isotopic evidence. Chem. Geol. 214, 99–125. Zartman, R.E, Doe, B.R., 1981. Plumbotectonics — the model. Tectonophysics 75, 135–162.
194
Z. Xie et al. / Chemical Geology 235 (2006) 191–194
Zhang, H.F., Sun, M., Zhou, X.H, Fan, W.M., Zhai, M.G., Yin, J.F., 2002. Mesozoic lithosphere destruction beneath the North China Craton: evidence from major-, trace-element and Sr–Nd–Pb isotope studies of Fangcheng basalts. Contrib. Mineral. Petrol. 144, 241–253. Zhang, H.F., Sun, M., Zhou, M.F., Fan, W.M., Zhou, X.H., Zhai, M.G., 2004. Highly heterogeneous Late Mesozoic lithospheric mantle
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