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Emplacement age for the mafic-ultramafic plutons in the northern Dabie Mts. (Hubei): Zircon U-Pb, Sm-Nd and40Ar/39Ar dating

  • Jianghai Wang
  • Shangxian Deng
Article

Abstract

The protoliths of mafic-ultramafic plutons in the northern Dabie Mts. (NDM) (Hubei) include pyroxenite and gabbro. The zircon U-Pb dating for a gabbro suggests that emplacement of mafic magma took place in the post-collisional setting at the age of 122.9±0.6 Ma. It is difficult to obtain a reliable Sm-Nd isochron age, due to disequilibrium of the Sm-Nd isotopic system. Two hornblende40Ar/39Ar ages of 116.1±1.1 Ma and 106.6±0.8 Ma may record cooling of metamorphism in the mafic-ultramafic plutons in Hubei below 500°C. The hornblende40Ar/39Ar ages for the mafic-ultramafic rocks in Hubei are evidently 15–25 Ma younger than those for the same rocks in Anhui, indicating that there is a diversity of the cooling rates for the mafic-ultramafic rocks in Hubei and Anhui. The difference in their cooling rates may be controlled by the north-dipping normal faults in the NDM. The intense metamorphism occurring in the mafic-ultramafic rocks in Hubei may result from the Yanshanian magmatic reheating and thermal fluid action induced by the Cretaceous migmatization. The geochemical similarity of these mafic-ultramafic rocks wherever in Hubei and Anhui may be attributed to the same tectonic setting via an identical genetic mechanism.

Keywords

mafic-ultramafic plutons geochronology Dabie Mountains 

References

  1. 1.
    Zhang, Q., Ma, B. L., Liu, R. X. et al., A remnant of continental lithospheric mantle above a subduction zone: Geochemical constraints on ultramafic rocks from Raobazhai area in Anhui Province, Sci. in China, Ser. 1995, 38(12): 1522–1529.Google Scholar
  2. 2.
    Zhai, M. G., Cong, B. L., Petro-tectonics of the Sulu-Dabie Shan metamorphic belt, Central and East China, Sci. in China, Ser. D, 1996,39(3): 319–328.Google Scholar
  3. 3.
    Li, S. G., Hart, S. R., Zheng, S. G. et al., Timing of collision between the North and South China Blocks—the Sm-Nd isotopic age evidence, Sci. in China, Ser. B, 1989, 32(11): 1393–1400.Google Scholar
  4. 4.
    Ni, Y. H., Li, S. G., Sm-Nd ages of the syn-collisional mafic-ultramafic intrusions in the Dabie Mountains, Chinese Sci. Bull., 1998, 43(2): 160–163.CrossRefGoogle Scholar
  5. 5.
    Chen, D. G., Wu, Y. B., Xia, Q. K. et al., Sm-Nd ages for the Jiaoziyan gabbro pluton and the characteristics of Nd isotopes, Acta Geosci. Sinica, 1997, 18(Suppl.): 9–11.Google Scholar
  6. 6.
    Jahn, B. M., Wu, F. Y., Lo, C. H. et al., 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., 1999, 157: 119–146.Google Scholar
  7. 7.
    Li, S. G., Jagoutz, E., Zhang, Z. Q. et al., Structure of high-metamorphic belt in the Dabie mountains and its tectonic implications, Chinese Sci. Bull., 1995, 40(Suppl.): 138–140.Google Scholar
  8. 8.
    Zhang, R. Y., Liou, J. G., Tsai, C. H., Petrogenesis of a high-temperature metamorphic terrain: a new interpretation for the north Dabie Shan, central China, J. Metamorphic Geol., 1996, 14: 319–333.CrossRefGoogle Scholar
  9. 9.
    Wang, J. H., The Early Evolution of the Dabie Complex, with Special Reference to the Genetic Mechanism of Migmatites, Wuhan: China University of Geosciences Press, 1991, 1–140.Google Scholar
  10. 10.
    Suo, S. T., Zhong, Z. Q., You, Z. D., Extensional deformation of post ultrahigh-pressure metamorphism and exhumation process of ultrahigh-pressure metamorphic rocks in the Dabie massif, China, Sci. in China, Ser. D, 2000, 43(2): 225–236.CrossRefGoogle Scholar
  11. 11.
    Hacker, B. R., Wang, Q. C., Ar/Ar geochronology of ultrahigh-pressure metamorphism in Central China, Tectonics, 1995, 14: 994–1006.CrossRefGoogle Scholar
  12. 12.
    Ge, N. J., Hou, Z. H., Li, H. M. et al., Zircon U-Pb ages of the Shacun gabbro body, Yuexi, Dabie orogen and its geological implications, Chinese Sci. Bull., 2000, 45(1): 74–79.CrossRefGoogle Scholar
  13. 13.
    Xu, S. T., Liu, Y. C., Jiang, L. L. et al., Tectonic Regime and Evolution of the Dabie Mountains, Beijing: Science Press, 1994, 1–175.Google Scholar
  14. 14.
    Li, S. G., Ni, Y. H., Zheng, S. G. et al., Interaction between subducted continental crust and the mantle: I. Major and trace element geochemistry of syncollisional mafic-ultramafic intrusions in the Dabie Mountains, Sci. in China, Ser. D, 1998, 41(5): 545–553.CrossRefGoogle Scholar
  15. 15.
    Blundy, J. D., Holland, T. J. B., Calcic amphibole equilibrium and a new amphibole plagioclase geothermometer, Contrib. Mineral. Petrol. 1990, 104:208–224.CrossRefGoogle Scholar
  16. 16.
    Hammartron, J. M., Zen, E. A., Aluminum in hornbole: an empirical igneous geobarometer, Amer. Mineral., 1986, 71: 1297–1313.Google Scholar
  17. 17.
    Hollister, L. S., Grisson, G. C., Peters, E. K. et al., Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of calcalkaline plutons, Amer. Mineral., 1987,72: 231–239.Google Scholar
  18. 18.
    Johnson, M. C., Rutherford, M. J., Experimental calibration of an aluminium-hornblende geobarometer applicable to calc-alkaline rocks, EOS, 1988,69: 1511.Google Scholar
  19. 19.
    Whitney, J. A., Stormer, J. C., The distribution of NaAlSi3O8 between coexisting microcline and plagioclase and its effect on geothermometric calculations, Am. Mineral., 1977, 62: 687–691.Google Scholar
  20. 20.
    Zhang, R. Y., Cong, B. L., Mineral Thermometers and Barometers, Beijing: Geological Publishing House, 1983, 150–173.Google Scholar
  21. 21.
    Krogh, T. E., A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations, Geochim. Cosmochim. Acta, 1973,48: 505–511.Google Scholar
  22. 22.
    Krogh, T. E., Vapour transfer for the dissolution of zircons in a multi-sample capsule at high-pressure, in Short Papers of the Fourth International Conference on Geochronology, Cosmochronology, and Isotope Geology (ed. Zartman, R. E.), USGS Open-File Rep., 1978,78-701: 233-234.Google Scholar
  23. 23.
    Mao, C. X., Zhu, N. J., Zhu, B. Q. et al., Measurement techniques and application of the Sm-Nd isotopic system, Geochimica, 1989, (1): 36–42.Google Scholar
  24. 24.
    Ludwig, R. K., Isoplot—a plotting and regression program for radiogenic-isotope data, version 2.57, USGS Open-File Rep, 1992, 91–445: 40.Google Scholar
  25. 25.
    Steiger, R. H., Jäger, E., Subcommission on geochronology: Conventions on the use of decay constants in geo- and cosmo-chronology, Earth Planet. Sci. Lett., 1977, 36: 359–362.CrossRefGoogle Scholar
  26. 26.
    Dai, T. M., Hong, A. S., 40Ar/39Ar dating and some isotopic determinations on Himalayan biotite from granitoids in southern Tibet, Geochimica, 1982, (1): 48–55.Google Scholar
  27. 27.
    McDougall, I., Harrison, T. M., Geochronology and Thermochronology by the40Ar/39Ar Method, New York: Oxford University Press, 1999, 1–269.Google Scholar
  28. 28.
    Chen, T. Y., Niu, B. G., Liu, Z. G. et al., Isotopic geochronology of metamorphism and Yanshanian magmatism within the Dabie Shan, Acta Geol. Sinica, 1991, 65(4): 329–335.Google Scholar
  29. 29.
    Chen, J. F., Xie, Z., Liu, S. S., Cooling age of Dabie orogen, China determined by40Ar-39Ar and fission track techniques, Sci. in China, Ser. 1995, 38(6): 749–757.Google Scholar
  30. 30.
    Li, S., Wang, T., Geochemistry of Granitoids in the Tongbai-Dabie Mountains, Wuhan: China University of Geosciences Press, 1991,1–208.Google Scholar
  31. 31.
    Hacker, B. R., Ratschbacher, L., Webb, L. et al., U/Pb zircon ages constrain the architecture of the ultrahigh-pressure Qinling-Dabie orogen, China, Earth Planet. Sci. Lett., 1998, 161:215–230.CrossRefGoogle Scholar
  32. 32.
    Deng, S. X., Wang, J. H., Sun, M. et al., Types of leucosomes in the migmatites and their U-Pb ages at Fenghuangguan, Hubei, Geochimica, 1997, 26(2): 75–86.Google Scholar
  33. 33.
    Ratschbacher, L., Hacker, B. R., Webb, L. E. et al., Exhumation of the ultrahigh-pressure continental crust in east central China: Cretaceous and Cenozoic unroofing and the Tan-Lu fault, J. Geophys. Res., 2000,105(B6): 13030–13338.CrossRefGoogle Scholar
  34. 34.
    Faure, M., Lin, W., Shu, L. S. et al., Tectonics of the Dabieshan (eastern China) and possible exhumation mechanism of ultrahigh-pressure rocks, Terra Nova, 1999, 11(6): 251–258.CrossRefGoogle Scholar
  35. 35.
    Suo, S. T., Sang, L. K., Han, Y. J. et al., The Petrology and Tectonics in the Dabie Precambrain Metamorphic Terrain, Central China, Wuhan: China University of Geosciences Press, 1993, 151–181.Google Scholar
  36. 36.
    Wang, J. H., Wu, J. P., Yang, W. H., Dynamic mechanism for migmatization in Dabie Complex, northern Hubei Province, China, Acta Geol. Sinica, 1994, 68(4): 308–323.Google Scholar
  37. 37.
    Wang, J. H., Sun, M., Chang, X. Y. et al., Dynamic models for origin of the migmatites with thermal centers in the Dabie complex, Hubei, central China, in Procs. 30th IGC, 17: Precambrain Geology and Metamorphic Petrology (eds. Qian, X. L., You, Z. D., Jahn, B. M. et al.), Zeist: VSP, 1997, 203–215,Google Scholar
  38. 38.
    Li, S. G., Ni, Y. H., Hart, S. R. et al., Interaction between subducted continental crust and the mantle: II Sr and Nd isotopic geochemistry of syncollisional mafic-ultramafic intrusions in the Dabie Mountains, Sci. in China, Ser. D, 1998, 41(6): 632–638.CrossRefGoogle Scholar
  39. 39.
    Yin, A., Nie, S., A Phanerozoic palinspastic reconstruction of China and its neighboring regions, in The Tectonic Evolution of Asia (eds. Yin, A., Harrision, T. M.), New York: Cambridge University Press, 1996, 442–485.Google Scholar

Copyright information

© Science in China Press 2002

Authors and Affiliations

  1. 1.Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhouChina

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