U-Pb zircon ages, geochemical and Sr-Nd-Hf isotopic compositions of granitoids in western Songpan-Garze fold belt: Petrogenesis and implication for tectonic evolution

Abstract

Granitoids are widespread in the Songpan-Garze (松潘-甘孜) fold belt, western China. These granitoids provide insight into regional tectono-magmatic events, basement nature and tectonic evolution. However, previous studies mainly focused on the eastern Songpan-Garze fold belt. In this article, five granitoid intrusions from the western Songpan-Garze fold belt have been studied. These intrusions are composed of quartz-diorite and granodiorite. Using LA-ICP-MS zircon dating method, the obtained magma crystallization ages are 219±2 Ma for the quartz-diorite and 216±5 Ma for the granodiorite. The ages, combined with regional geological analyses, show that they formed in a post-collisional tectonic setting. The quartz-diorite and granodiorite display co-linear variation in their chemical compositions. REE compositions for both the quartz-diorite and granodiorite show strongly fractionated patterns with (La/Yb)_N=5.02–18.34 and Eu/Eu*=0.44–0.89. The quartz-diorites have initial ⁸⁷Sr/⁸⁶Sr ratios (I _Sr) of 0.709 29–0.711 97 and ɛ _Nd(t) values of −8.6 to −6.1 and the granodiorites have I _Sr values of 0.705 49–0.709 97 and ɛ _Nd(t) values of −8.3 to −4.3. Zircon Hf isotopic data show ɛ _Hf(t) values of −3.8 to +1.6 for the quartz-diorites and −1.2 to +3.0 for the granodiorites. Geochemical and Sr-Nd-Hf isotopic compositions indicate that the quartz-diorites and granodiorites have similar petrogenesis. We suggest that the magmas for the quartz-diorites and granodiorites were derived from partial melting of lower crustal mafic source, resulting from amphibole dehydration melting reaction. The probing of the magma source reveals that the western Songpan-Garze fold belt contains an unexposed continental basement, which is similar to the eastern Songpan-Garze fold belt. Geodynamically, it is proposed that a lithospheric delamination model can account for the magma generation for the quartz-diorites and granodiorites in the western Songpan-Garze fold belt.

Keywords

granitoid / petrogenesis / nature of basement / geodynamics / western Songpan-Garze fold belt

References

[1] Andersen T.. Correction of Common Lead in U-Pb Analyses That do not Report ²⁰⁴Pb. Chemical Geology, 2002, 192: 59-79.

[2] Beard J. S., Lofgren G. E.. Dehydration Melting and Water-Saturated Melting of Basaltic and Andesitic Greenstones and Amphibolites at 1, 3 and 6.9 kb. J. Petrol., 1991, 32: 365-401.

[3] Blichert-Toft J., Albarede F.. The Lu-Hf Isotope Geochemistry of Chondrites and the Evolution of the Mantle-Crust System. Earth and Planet. Sci. Lett., 1997, 148: 243-258.

[4] Bruguier O., Lancelot J. R., Malavieille J.. U-Pb Dating on Single Detrital Zircon Grains from the Triassic Songpan-Garze Flysch (Central China): Provenance and Tectonic Correlations. Earth and Planet. Sci. Lett., 1997, 152: 217-231.

[5] Calassou S.. Étude Tectonique d’une Chaine de Décollement: A) Tectonique Triasique et Tertiaire de la Chaine de Songpan-Garzê. B) Géométrie et Cinématique des Déformations Dans les Prismes D’accrétion Sédimentaire: Modélisation Analogique: [Dissertation], 1994, Montpellier: Univ. Montpellier II 1-400.

[6] Chen S. F., Wilson C. J. L.. Emplacement of the Long-men Shan Thrust-Nappe Belt along the Eastern Margin of the Tibetan Plateau. J. Struct. Geol., 1996, 18: 413-430.

[7] Chung S. L., Chu M. F., Zhang Y., . Tibetan Tectonic Evolution Inferred from Spatial and Temporal Variations in Post-Collisional Magmatism. Earth-Sci. Rev., 2005, 68: 173-196.

[8] Chung S. L., Liu D., Ji J., . Adakites from Continental Collision Zones: Melting of Thickened Lower Crust beneath Southern Tibet. Geology, 2003, 31: 1021-1024.

[9] DePaolo D. J.. Neodymium Isotopes in the Colorado Front Range and Crust-Mantle Evolution in the Proterozoic. Nature, 1981, 291: 193-196.

[10] DePaolo D. J.. A Neodymium and Strontium Isotopic Study of the Mesozoic Calc-Alkaline Granitic Batholiths of the Sierra Nevada and Peninsular Ranges, California. J. Geophys. Res., 1981, 86: 10470-10488.

[11] Elena A. K., Maurice B., Jacques M.. Discovery of the Paleo-Tethys Residual Peridotites along the Anyemaqen-Kunlun Suture Zone (North Tibet). C. R. Geoscience, 2003, 335: 709-719.

[12] Enkin R. J., Yang Z. Y., Chen Y., . Paleomagnetic Constraints on the Geodynamic History of the Major Blocks of China from the Permian to the Present. J. Geophys. Res., 1992, 97: 13953-13989.

[13] Harrowfield M. J., Wilson C. J. L.. Indosinian Deformation of the Songpan Garzê Fold Belt, Northeast Tibetan Plateau. J. Struct. Geol., 2005, 27: 101-117.

[14] Helz R. T.. Phase Relations of Basalts in Their Melting Ranges at P _H2O=5 kb, Part II: Melt Compositions. J. Petrol., 1976, 17(2): 139-193.

[15] Hou Z. Q., Gao Y. F., Qu X. M., . Origin of Adakitic Intrusives Generated during Mid-Miocene East-West Extension in Southern Tibet. Earth and Planet. Sci. Lett., 2004, 220(1–2): 139-155.

[16] Hu J. M., Meng Q. R., Shi Y. R., . SHRIMP U-Pb Dating of Zircons from Granitoid Bodies in the Songpan-Ganzi Terrane and Its Implications. Acta Petrol. Sin., 2005, 21(3): 867-880.

[17] Huang J. Q., Chen B. W.. The Evolution of the Tethys in China and Adjacent Regions, 1987, Beijing: Chinese Academy of Geological Sciences 109

[18] Ilbeyli N., Pearce J. A., Thirlwall M. F., . Petrogenesis of Collision-Related Plutonics in Central Anatolia, Turkey. Lithos, 2004, 72: 163-182.

[19] Johannes W., Holtz F.. Petrogenesis and Experiment Petrology of Granitic Rocks, 1996, Berlin: Springer 1-254.

[20] Jung S., Mezger K., Hoernes S.. Petrology and Geochemistry of Syn-to Post-Collisional Metaluminous A-Type Granites: A Major and Trace Element and Nd-Sr-Pb-O-Isotope Study from the Proterozoic Damara Belt, Namibia. Lithos, 1998, 45: 147-175.

[21] Liu M. J., Mooney W. D., Li S. L., . Crustal Structure of the Northeastern Margin of the Tibetan Plateau from the Songpan-Ganzi Terrane to the Ordos Basin. Tectonophysics, 2006, 420: 253-266.

[22] Liu Y. S., Hu S. H., Liu X. M., . Accurate Analysis of Zr, Hf, Nb and Ta in High-Grade Metamorphic Rocks with ICP-MS. Earth Science—Journal of China University of Geosciences, 2003, 28: 151-156.

[23] Ludwig K. R.. Isoplot/Ex Version 2.49: A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center Special Publ., 2001, 1a: 53

[24] Mattauer M., Malavieille J., Calassou S., . La Chaîne Triasique de Songpan-Garze (ouest Sechuaneastern Tibet): une Chaîne de Plissement-décollement sur Marge Passive. Comptes Rendus de 1’Académie des Sciences Paris, 1992, 314: 619-626.

[25] McCulloch M. T., Chappell B. W.. Nd Isotopic Characteristics of S- and I-Type Granites. Earth Planet. Sci. Lett., 1982, 58: 51-64.

[26] Mo X. X., Lu F. X., Shen S. Y., . Sanjiang Tethyan Volcanism and Related Mineralization, 1993, Beijing: Geological Publishing House 1-267.

[27] Nie S. Y., Yin A., Rowley D. B., . Exhumation of the Dabie Shan Ultra-High-Pressure Rocks and Accumulation of the Songpan-Ganzi Flysch Sequence, Central China. Geology, 1994, 22: 999-1002.

[28] Pan G. T., Ding J., Yao D. S., . Geological Map of Qinghai-Xizang (Tibet) Plateau and Adjacent Areas (1: 1 500 000), 2004, Chengdu: Chengdu Cartographic Publishing House

[29] Patino-Douce A. E., Harris N.. Experimental Constraints on Himalayan Anatexis. J. Petrol., 1998, 39: 689-710.

[30] Patino-Douce A. E., McCarthy T. C.. Hacker B. R., Liou J. G.. Melting of Crustal Rocks during Continental Collision and Subduction. When Continents Collide: Geodynamics and Geochemistry of Ultrahigh-Pressure Rocks, 1998, Dordrecht: Kluwer Academic Publishers 27-55.

[31] Petford N., Atherton M.. Na-Rich Partial Melts from Newly Underplated Basaltic Crust: The Cordillera Blanca Batholith, Peru. J. Petrol., 1996, 37: 1491-1521.

[32] Rapp R. P., Watson E. B.. Dehydration Melting of Metabasalt at 8–32 kbar: Implications for Continental Growth and Crust-Mantle Recycling. J. Petrol., 1995, 36: 891-931.

[33] Reid A. J., Wilson C. J. L., Liu S.. Structural Evidence for the Permo-Triassic Tectonic Evolution of the Yidun Arc, Eastern Tibetan Plateau. J. Struct. Geol., 2005, 27: 119-137.

[34] Reid A. J., Wilson C. J. L., Liu S., . Mesozoic Plutons of the Yidun Arc, SW China: U/Pb Geochronology and Hf Isotopic Signature. Ore Geol. Rev., 2007, 31: 88-106.

[35] Roger F., Calassou S.. Géochronologie U-Pb sur Zircons et Géochimie (Pb, Sr et Nd) du socle de la Chaîne de Songpan-Garze (Chine). Comptes Rendus de l’Académie des Sciences Paris, 1997, 324: 819-826.

[36] Roger F., Arnaud N., Gilder S., . Geochronological and Geochemical Constraints on Mesozoic Suturing in East Central Tibet. Tectonics, 2003, 22: 111-119.

[37] Roger F., Malavieille J., Leloup P. H., . Timing of Granite Emplacement and Cooling in the Songpan-Garze Fold Belt (Eastern Margin of the Tibetan Plateau) with Tectonic Implications. J. Asian Earth Sci., 2004, 22: 465-481.

[38] Rushmer T.. Partial Melting of Two Amphibolites: Contrasting Experimental Results under Fluid Absent Condi tions. Contrib. Mineral. Petrol., 1991, 107: 41-59.

[39] Scherer E., Muenker C., Mezger K.. Calibration of the Lutetium-Hafnium Clock. Science, 2001, 293: 683-687.

[40] Sengör A. M. C.. Tectonic Subdivisions and Evolution of Asia. Bull. Tech. Univ. Istanbul, 1985, 46: 355-435.

[41] Sisson T. W., Ratajeski K., Hankins W. B.. Voluminous Granitic Magmas from Common Basaltic Sources. Contrib. Mineral. Petrol., 2005, 148: 635-661.

[42] Sun S. S., McDonough W. F., Sunders A. D., Norry M. J.. Magmatism in the Ocean Basins. J. Geol. Soc. Special Publ., 1989, 42: 313-345.

[43] Sun Y., Chen L., Feng T., . A Dynamic Model of Paleo-Tethyan Evolution: Evidences from Paleo-Tethyan Ophiolite in China. J. Northwest University, 2002, 32: 1-6.

[44] Taylor S. R., McLennan S. M.. The Continental Crust: Its Composition and Evolution, 1985, Oxford.: Blackwell 312

[45] Tepper J. H., Nelson B. K., Bergantz G. W.. Petrology of the Chilliwack Batholith, North Cascades, Washington: Generation of Calc-Alkaline Granitoids by Melting of Mafic Lower Crust with Variable Water Fugacity. Contrib. Mineral. Petrol., 1993, 113: 333-351.

[46] Turner S., Hawkesworth C., Liu J. Q., . Timing of Tibetan Uplift Constrained by Analysis of Volcanic Rocks. Nature, 1993, 364: 50-54.

[47] Vervoort J., Blichert-Toft J.. Evolution of the Depleted Mantle: Hf Isotope Evidence from Juvenile Rocks through Time. Geochim. Cosmochim. Acta, 1999, 63: 533-556.

[48] Wang X. F., Metcalfe I., Jian P., . The Jinshajiang-Ailaoshan Suture Zone, China: Tectonostratigraphy, Age and Evolution. J. Asian Earth Sci., 2000, 18: 675-690.

[49] Wolf M. B., Wyllie P. J.. The Formation of Tonalitic Liquids during the Vapor-Absent Partial Melting of Amphibolite at 10 kbar. EOS, 1992, 70: 506-518.

[50] Wu F. Y., Lin J. Q., Wilde S.A., . Nature and Significance of the Early Cretaceous Giant Igneous Event in Eastern China. Earth Planet. Sci. Lett., 2005, 233: 103-119.

[51] Wu F. Y., Sun D. Y., Li H. M., . A-Type Granites in Northeastern China: Age and Geochemical Constraints on Their Petrogenesis. Chem. Geol., 2002, 187: 143-173.

[52] Wu F. Y., Yang Y. H., Xie L. W., . Hf Isotopic Compositions of the Standard Zircons and Baddeleyites Used in U-Pb Geochronology. Chem. Geol., 2006, 234: 105-126.

[53] Xiao L., Zhang H. F., Clemens J. D., . Late Triassic Granitoids of the Eastern Margin of the Tibetan Plateau: Geochronology, Petrogenesis and Implications for Tectonic Evolution. Lithos, 2007, 96: 436-452.

[54] Xu J. F., Castillo P. R., Li X. H., . MORB-Type Rocks from the Paleo-Tethyan Mian-lueyang Northern Ophiolite in the Qinling Mountains, Central China: Implications for the Source of the Low ²⁰⁶Pb/²⁰⁴Pb and High ¹⁴³Nd/¹⁴⁴Nd Mantle Component in the Indian Ocean. Earth Planet. Sci. Lett., 2002, 198: 323-337.

[55] Xu Z. Q., Hou L. W., Wang Z. X., . Orogenic Processes of the Songpan-Garze Orogenic Belt of China, 1992, Beijing: Geological Publishing House 8-12.

[56] Yin A., Nie S. Y.. An Indentation Model for North and South China Collision and the Development of the Tanlu and Honam Fault Systems, Eastern Asian. Tectonics, 1993, 12: 801-813.

[57] Yuan H. L., Gao S., Liu X. M., . Accurate U-Pb Age and Trace Element Determinations of Zircon by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. Geostandards and Geoanalytical Research, 2004, 28: 353-370.

[58] Zhang C. Z., Li B., Cai J. X., . First Finding of A-Type Granite and Adakitic Magmatism Association in Songpan-Garze Fold Belt, Eastern Tibetan Plateau: Implication for Lithospheric Delamination: Comment. Lithos, 2008, 103: 562-564.

[59] Zhang H. F., Harris N., Parrish R., . Causes and Consequences of Protracted Melting of the Mid-Crust Exposed in the North Himalayan Antiform. Earth Planet. Sci. Lett., 2004, 228: 195-212.

[60] Zhang H. F., Zhang L., Harris N., . U-Pb Zircon Ages, Geochemical and Isotopic Compositions of Granitoids in Songpan-Garze Fold Belt, Eastern Tibetan Plateau: Constraints on Petrogenesis, Nature of Basement and Tectonic Evolution. Contrib. Mineral. Petrol., 2006, 152: 75-88.

[61] Zhang H. F., Parrish R., Zhang L., . A-Type Granite and Adakitic Magmatism Association in Songpan-Garze Fold Belt, Eastern Tibetan Plateau: Implication for Lithospheric Delamination. Lithos, 2007, 97: 323-335.

[62] Zhang H. F., Parrish R., Zhang L., . Reply to the Comment by Zhang et al. on: “First Finding of A-Type and Adakitic Magmatism Association in Songpan-Garze Fold Belt, Eastern Tibetan Plateau: Implication for Lithoshperic Delamination”. Lithos, 2008, 103: 565-568.

[63] Zheng Y. F., Zhang S. B., Zhao Z. F., . Contrasting Zircon Hf and O Isotopes in the Two Episodes of Neoproterozoic Granitoids in South China: Implications for Growth and Reworking of Continental Crust. Lithos, 2007, 96: 127-150.

[64] Zhou D., Graham S. A.. Songpan Ganzi Flysch Triassic Complex as a Remnant Ocean Basin along Diachronous Qinling Collision Orogen, Central China. Geol. Soc. Am. Abst. Prog., 1993, 25(6): 118