The Wulian metamorphic core complex: A newly discovered metamorphic core complex along the Sulu orogenic belt, eastern China

Abstract

Combined with field studies, microscopic observations, and EBSD fabric analysis, we defined a possible Early Cretaceous metamorphic core complex (MCC) in the Wulian (五莲) area along the Sulu (苏鲁) orogenic belt in eastern China. The MCC is of typical Cordilleran type with five elements: (1) a master detachment fault and sheared rocks beneath it, a lower plate of crystalline rocks with (2) middle crust metamorphic rocks, (3) syn-kinematic plutons, (4) an upper plate of weakly deformed Proterozoic metamorphic rocks, and (5) Cretaceous volcanic-sedimentary rocks in the supradetachment basin. Some postkinematic incursions cut across the master detachment fault zone and two plates. In the upper plate, Zhucheng (诸城) Basin basement consists of the Proterozoic Fenzishan (粉子山) Group, Jinning period granite (762–834 Ma). The supradetachment basin above the Proterozoic rocks is filled with the Early Cretaceous Laiyang (莱阳) (∼135–125 Ma) and Qingshan (青山) groups (120–105 Ma), as well as the Late Cretaceous Wangshi (王氏) Group (85–65 Ma). The detachment fault zone is developed at the base and margin of the superposed basin. Pseudotachylite and micro breccia layers located at the top of the detachment fault. Stretching lineation and foliation are well developed in the ductile shear belt in the detachment faults. The stretching lineation indicates a transport direction of nearly east to west on the whole, while the foliations trend WNW, WSW, and SE. Protomylonite, mylonite, and ultramylonite are universally developed in the faults, transitioning to mylonitic gneiss, and finally to gneiss downward. Microstructure and quartz preferred orientation show that the mylonites formed at high greenschist facies to low greenschist facies as a whole. The footwall metamorphic rock series of the Wulian MCC are chiefly UHP (ultrahigh pressure) metamorphic rocks. Syntectonic rocks developed simultaneously with the Wulian MCC detachment and extension. Geological research has demonstrated that the MCC is associated with small-scale intrusive rocks developing in the vicinity of the detachment faults, for instance, dike. Geochronology results indicate that the denudation of the Wulian MCC occurred at about 135–122 Ma. Its development and exhumation was irrelevant to the Sulu UHP metamorphism zone rapid exhumation during Triassic Period but resulted from the crustal extension of North China Craton and adjacent area.

Keywords

metamorphic core complex / Late Mesozoic / North China Craton / crustal extension / Sulu orogenic belt

References

[1] Charles N, Gumiaux C, Augier R, . Metamorphic Core Complexes vs. Synkinematic Plutons in Continental Extension Setting: Insights from Key Structures (Shandong Province, Eastern China). Journal of Asian Earth Sciences, 2011, 40(1): 261-278.

[2] Darby B J, Davis G A, Zhang X H, . The Newly Discovered Waziyu Metamorphic Core Complex, Yiwulushan, Western Liaoning Province, North China. Earth Science Frontiers, 2004, 11(3): 145-155.

[3] Deng J F, Mo X X, Zhao H L, . A New Model for the Dynamic Evolution of Chinese Lithosphere: ‘Continental Roots-Plume Tectonics’. Earth-Science Reviews, 2004, 65(3–4): 223-275.

[4] Enami M, Suzuki K, Zhai M G, . The Chemical Th-U-Total Pb Isochron Ages of Jiaodong and Jiaonan Metamorphic Rocks in the Shandong Peninsula, Eastern China. The Island Arc, 1993, 2(2): 104-113.

[5] Fairbairn H W, Robson G M. Breccia at Sudbury, Ontario. The Journal of Geology, 1942, 50(1): 1-33.

[6] Faure M, Lin W, Breton N L. Where Is the North China-South China Block Boundary in Eastern China?. Geology, 2001, 29(2): 119-122.

[7] Festa V. C-Axis Fabrics of Quartz-Ribbons during High-Temperature Deformation of Syn-Tectonic Granitoids (Sila Massif, Calabria, Italy). Comptes Rendus Geoscience, 2009, 341(7): 557-567.

[8] GSFSP Regional Geology Survey Report about Rizhao City, 2002 Beijing: Geologic Survey Bureau of China, 1-666.

[9] Gao S, Rudnick R L, Xu W L, . Recycling Deep Cratonic Lithosphere and Generation of Intraplate Magmatism in the North China Craton. Earth and Planetary Science Letters, 2008, 270(1–2): 41-53.

[10] Gao S, Zhang J F, Xu W L, . Delamination and Destruction of the North China Craton. Chinese Science Bulletin, 2009, 54(19): 3367-3378.

[11] Hacker B R, Ratschbacher L, Webb L, . U/Pb Zircon Ages Constrain the Architecture of the Ultrahigh-Pressure Orogen, Qinling Dabie. Earth and Planetary Science Letters, 1998, 161: 215-230.

[12] Hacker B R, Wallis S R, Ratschbacher L, . High-Temperature Geochronology Constraints on the Tectonic History and Architecture of the Ultrahigh-Pressure Dabie-Sulu Orogen. Tectonics, 2006, 25(5): 1-17.

[13] Hu J M, Zhao Y, Liu X W, . Early Mesozoic Deformations of the Eastern Yanshan Thrust Belt, Northern China. International Journal of Earth Sciences, 2010, 99(4): 785-800.

[14] Huang J, Zheng Y F, Zhao Z F, . Melting of Subducted Continent: Element and Isotopic Evidence for a Genetic Relationship between Neoproterozoic and Mesozoic Granitoids in the Sulu Orogen. Chemical Geology, 2006, 229(4): 227-256.

[15] Kusky T M, Windley B F, Zhai M G, . Zhai M G, Windley B F, Kusky T M, . Tectonic Evolution of the North China Block: From Orogen to Craton to Orogen. Mesozoic Sub-Continental Lithospheric Thinning Under Eastern Asia, 2007, 1-34.

[16] Li S G, Huang F, Li H. Post-Collisional Lithosphere Delamination of the Dabie-Sulu Orogen. Chinese Science Bulletin, 2002, 47(3): 259-263.

[17] Li S Z, Liu J Z, Zhao G C, . Key Geochronology of Mesozoic Deformation in the Eastern Block of the North China Craton and Its Constrains on Regional Tectonics: A Case of Jiaodong and Liaodong Peninsula. Acta Petrologica Sinica, 2004, 20(3): 633-646.

[18] Lin W, Wang Q C, Shi Y H. Architecture, Kinematics and Deformation Analysis in Dabie-Sulu Collision Zone. Acta Petrologica Sinica, 2005, 21(4): 1195-1212.

[19] Ling W L, Duan R C, Xie X J, . Contrasting Geochemistry of the Cretaceous Volcanic Suites in Shandong Province and Its Implications for the Mesozoic Lower Crust Delamination in the Eastern North China Craton. Lithos, 2009, 113(3–4): 640-658.

[20] Lister G S, Davis G A. The Origin of Metamorphic Core Complexes and Detachment Faults Formed during Tertiary Continental Extension in the Northern Colorado River Region, USA. Journal of Structural Geology, 1989, 11(1–2): 65-94.

[21] Liu J L, Davis G, Lin Z, . The Liaonan Metamorphic Core Complex, Southeastern Liaoning Province, North China: A Likely Contributor to Cretaceous Rotation of Eastern Liaoning, Korea and Contiguous Areas. Tectonophysics, 2005, 407(1–2): 65-80.

[22] Liu J L, Guan H M, Ji M, . The Liaonan Metamorphic Core Complex: Constitution, Structure and Evolution. Acta Geologica Sinica, 2006, 80(4): 502-513.

[23] Mao J W, Li X F, White N C, . Types, Characteristics, and Geodynamic Settings of Mesozoic Epithermal Gold Deposits in Eastern China. Resource Geology, 2007, 57(4): 435-454.

[24] Menzies M A, Fan W, Zhang M. Palaeozoic and Cenozoic Lithoprobes and the Loss of >120 km of Archaean Lithosphere, Sino-Korean Craton, China. Geological Society, London, Special Publications, 1993, 76(1): 71-81.

[25] Okudaira T, Takeshita T, Hara I, . A New Estimate of the Conditions for Transition from Basal <a> to Prism [c] Slip in Naturally Deformed Quartz. Tectonophysics, 1995, 250(1–3): 31-46.

[26] Passchier C W, Zhang J S, Konopa J, . Geometric Aspects of Synkinematic Granite Intrusion into a Ductile Shear Zone-An Example from the Yunmengshan Core Complex. Geological Society, London, Special Publications, 2005, 245(1): 65-80.

[27] Ratschbacher L, Hacker B R, Webb L E, . Ex humation of the Ultrahigh-Pressure Continental Crust in East Central China: Cretaceous and Cenozoic Unroofing and the Tan-Lu Fault. Journal of Geophysical Research, 2000, 105(B6): 13303-13338.

[28] Ren J Y, Tamaki K, Li S T, . Late Mesozoic and Cenozoic Rifting and Its Dynamic Setting in Eastern China and Adjacent Areas. Tectonophysics, 2002, 344(3–4): 175-205.

[29] Schmid S M, Casey M. Complete Fabric Analysis of Some Commonly Observed Quartz c-Axis Patterns. Mineral and Rock Deformation: Laboratory Studies-The Paterson Volume, 1986, 36: 263-286.

[30] Schofield D I, D’Lemos R S. Relationships between Syn-Tectonic Granite Fabrics and Regional PTtd Paths: An Example from the Gander-Avalon Boundary of NE Newfoundland. Journal of Structural Geology, 1998, 20(4): 459-471.

[31] Shao J A, Han Q J. Early Mesozoic Mantle-Crust Transitional Zone in Eastern Inner Mongolia: Evidence from Measurements of Compressional Velocities of Xenoliths at High Pressure and High Temperature. Science in China Series D: Earth Sciences, 2000, 30(Suppl.): 253-261.

[32] Shi Y R, Zhao X T, Ma Y S, . Late Jurassic-Early Cretaceous Plutonism in the Northern Part of the Precambrian North China Craton: SHRIMP Zircon U-Pb Dating of Diorites and Granites from the Yunmengshan Geopark, Beijing. Acta Geologica Sinica, 2009, 83(2): 310-320.

[33] Suo S T, Zhong Z Q, Zhou H W, . Multi-Stage Tectonic Exhumation Processes of Ultra High-Pressure (UHP) Metamorphic Rocks in the Dabie-Sulu Area, East-Central China. Earth Science-Journal of China University of Geosciences, 2012, 37(1): 1-17.

[34] Wang Q, Xu J F, Wang J X. The Recognition of Adakite-Type Gneisses in the North Dabie Mountain and Its Implication to Ultrahigh Pressure Metamorphic Geology. Chinese Science Bulletin, 2000, 45(21): 1927-1933.

[35] Wang T, Zheng Y D, Liu S W, . Mylonitic Potassic Granitoids from the Yagan Metamorphic Core Complex on Sino-Mongolian Border: A Mark of Transition from Contractile to Extensional Tectonic Regime. Acta Petrologica Sinica, 2002, 18: 177-186.

[36] Wang Y. The Onset of the Tan-Lu Fault Movement in Eastern China: Constraints from Zircon (SHRIMP) and ⁴⁰Ar/³⁹Ar Dating. Terra Nova, 2006, 18: 423-431.

[37] Webb L E, Leech M L, Yang T N. Hacker B R, McClelland W C, Liou J G. ⁴⁰Ar/³⁹Ar Thermochronology of the Sulu Terrane: Late Triassic Exhumation of High- and Ultrahigh-Pressure Rocks and Implications for Mesozoic Tectonics in East Asia. Ultrahigh-Pressure Metamorphism: Deep Continental Subduction, 2006, 77-92.

[38] Wu F Y, Sun D Y, Li H M, . A-Type Granites in Northeastern China: Age and Geochemical Constraints on Their Petrogenesis. Chemical Geology, 2002, 187(1–2): 143-173.

[39] Wu F Y, Walker R J, Ren X W, . Osmium Isotopic Constraints on the Age of Lithospheric Mantle beneath Northeastern China. Chemical Geology, 2003, 196(1–4): 107-129.

[40] Wu Y B, Zheng Y F, Zhou J B. Neoproterozoic Granitoid in Northwest Sulu and Its Bearing on the North China-South China Blocks Boundary in East China. Geophysical Research Letters, 2004, 31 L07616

[41] Xiong X L, Liu X C, Zhu Z M, . Adakitic Rocks and Destruction of the North China Craton: Evidence from Experimental Petrology and Geochemistry. Science China: Earth Sciences, 2011, 54(6): 858-870.

[42] Xu Y G. Thermo-Tectonic Destruction of the Archaean Lithospheric Keel beneath the Sino-Korean Craton in China: Evidence, Timing and Mechanism. Physics and Chemistry of the Earth Part A: Solid Earth and Geodesy, 2001, 26(9–10): 747-757.

[43] Xu Y G, Qin X F. Geochemistry and Geodynamics of Cenozoic Magmatism in NE China. Geochimica et Cosmochimica Acta, 2009, 73 13Suppl. A1466.

[44] Xu Z Q, Zhang Z M, Liu F L, . Exhumation Structure and Mechanism of the Sulu Ultrahigh-Pressure Metamorphic Belt, Central China. Acta Geologica Sinica, 2003, 77(4): 433-450.

[45] Yang J H, Wu F Y, Lo C H, . Deformation Age of Jurassic Granites in the Dandong Area, Eastern China: ⁴⁰Ar-³⁹Ar Geochronological Constraints. Acta Petrologica Sinica, 2004, 20(5): 1205-1214.

[46] Yang J H, Wu F Y, Chung S L, . Petrogenesis of Early Cretaceous Intrusions in the Sulu Ultrahigh-Pressure Orogenic Belt, East China and Their Relationship to Lithospheric Thinning. Chemical Geology, 2005, 222(3–4): 200-231.

[47] Yang T N, Chen W, Li J Y, . Exhumation History of the Su-Lu UHPM Terrene-Evidence from Dating and Deformation on Its Northern Boundary. Geological Review, 2002, 48(Suppl.1): 176-182.

[48] Ye K, Cong B L, Ye D N. The Possible Subduction of Continental Material to Depths Greater than 200 km. Nature, 2000, 407: 734-736.

[49] Zhang J J, Zheng Y D, Liu S W. Application of General Shear Theory to the Study of Formation Mechanism of the Metamorphic Core Complex: A Case Study of Xiaoqinling in Central China. Acta Geologica Sinica, 2000, 74(1): 19-28.

[50] Zhang L C, Liu T B, Shen Y C, . Structure, Isotopes, and ⁴⁰Ar/³⁹Ar Dating of the Pengjiakuang Gold Deposit, Mesozoic Jiaolai Basin, Eastern China. International Geology Review, 2003, 45(8): 691-711.

[51] Zhang Y Q, Dong S W, Shi W. Cretaceous Deformation History of the Middle Tan-Lu Fault Zone in Shandong Province, Eastern China. Tectonophysics, 2003, 363(3–4): 243-258.

[52] Zheng J P, Tang H Y, Zhao J H, . Age, Trace Elements and Hf-Isotope Composition of Zircon in Eclogites from the Sulu UHP Belt, East-Central China: Neoproterozoic Intrusion and Subsequent Paleozoic and Early Mesozoic Metamorphism. Journal of Earth Science, 2010, 21(5): 598-622.

[53] Zhi X C, Peng Z C, Cheng D G, . The Longevity of Subcontinental Lithospheric Mantle beneath Jiangsu-Anhui Region. Science in China Series D: Earth Sciences, 2001, 44(12): 1110-1118.

[54] Zhou J, Wilde S A, Zhao G, . SHRIMP U-Pb Zircon Dating of the Wulian Complex: Defining the Boundary between the North and South China Cratons in the Sulu Orogenic Belt, China. Precambrian Research, 2008, 162(3–4): 559-576.

[55] Zhu G, Song Q Z, Wang D X, . Studies on ⁴⁰Ar/³⁹Ar Thermochronology of Strike-Slip Time of the Tan-Lu Fault Zone and Their Tectonic Implications. Science in China Series D: Earth Sciences, 2001, 44(11): 1002-1009.