U-Pb-Hf-O-Nd isotopic and geochemical constraints on the origin of Archean TTG gneisses from the North China Craton: Implications for crustal growth

Li, Zhuang1,2,5,6; Wei, Chunjing3; Chen, Bin4; Zhang, Wei1,2; Yang, Fan1,2

2021-03-01

10.1016/j.precamres.2020.106078

PRECAMBRIAN RESEARCH   影响因子和分区

0301-9268

1872-7433

Tonalite-trondhjemite-granodiorite (TTG), an Archean dominant lithological assemblage within the cratonic provinces, is believed to have been formed by partial melting of the hydrous basalts in the garnet stability field. The origin of TTG is a window to decipher the evolution of Archean continental crust, whereas the petrogenesis is not well constrained. To solve this issue, we have carried out field observations, zircon U-Pb-Hf-O isotope, as well as whole-rock Nd-O isotope and geochemical analyses on the TTG and associated dioritic gneisses from the North China Craton. U-Pb isotopic dating using the LA-ICP-MS on zircons reveals that the granitoid gneisses in northern Liaoning were contemporaneously generated during ca. 2.56-2.51 Ga and immediately experienced a regional metamorphic event at 2.48-2.45 Ga. The dioritic gneisses occur as quenched inclusions with rounded to ellipsoidal globules in shape rather than lithospheric relics. Such occurrence, together with isotopic and geochemical data, suggests that the mafic enclaves and host TTG represent two co-existing, compositionally distinct magmas. The TTG gneisses are featured by elevated SiO2 (64.72-86.46 wt%) contents, (La/Yb)(N) (68 on average) and Sr/Y (119 on average) ratios, and low MgO (0.35-2.58 wt%) contents and Mg-# values, with radiogenic Hf and Nd isotopes (epsilon(Hf)(t) = +3.5 to +9.0 and epsilon(Nd) (t) = +0.8 to +5.4), indicating the derivation from partial melting of the juvenile basaltic sources at lower crustal levels. Compared with the TTG gneisses, the dioritic gneisses have lower SiO2 contents, higher MgO contents and Mg-# values, with similar Hf-Nd isotopes (epsilon(Hf)(t) = +3.6 to +9.5 and epsilon(Nd)(t) = +3.3 to +5.1), implying the depleted mantle source. A model is proposed whereby partial melts from juvenile basaltic sources evolved via mixing with mafic enclaves (viz. dioritic magma) and fractional crystallization, and finally were contaminated by the sedimentary rocks, forming the TTG magma. The granitoid gneisses in northern Liaoning witnessed the major vertical growth of continental crust at the end of the Neoarchean, which is supported by Hf-Nd-O isotopic data and zircon Hf-O isotopic modeling. Our results show that the geochemistry of TTG (such as elevated La/Yb and Sr/Y) might be affected by complex petrogenetic processes, i.e., partial melting of individual sources, magma mixing, fractional crystallization, and crustal contamination, rather than solely controlled by the P-T conditions of crustal anataxis as previously thought, which might have been also overlooked in other Archean cratons.

U-Pb-Hf-O-Nd isotope TTG Neoarchean Crustal growth North China Craton

SCI

英语

其他

Science Foundation of China University of Petroleum, Beijing[2462017YJRC032] ; National Natural Science Foundation of China[42002238,41872057]

Geology

Geosciences, Multidisciplinary

WOS:000615712000029

ELSEVIER

GEOSCIENCES

Web of Science

1.China Univ Petr, State Key Lab Petr Resources & Prospecting, Beijing 102249, Peoples R China
2.China Univ Petr, Coll Geosci, Beijing 102249, Peoples R China
3.Peking Univ, Sch Earth & Space Sci, Key Lab Orogen Belts & Crustal Evolut, MOE, Beijing 100871, Peoples R China
4.Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen 518055, Peoples R China
5.Hebei GEO Univ, Key Lab Reg Geol & Mineralizat, Shijiazhuang 050031, Hebei, Peoples R China
6.Minist Nat & Resources, Key Lab Mineral Resources Evaluat Northeast Asia, Changchun 130061, Peoples R China

Li, Zhuang,Wei, Chunjing,Chen, Bin,et al. U-Pb-Hf-O-Nd isotopic and geochemical constraints on the origin of Archean TTG gneisses from the North China Craton: Implications for crustal growth[J]. PRECAMBRIAN RESEARCH,2021,354.

Li, Zhuang,Wei, Chunjing,Chen, Bin,Zhang, Wei,&Yang, Fan.(2021).U-Pb-Hf-O-Nd isotopic and geochemical constraints on the origin of Archean TTG gneisses from the North China Craton: Implications for crustal growth.PRECAMBRIAN RESEARCH,354.

Li, Zhuang,et al."U-Pb-Hf-O-Nd isotopic and geochemical constraints on the origin of Archean TTG gneisses from the North China Craton: Implications for crustal growth".PRECAMBRIAN RESEARCH 354(2021).