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The Early Carboniferous Xiaomiaogou granite porphyry dykes in the northern margin of the North China Craton: implication for crust–mantle interaction and intraplate magmatism
Author(s) -
Wang Liang,
Wang Genhou,
Lei Shibin,
Qing Min,
Jia Liqiong,
Chang Chunjiao,
Kang Jiankun,
Hou Wanrong
Publication year - 2016
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.2780
Subject(s) - craton , geology , geochemistry , zircon , petrogenesis , partial melting , magmatism , crust , mantle (geology) , geochronology , intraplate earthquake , continental crust , basalt , carboniferous , petrology , paleontology , structural basin , tectonics
The age, petrogenesis and geodynamic implication of Xiaomiaogou granite porphyry dykes in the northern margin of the North China Craton were investigated using geochronology, geochemistry and Sr–Nd–Pb–Hf isotopic data. LA‐MC‐ICP‐MS zircon U–Pb dating yielded the concordant 206 Pb/ 238 U weighted mean age of 350.4 ± 1.4 Ma for the dykes, suggesting they were the productions of the Early Carboniferous magmatism in the northern margin of the North China Craton. The granite porphyries display the pronounced A‐type affinities: apart from higher zircon saturation temperature, they are high‐K calc‐alkaline and metaluminous, with high concentrations of K 2 O + Na 2 O varying from 7.93 to 8.55 wt.%, incompatible elements (e.g. Zr, Y, Nb and Ce), REEs and 10 000 Ga/Al ratios but less obvious LREE and HREE fractionation. With the lower initial 87 Sr/ 86 Sr ratios (0.7055 to 0.7070), negative values of ε Nd ( t ) (−7.1 to −4.9) and ε Hf ( t ) (−11.2 to −8.0) and old Nd (1505 to 1681 Ma) and Hf (1861 to 2061 Ma) model ages, all the rocks exhibit the similar geochemical compositions to the melts obtained in experimental studies by dehydration melting of meta‐basalts, implying a lower continental crust origin. However, the high Mg # values (47.53 to 53.60) and subcontinental lithospheric mantle‐like ε Nd ( t ), ε Hf ( t ) and Pb isotopic compositions (( 206 Pb/ 204 Pb)i = 17.296–17.766, ( 207 Pb/ 204 Pb)i = 15.460–15.490 and ( 208 Pb/ 204 Pb)i = 37.097–37.568) indicate the involvement of melts from subcontinental lithospheric mantle. Combined with the special features of mafic microgranular enclaves occurring within the granite porphyries, mixing of the lower crust and subcontinental lithospheric mantle of the North China Craton is proposed for the genesis of granite porphyry dykes in this study. During the hybrid magma ascending, pronounced fractional crystallization and crustal assimilation may have also occurred. Based on geochemical criteria, the Xiaomiaogou granite porphyries can be classified into A 1 group. Characterized by the compositional features of anorogenic granites, an intraplate setting is envisaged for the formation of Xiaomiaogou granite porphyry dykes. Such a tectonic environment may be related to the northward drift of the North China Craton during rifting away from East Gondwana. Copyright © 2016 John Wiley & Sons, Ltd.