TY - JOUR
T1 - Recycling of oceanic crust from a stagnant slab in the mantle transition zone
T2 - Evidence from Cenozoic continental basalts in Zhejiang Province, SE China
AU - Li, Yan Qing
AU - Ma, Chang Qian
AU - Robinson, Paul T.
AU - Zhou, Qin
AU - Liu, Ming Liang
N1 - Funding Information:
We would like to thank the editor in chief Dr. Andrew Kerr and two anonymous reviewers for their constructive and thoughtful comments, Dr. Jianqiang Liu for helpful discussions, which have improved the revised manuscript. We thank Peng Lu, Hong-An Jiang, Jun Wang for assisting in the field trip and sample preparation. Bulk-rock major and trace element analyses were supported by Xi-Yao Li, Hai-Hong Chen; Lian Zhou, Huan-Ling Lei, Zuo-Min Zhou and Yu Pu assisted with whole-rock Sr–Nd–Pb isotope measurements; He Rong and Ye Li provide help with the mineral compositions analyses. We are grateful to Jie Li, PeiPei Zhao and Lu Yin for their help with the Re–Os analyses. The authors gratefully acknowledge the financial support from National Science Foundation of China (grant: 41272079 ).
Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/8/1
Y1 - 2015/8/1
N2 - Cenozoic continental basalts from Zhejiang Province, southeast China are tholeiitic to weakly alkalic in composition, with moderate MgO contents (6-11wt.%) and an average Mg# of 62. They display typical OIB-like trace element features, including enrichment in most incompatible elements, both LILE and LREE, and negative K, Pb, Zr, Hf anomalies. In particular, they are characterized by high Fe/Mn (73±5), La/Yb (19±6) and Nb/Ta (18.8±0.4) ratios, which can be attributed to the presence of residual clinopyroxene, garnet and rutile in the mantle source. Based on these minerals, the following hybrid source rocks are hypothesized: garnet pyroxenite/eclogite and peridotite. Clinopyroxene-liquid thermobarometry indicates clinopyroxene crystallization temperatures of >1257°C. This is higher than the assumed temperature at the base of the sub-continental lithospheric mantle (SCLM) (~1220°C) beneath Zhejiang, thus the magmas were presumably derived from the asthenosphere. Some typical geochemical features such as negative K, Pb anomalies, positive Ba, Sr, Nb, Ta anomalies and the extremely high Os isotopic signatures, suggest participation of EM-like mantle sources, indicative of ancient subducted oceanic crust. (87Sr/86Sr)i (0.7037-0.7046) and 143Nd/144Nd (0.512832-0.512990) isotope ratios point to the presence of mixed components in the source region, i.e., DMM, EM1 and EM2. Recent seismic tomographic images of the mantle beneath Zhejiang suggest the presence of a subducted slab of oceanic lithosphere in the transition zone. Based on the combined geophysical and geochemical evidence, we propose that the major source of the Zhejiang basaltic magmas was the ancient subducted oceanic slab in the transition zone with an EM-like signature. The other magma sources include depleted asthenospheric peridotite possessing a DMM-like signature. The dynamics of this upwelling hybrid magma was apparently related to westward subduction of the Pacific plate underneath the eastern Asian continent. This process may have triggered the widespread Cenozoic volcanism related to the lithospheric thinning in East China in the Mesozoic and Cenozoic.
AB - Cenozoic continental basalts from Zhejiang Province, southeast China are tholeiitic to weakly alkalic in composition, with moderate MgO contents (6-11wt.%) and an average Mg# of 62. They display typical OIB-like trace element features, including enrichment in most incompatible elements, both LILE and LREE, and negative K, Pb, Zr, Hf anomalies. In particular, they are characterized by high Fe/Mn (73±5), La/Yb (19±6) and Nb/Ta (18.8±0.4) ratios, which can be attributed to the presence of residual clinopyroxene, garnet and rutile in the mantle source. Based on these minerals, the following hybrid source rocks are hypothesized: garnet pyroxenite/eclogite and peridotite. Clinopyroxene-liquid thermobarometry indicates clinopyroxene crystallization temperatures of >1257°C. This is higher than the assumed temperature at the base of the sub-continental lithospheric mantle (SCLM) (~1220°C) beneath Zhejiang, thus the magmas were presumably derived from the asthenosphere. Some typical geochemical features such as negative K, Pb anomalies, positive Ba, Sr, Nb, Ta anomalies and the extremely high Os isotopic signatures, suggest participation of EM-like mantle sources, indicative of ancient subducted oceanic crust. (87Sr/86Sr)i (0.7037-0.7046) and 143Nd/144Nd (0.512832-0.512990) isotope ratios point to the presence of mixed components in the source region, i.e., DMM, EM1 and EM2. Recent seismic tomographic images of the mantle beneath Zhejiang suggest the presence of a subducted slab of oceanic lithosphere in the transition zone. Based on the combined geophysical and geochemical evidence, we propose that the major source of the Zhejiang basaltic magmas was the ancient subducted oceanic slab in the transition zone with an EM-like signature. The other magma sources include depleted asthenospheric peridotite possessing a DMM-like signature. The dynamics of this upwelling hybrid magma was apparently related to westward subduction of the Pacific plate underneath the eastern Asian continent. This process may have triggered the widespread Cenozoic volcanism related to the lithospheric thinning in East China in the Mesozoic and Cenozoic.
KW - Cenozoic basalt
KW - Petrogenesis
KW - Recycled oceanic slab
KW - Stagnant ancient slab
KW - Zhejiang
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U2 - 10.1016/j.lithos.2015.05.021
DO - 10.1016/j.lithos.2015.05.021
M3 - Article
AN - SCOPUS:84931262492
SN - 0024-4937
VL - 230
SP - 146
EP - 165
JO - Lithos
JF - Lithos
ER -