CHEN Jiafu
1 Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Department of Geology, Northeastern University, Shenyang 110819, China 2 Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles 90095, USALI Rongyan
1 Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Department of Geology, Northeastern University, Shenyang 110819, China 2 Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles 90095, USAMA Haitao
1 Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Department of Geology, Northeastern University, Shenyang 110819, China 2 Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles 90095, USAHAN Baofu
3 Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, ChinaLIU Junlai
4 State Key Laboratory of Geological Process and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, ChinaWe thank Dr. Zheng Changqin, Dr. Hou Kejun, Dr. Ma Xu, Dr. Feng Lixia and Dr. Zheng Bo for their assistance in the field and during indoor analyses. This work was supported by the National Science Foundation of China (Grant No. 41672217), the Fundamental Research Funds for the Central Universities (Grant No. N170104022), and the State Scholarship Fund (Grant No. 201806085034).
Seamount accretion is one of the most significant accretionary orogenic processes in the Central Asian Orogenic Belt, but there are few paleo-seamounts reported from and debate on the tectonic evolution of the Junggar Ocean still exists. In this study, we present geochronological, mineralogical, geochemical and isotopic data for basalts from the Chagantaolegai ophiolitic mélanges in Junggar. Zircon U-Pb dating on one basalt yielded a weighted mean 206Pb/238U age of 469 ± 7 Ma, which suggests that it formed in the Middle Ordovician. All rock samples belong to alkaline basalt and show similar geochemical characteristics, displaying high TiO2 (~3 wt%), (La/Yb)N (17.6–19.0), ΣREE (232–289 ppm) and enrichment in Nb and Ta, which implies an ocean island basalt (OIB) affinity. Based upon positive εNd(t) (+4.16 to +4.23), ΔNb (0.20–0.22) and low initial 87Sr/86Sr (0.70425 to 0.70452) and Zr/Nb (3.35–3.57), we suggest that the Chagantaolegai OIB samples were likely derived from a fertile mantle source related to plume. The OIB rock assemblage, chert and marble in the southern part of the Chagantaolegai ophiolitic mélange indicates that a Middle Ordovician seamount was accreted to the Boshchekul-Chingiz arc due to the northward subduction of the Junggar-Balkhash Ocean.
CHEN Jiafu, LI Rongyan, MA Haitao, HAN Baofu, LIU Junlai.2021. Petrogenesis and Tectonic Implications of Middle Ordovician Ocean Island Basalts from the Chagantaolegai Ophiolitic Mélange in Junggar, NW China[J]. Acta Geologica Sinica(),95(4):1099-1111
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