Seamounts accretion is one of the most significant accretionary orogenic processes in the Central Asian Orogenic Belt, but there are few paleo‐seamounts reported from northern West Junggar and debates on 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 northern West Junggar. Zircon U–Pb dating on a basalt yields a weighted mean 206Pb/238U age of 469 ± 7 Ma, which suggests that it formed in the Middle Ordovician. All basalt samples belong to alkaline basalt and show similar geochemical characteristics. They display high TiO2 (∼3 wt%), (La/Yb)N (17.6–19.0) and ΣREE (232–289 ppm) and enrichment in Nb and Ta, which implies for their 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, we suggest that the Chagantaolegai OIB samples were likely derived from a fertile mantle source related to plume. The rock assemblage of OIB, 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.

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206pb238u tio2 3 wt laybn 176190 accretion accretionary orogenic mineralogical geochemical 87sr86sr 070425 ree 232289 ppm nd t 416

Haitao MA,Jiafu CHEN, Junlai LIU, Bo LIU, Rongyan LI, Baofu HAN,.Petrogenesis and Tectonic Implications of Middle Ordovician Ocean Island Basalts from the Chagantaolegai Ophiolitic Mélange in Northern West Junggar, NW China. (),.

Haitao MA, et al."Petrogenesis and Tectonic Implications of Middle Ordovician Ocean Island Basalts from the Chagantaolegai Ophiolitic Mélange in Northern West Junggar, NW China"

Haitao MA,Jiafu CHEN, Junlai LIU, Bo LIU, Rongyan LI, Baofu HAN,"Petrogenesis and Tectonic Implications of Middle Ordovician Ocean Island Basalts from the Chagantaolegai Ophiolitic Mélange in Northern West Junggar, NW China"