Petrogenesis and Tectonic Implications of Middle Ordovician Ocean Island Basalts from the Chagantaolegai Ophiolitic Mélange in Junggar,NW China  

作　　者：CHEN Jiafu LI Rongyan MA Haitao HAN Baofu LIU Junlai 

机构地区：[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,USA [3]Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China [4]State Key Laboratory of Geological Process and Mineral Resources,School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China

出　　处：《Acta Geologica Sinica(English Edition)》2021年第4期1099-1111,共13页地质学报（英文版）

基　　金：supported by the National Science Foundation of China(Grant No.41672217);the Fundamental Research Funds for the Central Universities(Grant No.N170104022);the State Scholarship Fund(Grant No.201806085034)。

摘　　要：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^(206)Pb/^(238)U 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 TiO_(2)(~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 positiveεN d(t)(+4.16 to+4.23),ΔNb(0.20–0.22)and low initial^(87)Sr/^(86)Sr(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.

关 键 词：ocean island basalt SEAMOUNT Middle Ordovician CAOB West Junggar 

分 类 号：P588.145[天文地球—岩石学]