Petrology and geochemistry of the Wangjiazhuang banded iron formation and associated supracrustal rocks from the Wutai greenstone belt in the North China Craton:Implications for their origin and tectonic setting
作者单位：Key Laboratory of Mineral ResourcesInstitute of Geology and GeophysicsChinese Academy of Sciences University of Chinese Academy of Sciences Guangzhou Institute of GeochemistryChinese Academy of Sciences
会议名称：《中国科学院地质与地球物理研究所2014年度（第14届）学术年会》
会议日期：2015年
学科分类：081803[工学-地质工程] 0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 08[工学] 0818[工学-地质资源与地质工程]
基 金：supported by the Major State Basic Research Programme of the People’s Republic of China(No.2012CB416601) the Knowledge Innovation Programme of the Chinese Academy of Sciences(No.KZCX2-YW-Q04-07)
关 键 词：Wutai greenstone belt Algoma-type BIF Tectonic setting of the BIF Neoarchean North China Craton(NCC)
摘 要：The Wutai greenstone belt(WGB) is one of the most extensively studied greenstone belts in *** with the Hengshan and Fuping complexes,these three associations compose the central segment of the Trans-North China Orogen(TNCO) in the North China Craton(NCC).The Wangjiazhuang banded iron formation(BIF) is located in the bottom of the Jingangku Formation of the *** associated supracrustal rocks consist of meta-basalts(amphibolites),meta-felsic volcanic rocks(leptynite)and metapelites(mica schist),which have experienced amphibolite-facies *** are commonly intercalated with the BIF,SIMS zircon U-Pb analyses on amphibolites suggest that the Wangjiazhuang BIF was formed at ca.2543±4 *** with most Neoarchean Algoma-type Bits in the NCC,these features indicate that a significant tectothermal event of the NCC have occurred *** assemblages of the Wangjiazhuang BIF are composed of quartz,magnetite,amphibole,and minor garnet,pyrite and *** precursor deposts of this BIF were likely feiric-oxyliydroxides,fine-grained carbonate oozes,silicate phases rich in Al-Ca-Mg-Fe and amorphous *** appearance of garnet and ferro-pargasite,high concentrations of AlO,HFSEs,Sc,and positive correlations among AIO,TiO,HFSEs and REE indicate that there was a significant terrigenous *** so,the Wangjiazhuang BIF samples display distinctively seawater-like REE+Y profiles,characterized by positive La and Y anomalies and HREE enrichment relative to LREE in PAAS-normalized REE *** positive Eu anomalies are also observed,which are typically from high-T hydrothermal *** addition,the true negative Ce anomalies recorded in the Wangjiazhuang BIF might indicate the onset of bottomwater oxidation at the Archean-Ptoterozoic boundary,at least in restricted *** have geochemical affinity with both MORB- and arc-like components,and the trace element characteristics of Icptynitcs are also consistent wi