Mesoproterozoic Magmatic Events And Mineralization In The North China Craton

The North China Craton underwent complicate and multistage tectonic evolutionduring early Precambrian period, and then went into a pediocratic time when the thicksedimentary cover developed since1.8Ga. Accompanying with theMid-Mesoproterozoic sedimentation, a series of thermotectonic events related tobreakup of the Columbian supercontinent occurred. The North China Craton almostbecame the most developed area of thermotectonic events during the period of1.80~1.00Ga(Mesoproterozoic).Mesoproterozoic breakup events in the North China Craton can be included intofive peak periods in ascending order: PeakⅠoccurred during1.80~1.77Ga and wasrepresented by Xionger volcanic and mafic dyke swarms in Wutai mountain andHengshan area; PeakⅡ followed during1.72~1.67Ga and was dominated by AMCGassemblage, including Damiao anorthosite,Miyun rapakivi granites,Chicheng rapakivigranites,Lanying syenite, Gubeikou alkali granite, Laowa monzogranite and quartzmonzonite, Jianping gabbro,diorite,monzonite, quartz syenite and charnockite,andGuyang quartz syenite et al.; Peak Ⅲ occurred during1.63~1.62Ga, such asDahongyu K-rich volcanic, Longwangzhuang alkaline granite in the southern marginof the North China and gabbro-diabase dykes in the Mount Tai of the westernShandong Province; Peak Ⅳ was during the time of1.33~1.30Ga,for example, maficdykes(sills) which intruded into Xiamaling Formation and Wumishan Formation,(monzonitic) granite in the area of Shangdu,Huade and Kangbao, and Bayan Obobeforsite; Peak Ⅴ happened at about1.23Ga, and buried mafic dyke in EasternHebei Province was typical.In this paper, further research on the breakup events of1.72~1.67Ga,1.63~1.62Ga,1.33~1.30Ga and about1.23Ga period are introduced.On the base of high precision date from experiment, accurate chronologicalframework of Mesoproterozoic breakup events in the North China Craton is builded,which deepens our cognition on the events, and conduces to build the magmatic events sequence this time. Dates will be introduced in detail as following: zirconLA-ICPMS U-Pb isotopic ages of Laowa monzogranite and quartz monzonite are1695±12Ma and1696±12Ma respectively; zircon SHRIMP、MC-LA-ICPMSU-Pb isotopic age of intrusive rock in Jianping area is1692~1714Ma; zirconLA-MC-ICPMS、SHRIMP U-Pb isotopic ages of granite-prophyry dyke which isunconformably overlain by the conglomerate and sandstone of the ChangzhougouFormation are1673±10Ma and1669±20Ma; zircon SHRIMP U-Pb isotopic age ofGuyang quartz syenite is1702±31Ma; baddeleyite SIMS、ID-TIMS U-Pb isotopicages of the gabbro-diabase dike in the Hongmen scenic region of Mount Tai are1632.4±4.2Ma and1621.1±8.8Ma respectively; age of monzonitic granite fromKangbao area is1335±4Ma, and baddeleyite ID-TIMS U-Pb isotopic age of themafic dyke which intruded into Xiamaling Formation is1320±6Ma; baddeleyiteSIMS Pb-Pb isotopic age of buried mafic dyke in Luannan region of Eastern HebeiProvince is1228.3±4.0Ma.In reviewing of feature of regional geology and sequence of sedment evolution,in this paper, we discuss the nature and characters of breakup events, the features ofmineralization related to magmatic events in Mesoproterozoic period on the NorthChina Craton and the tectonic significance of these magmatic evens which wereepisodic. The ones of1.80~1.77Ga,1.72~1.67Ga,1.63~1.62Ga are the record ofprimary breakup of the Columbian supercontinent, while other events during1.33~1.30Ga and1.23Ga represent the late period of supercontinent breakup. Themineralization of Damiao vanadic titanomagnetite and Bayan Obo Fe-REE-Nbdeposits are closely correlated to Mesoproterozoic magmatic evens.