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《Earth Science》 2017-12
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Tectonic Setting of Guandi Iron Deposit and Archean Crustal Growth of Helong Massif in NE China:Evidence from Petrogeochemistry,Zircon U-Pb Geochronology and Hf Isotope

Shang Qingqing;Ren Yunsheng;Chen Cong;Duan Mingxin;Sun Qi;Xue Shiyuan;College of Earth Sciences,Jilin University;Shenyang Center of Geology Survey,China Geological Survey;No.3 Gold Geological Party of CAPF;The 603 Team of Jilin Nonferrous Metal Geological Exploration Bureau;  
The Guandi iron deposit has been discovered and developed for several years and has been considered as a typical BIFtype iron deposit in Yanbian area,Northeast China.This deposit is located at the north part of the Helong massif,at the joint of the North China craton and the Xing'an-Mongolia orogenic belt.The stratiform and lenticular iron orebodies are dominantly hosted within the metamorphic rocks of Jiashan Formation,Anshan Group.In order to determine the formation age,metamorphic age and tectonic setting of the Guandi deposit,in this paper,the geochemistry,LA-ICP-MS zircon U-Pb dating and zircon Hf isotope for the ore-hosting plagiogneiss,amphibole plagiogneiss and amphibolite were conducted.The results indicate thatthe protolith of the plagiogneiss is rhyodacite and dacite pyroclastic rock,the protolith of the amphibole plagiogneiss is andesite,the protolith of the amphibolite is basalt.The LA-ICP-MS zircon U-Pb dating data imply that the Guandi area experienced the late Neoarchean to early Paleoproterozoic magmatic event(ca.2 508~2 483 Ma)and metamorphic event(ca.2 472~2 459 Ma),both of which have closely genetic relationship with the iron formation of the Guandi iron deposit.Geochemical characteristics of the ore-hosting amphibolite indicate that they formed in the back-arc basin setting,which is also interpreted as the tectonic setting of the Guandi iron deposit.TheεHf(t)values of zircon grains from amphibole plagiogneiss range from-5.0 to +4.2,and the corresponding two-stage Hf model ages(tDM2)are from 3 182 Ma to 2 889 Ma,both of which indicate that the initial magma was mainly derived from the partial melting of the Mesoarchean crust.On the basis of comparison with several representative banded iron formations(BIFs)at home and abroad,it can be concluded that the Guandi iron deposit belongs to the Algoma-type BIFs,and was caused by the late Neoarchean large-scale BIF metallogenic event,which were widely developed in the North China craton.The Guandi area took place a crustal growth event at the early Neoarchean(2.8-2.7 Ga).Moreover,this paper proposes that the Helong massif has affinities to the North China Craton,which provides new evidence for the eastward termination of the Solonker-Xar Moron-Changchun suture in the Yanbian area.
【Fund】: 国家重点基础研究发展计划973课题(No.2013CB429802);; 吉黑东部地区资源远景调查评价(No.12120113098300)
【CateGory Index】: P59;P618.31
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