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
Abstract：The Guandi iron deposit has been discovered and developed for several years and has been considered as a typical BIF-type 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,metamor-phic 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 that the protolith of the plagiogneiss is rhyodacite and dacite pyroclastic rock,the protolith of the amphibole plagiogneiss is andes-ite,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.2508 ~ 2483 Ma)and metamorphic event (ca.2472 ~2459 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 (t DM2 )are from 3182 Ma to 2889 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).Moreo-ver,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.
Keywords：Hf isotopezircon U-Pb datingcrustal growthGuandi iron depositHelong massifgeochemistry
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：21( 2208-2228 )