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首页|期刊导航|地质学报(英文版)|Petrogenesis and Tectonic Implications of the Early Triassic Nianzi Adakitic Granite Unit in the Yanshan Fold and Thrust Belt:New Constraints from U-Pb Geochronology and Sr-Nd-Hf Isotopes

Petrogenesis and Tectonic Implications of the Early Triassic Nianzi Adakitic Granite Unit in the Yanshan Fold and Thrust Belt:New Constraints from U-Pb Geochronology and Sr-Nd-Hf IsotopesOACSTPCD

Petrogenesis and Tectonic Implications of the Early Triassic Nianzi Adakitic Granite Unit in the Yanshan Fold and Thrust Belt:New Constraints from U-Pb Geochronology and Sr-Nd-Hf Isotopes

英文摘要

The Nianzi granite unit,which includes the Nianzi,Xiaolianghou and Xiawopu granitic intrusions,is a significant component of the northern part of the North China Craton(NCC)and is situated in the Yanshan fold and thrust belt(YFTB).However,there is still debate regarding the tectonic evolutionary history of the YFTB during the late Permian to Triassic period,specifically regarding the timing of subduction and collision between the NCC and the Paleo-Asian Ocean.The Nianzi granite unit exhibits unique petrological,geochronological and geochemical signatures that shed light on the tectonic evolutionary history of the YFTB.This study presents detailed petrology,whole-rock geochemistry,together with Sr-Nd isotopic,zircon U-Pb dating and Lu-Hf isotopic data of the granites within the Nianzi granite unit.Our findings demonstrate that the granites primarily consist of subhedral K-feldspar,plagioclase,quartz,minor biotite and hornblende,with accessory titanite,apatite,magnetite and zircon.Zircon U-Pb dating indicates that the Xiaolianghou granite was emplaced at 247.5±0.62 Ma.Additionally,the adakitic characteristics of the Nianzi,Xiawopu and Xiaolianghou granitic intrusions,such as high Sr and Ba contents and high ratios of Sr/Y and(La/Yb)N,combined with negative Sr-Nd and Lu-Hf isotopes(87Sr/86Sr)i = 0.705681-0.7057433,εNd(t)=-21.98 to-20.97,zircon εHf(t)=-20.26 to-9.92),as well as the I-type granite features of high SiO2,Na2O and K2O/Na2O ratios,enriched Rb,K,Sr and Ba,along with depleted Th,U,Nb,Ta,P and Ti,suggest that the Nianzi granitic unit was mainly derived from the partial melting of a thickened lower crust containing hydrous,calc-alkaline to high-K calc-alkaline,mafic to intermediate metamorphic rocks.In light of these parameters,we further integrate our data with previous studies and conclude that the Nianzi granitic unit was generated in a post-collisional extensional environment during the Early Triassic.

ZHANG Huijun;WU Chu;HE Fubing;WANG Biren;CUI Yubin;LIU Zhenghua;YOU Shina;DONG Jing

Development and Research Center of the China Geological Survey,Beijing 100037,ChinaBeijing Institute of the Geological Survey,Beijing 100095,ChinaInstitute of Disaster Prevention,Langfang,Hebei 065201,China

tectonic evolutionzircon geochronologySr-Nd-Hf isotopesNianzi granite unitYanshan fold and thrust belt

《地质学报(英文版)》 2024 (001)

50-66 / 17

This study was funded by the National Natural Science Foundation of China(41872232),the Beijing Geological Survey Project(PXM 2016-158203-000008,PXM 2018-158203-000014)and the Beijing Innovation Studio(Urban Geology,Active Structure,and Monitoring).We thank the editors and anonymous reviewers for their insightful and constructive comments.We acknowledge Dai Bing and Li Yue for their support during the modification of this manuscript and for their professional input.

10.1111/1755-6724.15112

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