Neoarchean granitic rocks from the Jiamiao area of the Dabie orogen:Implications on the formation and early evolution of the Yangtze Craton  

作　　者：Yang TIAN Wei WANG Wei JIN Yuanbao WU Jing WANG Xin DENG Sifang HUANG 

机构地区：[1]Wuhan Center of Geological Survey,China Geological Survey,Wuhan,430205,China [2]State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,Wuhan,430074,China [3]Research Center for Petrogenesis and Mineralization of Granitoid Rocks,China Geological Survey,Wuhan,430205,China [4]Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037,China [5]Department of Surveying and Planning,Shangqiu Normal University,Shangqiu,476000,China

出　　处：《Science China Earth Sciences》2022年第8期1568-1585,共18页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.41972242);the Regional Geological Survey Project of China Geological Survey(Grant Nos.DD20190050&DD20221634);the Open Fund of the Research Center for Petrogenesis and Mineralization of Granitoid Rocks(Grant Nos.PMGR202002&PMGR202112)。

摘　　要：Archean rock exposures in the Yangtze Craton of South China are scarce and have been only studied in small-scale outcrops for understanding its early crustal evolution.Geological investigations have been carried out for three Neoarchean gneissic granitic plutons from the Dabie orogen in the northeastern margin of the Yangtze Craton.Zircon U-Pb geochronology constrains the emplacement of high-K monzogranite at 2645±30 Ma,high-K syenogranite at 2630±37 Ma and Na-rich granodiorite at 2497±29 Ma.These findings provide direct evidence for the existence of∼2.7-2.5 Ga rocks in the Dabie orogen,which significantly contribute to the distribution and evolution of Neoarchean basement rocks in the Yangtze Craton.Zircon crystals from the three granite samples giveεHf(t)values of−0.9 to 3.7,−4.2 to−0.4 and−4.7 to 0.1,respectively,corresponding to T_(DM2) ages of 3186-2909,3372-3141 and 3297-3005 Ma.The magmatic zircons have δ^(18)O values of 5.06±0.27‰to 5.79±0.30‰(average 5.59‰),6.14±0.24 to 7.35±0.26‰(average 6.87‰)and 5.95±0.17‰to 7.09±0.17‰(average 6.55‰),respectively.Considering the possible decrease of δ^(18)O value due to the lead loss during post-crystallization alteration,the primary δ^(18)O values might be substantially higher than those of the normal mantle zircon value(δ^(18)O=5.3±0.6‰).These isotopic data indicate that the Jiamiao Neoarchean granites were largely generated through reworking of Paleo-Mesoarchean basement rocks with a minor contribution of supracrustal material.Integrating our findings with previous results,we infer that the Archean-Paleoproterozoic complexes/terranes of the Yangtze Craton have distinct petrogenesis and the timings of the transition from Na-rich to high-K granites,crustal growth,and tectonothermal evolution before∼2.0 Ga.However,all of them underwent metamorphism at about 2.0 Ga.These observations also reveal that the Yangtze Craton might comprise several microcontinents that evolved individually and collided to form a unified craton at�

关 键 词：Zircon U-Pb age Hf-O isotopes NEOARCHEAN Dabie orogen Yangtze Craton 

分 类 号：P534.4[天文地球—古生物学与地层学] P588.121[天文地球—地质学] P542