古元古代胶-辽-吉带造山后转换机制:来自青城子地区花岗岩体年代学与地球化学特征的制约  

Orogenic to post-orogenic transition of the Paleoproterozoic Jiao-Liao-Ji Belt:Constraints from geochronology and geochemistry of the granites in the Qingchengzi area

作　　者：马玉波[1] 张勇[1] 李立兴[1] 沈宏飞 MA YuBo;ZHANG Yong;LI LiXing;SHEN HongFei(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《岩石学报》2022年第10期2971-2987,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42072112、41202042);国家重点研发计划项目(2017YFC0601303);中央级公益性科研院所基本科研业务费专项资金资助项目(KK2124、KK2105)联合资助。

摘　　要：胶-辽-吉带是华北克拉通最具代表性的一条古元古代造山带,巨量古元古代火山-沉积岩系和中酸性侵入岩体及少量镁铁质岩体发育其中。这些古元古代地质体形成后经受了多期岩浆/变质事件的改造,因此给该地区的前寒武纪研究带来很大的困扰。青城子地区位于胶-辽-吉带中段,以发育大量金、铅锌、银矿床受到广泛关注。尽管该地区经历了古元古代、中元古代-中三叠世和晚三叠世多期的构造-岩浆事件,但仍可以通过岩石学和年代学工作识别出数个古元古代花岗岩体,这些岩体为探讨古元古代胶-辽-吉带造山后转换机制提供了制约。本文仅选取该地区两个不同岩相的古元古代后造山花岗岩体进行了系统研究。锆石U-Pb年代学研究表明,大顶子岩体形成于1884±5Ma,并保留大量~2.1Ga继承锆石,而卧龙泉岩体形成于1878±4Ma,误差范围内与大顶子岩体一致。大顶子岩体高SiO_(2)、富Al_(2)O_(3)、低K_(2)O和TiO_(2)含量以及相对高MgO含量,表现出类似高铝埃达克质岩石的特征。卧龙泉岩体同样具有高SiO_(2)、富Al_(2)O_(3)和TiO_(2)含量以及相对高MgO含量,但具有明显高的K_(2)O含量,并不具备埃达克质岩石的地球化学特征。综合分析认为大顶子岩体形成于加厚下地壳的部分熔融,而卧龙泉岩体形成于下地壳部分熔融产生的熔体,并添加了少量来源于富集地幔的富闪岩浆,二者均对应于胶-辽-吉构造带由碰撞造山阶段向造山后伸展阶段的转折时期。The Jiao-Liao-Ji Belt is the most representative Paleoproterozoic belt in the North China Craton,which hosts huge amounts of Paleoproterozoic volcanic-sedimentary rocks,intermediate-felsic plutonic rocks and some mafic rocks.Multi-stage magmatic-metamorphic events occurred to these Paleoproterozoic geologic bodies,which resulted in great confusion about the understanding of the Precambrian geology of this belt.The Qingchengzi area,located in the middle of Jiao-Liao-Ji Belt,is characterized by its huge amounts of Au,Pb,Zn and Ag deposits.Although multi-stage tectonic magmatic events happened in Jiao-Liao-Ji Belt in Paleoproterozoic,Middle Proterozoic to Middle Triassic and Late Triassic in this area,several Paleoproterozoic granites were recognized by petrologic and geochronological work,which offer constraints on the transformation mechanism of the belt in Paleoproterozoic from orogenic period to post-orogeny.In this study,Paleoproterozoic granites with different facies(Dadingzi monzogranite and Wolongquan porphyritic biotite monzogranite)were chosen to study their petrologic,geochronological and geochemical features.SHRIMP zircon U-Pb geochronological analysis showed that the Dadingzi monzogranite was formed at 1884±5Ma with abundant inherited zircons aged 2.1Ga,whereas the Wolongquan monzogranite had an age of 1878±4Ma,which was synchronous to the Dadingzi monzogranite.Geochemically,the Dadingzi monzogranite is rich in SiO_(2)and Al_(2)O_(3),and poor in K_(2)O and TiO_(2),with a relatively high MgO content,which is similar to high aluminum adakite;while the Wolongquan porphyritic biotite monzogranite belongs to high Sr+Ba granite,which has high SiO_(2)and Al_(2)O_(3),and low TiO_(2)contents,with a relatively high MgO and obviously high K_(2)O,showing that it is not of adakite characteristics.Combined with the regional tectonic evolution,Hf isotopic and major-trace element compositions,we conclude that the Dadingzi intrusion resulted from partial melting of a thickened lower crust,whereas the Wolongquan intrus

关 键 词：古元古代花岗岩 SHRIMP锆石U-PB年龄 HF同位素 胶-辽-吉带 青城子地区 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]