As part of the mosaic of micro-continents within the Central Asian Orogenic Belt(CAOB), the Xing’anAirgin Sum Block(XAB) features increasingly-recognized Meso-Neoproterozoic geological records. However, the origin, t...As part of the mosaic of micro-continents within the Central Asian Orogenic Belt(CAOB), the Xing’anAirgin Sum Block(XAB) features increasingly-recognized Meso-Neoproterozoic geological records. However, the origin, temporal-spatial distribution of ancient materials, and their roles in crust evolution remain to debate. This paper presents an integrated study of zircon U-Pb ages and Hf-O isotopes for Mesoproterozoic and Paleozoic granites from the Erenhot region of central Inner Mongolia, along eastern CAOB. The intrusion of 1450 Ma syenogranite denotes that the Precambrian basement of XAB extends from Sonid Zuoqi westward to Erenhot. The 384 and 281 Ma monzogranites containing Mesoproterozoic xenocrystic zircons possess Proterozoic-dominant two-stage Hf model ages, further suggesting the wide existence of Proterozoic crust beneath western XAB. Cyclic Proterozoic crustal growth and reworking seem to show close linkages with the orogenesis during relevant supercontinent cycles. 1450-1360 Ma juvenile crustal growth at Erenhot and synchronous ancient crust reworking at Sonid Zuoqi and Abagaqi were likely resulted from retreating subduction involved in Columbia breakup, while 1.2-1.0 Ga reworking and 0.9-0.7 Ga growth events within the Erenhot basement might respond to assembly and breakup of Rodinia, respectively. Besides, our work confirms that reworking of Neoproterozoic crust played important roles during Paleozoic multi-stage accretion of CAOB.展开更多
华南地区是我国重要的稀有金属矿产区,绝大部分具经济规模的稀有金属矿床均与高演化的富Li-F花岗岩有成因联系。大坪花岗斑岩位于南岭构造带最东缘福建省永定地区,与区内Nb-Ta矿床形成有关。该岩体SIMS和LA-ICP-MS锆石U-Pb定年结果分别...华南地区是我国重要的稀有金属矿产区,绝大部分具经济规模的稀有金属矿床均与高演化的富Li-F花岗岩有成因联系。大坪花岗斑岩位于南岭构造带最东缘福建省永定地区,与区内Nb-Ta矿床形成有关。该岩体SIMS和LA-ICP-MS锆石U-Pb定年结果分别为186.7±1.2Ma和190.7±1.1Ma,是华南少见的早侏罗世(200~180Ma)侵入的花岗岩侵入体,也是华南最早报道的早侏罗世稀有金属成矿事件。大坪花岗斑岩具高钾低镁、准铝质到弱过铝质的特征,属于高钾钙碱性花岗岩,并显示A型花岗岩的地球化学特征,如富硅(72.81%~76.44%)、高10000×Ga/Al比值、高FeO^T/MgO和高的Zr+Nb+Ce+Y含量、亏损高场强元素和Eu负异常明显等。全岩体系低的Zr/Hf、Nb/Ta比值,指示岩浆具有较高的分异演化程度,Nb 2 O 5和Ta 2 O 5均含量达到了花岗岩型稀有金属矿床的工业品位。花岗斑岩中锆石Hf-O同位素分析结果显示,其具有比较亏损的Hf同位素与比较均一的O同为素组成(εHf(t)=-2.4~3.4,δ^18 O=6.0‰~6.6‰)。结合微量元素地球化学特征,大坪花岗斑岩源区主要来源于软流圈地幔,并有约20%~30%壳源岩浆的加入,在成岩过程中发生了显著的分离结晶。晚期富氟的流体出熔并向上迁移可能对于Nb和Ta的再次富集与分异具有重要作用。大坪花岗斑岩与闽西南地区同时期的火山岩,如藩坑组双峰式火山岩,在空间上可与前人提出的“南岭山脉早侏罗世发育的东西向裂谷岩浆岩带(OIB型玄武岩、辉长岩和A型花岗岩组合)”相对应,是该裂谷带向东的延伸。展开更多
基金Projects(41873035,41802053) supported by the National Natural Science Foundation of ChinaProject(ZD2021015) supported by the Science and Technology Project of Hebei Education Department,China+1 种基金Project(SCRM2116) supported by the Opening Foundation of Hebei Key Laboratory of Strategic Critical Mineral Resources,ChinaProject(202045004) supported by the Scientific Research Starting Foundation of Central South University,China。
文摘As part of the mosaic of micro-continents within the Central Asian Orogenic Belt(CAOB), the Xing’anAirgin Sum Block(XAB) features increasingly-recognized Meso-Neoproterozoic geological records. However, the origin, temporal-spatial distribution of ancient materials, and their roles in crust evolution remain to debate. This paper presents an integrated study of zircon U-Pb ages and Hf-O isotopes for Mesoproterozoic and Paleozoic granites from the Erenhot region of central Inner Mongolia, along eastern CAOB. The intrusion of 1450 Ma syenogranite denotes that the Precambrian basement of XAB extends from Sonid Zuoqi westward to Erenhot. The 384 and 281 Ma monzogranites containing Mesoproterozoic xenocrystic zircons possess Proterozoic-dominant two-stage Hf model ages, further suggesting the wide existence of Proterozoic crust beneath western XAB. Cyclic Proterozoic crustal growth and reworking seem to show close linkages with the orogenesis during relevant supercontinent cycles. 1450-1360 Ma juvenile crustal growth at Erenhot and synchronous ancient crust reworking at Sonid Zuoqi and Abagaqi were likely resulted from retreating subduction involved in Columbia breakup, while 1.2-1.0 Ga reworking and 0.9-0.7 Ga growth events within the Erenhot basement might respond to assembly and breakup of Rodinia, respectively. Besides, our work confirms that reworking of Neoproterozoic crust played important roles during Paleozoic multi-stage accretion of CAOB.
文摘华南地区是我国重要的稀有金属矿产区,绝大部分具经济规模的稀有金属矿床均与高演化的富Li-F花岗岩有成因联系。大坪花岗斑岩位于南岭构造带最东缘福建省永定地区,与区内Nb-Ta矿床形成有关。该岩体SIMS和LA-ICP-MS锆石U-Pb定年结果分别为186.7±1.2Ma和190.7±1.1Ma,是华南少见的早侏罗世(200~180Ma)侵入的花岗岩侵入体,也是华南最早报道的早侏罗世稀有金属成矿事件。大坪花岗斑岩具高钾低镁、准铝质到弱过铝质的特征,属于高钾钙碱性花岗岩,并显示A型花岗岩的地球化学特征,如富硅(72.81%~76.44%)、高10000×Ga/Al比值、高FeO^T/MgO和高的Zr+Nb+Ce+Y含量、亏损高场强元素和Eu负异常明显等。全岩体系低的Zr/Hf、Nb/Ta比值,指示岩浆具有较高的分异演化程度,Nb 2 O 5和Ta 2 O 5均含量达到了花岗岩型稀有金属矿床的工业品位。花岗斑岩中锆石Hf-O同位素分析结果显示,其具有比较亏损的Hf同位素与比较均一的O同为素组成(εHf(t)=-2.4~3.4,δ^18 O=6.0‰~6.6‰)。结合微量元素地球化学特征,大坪花岗斑岩源区主要来源于软流圈地幔,并有约20%~30%壳源岩浆的加入,在成岩过程中发生了显著的分离结晶。晚期富氟的流体出熔并向上迁移可能对于Nb和Ta的再次富集与分异具有重要作用。大坪花岗斑岩与闽西南地区同时期的火山岩,如藩坑组双峰式火山岩,在空间上可与前人提出的“南岭山脉早侏罗世发育的东西向裂谷岩浆岩带(OIB型玄武岩、辉长岩和A型花岗岩组合)”相对应,是该裂谷带向东的延伸。
