Dating of monazite-apatite-allanite-epidote corona from the Bayan Obo Group in the northern margin of the North China Craton:implications for the time of regional Au and REE mineralization  

华北克拉通北缘白云鄂博群REE、Au成矿时代厘定:来自于独居石-磷灰石-褐帘石-绿帘石冠状矿物组合的年代学证据

作　　者：Haidong Zhang Mingguo Zhai Dequan Wang Mostafa Fayek Jianchao Liu 张海东;翟明国;王得权;Mostafa Fayek;刘建朝(School of Earth Science and Resource,Chang’an University,Xi’an 710056,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Sino Shaanxi Nuclear Industry Group,Xi’an 710100,China;Department of Geological Sciences,University of Manitoba,Manitoba R3T2N2,Canada)

机构地区：[1]School of Earth Science and Resource,Chang’an University,Xi’an 710056,China [2]Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [3]Sino Shaanxi Nuclear Industry Group,Xi’an 710100,China [4]Department of Geological Sciences,University of Manitoba,Manitoba R3T2N2,Canada

出　　处：《Science Bulletin》2022年第3期236-239,共4页科学通报（英文版）

基　　金：supported by the National Natural Science Foundation of China(41402042,41002064,and 42172090);the Natural Sciences and Engineering Research Council of Canada(NSERC)Discovery Grant。

摘　　要：The Mesoproterozoic Bayan Obo Group located along the northern margin of the North China Craton(NMNCC)hosts a world’s largest known rare-earth element(REE)deposit(Bayan Obo Fe-REE-Nb deposit)[1,2]and a number of large gold deposits(eg.,Haoyaoerhugong and Zhulazhaga gold deposits;Fig.1a)[3],and has a long and protracted thermal history spanning from1.3 Ga to 250 Ma[1].The tectonic history was associated with Proterozoic rifting with carbonatite magmatism at1.3 Ga[4]and subsequent subduction-accretion processes of the Paleo-Asian Ocean[5,6].The Paleo-Asian oceanic subduction beneath the North China Craton(NCC)initiated in the Middle Silurian[7,8]and the ocean was closed in the Permian to induce the accretion of arcs and terranes with the NCC[2].This long and protracted tectonic history increases the difficulties both in dating and understanding the genesis of the Bayan Obo REE deposit and black shale-hosted gold deposits(e.g.,Haoyaoerhudong deposit).Thus,it is important to understand the thermal history of the hosting strata in order to constrain the tectonic drive and timing of polymetallic mineraliza-tion.There have been few attempts to date the multistage thermal events which the Bayan Obo Group has witnessed,predominantly because of greenschist facies overprint of the host rocks and lack of reliable geochronometers[9,10].华北克拉通北缘中元古代白云鄂博群拥有世界最大的REE矿床(白云鄂博Fe-REE-Nb矿床)和一大批重型-大型金矿床(浩尧尔忽洞),先后经历了1.3 Ga~250 Ma构造-岩浆事件.然而关于REE和Au的成矿时代却一直存在较大争议,其主要原因是:(1)稀土矿床中有效测年矿物同位素组成发生了重组,缺乏与晚期脉状成矿作用(450~400 Ma)相关的岩浆活动;(2)金矿中缺乏有效的测年矿物.本工作在白云鄂博群内发现了独居石-磷灰石-褐帘石-绿帘石特殊的冠状矿物组合,其为揭示白云鄂博群所经历的流体改造温度和时代提供了关键标本.精确U-Th-Pb年代学显示:白云鄂博群最早经历的热事件发生在约410~380 Ma,与白云鄂博REE矿床中晚期脉状REE成矿作用年龄一致,认为其可能与区域变质作用有关,而不是之前认为与二叠纪岩浆活动有关;浩尧尔忽洞金矿床中出现在变质峰期的含金黄铁矿脉成矿时代约为360 Ma,略早于形成在后变质峰期的含金石英-黄铁矿脉的成矿时代(341 Ma),为造山型金矿床.

关 键 词：白云鄂博群 矿物组合 区域变质作用 褐帘石 成矿时代 同位素组成 中元古代 绿帘石 

分 类 号：P612[天文地球—矿床学]