Palynological constraints on the age of the Mississippi Valley-type Changdong Pb-Zn deposit,Sanjiang belt,West China  

作　　者：Yingchao LIU Yucai SONG Zengqian HOU Dangpeng XI Suping LI Longlong YUE Wang MA Bolang TANG 

机构地区：[1]Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China [2]School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China [3]Jiangsu Nanjing Institute of Geo-Engineering Investigation,Nanjing 210041,China

出　　处：《Science China Earth Sciences》2022年第1期167-181,共15页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41922022,41773042,41773043,41772088,and 41472067);the Strategic Priority Research Program of Chinese Academy of Sciences,China(Grant No.XDA20070304);the Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources(Grant No.J1901-6);the Basic Scientific Research Foundation of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.2105);the IGCP-662 Program。

摘　　要：Mississippi Valley-type(MVT)Pb-Zn deposits serve as the world’s major supply of Pb-Zn resources.However,the age constraint of MVT Pb-Zn deposits has long been a big challenge,due to the lack of minerals that are unequivocally related to ore deposition and that can be used for radioisotopic dating.Here we show sporopollens can provide useful chronological information on the Changdong MVT Pb-Zn deposit in the Simao basin,Sanjiang belt,West China.The Pb-Zn ores in the Changdong deposit are hosted by internal sediments in paleo-karst caves of meteoric origin.Sphalerite and galena occur as replacements of carbonate minerals and void infillings in the internal sediments.The relations suggest that the Pb-Zn mineralization occurred after the deposition of the internal sediments.A palynological assemblage mainly composed of angiosperm pollen dominated by Castanea,Quercus,and Carya and fern spores dominated by Polypodiaceae,Pteris,and Athyriaceae was identified.These pollen and spores place the ore-hosting internal sediments and the Changdong paleo-karst at early to middle Oligocene.Consequently,the Changdong Pb-Zn deposit must have formed after the early Oligocene(~34 Ma).These age constraints,together with the geological characteristics,indicate that the Changdong Pb-Zn deposit is a paleo-karst-controlled MVT deposit related to fold-thrust systems in the Sanjiang belt.The Changdong deposit is similar to other MVT Pb-Zn deposits in the northern part of the Sanjiang belt,making it possible to extend this Pb-Zn belt 500 km further to the South.Results presented here highlights the potential of sporopollens in dating the age of MVT deposits related to paleo-karst formation in young orogenic belts.

关 键 词：Mississippi Valley-type(MVT)Pb-Zn deposits Age constraint PALYNOMORPHS Internal sediments Paleo-karst Changdong deposit Sanjiang fold-thrust belt 

分 类 号：P618.4[天文地球—矿床学]