白云鄂博陆缘裂谷系沉积物源与超大型稀土矿床含矿白云岩的成因探讨  

Sediment Source of Bayan Obo Marginal Rift and Genesis of Ore-Bearing Dolomite of the Giant REE Deposit

作　　者：杨奎锋[1] 范宏瑞[1] 胡芳芳[1] 王凯怡[1] 

机构地区：[1]中国科学院地质与地球物理研究所,矿产资源研究重点实验室,北京100029

出　　处：《地质学报》2012年第5期775-784,共10页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40902028)资助的成果

摘　　要：白云鄂博群尖山组H4岩性段石英砂岩中的碎屑锆石年龄纪录了华北克拉通北缘两期重要的构造岩浆事件,一组年龄集中在新太古代—古元古代初期(2379～2596Ma),另一组年龄集中在古元古代晚期(1761～1946Ma),该结果与白云鄂博地区基底岩石的锆石年龄相吻合。白云鄂博群沉积碳酸盐岩的全岩207Pb-206Pb等时线年龄1649±45Ma,代表了白云鄂博群的沉积时代。白云鄂博地区沉积灰岩、白云岩与含矿白云岩的Pb同位素组成存在非常大的差异,在Pb同位素组成和构造图解中,含矿白云岩都集中在地幔演化线附近,靠近亏损地幔端元[(206Pb/204Pb)i=15.04～16.49,(207Pb/204Pb)i=15.17～15.28,(208Pb/204Pb)i=31.20～36.40],而白云鄂博群中的灰岩、白云岩则位于造山带演化线附近,靠近深海沉积物端元[(206Pb/204Pb)i=17.28～19.35,(207Pb/204Pb)i=15.47～15.69,(208Pb/204Pb)i=36.62～37.12]。Detrital zircon ages of Jianshan Formation H4 quartz sandstone of Bayan Obo Group record two major tectonic-magmatic events in the northern margin of the North China Craton（NCC）.One Group of age concentrates in the Late Archean—Early Paleoproterozoic（2379~2596 Ma）,and the other in the medium Paleoproterozoic（1761~1946 Ma）.The results are consistent with the zircon ages of basement rocks in the Bayan Obo region.The 207Pb-206Pb isochron age（1649±45 Ma） of the sedimentary carbonate rocks of the Bayan Obo Group may represent its deposition times.The Pb isotope compositions of ore-bearing dolomite marble are quite different from those of the sedimentary carbonate rocks of the Bayan Obo Group.In the Pb isotope composition and tectonic diagram,the ore-bearing dolomite marbles are concentrated near the mantle evolution line and close to depleted mantle end member ／[（206Pb/204Pb）i=15.04~16.49,（207Pb/204Pb）i=15.17~15.28,（208Pb/204Pb）i=31.20~36.40 ／],but the sedimentary carbonate rocks are distributed near the orogenic evolution line and close to the pelagic sediment end member ／[（206Pb/204Pb）i=17.28~19.35,（207Pb/204Pb）i=15.47~15.69,（208Pb/204Pb）i=36.62~37.12 ／].

关 键 词：白云鄂博群 碎屑锆石 含矿白云岩 PB同位素 U-Pb年龄 

分 类 号：P618.7[天文地球—矿床学] P619.234[天文地球—地质学]