| 白云鄂博稀土矿床形成年龄的新数据 |
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| 关键词:Sm-Nd isotope ore-forming age Bayan Obo |
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| NEW DATA FOR ORE-FORMING AGE OF THE BAYAN OBO REE ORE DEPOSIT,INNER MONGOLIA |
| The Bayan Obo Fe-Nb-REE deposit,Inner Mongolia,China is the largest REE deposit in the world.Many research works on this deposit have been made and vast amount of scientific data have been accumulated.However,the genesis, especially the ore-forming age and REE sources, have been under dispute for a long time.21 samples were collected to determine the Sm-Nd isotopic compositions,of which 13 whole-ore samples from the Main ore body and the East ore body,3 whole-rock samples from the carbonatitic vein that cuts the quartzcoe strata in the north part of the mine region and 5 mineral samples from the late vein in the ore bodies. Three Sm-Nd isochrons were obtained on the basis of the isotopic analytical results. The whole-ore samples of the ores present a Sm-Nd isochron age of 1 286±91(2σ) Ma.With I_Nd=0.51098±4(2σ),ε_Nd(t)=-0.06±0.78,model age t_DM=1671±61(σ)Ma. The carbonatitic vein samples give an isochron age of 1223±65(2σ)Ma,with I_Nd=0.51093±35(2σ),ε_Nd(t)=-2.63±0.68,and it is in good agreement with a reported ￣(40) Ar/￣(39) Ar age of 1260Ma for riebeckite in the fenite vein that cuts quartzose strata,The Sm-Nd isotopic analytical results for the 5 mineral samples yield an isochron age of 422±18(2σ)Ma,with I_Nd=0.511263±13(2σ),corresponding to ε_Nd(t)=-16.3±0.2. The values of ε_Nd(t)indicate that the REE or ore-forming materials in the deposit have most prob-ably been derived from the mantle and the age data suggest that the ore-forming process chiefly took place in the Middly Proterozoic, the age of 422Ma indicates alteration or metamorphism of the ore in the Calednian time. |
| ZHANG Zong-qing,TANG Suo-han,WANG Jin-hui,YUAN Zhong-xin,BAI Ge.1994.NEW DATA FOR ORE-FORMING AGE OF THE BAYAN OBO REE ORE DEPOSIT,INNER MONGOLIA[J].Acta Geoscientica Sinica,15(1,2):85-94. |
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