| 白云鄂博稀土矿床形成年龄的新数据 |
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| 引用本文：张宗清,唐索寒,王进辉,袁忠信,白鸽.1994.白云鄂博稀土矿床形成年龄的新数据[J].地球学报,15(1,2):85-94. |
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| 中文摘要:白云鄂博铁铌稀土矿床的形成年龄是一个争论的问题。采自该矿床主、东矿的13个稀土矿石样品和5个明显为后期形成的脉体矿物样品被进行Sm-Nd同位素分析。对矿区北部侵入地层中的碳酸岩脉也做了工作。由矿石样品得出的Sm-Nd等时年龄为1 286±91(2σ) Ma，I_Nd=0.51098±4(2σ)，ε_Nd(t)=-0.06±0.78。脉体矿物样品给出的等时年龄为422±18(2σ)Ma，I_Nd=0.511263±13(2σ)，ε_Nd(t)=-16.3±0.2。采自矿区北部碳酸岩的等时年龄为1223±65 |
| 中文关键词:Sm－Nd，成矿年龄，白云鄂博 |
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| NEW DATA FOR ORE-FORMING AGE OF THE BAYAN OBO REE ORE DEPOSIT,INNER MONGOLIA |
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| Abstract: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. |
| keywords:Sm-Nd isotope ore-forming age Bayan Obo |
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