白云鄂博矿床白云岩的Sm-Nd、Rb-Sr同位素体系  

The Sm-Nd and Rb-Sr isotopic systems of the dolomites in the Bayan Obo ore deposit, Inner Mongolia, China.

作　　者：张宗清[1] 唐索寒[1] 王进辉[1] 袁忠信[2] 白鸽[2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《岩石学报》2001年第4期637-642,共6页Acta Petrologica Sinica

基　　金：国家地调项目(项目编号;DKD2001020-2)资助.

摘　　要：白云鄂博矿床的年龄和成因长期争论。本文报道了白云鄂博矿床白云岩及其组成矿物的Sm-Nd、Rb-Sr同位素分析结果。采自该矿床主、东矿等地的15个白云岩样品的Sm-Nd同位素分析结果呈现一条等时线,等时年龄1273±100(2σ)Ma,INd=0.510919±36(2σ),MSWD1.01。全岩Rb-Sr同位素分析结果分散,不构成等时线。87Rb/86Sr 0～2.092×10-2,87Sr/86Sr 0.70341～0.70541。白云岩矿物的Sm-Nd同位素分析结果给予了与全岩类似的Sm-Nd等时年龄,t=1250±210(2σ)Ma,INd=0.510914±77(2σ),MSWD 0.56。白云鄂博矿床可能是中元古代末期大离子亲石微量元素略为富集地幔源区部分熔融岩浆活动产物。The Bayan Obo Fe-Nb-REE ore deposit, Inner Mongonia, 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. its genesis, especially the ore-forming age and REE sources, have been under dispute for a long time. This paper reports the Sm-Nd and Rb-Sr isotopic analytical results of the dolomites for one of the major REE ore types and their minerals in the Bayan Obo deposit. The Sm-Nd isotopic analytical results of the 15 dolomite whole rock samples from the Main ore body and the East ore body in the deposit present an isochron of t= 1273±100(2σ)Ma, corresponding to INd = 0. 510909±36(2σ) ,MSWD 1. 01,but their Rb-Sr isotopic analytical data, with the ranges of 0-2. 092×10-2 for 87Rb/86Sr ratios and of 0. 70341-0. 70541 for 87Sr/86Sr ratios, are quite scattered. The Sm-Nd isotopic analytical results for the mineral samples of the dolomite give an analogous isochron age of t = 1250±210 (2σ) Ma, with INd = 0. 510914±77 (2σ) , MSWD0. 56, to the whole rock samples. The obtained Sm-Nd ages of the dolomite whole rock and their mineral samples are in agreement with the reported age data of the other samples from this deposit. For example, the Sm-Nd age of the whole ore samples from the Main ore body and East ore body of this deposit is 1286±91Ma, the ones of the potassium-rich slates and dark slates in the overlying H9 formation of the main ore body are 1096±56Ma and 1208±123Ma respectively, the one of the monazite and bastnaesite mineral samples, sorted from the Main ore body, is 1313±41Ma, and their corresponding εNd(t) are all negative values in range of -0. 06-4. 4. Besides, the 40Ar/39Ar age of 1260Ma, 1209±12Ma and the Sm-Nd age of 1223±65Ma for the alkali amphibole and the whole rock samples of carbonatite dykes, being similar geochemical feature to the deposit in the Dulahala area of the north of the Main ore body have been measured. This data state clearly indicates that the Bayan Obo deposit

关 键 词：同位素地质年代学 白云岩 白云鄂博矿床 钐-钕同位素 铷-锶同位素 中元古代 

分 类 号：P619.234[天文地球—矿床学] P597.3[天文地球—地质学]