摘要
稀有稀散稀土元素(三稀元素)因性能和作用特殊,是重要的战略资源,同时因其特有的地球化学属性,在研究古气候、古水体和古沉积环境、沉积物源等方面具有重要的意义。前人针对宁东煤田研究发现,煤系伴生稀散元素Ga轻度富集,而稀土元素含量偏低。本次研究选取灵武、积家井两个典型矿区,在钻孔岩心中开展系统采样,采用电感耦合等离子体质谱法(ICP-MS)对延安组泥岩、砂岩以及煤层顶(底)板开展三稀元素含量测试,探讨煤系三稀元素富集成矿可能性,同时讨论延安组古沉积环境特征及物源区岩石性质。结果表明:宁东煤田中侏罗统延安组煤系三稀元素整体含量水平较低(仅有Ga元素最高含量29.40μg/g,接近于30.00μg/g的最低工业品位)。稀有、稀散元素在延安组底部或细-粉砂岩、泥岩中的含量较高,与世界煤中的平均含量相比,稀有元素Li、Nb、Ta、Rb、Cs、Zr和稀散元素Ga、In、Sc、Hf为轻度富集或富集;REY(稀土元素+Y元素)属于LREY富集型,Eu呈明显的负异常。通过典型元素地球化学参数研究延安组古沉积环境,Rb、Sr和REY指示古气候条件温湿,Li、Sr、Ga指示为淡水沉积环境,Ce、Ce/La反映缺氧的还原环境;REY含量未受成岩作用影响,可以用于对原始沉积岩物源的判别。
BACKGROUND:Rare,dispersed,and rare earth elements are important strategic resources because of their special performance and function.At the same time,because of its unique geochemical properties,it is of great significance in the study of paleoclimate,paleo-water and paleo-sedimentary environment,and sediment sources.Previous studies have found that Ga in the Ningdong Coalfield is slightly enriched and rare earth element content is low.OBJECTIVES:To explore the possibility of enrichment and mineralization of rare,dispersed,and rare earth elements in the coal series of the Yan’an Formation of Middle Jurassic in the Ningdong Coalfield,and discuss the characteristics of paleosedimentary environment and properties of provenance rock.METHODS:Systematic sampling was carried out in the core of boreholes from the Lingwu and Jijiajing mining areas of the Ningdong Coalfield.ICP-MS was used to determine the content of rare,dispersed,and rare earth elements in mudstone,sandstone and top(bottom)plate of the Yan’an Formation.RESULTS:The overall content of rare,dispersed,and rare earth elements in the Yan’an Formation of the Ningdong Coalfield is low,which do not meet the requirements of the industrial indicators of the deposit and cannot be exploited comprehensively.The highest content of Ga is 29.40μg/g,which is close to the lowest industrial grade of 30.00μg/g.Compared with the average content of elements in world coal,rare elements Li,Nb,Ta,Rb,Cs,Zr and dispersed elements Ga,In,Sc,Hf are slightly enriched or enriched.The distribution of rare earth elements shows LREY type,and significant negative anomaly of Eu.CONCLUSIONS:Rb,Sr and REY indicate the humidity of paleoclimate conditions,Li,Sr and Ga represent the freshwater deposition environment,and Ce,Ce/La reflect the anoxic reducing environment.The REY content is not affected by diagenesis and can be used to discriminate the original sediment source.
作者
何伟
吴亮
魏向成
陶瑞
宋扬
HE Wei;WU Liang;WEI Xiangcheng;TAO Rui;SONG Yang(Ningxia Mineral Geological Survey Institute,Yinchuan 750021,China;Ningxia Mineral Geology Research Institute,Yinchuan 750021,China)
出处
《岩矿测试》
CAS
CSCD
北大核心
2022年第6期962-977,共16页
Rock and Mineral Analysis
基金
宁夏重点研发计划重大(重点)项目(2020BFG02003,2022BEG02013)。
关键词
稀有稀散稀土元素
电感耦合等离子体质谱法
延安组
地球化学特征
古沉积环境
物源
rare
dispersed and rare earth elements
inductively coupled plasma-mass spectrometry
Yan’an Formation
geochemical characteristics
paleosedimentary environment
provenance
