贵州开阳地区富硒地层及风化土壤地球化学特征

通过对开阳地层和土壤调查,发现灯影组、牛蹄塘组等地层富集硒元素,由其风化而来的土壤也富硒。富硒地层同时还富集Mo、As、Cd、Sb、Ba、Co、Ni、Tl、V、Zn等元素,而相对缺Ag、Bi、Cr、Ga、Rb、Sr、Ta、Zr等元素;富硒地层风化形成的土壤中As、Ba、Cd、Co、Mo、Ni、Sb、Se、Tl等元素对基岩有明显的继承而富集;Pb元素则在基岩风化过程中流失而亏损;Cu、Sc、V、Zn元素在基岩风化后明显富集;而Ni、Co、Cd则具有对基岩的继承和后期风化富集的双重特征。研究表明该地区硒的富集是热水沉积、深部物质沿白马洞深大断裂迁移、热卤水的迁移混合,铀矿化以及大量硫化物的存在共同作用的结果。开阳富硒地层及风化土壤中稀土元素总量∑REE为66.61～609.13×10-6,LREE/HREE比值为1.17～5.40,(La/Yb)N=5.08～15.72>1,REE分布模式为右倾型,轻稀土段右倾明显,(La/Sm)N=1.43～7.44>1,为LREE富集型,重稀土段则相对平缓,(Tb/Yb)N=1.01～2.39。通过对微量、稀土元素的分析表明,富硒的黑色岩系形成于缺氧条件下的低温热水沉积环境。

Geochemical Characteristics of Selenium-rich Strata and Weathered Soil from Kaiyang County,Guizhou Province

Investigations of strata and weathered soil from Kaiyang County revealed that the Dengying and Niutitang formations and weathered soil are enriched in Se,as well as Mo,As,Se,Cd,Sb,Ba,Co,Ni,Tl,V and Zn,while Ag,Bi,Cr,Ga,Rb,Sr,Ta and Zr were depleted in weathered soil,showing diverse distribution features,specifically,Pb concentrations decreased due to weathering process,Ar,Ba,Cd,Co,Mo,Ni,Sb,Se and Tl were enriched by inheriting from the bed rocks,Cu,Sc,V,Zn were enriched in soil after weathering process.However,Ni,Co,Cd display dual characteristics of both weathering enrichment and inheriting enrichment.In combination with previous studies,it is believed that the enrichment of Se in the study area can be related to many factors,such as hydrothermal deposition,material migration along the Baimadong deep fault,mixture and migration of hot brine,uranium mineralization,existence of abundant sulfide,etc..In selenium-enriched strata and weathered soil ΣREE contents are 66.61 to 609.13×106,LREE/HREE ratios are 1.17 to 5.40,(La / Yb)N = 5.08 ～ 15.72> 1,REE distribution pattern is of right-inclined type,especially the LREE distribution pattern which,shows an obvious right-inclination.Moreover,(La / Sm)N =1.43～7.44> 1 and(Tb / Yb)N = 1.01～2.39,indicating a LREE-enrichment pattern and a relatively regular period for HREE.Study on the trace elements and REEs showed that selenium-rich black shales were formed in hydrothermal deposition environments under hypoxic conditions.