研究生知识库

贵州织金磷块岩型稀土矿是具有超大型资源潜力的稀土矿，在我国是一种新类型稀土矿，是一种继离子吸附型稀土矿后的中重稀土重要后备资源。本文从岩石学、矿物学以及地球化学角度试图总结出织金磷块岩中稀土元素的富集规律以及古地理环境对稀土富集的制约，主要取得以下成果与结论：（1）岩石类型制约稀土元素富集。戈仲伍组∑REE和Y含量明显受岩石类型控制，由白云岩→含磷白云岩→白云质磷块岩→磷块岩→黑色（碳质）磷块岩，∑REE和Y含量依次增加。本质上是由岩石中胶磷矿、P2O5含量决定的。∑REE和Y含量呈很好的正相关，并且二者与岩石的P2O5含量均呈正相关，这反映出∑REE和Y含量可能与岩石中磷的化学成分和矿物成分密切相关；（2）稀土元素富集与矿物结构、生物成矿作用有关。戈仲伍组中下段主要为砂屑结构，矿物颗粒以柱状，条状为主，并分布有一定数量的生物碎屑；戈仲伍组中上段主要为粉屑结构，矿物颗粒以椭圆形、圆形粒状为主，生物碎屑含量很少。P2O5含量与稀土元素的含量在中下段比中上段相对富集。通过生物碎屑和稀土元素的分布特征以及轻、重稀土的分异特征，可以推测，在织金磷矿区摩天冲矿段，生物有利于稀土元素尤其是轻稀土的富集；（3）稀土元素富集与氧化还原环境有关。虽然U/Th与Ni/Co、δU与Th/U元素对跟V/Sc与V/Cr、V/(V+Ni)元素对对沉积环境的反映是相对的，但是通过Ce/Ce*与LaN/NdN近似呈线性的负相关关系，还是说明了轻稀土的富集可能与古海水的氧化还原条件有关，在越氧化的条件下，轻稀土越富集。（4）在平面上北西矿带（高山-戈仲伍-打麻厂）戈仲伍组∑REE和Y含量高于南东矿带（李家寨-毛稗冲）；北西矿带内部以高山-戈仲伍-打麻厂为中心，向四周∑REE和Y含量是降低的；（5）构建了织金地区早寒武世成磷期的古地理格局-缓坡模式。缓坡盆地最有利于稀土的富集，其次是缓坡滩前塌积地带，其次是缓坡滩地带，再次是缓坡盆前缘地带，缓坡盆后缘则不利于稀土的富集，缓坡盆地向东北和西南方向稀土含量降低；环境的水动力条件也制约着稀土的富集，水动力增强，相对的稀土含量减少。

The phosphate-type rare earth ore in Zhijin, Guizhou is a rare earth ore with super-large resource potential. It is a new type of rare earth ore in China, and it is an important reserve resource for medium-heavy rare earths after ion-adsorbed rare earth ore. From the perspective of petrology, mineralogy and geochemistry, this paper attempts to summarize the pattern of enrichment of rare earth elements of phosphorites and the constraints of paleogeographic environment on rare earth enrichment in Zhijin. The main results and conclusions are as follows:1. Rock type restricts the enrichment of rare earth elements. The content of REE and Y in Gezhongwu group is obviously controlled by rock type, and the content of REE and Y increased in turn in the following rock: dolomite→phosphor-bearing dolomite→dolomitic phosphorite→phosphorites→black (carbonaceous) phosphorites. Essentially determined by the phosphate rock and P2O5 content in phosphorites. The content of ∑REE and Y is positively correlated, and both of them are positively correlated with the P2O5 content of phosphorites. This indicates that the content of ∑REE and Y may be closely related to the chemical composition and mineral composition of phosphorus in phosphorites;2. The enrichment of rare earth elements is related to mineral structure and biomineralization. The middle and lower sections of the Gezhongwu Group are mainly Sandy structures. The mineral particles are mainly columnar and strip-shaped, and there are a certain amount of bioclastics. The upper and middle sections of the Gezhongwu Group are mainly powder structures, and the mineral particles are oval, round granular, and the amount of bioclastics is small. The content of P2O5 and rare earth elements are relatively enriched in the middle-lower section compared with the upper-middle section. Through the distribution characteristics of bioclastics and rare earth elements and the differentiation characteristics of light and heavy rare earths, it can be inferred that the organism is conducive to the enrichment of rare earth elements, especially light rare earths, in the phosphate-type rare earth ore of Zhijin;(3) The enrichment of rare earth elements is related to the redox environment. Although the element pairs of U/Th and Ni/Co, δU and Th/U and the element pairs of V/Sc and V/Cr, V/(V+Ni) are different about the reflection of the depositional environment, but Ce/Ce* and LaN/NdN is approximately linear negative correlated, which indicates that the enrichment of light rare earth may be related to the redox conditions of ancient seawater. Under the condition of oxidation, the light rare earth is more concentrated.(4) The REE and Y content of the Gezhongwu Group in the Northwest ore belt (Gaoshan-Gezhongwu-Damachang) on the plane is higher than that in the Southeast ore belt (Lijiazhai-Maobaicong); Seeing Gaoshan-Gezhongwu-Damachang as the center, the REE and Y content are reduced to the surrounding area;(5) The palaeogeographic pattern of the Early Cambrian phosphorus formation in Zhijin was established. The gentle slope-basin is the most conducive to the enrichment of rare earths, followed by the gentle slope-beach, than the leading edge of gentle slope-basin. The trailing edge of gentle slope-basin is not conducive to the enrichment of rare earths. The content of rare earth is reduced from the basin to the northeast and southwest; the hydrodynamic conditions of the environment also restrict the enrichment of rare earths, and the enhancement of hydrodynamics relatively reduces the content of rare earths.