研究生知识库

The Xinhua phosphorite-hoste rare earth element deposit in Guizhou province,the second largest rare earth element deposit in China after Bayan Obo, is a giant rare earth element deposit. This rare earth element deposit occurs in the Gezhongwu Formation, and locates on the southwest of the north Guizhou Uplift in Upper Yantze Platform. The type of the deposit belongs to the phosphorite-type REE deposit.Previous studies on the Xinhua deposit focus on the phosphate, and most of workare related with the mineralization regularity, ore formation mechanism, and metallogenic prediction for phosphate, but few work is related with the rare earth element, especially the enrichment regulation, ore-forming processes, and ore-controlling factors . In this study, we colligated the previous study, and conducted field investigation and experiment research, and most of our work focus on the occurrence, enrichment regulation, ore-controlling factors of rare earth element. Our results are as following:a. It shows that the REY mainly occur in apatite by EPMA, SEM and correlation analyses; LA-ICPMS analysis indicates the REY concentrations in dolomite (∑REY =10ppm) are lower than in apatites (∑REY is from 500 to 1000ppm). XRF and EPMA analyses suggest the apatite type is fluorapatite.b. the rare earth elements were sourced from the hot water by the result of major elements (Fe/Ti、(Fe+Mn)/Ti、Al/(Al+Fe+Mn)) from whole rocks, enrichment of specific elements (Sb、Ag、As、Pb、U、Ni、Ba) in hot water sediments, Zr-Cr, U-Th, and Fe-Mn-(Ni+Cu+Co)*10 diagrams, Eu anomalies of whole rocks and apatites, and the REE concentrations. In addition, according to the geological characteristics of the study area, we suggest that deep sea sediments with hot water characteristics may be the source of ore-forming materials. By chondrite-normalized REE patternsindicate that ore-forming materials consist of deep sea sediments andhot water sedimentary.c. Based on REY patterns , clustering analysis of sample elements in high or/and low REY concentrations group, major elements combinations(Al2O3, Ca, TFe2O3, SiO2) of samples of high REY concentrations in factor analysis, significant correlations between LaN/SmN and Ce anomalies, Ce anomalies and DyN/SmN, and Ce and Eu anomalies, we suggest that post-ore modification facilitated the enrichment of REY.d. In study area, mineralization system consists of ore-forming materials sources, materials migration, materials deposition, post-ore modification and re-concentration, which is presented by deep sea sediments, ascending currents, paleo-karst-Gezhongwu Formation-apatite and faults, respectively. Therefore, ore-controlling factors of the Xinhua rare earth element deposits include the hot-water sedimentation, paleo-karst, strata, apitite, and faults. 

贵州新华磷块岩型稀土矿具超大型稀土矿床规模，保有储量全国排位第二，仅次于白云鄂博，是目前我国资源量大，保有相对完整的稀土矿。稀土元素产于下寒武系戈仲伍组，处于上扬子地块黔北隆起区织金穹盆构造变形区西南部，矿床类型属于沉积相关的磷块岩型稀土矿。新华矿床的研究成果主要集中于磷矿方面，对其成矿规律、形成机制及成矿预测等方面都进行了深入细致的研究，但对其中稀土元素的研究程度非常薄弱，在稀土元素的富集规律、成矿过程、控矿因素等方面，仍认识不清。本文在大量收集和总结前人资料的基础上，通过野外地质调查，实验分析测试，数据综合处理，对贵州新华磷块岩型稀土矿的地球化学特征、赋存状态、富集规律、控矿因素等方面进行了研究，获得的主要成果和结论如下：1、经电子探针分析、扫描电镜分析、相关性分析，认为稀土元素主要赋存于磷灰石中。激光剥蚀等离子质谱分析表明白云石中∑REY在10ppm左右，磷灰石的∑REY相对较高，在500~1000ppm之间，为稀土元素赋存于磷灰石中提供了直接的证据。同时通过X射线粉晶衍射实验、电子探针微区定量分析，认为磷灰石为氟磷灰石。2、经过全岩常量Fe/Ti、(Fe+Mn)/Ti、Al/(Al+Fe+Mn)投图，富集Sb、Ag、As、Pb、U、Ni、Ba等热水沉积的标志性元素，Zr-Cr图解、U-Th关系图、Fe-Mn-(Ni+Cu+Co)*10三角图，全岩δEu值、磷灰石δEu，∑REY含量，推断稀土元素具有热水来源。根据研究区地质特征，判断可能为具热水特征的深海物质团，而磷灰石中稀土元素球粒陨石配分曲线特征，表明富稀土元素的深海物质团由深海水沉积和热水沉积组成。3、从全岩和磷灰石稀土元素配分模式曲线的上凸特征，样品元素的聚类分析，因子分析中∑REY高含量样品的Al2O3、Ca、TFe2O3、SiO2组合，以及LaN/SmN与Ce异常、Ce异常与DyN/SmN、Ce异常与Eu异常之间良好的相关性，证明稀土元素的富集经过了改造作用。4、研究区由具热水特征的深海物质团、上升洋流、古喀斯特地貌-戈仲伍组-磷灰石，和断层，构成了稀土元素的源、运、储、改造再富集的成矿体系，因此稀土元素的控矿因素为热水沉积、古喀斯特地貌、地层、磷灰石、断层。