江西新余铁矿地质地球化学特征及成矿机制探讨

Geologic,Geochemistry Characteristics and Ore-Forming Mechanism of Xinyu Iron Deposit,Jiangxi Province

在野外地质调查及大量前人研究成果综合分析的基础上,对江西新余铁矿地质及矿床的主量、微量、稀土元素特征进行了系统的研究,并据此探讨了其成矿机制。研究表明,新余铁矿区的褶皱变形应该是岩石复合流变及变形机制转换作用的结果,变形温度约在310-330℃,矿体多受花岗岩体破坏或吞噬并发生强烈的风化剥蚀,钻孔揭示矿体延伸形态复杂多变,具有中深部成矿潜力,但有减薄的趋势;在沉积建造的过程中存在较多碎屑物质的加入,矿石具有Co、Sc、V富集,Rb、U、Mo亏损,ΣREE相对较高,矿石及围岩均具有显著的轻稀土相对亏损和重稀土相对富集的特征,含铁岩段具有明显Eu的负异常及Y的正异常,而Ce负异常的缺乏很可能与沉积成矿时处于氧逸度很低的环境有关;成矿大致经历了沉积成矿、变质变形及改造保存3个期次,其中与找矿关系最为密切的为第3期次。

On the basis of the field geological investigation and a lot of previous research results,a systematic analysis has been carried out the geologic features as well as the characteristics of major elements,trace elements and REE of Xinyu iron deposit in Jiangxi Province,then the metallogenic mechanism was investigated. It is shown that the fold deformations is a result of composite rock rheological effects and the transformation of deformation mechanisms,deformation temperature is 310 ℃to 330 ℃. Most of the ore bodies are destroyed or swallowed by granitic bodies,and also strongly weathered and denudated. According to multiple drilling,the most potential mineralization of Xinyu ore field may be medium-deep seated for the complicated and changing shape of ore bodies extending,but has a tendency to thinning. There are relatively more detrital materials to join the process of sedimentary formation,the total REE content in iron ore is relatively high with positive Co,Sc,V and negative Rb,U,Mo. The obvious deficit of light rare earth and the relative enrichment of heavy one happen to be in the iron ore and the wall rock,while the ferruginous rock section have distinctly negative Eu and positive Y,but the lack of negative Ce is likely to related to the sedimentary mineralization is in very low oxygen fugacity environment. The formation of iron ore deposit normally goes through three metallogenic stages： sedimentation-mineralization,metamorphism-deformation and reformation-preservation,Which the third phase is the closest relationship with the prospecting.