福建李坊重晶石矿床形成环境及矿床成因

Formation Environment and Genesis of the Lifang Barite Deposit in Fujian Province

为了解福建李坊重晶石矿床成因和成矿物质来源,对重晶石单矿物的主量元素、稀土元素、微量元素和硫同位素进行了研究,研究结果显示:重晶石单矿物表现出富Al、Si、Fe的特征;ΣREE总量较低,富集轻稀土元素;δEu呈正异常,δCe呈负异常;微量元素富集Ba、Rb、Nb、Th、P等元素,亏损K、Zr等元素;各个中段δ34S均值大于32.6‰,且直方图中只显示一个主峰。重晶石单矿物成因判别图解、ΣREE-La/Yb图解,分别指示了重晶石单矿物形成于热水沉积区,成矿物质来源于沉积岩区;Si O2/Al2O3、MnO/TFe2O3、U/Th等比值指示了弱碱性—碱性的氧化环境;(La/Ce)N、Al/(Al+Fe)等比值指示大陆边缘环境。研究表明,李坊重晶石矿床形成于大陆边缘构造环境的热水沉积成矿作用,其Ba主要来源于沉积岩区,S主要来源于寒武纪海水,并且有较多陆源物质的输入。

For the purpose of understanding the genesis of the Lifang barite deposit in Fujian Province and the source of its metallogenic materials,this thesis has conducted a study on the main elements,rare earth elements,trace elements and sulfur isotope of the barite single mineral in the deposit.The results indicate that the barite single mineral is characterized by rich Al2O3,SiO2and TFe2O3,relatively lowΣREE with rich LREE,a positiveδEu anomaly and a negativeδCe anomaly,and rich Ba,Rb,Nb,Th,P and deficient K and Zr.The average of all midpieceδ34S is greater than 32.6‰,and only one main peak is displayed in the histogram.The genetic diagram of the barite single mineral,ΣREE-La/Yb respectively indicate barite single mineral form from hydrothermal sedimentation and sedimentary rocks contributing to most of its barium content.The ratios of Si O2/Al2O3,MnO/TFe2O3,U/Th,etc.indicate alkalescent-alkaline oxidizing environment.The ratios of(La/Ce)N,Al/(Al+Fe),etc.indicate continental margin environment.This thesis concludes that the Lifang barite deposit was formed by hydrothermal sedimentation in a continental margin environment with sedimentary rocks contributing to most of its barium content and Cambrian seawater being the major source of sulfur;this formation process is accompanied by a relatively large terrigenous input.