内蒙古巴彦敖包地区安格尔音乌拉组地层锂土壤地球化学异常成因研究

Study on the cause of lithium soil geochemical abnormal in the layer of Angeeryinwula formation in Bayanaobao area,Inner Mongolia

内蒙古巴彦敖包地区广泛出露上泥盆统安格尔音乌拉组地层,1∶5万土壤地球化学测量工作圈定的31处锂单元素异常与安格尔音乌拉组地层分布范围吻合良好。安格尔音乌拉组地层锂元素的富集与该套地层的原生沉积作用密切相关,未发生次生富集。通过对安格尔音乌拉组地层碎屑物源区及沉积作用的研究,认为其锂元素物质来源与镁铁质火山岩中锂元素的侵蚀溶出有关。溶出的锂元素被碎屑物中的粘土矿物吸附随后沉积成岩造成区内广泛分布的锂土壤地球化学异常。进而做出推断,研究区内晚泥盆世甚至更早存在大规模中基性火山活动,应该存在大规模古火山机构。提出一种新的沉积型锂矿成矿模式,即古火山机构周边的粘土矿物含量较高的碎屑岩层位在一定构造背景及沉积环境下可以具备锂元素富集成矿的条件。

The layer of Angeeryinwula Formation is widely exposed in the Bayanaobao area,Inner Mongolia,The 31 lithium single element anomalies determined by the 1∶50,000 soil geochemical measurement work are in good agreement with the range of Angeeryinwula Formation. The enrichment of lithium of the Angeeryinwula Formation is closely related to the primary sedimentation of the layer, and there is no secondary enrichment occurs.The source of its lithium element is related to the erosion and dissolution of lithium in mafic volcanic rocks,which is proven by the Study on the source area of clastic and sedimentation in the layer of Angeeryinwula Formation. The dissolved lithium is adsorbed by clay minerals in the debris and then deposited into diagenetic rocks, and which resulted in widespread geochemical anomalies of lithium soils in the area. Then the author inferred that there was a large-scale intermediate-basic volcanic activity in the Late Devonian and even earlier in the research area, and there should be a large-scale ancient volcanic mechanism. On the basis of this research, a new sedimentary lithium-ore mineralization model is proposed, that is, the clastic rock formation with high clay mineral content around the ancient volcanic mechanism can possess the condition of lithium-rich integrated ore under certain tectonic background and sedimentary environment.