黔西北普底地区富锂黏土岩地球化学特征及成因

Geochemical characteristics and genesis of lithium rich clay rocks in the Pudi area of northwestern Guizhou

黔西北普底地区二叠系梁山组直接不整合于寒武系娄山关组之上,梁山组黏土岩中有锂的超常富集现象,研究其富集机制可为黏土岩中锂资源开发与评价提供更为丰富的信息。采用激光剥蚀电感耦合等离子质谱仪(LA-ICP-MS)分析、LA-ICP-MS面扫分析、矿物自动定量分析系统(AMICS)、X衍射和扫描电镜等手段,结合U-Pb年代学研究,对黏土岩中富集的锂开展元素地球化学、物质来源及赋存状态研究。研究结果表明:富锂黏土岩产于中二叠统梁山组中下部,锂矿化体产状受下伏基底娄山关组白云岩岩溶不整合面控制。富锂黏土岩中Li, Ga, V,Nb, Zr和F等元素相对富集,Ba和Sr等元素相对贫化。富锂黏土岩富集轻稀土元素,轻稀土元素以La、Ce和Nd为主,重稀土元素以Y为主。富锂黏土岩以淡水陆相沉积为主,具有陆相、海陆过渡相和海相多相沉积特征,沉积环境以氧化环境为主,形成于热带-亚热带温湿气候。富锂黏土岩锆石年龄谱约具有2.5 Ga、1.4 Ga、980 Ma、780 Ma和530 Ma 5个峰值,其中主要峰约为980、780和530 Ma。初步认为研究区梁山组富锂黏土岩具有多重物源,寒武系娄山关组不纯白云岩可能为主要物源,黏土岩中的Li主要赋存于高岭石中。

The Permian Liangshan Formation in the Pudi area of northwest Guizhou Province directly overlays the Cambrian Loushanguan Formation,exhibiting abnormal lithium enrichment in its clay rocks.Studying the enrichment mechanism provides valuable insights for lithium resource development and evaluation in clay rocks,as well as understanding lithium accumulation mechanisms.Various analytical methods including LA-ICP-MS,mapping,AMICS,XRD,SEM,along with U-Pb chronology,are employed to elucidate the elemental geochemistry,provenances,and occurrence states of lithium enrichment in clay rocks.Results reveal lithium-rich clay rocks primarily in the middle and lower sections of the Permian Liangshan Formation,with their occurrence controlled by the karst unconformity surface of the underlying Loushanguan Formation dolomite.Enriched elements such as Li,Ga,V,Nb,Zr,and F are identified,while Ba and Sr are relatively depleted.Light rare earth elements(La,Ce,Nd)predominate,with Y as the main heavy rare earth element.Lithium-rich clay rocks comprise terrestrial deposits with characteristics of terrestrial,transitional,and marine phases,formed in an oxidized environment under a tropical-subtropical warm and humid climate.The zircon age spectrum exhibits five peaks at 2.5 Ga,1.4 Ga,980 Ma,780 Ma,and 530 Ma,with the main peaks at 980 Ma,780 Ma,and 530 Ma.Lithium in the clay rocks mainly occurs within kaolinite,indicating multiple sources,with impure dolomite of the Cambrian Loushanguan Formation likely being the primary source.