煤系中的锂矿产:赋存分布、成矿与资源潜力

Lithium resources in coal-bearing strata:Occurrence,mineralization,and resource potential

锂作为一种重要的战略性金属矿产,成为近些年来矿产资源勘探领域的热点。锂矿床的类型主要包括卤水型、花岗伟晶岩型和黏土型等。煤和含煤岩系中的战略性金属矿产研究取得了较多的进展,典型的有锗、镓-铝、铀、稀土、铌-锆等煤系共伴生金属矿产类型。煤中锂在过去相当长的时间内未被当作可从煤中开发利用的金属,仅在2008年后才得到较多关注和研究。煤中锂含量超过一定品位时,可形成与煤共伴生的锂矿床,属于沉积型锂矿床,但由于锂的原子序数低、赋存状态多样,是煤中赋存状态研究难度较大的元素之一。基于前人的研究,并结合煤系金属矿床特点,提出煤系中共伴生锂矿床的边界品位为Li_(2)O含量为0.08%(高温灰基)。我国煤系锂资源主要分布在华北的石炭—二叠系地层,少数分布在南方。迄今发现的品位最高的煤系锂矿床主要有山西晋城地区晚石炭世煤层、内蒙古准格尔官板乌素矿晚石炭世煤层以及重庆草堂矿晚三叠世煤层(Li_(2)O含量均大于0.2%,高温灰基),其中锂最重要的载体均为锂绿泥石或含锂的绿泥石。以上3个煤系锂矿床中Li的异常富集均为热液成因。煤系锂矿床中常还共伴生Ga和REY等战略性金属,有望实现煤系多种战略性金属矿产资源的协同开发和综合利用。

As an important strategic metal resource,lithium has been a hot spot in the exploration field in recent years.Lithium deposits occur primarily in brines,pegmatites,and clays.The research on strategic metal deposits in coal and coal-bearing sequences has also made a lot of progress in recent years.Some coal-hosted metal(such as Ge,Ga,Al,U,REE,Nb,and Zr)deposits have been found.Lithium in coal has not been regarded as an important metal for exploration and utilization for a long time in the past,and it has only received more attention since 2008.When the concentration of lithium in coal exceeds a certain grade,it can form coal-hosted lithium deposits,which are classified as sedimentary lithium deposits.In recent years,several cases of lithium enrichment in coal have been reported.However,lithium has a low atomic number,along with its low concentration in coal,and various modes of occurrence,which makes it one of the most difficult elements to be studied in coal.Based on the authors'previous research and the data published by previous researchers,it is proposed that when the Li_(2)O content in coal-bearing strata reaches 0.08%(on high-temperature ash basis),it can be considered that the grade of the coal-hosted lithium deposit in the coal-bearing strata has been reached.The coal-hosted lithium deposits discovered so far in China mainly occur in the Carboniferous-Permian strata of North China,while a small number occur in Southern China.Coals that are mostly enriched in Li(Li_(2)O in high-temperature ash≥0.2%)include the late Carboniferous coal of the Jincheng coalfield,Shanxi Province,the late carboniferous coal from the Guanbanwusu mine in the Jungar coalfield,and the late Triassic coal from the Caotang Mine,Chongqing.The most important carrier of Li in these three deposits are cookeite and/or lithium-bearing chlorite.These three coal-hosted lithium deposits are all caused by hydrothermal fluid activities.Coal-hosted lithium deposits are often associated with strategic metals such as Ga and REE,which are expected to be co-exploited and comprehensively utilized.