【作者】 袁伟；

【导师】 庄新国；

【作者基本信息】 中国地质大学 ， 矿产普查与勘探， 2023， 博士

【摘要】 论文综合运用煤地质学、煤岩煤化学、煤的矿物学及地球化学等理论与方法,使用光学显微镜、X射线衍射分析仪、带能谱的扫描电镜、X射线荧光光谱仪以及电感耦合等离子体质谱仪等分析测试技术,对准格尔煤田中深部区石炭-二叠纪含煤岩系铝-镓-锂共富集特征及地质控制因素开展了系统研究,基本查明主要可采煤层中铝、镓和锂等关键金属异常富集的时空分布规律及赋存状态;初步阐明煤系铝-镓-锂共富集过程与富集机制;对准格尔煤田铝、镓和锂等多金属成矿的含矿品位、靶区预测与资源潜力进行了综合评价。取得的主要认识如下:准格尔煤田中深部区含煤岩系属于华北石炭-二叠纪含煤沉积盆地一部分,含煤地层为晚石炭世太原组和早二叠世山西组,主要可采煤层分布于太原组。太原组形成于海陆过渡环境,主要沉积了一套以细碎屑为主的潮坪相沉积;山西组形成于海陆过渡和陆相环境,主要沉积了一套以粗碎屑为主的三角洲和河流相沉积。主要可采煤层的显微组分组成以镜质组和惰质组为主,含少量壳质组。煤层整体以低水分含量、中-中高灰分产率、中高挥发分产率和低的固定碳产率为特征。煤中矿物以高岭石为主,其次为碳酸盐和勃姆石,含少量石英、硫磷铝锶石、黄铁矿。煤层夹矸中矿物主要为高岭石,含少量的石英、伊利石、勃姆石、方解石、黄铁矿、石膏。煤层中矿物的含量分布具有明显的时空不均匀性。横向上,煤中高岭石、黄铁矿和菱铁矿含量由北向南具有增高趋势,而勃姆石、硫磷铝锶石和石英含量具有降低趋势。垂向上,煤层中不同矿物含量的分布是不均匀的,但整体上夹矸和顶底板中的高岭石含量明显高于煤中,勃姆石和硫磷铝锶石主要分布在6号煤层,其次分布于9号煤层。煤中高岭石主要为自生和碎屑成因,而勃姆石和硫磷铝锶石主要为自生成因。与中国煤中常量元素平均值相比,研究区煤中具有较高的Al₂O₃和Si O₂含量。与世界煤中微量元素均值相比,各煤层中整体富集Li、Ga、Sr、Zr、Nb、Th和Ta,轻度富集Ti、Se、Pb、Tl、W和REE。除ZK43-25孔5煤外,其余煤层中稀土元素含量均高于世界煤均值;且夹矸及顶底板中稀土元素含量高于煤中。煤中富集的Ga主要赋存于高岭石和勃姆石中。富集的Li除赋存于高岭石、勃姆石中外,还可能赋存于硫磷铝锶石中。主要可采煤层6号和9号煤层存在有铝、镓和锂,铝和锂,铝和镓组合,以及铝,锂,镓等不同类型的异常富集。根据这些异常富集类型的分布特征,将煤中铝、镓、锂的有利勘查开发区域划分为最有利区（Ⅰ类）、高有利区（Ⅱ类）、一般有利区（Ⅲ类）和潜在有利区（Ⅳ类）。这些有利区块主要分布于研究区的北部和中部。通过资源量估算,共获得煤中Al₂O₃资源量12.5亿吨,Ga资源量14.6万吨,Li资源量136.8万吨,均具有超大型矿床规模。煤中铝、镓和锂元素的富集受控于陆源区母岩的化学风化作用程度、泥炭沼泽的沉积环境、流体活动以及成岩过程中复杂的水/岩作用过程。铝、镓、锂的异常富集经历了3个阶段:华北地台前石炭系古陆和阴山古陆中元古代钾长花岗岩的长期风化淋滤,形成富Ga-Li-REY的铝土和粘土质风化壳残积物,为研究区煤中铝、镓、锂的富集提供了物质来源。晚石炭世华北盆地的缓慢沉降,海侵作用形成广泛的海陆过渡环境,并在泥炭沼泽形成时期,潮汐作用将富铝、镓、锂的细粒或胶状粘土矿物呈悬浮状态搬运,在水动力相对较弱的泻湖、泥炭沼泽等水体沉淀。在泥炭化和成岩阶段,在酸性流体与碎屑和胶体物质的相互作用下,碎屑物质中释放并伴随流体迁移的部分锂、镓和稀土元素等再富集。更多还原

【Abstract】 Based on the theories and methods of coal geology,coal chemistry,coal mineralogy and geochemistry,and on the analysis and test techniques of optical microscopy,X-ray diffraction（XRD）,scanning electron microscope with energy dispersed spectrum（SEM-EDS）,X-ray fluorescence spectrometer（XRF）and inductively coupled plasma mass spectrometer（ICP-MS）,this thesis investigates the characteristics and geological controls of the co-enrichment of Al-Ga-Li in the Permo Carboniferous coal-bearing sequence in the middle and deep mining areas of the Jungar coalfield,and focuses on finding out the temporal and spatial distribution of Al and Ga,Li and other key metallogenic layers,revealing the coupling relationship between geological control factors and polymetallic co-enrichment,and on clarifying the co-enrichment process and mechanism of Al-Ga-Li in the coal-bearing sequence.The main findings are as follows:As a part of the Permo Carboniferouscoal-bearing basin in North China,the main coal-bearing sequence of the central deep area in the Jungarcoalfield is the late Carboniferous Taiyuan Formation and the early Permian Shanxi Formation,and the primary workable coal seams are widely distributed in the Taiyuan Formation.The Taiyuan Formation was formed in a marine-continental transitional environment,with fine detrital sediments of the tidal flat facies,while the Shanxi Formation was formed in a continental to transitional environment,with coarse sediments of the delta and fluvial facies.Vitrinite and inertinite are mainly composed of macerals from coal seams to be mined in the study area,with a small amount of chitin.The overall seam is characterized by low moisture content（4.9%on average）,medium to medium high ash yield（20.0-22.0%on average）,medium to high volatility（37.4-38.1%on average）and low fixed carbon yield（46.2-47.0%on average）.The average moisture content of No.6coal seam is slightly higher than No.9 coal seam.The average ash yield of No.6 coal seam increases from north to south,and the ash yield of No.9 coal seam increases from middle to south.Kaolinite is the main mineral in the coal,followed by carbonate and boehmite,containing a small amount of quartz,svanbergite,and pyrite.Kaolinite is the main mineral in coal gangue,which contains a small amount of quartz,illite,boehmite,calcite,pyrite and gypsum.The distribution of mineral content in coal seams has obvious spatiotemporal inhomogeneity.Horizontally,the content of kaolinite,pyrite and siderite increased from north to south,while the content of bohmite,svanbergite,and quartz decreased.The content of kaolinite in gangue and roof and floor is higher than that in coal.Boehmite and svanbergite,are mainly distributed in No.6 coal seam,and secondly in No.9 coal seam.Kaolinite in coal is mainly of autogenetic and clastic origin,while boehmite and svanbergite are mainly formed by weathering alteration of weathering crust of Benxi bauxite.The content of Al₂O₃and Si O₂in the coal in the study area is higher than the average values in common Chinese coal.When compared with the average in worldwide coals,Li,Ga,Sr,Zr,Nb,Th and Ta are enriched,and Ti,Se,Pb,Tl,W and REY are slightly enriched in all coal seams in the study area.Except for in the No.5coal from ZK43-25 borehole,the concentration of rare earth elements and Y（REY）in other coal seams is higher than the world average,and the concentration of REY in parting,roof and floor is higher than that in coal.The No.6 and No.9 coal seams in the study area are characterized by the co-enrichment of Al,Ga and Li.According to the distribution characteristics of different co-enrichment types,four types of favorable exploration and development areas,viz the most favorable exploration and development area（type I）,the highly favorable exploration and development area（typeⅡ）,the common favorable exploration and development area（typeⅢ）,and the potential favorable exploration and development area（typeⅣ）are classified in the studied area.The estimated total amount of Al₂O₃,Ga and Li resources obtained from themain workable coal seams（No.6 and No.9）in the study area is 1.25 billion tons,146 thousand tons,and1.37 millon tons,respectively,allreaching the scale of extra-large mineral deposits.The enrichment of Al,Ga and Li in coal-bearing sequence is controlled by terrigenous detrital supply,redox conditions,fluid activity and complicated water/rock processes.Due to strong chemical alteration,the weathering and denudation of the Mesoproterozoic K-feldspar granite in the Yinshan Oldland provide a basic source for the enrichment of Al,Ga and Li in coal-bearing sequence.The terrigenous detritus containing Al,Ga and Li enriched in the weathering crust of the Upper Carboniferous Benxi Formation,which is located in the NE of the basin.Under the complex reaction of organic acid,carbonate and persistent strong weathering and leaching process,the relatively inactive elements such as Al,Ga,Li and REY in the weathering crust accumulate in situ and retain to form Al-Ga-Li-rich bauxite.In addition,the differential tectonic subsidence between the margin and the inner part of the basin makes the Al-Ga-Li-rich bauxite of the Benxi Formation as a direct material source of Al,Ga and Li in the coal-bearing sequence of the Jungar coalfield,which migrated to the coal-bearing sequence in the form of fine detritus or colloidal solution.Lithium,gallium and rare earth elements were released from the detrital material,and further migrated and redistributed by the interaction of acidic fluid and clastic colloid material.Lithium,gallium and rare earth elements were finally enriched and occurred in boehmite,and/or kaolinite and other minerals in the studied coal-bearing sequence.更多还原