Occurrence And Geological Controls Of Humic Acid From Lignite In No.1 Exploration Area,Baiyinhua Coalfield

Humic acid(HA)is an important strategic resource.Lignite,weathered coal and peat are main geological carriers of HA.Based on the data of coal exploration,the geological distribution of HA in lower Cretaceous lignite in No.1 exploration area of Baiyinhua coalfield is ascertained by means of geological analysis and mathematical statistics,and the geological controls for the formation and occurrence of HA are discussed.The total humic acid yield(THAY)of lignite in the study area is lower than that of standard lignite samples in China,showing normal distribution but slightly negative bias,and tends to decrease with the decrease of horizon.There are five types of THAY distribution in the columnar section of coal seams,and the dominant types in different coal groups are various,indicating that the geological conditions of ancient peat swamps varied greatly in time and space.Regionally,the distribution pattern of THAY in each coal group and main coal seam is similar,and several high or low value centers are developed;the humic acid iso-yield zones are mostly NW-SE oriented,which may be closely related to the difference of early coalification caused by paleo-burial depth..At the same time,the THAY of lignite decreases significantly with the increase of depth,indicating that the deep humic acid yield is affected by thermal coalification.Based on the conventional coal quality data,a parameter system for HA genesis analysis including 35 parameters was established.Nutrition level index(NLI)and weathering degree index(WDI)are the new parameters established in this paper.The results show that the coal seam in this area may originate mainly from herbaceous plants,and the marsh was relatively deep covered with water.The acidic marsh might be more conducive to the formation of HA,and the over-nutrition level is not conducive to the transformation of coal-forming plants to HA.It is found that there is a systematic "contradiction" in the indicators of coal facies in the area.Therefore,the particular formation condition of primary HA in lignite is analyzed by coupling multiple evidences.It is concluded that the clay minerals in lignite were mainly co-products of volcanic ash alteration,and HA was formed in marsh with strong reducibility and acidity.This thesis contains 67 illustrations,22 tables and 97 references.