Genesis of Kaolinite Deposits in the Jungar Coalfield,North China:Petrological,Mineralogical and Geochemical Evidence  

作　　者：LIU Linsong ZHANG Tongjun LIU Jianping LIU Qinfu LI Kuo LIU Di LIU Wanyue 

机构地区：[1]College of Geoscience and Surveying Engineering,China University of Mining and Technology,Beijing 100083,China [2]Shanxi Province Coal Geology 115 Prospecting Institute,Datong,Shanxi 037000,China

出　　处：《Acta Geologica Sinica(English Edition)》2021年第2期517-530,共14页地质学报（英文版）

基　　金：supported financially by the Science and Technology Major Projects of Shanxi Province of China(grant No.20181101003);the National Key R&D Program of China(grant No.2019YFC1904903)。

摘　　要：Petrological,mineralogical and geochemical studies carried out on kaolinite deposits in Haerwusu surface mine,Jungar Coalfield,northern Ordos Basin,North China,define their characteristics,ore genesis and economic interest.Based on the crystalline size,two different types of kaolinite rocks,cryptocrystalline and grainy,were identified under the microscope.XRD data show that kaolinite is the predominant mineral,associated with boehmite,magnesite,anatase,pyrite,diaspore and calcite.However,high boehmite content(mean 70%)shows up in the middle layers.Kaolinite minerals present homogeneous shape and a good crystallinity(HI=0.96–1.26).Geochemical studies show that the SiO_(2)/Al_(2)O_(3)molar ratio of kaolinite is close to the theoretical value,and the contents of Na_(2)O,K_(2)O,CaO,Mg O are less,suggesting a strong chemical weathering environment.The REE and Eu anomalies show a close relationship between kaolinite and the Yinshan Oldland granite.A Ce anomaly reflects a continental sedimentary environment with shallow water.A temperature range of 26.7–34℃was calculated on the basis of the isotopic signatures(δ18O,δD)of the kaolinite rocks.All these data indicate that the formation of the kaolinite is caused mainly by the dissolution,coagulation,precipitation and recrystallization of aluminosilicate clastics in acidic conditions.The formation of boehmite in the middle layers indicates that the source rocks have changed.Boehmite is mainly formed by dehydration and compaction of an aluminum-rich colloid which transported into peat swamp during diagenesis.In addition,it formed by desiliconization of kaolinite under acidic conditions.Due to its high kaolinite content(up to 90%)and low iron mineral content(less than 1%),and good crystallinity,kaolinite deposits occurred at Haerwusu surface mine probably have great economical value in the future.

关 键 词：KAOLINITE GENESIS CARBONIFEROUS-PERMIAN Haerwusu Inner Mongolia Autonomous Region 

分 类 号：P619.2[天文地球—矿床学]