沙尾风化壳高岭土矿床的研究

A STUDY OF A WEATHERING CRUST KAOLIN DEPOSIT IN GUANGDONG PROVINCE

广东沙尾高岭土矿属残积型风化壳矿床,分为白云母二长花岗岩钠化高岭土矿和斑状二长花岗岩高岭土矿。矿石主要组成矿物包括高岭石、埃洛石,伊利石及石英,含少量长石。原矿石SiO_2高达67—70％,Al_2O。20—23％,精矿SiO_2 47—50％,Al_2O_3 33—36％。矿石铁、钛含量低,SiO_2/Al_2O_3在2.2—2.5之间。高岭土的成矿作用分为前期热液蚀变阶段和后期表生风化阶段,前期主要以钠长石化和白云母化为主,后期通过地表水淋洗发育成高岭土风化壳。

The Shawei deposit in Guangdong province is a weathering residual type kaolia deposit. The kaolin deposit is of good quality and has considerable res- serves. Its products are widely used as high-quality raw materials for ceramics and papermaking.The kaolin deposit can be further divided by species of its associated rare earth minerals into a albitized kaolin deposit of muscovite monzonitic granite and a albitized kaolin beposit of porphyritic two-mica monzoitic granite. The ores consist mainly of kaolinite, halloysite, illite and quartz with a small amount of feldspar. In V_4 orebody, kaolinite makes up 70—85% and illite 9—20%; in V_2 orebody, kaolinite makes up 50—82% and illite 12—27%. Halloysite is well developed in the middle part of the orebody and a small amount of gibbsite occur near the upper part as a result of the weathering —dehydration at the surface. The primary ores have 67—70% SiO_2 and 20— 23% A1_2O_3; nevertheless, after sieving on 320 mech, SiO_2 is decreased to 47— 50% whereas A1_2O_3 is increased to 33—36%.In chemical composition, kaolin shows some characters: (1) TiO_2 content is very poor (generally lower than 0.02%), (2) Fe_2O_3 content is generally lower than 1% and (3) the other elements such as Na, Ca, Mg and Mn are very little in content and the SiO_2/Al_2O_3 ratio is in the range of 2.2—2.5.The ore-forming process of the Shawei kaolin deposit can be divided into two s ages: (1)the early alteration stage and(2) the late surface weathering stage. During the first stage, the granite mainly experienced albitization and muscovitization which provided rich materials for the surface weathering; during the second stage, the altered granite developed into the weathering crust of kaolin through the leaching process of surficial water which took such cations as Na, Mg and Ca and part of SiO_2 out of the parent minerals of the altered granite.