花岗岩风化程度的化学指标及微观特征对比——以香港九龙地区为例

據香港九龍 3個不同工程場地取得的 1 49件不同級別的風化花崗巖樣品的化學分析結果 ,用統計學方法 ,從反映巖石風化程度的 1 8項化學指標中選取 9項進行了分析計算。對其結果及其與風化程度分級的關系的研究表明有 4種指標比較理想。通過對樣品微觀特征的觀察研究和礦物成分、微孔隙率以及綜合顯微巖石指標 (Ip)進行了描述和定量分析 ,發現其中一些指標有一定相關性。這些化學指標和微觀特征相關的統計值在一定程度上可定量表征花崗巖的風化程度 ,即 :隨風化作用進行 ,堿、堿土金屬組分逐漸淋失 ,脫硅、富鋁鐵化作用逐漸加強 ;相應地 ,先是鈉長石風化成高嶺石 ,其次為云母和鉀長石的風化。粘土礦物所占體積百分比隨風化程度增高而變大 ,至殘積土 (Ⅵ級 )時已達 50 %左右 ;Ip 指標值下降 ,微孔隙率增高。文章綜合出各個風化級別的指標變化范圍及平均值供花崗巖分布區花崗巖風化野外調查和研究工作參考.According to the analytic data of 149 samples from 3 sites of Kowloon Peninsula, Hong Kong, a series of statistic values of chemical proportions and weathering indices are calculated, and their relations with the weathering grades are discussed .Then the micro-properties involving mineral constituents, micro-fracture contents and sophisticated micropetrographic index ( Ip ) are also quantitatively described, some of them are related with each other to an extent .The statistic values corresponding to the chemical, mineral and micro-structural properties quantitatively depict the material weathering grades of granitic rocks .With the progressive weathering, the alkalis and alkaline earth leach out, and finally eliminate .The content of silica decreases while that of sesquioxide goes up . Accordingly, the plagioclase diminishes and the potash feldspar the next .The clays are formed more and more and reached 50 %in grade Ⅵ .The Ip gradually goes down and the micro-fractures merge more clearly .To sum up, the total statistic values of various kinds are listed, which is perhaps of referential for the regional geo-technical engineering investigation and research works .