摘要
为获取南岭生态保护区花岗岩风化壳的基础数据,开展了野外实地考察,并初步选取石坑崆海拔1750 m处的一个剖面采样,室内进行色度、pH值、矿物和地球化学等分析。结果表明,该区花岗岩风化壳发育较薄,风化残余物质地较粗,矿物组成以石英、正长石等抗风化能力较强的浅色矿物为主,总体风化程度较低。样品的亮度(L~*)、红度(a~*)和黄度(b~*)值分别为69.09—81.14、0.86—9.42和12.1—23.23,颜色以黄白为主。pH值在4.42—4.74之间,均为酸性。化学元素含量相对母岩发生淋失或富集,如轻稀土明显富集,重稀土发生亏损。从剖面纵向变化看,多数元素的丰度呈现顶、底部高,中间低的特征,与a~*、b~*值的变化基本对应;Si等少数元素与L~*的变化对应,但与其他元素呈完全相反的趋势;pH值自上而下逐渐增大。综合分析认为,当地凉湿的气候环境、良好的植被覆盖状况等,是导致岩石风化速率慢、成土程度低的主要因素;特有的自然环境下,风化壳中的化学元素一方面随水介质向下迁移,一方面因较强的生物作用而向上迁移,同时不同元素对介质pH值敏感度也存在差异,共同作用的结果致使不同活动性的元素在剖面纵向分布上发生了分异。
In order to obtain the basic data of the granite weathered crust in Nanling ecological reserve,field investigation was conducted and samples of the Shikengkong profile were selected to analyze the chromaticity,pH value,mineralogy and geochemistry in the laboratory.The results show that the granite weathered crust in this area is relatively thin and coarse in texture.The mineral composition is dominated by light-colored minerals with strong anti-weathering ability,such as quartz and orthoclase.The overall weathering degree is low.The color of weathered residue is mainly yellowish white with high L*values(69.09-81.14),medium b*values(12.1-23.23)and low a*values(0.86-9.42).And all the residual materials are acidic with pH values varying between 4.42 and 4.74.Geochemical data show weathered crust enrichment or leaching in chemical elements relative to the parent rock,for example,light rare earth elements(LREE)significantly enrich,while,heavy rare earth elements(HREE)leach.As for the vertical variations in the profile,most elements show relatively higher abundance at the top and bottom part and lower abundance in the middle part,which correspond basically to the changes of a*and b*values.However,some elements,including Si,and L*values show the opposite trend.The pH values gradually increase from top to bottom.Based on comprehensive analysis,the local cool and humid climate,good vegetation coverage,etc.,are the main factors that cause slow rock weathering and weak soil formation.Under the unique natural environment,the chemical elements in the weathering crust shift downwards with the water medium on the one hand,and migrate upwards due to strong biological effects on the other hand.At the same time,different elements have different sensitivity to the medium's pH value.Finally,the joint action results in the differentiation of different active elements in the longitudinal distribution of the profile.
作者
付淑清
王钧
熊海仙
宫清华
杨龙
温美丽
FU Shuqing;WANG Jun;XIONG Haixian;GONG Qinghua;YANG Long;WEN Meili(Guangdong Open Laboratory of Geospatial Information Technology and Application,Guangzhou Institute of Geography,Guangzhou 510070,China)
出处
《生态科学》
CSCD
2018年第5期174-179,共6页
Ecological Science
基金
广东省自然科学基金重点项目(No.2017A030311020)
广州市科技计划项目(No.201707010417)
广东省科学院项目(No.2016GDASRC-0209
No.2017GDASCX-0101)
国家自然科学基金(No.41671506)
关键词
花岗岩风化壳
理化特征
石坑崆
南岭
granite weathered crust
physical and chemical characteristics
Shikengkong
Nanling area
