金沙江河流悬浮物与沉积物的矿物学特征及其表生地球化学意义

为研究金沙江流域表生风化特征,系统采集了金沙江和岷江流域32件河流悬浮物和河床砂样品,对其进行了矿物组成分析。结果表明,不同江段河流悬浮物、沉积物的矿物组成大致相同,以石英、方解石、斜长石和粘土矿物为主,局部有白云石、钾长石和角闪石等;粘土矿物主要有伊利石、绿泥石、高岭石和蒙脱石。河床沉积物中非粘土矿物碎屑(岩屑)含量明显高于悬浮物。伊利石为铁镁质,Kubler指数在轻微变质范围内,主要来源于三叠系碎屑岩和砂板岩。金沙江、岷江的河流悬浮物矿物组成与流域内出露的碎屑岩、砂板岩、火成岩、碳酸盐岩等的分布有较好的对应关系。河流悬浮物和沉积物的矿物组成及伊利石结晶指数特征表明流域内以物理风化为主。

Mineralogical Characteristics of Suspended Matters and Sediments in the Jinshajiang River and Their Superficial Geochemical Significance

In order to investigate the superficial weathering characteristics of the Jinshajiang River, 32 samples of the suspended matters and sediments, which were collected from 13 places alone the main drainage of the Jinshajiang River and 3 places alone the drainage of the Minjiang River, have been analyzed by using X ray diffraction. The analytical results indicate that the mineral components of the suspended matters and sediments from different parts or branches of the rivers are approximately identical. They include clay minerals of ferromagnesian illite, chlorite, kaolinite, montmorillonite and non-clay minerals of quartz, albite, and calcite, with dolomite, K-feldspar and hornblende locally. The contents of non-clay mineral fragments of the sediments in the river bed is obviously higher than that of the suspended matters in the river. The Kubler indexes of ferromagnesian illite in the suspended matters and sediments indicate that illite was mainly originated from low-grade metamorphosed Triassic clastic rocks, sandstone and slates. There is good correlation between the mineral components of the suspended matters and sediments and the distribution of clastic rocks, sandstone and slates, igneous rocks and carbonates. The mineral components of the suspended matters and sediments and the Kubler indexes of ferromagnesian illite indicate that the superficial physical weathering is the major type of weathering in the drainage area of the Jinshajiang River.