玄武岩发育的几种红壤的矿物特征

本文主要研究不同生物气候条件下由玄武岩母质发育的红壤、赤红壤和砖红壤的理化性质及矿物组成。粘粒中氧化铁的含量都很高,为16.98±0.83%。砖红壤与赤红壤粘粒中高岭石与非晶物质的含量相近,它们之间的差异是赤红壤中没有三水铝石,而含有7—11%蒙皂石。红壤粘粒中高岭石和非晶物质的含量都低于砖红壤和赤红壤,而水云母和蒙皂石的含量较高,也没有三水铝石。粘粒含量、阳离子交换量、硅铝率、硅铁铝率、铁的游离度和风化淋溶系数等都反映了土壤风化程度上的差异,它与水热条件特别是年均温和积温有关,进一步说明生物气候因素引起的土壤性质及矿物组成变化比其它因素强烈。砖红壤与砖红壤性水稻土的差异是在氧化铁形态上;红壤与红壤性水稻土相比,后者粘粒中蒙皂石含量略高,水云母含量略低。

MINERALOGICAL PROPERTIES OF SEVERAL RED EARTHS DEVELOPED FROM BASALT

This paper deals mainly with the physico-chemical properties and mineral compositions of red earths, lateritic red earths and latosols developed from basalts under different conditions of biological climate. The content of iron oxide in clays from all soils was higher, being 16.98±0.83%. The iron oxides in clay fraction were dominated by hematites and geothites, but those in coarse fraction by magnetites, hemames and anatases. The free degrees(free Fe₂O₃/total Fe₂O₃) of iron oxides of red earths, lateritic red earths and latosols were 53.3±2.2%. 71.1±2.8%, and 82.8±3.1% respecaively, and silica-alumina ration 3.29±0.05, 2.33±0.05, and 1.89±0.03 respectively. The degree of allitic enrichment strengthened with increase of remperature and rainfall. The weathering leached coefficient ba (ba=K₂O+Na₂O-CaO+MgO molecular ration) was used to indicate the weathering intensity of soils. The ba valus of red earths. lateritic red earths and latosols were 0.22±0.01, 0.13±0.002, and 0.05±0.01 respectively.