摘要
本文研究了玄武岩发育的红壤,花岗岩发育的红壤和山地黄壤中的轻、重矿物。轻矿物的主要成份是石英和长石,石英/长石的比率是玄武岩发育的红壤>花岗岩发育的红壤>花岗岩发育的山地黄壤。重矿物的主要成份是各种含铁矿物及铁氧化物裹着的石英粒,此外还有少量的角闪石、锆石、云母和电气石等。锆石与土壤的风化强度变化有密切关系,作为土壤风化演变过程的指示矿物是很合适的。
Study on light and heavy minerals in red soils developed from basalt, and in red soils and mountain yellow soils developed from granite showed that (1) the contents of heavy minerals in red soils, derived from basalt were much higher than that in other red soils, especially Xuwen laterite in which the contents of heavy minerals were about 90% in 10—50μ frac tion, 35—65% in 50—100μ fraction, and 6—33% in 100—250μ fraction, as compared to less 6% in most of soils such as red soil derived from granite. In fact, many heavy mineral grains in red soils derived from basalt consisted of quartz coated or cemented with ferric oxide which could not be removed by boiling 10% HCl. As is known to all, the specific gravity of quartz is 2.65, while that of quartz grains enveloped or cemented by ferric oxide raised to over 2.9, thus the quartz became 'heavy mineral', and resulted in the increase of heavy mineral content in this soil. (2) In<50μ fraction, content of feldspar in red soils derived from basalt was lower than that in other soils, being only 5.3%, as compared to over 13.4% in other soils. The ratio of quartz to feldspar in red soils derived from basalt was higher than that in red soils and mountain yellow soils derived from granit(?). The reasion is that the red soils derived from basalt mainly contained anorthite and bytownite which were liable to weather, while the red soils and mountain yellow soils derived from granite mainly contained K-feldspar, albite, and oligoclase which resisted to weathering. (3) There was a high proportion of iron minerals in the heavy mineral. The results studied on the 10—50μ fraction indicated that the content of iron minerals in red soils derived from basalt and granite accourted for 78% of the heavy mineral. Distribution of iron minerals was affected by temperature and moisture. In red soils derived from basalt, more limonite, hematite and ilmenite formed under high temperature and humid conditions, and the content of iron minerals decreased as temperature and moisture dropped, especially limonite, it was very obvious to decrease. (4) The content of zircon in intensely weathered red soils derived from granite was higher, making up 9—19% of the heavy mineral. However, in weakly we thered red soils it reduced obviously, only making up about 1% of the heavy mineral. Distribution of zircon in profile trends towards decrease with increasing depth. Consequently, the quantitative change of zircon could be used to reflect the process of soil weathering.
出处
《土壤学报》
CAS
CSCD
北大核心
1990年第4期385-391,共7页
Acta Pedologica Sinica
基金
国家自然科学基金委员会
