长江与黄河河口沉积物环境磁学特征及其对比研究

对采自长江现行主河道和黄河入海口处的表层沉积样品进行了环境磁学参数的测量和对比研究.结果表明:长江和黄河河口沉积物的磁性载体主要是亚铁磁性物质,亚铁磁性矿物晶粒以假单畴-多畴为主,同时亦有超顺磁晶粒的存在;长江河口沉积物的磁性明显强于黄河河口沉积物,特别是质量磁化率、非磁滞剩磁及饱和等温剩磁,两者相对偏差在40%以上;在粗粒级沉积物(>0.063 mm)中,长江河口沉积物的磁化率与全样磁化率平均值差别较小,在4%左右;黄河河口沉积物差别很大,可达34%.两者的差别反映了长江和黄河沉积物中磁性矿物赋存方式的差异;长江和黄河河口沉积物磁性特征的差异与两者粒度特征对比明显.长江和黄河河口沉积物的这些磁学方面的差别是源岩特征和气候环境差异上的反映,可以作为判别两者物源的有效示踪剂.

The characteristics of the environmental magnetism in sediment from the river mouths of the Changjiang River and the Huanghe River and their comparison study

Based on the environmental magnetism measurements on the sediment samples from the Changjiang River and the Huanghe River mouths,the basic characteristics of the environmental magnetism for the sediment from the Changjiang River mouth and the Huanghe River mouth are analyzed respectively and compared with each other.The results indicated that ferrimagnetic minerals are the main magnetism carriers for both the Changjiang River and the Huanghe River sediment.Additionally the ferrimagnetic minerals are mostly composed of psudo-single domain and multi-domain grains together with a little superparamagnetic grain.The magnetic intensity in the sediment from the Changjiang River mouth is obviously higher than that from the Huanghe River mouth,especially in terms of magnetic susceptibility,anhysteretic remanent magnetization and saturation isothermal remanent magnetization.For the samples from the Changjiang River mouth there is no significant discrepancy of susceptibility detected between the coarser-grain part and the total samples,while it is high up to 34% for the samples from the Huanghe River mouth,indicating that such difference of susceptibility between the samples from the two river mouths is derived from the dissimilar existence of the minerals;The difference in the environmental magnetism between the sediment samples from the two river mouths is corresponding with the different distribution patterns of grain size.The different environmental magnetism characteristics of the sediments reflect the different source rocks and the climate for the sediment generation.Therefore the parameters of the environmental magnetism can be regard as an effective tracer for identifying the sediment provenances of the Changjiang River and the Huanghe River.