湖光岩玛珥湖非残渣态Rb/Sr比值研究及其古气候意义

摘要

湖泊沉积物Rb/Sr比值变化主要受控于Sr含量的变化,而真正反映流域化学风化强度的主要是迁移至集水盆地(湖泊)的溶解态Sr2+,在沉积物中主要以碳酸盐结合态和铁锰氧化物结合态等形式存在.通过对不同赋存状态的Rb/Sr比值与相应的Sr含量之间相关关系的对比分析发现,沉积物非残渣态Rb/Sr比值更好地反映了流域化学风化.根据湖光岩玛珥湖沉积物非残渣态Rb/Sr比值的剖面变化,恢复了该流域一千多年来的化学风化历史.湖光岩玛珥湖非残渣态的Rb/Sr比值在AD704～1850年存在2个低值,即AD740～860年和AD1400～1750年,表明这两个时段该流域化学风化较强,其中AD1550～1700化学风化最强.湖光岩玛珥湖流域的化学风化主要受降水的控制,而温度对它的影响不明显.%The Rb/Sr ratios in lake sediments depend on Sr contents. The chemical weathering of the drainage basin can be better reflected by dissolved Sr2*, which is mainly bound to carbonate and/or to Fe-Mn oxides in lake sediments. Through comparative analysis of Rb/Sr ratios in non-residual, residual and bulk samples, we found that the Rb/Sr ratios in non-residual samples were the closest to the chemical weathering in the catchment basin. The history of chemical weathering of the past 1000 years in the catchment of Huguangyan Maar Lake was reconstructed, on the basis of analyses of non-residual Rb/Sr ratio in the lake sediments. During AD740~860 and AD 1400-1750, the non-residual Rb/Sr ratios were much lower, indicating that the chemical weathering of the two periods were relatively strong. Our results showed that chemical weathering in the catchment was dominantly controlled by precipitation, while the effect of temperature was not obvious.