福州盆地马堡红土地球化学元素特征及其气候环境意义

在光释光测年基础上，研究了福州盆地马保（MB）红土剖面的元素组成及其比值变化特点．结果表明：主元素氧化物以SiO2、Al2O3和Fe2O3为主，MgO、Na2O、CaO、K2O含量较低，硅铝率1．81-2．42（平均值为2．00），硅铝铁率1．30-1．87（平均值为1.49），CIA值88．63—95．98（平均值为93．71），Ba值0．07-0．16（平均值为0．10），元素组合及其比值符合亚热带湿热环境下的脱硅富铝的基本成土过程．MB红土的微量元素富集程度较高，相对于上陆壳（UCC）平均组成富V、Cu、Zn、Rb、Co，贫Sr、Ba、Ni、Zr．MB剖面红土形成于晚更新世中期，就微量元素与气候变化的关系而言，Cu、Zn、C0、Sr等化学性质较稳定的元素其高值段大体上对应区域化学风化作用增强，红土发育程度加强，气候暖湿；其低值段对应区域生物化学风化作用减弱，红土发育程度减弱，气候干凉．随着风化强度的增强，Rb／Sr比值增大．元素含量及其比值呈现峰谷旋回变化，指示了晚更新世中晚期以来区域气候以温干一温湿变化为主，并伴随着小尺度的旋回变化，气候总体波动较大．MB剖面地球化学元素记录的区域气候变化过程既是对全球气候变化的响应，也表现出亚热带季风区红土沉积风化的特殊性．

Characteristic of Geochemistry Element of Laterite at Mabao in Fuzhou and Its Climatic Evironment Significance

This paper researches the ratio of the elements and its characteristics of the changes at Maobao profile in Fuzhou on the basis of ESR dating. The results show that： The primary oxides of major elements are mainly SiO2, Al2O3 and Fe2O3, whereas the MgO, Na20, CaO and K20 contents are low. SiO2/Al2O3 ratio ranges from 1.81 to 2.42 （average of 2.00）, SiO2/（AhO3＋Fe2O3） ratio ranges from 1.30 to 1.87 （average of 1.49）, CIA values range from 88.63 to 95.98 （average of 93.71）, Ba values range from 0.07 to 0.16 （average of 0.10）, Therefore, the red earth underwent wet-hot weathering and desilicification-allitization process. Meanwhile, there is a high enrichment degree of the trace elements, the upper continental crust-normalized value for trace elements displays enrichment of V, Cu, Zn, Rb and Co and eluviation of Sr, Ba, Ni and Zr. The red earth of Mabao profile forms in the middle of late Pleistocene. For the relationship between trace elements and climate change, the elements with more stable chemical properties, such as Cu, Zn, Co, Sr etc, their high value in general corresponds to the strength of chemical weathering, as well as the development degree of the red earth, moreover, it means a warm and wet climate, on the contrary, the low value corresponds to the weaken chemical weathering, it means a cold and dry climate. Along with the increase of the weathering intensity, Rb/Sr ratio increased. The spin- ning back change indicated by the contain and the ratio of the elements shows that the major change of regional climate is converting from the weather which is warm and dry to the weather which is warm and wet, with the small scale of the spinning back change since the Middle-late of late pleistocene. The fluctuation of the climate change is obvious totally. The climate changes recorded by the content and their ratio of the geochemical element at Mabao profile is the specific response to the global climatic changes, and meanwhile it displays special zonality at the subtropical monsoon region.