西南极海沉积体系中的氟异常

测区沉积物和间隙水小的氟含量(分别为200～395μg/g和1.18～1.92μg/ml)均远低于所报道的大洋区域平均值(分别约为540μg/g和2.7μg/ml)。研究结果表明,测区沉积物中氟含量分布主要受周围岛屿风化基岩的化学成分制约;沉积物中主要含氟矿物:萤石/磷灰石、黄玉、黑云母等含量极低,氟在沉积物中赋存的矿物相主要与角闪石AX_2Y_5Z_8O_(22)(OH·F)_2]有关。氟含量与碎屑矿物中角闪石的体积比间的关系式可大致表示为:氟含量=217+361nV_H;间隙水中的低氟主要由测区化学风化不发育及氟的钙盐沉积所致。此外,沉积物中强阴离子(HCO_3~-)可交换态含量仅约为太平洋(亦道附近)的1/10、中国南海的1/4和浙江东部沿海的1/2,也反映了测区沉积物中易参与固-液相交换的氟离子含量较低,由此也必将导致间隙水中的低氟。沉积有机质的分解对间隙水的氟含量有一定的贡献,但这种氟易于为沉积物固相所捕获。测区沉积体系中氟的固-液相转换与分配机制可初步描述为: 有机质(氟)垆苎些苎苎苎蟹间隙,k苎苎苎些苎竺些鱼坚固相 (氧化物) 还原 一”—— ,一”

ANOMALY OF FLUORINE IN A SEDIMENTARY SYSTEM, WESTERN ANTARCTIC OCEAN

The fluorine content in bulk sediment and the pore water in Western Antarctic Ocean has been revealed in this paper, 200-395μg / g and 1.18-1.92μg / ml respectively, far below the average reported previously about the world oceans (540μg / g and 2.7μg/ml, respectively). This paper also shows the distribution of the fluorine in sediments of the area is mainly controlled by the chemical composition of the material from the surrounding islands, and the element seems to be incorporated by the hornblende at the most extent, thus the correlation between the element and the hornblende amount in the sediments can be expressed statistically as following: F=217+lnVh. The low concentration of fluorine in the pore water is largely due to the weak weathering process in the islands and the precipitation of the element with calcium, which can be demonstrated as well by the lower value of that in anion-exchangeable (HCO7) F~in the studied area, only about a tenth of that in Pacific Ocean and a quarter in south China and a half in east Zhejiang coast. In addition, the decomposition of the organic matter in the sediment will proba-bally provide fluorine to the pore water but which can be captured easily by the solid phase. Therefore, the possible mechanism of the element's transition and redistribution in the sedimentary system can be preliminarily described as: Early diagenesis decomposition Calcium compounds F Org.F-pore water F-Solid phase