长江口及邻近海域悬浮颗粒重晶石特征与成因探讨

海洋环境中重晶石的形成和保存是元素Ba生物地球化学过程的重要环节,在反演海洋古生产力领域具有重要价值。但是多年来该方面的研究主要集中在深海海域,而对河口及近海海域很少涉及。本研究使用SEM和EDX等方法对长江口及邻近海域5个断面36个站位的悬浮体中的重晶石矿物进行了系统的观察,对重晶石颗粒类型、空间分布和影响因素进行了研究。结果表明:该区重晶石颗粒包含自形晶体、长条状晶体、不规则形态晶体和集合体等4种类型,含少量Sr元素,大部分重晶石颗粒表面出现溶蚀现象;重晶石颗粒粒径主要分布在0.5~3 μm。通过研究发现,长江口及邻近海域悬浮体中重晶石的形成主要受到微环境中生物作用的控制,该区初级生产力的发育状态和重晶石颗粒的沉降差异造成重晶石空间分布具有表层含量较多、由岸向外增加的现象。

Feature and Origin of Suspended Barite in the Yangtze River Estuary and Its Adjacent Areas

Formation and preservation of barite are essential to the biogeochemical processes of Ba in marine environment, which have important value in the field of paleooceanopraphy research. However, researches were mainly concentrated on the deep sea and ocean waters for many years and rarely mentioned in estuaries and coastal waters. In this study, suspended mineral barites were observed systematic by scanning electron microscopy and energy dispersive X-ray spectrometry about five sections including 36 stations in the Yangtze River Estuary and its adjacent areas. Barite particle type, spatial distribution and influencing factors were researched. The results indicate that barite particles can be classified into euhedral crystal, elongated crystal, irregular crystal and aggregate, containing a small amount of Sr, occurring erosion phenomena on most of the barite surface. The size of barite particle is mainly in 0.5~3 μm. Barite particle is more in the surface water than the bottom water and is increasing from shore to the open sea, whose formation is related to microenvironment affected by biological processes. The primary productivity and the settling rate of barite particle are two main factors to influencing the barite distribution in that area.