东海东北部陆架表层沉积物碎屑矿物分布及其物源分析

为深入了解东海外陆架表层沉积物物质来源及沉积环境特征,运用粒度和矿物学研究手段,对济州岛西南海域180个表层沉积物样品进行沉积物类型和碎屑矿物组成分析,探讨了矿物分布特征与沉积环境的相互关系,进一步明确表层沉积物的输运模式、物质来源及环流系统对其分布的影响。结果表明,研究区重矿物共34种,以普通角闪石、绿帘石和钛铁氧化物类矿物为主,橄榄石和变质岩矿物是区别内陆架沉积的标志性矿物。轻矿物共13种,以普遍发育的海绿石为特征。根据碎屑矿物组合分布特征,将研究区分为Ⅰ、Ⅱ两个矿物组合区,并进一步将Ⅱ区划分为两个矿物组合亚区。中部现代沉积区(Ⅰ区)矿物组合为普通角闪石-绿帘石-自生黄铁矿-钛铁氧化物类矿物-片状矿物,表现为现代陆源沉积特征,物质来源以黄河为主,生物沉积和自生沉积也是该区重要的沉积方式。外围残留沉积区(Ⅱ区)为沉积作用缓慢的弱还原环境,Ⅱ-1亚区矿物组合为普通角闪石-绿帘石-钛铁氧化物类矿物-石榴石-橄榄石,认为是以古长江的残留前积沉积为基底,受到Ⅰ区影响,接受了少量悬浮再悬浮的现代陆源沉积,同时又具有区域独特性。Ⅱ-2亚区矿物组合为绿帘石-普通角闪石-钛铁氧化物类矿物-石榴石,认为是古长江的残留沉积,在中部冷涡作用下,很少有现代物质的加入,区内不排除在当地环境生长的生物体作用下与Ⅰ区互相调整的物质。本研究为今后在东海外陆架深入开展沉积学、矿物学及环境演化研究提供了新的参考。

Distribution and provenance of detrital minerals in surface sediments of the northeastern East China Sea

In order to understand the source of surface sediments and the characteristics of the depositional environment on the East China Sea Shelf, 180 surface sediment samples from the southwest waters of Jeju Island were analyzed in terms of sediment types and detrital mineral compositions by means of grain size and mineralogy. The relationship between the distribution characteristics of minerals and the depositional environment was discussed. Based on the sedimentary dynamics method, the influence of the transport mode, material source and circulation system of the surface sediments on its distribution was clarified. Thirty-four heavy minerals were identified, mainly common amphibole, epidote, and metallic minerals. Olivine and metamorphic rock minerals are the landmark minerals distinguished from inland shelf deposits. Thirteen light minerals were identified, which are characterized by commonly developed glauconite. According to the distribution characteristics of clastic mineral assemblage, the study area could be divided into two mineral assemblages named as Zone Ⅰ and Zone Ⅱ, correspondingly. Zone Ⅰ occupied in the central modern sedimentary zone characteristic of ordinary amphibole, epidote, authigenic pyrite, metallic minerals, and sheet minerals, showing colors of modern terrigenous sediments from mainly the Yellow River, biological, and authigenic sediments. Zone Ⅱ covered the peripheral residual sedimentary zone characteristic of weak reductive environment with slow sedimentation rate. Zone Ⅱ could be divided into two subzones. Subzone Ⅱ-1 features ordinary amphibole, epidote, metallic minerals, garnet, and olivine, indicating the origin of the ancient Yangtze River on the basement of foreset sediments with the influence of Zone Ⅰ, receiving a small amount of modern terrigenous suspended or resuspended sediments with own regional uniqueness. Subzone Ⅱ-2 contains epidote, ordinary hornblende, metal minerals, and garnet etc, reflecting residual sediments of the ancient Yangtze River. Under the action of the central cold vortex, few modern materials could be added. Meanwhile, local organic substances in local environment that are mutually exchanged with zone Ⅰ cannot be excluded from the area. The research content of this paper provides a new reference for further studies on sedimentology, mineralogy and environmental evolution on the East China Sea Shelf.