东海中南部海域表层沉积物碎屑重矿物组合分区及其物源分析

    HEAVY MINERAL PROVINCES OF THE SURFACE SEDIMENTS IN CENTRAL-SOUTHERN EAST CHINA SEA AND IMPLICATIONS FOR PROVENANCE

    • 摘要: 对东海中南部海域表层沉积物进行了重矿物鉴定,探讨了其物质来源,并对沉积环境及其主控因素进行了分析。研究区碎屑重矿物共有40余种,还有少量岩屑和风化碎屑。暗色重矿物含量高值出现在100 m以深的东海外陆架,浙闽近海一带暗色重矿物含量低。稳定重矿物含量与离岸距离有一定的相关性,从内陆架到外陆架,含量有逐步增加的趋势。云母类矿物高值集中于浙闽近海内陆架一带;自生黄铁矿也集中浙闽近海水深50 m以浅的内陆架,说明该区水动力偏弱, 主要为还原环境。聚类分析表明,研究区划为2个分区。Ⅰ区包括浙闽近海海域和台湾海峡中西部海域,水深在60 m以浅,主要是长江物质在沿岸流作用下向南搬运沉积。Ⅱ区包括东海中外陆架、陆坡以及冲绳海槽的部分海域,水深多在80 m以深,其物源来自东亚大陆,形成于晚更新世低海平面时期。

       

      Abstract: More than 40 species of heavy minerals and a small amount of lithic and weathered fragments are found in the surface sediments of the middle-southern East China Sea.Sediment sources, depositional environments and the main controlling factors were analyzed and discussed. High percentages of opaque heavy minerals mainly occur on the outer shelf of the East China Sea at water depth deeper than 100 m, while the content of opaque heavy minerals in the Zhejiang-Fujian coastal areas is very low. The content of stable heavy minerals depends upon the distance to the coast, and from the inner to the outer shelf, the content gradually increases. Micas and authigenic pyrite are found concentrated in the inner shelf of Zhejiang-Fujian coastal areas, indicating a rather weak hydrodynamic condition and reducing environment. Cluster analysis suggests that the study area can be roughly divided into two zones. The zone I includes the Zhejiang-Fujian coastal areas and the central and western Taiwan Strait with water depth less than 60 m. The sediments are mainly transported by the southward coastal currents. The zone II mainly includes the middle and outer continental shelf, continental slope and part of the Okinawa Trough in the East China Sea with water depth deeper than 80 m. The sediments are mainly derived from the East Asian continent during the low sea level period of Late Pleistocene.

       

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