摘要
锶同位素作为物源示踪剂和计时器在海洋地球化学研究中得到了广泛应用,南海东部海域沉积物中非碳酸盐相物质由慢源型火山物质和陆源硅铝物质组成,两者呈互为消长关系,由北向南陆源物质逐渐减少而慢源物质逐渐增多,海盆内发育的火山喷发是慢源型物质的主要来源,陆源物质主要是中国大陆碎屑物质经台湾海峡进入南海,南海东部海域非碳酸盐相沉积物^(87)Sr/^(86)Sr比值分布特点是:(1)陆架和陆坡边缘沉积物中^(87)Sr/^(86)Sr比值高(0.718 994),向东至深海盆东部边缘逐渐降低(0.713 545);(2)东沙群岛、中沙群岛周围海区^(87)Sr/^(86)Sr比值小(0.709 232);(3)台湾海峡南部^(87)Sr/^(86)Sr比值(0.717 940)接近地壳平均值,黄岩岛附近^(87)Sr/^(86)Sr比值(0.704 241),与幔源物质的锶同位素组成一致,这种分布规律说明中国大陆物质对南海东部海域沉积物的贡献由西向东、由北向南逐渐减小,对幔源基性岩组分和陆源硅铝质组分计算得出,东沙群岛以东、黄岩岛以北海区沉积物中陆源硅铝质组分平均含量为87％,台湾省南部基性岩组分含量不到10％,黄岩岛周围基性岩组分含量接近50％,来自台湾海峡的陆源物流向南一直延伸到17°N左右。幔源基性岩组分和陆源硅铝质组分理论计算值与区内沉积物中火山碎屑、陆源碎屑实际分布相一致?
Isotopic studies have provided significant information about the geological provenance in the eastern South China Sea. Noncarbonate fraction in sediments is composed of weathering products of silica rocks and of young volcanic rock of basaltic composition. There is negative correlation between both components. The volcanic activities are the main source of basaltic composition in the basin. The weathering products of silica rocks of continent are supplied by the Changjiang River, part of them are transported into the study area through the Taiwan Strait. The 87Sr/86 Sr ratios vary systematically in the investigation area: (1) High values were found in sediments collected around continental shelf and continental slope(0.718 994). Lower values(0.713 545)occur in the area lyingon east of the continental slope to the edge of the deep basin and beyond. (2) Somewhat lower values occur around the Dongsha Islands and the Zhongsha Islands (0.709 232), the lowest value (0.704 111) was obtained in sample collected around the Huangyan Island, this value is consistent with that of basaltic component. (3) 87Sr/86Sr ratios in sediments obtained from the southern Taiwan Strait were high(0.717 940), close to that of average value of the earth crust. The 87Sr/86Sr ratios decrease markedly in southwest direction toward the deep basin. The weight percentages of the basaltic component and silica component were calculated for each sample in terms of two-component mixing model. This treatment of the data provides estimates of the concentrations of the two components that are at least qualitatively useful. The concentration of volcanogenic detritus in the southern Taiwan Strait is less than 10% . However, this parameter increases to about 50% in the vicinity of the Huangyan Island. Weathering products of silica rock transported throagh the Taiwan Strait gradually deposit in the NNW - NE deep basin. Such a theoretical distribution is quite consistent with the actual occurrence of volcanic detritus and silica detritus.
出处
《海洋学报》
CAS
CSCD
北大核心
2003年第4期43-49,共7页
基金
国家海洋局青年科学基金(2001510)
