北冰洋西部沉积物黏土的Sm-Nd同位素特征及物源指示意义

Samarium-neodymium isotopic characteristics of the clay-size fraction in surface sediments from the western Arctic Ocean and their implications for sediment sources and transport pattern

通过对北冰洋西部(楚科奇海及北部边缘地带、加拿大海盆)34个表层沉积物样品中黏土组分的Sm-Nd同位素分析,结果表明:(1)黏土组分的Sm-Nd同位素分异明显,可将沉积物划分为北部、西部、南部和东部等多个同位素物源区;(2)在楚科奇海,太平洋入流的向北输运自西向东形成了3个不同的同位素物源区,沉积物的c(147Sm)/c(144Nd)比值、εNd(0)值和TDM年龄自西向东呈递减趋势;(3)在研究区北部,顺时针方向流动的波弗特涡流将马更些河物质向西搬运至加拿大海盆和楚科奇高地,使该区沉积物εNd(0)值明显偏低,TDM偏大;(4)在楚科奇海北部外陆架、海台和陆坡区,太平洋水、大西洋水和波弗特涡流的相互作用使该区沉积物TDM年龄的标准偏差大,同时出现了南-北源和西-南源等同位素混合类型。

Sm-Nd isotopes were measured on the clay-size fraction of thirty-four surface sediments to clarify sediment provenance and transport mechanism in the western Arctic Ocean,the Chukchi Sea,the Chukchi Borderland and the Canadian Basin.Spatial variations of Sm and Nd isotopes of surface sediments indicate there are multiple provenances in the study area.In the Chukchi Sea,three isotope-inferred sediment provenances,which have gradually decreasing c（147Sm） to c（144Nd）,epsilon values of Nd and model ages from west to east,indicate the northward transport paths of the three branches of the Pacific inflows.Due to the transport of the clockwise Beaufort Gyre,sediments are mainly derived from the Mackenzie River and have lower epsilon value Nd of（-13.28^-11.76） and older model age in the Canadian Basin and on the Chukchi Plateau in the north of the study area.Meanwhile,relatively larger model age deviations indicate there are strong water mass and sediment mixing due to co-actions of the Pacific water,the Atlantic water and the Beaufort Gyre on the Chuckchi Rise and continental slope.