多金属结壳Os同位素组成区域性和阶段性偏高异常  

Regional and Periodic Anomalies of Os Isotopic Composition in Polymetallic Crusts

作　　者：王洋 方念乔[1] 刘景昱 Wang Yang;Fang Nianqiao;Liu Jingyu(School of Ocean Science,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质大学海洋学院,北京100083

出　　处：《地球科学》2021年第2期719-728,共10页Earth Science

基　　金：中国大洋矿产资源研究开发协会“十三五”资源环境项目(No.DY135-C1-1-06)。

摘　　要：Os同位素地层法可以得到包含生长间断期的分辨率较高的结壳年代框架,相对传统定年方法具有更优的发展前景.在比对多金属结壳分层Os同位素组成曲线与大洋海水标准曲线从而为多金属结壳定年的同时,研究标准曲线的区域性特征及其与壳源、幔源物质供应的关系.依据比值和趋势贴合原则,得到的多金属结壳生长期包括80~75 Ma、70~65 Ma、60~50 Ma、42~40 Ma、35~28 Ma、15~10 Ma、8~0 Ma.在中、西太平洋地区,麦哲伦和马绍尔海山区结壳Os同位素组成测定值与标准曲线形态和取值贴合良好,而马尔库斯威克和莱恩海山区结壳测定值虽与标准曲线趋势较为贴合,但分别在7 Ma以来和33 Ma以前相对标准曲线取值异常偏高.这种异常偏高现象的出现与2个海山区进、出盛行西风带和赤道信风带的过程有关,结壳在处于风带时接收到风力输运的美洲和亚洲陆源风尘物质,使得其记录的Os同位素组成相对标准曲线偏高.Os isotopic stratigraphic dating method can be used to obtain the age frame of polymetallic crusts including growth discontinuities with high resolution,which has better development prospects than traditional dating methods.In comparison with the stratified Os isotopic composition curve of polymetallic crusts and the standard curve of sea water,we dated for the crusts and at the same time,the regional characteristics of the standard curve and its relationship with the material derived from earth crust and mantle were studied.Based on morphological fit,the growing stages of polymetallic crusts were 80-75 Ma,70-65 Ma,60-50 Ma,42-40 Ma,35-28 Ma,15-10 Ma and 8-0 Ma.In central-western Pacific,the measured curve of Os isotopic composition of crusts in Magellan and Marshall seamounts fits well with the shapes and values of the standard curve,while that of crusts in Marcus-Wake and Line seamounts fits well in the trend but the values are respectively higher since 7 Ma and before 33 Ma.This phenomenon is related to the process during which the crust travelled in and out of the influence copes of prevailing westerlies and equatorial trade winds.The crust received the wind-transported dust materials from the Americas and Asia when it was in the wind belt,which makes the Os isotopic composition recorded by the crust go higher than the standard curve.

关 键 词：多金属结壳 莱恩海山区 马尔库斯威克海山区 标准曲线 Os同位素 海洋地质 

分 类 号：P67[天文地球—海洋地质]