Galapagos微板块附近宝石山热液区沉积物稀土元素组成特征  

Rare Earth Elements in the Sediments from Baoshishan Hydrothermal Field near the Galapagos Microplate

作　　者：郭静静[1] 于增慧[1] 李怀明[2] 

机构地区：[1]中国海洋大学海底科学与探测技术教育部重点实验室,山东青岛266100 [2]国家海洋局第二海洋研究所,浙江杭州310012

出　　处：《中国海洋大学学报（自然科学版）》2013年第12期66-74,共9页Periodical of Ocean University of China

基　　金：国家重点基础研究发展计划项目(2013CB429702);中国大洋矿产资源研究开发协会"十二五"重大项目(DY125-11-R-01);浙江省自然科学基金项目(LY12D06006)资助

摘　　要：2009年大洋21航次在Galapagos微板块附近发现了宝石山热液区,本文将采自该区7个站位13个沉积物样品按稀土元素组成特征分为3组:第一组样品以玄武质玻璃碎屑为主,其总稀土含量(∑REE)相对较高,且稀土元素球粒陨石标准化配分模式相对平坦,稀土元素组成与基底玄武岩的特征较为一致;第二组样品以绿脱石和/或Fe-Mn质氧化沉积为主,含有少量玄武质玻璃碎屑,其∑REE含量较第一组明显降低,(La/Sm)N及(Yb/Gd)N升高,Ce负异常程度增加,Y/Ho值也有所增加。随站位逐渐远离喷口,Mn/Fe比值逐渐增加,同时稀土元素组成特征也更接近海水,反映热液羽状流扩散过程中Fe-Mn氧化物颗粒的逐渐沉淀及其对海水的清扫作用。含绿脱石样品(Yb/Gd)N明显升高,这与重稀土在绿脱石中具有较高的分配系数相一致,推断其来自低温流体置换早期形成的Fe氧化物/氢氧化物;第三组样品含有大量自然硫及黄铁矿球粒,其位于喷口附近,应是热液流体直接沉淀产物,但其稀土元素组成不具有Eu正异常这一热液流体的典型特征,也不具有Ce负异常等海水的典型特征,除∑REE含量较低外,其稀土元素配分模式与基底玄武岩相近。这些特征反映该区热液流体可能受到岩浆活动大量去气作用影响或者热液流体在深部曾发生了相分离而富含硫。第二组和第三组样品代表了该区不同时间形成的热液沉积,反映了该区热液活动多期次的特征。During the 21th ocean expedition by Da Yang Yi Hao in 2009, the scientists found the Baoshis han hydrothermal field near the Galapagos microplate, according to the features of the rare earth elements in the sediments, we divided 13 samples （from 7 sites） into three groups： The samples of the first group are mainly composed of basaltic glass debris, they have a higher total rare earth elements concentrations （REE） and show a smooth chondritenormalized REE pattern, they inherited from the basal basalt here; The samples of the second group are mainly composed of nontronite and/or Fe/Mnoxyhydroxide, they have small amount of basaltic glass debris and the REE concentrations are lower than the samples of the first group, on the contrary, the radio of （La/Sm）N and （Yb/Gd）N become higher, the negative Ce anoma lies become stronger, the radio of Y/Ho become higher, too. When the distance of the site from the hy drothermal vent become farther, the radio of Fe/Mn become higher and the REE pattern approaching that in the seawater gradually, so we inferred that the formation for Fe/Mnoxyhydroxide was by direct precip itation from diffuse fluids, and we can see the scavenging effect of the Fe/Mnoxyhydroxide on the trace elements of the seawater. The radio of （Yb/Gd）N in the samples contain nontronite is higher than that in the other samples, this is consistent with the higher partition coefficient of the HREE in the nontronite, so they must form during alteration of Feoxyhydroxide which formed earlier by low temperature fluids; The sample of the third group contains large amount of sulfur and globular pyrite, it was found nearby the hy drothermal vent and must be formed by direct precipitation from hydrothermal fluids, from its REE con centration we can not see the positive Eu anomaly that usually found in the high temperature fluids and the negative Ce anomaly that usually found in the seawater, it has the similar REE pattern with the basal basalt, except the lower ~REE concentrations. All the features o

关 键 词：稀土元素 热液沉积 宝石山热液区 Galapagos微板块 

分 类 号：P592[天文地球—地球化学]