不同构造环境下蛇纹岩化作用的对比——以西南天山和北祁连造山带为例  

Comparison of serpentinization in different tectonic environments:A case study of the Tianshan and North Qilian orogenic belts

作　　者：姚永祥 肖媛媛[1,2,4] 林晋炎 吴升莹[1,2,3] YAO Yongxiang;XIAO Yuanyuan;LIN Jinyan;WU Shengying(CAS Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao,Shandong 266071,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266061,China;University of Chinese Academy of Sciences,Beijing 100049,China;Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao,Shandong 266071,China;State Key Laboratory of Continental Dynamics,Northwest University,Xi’an,Shaanxi 710069,China)

机构地区：[1]中国科学院海洋研究所海洋地质与环境重点实验室,山东青岛266071 [2]青岛海洋科学与技术国家实验室,山东青岛266061 [3]中国科学院大学,北京100049 [4]中国科学院海洋大科学研究中心,山东青岛266071 [5]西北大学大陆动力学国家重点实验室,陕西西安710069

出　　处：《地质学报》2024年第7期2156-2172,共17页Acta Geologica Sinica

基　　金：崂山实验室科技创新项目(编号LSKJ202204104);中国科学院战略性先导科技专项(B类)(编号XDB42020302);泰山学者工程联合资助的成果。

摘　　要：蛇纹石含水量约为13%,是地球上重要的含水矿物,广泛分布于洋底、俯冲带、弧前等环境。同时,海水、俯冲带衍生流体中的活动性元素(B、Li、As、Sb、Pb、Cs、U、Sr、Ba)也可随蛇纹石化作用而富集在蛇纹石中。因此,蛇纹石可以作为流体和流体活动性元素的载体参与不同的地质过程。然而,不同的构造环境有不同的温度压力、水岩比值、流体性质、氧化还原条件。不同环境下的蛇纹石化作用,不仅会形成不同种类的蛇纹石(例如利蛇纹石,叶蛇纹石),也有可能会导致蛇纹石的元素富集特征不同,这就需要进一步研究流体活动性元素的地球化学行为和元素富集特征。基于对世界范围内不同环境蛇纹岩数据资料的整理分析,结合西南天山和祁连山两个典型造山带的蛇纹岩样品,我们发现深海蛇纹岩与俯冲带蛇纹岩,B、Ba、Cs表现出不同的富集特征:①深海蛇纹岩具有明显更高的B元素含量,可能反映了B在低温下更容易进入到蛇纹岩中;②俯冲带以及弧前环境下形成的蛇纹岩由于可能有沉积物的输入,Ba、Cs的含量相对较高。这一结论有助于以后通过蛇纹岩的元素地球化学特征反演其相对的构造环境。Serpentine,a hydrated mineral with a water content of about 13%,holds great significance on Earth.It is widely distributed across various tectonic environments,such as the ocean floor,subduction zones,and forearcs.In addition to fluids,serpentine can also be enriched with fluidmobile elements(B,Li,As,Sb,Pb,Cs,U,Sr and Ba)through the process of serpentinization.This makes serpentine a crucial host for fluids and these elements in different geological processes.However,different tectonic environments have varying temperatures and pressures,which can result in different properties of fluids.Serpentinization in different environments not only leads to the formation of different types of serpentines(e.g.,lizardite,antigorite),but also results in varying enriched characteristics of serpentine.Thus,further studies are required to understand these differences.By comparing literature data on serpentinite produced in different tectonic environments worldwide,as well as analyzing serpentinite samples from the Southwest Tianshan and Qilian Mountains orogenic belts,we have observed distinct enriched characteristics of B,Ba,and Cs in abyssal serpentinite and serpentinite found in subduction zones:①abyssal serpentinite has significantly higher B contents,suggesting a preference for B in serpentinite formation at lower temperatures;②serpentinite formed in subduction zones displays relatively higher Ba,Cs,and Pb contents,indicating a potential contribution from subducting sediments.This conclusion is valuable in interpreting the tectonic environment associated with serpentinite based on its compositional characteristics.

关 键 词：蛇纹岩 流体活动性元素 深海 俯冲带 弧前地幔楔 

分 类 号：P587[天文地球—岩石学] P542[天文地球—地质学]