海底热液循环中矿物沉淀过程数值模拟  

Numerical Modeling of Mineral Precipitation in Seafloor Hydrothermal Circulation

作　　者：郭志馗 陈超[1,2] 陶春辉[3] 胡正旺 许顺芳[1,2] Guo Zhikui;Chen Chao;Tao Chunhui;Hu Zhengwang;Xu Shunfang(Institute of Geophysics&Geomatics,China Universily of Geosciences,Wuhan 430074,China;Hubei Subsurface Muli-Scale Imaging Key Laboralory,China University of Geosciences,W uhan 430074,China;Key Laboralory of Submarine Geosciences of Stale Oceanic Administration,Second Instiute of Oceanography of MNR,Hangzhou 310012,China)

机构地区：[1]中国地质大学地球物理与空间信息学院,湖北武汉430074 [2]中国地质大学地球内部多尺度成像湖北省重点实验室,湖北武汉430074 [3]自然资源部第二海洋研究所国家海洋局海底科学重点实验室,浙江杭州310012

出　　处：《地球科学》2021年第2期729-742,共14页Earth Science

基　　金：国家重点研发计划项目(Nos.2016YFC0600507,2018YFC0309901)。

摘　　要：为了探索高渗透性洋壳中高温热液循环系统的形成机制,以数值模拟为手段研究热液循环中的矿物沉淀过程及其对洋壳渗透率的反馈.在热液对流-矿物反应模型中考虑了硬石膏、黄铁矿和黄铜矿的沉淀和溶解反应,基于矿物的溶度积计算矿物的沉淀/溶解量,并将其转换为渗透率的变化.结果显示,黄铁矿和黄铜矿分布于350~380℃等温线范围内,并随着热液温度升高而逐渐向海底推移.海水被加热及与热液混合过程中沉淀出硬石膏,在热液上升通道两侧形成低渗透性的烟囱状结构,降低了海水-热液混合程度从而使热液温度升高.高温热液通道建立后,便会有更多的金属物质随着高温热液被运输至浅层洋壳或海底.模拟结果为理解海底高温热液喷口的形成机制提供了借鉴.To understand the mechanism of high-temperature hydrothermal system in highly permeable oceanic crust,a reactive hydrothermal convection model is proposed to solve mineral precipitation and its feedback on permeability.Mineral reaction of anhydrite,pyrite and chalcopyrite are accounted in the model.Precipitation and dissolution can be solved using solubility product of the mineral and transformed into permeability change.The results suggest that pyrite and chalcopyrite are precipitated as cap-like structure around 300-380℃isotherm.With hydrothermal temperature increasing,the cap-like structure is moving to seafloor.Anhydrite is precipitated as chimney-like structure around focus flow by seawater heating and seawater-hydrothermal mixing.The low permeable chimney-like structure prevent seawater-hydrothermal mixing and thus keep hydrothermal at high temperature.Once the high-temperature focusing flow is formed,more metal can be dissolved in hydrothermal and be transported to shallow crust and seafloor.The numerical simulation results could help to understand the mechanism of high-temperature hydrothermal venting.

关 键 词：海底热液系统 高温喷口 数值模拟 矿物沉淀 黑烟囱 地球物理 

分 类 号：P738.6[天文地球—海洋地质]