浙江中生代浅成热液金银成矿系统的自组织与耗散结构

Self-organization and Dissipative Struction in Ore-formingSystem for the Mesozoic Epithermal Au-Ag Deposits of Zhejiang,China

浙江中生代浅成热液金银矿床多具明显的热液蚀变 (矿化 )分带—自组织结构。通过对围岩蚀变—矿化过程中的W /R(水 /岩 )比值、元素的带出 (λ)量[EO(I)A] ,熵变 (ΔS)、成矿成岩时差(Δti)和S°298/di(标准熵 /离子密度 )比值、盐度 (St)、P(压力 )、fs2(硫逸度 )和fo2(氧逸度 )、δ18OH2O 和δD、206Pb/204Pb和207Pb/204Pb值等变化的研究 ,表明浅成热液金银成矿系统是一个非平衡 (距热力学平衡态有一定距离 )的开放系统 ,矿床都是在开放环境下成矿流体通过能量的不断耗散并与围岩发生物质交换的一种自组织过程中形成的 ,具耗散结构的特征。一般W/R、EO(I)A和Δti与S°298/di∝MSOD(成矿系统开放程度 )。也就是说 ,围岩蚀变 -矿化过程中W /R比值、元素的带出(入 )量和Δti与S°298/di比值及ΔS值较大 ,一般成矿系统的开放程度也较高 。

Mesozoic epithermal Au and Ag deposits occurring in Zhejiang exhibit thd alterateion Zoning features of thd host rocks resultion from a self-organization evolution of thd ore-forming system,On thd basis of studies of W/R ration (thd water/rock of δD and δ18Oequilibrated hydrothermal system when an isotope exchange took place between fluid and rock),EO(I)A(elements input and output amount of hydrothermal system),Δti(time interval between the formation host magmatic rock and mineralization),Δs(entropy change of mineralization system),S°298/di(entropy standard value and ionic density ratio of ore-forming element)St(salinity of fluid inclusions in minerals),P(ressure of mineralization system),fS2(sulfur fugacity)and fO2(oxygen fugacity),and δD and δ18OH2O,206Pb/204Pb and 207Pb/204Pb in the altered-mineralized process of these Au and Ag deposits,the authors suggest that during thd formation of these Au and Ag deposits the ore-forming system was characteristic of an open system of no equilibrium,resulting in thd self-organization evolution with dissipative structure when an exchange of energy and material took place between ore-forming fluid and host rocks.It is observed from thd data that the values of W/R,EO(I) A and Δti as well as S°298/di vary with the open degree of mineralizing system.This,therefore,indicates,in some field away from thd equilibrium state of ore-forming system evolution,that the higher the values of W/R,EO(I)A,Δti and S°298/di,the more abvantageous the fornation of Au and Ag deposits.