摘要
大别山地区超高压变质岩的退变质作用表现为后成合晶和后成合晶冠状体的形成，这是薄片尺度不平衡反应的产物．岩石学和矿物微区化学研究表明，后成合晶结构是等化学出溶反应的结果，而后成合晶冠状体结构是通过扩散反应形成的．这两种反应结构都是由页片状和杆状矿物组成，矿物页片的形态与超高压变质岩的ｐＴｔ轨迹相关．后成合晶冠状体形成在一个相对较长的时间内，并且过冷度增加；而后成合晶是形成在过冷度不变的较短时间内．过冷度完全抑制转变作用，就会保存超高压变质矿物的残余，岩石则显示出一个再平衡速率低于状态参数改变速率的变质历史．在变质再平衡作用中。
The retrogression of ultra-high pressure metamorphic rocks from the Dabie Mountains is verified by the development of symplectite and symplectitic coronas.The symplectites and symplectitic coronas are products of disequilibrium reaction on a thin section scale.The study of petrography and micro-area mineral chemistry shows that the symplectite is derived from an isochemical exsolution reaction.On the contrary,the symplectitic coronas result from diffusion controlled reactions.Both symplectites and symplectitic coronas consist of intimately mixed phases with lamellar or rod-like morphologies.While the lamellar spacing is linked to the pTt path of ultra-high pressure metamorphic rocks.The corona formation reaction continued over a relatively long time-span with incressing undercooling.The symplectite formation reaction probably occurred over a shorter time-span with constant undercooling.The increasing undercooling completely suppressed the transformation processes,thus preserving mineral relics of ultra-high pressure metamorphic rocks.Therefore,the rocks experienced a metamorphic history characterized by a re-equilibrium rate lower than the rate of state change variables.The influx of water during metamorphic re-equilibration enhanced the degree of chemical communication and increased the reac￣tion rate.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
1996年第5期501-507,共7页
Earth Science-Journal of China University of Geosciences
基金
国家计委国土司专项基金
国家教委博士点基金
地质矿产部壳幔体系组成
物质交换及动力学开放研究实验室基金
关键词
变质岩
不平衡变质反应
后成合晶
动力学
ultra-high pressure metamorphic rock,disequilibrious metamorphic reaction,symplectite,kinetics.
