CAJ | 학술논문

传统观点认为地质时期海水成分一成不变，然而包裹体测试技术的迅速发展，揭示出显生宙以来海水成分至少发生过两次大的旋回变化。本文基于世界多个海相沉积盆地的原生石盐包裹体实测数据，探讨了显生宙以来古海水地球化学、水化学类型、蒸发岩矿物组合特征的显著变化，并结合 EQL／EVP 卤水蒸发平衡模型，定量模拟了两种典型海水的蒸发演化过程、析盐规律和矿物组合特征，分析和探讨了中国海相沉积盆地的成钾前景。应用 Spencer 相图，揭示出在过去的600 Ma 期间，古海水成分点在 Cl-SO4和 Ca-Cl 两个相区内随时间发生周期性的震荡变化，志留纪、泥盆纪、侏罗纪和白垩纪的海水类型与现代海水迥然不同，为典型的 Ca-Cl 型水。Mg-2K-SO4／ Mg-Ca-2K J?necke 相图分析结果显示，这些时期的石盐包裹体成分，位于富 CaCl2、贫 MgSO4的 Mg-Ca-2K 相图中光卤石、钾石盐稳定相区，指示原始海水相对于现代海水具有富 Ca、贫 Mg 的特征，其析出的典型矿物组合主要有石盐、钾石盐、光卤石和溢晶石等。而新元古代、二叠纪和第三纪大部分石盐包裹体成分，都落到了 Mg-2K-SO4相图上的钾盐镁矾和钾石盐相区，和现代海水成分较为类似，具有富 Mg2＋、SO2－4的特征，其析出的典型矿物组合包括石盐、钾盐镁矾、硫镁矾、钾石盐和光卤石等。EQL／EVP 定量模拟结果显示，富 SO4-Mg 型的海水和富 Ca-Cl 型的古海水，蒸发演化路径和矿物析出序列截然不同，Ca-Cl 型的海水更易形成优质钾盐矿床，有利的成钾时段为寒武纪-早石炭世、侏罗世-新生代早中期。
전통관점인위지질시기해수성분일성불변，연이포과체측시기술적신속발전，게시출현생주이래해수성분지소발생과량차대적선회변화。본문기우세계다개해상침적분지적원생석염포과체실측수거，탐토료현생주이래고해수지구화학、수화학류형、증발암광물조합특정적현저변화，병결합 EQL／EVP 서수증발평형모형，정량모의료량충전형해수적증발연화과정、석염규률화광물조합특정，분석화탐토료중국해상침적분지적성갑전경。응용 Spencer 상도，게시출재과거적600 Ma 기간，고해수성분점재 Cl-SO4화 Ca-Cl 량개상구내수시간발생주기성적진탕변화，지류기、니분기、주라기화백성기적해수류형여현대해수형연불동，위전형적 Ca-Cl 형수。Mg-2K-SO4／ Mg-Ca-2K J?necke 상도분석결과현시，저사시기적석염포과체성분，위우부 CaCl2、빈 MgSO4적 Mg-Ca-2K 상도중광서석、갑석염은정상구，지시원시해수상대우현대해수구유부 Ca、빈 Mg 적특정，기석출적전형광물조합주요유석염、갑석염、광서석화일정석등。이신원고대、이첩기화제삼기대부분석염포과체성분，도락도료 Mg-2K-SO4상도상적갑염미반화갑석염상구，화현대해수성분교위유사，구유부 Mg2＋、SO2－4적특정，기석출적전형광물조합포괄석염、갑염미반、류미반、갑석염화광서석등。EQL／EVP 정량모의결과현시，부 SO4-Mg 형적해수화부 Ca-Cl 형적고해수，증발연화로경화광물석출서렬절연불동，Ca-Cl 형적해수경역형성우질갑염광상，유리적성갑시단위한무기-조석탄세、주라세-신생대조중기。
The traditional view is that the composition of sea water is invariable during the geological period. However,with the rapid development of the testing technology of fluid inclusion,more and more measured data of fluid inclusion reveal that the seawater composition occurred at least two cyclic changes during the Phanerozoic period.Based on measured data of primary halite fluid inclusions from multiple marine basins in the world,this paper discusses the paleoseawater geochemistry,water chemistry type, significant change of evaporite mineral assemblages since Phanerozoic period.Combined with the brine evaporation balance model of EQL/EVP,this study simulates quantitatively the evaporation process of two typical seawater, analyses the salt precipitation law and mineral assemblages characteristics during evolution process,and evaluates the prospect of potash deposits in marine sedimentary basin in China.The Spencer diagram reveals that the paleoseawaters composition occurs cyclical shift between Cl-SO4 and Ca-Cl phase zone during the past 600 Ma,the seawater type of Silurian,Devonian,Jurassic and Cretaceous is typical Ca-Cl type,which is significantly different from modern seawater.The Mg-2k-SO4/ Mg-Ca-2k J?necke diagram show that the halite inclusions composition of Silurian,Devonian,Jurassic and Cretaceous are located in Mg-Ca-2K phase zone of CaCl2-rich and MgSO4-poor,Sylvite,carnallite stable phase zone, which indicate the original seawater has the feature of Ca-rich and Mg-poor in comparison with modern seawater, and the corresponding typical mineral assemblages are halite, sylvite, carnallite and tachyhydrite.But most of halite inclusions composition of Late Proterozoic,Permian and Tertiary,located in sylvite and kainite phase zone of Mg-2K-SO4 diagram,is similar to modern seawater composition characterized by Mg-rich and SO4-rich,and the typical mineral assemblages is halite,kainite,kieserite, sylvite and carnallitite.The quantitative model results of EQL/EVP show that the SO4-Mg-rich and CaCl2-rich seawater have obviously different evaporation evolution path and mineral precipitation sequence,the CaCl2-rich paleoseawater is conducive to quality potash deposits,and the favorable metallogenic epoch is from Cambrian to Early carboniferous,and from Jurassic to early-middle cenozoic.