【作者】 闫秋实；

【导师】 尹观；

【作者基本信息】 成都理工大学 ， 地球化学， 2016， 博士

【摘要】 本论文依托国家自然科学基金《川南主要含卤地层的氘过量参数演化》和国家地质调查专项研究项目《四川三叠纪富钾卤水富集规律及有利地区调查评价》,以四川盆地的主要含卤层的卤水为研究重点,在综合整理和系统研究前人的成果和相关地球化学数据资料的基础上,运用构造地质学、沉积学、水文地质学、矿藏地球化学及元素和同位素地球化学等多学科理论方法,采取地下水氘过量参数演化和同位素组成相结合的研究新思路,重点对四川盆地储卤地层的地质构造特征、盆地成卤流体的来源及演化、盆地中下三叠世富钾卤水的成藏机理及找矿方向三方面展开研究,并获得如下主要结论:（1）与其他含卤岩系相较,中下三叠统含卤岩系,因为沉积阶段古卤水浓度较高,又有火山喷发来源沉积物中硼、钾等微量组分的加入;淋滤阶段岩层未发生褶皱,裂隙不发育,渗入水的淋滤置换仅局限于剥蚀面附近;长期处于深埋封闭阶段,含盐系中的蒸发岩脱出水携带着大量易溶盐组分,在—定程度置换了储层水,并进而向正变质方向发展;后期构造的变动开启、现代淋滤仅局限于部分高背斜区及盆地的边缘地区。因而该含卤岩系的富钾卤水品质显著好于其他含卤岩系。（2）盆地卤水水文地球化学特征具有明显的分层性和分区性,卤水常量水化学组成与矿化度一致,具有同一层位上的一致性和不同层位之间的明显差异。中下三叠统及寒武系含卤岩系的卤水矿化度则普遍较高,以C1—Na型为主,并以较高含量SO₄^2-为特点。该类含卤岩系为海相沉积层中不含Ba²⁺者,且以B₂O³、K⁺含量较高为特色,其中尤以T₁j⁵、T₂l¹及T₂l³含卤层为最突出。K·10³Cl一般在10³0之间变化,γNa/γC1则多在0.97⁰.71间,Br·10³/CI普遍在3⁹间,卤水浓度有随埋藏深度增加,封闭条件亦随之变好的趋势。研究表明,该含盐岩系的原始沉积中曾沉积过钾盐。（3）海相沉积含卤层中卤水,其同位素相对集中于δD-δ¹⁸O图右方,氧同位素高于海水,而氢同位素组成则均低于海水。卤水的主体应源于海水,不同时期海水的蒸发程度有所差异。自震旦系含卤层卤水分布区而上,经寒武系、二叠系茅口组至三叠系嘉陵江、雷口坡组,卤水δD值随时代变新而相对富重同位素组成;陆相沉积含卤层卤水,主要源于大气降水,其同位素组成落于大气降水线附近;海、陆过渡相含卤层（上三叠须家河组）卤水,同位素组成落于海相沉积含卤层卤水与大气降水端元之间,为大气降水与蒸发海水的混合。（4）盆地内不同时代含卤层,卤水氘过量参数（d值）有明显随时代变老而逐步降低的趋势。三叠系雷口坡组-嘉陵江组、二叠系茅口组、寒武系及震旦系含卤层均系碳酸盐岩地层,反映出水/岩作用十分强烈,同时显示卤水氘过量参数的变化是时间的函数;三叠系不同组的含卤层卤水d值的变化与平面分布和含卤层埋深具有一定关联,含卤层埋深愈深,卤水氘过量参数的（d）值也就愈低。（5）四川盆地的早、中三叠世富钾卤水的流体来源主要由沉积同生水、脱出的矿物结晶水构成,它们均来源于当时的盆内海水,受后期地表水的影响很小,其化学物质来源（如K、Sr、Mg等）与晚二叠世的峨嵋山玄武岩有关;川西龙门山深大断裂频繁活动,深部热液上涌所带入的深部物质与能量,是造成西部凹陷储层中的卤水（平落4井）与川东卤水（宣汉:川25井）相比,相对富集重金属元素（Cu、Pb、Zn、Sn、Cr、Ga）和B、K⁺,Mg²⁺、SO₄^2-浓度进一步贫化的重要因素。（6）依据卤水的地质地球化学特征,初步划出了富钾卤水成藏的主要成因类型:同生沉积型、淋滤混合型与沉积改造型;于此基础之上,经综合分析,提出了四川盆地富钾卤水藏找矿方向的思考:四川盆地富钾卤水藏重点靶区的确定,应聚焦于盆地内早、中三叠世海相沉积的凹陷区,特别是与深大断裂有关的次级断裂发育地带的富钾矿物沉积盐盆中,尤其是盆周深大断裂的交汇地带,更具蕴藏有高浓度富钾卤水的可能性。更多还原

【Abstract】 The paper focuses on the brine of major halogen-containing layer on the south of Sichuan Basin supplemented by other areas of the basin,some of the samples were collected continuously.Combined with previous studies data and related isotopic data,the paper firstly discusses the deuterium excess evolution of brines,which provides a new thought and forms the basis for further study of the brine accumulation mechanism.By studying of the geological structural characteristics of brine-bearing stratum,evolution of brines fluid source of Upper-Middle Triassic and the forming of potassium rich brines,we draw some conclutions as follow:（1）Comparing with other brine-bearing strata,Triassic Leikoupo-Jialingjiang Formations which brine reservoir is widely dispersed over the Sichuan basin,have high quality brine and long developmental history.The study indicates that the brine reservoir is composed of compact rocks with a low porosity and a low permeability,being unfavourable for brine migration.Brine migration and accumulation are cont rolled by f racture systems.（2）The hydrogeochemical characteristics of the brines in Sichuan basin assume obviously layered and partitioned.The major hydrogeochemical compositons,in keep with salinity,are consistent in the same Formation and variant between different Formation.The brine-bearing strata of Upper-Middle Triassic and Cambrian which were marine sedimentary have high formation water salinity,mainly Cl-Na style with high SO₄^2-.This kind of strata is characteristic by high K⁺、B₂O³ without Ba²⁺,particularly such as T₂l¹、T₂l³ and T₁j⁵.（3）On theδD-δ¹⁸O plot,the oxygen and hydrogen isotope compositions of brines sampled in marine sedimentary brine-bearing strata fall in the right part of the plot,and the hydrogen isotope compositions are lower than SMOW,while oxygen isotope compositions are higher than SMOW.From Sinian stratum,up to Cambrian,Permian Maokou Formation Triassic Jialingjiang Formation,theδD value of brines gets relatively positive with the strata becoming younger.Brines of terrestrial deposit are considered to be derived from precipitation and the isotope compositions fall in the neighborhood of the globe meteoric water line（GMWL）.Brines of transition between marine and terrestrial deposit（Upper Triassic Xujiahe Formation）haveδD andδ¹⁸O values falling between the two end members of marine deposit brines and precipitation,implying that the brine is a mixture of precipitation and vaporing seawater.（4）In the basin,water samples from the brine-bearing strata of different ages,show various deuterium excess（d）with evident decreasing tendency as the age of strata gets older.The brine-bearing strata of Triassic Leikoupo-Jialingjiang Formations.Permian Maokou Formation,Cambrian and Sinian are all carbonate rocks which have intensive action with water.Having the same lithology,the strata present brines whose deuterium excess essentially change with time.All brine-bearing strata surrounding the basin or locating at t he faults,as well as those brine wells exploited for resources,have been obviously influenced by precipitation supply.Therefore,the deuterium excesses of their brines have increased to different extents,depending on the amount of mixing precipitation.The change and distribution of d values of the brines f rom different strata of Triassic are related to the burial of stratum depth.The deuterium excesses of brine become lower with the increase of burial depth of the stratum.（5）The deep formation brines,very rich in potassium,found in the Upper-Middle,are suggested that originated from marine,almost not affected by precipitate water since formed.The sources of K,Sr,Mg are suggested that related to Emeishan basalts eruption in late Permian.It’s about Longmenshan deep fault activities which made more Cu、Zn、Pb、Sn、Cr、Ga and K⁺、B and less Mg²⁺、SO₄^2-of the western brines comparing with the eastern of Sichuan basin.（6）According to the characteristics of geology and geochemistry,the potassium rich brines can be grouped into homozygous depositional brine,leaching mixed brine and deposition deformation brine.On that basis,key target areas were given for prospecting potassium rich brines.更多还原