东营凹陷沙四下亚段沉积环境特征及沉积充填模式

沉积盆地中沉积环境特征控制了砂体沉积成因类型及盆地沉积充填模式。通过对东营凹陷丰深2井、官112井及梁120井沙四下亚段泥质沉积物系统取样,进行全岩X衍射分析和常量及微量地球化学元素分析,在此基础上对东营凹陷沙四下亚段古气候和古盐度指标进行分析。结果表明,古气候指标Rb/Sr比值与石英+长石含量、Cr元素含量及P元素含量呈正比,含量增加反映了气候相对潮湿,与古盐度指标碳酸盐+硫酸盐含量呈反比,其含量增加反映了气候相对干旱。东营凹陷沙四下亚段沉积时期气候干湿交替频繁,气候潮湿时期相对湖平面上升,湖水盐度降低;气候干旱时期相对湖平面下降,湖水盐度升高,使得此时期湖泊呈现为高频振荡性盐湖特征。气候潮湿时期以沉积碎屑沉积物为主,包括冲积扇、浅水型三角洲、滨湖滩坝及近岸水下扇沉积,由于湖水盐度较低,洼陷带主要沉积泥岩、灰质泥岩、含膏泥岩和少量泥质膏岩;气候干旱时期相对湖平面下降,湖泊水体盐度升高,洼陷带以沉积膏盐岩为特征,垂向上具有含膏泥岩、泥质膏岩、膏岩和盐岩的演化序列,平面上表现为由湖泊边缘向湖泊中心发育灰质泥岩、含膏泥岩、泥质膏岩、膏岩和盐岩的环带状结构特征。     

安徽定远县三和集镇石膏矿地质特征浅析

安徽省定远县关塘石膏矿矿区位于定远县城东北部,行政区划隶属定远县三和集镇管辖。通过对其主要地质特征及矿床成因分析,认为矿床赋存于土金山组中,主要矿石自然类型为泥质石膏和纤维石膏。希望为给地区寻找该类型石膏矿提供指导意义。     

山东省平邑左庄石膏矿区非采空致塌机理与治理方法

平邑左庄石膏矿区曾发生过3次地面塌陷,但井下实地调查发现,该矿区地面塌陷并非地下采空塌陷波及地表后而引发的地面塌陷。根据矿区地质环境条件、采矿方法及井巷工程布置等因素,分析认为地面塌陷原因是矿山布置的第一开采中段未预留出足够的顶柱厚度,致使井下回采时揭穿矿房顶柱接触到上覆第四纪松散盖层,第四纪孔隙水携带泥砂泄入矿坑发生潜蚀作用,在矿房顶柱与第四纪松散盖层之间形成"天窗式"砂漏,第四纪松散盖层中逐渐形成土洞,土洞扩大并塌陷后引发地面塌陷。     

西昆仑塔什库尔干地区老并石膏磁铁矿地质特征及成矿作用过程探讨

老并石膏磁铁矿位于塔阿西大断裂西侧,为一种新的矿床类型。笔者依据最新大调查、详查及勘探成果,通过矿区地质、矿床地质等方面综合分析研究,认为老并石膏磁铁矿成矿过程为海底火山活动带来了大量的炽热含盐和金属溶液,形成含矿溶液;含矿溶液在Eh、pH值差异的驱动下运移,并在特定的物理化学条件下,导致铁质的卸载沉淀,形成磁铁矿;同时由于炽热的含矿溶液与海水相互作用,为硬石膏的形成提供了S的物质来源,从而出现石膏、磁铁共生的现象。对于深化西昆仑地区磁铁矿成矿带成矿认识,总结区域成矿规律具有一定的理论意义和实践意义。     

南海神狐海域沉积物自生黄铁矿和石膏S同位素特征及对甲烷渗漏强度的示踪

The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor(cmbsf) in the entire core sediment of HS328 from the northern South China Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ~(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The relative high abundance and δ~(34) S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone(SMTZ).The sulfur isotopic composition of gypsum(from–25‰ to –20.7‰) is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The δ~(34) S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.     

滇西北兰坪盆地北部上三叠统含盐层位的厘定及其意义

通过野外实测剖面和大量室内岩矿工作,首次指出兰坪盆地上三叠统至少存在2套含盐层位,上含盐层位于三合洞组上段(T3s2),盐类物质以石膏、天青石为主,下含盐层位于三合洞组下段(T3s1),以天青石为主。天青石和石膏均呈中厚层层状产出,与顶底板地层产状一致。不同地区含盐层岩石组合及序列不同,横向上不具有可对比性,提出其并非正常蒸发沉积产物的认识。同时,含盐地层又是盆地内铅锌矿重要的赋矿层位,因此上三叠统含盐建造层序的厘定对深化认识区域铅锌矿床成矿机制、指导盐类矿床和铅锌矿找矿具有重要的意义。     

成都市近地表大气尘的矿物学特征及其环境指示意义

通过对成都市近地表大气尘X射线衍射、电镜扫描分析等研究显示:其主要由石英、长石、伊利石、绿泥石、方解石、石膏等矿物组成;就其形状看有致密的不规则粒状、片状单矿物、不规则粒状聚合体、浑圆形球状飘珠、聚合体放大观察可见片状的粘土矿物和细小的粒状单矿物,偶见藻类;矿物形貌特征及矿物组成空间分布特征的研究显示:球形状飘珠及伊利石、绿泥石、石膏的空间分布特征与工业布局和表层土壤的pH值密切相关,成都市近地表大气尘主要为地表扬尘和工业烟尘的混合物;与土壤的矿物组成比较可见,近地表大气尘重金属污染除土壤贡献外,还有其他污染贡献;石膏在本次研究中平均含量高达8.2%,推测可能成为成都市往年燃煤量大而无明显酸雨现象的原因之一。     

Diagenetic formation of gypsum and dolomite in a cold‐water coral mound in the Porcupine Seabight,off Ireland

Authigenic gypsum was found in a gravity core, retrieved from the top of Mound Perseverance, a giant cold‐water coral mound in the Porcupine Basin, off Ireland. The occurrence of gypsum in such an environment is intriguing, because gypsum, a classic evaporitic mineral, is undersaturated with respect to sea water. Sedimentological, petrographic and isotopic evidence point to diagenetic formation of the gypsum, tied to oxidation of sedimentary sulphide minerals (i.e. pyrite). This oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments. The oxidation of pyrite produced acidity, causing carbonate dissolution and subsequently leading to pore‐water oversaturation with respect to gypsum and dolomite. Calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21·6% and 28·6% of the sulphate incorporated into the gypsum derived from pyrite oxidation. The dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment‐water interface. Thus, authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate‐rich sediments. These observations demonstrate that fluid flow, steered by environmental factors, has an important effect on the diagenesis of coral mounds.     

酸碱滴定法测定天然石膏中碳酸盐的不确定度评定

对酸碱滴定法测定天然石膏中碳酸盐的结果进行不确定度评定。测量过程中的不确定度主要来源于样品制备过程引入的不确定度、滴定导致的不确定度、标定NaOH标准滴定溶液和HCl标准溶液引起的不确定度及重复性实验引起的不确定度等。合成各不确定度分量,并乘以扩展因子2得到扩展不确定度。对于CO₂平均含量为8.66%（质量分数）的天然石膏样品,其扩展不确定度为0.17%。     

利用石膏产状研究汶东盐湖相沉积与烃源岩特征

根据石膏矿物类型和产状以及其它相标志,对汶东凹陷汶ZK16 钻孔的古近系盐湖相地层进行了沉积相分析,并结合有机地球化学分析,对不同沉积相的烃源岩开展了地球化学评价。汶东凹陷石膏矿物组合较好的反映了古盐湖沉积环境、水深、盐度和底水含氧量等的变化,不同的石膏矿物组合对应着不同的沉积相和不同质量的烃源岩,其中干化泥坪相和盐化泥坪相石膏矿物组合以分散胶结状和结核状为主,其烃源岩有机质丰度较低,发育非烃源岩到差烃源岩;干盐湖相石膏矿物组合以肠状石膏和透镜状石膏为主,烃源岩有机质丰度较高,发育好到优质烃源岩;而深水盐湖相石膏矿物以纹层状石膏为主,烃源岩有机质丰度高,总体达到优质烃源岩的标准。据此,建立了盐湖相烃源岩的发育模式。该模式对于中国第三系盐湖烃源岩,特别是高演化程度的盐湖相烃源岩原始烃源岩类型研究具有重要的指导意义。