白云母对岩盐断层带摩擦速度依赖性影响的实验研究

为更好地理解层状硅酸盐对断层强度、滑动速度依赖性及地震活动特征的影响,利用双轴摩擦实验对含白云母岩盐断层带在干燥及含水条件下摩擦的速度依赖性进行了实验研究,并观测了摩擦滑动过程中的声发射,分析了断层带的微观结构.实验结果表明,干燥条件下含白云母岩盐断层带在0.1 ～ 100μm/s的速度范围内表现为黏滑和速度弱化,增大σ2会使断层带从速度弱化向速度强化转化,速度依赖性转换出现在0.1 μm/s,其中断层滑动表现为稳滑或应力释放时间较长的黏滑事件;含水条件下含白云母岩盐断层带在0.05 ～0.01μm/s的速度范围内表现为速度强化,0.1 ～10μm/s的速度范围内表现为速度弱化,50～100μm/s的速度范围内又转换为速度强化行为.含白云母岩盐断层带在干燥条件下一次黏滑伴随一个或一丛声发射事件,而在含水条件下与稳滑相对应,滑动过程中并未记录到声发射事件.显微结构观察表明,速度弱化域的主要变形机制是岩盐颗粒的脆性破裂和局部化的滑动;干燥条件下,速度强化域的主要变形机制是岩盐颗粒的均匀破裂;含水条件下2个速度强化域对应不同的微观机制,高速域的速度强化受控于岩盐颗粒在白云母相互连结形成的网状结构上的滑动及其均匀碎裂作用,而低速域的速度强化还受岩盐的压溶作用控制.通过与岩盐断层带摩擦实验结果对比可知,白云母的存在对于燥岩盐断层带摩擦滑动方式和速度依赖性没有显著影响,而在含水条件下白云母的存在使得岩盐断层带滑动趋于稳定.实验结果为分析含层状硅酸盐断层的强度和稳定性提供了依据.此外,在速度依赖性转换域上观察到的应力缓慢释放的现象进一步证实了在岩盐断层带摩擦滑动过程中观察到的现象,这对慢地震机制研究具有参考意义.     

山东省泰安市大汶口盆地岩盐矿地质特征及开发意义

大汶口盆地岩盐矿均为第四系所覆盖,钻孔揭露,除第四系外,主要为古近系官庄群大汶口组。大汶口盆地主要是由南留断裂所控制。岩盐矿是大汶口盆地盐类矿床的主体,矿层多而集中,厚度大而变化小,品位高而稳定。矿层延展面积约45km3,其平面形态为一个椭圆形,在空间上整个含盐段似一个向北缓倾的大透镜体。矿石自然类型有3种,即块状岩盐（灰白盐）、含杂质岩盐（杂色盐）和脉状岩盐,其中以块状岩盐为主,含杂质岩盐次之,脉状岩盐不具有工业意义。该矿床地质条件好、埋藏深度适宜,外部建设条件好,该矿床具备大规模开发的条件,矿业开发可促进当地的经济发展.当地政府有关部门已在着手工作,推动该岩盐矿规模开发进程。     

Origin and geochemistry of Miocene marine evaporites associated with red beds: Great Kavir Basin,Central Iran

During the Cenozoic numerous shallow epicontinental evaporite basins formed due to tectonic movements in the Northern Province of the Central Iran Tectonic Zone (the Great Kavir Basin). During the Miocene, due to sea‐level fluctuations, thick sequences of evaporites and carbonates accumulated in these basins that subsequently were overlain by continental red beds. Development of halite evaporites with substantial thickness in this area implies inflow of seawater along the narrow continental rift axis. The early ocean basin development was initiated in Early Eocene time and continued up to the Middle Miocene in the isolated failed rift arms. Competition between marine and non‐marine environments, at the edge of the encroaching sea, produced several sequences of both abrupt and gradual transition from continental wadi sediments to marginal marine evaporites in the studied area. These evaporites show well‐preserved textures indicative of relatively shallow‐brine pools. The high Br content of these evaporites indicates marine‐derived parent brines that were under the sporadic influence of freshening by meteoric water or replenishing seawater. However, the association of hopper and cornet textures denotes stratified brine that filled a relatively large pool and prevented rapid variations in the Br profile. Unstable basin conditions that triggered modification of parent brine chemistry prevailed in this basin and caused variable distribution patterns for different elements in the chloride units. The presence of sylvite and the absence of Mg‐sulphate/chlorides in the paragenetic sequence indicate SO₄−depleted parent brine in the studied sequence. Petrographic examinations along with geochemical analyses on these potash‐bearing halites reveal parental brines which were a mixture of seawater and CaCl₂‐rich brines. The source of CaCl₂‐rich brines is ascribed to the presence of local rift systems in the Great Kavir Basin up to the end of the Early Miocene. Copyright © 2007 John Wiley & Sons, Ltd.     

东濮凹陷文留油田盐岩地震反射特征及相关油藏类型

利用地震资料, 结合地质、钻井资料, 对东濮凹陷文留地区盐岩的物理性质、地震反射特征、几何形态、与盐岩相关油气藏的类型进行了研究。发现盐岩具有密度恒定特性(低密度)和速度稳定特性(高速度), 基本不随深度变化。盐岩与砂泥岩体之间有较强的波阻抗差, 因而其界面反射特征明显。但盐岩的流动特性造成盐岩体有多种赋存状态, 它们的地震反射特征各不相同, 这是盐岩解释的主要困难。利用地震资料识别归纳出盐层(体)解释判定模式, 认为本区盐岩主要有3种赋存状态:原生板状盐岩、后生变形盐岩和次生盐墙。盐岩流动变形及相变形成了3类油气藏:盐上堑式背斜油气藏、盐侧向封堵油气藏和盐下盐背斜油气藏。      

Deciphering some unique paleotemperature indicators in halite-bearing saline lake deposits from Death Valley, California, USA

Saline lake deposits are arguably the best source of mid- to low-latitude terrestrial paleoclimate data. Alternating clastic sediments and evaporites of different chemical composition have long been recognized as sensitive records of changes in inflow and aridity related to a variety of climate parameters. Several sources of paleotemperature information from a halite-bearing saline lake deposit are described here – pseudomorphs of a cold-temperature evaporite mineral, homogenization temperatures of fluid inclusions in halite, and stable-isotope compositions of fluid inclusions in halite. Examples of these paleoclimate data come from analysis of the lower half of a 185-m core drilled in Pleistocene saline lake deposits at Death Valley, California. Daily and seasonal temperature variations in saline lake waters create conditions for the appearance and disappearance of temperature-dependent mineral phases. In the Death Valley core, hexagonal-shaped halite crystals, probable pseudomorphs of the cold-temperature hydrous mineral, hydrohalite (NaCl2H₂O), provide evidence of brine temperatures below about 0 °C. Homogenization temperatures of fluid inclusions in primary halite offer an actual (not proxy) record of surface-brine temperatures. Samples with primary fluid-inclusion textures are carefully selected and handled, and data are collected from single-phase aqueous-brine inclusions chilled to nucleate vapor bubbles. Temperature variations are observable at scales of individual halite crystals (hours to days), single halite beds (weeks to months or years), and multiples of beds to entire facies (hundreds to tens of thousands of years). A ¹⁸O/D stable isotope record from the minute quantities of brines in fluid inclusions in halite is accessible using a method recently developed at the University of Calgary. The stable isotope record from the Death Valley core, a complex response to climate variables including temperature, humidity, storm patterns or seasons, and inflow sources, compliments and expands the interpretation emerging from the stratigraphy and homogenization temperatures.     

柴达木西部钻孔盐类矿物及环境意义初步研究

柴达木盆地位于青藏高原北部,沉积和储存了巨量的蒸发岩。其独特的地理位置、构造特征、盐类沉积和其它资源优势,成为地学领域各方向学者关注的焦点。2008年,中德合作在盆地西部取得千米深的钻孔,上部400 m表现为碳酸盐粘土层与盐层的交替,盐层的矿物种类是石盐（NaCl）,石膏（CaSO4·2H2O）,芒硝（Na2SO4·10H2O）,无水芒硝（Na2SO4）,钙芒硝（Na2Ca(SO4)2）,杂卤石（K2MgCa2(SO4)4·2H2O）,尤钠钙矾（Na4Ca(SO4)3·2H2O）和白钠镁矾（Na2Mg(SO4)2·4H2O）,以石盐和石膏为主。碳酸盐粘土层中还出现了少量重晶石（BaSO4）、碳酸钠钙石（Ca2Na2(CO3)3）、钠钙矾（Ca2Na3(SO4)3(OH)）、苏打石（NaHCO3）、斜碳钠钙石（Na2Ca(CO3)2·5H2O）、一水碳酸钠（Na2CO3·H2O）和水硼镁石（CaMg(B3O3(OH)5)2·6H2O）。碳酸盐粘土层中不同形态的石膏单晶、双晶和集合体,形成于次生浓卤水溶液,晶体形状与生长速度、溶液性质和环境条件有关。单盐矿物石盐、石膏和无水芒硝从卤水中直接结晶,复盐钙芒硝、白钠镁矾和尤钠钙矾则由单盐反应形成。尤钠钙矾为罕见的亚稳定矿物,柴达木盆地和青藏高原其它地区的研究中尚未见报道,该矿物形成温度远高于室温,可能是由石膏或无水芒硝在富Na SO4卤水溶液中反应形成。根据矿物种类、组合和阳离子含量推断,古卤水类型主要为Na Cl型,其次为Na Ca SO4、Na SO4、Na SO4 Cl、Na Ca SO4 Cl,少数层位为Ca SO4和Na Mg SO4型卤水。盐层和碳酸盐粘土层的交替说明,1 Ma以来钻孔所在区域为干湿交替气候,18个成盐阶段或气候干旱阶段出现在0.97~0.03 Ma,最早的两个蒸发阶段为0.96~0.97 Ma和0.87 Ma,其它蒸发阶段出现在0.78~0.03 Ma,厚盐层集中出现在0.5~0.03 Ma。     

库车坳陷第三系盐膏质盖层特征及其对油气成藏的控制作用

库车坳陷的第三系盐膏质区域盖层具有厚度大、分布广、岩性致密、突破压力高、地层压力也很高的特点,属于封闭性特别强的区域盖层;在坳陷的成藏系统中,起着应变分隔带、流体压力屏障、油气成藏机制分界线的作用;在其上下出现了两种成藏模式-克拉苏模式和大宛齐模式。这套盖层是坳陷油气富集的最重要条件之一,也是我国最优良气田-克拉2大气田形成的最重要条件之一。在其下还会有更多的克拉2型的气田存在。     

洪泽凹陷赵集次凹阜宁组四段盐岩深水再沉积成因探讨

为了查明洪泽凹陷赵集次凹阜四段盐岩成因,利用录井、测井、古生物和地球化学资料,对苏北盆地洪泽凹陷赵集次凹古新统阜宁组四段(E₁f₄)的盐岩沉积特征进行了分析,发现阜四段含盐系地层主要发育石盐岩,硫酸盐岩次之,还有少量碳酸盐岩。石盐岩单层厚度大,纯度高,横向分布稳定。对比研究认为赵集次凹E₁f₄盐岩应为淮安凸起上白垩统浦口组(K₂p)盐岩经溶解搬运至洪泽凹陷赵集次凹深水湖盆中,使盐度过饱和后再沉积成因。赵集次凹E₁f₄比淮安凸起K₂p石盐岩矿层纯度高;盐岩洁净、盐间夹灰-深灰色泥岩,未见浅水蒸发构造;生物化石以陆相介形类为主,淡水滨浅湖的腹足类和轮藻化石稀少,在E₁f₄地层中存在仅见于K₂p地层中的Cicat ricosisporites pseudoanrifer化石以及Welwitschiapitesningensis、Cicatricosisporites pseudoaurifer等;两地盐岩的卤水类型均为硫酸盐-氯化物型,而赵集次凹E₁f₄盐岩重金属元素含量较低。赵集次凹阜四段存在两个主要成盐期:上盐亚段与下盐亚段,对比研究发现二者的盐岩类型、特征及成盐序列有较大差异,尝试根据盐类物质供给的成分和速率的不同建立了相应的成盐模式:下盐亚段为深水近源快速补给"石盐岩-无水芒硝岩-石盐岩再沉积"成盐模式;上盐亚段为深水近源缓慢补给"钙芒硝岩-石盐岩再沉积"成盐模式。     

塔里木盆地塔中隆起盐相关断裂发育特征

根据地震资料解释成果,结合中、下寒武统含盐层系展布特征,分析塔里木盆地塔中隆起主要断裂带变形特征及其形成机理.塔中隆起主要断裂带表现为上陡下缓,往深部在中、下寒武统含盐层系顶在或内部发生滑脱,滑脱距离在不同地区有所差异,具有典型的"盐相关断裂"特征.塔中地区断裂带的形成演化主要受区域构造应力场、基底先存断裂和中、下寒武...     

Fluid Inclusions in Surface‐temperature Halite: Sample Preparation and Application

Paleo-temperature and paleo-environment can be interpreted from measuring homogenization temperatures of fluid inclusions within halite. In order to conduct such measurements, vapor bubbles within low-temperature fluid inclusion often need to be created through cooling process by using cooling stage or freezer. Proper cooling is critical for interpreting measured temperature data. We tested two common cooling methods, using heating/freezing stage and freezer, for studying fluid inclusions in halite precipitated in laboratory at conrtolled temperature of 25℃. While using the heating/freezing stage, halite samples were kept at-18℃ for 40–50 min; whereas for freezer, samples were stored at-18℃ for 1, 10, 20 and 40 days, respectively. By comparing the homogenization temperatures of the two cooling processes, we explored the detailed experimental processes and developed an optimal cooling nucleation procedure for homogenization temperature analyses of fluid inclusions within surface-temperature halite. The results show that the maximum homogenization temperatures from both methods approximate the actual brine temperature of 25℃. However, extended refrigeration time has noticeable influence on the results. The refrigeration time of the experiment can be shortened to meet requirements.