沉积地层中成矿作用的碳同位素特征和含矿缺氧盆地成因新观点

沉积盆地内地层中碳的来源,根据其碳,氧同位素特征可归纳为：海洋沉积碳酸盐碳,生物碳,热解非生物成因碳,大气淡水方解石碳和热卤水系统中的无机碳。热水成因的金矿及喷气－沉积矿床中的碳都具有深源成因的无机碳。深部含无机碳的热流体喷溢到海洋底部可以解释为扩张盆地底部形成的缺氧环境和含矿黑色页岩的主导原因。     

沉积地层中成矿作用的碳同位素特征和含矿缺氧盆地成因新观点

沉积盆地内地层中碳的来源 ,根据其碳、氧同位素特征可归纳为 :海洋沉积碳酸盐碳、生物碳、热解非生物成因碳、大气淡水方解石碳和热卤水系统中的无机碳。热水成因的金矿及喷气 沉积矿床中的碳都具有深源成因的无机碳。深部含无机碳的热流体喷溢到海洋底部可以解释为扩张盆地底部形成的缺氧环境和含矿黑色页岩的主导原因     

陆相盆地主要沉积微相的测井特征

通过研究自然电位和视电阻率曲线的响应特征,将我国陆相盆地的3个陆相组：冲积相组、过渡相组、湖泊相组,进一步划分出27个沉积微相。并论述了它们的测井曲线特征,建立了测井沉积微相模式。它们具有在自然电位曲线和视电阻率曲线上的可识别特征。测井沉积微相模式为陆相盆地沉积学和定量测井沉积学的深入研究可提供一个参考模式。     

沁水煤层气田高阶煤解吸气碳同位素分馏特征及其意义

沁水盆地是我国煤层气勘探开发的重要有利区,沁水煤层气田位于盆地东南部。对采自沁水煤层气田两口井的煤开展了罐解吸实验。结果表明,该地区煤层气解吸速率很快,96 h后解吸气量都达到了总解吸气量的60%~85%,720 h后解吸过程基本结束;解吸气量大,平均在18 m3/t以上。煤层气解吸过程中甲烷发生碳同位素分馏,δ13C1值变化与解吸率呈良好的线性关系,参考这种正相关关系曲线,定期监视煤层气降压排采过程中甲烷δ13C1值的变化情况,可以大致推测出该地区煤层气解吸率,从而预测煤层气的采出程度。跟踪测试沁水煤层气田A1和A1-3井在试采过程的甲烷δ13C1变化情况,推测现在采出的煤层气可能主要是煤层裂隙中以游离形式存在的煤层气,表明该区煤层气稳产性较好,资源前景广阔。     

沉积盆地物质来源综合研究——以南堡老第三纪亚断陷盆地为例

重矿物分析对于判断沉积盆地的物源方向和物源区的母岩性质是有效的,但具有局限性:①对无重矿物或者仅能提供极少量重矿物的母岩判别力较差;②它不能准确判断物源区沉积物的主要运移通道。因此,进行盆地物源分析还需要重视综合研究,即①通过重矿物的矿物学、重矿物组合研究,判断物源区的母岩类型,推测母岩岩性演化;②通过沉积岩矿物成分与结构研究,判别物源区是否存在重矿物无法辨认的母岩类型和沉积物的搬运距离;③通过沉积体系分析,尤其是砂分散体系的编图,能有效地判断物源区的方位和圈定各物源的具体影响范围;④利用古构造图判别物源区的主要沉积物运移通道及其方位;⑤编制沉积盆地一物源区古环境图,以此来弥补重矿物分析物源所带来的缺陷。     

海相干酪根与原油裂解气甲烷生成及碳同位素分馏的差异研究

利用封闭金管高压釜体系对海相原油和成熟干酪根进行了热解生气实验,获取了两类裂解气的组分和甲烷碳同位素数据,对比研究了两类母质在生气机理上的差异,并借助碳同位素分馏动力学参数讨论了甲烷碳同位素分馏的异同点.结果表明,原油裂解气富含C2-5重烃,其后期裂解是甲烷的重要来源;而干酪根裂解气中C2-5的含量较低,其后期裂解对干酪根甲烷气的贡献较小.这是两类甲烷气体生成的最大差异之一.两类裂解气甲烷碳同位素都有随着热解温度增高,碳同位素值先变轻再变重的特点,但原油裂解气甲烷碳同位素的最小值对应的温度较高;在相同热解温度下,干酪根裂解气甲烷碳同位素值要重于原油裂解气甲烷碳同位素值,这与后者前系物经过多次碳同位素分馏有关.因此,生气机理的差异是造成同位素分馏差异的根本原因,两类甲烷气体碳同位素分馏动力学参数的差异也是有成因意义的.     

沉积盆地卤水来源的非传统同位素示踪研究进展

世界上大多数的沉积盆地内,在结晶基底或者沉积地层内都有矿化度较高的卤水,由于这些卤水通常携带或富含有钾、硼、锂、溴、碘、铷、铯、稀有气体及重金属元素,因此,它们是地学界的研究热点之一。随着测试技术的不断进步,非传统同位素的应用也日益广泛,但在沉积盆地卤水来源和演化方面的研究还十分薄弱,对卤水的来源和演化也还存在争议。文章回顾了硼、锂、碘和惰性气体氦、氩同位素在卤水来源研究方面的进展,并指出由于单一同位素在解释上的片面性,多种同位素相结合的示踪方法研究沉积盆地卤水的来源是国际趋势。     

西太平洋中段沉积盆地新生代构造-沉积演化特征*

西太平洋中段位于欧亚板块、太平洋板块和印度洋板块的交汇处,是全球沟弧盆体系最为发育的地区,主要发育弧后盆地、弧前盆地和陆架边缘盆地。文中通过综合研究西太平洋中段17个盆地的大地构造背景、盆地的形成与演化和沉积特征后认为:(1)各类盆地的构造-沉积演化均经历4个期次。弧前盆地和弧后盆地的构造-沉积演化可分为俯冲期(K₂-E)、盆地发育期((Ｎ_１^１ -Ｎ_１³)、沉降期(Ｎ_１⁴-Ｎ_１⁵)和挤压期(N₂-Q):俯冲期发育火山岩和变质岩基底,局部为海相碎屑岩;盆地发育期以海相沉积为主,伴有火山活动,局部发育陆相沉积;沉降期以海相和三角洲相沉积为主;挤压期以三角洲相和海相沉积为主,局部发育河湖相沉积。陆架边缘盆地的构造-沉积演化也分为4期,分别为前裂陷期(K₂-E₁)、裂陷期(E₂-(E₃^１)、拗陷期(E₃²-Ｎ_１³)和沉降期(Ｎ_１⁴-Q):前裂陷期和裂陷期主要发育冲积扇—河流—湖泊沉积体系,火山活动强烈;拗陷期沉积环境由陆相向海陆过渡相演化;沉降期以海相和海陆过渡相沉积为主。(2)不同类型盆地的构造-沉积演化特征各不相同:弧前盆地构造以挤压和板块俯冲为主,平均沉积厚度为3.6,km,总体由海陆过渡相向陆相演化;弧后盆地构造受板块俯冲后撤和弧后洋壳扩张作用控制,平均沉积厚度为4.8,km,总体由海相向海陆过渡相演化;陆架边缘盆地构造呈下断上拗双层结构,平均沉积厚度超过10,km,总体由陆相演化为海相。     

煤层气甲烷碳同位素的分布特征与控制因素

研究表明 ,在相同热演化程度条件下 ,除少量样品外 ,煤层气δ13 C1值一般较煤型气偏轻。影响煤层气甲烷碳同位素变轻的因素相当复杂。母质类型、成熟度、解吸扩散及运移效应、次生生物气的混入以及CO2 和CH4之间的同位素交换反应等都是影响煤层气甲烷碳同位素组成与分布的重要因素。     

与火山岩容矿有关的海底热水沉积矿床硫同位素地球化学证据

对国内与火山岩容矿有关的海底热水沉积矿床新疆阿巴宫、铁-铅锌矿、甘肃桦树沟铁-铜矿床、新疆阿舍勒铜锌矿、新疆阿尔泰可可塔勒铅锌矿等矿床硫化物进行硫同位素测定,这些矿床硫化物和硫酸盐的硫同位素组成分别为-4.3‰~1‰(阿巴宫)、+8.1‰~+33.4‰(桦树沟)、-3.3‰~+8.2‰(阿舍勒矿床硫化物)、-20.6‰~5.1‰(阿尔泰可可塔勒)。硫化物的硫同位素变化范围较小,硫同位素可以达到平衡,也可以没有达到平衡,获得的δ34SΣS值有+18‰~29‰之间,δ34SΣS值高;表明与火山岩控矿有关的海底热水沉积矿床热液中硫的来源,不是直接来源岩浆去气的硫,而是岩浆去气硫与海水硫酸盐硫混合而成的硫。     

Cretaceous sedimentary basins in Sichuan,SW China: Restoration of tectonic and depositional environments

This study documents sediment infill features and their responses to the tectonic evolution of the Sichuan Basin and adjacent areas. The data include a comparison of field outcrops, well drillings, inter-well correlations, seismic data, isopach maps, and the spatial evolution of sedimentary facies. We divided the evolutionary history of the Sichuan Cretaceous Basin into three stages based on the following tectonic subsidence curves: the early Early Cretaceous (145–125 Ma), late Early Cretaceous to early Late Cretaceous (125–89.8 Ma), and late Late Cretaceous (89.8–66 Ma). The basin underwent NW–SE compression with northwestward shortening in the early Early Cretaceous and was dominated by alluvial fans and fluviolacustrine sedimentary systems. The central and northern areas of the Sichuan Basin were rapidly uplifted during the late Early Cretaceous to early Late Cretaceous with southwestward tilting, which resulted in the formation of a depression, exhibited southwestward compression, and was characterized by aeolian desert and fluviolacustrine deposits. The tectonic framework is controlled by the inherited basement structure and the formation of NE mountains, which not only affected the clastic supply of the sedimentary basin but also blocked warm-wet currents from the southeast, which changed the climatic conditions in the late Late Cretaceous. The formation and evolution of Cretaceous sedimentary basins are closely related to synchronous subtle far-field tectonism and changes in climate and drainage systems. According to the analysis of the migration of the Cretaceous sedimentation centers, different basin structures formed during different periods, including periods of peripheral mountain asynchronous thrusting and regional differential uplift. Thus, the Sichuan Cretaceous sedimentary basin is recognized as a superimposed foreland basin.     

青藏高原中东部早期构造隆升对古近纪盆地充填和演化的影响

青藏高原中东部分布着一系列中小型古近纪断陷盆地和走滑-拉分盆地。印度-欧亚板块碰撞已引起盆地构造、沉积和岩浆活动等地质事件的响应。古近纪断陷盆地和走滑-拉分盆地中广泛分布的巨厚粗碎屑岩充填、新特提斯海湾消亡、大规模地壳挤压褶皱冲断和高钾岩浆活动、周缘前陆盆地形成、干旱-温暖极热事件以及古近纪盆地的封闭和裂解等。详细的野外地质调查、盆地构造-沉积学、生物地层学和岩浆岩同位素年代学研究结果表明,北部玉树-囊谦地区断陷盆地发生了大规模挤压掀斜和冲断,在盆缘形成高陡地层和挤压向斜,盆地内地层发生明显的褶皱变形。盆地内部充填了巨厚层状底砾岩、紫红色陆源碎屑岩夹火山碎屑岩、碳酸盐岩和石膏层,并被晚期岩浆岩所切割。南部巴塘-丽江地区形成走滑-拉分盆地。区域地层对比、细碎屑岩内孢粉和古植物、火山碎屑岩和侵入岩的U- Pb和40Ar/39Ar年代学结果表明,盆地内充填沉积物形成于始新世(56~32 Ma)。古近纪紫红色细粒沉积物、碳酸盐岩和石膏层的出现表明盆地封闭期处于干旱-炎热的古气候环境。38~32 Ma是自印度-欧亚板块陆-陆碰撞以来,青藏高原中东部从转换挤压到转换伸展的过渡阶段,出现了大规模高钾火山喷发和随后的岩浆侵入,并导致青藏高原中东部古近纪盆地的封闭和裂解。北部盆地的封闭时间(约37 Ma)早于南部盆地的裂解(约32~28 Ma)。青藏高原中东部古近纪盆地的封闭和裂解主要是自约38 Ma以来,印度-欧亚板块碰撞引起的陆壳挤压、变形和缩短,及由高原早期构造隆升诱导的逆冲挤压和走滑拉分引起的。     

Prediction of hydrocarbons in sedimentary basins

To estimate the undiscovered hydrocarbon potential of sedimentary basins, quantitative play assessments specific for each location in a region may be obtained using geostatistical methods combined with the theory of classification of geological objects, a methodology referred to as regionalization. The technique relies on process modeling and measured borehole data as well as probabilistic methods to exploit the relationship between geology (the predictor) and known hydrocarbon productivity (the target) to define prospective stratigraphic intervals within a basin. It is demonstrated in case studies from the oil-producing region of the western Kansas Pennsylvanian Shelf and the gas-bearing Rotliegend sediments of the Northeast German Basin.     

Compaction process in sedimentary basins: the role of stiffness increase and hardening induced by large plastic strains

This paper is devoted to the simulation of large strain compaction process in sedimentary basins. Special attention is paid to the effects of large porosity changes on the elastic and plastic mechanical properties of the sediment material. The latter are introduced in the constitutive behaviour in the framework of a micromechanical reasoning. In particular, the proposed approach avoids the problem of negative porosities that are predicted by classical models under high confining pressures. Some closed‐form solutions are presented in the simplified case of one‐dimensional compaction. While the influence of stiffness increase is shown to be negligible as regards the compaction law, it proves to affect significantly the stress and porosity profiles. Copyright © 2004 John Wiley & Sons, Ltd.     

Enrichment of nitrogen and 13C of methane in natural gases from the Khuff Formation,Saudi Arabia,caused by thermochemical sulfate reduction

Permian Khuff reservoirs along the east coast of Saudi Arabia and in the Arabian Gulf produce dry sour gas with highly variable nitrogen concentrations. Rough correlations between N₂/CH₄, CO₂/CH₄ and H₂S/CH₄ suggest that non-hydrocarbon gas abundances are controlled by thermochemical sulfate reduction (TSR). In Khuff gases judged to be unaltered by TSR, methane δ¹³C generally falls between −40‰ and −35‰ VPDB and carbon dioxide δ¹³C between −3‰ and 0‰ VPDB. As H₂S/CH₄ increases, methane δ¹³C increases to as much as −3‰ and carbon dioxide δ¹³C decreases to as little as −28‰. These changes are interpreted to reflect the oxidation of methane to carbon dioxide.Khuff reservoir temperatures, which locally exceed 150 °C, appear high enough to drive the reduction of sulfate by methane. Anhydrite is abundant in the Khuff and fine grained nodules are commonly rimmed with secondary calcite cement. Some cores contain abundant pyrite, sphalerite and galena. Assuming that nitrogen is inert, loss of methane by TSR should increase N₂/CH₄ of the residual gas and leave δ¹⁵N unaltered. δ¹⁵N of Paleozoic gases in Saudi Arabia varies from −7‰ to 1‰ vs. air and supports the TSR hypothesis. N₂/CH₄ in gases from stacked Khuff reservoirs varies by a factor of 19 yet the variation in δ¹⁵N (0.3–0.5‰) is trivial.Because the relative abundance of hydrogen sulfide is not a fully reliable extent of reaction parameter, we have attempted to assess the extent of TSR using plots of methane δ¹³C versus log(N₂/CH₄). Observed variations in these parameters can be fitted using simple Rayleigh models with kinetic carbon isotope fractionation factors between 0.98 and 0.99. We calculate that TSR may have destroyed more than 90% of the original methane charge in the most extreme instance. The possibility that methane may be completely destroyed by TSR has important implications for deep gas exploration and the origin of gases rich in nitrogen as well as hydrogen sulfide.     

Geodynamics of the Early Precambrian,Part 2: Formation of continental crust and sedimentary basins,specificity of the lithosphere

This part of work is aimed at consideration of problems concerning evolution of geodynamic processes based on characteristic structures of the Early Precambrian and their rocks. Considered in the paper are structures characterizing existence of mature continental crust (sedimentary basins), development of the crust (metamorphic belts and granitoids) and underlying upper mantle (lithospheric keel), and amalgamation of crustal domains (continents, microcontinents, terrains) into supercontinents. Geodynamic phenomena of the Early Precambrian comparable with the Phanerozoic ones are distinguishable, on the one hand, and their changes with time of evolutionary character are detectable, on the other. The latter are satisfactorily explainable by secular lowering of the mantle temperature in general and above the top of mantle plumes.     

大陆岩石圈挠曲背景下盆山耦合研究进展与展望

盆山耦合研究在大地构造和地球动力学研究中占有重要地位。地貌负载引起的大陆岩石圈挠曲与沉积盆地沉降是盆山耦合的一种重要体现方式。本论文聚焦于挤压背景下大陆岩石圈挠曲盆地与造山带的耦合过程,系统梳理了单个或者多个地貌负载的几何形态、挠曲盆地几何形态以及岩石圈有效弹性厚度(T_e)三者之间的数学关系。在此基础上,论文介绍了岩石圈挠曲模拟方法在恢复岩石圈刚性程度、造山带演化过程以及盆地沉积沉降方面的具体应用。结合古环境分析与岩石圈挠曲模拟实验,本文提出了一种定量恢复造山带古海拔的新方法。有别于基于温度、压力以及动植物分布与海拔之间关系所建立的传统古高度计,该方法强调在海侵时期地貌负载与沉积盆地间的高度差即为造山带的古海拔。该方法的提出为重建中亚以及其他曾受海侵影响并与岩石圈挠曲相关造山带的古海拔提供了新的思路。论文最后介绍了岩石圈挠曲模拟在定量分析造山带与盆地演化的研究过程中存在的问题与不足,并提出了在探究沉积盆地基底属性、重建岩石圈挠曲相关造山带古海拔以及有关挠曲模拟软件开发方面的新展望。     

Evidence for anisotropy in the super-thick sedimentary basin,Bay of Bengal

Evidence for anisotropy in the super-thick sedimentary basin under the northern Bay of Bengal is presented. Surface wave group velocity data given by Brune and Singh (1986) is better fit by an anisotropic model than an isotropic one. This lends support to the hypothesis that the mid-crustal rocks are metasediments and that the section of sediments and metasediments is more than 20 km thick.     

保德地区煤层气地球化学特征及成因探讨

为了查明保德地区煤层气地球化学特征及成因,采集煤样、煤层气样及水样,开展气体组分分析、煤层气井产出水水质检测和稳定同位素分析。结果表明：煤层气组成中烃类气体以CH₄为主,体积分数为88.60%~97.59%;含有少量乙烷,体积分数仅为0.01%~0.14%;干燥系数均大于0.99,属于极干煤层气。非烃类组分中,主要含有CO₂和N₂,其中,CO₂体积分数为1.74%~7.61%,N₂体积分数为0.04%~8.18%。煤层气δ¹³C(CH₄)值为–56.8‰~–47.7‰,δ¹³C(CO₂)值为–6.6‰~13.9‰,δD(CH₄)值为–252.6‰~–241.6‰。煤层产出水呈弱碱性,属于NaHCO₃类型水,与地表水离子构成、矿化度、δD(H₂O)和δ¹⁸O(H₂O)值均相近,有地表水的补给,有利于产CH₄菌大量繁殖,生成次生生物气。综合认为,研究区煤层气为热成因气和生物气的混合气,生物成因气主要是通过二氧化碳还原作用形成,受煤层解吸–扩散–运移作用、水溶作用和次生生物作用导致煤层气“变轻”。研究成果为后续煤层气勘探开发提供指导。     

黑龙江省东部残留盆地群早白垩世沉积相特征及演化

黑龙江省东部残留盆地群早白垩世主要充填滴道组（裴德组）、城子河组（七虎林组和云山组）、穆棱组（珠山组）和东山组。沉积相以冲积扇相、（扇）三角洲相、湖泊相、海相等为主。沉积相研究结果表明,滴道组以冲积扇及（扇）三角洲粗碎屑沉积为主,并伴随有火山岩分布,反映了盆地初始裂陷阶段的沉积环境特点;城子河组和穆棱组沉积时期,三江地区处于整体下沉阶段,现今残留的三江盆地、勃利盆地、鸡西盆地、虎林盆地、宁安盆地、鹤岗盆地和汤原断陷等为统一的近海拗陷盆地,张广才岭-小兴安岭及东三江和完达山地区是盆地主要物源供给区,平面上构成（扇）三角洲-滨浅湖-半深湖-湖底扇的沉积格局,并且伴随有多次海侵事件,海侵方向主要来自虎林盆地东部及绥滨坳陷北部;东山组沉积时期,盆地已明显萎缩,发育局限的（扇）三角洲-滨浅湖相沉积。