南京汤山上震旦统及古生界白云岩成因初探

本文通过对南京汤山上震旦统及古生界不同层位白云岩的岩石学特征，微量元素特征的研究提出了该区白云岩的五种成因机理，它们是原生－准同生白云石化模式，成岩早期混合水白云石化模式，成岩早期白云石化，成岩中晚期调整白云石化模式和构造热液白云石化模式。     

台湾甲仙地区早上新世冷泉白云岩的地质地球化学特征及沉积环境

白云石成因一直是地学中尚未解决的难题,海底冷泉系统中发育的原生白云石为解决白云石成因问题提供了新途径。台湾甲仙白云仙谷早上新世盐水坑组页岩地层中发育有冷泉白云岩,其流体来源和沉积环境并不清楚。本文通过矿物学和岩石学,结合碳氧同位素、微量和稀土元素地球化学,探索该冷泉白云岩的流体特征和形成环境,为解决白云石成因提供参考。白云仙谷冷泉白云岩以烟囱状或透镜状产出于页岩中,碳酸盐矿物均为泥微晶白云石,含量为61.4%～88.0%。冷泉白云岩的δ13C为-27.08‰～-10.58‰,指示形成白云石的碳源可能是热成因甲烷和海水的混合。Ni/Co均值为12.54,稀土元素配分模式呈中稀土富集、无Ce异常,均表明冷泉白云岩形成于弱还原的沉积环境。在弱还原环境中的冷泉微生物的作用下,促进了HCO3-的增加和SO42-的消耗,可能有利于冷泉白云石的形成。     

中扬子二叠系白云石化模式

中扬子二叠系发育局部白云石化和层状白云石化两种式,局部白云石化呈树枝状、斑块状见于不同层位之中,形成白云石化灰岩;层状白云石化分布稳定,形成层状白云岩。通过白云石化产状、X射线粉晶衍射特征、微量元素及稳定同位素特征的研究表明:局部白云石化为成岩期的调整白云石化模式,层状白云石化为同生——准同生期混合水白云石化模式。     

西沙岛礁白云岩化特征与成因模式分析

关于碳酸盐岩的白云岩化作用至今仍是一个争论颇大的科学问题。在2012-2013年期间,中海石油（中国）有限公司湛江分公司在西沙石岛钻取了长达1 268.02 m的“西科1井”岩心,在0~1 257.52 m主要由碳酸盐岩组成的岩心中存在有7个白云岩层。本文基于西科1井岩心样品的矿物组成、常量、微量及稀土元素含量等地球化学特征分析,探讨了西沙岛礁特有的白云岩化作用过程。结果表明:西科1井7层白云岩在成因上与埋深和压实成岩作用无关,其分布与海平面下降的地质事件有良好的对应关系,白云岩层元素地球化学特征表明白云岩成岩流体为浓缩的高盐度海水。根据白云岩层的矿物学和地球化学特征,提出了礁滩潟湖环境下高盐卤水渗透回流作用的白云岩化模式:伴随海平面的升降,礁体处于淹没与暴露的交替之中,海平面下降导致了礁滩潟湖的形成,由于西沙海区蒸发量大于降水量而使澙湖中海水盐度增高,最终形成富Mg卤水;澙湖中高盐度富Mg卤水在礁体内下渗和侧向扩散,Mg逐渐替代早期CaCO₃晶格中Ca而形成白云石;海平面的升降变化和礁体淹没与暴露的交替导致了钻井岩心多个白云岩层的形成。海平面升降直接控制了岛礁碳酸盐岩的发育和白云岩化作用,导致海平面升降的古气候变化在岛礁的形成发育中起到主导作用。     

西沙中新世藻礁白云岩储层特征及成因模式

西琛1井中新世生物礁被认为是植物藻礁白云岩,但为一孔之见。基于西沙群岛两大环礁3个岛屿的3口晚中新世—中中新世钻井生物礁全取心岩心的资料,开展藻礁白云岩的储层对比及成因模式分析,证实白云岩在各自埋深、厚度等方面虽不一致但特征较为相近,均处于中新世,多属藻礁白云岩,对于理解西沙群岛新近纪生物礁的形成演化具有重要意义。其中,涉及白云岩3层,总厚724.65m,通过常规岩石薄片、扫描电镜、X光粉晶衍射和物性测试分析发现,3口井的研究井段以藻礁白云岩为主,但深度不同;白云石矿物隐晶—粉晶—细晶状,发育粒间孔、藻架孔和生物体腔孔等原生孔隙和粒内溶孔、铸模孔、藻体溶孔及裂缝等次生孔隙;并在多个层段形成粒内溶孔—晶间孔—藻体溶孔组合;具有高孔、高渗显著特征,为有利油气储层。本段白云岩锶含量低,是新近纪全球冰川性海退事件的结果,构成混合水白云化作用机制。     

海南岛排浦现代白云岩若干特征及其岩化作用探讨

对我国首次发现的海南排浦现代白云岩的研究认为，该央发育于早更新世湛江组滨海相细一粉砂层之中，通过交代作用形成具雾心亮边结构的菱面体自形晶，矿物上属钙过剩的含铁白云岩，其形成过程可分为二个阶段：准同生渗透回流白云岩化作用阶段，成岩混合水白云岩化作用阶段，而后一阶段可能延续至今。     

西永2井中新统铁白云岩空间变异特征及成因

西沙群岛新近纪以来广泛发育生物礁白云岩,在西永2井白云岩层段发现大量的铁白云石,关于该区的铁白云石研究较少。笔者主要通过X射线粉晶衍射数据,结合前人研究资料,对西永2井407～570 m白云岩-铁白云岩进行了分析。研究发现西沙群岛西永2井中新统铁白云岩主要集中在上中新统黄流组一段,其黄流组二段主要发育含铁白云岩。白云岩孔隙度分布与其铁白云石分布有较好的对应关系,孔隙度高的层位铁白云石分布更密集。从中新统白云石和铁白云石的晶胞参数可以得知,该区铁白云石和白云石的晶胞参数都较大,呈现出富钙铁的特征。西永2井白云岩-铁白云岩有序度受Fe~(2+)的影响较大,Fe~(2+)的加入使其有序度降低,因此有序度低的现象不能简单的认为是结晶速度快的准同生作用造成。西沙群岛晚中新世有大量火山活动的现象,岩浆热液提供了铁白云石形成所需要的Fe~(2+)和热量来源。在成岩后期,孔隙性较好的黄流组一段受火山活动影响大,其热源及富Fe~(2+)离子促使白云石向铁白云石转变,形成了大量的铁白云石;而孔隙性较差的黄流二组仅仅形成大量的含铁白云岩。     

Fe同位素研究现状及其在西沙群岛铁白云岩研究中的应用

铁是地球中含量最多分布最广的过渡金属元素之一,但针对Fe同位素的研究滞后。介绍了开始于TIMS,到MC-ICP-MS的Fe同位素测试技术,其重要研究进展与现状。指出Fe元素及Fe同位素在自然界中的组成、分布及在生物、非生物有机作用过程中分馏的特征;Fe同位素地球化学及在古海洋学、矿床学等地球科学领域的广泛应用,涉及铁硫化物、铁氧化物和铁碳酸盐矿物-菱铁矿成矿作用。后者目前被认为是碳酸盐岩铁白云岩成因研究的关键,通过铁白云岩中大量铁和重金属来源示踪研究,揭示西沙群岛孤立岛屿环境铁白云岩的成因特征和机制,属于白云岩问题研究重要内容,具有重要的意义。     

南沙群岛南科1井白云岩发育特征及铁白云石成因机制的初步研究*

南海自新生代以来发育了大量的碳酸盐岩台地和生物礁, 并普遍发生白云岩化作用, 具有广阔的油气勘探前景。文章通过开展岩相学观察、矿物学分析、常微量元素和碳氧同位素分析, 同时结合Fe组分及Fe同位素地球化学分析, 对南沙群岛南科1井白云岩的发育特征和成岩环境进行了系统研究。结果表明: 南科1井上中新统—下更新统白云岩主要形成于近地表环境中, 溶蚀孔隙发育, 残余结构明显。白云岩层中发育有多个与暴露成因有关的界面, 未发现石膏层的存在。同时, 白云岩普遍具有低Fe、Mn和Sr的特征以及与现代海水相似的REE分布模式, δ¹³C和δ¹⁸O多为正值, 但不存在相关性。整体来看, 白云岩可能形成于轻微蒸发海水的渗透回流作用, 还受到了与古气候变冷有关的海平面下降的控制。此外, 南科1井岩芯中多个层位发育铁白云石, 并且集中分布在暴露面附近。Fe组分和Fe同位素组成结果显示, 白云岩中Fe主要来源于海水中碳酸盐的沉淀, 成岩过程中基本不存在额外的陆源或热液来源的Fe混入。铁白云石主要形成于低温和浅埋藏环境中, 大气淡水对生物骨架、生物碎屑以及自生碳酸盐矿物的淋滤-溶解作用为其提供了重要的物质来源。作为生物礁体暴露地表期间的产物, 铁白云石的发育层位可能指示着低海平面时期。     

渤海盆地JZ油田沙河街组白云岩成因分析

研究区以生屑白云岩及含砂屑的鲕粒白云岩为主,相邻井区白云岩类型及厚度变化大。为确定各类白云岩的成因,通过孢粉及微体古生物化石、碳氧同位素、微量元素B含量等分析手段,对本区的古气候、古环境、古沉积介质的物理化学性质进行系统地分析,自沙三段以来,由温暖的亚热带气候变得逐渐干燥,水体逐渐咸化,为白云岩的形成提供了必要条件。具有硬的基底的滨浅湖台地,水体能长期保持清澈,有利于底栖生物生长繁殖,适宜碳酸盐岩的形成、沉积了巨厚的生屑白云岩,其生屑含量高、孔隙较发育、方解石也被交代的更加彻底,建立了该类白云岩滨浅湖台地渗透回流成因模式。滨浅湖隆起带区域,淡水与咸水在此交汇,易形成具雾心亮边的粉晶白云岩和具有同心圆结构的鲕粒云岩或生物碎屑云岩,但常常白云石化不彻底,方解石含量高,个别井段甚至发育云质鲕粒灰岩,建立了该类白云岩滨浅湖隆起带混合水成因模式。此研究丰富了湖相白云岩成因模式,对渤海湾盆地碳酸盐岩的勘探具有重要的指导意义。     

海南岛排浦现代白云岩若干特征及其岩化作用探讨

对我国首次发现的海南排浦现代白云岩的研究认为，该岩发育于早更新世湛江组滨海相细—粉砂层之中，通过交代作用形成具雾心亮边结构的菱面体自形晶，矿物上属钙过剩的含铁白云岩，其形成过程可分为二个阶段：准同生渗透回流白云岩化作用阶段；成岩混合水白云岩化作用阶段，而后一阶段可能延续至今。     

断阶型潜山带地质模型的建立及储层预测--以CG20潜山为例

以 CG2 0潜山为例 ,从建立地质模型入手 ,包括地层模型、构造模型、储集模型、储盖组合模型、速度模型等 ,认识到各套地层分布和储层物性的差异均与地震响应密切相关 ,因此可以利用地震波的信息 ,预测潜山储层的发育及分布情况。在对 CG2 0潜山进行精细全三维构造解释的基础上 ,探讨性地应用了测井约束反演、吸收系数、相干分析及三维模式识别等技术 ,对潜山储层进行了预测 ,从而提高了潜山勘探的效益 ,并为类似断阶型潜山带的勘探提供了成功的经验 ,具有一定的指导意义。     

Reactivity of dolomitizing fluids and Mg source evaluation of fault-controlled dolomitization at the Benicàssim outcrop analogue (Maestrat basin,E Spain)

The mechanisms responsible for the formation of huge volumes of dolomitized rocks associated with faults are not well understood. We present a case study for high-temperature dolomitization of an Early Cretaceous (Aptian–Albian) ramp in Benicàssim (Maestrat basin, E Spain). In this area, seismic-scale fault-controlled stratabound dolostone bodies extend over several kilometres away from large-scale faults. This work aims at evaluating different Mg sources for dolomitization, estimating the reactivity of dolomitizing fluids at variable temperature and quantifying the required versus available fluid volumes to account for the Benicàssim dolostones. Field relationships, stable ¹³C and ¹⁸O isotopes, as well as radiogenic ⁸⁷Sr/⁸⁶Sr isotopes, indicate that dolomitization at Benicàssim was produced by a high-temperature fluid (>80 °C). ¹³C and ¹⁸O isotopic compositions for dolomite vary from +0.5 to +2.9‰ V-PDB and from +21.1 to +24.3 V-SMOW, respectively. A Mg source analysis reveals that the most likely dolomitizing fluid was seawater-derived brine that interacted with underlying Triassic red beds and the Paleozoic basement. Geochemical models suggest that evolved seawater can be considerably more reactive than high-salinity brines, and the maximum reactivity occurs at about 100 °C. Mass-balance calculations indicate that interstitial fluids with high pressure and/or high temperature relative to the normal geothermal gradient cannot account for the volume of dolomite at Benicàssim. Instead a pervasive fluid circulation mechanism, like thermal convection, is required to provide a sufficient volume of dolomitizing fluid, which most likely occurred during the Late Cretaceous post-rift stage of the Maestrat basin. This study illustrates the importance of fluid budget quantification to critically evaluate genetic models for dolomitization and other diagenetic processes.     

南海区域岩石圈的壳-幔耦合关系和纵向演化

南海区域岩石圈由地壳层和上地幔固结层两部分组成。具典型大洋型地壳结构的南海海盆区莫霍面深度为９～１３ｋｍ,并向四周经陆坡、陆架至陆区逐渐加深;陆缘区莫霍面一般为１５～２８ｋｍ,局部区段深达３０～３２ｋｍ,总体呈与水深变化反相关的梯度带;东南沿海莫霍面深约２８～３０ｋｍ,往西北方向逐渐增厚,最大逾３６ｋｍ。南海区域上地幔天然地震面波速度结构明显存在横向分块和纵向分层特征。岩石圈底界深度变化与地幔速度变化正相关;地幔岩石圈厚度与地壳厚度呈互补性变化,莫霍面和岩石圈底界呈立交桥式结构,具有陆区厚壳薄幔—洋区薄壳厚幔的岩石圈壳－幔耦合模式。南海区域白垩纪末以来的岩石圈演化主要表现为陆缘裂离—海底扩张—区域沉降的过程,现存的壳－幔耦合模式显然为岩石圈纵向演化产物,其过程大致可分为白垩纪末至中始新世的陆缘裂离、中始新世晚期至中新世早期的海底扩张和中新世晚期以来的区域沉降等三个阶段。     

Hydrothermal dolomitization in platform and basin carbonate successions during thrusting: A hydrocarbon reservoir analogue (Mesozoic of Venetian Southern Alps,Italy)

The Early Jurassic dolomitized carbonates in the Venetian Alp, represent a surface analogue of the hydrocarbon exploration targets in Adriatic offshore and Po Plain, Italy. Dolomitization affected the carbonate platform of Monte Zugna Formation (Lower Jurassic) and the Neptunian dikes breccia in the pelagic Maiolica Formation (Uppermost Jurassic–Lower Cretaceous) improving the poro-perm characteristics. Petrography, stable isotope, strontium isotope ratio, trace element and fluid inclusion analyses were carried out on samples from the Monte Grappa Anticline, which is the direct analogue for subsurface. The petrographic analyses showed a first pervasive, replacement dolomitization phase (D1) followed by volumetrically less important dolomite cement precipitation phases (D2, D3, DS). The same, quite wide range of oxygen isotope (?9 to ?2‰ V-PDB) is observed in all dolomite types. The δ¹³C range is in the positive field of marine derived carbonate (from +0.5 to +3.2‰ PDB). The trace element analysis showed a slight enrichment in Fe and Mn contents in the Monte Zugna dolostones with respect the original limestone. The same dolomite precipitation temperature (up to 105 °C Th) was observed in the replacement and cement dolomites, suggesting a unique dolomitization event. This temperature, largely higher than the maximum burial temperature (about 50 °C), supports a hydrothermal origin of the dolomitizing fluids, which had a seawater to brackish composition. The data collected suggest a hydrothermal dolomitization occurring during to the South Alpine thrusting according to the “squeegee model”. The interpretation is consistent with the dolomitization model proposed for similar Jurassic successions in the Central Southern Alps. This study indicates that the deformed foreland and thrust fold belts carbonates in Po Plain and Adriatic offshore are suitable to be dolomitized, and therefore reflect an efficient hydrocarbon exploration play.     

莱州湾南岸平原浅埋古河道带研究

菜州湾海岸平原在埋深６０ｍ内的浅埋古河道带,可分弥河、潍河和白浪河３个系统,它们大都呈掌状、放射状分布,并与其所属诉冲洪积扇范围相吻合,该区古河道的形成和发育是新构造运动和古气候环境演变的结果。自晚更新世晚期以来,该区有６期古河道发育,其中玉木早冰期古河道和玉木主冰期古河道的砂体沉积粒度粗、连通性好、分布广,即是富水性强、水质好的淡水含水层,又是该区海（咸）水入侵的主要通道,控制在线积粒度粗、连通     

Flow simulation with reactive transport applied to carbonate rock diagenesis

Significant volumes of the known hydrocarbon reserves are found in carbonate rocks, many of these dolomitized. The spatial distribution of diagenesis on these rocks is one of the main challenges in oil reservoir modeling. Reactive transport models can be a powerful tool to understand the active diagenetic processes and their effects on the quality of these reservoirs. In this study it was used, for the first time, the CMG-GEM simulator to model diagenetic evolution of a carbonate sequence, subjected to compaction-driven and geothermal flow in a simulated period of 200 thousand years. It was simulated carbonate cementation, dolomitization and dissolution, with and without presence of faults. Among the analyzed variables, the volume of circulating fluid was the most important factor. For both mechanisms, flow simulated velocities obtained had magnitudes smaller than 10⁻⁶ m/day. Diagenesis was insignificant for these low speeds at simulated time interval. Only dolomitized facies presented relevant diagenesis in form of calcite dissolution and dolomite precipitation. Simulations with flow rates of 1 m/day revealed a considerable increase in observed diagenesis, especially in carbonate cementation and in porosity enhancement. Diagenesis was more pronounced in more permeable sediments, highlighting the role of fluid flow in diagenetic reactions. Relative dissolution was greatly reduced during simulations performed with absence of dolomite and dolomitization reactions. The presence of faults strongly influences spatial distribution of diagenesis, especially relatively to dissolution. More permeable facies were more dissolved near fault, decreasing with increasing distance. Low permeability facies, as mudstones, are not dissolved, even near fault. Spatial distribution of diagenesis would then be dependent mainly on the quality of original pore structure, of fault presence and mineral composition of rock.     

南黄海盆地古潜山分类及构造特征

南黄海是下扬子的主体,奠基于晋宁期变质基底之上,构造演化历经南华纪—早、中三叠世海相地层发育期、晚白垩世—古近纪箕状断陷发育期和新近纪—第四纪坳陷发育期,为一典型地台-断陷-坳陷多层结构的复合盆地。盆地历经多次构造运动改造,古潜山发育,类型多样。在总结前人对古潜山研究的基础上,结合南黄海新近采集的二维地震剖面,对该地区古潜山类型进行了系统划分,并对典型古潜山的构造特征及生储盖匹配关系进行了初步描述。根据成因划分为剥蚀型潜山、拉张型潜山、挤压型潜山和复合型潜山四大类,每一类又可根据形态划分出剥蚀残丘型潜山、拉张翘倾断块型潜山、拉张断阶型潜山、拉张断垒型潜山、挤压褶皱型潜山、拱张褶皱型潜山和褶皱—断块复合型潜山等类型。南黄海盆地古潜山的发育具有分带性,按盆地中潜山的构造位置,分为凸起潜山带、陡坡潜山带、洼陷潜山带和缓坡潜山带,每一构造带发育了不同类型潜山。研究表明南黄海古生界和中生界古潜山数量众多,规模较大,是南黄海地区实现油气突破的一种重要油气藏类型。