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1.
The chemistry of the waters from which the evaporitic minerals crystallized in the lower part of the Salt IV unit of the Mulhouse Basin (France) has been investigated. The lithological and fluid inclusion data have been compared to the output data of the mass transfer program NEWEQUI which simulates the change in brine composition during its evaporation advancement. The results show that the evolution of the composition of the brine is compatible with the calculated sequence of evaporation of a parent water corresponding to a seawater modified by CaCl2-rich hydrothermal water. In the studied sequence fluid inclusion data provide useful constraints for reconstructing the paleoenvironment controlling the evaporitic sedimentation. They also provide data on the water stratification in the basin and on its connectivity with the open sea, and important parameters controlling the productivity (possible sources for the nutrients) and the preservation of organic matter in the sediment. 相似文献
2.
The key drivers controlling the redox state of seawater and sediment pore waters in low energy environments can be inferred from redox-sensitive trace elements (RSTE), molecular biomarkers and trace metal isotopes. Here, we apply a combination of these tools to the Upper Permian Kupferschiefer (T1) from the Thuringian Basin, deposited in the southern part of the semi-enclosed Kupferschiefer Sea. Enrichment patterns of the RSTEs molybdenum (Mo) and uranium (U) as well as biomarker data attest to the rapid development of euxinic conditions in basin settings during early T1 times, which became progressively less extreme during T1 deposition. The evolution of redox conditions in basinal settings, and the associated delay in the onset of euxinia at more shallow marginal sites, can be attributed to the interaction of sea-level change with basin paleogeography. Euxinia in the southern Kupferschiefer Sea did not lead to near-quantitative depletion of aqueous Mo, possibly due to short deepwater renewal times in the Thuringian Basin, low aqueous H2S concentrations, the continuous resupply of RSTE during transgression and declining burial rates of RSTEs throughout T1 times. Drawdown of RSTE is, however, indicated for euxinic lagoon environments. Moreover, admixture of freshwater supplied to these lagoons by rivers strongly impacted local seawater chemistry. The highest Mo-isotope compositions of ~ 1.70‰ in basin sediments allow a minimum Kupferschiefer Sea seawater composition of ~ 2.40‰ to be estimated. This composition is similar to the ~ 2.30‰ estimate for the Late Permian open ocean, and confirms a strong hydrographic connection between the epeiric Kupferschiefer Sea and the global ocean. The substantial variation in Mo-isotope signatures is paralleled by diagnostic shifts in biomarkers responding to oxygenation in different parts of the water column. Water column chemistry has been affected by variation in sea level, hydrodynamic restriction, riverine freshwater influx and evaporitic conditions in shallow lagoons. Elucidation of the relative role of each driving factor by a single geochemical proxy is not feasible but the complex scenario can be disentangled by a multiproxy approach. 相似文献
3.
Harbridge William Pilkey Orrin H. Whaling Patric Swetland Paul 《Environmental Geology》1976,1(4):215-225
The Lake of Tunis in northern Tunisia is a eutrophic marine lagoon covering 45 km2 to an average depth of 1 m. Exchange of water with the Mediterranean Sea is restricted to a few canals. Bottom sediment is
mainly calcareous sandy mud with much organic material. Sand-size grains commonly include quartz, dolomite, gypsum, and pyrite,
as well as calcareous skeletal material dominated by molluscan fragments. Pyrite is the only important authigenic mineral
presently forming. Principal sources of sediment are sewage sludge and fill, calcareous marine organisms, including abundant
worm reefs, and local intermittent streams. The concentrations of Hg, Pb, Cd, Cr, Zn, Cu, and Fe are significantly higher
in Lake of Tunis sediments than in sediments from Bahiret el Bibane, an unpolluted lagoon in the south of Tunisia.
Man has affected the Lake of Tunis in four important ways. (1) Cultivation by early settlers, particularly the Romans, caused
increased regional erosion and probably provided the sediment that encloses the lagoon. (2) In the mid-1800's the French constructed
a ship canal which reduced intralagoonal circulation as well as exchange with the Mediterranean. (3) Nutrient pollution from
sewage has encouraged the growth of circulation-restricting worm reefs, caused eutrophication and fish kills, and produced
H2S odor which permeates the city of Tunis during the summer. (4) Finally, man has significantly reduced the size of the lagoon
by filling the lagoon and operating salt pans. 相似文献
4.
The geochemical evolution of the Catalan potash subbasin, South Pyrenean foreland basin (Spain) 总被引：1，自引：0，他引：1
Over the last decade, our studies in ancient evaporitic basins have been based on a detailed study of a single borehole record. The detailed findings in medium- to large-sized evaporitic basins were shadowed with a relevant question: can interpretations from a representative evaporitic record in a single borehole be extended to the whole evaporitic basin? This paper addresses that question; the results obtained are compared with results from another distant point within the basin. The general methodology not only proves its reliability in interpreting the evolution of evaporitic basins from a single borehole but reveals its capability to obtain detailed palaeoenvironmental interpretations.
The chemical evolution of an Upper Eocene evaporitic sequence from the South Pyrenean foreland basin (Spain) has been investigated along the Súria-19 borehole record. Detailed petrographic and mineralogical study, X-ray microanalysis of frozen primary inclusions trapped in halite (Cryo-SEM-EDS), systematic isotopic analysis (δ34S and δ18O in sulphates) and computer-based evaporation models have been integrated in a multi-proxy methodology. This study revealed that a variable amount of Ca excess is required throughout different parts of the marine Lower Halite Unit (LHU) for sylvite, instead of K–Mg sulphates, to form. This Ca excess is in turn different from that required for the western sector of the same evaporitic basin (Navarrese subbasin). Quick and variable changes in Ca-rich brines or equivalent dolomitization required are explained as internal processes within the basin rather than secular variations in seawater chemistry.
The general hydrological evolution of the Catalan subbasin is explained as a restricted subbasin with a first marine stage in which continental input (up to 50% of total input) had an important control on the geochemistry of the subbasin. A second stage was determined during potash precipitation, in which the subbasin was cut from any seawater input to end up in its last stage as a purely continental evaporitic basin. Coupling evaporation models and analytical results we have obtained the proportions of recycling and their sources, estimated to change from a 100% (total mass of sulphate) Eocene source to 20% Eocene and 80% Triassic (Keuper) towards the latest stage of potash precipitation. The results obtained have been compared with results from the Navarrese subbasin allowing an integrated interpretation of the hydrological evolution of the whole Upper Eocene South Pyrenean basin. Local geochemical variations within the Upper Eocene south Pyrenean basin are explained by the differences in paleogeographical setting of the Navarrese and Catalan subbasins. 相似文献
5.
Sedimentological, palaeontological and geochemical data provide detailed evidence of a marine-to-lagoon environmental succession around the Campanian-Maastrichtian boundary in the Ibero-Armorican domain. This regression is recorded by the succession of several environments of the south-central Pyrenees basin: open marine mixed shelf, marine restricted mixed shelf (both rudist-rich), tidal flat, lagoon and fluvial dominated. The tidal flat setting belongs to the Fumanya Member here described, which is the base of the Posa and Massana formations (Tremp Group). The Fumanya Member is 5 m thick, is built up of marly limestones and was an elongated tidal mudflat (100 km long, 25 km wide) developed in a foreland trough and was separated from the Atlantic Ocean by an island-barrier system. In the lagoon environment, marginal marine waters and continental fresh waters alternated as documented by geochemistry and fossil molluscs. The Fumanya Member is a dinosaur megatracksite, reporting the roaming activity only of sauropods in tidal flats, a likely secure area against predators. Feeding activity of these herbivores took place in the lagoonal-lacustrine environments of the Posa Formation above the Fumanya Member. 相似文献
6.
Diatoms in lower sediments from eight basins of the Frosta peninsula, Nord-Trødelag, Norway, have been analysed. All the basins have been isolated from the sea, and a succession from a flora influenced by marine and brackish water to a freshwater flora is always found. An attempt is made to establish a relative salinity range for the fjord basin around the investigated area, from the Younger Dryas chronozone to the end of the Atlantic chronozone. These changes seem to be controlled by the accumulation and ablation of the ice shield and also by major climatic changes in the early and middle Holocene. It is not possible to make a general list of lagoon taxa, because of great variation from basin to basin. The isolation contact (marine/brackish boundary) must be established at the end of the brackish water flora in the absence of lagoon types. The first period after isolation is characterized by a maximum in productivity with dominance of alkaliphilous types among the diatoms. A pioneer flora with dominance of Fragilaria taxa can be traced in the uppermost basins which were isolated just after the deglaciation of the area 相似文献
7.
The Boughrara Lagoon located in southern Tunisia shows evidence of eutrophication and the deterioration of water quality. The large amount of water shown to exchange tidally between the lagoon and the open sea suggests that while water per se is important and observed eutrophication problems are not caused by a lack of water. Heavy metal concentrations in surface sediments of the lagoon indicate that the ecosystem degradation is most likely related to the discharge of untreated phosphogypsum. Excessive pumping from the local freshwater aquifer that previously supplied freshwater to the lagoon via sub-aquatique fractures is likely to be a significant factor contributing to the water and sediment quality degradation of Boughrara Lagoon. 相似文献
8.
The evolution of marine evaporitic brines in inland basins: The Jordan-Dead Sea Rift valley 总被引：1，自引：0，他引：1
Marine-evaporitic brines frequently display Na, Cl and Br concentrations that significantly deviate from seawater evaporation paths, yielding markedly conflicting degrees of evaporation calculated for a specific brine. Here we present 493 new and 33 previously reported analyses of Ca-chloridic waters of Neogene age from the Dead Sea Rift (DSR) valley to explain such offsets. The DSR brines plot along an almost perfect mixing line (R2 = 0.990) on a Br/Cl-Na/Cl diagram, extending between two end members A and B. Points A and B are located at Na/Cl = 0.804 and Br/Cl = 0.00193, and at Na/Cl = 0.00773 and Br/Cl = 0.0155, respectively, within the halite and bischofite stability fields.Brines A and B originated in a dual-mode evaporation basin. Brine A formed under the classic lagoon scenario (mode A), with seawater inflow and brine outflow at steady state. Occasional drops in water level, imposed by climatic or tectonic causes, resulted in outflow cutoff and in rapid concentration buildup. The second mode (B) initiated upon equilibration of the activity of water in the brine with the overlying relative humidity, resulting in composition and salinity approaching that of brine B, sustaining it until the next reversal to mode A.Thick evaporite deposits inhibited infiltration of brines A and B into the subsurface terrain, a process that was enabled only when the brine reached the permeable carbonate rock rim and border faults of the basin. Hence, brines that formed during the relatively short shifts from mode A to mode B could not penetrate into the deep subsurface, and bittern minerals that were formed during the frequent mode shifts were dissolved and flushed out into the sea upon the next resumption of outflow.The proposed model accounts for the deviations of brines from the marine evaporitic evolution curve by brine mixing, rather than due to a change in ocean chemistry. It also explains the absence of bittern minerals in the thick halite and gypsum/anhydrite succession, and the compositional gap between the widely different end member hypersaline fluids. This model applies directly to the studied DSR brines and evaporites, but it may be relevant to other inland evaporitic basins. 相似文献
9.
沉积型天青石矿床的地质特征及其成因探讨 总被引：6，自引：0，他引：6
沉积型天青石矿床和蒸发岩类 ,特别是石膏的沉积密切相关 ,含矿地层主要是纹层状叠层石或藻灰岩。天青石中硫、锶同位素值和海水硫、锶同位素值相近。在蒸发条件下海水浓缩到一定浓度时 ,产生天青石沉积 ,或是富锶的硫酸型晶间卤水和钙碳酸盐反应 ,形成交代型天青石。天青石主要分布于蒸发盐盆地的边缘部位 ,位于钙碳酸盐和钙硫酸盐沉积的过渡带 相似文献
10.
本文通过野外剖面实测、样品采集、薄片鉴定等手段,收集地球化学数据及前人研究材料,对岐山地区岩性组合、沉积构造进行了研究,分析其中奥陶统沉积环境演化过程。结果表明,岐山地区在中奥陶统下马家沟组早期沉积白云岩,为局限海台地环境;下马家沟组中、晚期沉积中厚层状灰岩,为开阔海台地环境;上马家沟组沉积厚层的纹层状灰岩夹碎屑流、浊流等深水沉积建造,水体逐渐加深,并进入台地前缘斜坡沉积环境;峰峰组发育厚层的纹层状灰岩,为台地前缘斜坡环境并向深水海盆靠近。由此判断岐山地区应为南缘凹陷上,除淳化-旬邑次级凹陷以外的另一个水体更深、坡度更大的次级凹陷。 相似文献
11.
北祁连东部石炭纪岩相古地理 总被引：3，自引：0，他引：3
〗通过对石炭系实测剖面岩石的岩性、岩相、结构构造、粒度、古生物组合和古生态等特征的综合分析,利用石油勘探成果,研究了北祁连东部石炭纪岩相古地理。早石炭世早期,秦岭海域海水以天水—静宁古海峡为通道,向北侵入本区,形成由鄂尔多斯、阿拉善和陇西三大古陆围限的祁连海海湾沉积区,以咸化泻湖相、滨浅海相沉积为主,早石炭世晚期,海侵进一步扩大,以滨浅海相碎屑岩、碳酸盐岩沉积为主。晚石炭世海盆继续向东、向北扩展,海侵次数增多,形成了多个以碎屑岩为主夹灰岩沉积的海侵海退旋回,晚石炭世晚期太原组沉积时期,海水向东与华北海相连,成为广阔的陆表海沉积。中部地区存在近东西向分布的链岛状古隆起及水下隆起,古地形具西高东低、北高南低的特征。 相似文献
12.
鄂尔多斯盆地南部下奥陶统马家沟组沉积特征 总被引：2，自引：2，他引：0
依据鄂尔多斯盆地南部早奥陶世古构造、古地理、古水动力以及古气候背景,结合单井、野外露头沉积相分析等认为,秦岭海槽和中央古隆起的存在和演化控制盆地南部马家沟组沉积特征及演化。(1)平面上根据中央古隆起的障壁作用将其分为两大沉积区,西南区和东北区。西南区发育盆地—斜坡—台地边缘相,东北区为障壁潟湖沉积环境;(2)东北区马家沟组由"三云三灰"六段组成,马一、马三、马五段为白云岩、石膏和石盐组成的蒸发岩系,马二、马四、马六段为石灰岩夹白云岩的碳酸盐岩序列,在纵向上构成蒸发岩与碳酸盐岩间互的旋回性沉积。在此基础上进一步建立了马家沟组障壁潟湖沉积模式,该模式具有两个主要特征:(1)中央古隆起作为障壁控制秦岭海与潟湖之间的海水沟通;(2)依据海平面升降旋回将该模式动态地分为三个阶段,即与海侵期相对应的以石灰岩沉积为主的障壁潟湖沉积阶段(阶段Ⅰ)、与海退期相对应的以石灰岩夹蒸发岩沉积为主的障壁咸化潟湖沉积阶段(阶段Ⅱ)和与低海平面期对应的以膏盐岩沉积为主的障壁膏盐湖沉积阶段(阶段Ⅲ)。 相似文献
13.
14.
ABSTRACT The Tripoli Formation (Lower Messinian) in Sicily includes diatomites irregularly alternating with marl and carbonate beds and lies, stratigraphically, between the Tortonian pelagic marls and the evaporitic Calcare di base. The relationships between mineralogy, textural features and oxygen-carbon isotopic compositions of carbonate components point to a wide variability of depositional conditions and suggest that Tripoli sedimentation occurred in small basins characterized by periodic and marked restriction from the open sea.
The isotopic values of calcite and dolomite in the diatomites suggest an evolution from normal marine towards more restricted environments. Evaporating conditions are also indicated by the occurrence of anhydrite, length-slow chalcedonic quartz and moulds of gypsum. In a more advanced stage, the precipitation of heavy δ18 0 dolomite in the interstitial pores of fossil-poor diatomites denotes an environment with highly evaporated water. Mixing of meteoric and marine waters, on the other hand, might have favoured the precipitation of a dolomite characterized by relatively low δ18 0 and δ13 C values.
The deposition of marl and carbonate beds alternating with or overlying the diatomites took place in an environment with highly evaporated marine waters on the basis of δl18 O values of dolomite (up to + 9.10‰) and aragonite (up to + 5.83‰), occurrence of evaporitic minerals and lack of fossils. The presence at these levels of calcite with extremely negative δ13 C values (down to - 38.40‰), filling gypsum moulds, suggests activity of sulphate-reducing bacteria. Some aragonitic marls, however, bear evidence of deposition in relatively normal marine conditions. 相似文献
The isotopic values of calcite and dolomite in the diatomites suggest an evolution from normal marine towards more restricted environments. Evaporating conditions are also indicated by the occurrence of anhydrite, length-slow chalcedonic quartz and moulds of gypsum. In a more advanced stage, the precipitation of heavy δ
The deposition of marl and carbonate beds alternating with or overlying the diatomites took place in an environment with highly evaporated marine waters on the basis of δl
15.
四川盆地东北部在早三叠世飞仙关期的大部分时间内(飞一—飞三期)属于四周被深水海槽围绕的、受南秦岭海演化拉张断裂而形成的一个碳酸盐孤立台地环境,随四级海平面的升降变化、开江—梁平海槽的逐渐关闭和城口—鄂西海槽的东移,各种孤立台地亚相发生移动和转变,最终在飞三晚期至飞四早期孤立台地转化合并为川东北大型连陆台地。根据区域地质背景和地层沉积特征(岩性、古生物、沉积构造、测井)研究,划分了潟湖(包括蒸发潟湖、局限潟湖、半局限潟湖和点滩)、台地边缘鲕滩、斜坡、海槽4个亚相;建立出孤立台地的沉积立体模式并分析了沉积相从飞一飞三期的展布及演化过程;最后着重剖析了具备后期形成良好储层条件的孤立台地边缘鲕滩相带的迁移性、储层发育不均一性、测井和地震特征,沉积相对鲕滩气藏分布的控制,最后对孤立台地边缘鲕滩相中有望成为新的天然气勘探突破区进行了地震横向分布预测。 相似文献
16.
《Applied Geochemistry》2001,16(9-10):1269-1284
Chemistry of major and minor elements, 87Sr/86Sr, δD, and δ18O of oilfield waters, and 87Sr/86Sr of whole rock were measured from Paleozoic strata in the Central Tarim basin, NW China. The aim is to elucidate the origin and migration of formation water and its relation to petroleum migration. High salinity oilfield waters in Carboniferous, Silurian and Ordovician reservoirs have maintained the same Na/Cl ratio as seawater, indicative of subaerially evaporated seawater. Two possible sources of evaporitic water are Carboniferous (CII) and Cambrian, both of which contain evaporitic sediments. Geographic and stratigraphic trends in water chemistry suggest that most of the high salinity water is from the Cambrian. Strontium, H and O isotopes as well as ion chemistry indicate at least 3 end member waters in the basin. High-salinity Cambrian evaporitic water was expelled upward into Ordovician, Silurian and Carboniferous reservoirs along faults and fractures during compaction and burial. Meteoric water has likely invaded the section throughout its history as uplift created subaerial unconformities. Meteoric water certainly infiltrated Silurian and older strata during development of the CIII unconformity and again in recent times. Modern meteoric water enters Carboniferous strata from the west and flows eastward, mixing with the high salinity Cambrian water and to a lesser degree with paleometeoric water. The third end member is highly radiogenic, shale-derived water which has migrated eastward from the Awati Depression to the west. Enrichment of Ca and Sr and depletion of K, Mg, and SO4 relative to the seawater evaporation trajectory suggest waters were affected by albitization of feldspars, dolomitization, illitization of smectite, and SO4 reduction. The mixing of meteoric water occurred subsequently to seawater evaporation, main water-rock interactions, and brine migration. The direction of brine migration is consistent with that of petroleum migration, suggesting water and petroleum have followed the same migration pathways. 相似文献
17.
18.
Julie C. Gattacceca Adriano Mayer Andrea Cucco Christelle Claude Olivier Radakovitch Christine Vallet-Coulomb Bruno Hamelin 《Applied Geochemistry》2011,26(5):907-920
Several recent studies have suggested that submarine groundwater discharge (SGD) occurs in the Venice lagoon with discharge rates on the same order or larger than the surface runoff, as demonstrated previously in several other coastal zones around the world. Here, the first set of 222Rn data, along with new 226Ra data are reported, in order to investigate the occurrence and magnitude of SGD specifically in the southern basin of the lagoon. The independent connection with the Adriatic Sea (at the Chioggia inlet), in addition to the relative isolation of the water body from the main lagoon, make this area an interesting case study. There is probably only minimal fresh groundwater flux to the lagoon because the surrounding aquifer is subsiding and mainly has a lower hydraulic head than seawater.The data show that the Ra and Rn activities are in slight excess in the lagoon compared to the open sea, with values on the same order as those observed in the northern and central basins. Taking into account the water exchange rate between the lagoon and adjacent seawater provided by previous hydrodynamic numerical modelling, it is shown that this excess cannot be supported at steady state by only riverine input and by diffusive release from the sediment interstitial water. High activities observed in groundwater samples collected from 16 piezometers tapping into the shallow aquifer over the coastal lowland substantiate that the excess radioactivity in the lagoon may indeed be due to the advection of groundwater directly into the lagoon bottom water through the sediment interface. However, the data show that the groundwater composition is extremely heterogeneous, with high Ra activities concentrated within a narrow coastal strip where the contact between fresh and saline water takes place, while Rn strongly decreases when approaching the lagoon shore across the 20 km coastal plain. Assuming that the average groundwater activities measured in the coastal strip are representative of the SGD composition, a SGD flux of 7.7 ± 3.5 × 105 and 2.5 ± 2 × 106 m3/d is calculated using a 226Ra and 222Rn budget, respectively, (i.e. about 1-3 times the surface runoff), substantially lower than in previous studies. The influence of all assumptions on SGD estimates (groundwater heterogeneity, diffusive sediment flux, one-box versus multi-boxes model calculations) is discussed, and a sensitivity analysis of the influence of imperfect exchange and mixing at the lagoon outlets that affects the lagoon composition is provided. Finally, the results confirm that the SGD flux, calculated with these assumptions, is largely (∼80%) composed of saline lagoon water circulating through the sediment under the lagoon margin, and that the fresh water discharge associated with SGD is at most a minor term in the lagoon hydrologic balance. 相似文献
19.
沉积物颜色是其物质组成和形成环境的重要标志,对古海洋古环境重建有特殊指示意义。国际大洋发现计划(IODP)368航次在南海北部钻取的U1502站沉积岩心中发现了上百米红褐色-绿灰色韵律沉积层,但其成因不明。为探究其物源和红绿韵律沉积层的成因,我们对该站位岩心样品开展了矿物学和地球化学分析,包括粒度、黏土矿物、常微量元素和Sr-Nd同位素组成、有机碳含量及碳酸盐碳氧同位素组成分析。物源分析表明,U1502站沉积物陆源输入以珠江为主而吕宋次之,红层相对绿层有稍多的吕宋物质贡献。地球化学指标指示红绿沉积层的形成没有遭受热液、冷泉流体的影响,其形成是南海晚中新世构造演化和冰期-间冰期旋回中水体通风、底层水氧化还原环境改变及早期成岩作用共同影响的结果。结合以前南海北部沉积物源研究及沉积物颜色频谱分析,推测红绿层可能分别对应了间冰期-冰期时间尺度。指标重建指示了红绿层分别形成于偏氧化和偏还原的底层水氧化还原环境。自中中新世以来随着吕宋岛弧与欧亚板块碰撞,南海海盆从开放的环境变得相对封闭,其深部通风和氧化还原条件开始呈现典型的冰期-间冰期旋回模式。红层对应了间冰期高海平面时期南海深层水通风良好、水体偏氧化的沉积环境,而绿层则指示了冰期低海平面时期南海层化加强、水体偏还原的环境。不同的氧化还原条件控制了早期成岩作用中致色含铁自生矿物如赤铁矿的形成与转化,最终引起沉积层颜色韵律变化。 相似文献
20.
鄂尔多斯盆地奥陶系白云岩是重要的天然气储集层,对其白云岩成因和储层发育规律的研究对于碳酸盐岩深层勘探理论的发展具有重要意义。文章基于大量岩心、薄片的观察,并结合稳定碳氧同位素、稀土元素、白云岩有序度、地层水、包裹体特征等地球化学分析,对盆地奥陶系存在的两种典型白云岩储层的发育特征和形成机理进行了详细研究。分析表明,含硬石膏结核或柱状晶的泥粉晶白云岩主要为潮坪蒸发环境的萨布哈成因,其规模储层的发育主要受到长时不整合的控制,不整合面以下发育大量硬石膏结核和柱状晶溶模孔;颗粒滩白云岩主要为回流渗透成因,其储层孔隙的发育主要受到海平面高频升降的影响,发育多旋回的粒（晶）间孔隙型储层。虽然两种白云岩的白云石化流体都为浓缩海水,但由于白云石化的机制和速率不同,二者的原始孔隙类型和特征迥异。两种白云岩孔隙在后期的成岩改造和演变过程中,既有相同之处,又有明显的区别。这一认识也将对深层的白云岩储层勘探提供指导作用。 相似文献