Hydrocarbon accumulation in deep ancient carbonate-evaporite assemblages

The Ediacaran–Ordovician strata within three major marine basins(Tarim,Sichuan,and Ordos)in China are analyzed.Based on previous studies focusing on the characteristics of the Neoproterozoic–Cambrian strata within the three major basins(East Siberian,Oman,and Officer in Australia)overseas,the carbonate–evaporite assemblages in the target interval are divided into three types:intercalated carbonate and gypsum salt,interbedded carbonate and gypsum salt,and coexisted carbonate,gypsum salt and clastic rock.Moreover,the concept and definition of the carbonate-evaporite assemblage are clarified.The results indicate that the oil and gas in the carbonate-evaporite assemblage are originated from two types of source rocks:shale and argillaceous carbonate,and confirmed the capability of gypsum salt in the saline environment to drive the source rock hydrocarbon generation.The dolomite reservoirs are classified in two types:gypseous dolomite flat,and grain shoal&microbial mound.This study clarifies that the penecontemporaneous or epigenic leaching of atmospheric fresh water mainly controlled the large-scale development of reservoirs.Afterwards,burial dissolution transformed and reworked the reservoirs.The hydrocarbon accumulation in carbonate-evaporite assemblage can be categorized into eight sub-models under three models(sub-evaporite hydrocarbon accumulation,supra-evaporite hydrocarbon accumulation,and inter-evaporite hydrocarbon accumulation).As a result,the Cambrian strata in the Tazhong Uplift North Slope,Maigaiti Slope and Mazatag Front Uplift Zone of the Tarim Basin,the Cambrian strata in the eastern-southern area of the Sichuan Basin,and the inter-evaporite Ma-4 Member of Ordovician in the Ordos Basin,China,are defined as favorable targets for future exploration.

Dolomite genesis and reservoir-cap rock assemblage in carbonate-evaporite paragenesis system

Regarding to the problem on the reservoir-cap rock assemblage evaluation in the carbonate-evaporite paragenesis system,this study examined the dolomite and reservoirs genesis and the characteristics of reservoir-cap rock assemblage.Based on the literature research of the global carbonate reservoirs and the case study on four profiles of carbonate-evaporite succession,together with geological and experimental work,three aspects of understandings are achieved.(1)Lithology of carbonate-evaporite paragenesis system is mainly composed of microbial limestone/bioclastic limestone,microbial dolomite,gypsum dolomite and gypsum salt rock deposited sequentially under the climatic conditions from humid to arid,and vice versa,and an abrupt climate change event would lead to the lack of one or more rock types.(2)There developed two kinds of dolomite(precipitation and metasomatism)and three kinds of reservoirs in the carbonate-evaporite system;and the carbon dioxide and organic acid generated during early microorganism degradation and late microbial dolomite pyrolysis process,and early dolomitization are the main factors affecting the development of microbial dolomite reservoirs with good quality.(3)In theory,there are 14 types of reservoir-cap rock assemblages of six categories in the carbonate-evaporite system,but oil and gas discoveries are mainly in four types of reservoir-cap rock assemblages,namely"microbial limestone/bioclastic limestone–microbial dolomite–gypsum dolomite–gypsum salt rock","microbial limestone/bioclastic limestone–gypsum salt rock","microbial dolomite–gypsum dolomite–gypsum salt rock"and"gypsum dolomite–microbial dolomite–tight carbonate or clastic rock".These four kinds of reservoir-cap rock assemblages should be related with the climate change rules in the geologic history,and have good exploration prospects.

Rock Assemblages and Formation Ages of the Baishuijiang Group in the Southwest Qinling Orogenic Belt, Northwest China

The Baishuijiang Group, located in the southwest Qinling orogenic belt, is divided into three belts according to the characteristic of the matrix and rock blocks based on the large scale geological mapping. The north belt and south belt are composed of abyssal mudstone and siltstone, and limestone, chert and basic and ultrabasic rock blocks. The middle belt consists of a few limestone blocks and turbidites, which were formed in the trench environment. At present, in the Baishuijiang Group, many fossils were found in matrix and rock blocks, the fossils contain the Cambrian small shell fossils(Xiao, 1992;Tao et al., 1992), Silurian chitinozoas, scolecodonts and spores, and Ordovician graptolites, and middle Devonian Coral and conodonts in limestone and chert blocks(Wang et al., 2011a), and Permian radiolarians in the matrix(Wang et al., 2007). The volcanic rock blocks have undergone different degree of metamorphism. Their geochemical characteristics indicate that the rocks are similar to oceanic island arc and seamount(Wang et al., 2009), and SHRIMP U-Pb dating yielded ages from Neoproterozoic to early Paleozoic(Yan et al., 2007;Wang et al., 2009, 2011b). Therefore, comprehensive analysis of regional data, the Baishuijiang group is an accretionary complex which was consisted of matrix and blocks, and was finally formed during Permian-Triassic.

The Key Influence of Fluid in Metamorphic Rock Preserves, Mineral Assemblages, Compositions and Structures: Study from High-Pressure Eclogite and Its Amphibolization in the Western Dabie Mountains,Central China

The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should

Accumulation conditions and exploration directions of Ordovician lower assemblage natural gas, Ordos Basin, NW China

Based on drilling cores, well logging and seismic data, source rocks and reservoirs are evaluated;and the natural gas genesis is identified through the analysis of natural gas isotopes, components and fluid inclusions, to study the gas accumulation conditions of the gypsum salt rock related strata of the Ordovician lower assemblage in Ordos Basin.(1) The natural gas from Ordovician lower assemblage is high thermal evolution dry gas from marine source rock, characterized by relatively light δ^(13)C value of methane and heavy δ^(13)C value of ethane. The natural gas is identified as gas cracking from crude oil according to component analysis. Thermochemical sulfate reduction(TSR) reaction has happened between the hydrocarbon fluid and sulfate as sulfur crystals are found in the cores, hydrogen sulfide is found in the natural gas, and hydrocarbon and hydrogen sulfide fluid inclusions are widespread in secondary minerals.(2) Around the gypsum-salt lows, argillaceous rocks are extensive in the Ordovician lower assemblage, reaching a cumulative thickness of 20–80 m. The effective source rocks include argillaceous rock rich in organic laminae, algal clump and algal dolomite. Analysis shows that the source rocks have a dominant TOC of 0.1%–0.5%, 0.31% on average and 3.24% at maximum. The source rocks have an average TOC of 0.58% after recovered through organic acid salt method, indicating the source rocks have high hydrocarbon supply potential.(3) In the sedimentary period, the palaeo-uplift controlled the distribution of reservoirs. The inherited secondary palaeo-uplift in Wushenqi–Jingbian east of the central palaeo-uplift and the low uplift formed by thick salt rocks near Shenmu–Zizhou area controlled the distribution of penecontemporaneous grain shoal dolomite reservoirs. The salinization sedimentary environment of gypsum salt rock can promote the development of reservoir. There are three types of dolomite reservoirs, the one with intercrystalline pore, with dissolution pore, and with fracture;intercrystalline and dissolution pores are main reservoir spaces.(4) There are two types of cap rocks, namely tight carbonate rock and gypsum-salt rock, constituting two types of source-reservoir-cap assemblages respectively. The general accumulation model is characterized by marine source rock supplying hydrocarbon, beach facies limy dolomite reservoir, small fractures acting as migration pathways, and structural-lithologic traps as accumulation zones.(5) The third and fourth members of Majiagou Formation are major target layers in the lower assemblage. The Wushengqi–Jingbian secondary paleo-uplift area and Shenmu–Zizhou low uplift are dolomite and limestone transition zone, there develops tight limestone to the east of the uplift zone, which is conducive to the formation of gas reservoir sealed by lithology in the updip. Two risk exploration wells drilled recently have encouraging results, indicating that the two uplift zones are important prospects.

Dynamic Change and Simulation and Prediction of the Karst Rocky Desertification Sensitivity in Guizhou Province

Sensitivity evaluation of rocky desertification is to recognize the areas prone to be rock-deserted,so as to assess the sensitivity degree of rocky desertification to human activities.To perform the sensitivity evaluation of rocky desertification,we should be on the basis of the mechanism of rocky desertification formation for analyzing its regional distribution difference in the sensitivity and further for finding out the rocky desertification-susceptive areas and their possible degrees.Employing remote sensing and geological information system techniques,we regarded the 1∶ 50 000 topographic map and the TM image in 2000 of Guizhou Province,together with the hydrologic map,soil map,geologic map,rock formation map,administrative map and other geological information as data sources to generate the degree data of rocky desertification sensitivity of Guizhou Province in 1962 and 2000,based on which we determined the corresponding degree transfer matrix and adopted Markov model to simulate the dynamic change process of rocky desertification sensitivity and its future evolution trend.In various sensitivity types of rocky desertification in Guizhou Province,only the insensitive type showed a declined acreage,from the proportion of total land acreage of 61.35% in 1962 to 55.55% in 2000.Various sensitivity types inter-conversed,resultantly the acreage of mildly sensitive type increased most.The prediction results showed that the acreage of insensitive type of rocky desertification in Guizhou Province will assume a remarkable decline trend,of mildly sensitive type will present a remarkably increasing trend and of slightly sensitive type basically will maintain a stable level in the future tens of years.Acreages of both highly sensitive and extremely sensitive type of rocky desertification expanded to some extent,suggesting that the rocky desertification risk in Guizhou Province is in an aggravating process.

Geochemical Features and Tectonic Settings of Upper Ordovician Marine Volcanic Rocks on North Margin of Qaidam

The geochemical and petrological features show that the Upper Ordovician marine volcanic rocks on north margin of Qaidam can be classified into three main kinds of petrotectonic assemblages. The three assemblages exhibit features of tectonic melange. And they indicate that there exists an ancient ocean basin on north margin of Qaidam during Late Ordovician period. At the last stage of Ordovician period, the ocean basin on north margin of Qaidam closed gradually, then Qaidam continental block subducted continually and Qilian continental block thrusted onto Qaidam continental block in the direction from north to south, formed the orogenic belt of continent to continent collision type. As a result, a three unit tectonic model is proposed. The three units are: the overlying Qilian crustal wedge, the collision tectonic melange belt on the north margin of Qaidam and the Qaidam underthrusted wedge.

深层古老碳酸盐岩-膏盐岩组合油气成藏特征

通过分析塔里木、四川和鄂尔多斯三大海相盆地埃迪卡拉系—奥陶系,并对比参考东西伯利亚、阿曼和澳大利亚Officer三大国外盆地新元古界—寒武系的地层特征,将碳酸盐岩-膏盐岩组合划分成碳酸盐岩类和膏盐岩类互为夹层型、碳酸盐岩类和膏盐岩类互层型以及碳酸盐岩类、膏盐岩类和碎屑岩类共生型3种类型,明确了碳酸盐岩-膏盐岩组合的概念及内涵。结果表明:(1)碳酸盐岩-膏盐岩组合的油气通常来源于泥页岩和泥质碳酸盐岩两类烃源岩,咸化环境膏盐岩可促进烃源岩生烃。(2)主要发育膏云坪型、颗粒滩和微生物丘型两大类白云岩储集层,准同生期或表生期的大气淡水淋滤是储集层规模发育的主要控制因素,后期埋藏溶蚀作用对储集层有调整和改造作用。(3)碳酸盐岩-膏盐岩组合油气成藏模式可划分为盐下成藏模式、盐上成藏模式和盐间成藏模式3大类8小类模式。塔里木盆地塔中隆起北坡、麦盖提斜坡和玛扎塔格前缘隆起带寒武系、四川盆地东部—南部地区寒武系和鄂尔多斯盆地奥陶系盐间马家沟组四段等为未来的有利勘探领域。

宽高比对煤柱型冲击地压影响规律的实验研究

我国深部煤炭开采日趋复杂,区段煤柱在采动、构造或坚硬顶底板影响下极易诱发煤柱型冲击地压,煤柱型冲击地压的防治已成为煤矿安全高效开采的难题,研究不同宽高比条件下区段煤柱的力学性能及冲击破坏特性对煤柱型冲击地压防治具有积极意义。采用不同宽高比煤样的“岩-煤-岩”组合体进行了单轴压缩实验,通过分析煤岩组合体的冲击倾向性、动态破坏特征、分形维数和声发射特征参数等,研究了宽高比对煤柱冲击破坏的影响规律。结果发现:①煤柱的宽高比对煤岩组合体的冲击倾向性具有显著影响,宽高比不小于2∶1时,其冲击能量指数K_(E)为1.82~2.65,冲击倾向性无明显变化;小于2∶1时冲击倾向性呈先升高后降低的趋势,1∶1时K_(E)最大,达到了15.43。②随宽高比减小,煤岩组合体破坏特征依次表现为:拉压破坏—压剪破坏—拉剪破坏。煤柱宽高比为5∶1~3∶1时,煤岩组合体破坏较为缓慢;宽高比为2∶1时开始出现片状煤屑弹出,冲击破坏剧烈程度较低;宽高比为1∶1和0.75∶1时,具有明显的冲击破坏特性;宽高比为0.5∶1时,煤岩组合体整体稳定性下降,相对0.75∶1煤岩组合体煤柱破坏的剧烈程度降低。③峰后声发射能量释放率与分形维数D变化规律相似,均随宽高比减小呈先升高后降低的趋势。宽高比不小于2∶1时,煤岩组合体破坏过程中能量持续释放时间较长,煤柱破坏平缓;宽高比为1∶1时,能量释放率和D值明显增大,相较宽高比不小于2∶1煤岩组合体的能量释放率增大了约4倍,D值增大了0.18~0.23,煤柱冲击破坏最为剧烈;宽高比0.75∶1煤岩组合体能量释放率与D值分别降低了约10%和0.01,破坏剧烈程度与1∶1煤岩组合体相近;宽高比减小至0.5∶1时,相关参数的降低幅度约为0.75∶1煤岩组合体的6倍,破坏剧烈程度相对较小。研究表明:宽高比对煤柱的冲击破坏具有显著影响,整体上,煤柱冲击破坏剧烈程度随宽高比减小(5∶1~0.5∶1)呈先升高后逐渐降低的趋势;煤柱宽高比大于3∶1时,煤柱冲击危险性相对较小,煤柱宽高比为1∶1和0.75∶1时冲击危险性较大,0.5∶1次之。

吐哈盆地台北凹陷水西沟群成烃环境演变对煤系烃源岩分布及煤岩气保存的影响

吐哈陆相聚煤盆地是中国西部重要的含油气盆地。侏罗系水西沟群发育多套含煤优质烃源岩层,具有多套优质的砂岩储层和煤岩储层,是盆地主要的油气勘探目的层和深层煤岩气战略突破领域。通过研究盆地构造-沉积演化对烃源岩形成的影响以及微量元素对沉积环境的响应特征,分析了不同类型烃源岩的发育和分布规律,指出了煤岩储层中天然气(煤岩气)保存的有利空间位置。研究认为:①水西沟群沉积时期,构造抬升与沉降作用控制了台北凹陷沉积中心的形成与演化,沉积中心由北向南逐渐迁移;在晚侏罗世末期,北部发生强烈构造抬升,沉积中心继续向腹部迁移并造成东高、西低的地势特征,形成了现今胜北、丘东和小草湖洼陷3个逐渐向东抬升变浅的沉降中心。②沉积中心演化控制凹陷内不同次洼水体深度和盐度的变化。水西沟群八道湾组—三工河组沉积时期水体加深,盐度变小,三工河组—西山窑组沉积时期水体逐渐变浅,盐度增大。泥岩主要位于盆地的北部,具有自西向东加厚的特征。纵向上受古水体盐度的影响,八道湾组—西山窑组有机质类型和丰度具有逐渐变好的趋势。③水西沟群沉积期发生频繁的水体变动,煤形成于水体相对较浅的沉积环境。在八道湾组早期的水进初期阶段、八道湾组晚期和西山窑组早-中期的水退晚期阶段,水体相对较浅,为有利的聚煤环境,是吐哈盆地煤岩发育的主要层段。④在煤的发育区划分了10种不同类型的煤层顶-底板组合,提出了5个有利于煤岩气保存的煤层顶-底板组合类型及其分布位置,这些分布区是下一步煤岩气勘探方向。

深部煤-岩组合体力学特征及裂隙扩展规律——以沁水盆地武乡区块为例

煤层及其顶、底板的岩石力学性质是影响煤储层压裂、起裂和裂缝延伸的关键因素,制约深部煤层气的规模效益开发。为研究煤-岩组合体破裂过程中的力学特征及其裂隙扩展行为,根据声发射信号监测,开展了沁水盆地中、东部武乡区块煤-岩组合体的单轴压缩实验和有限元数值模拟计算,研究了煤-岩组合体中不同厚度比、不同岩性类别和不同交界面倾角对组合体抗压强度、弹性模量、声发射信号特征和破裂特征的影响规律,探究不同组合配置下的裂缝扩展行为。研究结果表明:①煤-岩组合体的抗压强度和弹性模量随煤-岩厚度比和煤-岩交界面接触倾角的增大而减小,不同岩性的组合体弹性模量介于1.75~5.44 GPa,抗压强度为11.20~20.60 MPa,其中煤岩-泥页岩组合体力学性质最弱,煤岩-砂岩组合体最强。②煤-岩厚度比增大会加剧组合体的破坏程度和裂隙数量,当煤-岩厚度比达到一定程度时,煤体发生破裂后能量会继续扩散到邻层,使整个组合体破碎。在不同岩性的组合体中,破坏难易程度为煤岩-砂岩组合>煤岩-灰岩组合>煤岩-泥页岩组合。随着煤-岩组合体交界面接触倾角增大,整体更容易被破坏失稳、产生裂隙。③随着组合体中煤岩厚度增大,发育的裂缝由张性裂隙演变为X型剪切裂隙,且由只在煤岩内部扩展逐渐过渡到整个组合体。不同岩性组合体的力学强度愈大,其裂隙越倾向于从X型剪切裂隙演变为张性裂隙,展布范围由整个组合体变为局限于煤岩内部。煤-岩交界面接触倾角的增大使组合体内部的X型剪切裂隙尺度相应增加,加剧破坏程度。

层状复合夹煤岩石组合体试样强度试验与破坏特征研究

针对巷道复合夹煤组合结构顶板易冒落问题,以某矿取芯和钻孔窥视探测获得的巷道层状复合夹煤顶板结构组合类型为实验背景,对砂质泥岩、中砂岩以及煤厚度为20、30、40 mm不同结构组合类型的复合试件进行了单轴压缩试验,研究了复合夹煤岩石组合体的力学特性与破坏特征。试验结果表明:复合夹煤岩石组合体的抗压强度均小于单一岩石,中砂岩夹煤厚度为30mm时抗压强度达到单一中砂岩抗压强度的85.95%,抗压强度随着煤厚变薄而下降;砂质泥岩夹煤厚度为20 mm时仅为单一砂质泥岩抗压强度的32.5%,随着夹煤厚度增加抗压强度也增大,夹煤厚度超过30mm后抗压强度增大不明显。复合夹煤岩石组合体整体呈X状共轭斜面剪切破坏、单斜面剪切破坏、部分拉伸破坏,随着复合夹煤岩石组合类型不同呈现不同的破坏特征等。

陆相细粒沉积岩岩相组合类型划分研究现状及其油气地质意义

细粒沉积岩是陆相页岩油气重要的烃源岩和储集层。然而该类岩石具有岩相类型多样、垂向叠置复杂的特征,已知大部分获得高产油气井对应的甜点层通常为多种岩相类型的组合。当前,细粒沉积岩岩相分类方案仍存在分歧,岩相组合相关研究尚处于初步阶段。通过对比近年来国内学者关于陆相细粒沉积岩岩相类型划分方案的差异性,梳理了岩相组合的划分依据,探寻岩相组合划分新方法及其研究的油气地质意义。认为在岩相类型识别基础上,开展天文旋回理论指导下的岩相组合类型划分、展布特征刻画,对于陆相页岩油甜点精细预测具有重要意义;分析不同岩相组合源-储耦合特征、油气分布特征,注重微运移的相关研究有助于提升对页岩油气差异性富集的认识。

渤海湾盆地临南洼陷古近系沙河街组源-储组合类型与致密(低渗)砂岩油差异富集模式

为了揭示渤海湾盆地临南洼陷古近系沙河街组致密(低渗)砂岩油的差异富集机理,在依据空间配置和岩性组合划分源-储组合类型的基础上,综合利用测井、录井、试油和岩心分析测试资料,对不同源-储组合类型含油性及其供烃条件、储集条件、输导条件和运聚动力进行了分析,建立了致密(低渗)砂岩油差异富集模式。结果显示:①研究区存在源-储共生型(夹层型、互层型)、源-储紧邻型(源上型、源间型和源下型)、源-储间隔型(源下型)3大类6亚类源-储组合,对应3种致密(低渗)砂岩油富集模式。②源-储共生型具有“强供烃-强动力-高效充注-储集控富”模式,供烃条件和运聚动力最优,油气通过孔缝高效充注,储层含油性最好;相较于互层型,砂体厚度制约了夹层型油气富集规模。③源-储紧邻型具有“较强供烃-差异动力-联合输导-多元控富”模式,供烃条件较好,运聚动力变化大,油气通过孔缝-断裂-砂体联合输导,优先充注物性和孔隙结构好的储层,储层含油性较好;亚类中,源间型供烃条件和运聚动力优于源上型和源下型,含油性最好。④源-储间隔型具有“弱供烃-弱动力-断砂输导-输储控富”模式,供烃和运聚动力较弱,断裂、砂体组成的有效输导通道和优质储层发育对于油气富集至关重要,含油性整体较差。

蒙古—鄂霍次克洋俯冲的火成岩记录:来自大兴安岭花岗岩类的证据

大兴安岭地区出露大规模的中生代花岗岩类岩石,它们的形成与蒙古—鄂霍次克洋或古太平洋的关系仍具有争论(杨华本等,2020;王亚东等,2023)。本研究通过野外调查采样,对大兴安岭北部黑河—白石砬子一带附近出露的18个花岗岩类岩石样品进行了岩石学、地质年代学和地球化学研究。

神府区块深部煤储层力学特性及裂缝扩展机制

【目的】明确煤力学性质和地应力的分布特征及其对人工裂缝形态和扩展行为的控制机制,对深部煤层压裂设计、井网部署和煤层气资源开发至关重要。【方法】以鄂尔多斯盆地东缘北部神府区块太原组8+9号煤为研究对象,基于声波测井、密度测井、注入/压降试井和排采资料,系统分析煤层及其顶底板岩层的力学性质和地应力分布特征,揭示力学性质和地应力对水力裂缝的控制机理。【结果和结论】结果表明:(1)8+9号煤层与顶底板形成了泥岩−煤−泥岩(占77.4%)、砂岩−煤−泥岩(15.5%)等6种组合。(2)基于声波和密度测井计算的力学参数显示,煤弹性模量在4.83~13.69 GPa(平均6.28 GPa),泊松比0.31~0.41(平均0.37),区域上南北脆性高,中部塑性高。(3)注入/压降试井计算结果显示,研究区最大水平主应力介于31.11~39.11 MPa,最小水平主应力变化范围为25.78~29.94 MPa;声波测井计算结果显示,垂向应力(平均49.12 MPa)>最大水平主应力(平均39.50 MPa)>最小水平主应力(平均33.80 MPa),煤层与顶底板最小水平主应力差在0~12.75 MPa。(4)Abaqus和Fracpro PT模拟结果显示,煤弹性模量越大,裂缝高度相对越大,当顶板与煤层的力学强度差较小时防止穿层;煤层水平主应力差增大,容易沿最大水平主应力形成单一裂缝;煤层水平主应力较顶底板水平主应力越小,易在煤层内形成较长、较低、较宽的裂缝,且不易穿层。研究认为实施较大的压裂规模、缝内暂堵技术和控制裂缝净压力等手段是提高神府区块8+9号煤水力压裂效果的主要途径。

基于变尺度岩相组合的陆相页岩源-储耦合机理探讨——以四川盆地侏罗系页岩层段为例

中国陆相页岩层系沉积成因及岩相组合复杂多样,陆相页岩源、储特征及耦合机理研究薄弱。以四川盆地侏罗系页岩层段为研究对象,以岩石学、沉积学及非常规储层地质学等理论为指导,综合运用岩矿、有机球化学及页岩储层表征等多种实验测试技术,开展了基于变尺度岩相组合的陆相页岩源-储耦合机理研究。提出了宏观与微观结合定岩相、变尺度分析定岩相组合的研究思路与方法,识别出陆源泥-砂沉积型、内源泥-灰沉积型和混源泥-砂-灰沉积型3种沉积成因岩相组合类型。研究发现:①页岩夹介壳灰岩或粉砂岩大尺度组合页岩段中可发育较多纹层-薄层状方解石介壳层或粉砂层,同一组合中不同尺度夹层类型具有较好的一致性;②大尺度岩相组合中米级介壳灰岩或粉砂岩层储集物性较差,对油气储集贡献有限,而小尺度岩相组合中毫米级纹层与厘米级薄层状方解石介壳粒内孔较发育,且内部有暗色有机质充填,可为油气提供有效储集空间。建立了3种沉积成因岩相组合的源-储耦合发育模式,提出由陆源型—混源型—内源型沉积岩相组合,源(总有机碳含量TOC)-储(孔隙度)参数相关性依次变好,其相关性主要与热演化程度、有机显微组分及无机矿物差异密切相关。探讨了不同类型、不同尺度岩相组合形成的影响因素,分析了从变尺度岩相组合角度认识陆相页岩油气源、储特征及耦合机理的必要性,旨在探索陆相页岩油气富集机理研究的新思路。

岩煤强度比对组合体破裂声发射及裂隙分形特性的影响

为研究不同岩煤强度比条件下煤岩组合体分层介质的渐进破坏特征,采用DYD-10电子万能试验机、PCI-8型声发射信号采集系统,结合能量耗散、分形理论,对不同岩煤强度比的煤岩组合体开展了单轴压缩试验。结果表明:不同岩煤强度比组合体试件破坏模式为煤体部分的剪切破裂进而牵引岩体破裂;岩煤强度比的增加,使得煤岩组合体的抗压强度在有限的范围内增加,而煤体强度是影响试件抗压强度的主要因素;分形维数D_(c)的斜率均大于D_(r),煤岩组合体全应力应变过程中裂隙在煤体部分的发育程度更完全;随着岩煤强度比增大,煤岩组合体中煤体部分裂隙更加发育、破坏程度更大,岩体部分裂隙扩展范围更小;当岩煤强度比增大时,煤岩组合体储能极限逐渐减小,试件内部储存的能量不足以驱动裂隙进一步向岩层部分扩展。该研究对进一步完善采动煤岩体动力学灾害防治具有重要意义。

Mineralogical study and significance of the basalt-hosted Carlin-type Au deposits in southwestern Guizhou Province,China

The Jiadi and Damaidi gold deposits in southwest Guizhou Province are the largest basalt-hosted Carlintype gold deposits recently discovered in China.This study uses the Tescan Integrated Mineral Analyzer,supported by detailed field investigations,regional geological data,and extensive sample collections,including mineralized ore,altered wall rock,and unaltered basalt samples,for orebearing and geochemical analyses.Comparative analysis between altered and unaltered basalt samples revealed a mineral assemblage of sericite,quartz,and pyrite.This mineral composition forms through the hydrothermal alteration of unaltered basalt,originally containing feldspar,pyroxene,and ilmenite.The wall rock primarily features sericite,quartz,and hematite.During the alteration process,major,trace,and rare earth elements notably migrate.In the Jiadi deposit,K_(2)O,Rb,Au,and REE significantly increase,while Na_(2)O,CaO,MgO,and MnO decrease.SiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)levels remain relatively stable.In the Damaidi deposit,K_(2)O,Rb,and Au enrich,contrasting with the depletion of Na_(2)O,CaO,MgO,and MnO,while SiO_(2),Fe_(2)O_(3),Al_(2)O_(3),TiO_(2),and REE show no significant changes.In the wall rock,TiO_(2),Al_(2)O_(3),K_(2)O,and REE increase,while Na_(2)O,CaO,MgO,and MnO decrease;SiO_(2)and Fe_(2)O_(3)content remains unchanged.The mineralization process likely originated from mid-to low-temperature,reductive magmatic hydrothermal fluids rich in CO_(2),CH_(4),N_(2),H^(+),S^(2-),HS^(-),H_(3)AsO_(3),and[Au(HS_(2)]^(-).These fluids migrated to tectonically weak zones in the Lianhuashan area,where Emeishan basalts are present.They reacted with Fe-bearing minerals in the basalt,such as ferro-hornblende and ilmenite,forming pyrite,arsenic-bearing pyrite,and arsenopyrite,thus enriching Au in these minerals.Additionally,K^(+)and H^(+)in the fluid reacted with plagioclase in the basalt,forming sericite and quartz.As the fluid entered the wall rock from structural weak zones,its oxidation increased,leading to the complete or partial reaction of Fe-bearing minerals in the wall rock,resulting in the formation of hematite or magnetite.This mineralization process is similar to that observed in carbonate-hosted Carlin-type gold deposits in southwest Guizhou,with the primary distinction being the iron source.In carbonate deposits,iron originates from ferridolomite within the wall rock,while in basalt-hosted deposits,it derives from ferripyroxene and ilmenite.

Petrology and high-pressure mineral assemblage of maflc-ultramaflc rocks of ultrahigh-pressure metamorphic zone in the Dabie Mountains

The relation between edogite and mafic-ultramafic rocks of Maowu, Bixiling and Nanshanling in Dabie Mountains represents three different kinds of occurrence relations. Their protoliths are bedded cumulate formed by crystallization differentiation of basic magma, which experienced ultrahigh-pressure metamorphism under the mantle condition at the depth of more than 120- 150km during the colli-sion-subduction between the Yangtze Plate and North China Plate. Ti-dinohumite + Ti-chondrodite + magnesite + Al-poor pyroxene is the typical high-pressure mineral assemblage of mafic-ultramafic rocks which reveals the participation of H2O, CO2 and other volatiles-containing fluid in the ultrahigh-pressure metamorphism.