新生代辉绿岩侵入对围岩物性的影响:以苏北盆地洋心次凹为例

传统观念认为岩浆活动区是油气勘探的禁区,但现今理论研究与实践勘探发现岩浆侵入作用能够显著改造围岩物性。目前岩浆侵入对围岩具体的影响认识不清,查明岩浆侵入影响围岩物性的机理对油气勘探具有重要意义。以苏北盆地洋心次凹的丰页1井为例,结合测井、地震及岩心等资料重点分析辉绿岩侵入对围岩储层物性与储集空间的改造,深入讨论其影响机制。苏北地区丰页1井的辉绿岩在吴堡运动期(约59 Ma)开始顺层侵入,侵入体中心相为辉长岩,侵入体边缘相为辉绿岩,变质相为板岩,上变质带厚度大于下变质带厚度。围岩由非渗透性泥岩转变为油气储层,储集空间为辉绿岩侵入和泥岩变质过程中产生的裂缝与孔隙。辉绿岩的侵入显著提高围岩储层物性,主要的机制有变质固结、热液破裂、冷凝收缩和溶蚀作用4种,其中热液破裂和溶蚀作用对储层的形成最为关键。     

高邮凹陷北斜坡辉绿岩及其接触带储层发育特征与有利油气藏条件

理论研究与勘探实践表明岩浆侵入作用能够形成侵入岩—外变质带油气储层。以高邮凹陷北斜坡地区阜宁组为研究层位,根据岩心、薄片、分析测试等资料,重点研究了高邮凹陷北斜坡地区辉绿岩及其接触带的储层发育特征,并从烃源岩和成藏条件分析了研究区油气藏形成的有利条件,讨论了岩浆侵入活动对油气成藏造成不利影响的可能性。辉绿岩及其外变质带(接触带泥岩和砂岩)均可作为储层,辉绿岩储集空间包括原始气孔、冷凝裂缝、溶蚀孔隙、微孔、收缩微缝及构造裂缝;接触带泥岩储集空间包括构造裂缝、热液微裂缝、收缩缝、解理缝、晶间微孔和微溶孔;接触带砂岩储集空间包括原生粒间孔、粒间溶孔、粒内溶孔、铸模孔、超大孔及微溶孔。辉绿岩和接触带泥岩整体物性较差,非均质性强,发育的裂缝系统是储层性能改善的重要因素。相对于未受辉绿岩影响的正常储层而言,接触带砂岩的储集性能变差。研究区地球化学特征和油气藏分布特征等证据表明辉绿岩侵入降低了烃源岩生烃门限,加速了有机质向油气的转化,为辉绿岩及变质带储层提供了油气来源。研究区有利成藏条件主要包括:近距离油源供给、辉绿岩侵入形成运移通道、油气运移与圈闭形成良好时空配置、较大规模的辉绿岩及变质带和良好的封闭遮挡条件。     

岩浆侵入活动对砂岩的改造作用研究简介

岩浆侵入活动对砂岩的改造作用包括：侵入岩胀裂而导致已固结砂岩的脆性破裂和未固结砂岩的压溶作用；热流体促进或参与砂岩中矿物间的反应，使砂岩发生热变质作用，形成低温变质矿物；侵入活动提供的高温加热地层水，通过热对流的方式使砂岩温度突变，形成“相对高温”的自生矿物或引起一些溶解度对温度变化敏感的自生矿物的溶解和重新沉淀。     

浅层侵入体泥岩变质带储集特征及发育模式—以江苏高邮凹陷北斜坡侵入体泥岩变质带为例

对江苏高邮凹陷北斜坡浅层侵入体泥岩变质带储集特征及发育模式开展的研究表明,泥岩变质带厚度与侵入体厚度呈正相关关系,按变质程度差异分为3个岩相带:角岩带、板岩带和变余泥岩带。其储集空间以各种成因的裂缝为主,物性变化受热接触变质作用控制,越靠近侵入体储层物性越好,即角岩带物性好于板岩带及变余泥岩带。岩浆侵入带来的高温高压、热流体活动及冷凝收缩作用是泥岩变质带储层发育的主要动力机制;侵入体上下变质带多呈非对称发育,上部变质带厚度及物性均优于下部变质带,这种非对称发育特征主要受控于高压热流体向上优势运移作用;其中上部角岩带为泥岩变质带相对优质储层发育部位。通过分析岩浆侵入与油气运聚的时空匹配关系认为泥岩变质带具有较大成藏潜力。     

岩浆侵入对围岩储层的成岩及其变质特征的影响及意义——以松辽盆地南部辉绿岩侵入带露头研究为例

以松辽盆地南部团山子采石场辉绿岩侵入露头为例,采用连续密集取样、常规分析和碳氧稳定同位素测试等方法,对围岩储层的成岩及其变质特征进行分析,进而探讨岩浆侵入对围岩的影响及其储层意义。岩浆侵入对角岩围岩的影响包括：1）自生绢云母距离侵入体越远,其含量越少;2）粘土矿物主要为成岩晚期的伊利石和绿泥石;3）角岩中发育特殊“气孔-杏仁”构造。岩浆侵入对上覆砂岩的影响表现为：1）造成自生石英的特征分布;2）造成粘土矿物的不均匀分布;3）形成反映应力挤压特征的颗粒结构。角岩中浊沸石发育和高岭石不发育对应碱性环境,不利于热液微裂缝中碳酸盐矿物的溶蚀。因此,尽管角岩发育微孔、微缝等少量储集空间（平均孔隙度为1.70%）,但其渗透能力很低（平均渗透率小于0.1 mD）。侵入活动对研究露头砂岩储层物性造成的不利影响,主要是由于挤压作用和热液流动作用使自生矿物不均匀分布,从而导致或加剧了砂岩储层的非均质性。     

花岗质岩浆侵位对围岩裂隙发育和热结构影响的数值模拟

岩浆侵位会引起围岩的接触变质作用和变形，虽然围岩中的破裂提供了流体活动和元素迁移的重要通道，但是大多数岩浆侵位模型忽略了围岩中热对流的影响。本文总结了岩浆侵位的数值模拟原理和常用模拟方法，然后使用离散元软件MatDEM建立了二维的双层围岩模型和均质围岩模型，用孔隙密度流法模拟花岗质岩浆侵位和冷却过程中岩浆与围岩之间的流- 固- 热- 力耦合过程。结果表明岩浆侵位过程中围岩的裂隙发育和热对流对接触变质晕具有重要影响，围岩的裂隙发育和热传输模式可分为三个阶段：① 岩浆侵位初期的挤压力使围岩中产生广泛分布的、呈径向展布的剪裂隙，围岩以热传导和孔隙渗流为主导；② 在持续的孔隙流体压下，径向裂隙连通形成主干张性断裂并向上扩展，成为熔/流体迁移的重要通道以及伟晶岩型和热液型矿床的成矿空间，通道流和局部热对流控制了围岩的热传输；③ 在岩浆侵位后期，岩浆房附近围岩中的孔隙流体压增大，在侵入体与围岩的接触带形成大量张裂，加强了变质晕内的热对流，有助于矽卡岩型矿床的形成。与只有热传导的模型对比，热对流使围岩中变质晕的宽度减小。接触变质晕的几何形态受侵入体的形态控制，但是变质晕宽度在空间上有显著差异。本研究为重建岩浆侵位过程中的变质- 变形- 成矿作用提供了新方法。     

花岗岩侵入体-泥质围岩热传输过程的数值模拟及其地质意义：以粤东典型接触带剖面为例

岩浆侵入作用可以引发水- 岩反应和多种形式的变质作用和金属富集,当侵入至富含有机质的泥质围岩时,其热效
应不仅会造成热接触变质、改变围岩的成岩作用,还会促进围岩中烃源岩的生烃作用。热传输模型研究是定量- 半定量考
察岩浆侵入体及其围岩热演化的重要工具之一。本文选取粤东典型的花岗岩- 泥岩接触带剖面,在开展地质地球化学研究
的基础上,进行了二维热传输模型分析。模拟结果与地质基本一致,发现岩浆侵入能够显著提高接触带围岩和上覆围岩的
地温,其中侧向传输的范围有限,根据多个规模不等的花岗岩岩体热传输模型分析结果,发现小型侵入体的热影响范围与
其侵入体规模正相关,但对于大型侵入体而言,其侧向影响范围一般在2.5 km 左右。本文研究成果对认识与岩浆活动有关
的成矿作用和油气成藏作用有着重要意义。     

热对流成岩作用的基本特征与研究意义

介绍了热对流产生的条件与地质背景,指出火成侵入体、盐丘和活跃断层周围等温线陡倾斜场所易发生热对流成岩作用。综述了岩浆成因热对流的岩石学记录,包括热变质作用、突然升温—逐渐降温的自生矿物组合和相对高温的自生矿物类型,分析了自生伊利石的K/Ar年龄在热对流成岩作用研究中的作用。阐述了热对流成岩作用对盆地动力学、砂岩储层和油气运移研究的意义。     

惠民凹陷岩浆作用对碎屑岩储层的影响

岩浆活动对碎屑岩储层的影响主要包括岩浆上拱作用、热烘烤作用和热液作用。岩浆上拱作用往往使上覆岩层中产生裂缝。而热烘烤作用使周围碎屑岩产生不同程度的变质,如使泥岩变质为板岩。轻微变质的板岩一般为有效封盖层,变质程度相对高的板岩,易发育裂缝而成为有效储集层。另外,岩浆活动造成局部地温梯度高异常,促使周围烃源岩热演化生成的烃类、有机酸、二氧化碳,与岩浆携带的无机二氧化碳一起注入周围碎屑岩储层中,使储层原始孔隙得以保留并产生次生孔隙。在基性岩浆侵入或喷溢活动中,岩浆中的Fe2+、Mg2+,有利于周围碎屑岩中的蒙脱石向绿泥石转化。而在酸性介质条件下,碎屑中长石颗粒蚀变提供的K+,有利于蒙脱石向伊利石转化。结果出现火成岩体周围储层中粘土矿物组合具富绿泥石而贫高岭石以及伊利石相对百分含量较高的特征。     

东北及华北含油气盆地岩浆活动对碎屑岩的改造与成岩作用贡献

含油气盆地中的岩浆活动不但对碎屑岩围岩进行了物理改造，而且也引起了分布局限的热变质作用。同时，岩浆活动也加速了围岩的成岩作用进程。并且直接或间接地为成岩作用提供了物质来源。岩浆活动对碎屑岩围岩的物理改造表现为围岩热拱张裂和气孔一杏仁构造的形成，前者普遍见于三江盆地、松辽盆地和渤海湾盆地；后者发现于松辽盆地南部。岩浆活动引起的热变质作用普遍见于三江盆地、松辽盆地、渤海湾盆地和海拉尔盆地，并且以泥岩围岩的角岩化、砂岩围岩中基质重结晶成绢云母和绿泥石为特征。岩浆活动也可引起氧化硅凝胶在孔隙中的直接沉淀，例如松辽盆地南部营城组砂岩中的梳状石英。由于岩浆活动引起了地温梯度的升高，因而在浅部地层中可发现深部地层中才可形成的铁方解石等。岩浆活动直接或间接引起的片钠铝石和方解石的沉淀见于海拉尔盆地、三江盆地和渤海湾盆地。     

致矿侵入体的识别标志——以新疆阿尔夏提矽卡岩型铁铜矿床为例

致矿侵入体的识别是成矿学研究和资源勘查的关键环节之一,对于许多矿床类型来说也是一个难点.本文以新疆阿尔夏提矽卡岩型铁铜矿床为例,阐述了通过建立五种联系及其地质学、岩石学、矿物学、地球化学和成矿学标志的识别方法,进而提出推木尔特岩基为含矿流体屏蔽层的认识.推木尔特岩基与矽卡岩矿体具有紧密的空间联系,容易被误认为是致矿侵入体.然而,其成岩时间早于成矿时间,仅导致围岩的大理岩化和角岩化,因而不是成矿物质的来源.相反,矿区内分布的闪长质小岩体和各类岩墙不仅与矿体和矽卡岩存在紧密的空间联系,而且岩石中普遍见有造矿矿物与造岩矿物的共结关系,岩体(墙)本身及其围岩也经受了强烈的流体改造,是含矿流体的通道和真正的致矿侵入体.     

山东莱芜盆地碳酸盐岩热液溶蚀特征及水文地质意义

鲁中山区莱芜盆地在燕山期发生大规模岩浆侵入活动,岩浆岩体外围碳酸盐岩区分布有水源地、富水块段等岩溶发育富水区,且靠近岩体含水层多发生大理岩化。富含CO₂、H₂S等酸性成分的岩浆热液流体,能对碳酸盐岩产生明显的溶蚀作用。基于岩石样品化学组分分析、水文地质调查及数据统计分析、热液溶蚀地质点详细观测,构建热液溶蚀模式,对莱芜盆地及外围热液溶蚀特征及机理进行研究。结果表明:高温高压岩浆侵入使得接触带碳酸盐岩发生热液变质大理岩化;沿渗透性断裂、裂缝以及不整合面等运移的热液流体,对碳酸盐岩地层产生酸性热液溶蚀和混合溶蚀作用,形成不同规模溶蚀孔洞,构成地下水富集空间,为寻找城镇地下水后备水源地提供新方向。     

Geological and structural conditions of eclogitization of Paleoproterozoic basic dikes in the eastern Belomorian Mobile Belt

A new, Krasnaya Guba dike field that comprises more than 30 minor gabbronorite intrusions and dikes of “garnet” Fe-gabbro was revealed at the northeastern flank of the Belomorian Mobile Belt. Gabbronorite intrusions were emplaced along the faults that formed as a result of brittle failure under conditions of general extension. As follows from the structural relationships, dikes of Fe-gabbro are younger than gabbronorite. They were formed under compression and shearing. The mobile melt was pumped into gneisses that underwent ductile deformation. Eclogitization in the Krasnaya Guba dike field was selective and affected only dikes of Fe-gabbro and minor gabbronorite intrusions and did not develop in country rocks. The bodies of Fe-gabbro are eclogitized almost completely, whereas gabbronorite is transformed into eclogite only along shear zones. Eclogites were formed after the complete solidification of intrusive bodies, and their localization is controlled by the concentration of deformations owing to the different elastoplastic properties of gabbroic rocks and country gneisses and migmatites. The different degree of fracturing in basic dikes and country gneisses resulted in the concentration of fluid flows in fracture systems within competent rocks. Late Svecofennian pegmatites (1.86 Ga) distinctly crosscut eclogites that experienced retrograde metamorphism. The eclogitic rocks from the Krasnaya Guba are the youngest known in the Belomorye. The age of eclogitization is 2.12–1.86 Ga. A new finding of eclogitic rocks in the Belomorye, as well as previously known similar rocks near Gridino Village, emphasize tectonic activity of the northwestern Umba Collision Zone. The eclogitization of basic rocks in Krasnaya Guba is related to their desilification in shearing zones in the course of interaction of plagioclase with ortho-and clinopyroxene with the formation of garnet-omphacite aggregate and removal of silica. The currently observed texture, structure, and chemical and mineral compositions of eclogitic rocks are products of intense retrograde metamorphism.     

Dating mafic–ultramafic intrusions by ion-microprobing contact-melt zircon: examples from SW Sweden

Zircons from anatectic melts of the country rocks of three Proterozoic mafic–ultramafic intrusions from the Sveconorwegian Province in SW Sweden were microanalyzed for U–Th–Pb and rare earth elements. Melting and interaction of the wall rocks with the intrusions gave rise to new magmas that crystallized zircon as new grains and overgrowths on xenocrysts. The ages of the intrusions can be determined by dating this newly crystallized zircon. The method is applied to three intrusions that present different degrees of complexity, related to age differences between intrusion and country rocks, and the effects of post-intrusive metamorphism. By careful study of cathodoluminescent images and selection of ion probe spots in zircon grains, we show that this approach is a powerful tool for obtaining accurate and precise ages. In the contact melts around the 916?±?11?Ma Hakefjorden Complex, Pb-loss occurred in some U-rich parts of xenocrystic zircon due to the heat from the intrusion. In back-veins of the 1624?±?6?Ma Olstorp intrusion we succeeded in geochemically distinguishing new magmatic from xenocrystic zircon despite small age differences. At Borås the mafic intrusion mixed with country rock granite to form a tonalite in which new zircon grew at 1674?±?8?Ma. Reworking of zircon occurred during 930+33/–34?Ma upper amphibolite facies Sveconorwegian metamorphism. Pb-loss was the result of re-equilibration with metamorphic fluids. REE-profiles show consistent differences between xenocrystic, magmatic, and metamorphic zircon in all cases. They typically differ in Lu/La_N, Ce/Ce*, and Eu/Eu*, and igneous zircon with marked positive Ce/Ce* and negative Eu/Eu* lost its anomalies during metamorphism.     

中国东部中、新生代含油气盆地火成岩油气藏成藏机制

中国东部中、新生代盆地油气资源丰富,其地层中广泛发育着以玄武质及粗面质为主的火成岩。这些火成岩既可为油气提供储集空间也可作为油气藏的盖层,形成了一定量与火山岩及潜火山岩相关的油气藏。与火山岩有关的油气藏主要有火山岩储层型、火山岩盖层型和风化壳型,而与潜火山岩有关的油气藏主要有拱张裂缝型、隐爆角砾岩型、原生裂缝型、蚀变破碎型和侧向隔挡型。本文评述了这些火成岩型油气藏的成藏机制,提出了中国东部中、新生代含油气盆地中的火成岩油气藏综合成藏模型,以期这类油气藏在今后的油气勘探工作中得到充分重视。     

多宝山斑岩铜矿床成因模式

多宝山斑岩铜矿床位于蒙古—鄂霍茨克(古亚洲)地槽东部。矿区周围出露的地层以中古生界为主,在复背斜核部出露有奥陶系。从多宝山矿区向东南40公里为新开岭隆起,隆起呈北东东走向,上面地层多属下古生界和前古生界,而其东南广大地区地层多属石炭二叠系。多宝山矿区含矿的花岗岩体,经K-Ar法年龄测定,为292百万年,属中石炭世。由此可见,在多宝山矿床形成期间,多宝山矿区应位于正负构造单元接壤处偏隆起一侧。     

Evidence of multiple intrusion,possible resetting of U-Pb ages,and new crystallization of zircons in the post-tectonic intrusions (‘Rapakivi granites’) and gneisses from South Greenland

U-Pb data for zircons from post-tectonic monzonite, syenite and norite, and country rock gneiss and migmatite from the Kap Farvel-Prins Christian Sund area of South Greenland indicate two distinct intrusive episodes at ～1740 m.y. and ～1755 m.y. The norites have the same age as the older granitic rocks. Similar intrusions further north along the southeast coast have the same age (～1755 m.y.) and geochemical character as those of the Kap Farvel-Prins Christian Sund area. Our U-Pb ages are about 100 m.y. older than previously determined K-Ar ages.The youngest peak of regional Ketilidian metamorphism in this area is placed at about 1800 m.y. based on a linear array of seven magnetic and size fractions from a syntectonic granitic part of a migmatite. This age is distinctly different from the post-tectonic intrusions and, along with other data, precludes the possibility of in situ formation of the intrusions by remelting of the country rocks.In one hypersthene migmatite sample collected near a post-tectonic intrusion, clear overgrowths and separate clear grains with low uranium concentrations were identified. The clear grains of zircon have the same age as the intrusion, indicative of new zircon growth during the granulite facies recrystallization of the gneiss. In contrast, rounded red zircons from an early subconcordant granitic sheet have clear uranium-rich overgrowths which probably formed during regional metamorphism. If the deep-red zircons observed in one of the post-tectonic intrusions were derived from the surrounding metamorphic rocks, they have had their U-Pb systems reset to the time of intrusion.In accord with observations (Krogh, 1971) on non-magnetic zircon fractions from volcanics, the Greenland zircons contain very low amounts of common lead ranging from <0.01 ppm in the least magnetic fractions in the post-tectonic intrusions, to 6.5 ppm in the most magnetic fractions of the gneisses. These two rock groups can be differentiated on the basis of their common lead content.     

Geophysical surveys to help map buried igneous intrusions,Snowdonia, North Wales,UK

The geology of the Snowdonia National Park in North Wales comprises a mixture of Lower Palaeozoic shallow marine sediments, acidic igneous rocks and basic intrusions of the Welsh Basin that were subsequently deformed during the Caledonian Orogeny. Thin igneous intrusions are challenging to map due to variable surface exposures, their intrusive origin, structural deformation and burial by glacial sediments. This study used a combination of traditional geological techniques, near‐surface geophysical surveys and remote sensing to detect and map a buried dolerite sheet intrusion. Both simple and mathematical analysis of magnetic anomalies and numerical modelling allowed the dolerite position, depths and target widths to be determined. Results showed that calibrated magnetic surveys can characterize buried igneous bodies in such mountainous environments.