裂后岩浆活动中岩床复合体的特征:以南海北部和南极西罗斯海地区为例

由于蕴含着潜在的油气勘探和资源储藏信息,岩床复合体在全球范围内被广泛研究。本文基于南海北部三维地震资料以及南极罗斯海地区二维多道地震资料,对岩床复合体的形态特征及分布进行分析,对两个地区岩床复合体的形成时间进行判断,阐述岩床复合体的侵位机制。研究发现,岩床复合体代表性产状除了菱形、碟形及复合型外,还存在沿着层位平行侵入的板状,推测它可能是夭折了的岩床侵入体,以及由几个小型岩床堆叠而成的透镜状岩床复合体。分布上,南海北部岩床主要发育于珠江口盆地白云凹陷三维工区西部,东部只零星可见;南极西罗斯海岩床主要发育于西北角的阿黛尔盆地内。根据岩床上覆的强制褶皱结合区域构造背景,推测南海北部岩床复合体的形成时间为早中新世(15.5 Ma),海底扩张结束之时。残余岩浆将盆地内裂谷时期形成的断层作为岩浆运移的通道,并最终在断层终点处即下中新统近海相砂泥岩地层中实现侵位。南极西罗斯海岩床复合体的形成时间则非常晚,不早于5.5 Ma。该区这期岩浆活动可能与构造作用无关,而是受到冰川消融的影响。研究发现岩床复合体内部的岩床个体互相供给,即深部的大岩床为上覆浅层的小岩床提供岩浆供给,并且互相组合,形成大的岩床复合体。然而,每个岩床复合体则可能由不同的岩浆供给发育而成。     

多期岩浆侵入事件对长昌凹陷烃源岩热演化的影响

最新研究表明长昌凹陷发育多期岩浆侵入事件。针对多期岩浆侵入事件对长昌凹陷烃源岩热演化的影响尚不明确的问题,文章依据最新地震、地化、钻井等资料,利用地震相技术在凹陷内识别出9个四期岩浆侵入体;在此基础上,运用三维盆地模拟技术对岩浆侵入事件进行热模拟,定量评价多期岩浆侵入事件对凹陷内烃源岩热演化影响。模拟结果表明,岩浆侵入体对烃源岩热演化有促进,但影响范围有限,岩浆体规模与其影响范围有如下规律：岩浆体直径小于2 km,对烃源岩热演化影响范围的半径小于2 km;岩浆体直径大于2 km而小于5 km,影响范围半径小于5 km;岩浆体直径大于10 km而小于20 km,影响范围半径小于16 km。因此长昌凹陷烃源岩主体热演化基本不受岩浆侵入事件的影响,且其可能带来非烃充注风险。结合岩浆侵入体对研究区两口钻井影响的分析,厘定长昌凹陷生烃门限为海底以下2300~2500 m。这些研究为凹陷下一步油气勘探奠定了基础。     

晶粥储存、侵入体累积组装与花岗岩成因

花岗质岩浆在地壳内的储存、迁移和分异,是导致大陆地壳生长演化的基本过程.有关地壳岩浆冷储存的新发现,挑战了数十年来深部存在以熔融体为主要组成的大岩浆房的观点.对活火山区的地球物理探测、岩石矿物学研究以及热历史模拟都一致证明,岩浆储库中的物质以晶粥为主,它们长时间处于固相线下的温度条件,属于冷储存状态.今天出露地表的大型侵入岩体,是古岩浆储库的代表,它们大都是在数百万年甚至更长的时间跨度内,多幕式的岩浆输运、累积侵位和多次添加组装而成的.侵入体的累积组装,可以通过岩石单元间接触关系的观察、岩石和矿物成分的不均一性研究以及侵入体内大的结晶时间跨度来证明.地壳浅部大型侵入体的形成,大体积的火山喷发,都要求存在穿地壳的岩浆通道系统,该系统中岩浆主要以岩墙形式将不同深度的岩浆储库串联起来,并通过无数岩床的堆垛而形成巨大的岩株或岩基等侵入体.高分异花岗岩和高硅流纹岩的存在,尤其是火山的超级喷发现象,要求岩浆储库的晶粥体发生活化和分异,而晶粥的解体往往是由于从下部侵入的新岩浆注入了额外的热和流体.保留在岩石中的晶体种群蕴含了侵入体累积组装、晶粥活化和岩浆分异的线索.尤其是再循环晶可以提供岩浆通道系统结构和演变的新信息.未来,在花岗岩成因研究中,重点要从晶粥活化与岩浆分异演化过程、岩浆上升和组装机制、火山岩与侵入岩的成因联系等方面入手,开展岩浆通道系统的跨学科研究,构建花岗岩岩浆过程研究的新范式,深入认识大陆地壳的生长和演化机理.      

卧龙湖煤矿岩浆侵入特征及控制因素分析

岩浆侵入对煤矿生产影响极大,淮北煤田卧龙湖煤矿是受岩浆侵入较严重的矿井之一,其地质构造是控制岩浆侵入和岩浆岩展布的重要因素。卧龙湖煤矿自侏罗纪以来岩浆活动剧烈,发生了中性岩浆的侵入,多以岩床形式顺层侵入煤层顶底板及煤层中间。本文基于矿区钻孔数据揭露的岩浆岩分布情况,分析了结果表明卧龙湖矿区岩浆侵入规律,受煤层的形态、结构、理化性质以及产状的控制。     

祁东煤矿岩浆侵入特征的研究

通过对祁东煤矿勘探钻孔统计资料分析．研究了岩浆侵入煤层的主要特征。岩浆主要以岩床的形式沿煤层侵入,岩性以云煌岩为主,岩床层数多为一层,岩浆主要是顺煤层上部侵入。从上部煤层到下部的10煤层,岩浆侵入活动呈现出从无到有、从弱到强的趋势;分布区域从西向东、由北向南扩展,分布面积逐渐扩大。岩浆侵入破坏了煤层的结构和稳定性,其接触变质作用造成煤类分布混杂,而仅靠钻孔不可能完全查明岩浆岩的分布形态,建议今后加强矿井地质观测,为煤炭开采提供服务。     

邢台显德江煤矿岩浆侵入体的特征及对煤层瓦斯的影响

本文对显德江煤矿岩浆侵入体的岩性、产状、分布特征、侵入方式、时代、形成温度及其侵入体与井田地质构造的关系等基本特征进行了论述，在此基础上分析讨论了侵入体对９＃煤层、煤质及其瓦斯的影响。     

淮南煤田朱集井田岩浆侵入特征研究

在对淮南煤田朱集井田钻孔资料分析的基础上,结合侵入岩化学成分测试、X-射线衍射分析以及薄片显微镜下鉴定等结果,得出研究区侵入岩主要以岩床的形式侵入煤系地层,岩性以闪长岩、花岗岩为主,岩床层数多为单层;受NWW—NW向断裂构造带控制,侵入岩体的分布范围呈现从西向东逐渐扩大,在垂向上,从上部煤层到下部煤层,受岩浆影响的程度有明显加大的态势。由于岩浆侵入煤层,严重破坏了煤层的结构和稳定性,同时,降低了煤的工业利用价值,加大了开采难度。     

花岗岩体的累积生长与高结晶度岩浆的分异

花岗岩成因研究是认识大陆地壳形成和分异的有效方式。野外地质和地球物理观测、岩石学和地质年代学研究以及热演化模拟证明,很多花岗岩体是在数百万年甚至更长的时间跨度内、由多次岩浆累积添加侵位而成的。地壳内可能不存在岩基尺度的大岩浆房,具有流动能力的岩浆体一般规模很小(宽度1000m)。1000m宽的岩浆体冷凝到固相线只需要数千年时间。复式岩体的形成一般要经历三个阶段,即源区岩浆沿岩墙的上升、在脆-韧性地层界面处岩墙转化为岩床以及无数的岩床的垂向堆垛导致侵入体长大。存在于上地壳的岩浆储库,特别是多次先后侵位产生的岩浆体,主体上是晶粥体,其晶体含量高,粘度大,活动性弱,不利于发生对流、分异和混合。当幔源镁铁质岩浆大规模注入到地壳时,使粘稠的晶粥状岩浆受到加热,熔体含量增大,岩浆的粘度降低,引起岩浆体内部的成分分异和不同成分的岩浆之间的混合;当逐渐加厚的熔体层产生了足够大的浮力后,特别是有挥发份加入后,就会快速上升,甚至穿透上部的晶粥体,触发大规模的火山喷发。幔源岩浆的通量越大,地壳岩浆的活动性也越强,大规模的长英质岩浆聚集就可能发生大喷发,形成超级火山。本文提出,只有将侵入岩与火山岩相结合、长英质岩石与镁铁质岩石相结合,重点从侵入体形成的时间长短、岩浆相互作用的规模和频率、岩浆通量的演变、高结晶度的岩浆分异机理、侵入岩与火山岩的关系、地幔热和物质的贡献、挥发份在岩浆分异和火山喷发中的作用等方面入手,开展野外地质、岩石学、地球化学、同位素年代学及岩浆动力学的综合研究,才能深入认识花岗岩的成因机制,深化对大陆地壳形成和演化过程的理解。     

卧龙湖煤矿岩浆蚀变煤层中汞的分布与赋存特征

系统采集淮北卧龙湖煤矿岩浆蚀变煤层中岩浆岩、煤及顶底板岩石样品,测试分析了样品中汞、灰分、挥发分、水 分以及各形态硫的含量,探讨了岩浆蚀变煤层中汞的分布与赋存特征。结果表明：（1） 岩浆侵入导致煤中灰分升高,挥发 分降低,煤中硫主要以黄铁矿硫和有机硫存在;（2） 岩浆侵入导致煤中汞的富集,卧龙湖煤矿岩浆蚀变煤层中汞的平均含 量高达0.23×10-6,是华北石炭-二叠纪煤、中国煤以及美国煤中汞的平均含量的1.4 倍,1.2 倍和1.3 倍;（3） 煤中汞的含量 随离岩浆侵入体距离增大有逐渐降低的趋势,但在煤岩接触带附近,汞在岩浆侵入体上方和下方的煤中呈现不同的分布特 征;（4） 煤中的汞主要以无机结合态的形式存在,且大部分赋存在煤中的黄铁矿中,同时亦存在与有机硫结合的汞。岩浆 热液对煤层的侵入,导致煤质以及煤中汞的含量和赋存方式发生了显著变化。     

中国岩浆硫化物矿床新分类与小岩体成矿作用

中国镍(铜、钴)、铂族等许多重要金属矿产都产出于岩浆硫化物矿床,该类矿床是矿床地质研究的热点之一。笔者综合构造背景、侵入方式、岩体规模、矿床模式、主成矿元素等因素,对中国岩浆硫化物矿床提出了新的分类:①古大陆内的小侵入体矿床;②与大陆溢流玄武岩有关的侵入体矿床;③造山带内小侵入体矿床;④蛇绿岩型矿床。认为小侵入体(小岩体)岩浆矿床是中国主要的矿床类型,并在此基础上,从小岩体矿床的相关概念、3种地质背景、3种火山岩_岩体_矿床组合形式以及成矿的主要因素等方面详细阐述了小岩体成矿作用。结合国内外勘查实践指出,小岩体岩浆矿床仍具有很大的找矿潜力,是中国应继续重点研究的主要矿床类型。最后,还讨论了小岩体矿床不仅在基性_超基性岩体中广泛发育,而且在中酸性岩体中也具有重要的经济价值和研究意义。     

Quaternary Intrusions from the Zhongjiannan Basin, South China Sea: Their Relationship with the Hainan Mantle Plume and Influence on Hydrocarbon Reservoirs

The transportation of magma in sedimentary basins often occurs through extensive dyke-sill networks. The role of sills on the plumbing system in rifted margins and the impact of sills on hydrocarbon reservoirs of prospective sedimentary basins has long been an area of great industrial interest and scientific debate. Based on 2D seismic reflection, we present data on how the sills emplaced to form a magmatic plumbing system of the volcanic system for the Zhongjiannan Basin(ZJNB). The results show...     

沉积盆地火成构造研究综述

岩浆活动在沉积盆地中是非常广泛的.随着油气勘探领域的扩展,对沉积盆地火成岩及相关构造的研究愈加重要.沉积盆地火成构造是指在沉积盆地中由岩浆侵入或喷发作用形成的岩浆和围岩及上覆层变形构造的总和.当前,利用三维地震数据研究岩席的几何学与侵位机制取得了重要进展,开启了沉积盆地火成构造研究的新时代.三维地震分析是沉积盆地火成构...     

Fingered Intrusion of Shallow Saucer-shaped Igneous Sills: Insights from the Jiaojiang Sag, East China Sea

An extensive suite of igneous sills was intruded into the Tertiary sedimentary section of the Jiaojiang sag,East China Sea.This suite has been well imaged offshore through 2D and 3D seismic surveys,showing a close relationship with CO2 content in nearby gas discoveries.A new observational model,which incorporates simple upward propagation,simple horizontal propagation,and transgressive propagation,was proposed to interpret these sill intrusions.In this model,the source magma of the saucer-shaped sills was injected from their lowest points near the center.The transgressive propagation can be interpreted as a combination of the vertical and horizontal propagation.Most shallow sub-volcanic intrusions in the Jiaojiang sag exhibit fingered characteristics,both vertically and horizontally.The vertical fingered propagation produced saucer-shaped sills arranged in the flower style.Along the brims of lower sills could usually be found the upper sills,which are interpreted to have formed simultaneously with or later than the lower feeder sills.In the second type,the chilled paths of the older sills were reutilized by subsequent intrusions.The horizontal fingered propagation formed sheet intrusions that exhibit groove,lobate,tubular,and crevasse splaylike geometry in plan view.In 3D view,the sheet intrusions have still preserved the lower center and higher rim that similar with the sub-rounded saucer-shaped sills.Although fracture propagation may be important,flow inflation was the key mechanism of magma intrusion.Further consideration of the mechanisms underlying sill formation may help explain the fingered characteristics of sill propagation.     

Granite magma migration and emplacement along thrusts

This paper investigates the influence exerted by brittle tectonic structures in the emplacement of granite plutons in contractional settings. We address both cases where contractional tectonics and magma intrusion are (1) coeval, to study how active contractional tectonics controls the transport of magma, and (2) diachronous, to study the role of pre-existing structures on the transport of magma. In light of new experimental models, we show that magma can rise along thrusts ramps and flats. This phenomenon occurs for both low-viscosity magma (basalts to andesite) and high-viscosity magma (dry granite). The experimental results also allow the evaluation of the role played by magma viscosity in determining pluton geometries. In addition, a review of literature demonstrates a spatial and causal relationship between granites and thrusts and highlights the geometric control of magma pathways in the pluton final shape. The abundance of subhorizontal and tabular granitic intrusions indicates that the location of inflating granitic sills along thrust flats can be common. We argue that active and pre-existing flats-and-ramps thrusts provide a preferential continuous planar anisotropy susceptible to become a granitic magma migration pathway.     

Occurrence and Dispersal of Magmas in the Jurassic Ferrar Large Igneous Province, Antarctica

Tholeiitic rocks of the Ferrar Large Igneous Province (FLIP) occur in a linear belt from the Theron Mountains to Horn Bluff in the Transantarctic Mountains and extend into southeastern Australasia. The FLIP was emplaced during the initial stages of Gondwana break-up from a source suggested to be in the proto-Weddell Sea region. Magma transport from its source (Weddell triple junction) was controlled by an Early Jurassic zone of extension. The FLIP comprises the Dufek intrusion, Ferrar Dolerite sills and dykes (sheet intrusions), and extrusive rocks consisting of pyroclastic strata overlain by Kirkpatrick Basalt lavas. The Dufek intrusion occurs in deformed supracrustal rocks of the foldbelt along the paleo-Pacific Gondwana margin. A few sills were emplaced in basement rocks, but the majority of the sheet intrusions occur in flat-lying Devonian to Triassic Beacon strata. Only in the central Transantarctic Mountains (CTM) and south and north Victoria Land (SVL, NVL) are extrusive rocks preserved overlying Beacon strata. The greatest cumulative thicknesses of magmatic rocks (ca. 2 km) occur in areas where lavas are preserved (CTM and SVL). Sheet intrusions have complex relationships. Dyke swarms (sensu stricto) are unknown and dykes cutting basement rocks are uncommon. Nevertheless, these dykes, including a 30-m-wide dyke in SVL, suggest that some magmas locally migrated up through basement rocks. In CTM and NVL the outcrop belt has a width of about 160 km. Sills originally extended farther toward the plate margin but have been cut out by erosion and Cenozoic faulting, most clearly in CTM; geophysical data suggest extension under the East Antarctic ice sheet for at least 100 km. Although Early Jurassic extension is documented in CTM, major rift-bounding faults have not been observed. Models for magma emplacement include transport along the axis of the Transantarctic Mountains and off-axis transport from major rift-bounding faults. Contrasts in geochemistry between lavas of NVL (MgO=67%) and CTM (MgO=24%) and the presence of massive dolerite bodies (CTM, SVL) suggest discrete episodes and locations of magma emplacement, and that there was no long range interconnection along the mountain range in supracrustal rocks.     

Mechanics of growth of some laccolithic intrusions in the Henry mountains, Utah, I: Field observations, Gilbert's model, physical properties and flow of the magma

The shapes of sills and laccolithic intrusions and associated host rock deformation were studied at several locations on the flanks of the Henry Mountains. Diorite sills range from 0.5 to 10 m in thickness, are less than 1 km² in areal extent, and have blunt terminations. The laccolithic intrusions range from 10 to 200 m in thickness, and from 1 to 3 km² in areal extent. The host rock, principally sandstone and shale, is deformed along closely spaced cataclastic shear planes. This deformation is concentrated at contacts, especially near sill terminations and over laccolith peripheries. The diorite contains plagioclase phenocrysts which are usually sheared in a thin zone adjacent to each contact. Field observations suggest that sills are the forerunners of laccolithic intrusions which form only after magma has spread far enough laterally (greater than about 1 km² in the Henry Mountains) to gain leverage to bend the overburden upward. Further injection of magma results in laccolithic peripheries or terminations with one of three distinct cross-sectional forms: (1) blunt termination of the diorite accompanied by bending and minor faulting of the host rock; (2) termination at a peripheral diorite dike cutting upward across the host rock; or (3) abrupt termination of the diorite against a nearly vertical fault zone.In order to study some of the processes of sill and laccolith intrusion, mechanical models for the driving pressure, physical properties, and flow behavior of the diorite magma are derived and discussed. A static driving pressure (equal to the difference between total magma pressure and lithostatic pressure) of up to 700 bar is estimated. The rheological behavior of the magma in the Henry Mountains is unknown. However, flow behavior is calculated assuming three of the more common models for fluids: Newtonian viscous, pseudoplastic, and Bingham. Suspended crystals probably contributed to the finite strength of the magma (estimated to be at least 10³ dyn/cm² for the Henry Mountains magma) which enables it to support dense zenoliths and also fixes maximum limits on the lengths of sills or dikes. Pressure in magma flowing along tabular intrusions of uniform thickness drops linearly in the flow direction for all three rheological materials. Thickening of tabular intrusions tends to make the pressure drop less rapidly, but pressure drops more rapidly in the tapered region near a termination. Pressure distributions under these and other conditions are derived in order to use them in the models of host rock deformation presented in Part II.     

Tectonic Controls on Ore-Bearing Intrusions of the Talnakh Ore Junction: Position,Morphology, and Ore Distribution

Analysis of fifteen hundred deep boreholes permits understanding of Noril'sk-type, ore-bearing intrusions with respect to stratigraphic position, thickness, and ore distribution, and provide insights into the evolution of the Talnakh and Noril'sk ore junctions. Weakly miner-alized, Lower Talnakh-type intrusions were emplaced early in each ore junction, followed by emplacement of the ore-bearing intrusions. The morphology of the Lower Talnakh-type intrusions appears to have been controlled largely by inferred, arcuate faults; tight, N-S-trend-ing folds in the Noril'sk-Kharaelakh fault zone; and pre- Tungusskaya anticlines. The spreading and morphology of the ore-bearing intrusions were influenced by these features, but were more strongly controlled by the Noril'sk-Kharaelakh fault zone and by arcuate, thickened lenses within the Lower Talnakh-type intrusions. Host-rock characteristics strongly influenced the shapes of the ore-bearing intrusions in section and plan, the configurations of their flanking and frontal parts, and the attitudes of their peripheral sills.     

Deformation structures associated with the Trachyte Mesa intrusion,Henry Mountains,Utah: Implications for sill and laccolith emplacement mechanisms

Deformation structures in the wall rocks of igneous intrusions emplaced at shallow crustal depths preserve an important record of how space was created for magma in the host rocks. Trachyte Mesa, a small Oligocene age intrusion in the Henry Mountains, Utah, is composed of a series of stacked tabular, sheet-like intrusions emplaced at 3–3.5 km depth into sandstone-dominated sedimentary sequences of late Palaeozoic–Mesozoic age. New structural analysis of the spatial distribution, geometry, kinematics and relative timings of deformation structures in the host rocks of the intrusion has enabled the recognition of distinct pre-, syn-, and late-stage-emplacement deformation phases. Our observations suggest a two-stage growth mechanism for individual sheets where radial growth of a thin sheet was followed by vertical inflation. Dip-slip faults formed during vertical inflation; they are restricted to the tips of individual sheets due to strain localisation, with magma preferentially exploiting these faults, initiating sill (sheet) climbing. The order in which sheets are stacked impacts on the intrusion geometry and associated deformation of wall rocks. Our results offer new insights into the incremental intrusion geometries of shallow-level magmatic bodies and the potential impact of their emplacement on surrounding host rocks.     

Characteristics of Meso-Cenozoic Igneous Complexes in the South Yellow Sea Basin, Lower Yangtze Craton of Eastern China and the Tectonic Setting

The South Yellow Sea Basin is partially surrounded by the East Asian continental Meso-Cenozoic widespread igneous rocks belt. Magnetic anomaly and multi-channel seismic data both reveal the prevalent occurrence of igneous rocks. We preliminarily defined the coupling relation between magnetic anomalies and igneous rock bodies. Some igneous complexes were also recognized by using multi-channel seismic and drilling data. We identified various intrusive and extrusive igneous rock bodies, such as stocks, sills, dikes, laccoliths and volcanic edifice relics through seismic facies analysis. We also forecasted the distribution characteristics of igneous complexes. More than fifty hypabyssal intrusions and volcanic relics were delineated based on the interpretation of magnetic anomaly and dense intersecting multi-channel seismic data. It is an important supplement to regional geology and basin evolution research. Spatial matching relations between igneous rock belts and fractures document that extensional N–E and N–NE-trending deep fractures may be effective pathways for magma intrusion. These fractures formed under the influence of regional extension during the Meso-Cenozoic after the Indosinian movement. Isotopic ages and crosscutting relations between igneous rock bodies and the surrounding bedded sedimentary strata both indicate that igneous activities might have initiated during the Late Jurassic, peaked in the Early Cretaceous, gradually weakened in the Late Cretaceous, and continued until the Miocene. Combined with previous studies, it is considered that the Meso-Cenozoic igneous activities, especially the intensive igneous activity of the Early Cretaceous, are closely associated with the subduction of the Paleo-Pacific Plate.