鄂尔多斯盆地三水河剖面上三叠统块状砂岩的异重流成因——来自岩石结构的证据

由于储层质量好、非均质性弱、成藏条件优越,深水沉积中的块状砂岩常常成为油气勘探开发的重要目标。相对具有各种交错层理等沉积构造的其他砂岩而言,块状砂岩的成因判识难度更大。因此,对块状砂岩成因机制的研究,直接影响了其沉积过程的认识,制约了其沉积模式、储层预测地质模型的重建。针对鄂尔多斯盆地南部旬邑县三水河剖面中发育的晚三叠世中层—巨厚层块状砂岩,利用高密度岩石样品的岩石薄片和激光粒度分析,对块状砂岩的粒度组成、粒度参数及其垂向变化特征进行研究。结果表明: 1）块状砂岩为长石岩屑质极细砂—细砂岩,内部偶含漂浮状灰黑色、红褐色泥砾,底部发育球枕、沟模等沉积构造;2）块状砂岩之间及其与交错层理砂岩层之间夹薄层—极薄层灰黑色泥岩、油页岩,二者间突变接触常见;3）岩石薄片中碎屑颗粒分选差,呈棱角—次棱角状,成分及结构成熟度中等偏低;4）粒度组成上,跳跃组分与悬浮组分各占50%左右,显示底床载荷与悬浮载荷同时存在且贡献相当;5）其偏度与浊流沉积相似,但其分选略差于浊流沉积,与三角洲沉积相差更远;6）垂向上,块状砂岩内部存在多期分米级复合韵律,厚度范围为10~30 cm。综合研究区地质背景、沉积构造、微观显微结构、粒度组成及其搬运过程、沉积分异解释结果,认为该剖面块状砂岩为洪水成因的异重流沉积。该研究丰富了对深水块状砂岩成因的理解,深化了异重流沉积块状砂岩结构特征的认识,同时也为异重流沉积的判识提供了依据。     

Envelope structure in T Tauri binary stars with subsonic orbital motion of one component

Results of numerical modeling of the gas dynamics ofmaterial in the envelopes of T Tauri binary stars with a small component mass ratios (q = 0.08) are reported. In such systems, the less massive component is moving at a supersonic velocity, and the more massive component can move with either a subsonic or supersonic velocity. The modeling results show that the morphology of the flow changes substantially in the transition from supersonic to subsonic motion of the massive component. In particular, one of the two bow shocks vanishes, flows ofmaterial in the system are redistributed, and the characteristics of the accretion disks change. In addition, the effect of the change in the accretion mode on the evolution of the binary system and the possibility of recovering some parameters of the system from observational manifestations of shocks in the circumstellar envelope are considered.     

闽西南地区块状硫化物矿床的喷流-沉积成矿作用

通过对闽西南地区石炭纪—早二叠世主要块状硫化物矿床的区域成矿背景、贮矿层位特征以及矿石矿物成分、结构构造,硫同位素地球化学特征、成矿温度等分析研究,指出该地区石炭纪—早二叠世块状硫化物矿床的形成多与海底火山活动有关,贮矿层中伴有典型的喷流沉积岩—硅质岩,并提出闽西南地区块状硫化物矿床存在海底喷流-沉积成矿作用的新认识。     

The Herbig Be Star IL Cep A as a Long-Periodic Spectroscopic Binary

The results of long-term spectral monitoring of the Herbig Be star IL Cep A are presented. A smooth variation in the parameters of the Нα and Нβ line emission component has been discovered. The helium absorption lines He I λ4922 and 5876 Å show seasonal changes, however, these changes do not correlate with changes in hydrogen emission. The radial velocities of the narrow lines D Na I and DIB λ5780, 5796 Å correspond to that of the interstellar medium. The hydrogen emission lines are apparently formed in a triple system, including a close pair of B stars and a remote low-mass K–A component. The orbital elements of this system were calculated using an approximate spectral binary model, where a close pair of massive B stars was considered as one massive component. The rationale for this approach for determining the elements of the orbit is given. The orbital period P = 3550 ± 28 days is determined and some other parameters of the orbit are estimated.     

The minimum stellar mass in early galaxies

The conditions for the fragmentation of the baryonic component during mergers of dark matter halos in the early Universe are studied. We assume that the baryonic component undergoes a shock compression. The characteristic masses of protostellar molecular clouds and the minimum masses of protostars originating in these clouds decrease with increasing halo mass. This may indicate that the initial stellar mass function in more massive galaxies was shifted towards lower masses during the initial stages of their formation. This would result in an increase in the number of stars per unit mass of the halo, i.e., in an increase in the efficiency of star formation.     

冲绳海槽Jade热液活动区块状硫化物的铅同位素组成及其地质意义

新测行Ｊａｄｅ热液活动区中５件块状硫化物样品的铅同位素组成,具有较小的变化范围,表现出较均一的铅同位素组成特征。在Ｐｂ－Ｐｂ图解上,块状硫化物的铅同位素数据构成线形排列,与该区沉积物和蚀变火山岩的铅同位素组成一致,而与该区新鲜火山岩相比具较高的放射成因铅,证实了该区海底块状硫化物中的铅是由沉积物长英质火山岩来源铅共同构成的混合铅。不同热液活动区铅同位素组成对比研究表明,地质－构造环境的不同是导致各     

Seismic earth thrust against massive building walls

The problem of earth thrust for a massive building in a seismic environment is analysed. Intertial and kinematic soil-structure interactions are considered by modelling the soil and the structure together. The problem is solved in the frequency domain by using the computer code FLUSH. Results show that the horizontal component of the seismic earth thrust is much greater than that obtained when applying the Mononobe-Okabe theory. This study establishes a set of conclusicns and recommendations for both design and practical purposes, and proposes future lines of investigation.     

含柯石英超高压榴辉岩的早期变形--以苏北东海碱场榴辉岩体为例

以超高压矿物组合的各种后成合晶及冠状体等卸载不平衡结构为参考标志，将含柯石英的超高压榴辉岩的交形序列分成两个部分。后成合晶及冠状体发育之前的变形为早期变形，是在大陆深俯冲和碰撞条件下发育的超高压变质变形组构。后成合晶及冠状体发育之后的变形为晚期变形，是在超高压岩石折返剥露过程中，主要是在角闪岩相甚至绿片岩相条件下发育的。构造上江苏省北部东海县碱场合柯石英榴辉岩体，分为块状榴辉岩和面理化榴辉岩两种类型，分别代表超高压变质岩早期变形的两个构造阶段或世代(D1、D2)。详细描述了它们的矿物组合、中小尺度及显微尺度下的组构特征，讨论了两者的几何关系和区域构造意义，强调指出，只有含柯石英榴辉岩的早期变形组构，才能记录和反映斜向大陆深俯冲及碰撞的动力学过程。     

Lead isotope systematics of the giant massive sulphide deposits in the Iberian Pyrite Belt

Lead isotope analyses were performed on 26 polymetallic massive sulphide deposits of the Iberian Pyrite Belt, as well as on overlying gossans and associated volcanic rocks. All the massive sulphide deposits (except for Neves-Corvo), and nearly all the volcanic rocks show very similar isotopic compositions grouped around 18.183 (²⁰⁶Pb/²⁰⁴Pb), 15.622 (²⁰⁷Pb/²⁰⁴Pb) and 38.191 (²⁰⁸Pb/²⁰⁴Pb), indicating that most of the ore deposit lead was derived from the same continental crust environment as the associated volcanic rocks. The isotopic compositions are representative of the average south Iberian crust during the Devonian to Early Carboniferous (Dinantian), and their constancy implies a homogenization of the mineralizing fluids before the deposition of the massive sulphides from hydrothermal fluids circulating through interconnected regional fracture systems. This isotopic constancy is incompatible with multiple, small, independent hydrothermal cells of the East Pacific Rise type, and fits much better with a model of hydrothermal convections driven by “magmatic floor heating”. Neves-Corvo is the only south Iberian massive sulphide deposit to have a heterogeneous isotopic composition with, in particular, a highly radiogenic stanniferous ore (²⁰⁶Pb/²⁰⁴Pb of the cassiterite is >18.40). A model of lead mixing with three components is proposed to explain these variations: (1) one derived from the Devonian to Early Carboniferous (Dinantian) continental crust that generated all the other massive ores; (2) an Eohercynian stanniferous mineralization partly remobilized during the formation of the massive sulphides, but independent of them; and (3) a Precambrian continental crust component. The juxtaposition of three different sources places Neves-Corvo in a specific paleogeographic situation that could also explain its mineralogical specificity. The geodynamic context that best explains all the obtained isotopic results is one of an accretionary prism. The fact that lead isotope signatures of the gossans are almost identical to those of the underlying massive sulphides means that this technique could be a useful exploration tool for the Iberian Pyrite Belt.     

Integration multisource data for mineral exploration by using fuzzy logic,case study: Taknar deposit,NE of Iran

The Taknar Zone is located at the northern margin of the eastern Iranian continental microplate, and it is host to the Taknar massive sulfide deposit. This study was conducted to find new exploration targets. We used multiple data sources (e.g., litho-geochemical and magnetic surveys) to produce more effective predictive maps. Principal component analysis and hierarchical cluster analysis methods were used to organize the new information into favorability maps and to determine multi-element correlations. We then employed fuzzy logic modeling to create favorability maps from geochemical and magnetic data. A concentration–area multifractal method was used to evaluate the final integrated favorability map for massive sulfide exploration. Our new map identifies previously unexploited sites in the eastern part of the study area, near the boundary of the Taknar formation, with intrusive and subvolcanic rocks, with potential for mineral exploration. The newly defined targets are attractive because old mined ore bodies are also identified in the favorability map.     

The evolutionary status of the most massive WNh stars in close binary systems. NGC 3603-A1

The evolution of the components of the unique, massive, close binary system NGC 3603-A1, which consists of stars of spectral types WN6ha and WN6h, is analyzed. The component masses are estimated to be 116 and 89M _⊙, close to the highest measured stellar masses. Numerical modeling of the evolution of the components has been carried out, taking into account mass loss via the stellar winds of the two massive stars. It is shown that the maximum possible initial component masses are close to 140 and 125M _⊙. The components are currently slightly evolved main-sequence stars, with a comparative low degree of helium enrichment at their surfaces. Further evolution of the system will lead to filling of the Roche lobe of the primary and subsequent evolution in a common envelope. This may lead to the merger of the components, with the evolution of the system ending in the formation of a singlemassive black hole after the second supernova explosion. Otherwise, depending on the masses of the resulting black holes, either a binary system of two black holes or two unbound black holes may form, accompanied by gamma-ray bursts.     

The luminosity excess of OB stars in quasi-stationary X-ray binaries

We have found a mass—luminosity relation for the OB components of massive X-ray binaries that is a good estimator of the masses of these evolutionarily important binaries. Analysis of this relation showed a systematic luminosity excess of ≈1^m for the OB components in these systems. No such excess was discovered for the evolutionarily related WR + O binaries, which also undergo mass exchange between their components and are the immediate precursors of X-ray binaries. A study of possible origins of the luminosity excess suggests that the most likely explanation is an X-ray luminosity related selection effect for massive X-ray binaries. Estimates show that the probability of detecting X-ray binary increases due to the enhancement of the stellar wind, which increases the efficiency of accretion by the relativistic companion while the optical component evolves along the main sequence. This can explain the magnitude of the observed luminosity excess and the position of the optical components of X-ray binaries in the luminosity—radius plane.     

Mg–Fe carpholites from aluminous schists in the Diahot region and implications for preservation of high-pressure/low-temperature schists, northern New Caledonia

Abstract Mg–Fe carpholite is widespread in the Diahot region of New Caledonia in highly aluminous schists and as veins in what was originally a clay-rich hydrothermal alteration envelope about massive suphide deposits. These carpholites have Fe/(Fe + Mg) ratios of 0.03–0.65 and no significant Mn component. Mg-carpholite + quartz occur in assemblages with chlorite or pyrophyllite, pyrophyllite + kaolinite and pyrophyllite + diaspore. Temperatures of 230–320° C and minimum pressures of 7 kbar are indicated for the Mg–Fe carpholite-bearing rocks. The regional distribution of aragonite and Mg–Fe carpholite parallel to a major zone of dominantly transcurrent movement and oblique to the trend of the subduction complex indicates the high- P /low- T schists owe their rapid uplift and preservation to the vertical component of the transcurrent faulting.     

The Key Tuffite,Matagami Camp,Abitibi Greenstone Belt,Canada: petrogenesis and implications for VMS formation and exploration

The Key Tuffite is a stratigraphic marker unit for most of the zinc-rich volcanogenic massive sulfide deposits of the Matagami Camp in the Abitibi Greenstone Belt. This 2- to 6-m-thick unit was previously interpreted as a mixture of ash fall (andesitic to rhyolitic tuffaceous components) and volcanogenic massive sulfide (VMS)-related chemical seafloor precipitate (exhalative component). Previous attempts to develop geochemical exploration vectoring tools using metal content within the Key Tuffite were mostly inconclusive due to the complex nature of the Key Tuffite unit and a poor understanding of its composition, origin and relationship with the VMS-forming hydrothermal systems. Detailed mapping and thorough lithogeochemistry of the Key Tuffite in the vicinity of the Perseverance and Bracemac-McLeod deposits indicate that the Key Tuffite is a homogeneous calc-alkaline, andesitic tuff that was deposited before the VMS deposits were formed. The unit is mostly devoid of exhalative component, but it is strongly hydrothermally altered close to orebodies. This is characterized by a strong proximal chloritization and a distal sericitization, which grades laterally into the unaltered Key Tuffite. Neither the Key Tuffite nor the ore was formed by seafloor exhalative processes for the two studied deposits. This probably explains why previously proposed exploration models based on metal scavenging proved unsuccessful and suggests that a re-evaluation of the exhalative model should be done at the scale of the mining camp. However, as shown in this study, hydrothermal alteration can be used to vector towards ore along the Key Tuffite.     

东秦岭刘山岩块状硫化物矿床地质地球化学特征

刘山岩铜锌矿位于河南省桐柏县城北西25km的桐柏山北麓，处于东秦岭造山带之北秦岭褶皱带核部。矿体赋存于纹层状硅质-钠长石岩层中，矿石具纹层状、原生角砾状构造等，自矿体中心向边缘存在黄铁矿-黄铜矿-方铅矿-重晶石-石英的相对矿物分带。异常的浓度与组分分带反映的是一定时间域内成矿作用的延续与变化，纵向与轴向上具相同的组分分带，由中心至边缘的组分分带为Cd、Ge、Bi、As、Ga、Cu、Mo、Zn、Pb、Ag、Ba、Mn、V、W。根据异常元素组合、强度及其比值可以判断矿体剥蚀程度。重要的是，湿热条件下块状硫化物矿床赋矿岩系水系沉积物中成矿元素的贫化率极高，充分运用海底火山喷流相模式和圈定微弱、局部地球化学异常是勘查工作的根本手段。     

火山成因块状硫化物矿床研究进展

火山成因块状硫化物（VMS）矿床可形成于太古宙至现代各个地质时期.现代海底热液成矿作用是赋存于海相火山岩系中的古代VMS矿床成矿作用的再现.VMS矿床可形成于多种构造环境,但均与拉张背景有关.按照构造环境和容矿岩系将VMS矿床分为黑矿型、塞浦路斯型、别子型和沙利文型.VMS矿床的热液蚀变由下盘蚀变带和上盘蚀变带两个结构单元组成.下盘蚀变一般有两种类型：（1）不整合的蚀变岩筒,直接产在块状硫化物带的下方;（2）半整合或层控的上盘蚀变带,并可以在区域范围内展布.与下盘蚀变类似,上盘蚀变也具有蚀变岩筒和半整合的蚀变带两种类型.成矿金属主要有两种可能的来源：（1）在岩浆侵入体和浅位岩浆房之上被加热的循环海水对含矿火山岩系及下伏基底物质的淋滤;（2）深部岩浆房挥发分通过释气作用直接释放.下渗的海水是成矿流体的主要来源,同时流体包裹体和稳定同位素资料显示岩浆流体对成矿流体系统亦有较大贡献.VMS矿床具有明显的金属分带现象,其金属序列组合从下至上依次为Fe→Fe-Cu→Cu-Pb-Zn→Pb-Zn-Ba,这种金属分带的演化反应了流体的演化和块状硫化物丘的生长机制.根据成矿流体温度变化而不断演化的4阶段成矿模式可以很好的解释经典丘堆式矿床的形成过程.     

The use of fluorine as a pathfinder for volcanic-hosted massive sulfide ore deposits

A multi-element geochemical study of the wall rocks of intermediate to felsic volcanic-hosted massive sulfide deposits was carried out to identify pathfinder elements which significantly enlarge the size of exploration targets. Drill core samples from the Crandon massive sulfide deposit in Wisconsin, and outcrop samples from the United Verde and Iron King deposits in Arizona, and from the Captains Flat, Mt. Costigan, and Wiseman Creek deposits in New South Wales, Australia were analyzed. Because anomalously high fluorine values have been described in several volcanic-hosted ore systems, fluorine was included in the study.All of the above deposits have patterns of fluorine enrichment around ore. Drill core samples from two noneconomic prospects within ten miles of the Crandon deposit contain background to only weakly anomalous fluorine values.At the large Crandon deposit (> 50 million tons of zinc, copper ore), fluorine enrichment extends approximately 320 m into the footwall rocks and at least 220 m into the hanging wall rocks. At the large United Verde deposit (> 50 million tons of copper, zinc ore), fluorine enrichment is recognizable in the footwall rocks at least 650 m from the ore. At the smaller Iron King deposit (five million tons production of zinc, lead, copper ore), fluorine enrichment extends for a distance of approximately 60 m into the footwall rocks. At the small deposits in New South Wales (< five million tons production of zinc, lead, copper ore), fluorine enrichment is easily recognizable, but with the samples collected, the limits of the anomalous patterns cannot be defined.Fluorine occurs in some hydrothermal systems unassociated with mineralization and is therefore not a specific signature of ore-forming processes. From the work completed, many massive sulfide deposits in volcanic rocks occur in hydrothermal systems which contain fluorine. On the basis of the data presented, if anomalously high fluorine values do exist in an exploration search area, the chances of finding a massive sulfide ore deposit are improved.Genetic models for volcanic-hosted massive sulfide ore deposits have concentrated on rock textures, alteration mineralogy, and geochemistry of the ore metals. From the data presented, fluorine should be considered as a component of massive sulfide systems in intermediate to felsic volcanic rocks, and should be considered as a possible complexing agent for the ore metals.     

The Teutonic Bore deposit,Western Australia: a lead isotope study of an ore and its gossan

The Teutonic Bore deposit occurs in an Archaean greenstone belt within the Eastern Goldfields Province of the Yilgarn Block in Western Australia. The ore is hosted by basaltic rocks and consists of a conformable massive sulfide lens underlain by a thick zone of pyritic stringer ore. The zone of oxidation reaches a depth of 90–100 m with the development of secondary copper sulfides. The lead isotopic compositions of six samples of massive sulfide, three mineral separates from the ore and eight gossan samples collected from the open cut were determined by standard mass-spectrometric techniques. Four of the massive sulfide samples, all three mineral separates and seven of the eight gossan samples have lead isotopic compositions identical to each other, within experimental error. These results confirm the findings of earlier studies that the lead isotopic signature of a massive sulfide ore is transferred to its gossan, and provide additional data suggesting the usefulness of lead isotopic determinations in ore prospect evaluation. The Teutonic Bore leads plot below the average global lead evolution curves for the uranogenic isotopes ²⁰⁶Pb and ²⁰⁷Pb, suggesting that the lead in the ore contains a significant mantle component. This feature of the isotopic data is consistent with the idea of a mantle plume origin of the Eastern Goldfields greenstone belts.     

Magnetite Dyke in Precambrian Banded Iron Formation,Singhbhum Craton,India: Mineralogical and Chemical Characteristics

Banded iron formation (BIF) of the Gorumahisani–Sulaipat–Badampahar (GSB) belt in Singhbhum Craton, India, consists predominantly of magnetite. This BIF is intruded by a magnetite dyke. The magnetite dyke is massive and compact with minor sulphide minerals while the host banded magnetite ore, a component of the BIF, shows thin lamination. The magnetite ore of the dyke is fine to medium grained and exhibits interlocking texture with sharp grain boundaries, which is different from the banded magnetite that is medium to coarse grained and show irregular martitised and goethitised grain boundaries. Relics of Fe–Ca–Mn–Mg‐carbonate and iron silicates (grunerite and cummingtonite) are observed in the banded magnetite. The intrusive magnetite is distinctly different in minor, trace and REE geochemistry from the banded magnetite. The banded magnetite contains higher amounts of Si, Al, Mn, Ca, Mg, Sc, Ga, Nb, Zr, Hf, Co, Rb and Cu. In contrast, the massive magnetite is enriched in Cr, Zn, V, Ni, Sr, Pb, Y, Ta, Cs and U with higher abundance of HREE. In the chondrite normalized plot, the massive magnetite shows a slight positive Eu anomaly while the banded ore does not show any Eu anomaly. Field disposition, morphology, mineralogy and chemistry show that the intrusive magnetite dyke is of igneous origin, while magnetite in BIF formed from a carbonate protolith through the process of sedimentation.