科学大洋钻探与深部生物圈

从深海钻探计划(DSDP)在20世纪70年代最早提出海洋沉积物中细菌活动性的证据到90年代大洋钻探计划(ODP)获得了令人信服的海底深部生物的存在证据，并成为即将启动的综合大洋钻探计划(IODP)的一个优先研究领域，深部生物圈成为科学大洋钻探近年来最为重大的发现之一，同时它也将有效地促进地球科学和生物学等其他学科的交叉。     

Sources and hydrothermal alteration of organic matter in Quaternary sediments: A synthesis of studies from the Central Gulf of California

Deep sea drilling in the Central Gulf of California, a young and active spreading centre, shows that the high heat flow typical of these regions causes extensive alteration of sediment organic matter, especially near sills and above magma chambers where hydrothermal activity is concentrated. Even on the nearby passive margin, where there are no sills, heat flow is moderately high and hydrocarbon generation has begun in immature sequences. Migrating light hydrocarbons are detected especially where hydrothermal activity is concentrated. Thermogenic methane is more widespread, though not in the passive margin bordering the spreading centre. Despite the incidence of hydrocarbon generation and migration, the amounts of hydrocarbons involved are relatively small and apparently do not lead to commercially significant accumulations of petroleum.The organic matter in these sediments is mostly marine because the Gulf of California generally has low runoff from land and highly productive surface waters. Turbidites rich in terrigenous organic material are locally abundant in the mainly pelagic section in the Guaymas Basin. The highest concentrations of organic matter are found in laminated diatomites deposited on the Guaymas passive margin within the oxygen minimum zone.     

A chlorine isotope study of DSDP/ODP serpentinized ultramafic rocks: Insights into the serpentinization process

Eight DSDP/ODP cores were analyzed for major ion concentrations and δ³⁷Cl values of water-soluble chloride (δ³⁷Cl_WSC) and structurally bound chloride (δ³⁷Cl_SBC) in serpentinized ultramafic rocks. This diverse set of cores spans a wide range in age, temperature of serpentinization, tectonic setting, and geographic location of drilled serpentinized oceanic crust. Three of the cores were sampled at closely spaced intervals to investigate downhole variation in Cl concentration and chlorine isotope composition.The average total Cl content of all 86 samples is 0.26 ± 0.16 wt.% (0.19 ± 0.10 wt.% as water-soluble Cl (X_WSC) and 0.09 ± 0.09 wt.% as structurally bound Cl (X_SBC)). Structurally bound Cl concentration nearly doubles with depth in all cores; there is no consistent trend in water-soluble Cl content among the cores. Chlorine isotope fractionation between the structurally bound Cl⁻ site and the water-soluble Cl⁻ site varies from − 1.08‰ to + 1.16‰, averaging to + 0.21‰. Samples with negative fractionations may be related to reequilibration of the water-soluble chloride with seawater post-serpentinite formation. Six of the cores have positive bulk δ³⁷Cl values (+ 0.05‰ to + 0.36‰); the other two cores (173-1068A (Leg-Hole) and 84-570) have negative bulk δ³⁷Cl values (− 1.26‰ and − 0.54‰). The cores with negative δ³⁷Cl values also have variable Cl⁻ / SO₄² ratios, in contrast to all other cores. The isotopically positive cores (153-920D and 147-895E) show no isotopic variation with depth; the isotopically negative core (173-1068A) decreases by ∼1‰ with depth for both the water-soluble and structurally bound Cl fractions.Non-zero bulk δ³⁷Cl values indicate Cl in serpentinites was incorporated during original hydration and is not an artifact of seawater infiltration during drilling. Cores with positive δ³⁷Cl values are most likely explained by open system fractionation during hydrothermal alteration, with preferential incorporation of ³⁷Cl from seawater into the serpentinite and loss of residual light Cl back to the ocean. Fluid / rock ratios were probably low as evidenced by the presence of water-soluble salts. The two isotopically negative cores are characterized by a thick overlying sedimentary package that was in place prior to serpentinization. We believe the low δ³⁷Cl values of these cores are a result of hydration of ultramafic rock by infiltrating aqueous pore fluids from the overlying sediments. The resulting serpentinites inherit the characteristic negative δ³⁷Cl values of the pore waters. Chlorine stable isotopes can be used to identify the source of the serpentinizing fluid and ultimately discern chemical and tectonic processes involved in serpentinization.     

Neptune: A marine micropaleontology database

Marine micropaleontology must in the future provide more precise chronologic and paleoenvironmental information, which in turn must be based on better, more consistent taxonomic and distributional data. Better tools for synthesis and standardization of this data are needed, as the ever expanding published literature is rapidly becoming unmanageable by purely manual compilation methods. The micropaleontology group at the ETH has developed a large relational database of marine microfossil data to partially meet this need. It currently contains biogeographic data on the distribution in Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) holes of nearly 8,000 species of Cenozoic planktonic foraminifera, radiolaria, diatoms and calcareous nannofossils. The database also includes full stratigraphic occurrence (range chart) data for these fossil groups from more than 100 selected Neogene holes. A particular feature of the database is that all sample information and species names in the original reports are linked to newly created, updatable, comprehensive age models and synonymy lists which reflect modern chronology and taxonomic usage. Searches of the database automatically make use of this information in producing reports. Species ' occurrences, including first and last occurrence information, can be further analyzed using external spreadsheet and statistics packages; plotted by mapping programs; or displayed by a new program which creates composite age-range charts.     

Palaeogeographical implications of CretaceousBenthic Foraminifera recovered by the Deep Sea Drilling project in the Western South Atlantic ocean

Albian/Cenomanian benthic foraminiferal faunas recovered by the DSDP in the western South Atlantic Ocean (Leg 36) are described and analyzed from the palaeogeographic and palaeo-environmental points of view. In doing this the author compares Leg 36 assemblages in the western South Atlantic Ocean with coeval benthic foraminiferal faunas recovered in the eastern South Atlantic Ocean (Leg 40) and in the eastern Indian Ocean (Legs 26 and 27). The specific composition of these assemblages, except for Leg 27, is virtually the same. Consequently, they are considered to indicate the same depositional water depth at all relevant sites studied, whether located in the Angola Basin, the northern flank of the Walvis Ridge, the eastern margin of the Falkland Plateau or on the Naturaliste Plateau. All the assemblages indicate shallow environments around 100 m and not exceeding 300–400 m in the deepest parts, corresponding to the inner shelf and the inner part of the outer shelf. By contrast the foraminiferal associations of Leg 27 (especially Site 259) indicate a greater depth, of the order of 200–600 m (but not exceeding 1000 m) corresponding to upper slope of Sliter & Baker (1972) and Sliter (1972). These bathymetrical conclusions are in remarkable accord with those of Sliter (1976), based on planktic Foramini fera of Leg 36.Late Cretaceous (Campanian-Maastrichtian) material with benthic Foraminifera was limited to two positive samples; however, these faunas indicate much the same palaeo-environment as do the planktic ones analyzed by Sliter (1976).     

South Equatorial Current (SEC) driven changes at DSDP Site 237, Central Indian Ocean, during the Plio-Pleistocene: Evidence from Benthic Foraminifera and Stable Isotopes

This study attempts to analyse paleoceanographic changes in the Central Indian Ocean (Deep Sea Drilling Project Site 237), linked to monsoon variability as well as deep-sea circulation during the Plio-Pleistocene. We used factor and cluster analyses of census data of the 34 most dominant species of benthic foraminifera that enabled us to identify five biofacies: Astrononion umbilicatulum–Uvigerina proboscidea (Au–Up), Pullenia bulloides–Bulimina striata (Pb–Bs), Globocassidulina tumida–Nuttallides umbonifera (Gt–Nu), Gyroidinoides nitidula–Cibicides wuellerstorfi (Gn–Cw) and Cassidulina carinata–Cassidulina laevigata (Cc–Cl) biofacies. Knowledge of the environmental preferences of modern deep-sea benthic foraminifera helped to interpret the results of factor and cluster analyses in combination with oxygen and carbon isotope values. The biofacies indicative of high surface productivity, resulting from a stronger South Equatorial Current (Au–Up and Pb–Bs biofacies), dominate the early Pliocene interval (5.6–4.5 Ma) of global warmth. An intense Indo-Pacific ‘biogenic bloom’ and strong Oxygen Minimum Zone extended to intermediate depths (1000–2000 m) over large parts of the Indian Ocean in the early Pliocene. Since 4.5 Ma, the food supply in the Central Indian Ocean dropped and fluctuated while deep waters were corrosive (biofacies Gt–Nu, Gn–Cw). The Pleistocene interval is characterized by an intermediate flux of organic matter (Cc–Cl biofacies).     

海平面变化的原因及结果

20世纪80年代初期以来,科学大洋钻探已累计完成了DSDP80、93、95和ODP133、143、 144、150、150X、166、174A、174AX、182、194等10多个与海平面变化有关的科学航次,在美国新泽西被动大陆边缘、澳大利亚东北部及南部被动大陆边缘、巴哈马台地、太平洋中西部平顶海山等地获得了大量的钻探资料。根据这些资料,建立了过去42 Ma来的海平面变化年表,确立了大陆边缘层序界面与全球海平面下降之间的成因联系,在估计全球海平面变化幅度方面取得进展。尽管如此,对全球海平面变化的幅度、机制及地层响应等基本问题的了解,还存在很大的不确定性。在综合有关文献基础上,对科学大洋钻探在海平面变化研究方面所取得的成就、存在的问题及发展方向进行简要介绍。     

Cyclic fluctuations of anoxia during Cretaceous time in the South Atlantic Ocean

The holes of the DSDP-IPOD program in the South Atlantic Ocean document two major anoxic events during Oxfordian to middle Albian times and secondly from late Cenomanian to Santonian times. The black shales formed during these two anoxic events differ in their rhythmicity and origin.During Lower Cretaceous time, the anoxic conditions resulted from the confined, euxinic nature of the basins. The rhythmicity of these black shales probably does not result from a global phenomenon (climatic or tectono-eustatic), but from local conditions resulting from the slender dimensions of the young ocean basin(s). The diversity and the diachroneity of the deposits from the south to the north precisely reflect the dynamics of the oceanic spreading.During Upper Cretaceous time, the anoxic conditions fluctuated in relation to a mid-water oxygen-minimum zone. The rhythmicity of black shale deposition seems to result from a global phenomenon, because of the widespread occurrence of the event. In the South Atlantic ocean, the cyclic fluctuations of anoxia were due to cyclic variations in the depth of the mid-water oxygen-minimum zone. There is no simple process to explain such rhythmicity. It probably results from the interplay of the three main variables which characterize the oceans at the time of the Cenomanian-Turonian boundary: the increased rate of sea floor spreading, high sea-levels and low water-circulation.     

Biotic effects of late Maastrichtian mantle plume volcanism: implications for impacts and mass extinctions

During the late Maastrichtian, DSDP Site 216 on Ninetyeast Ridge, Indian Ocean, passed over a mantle plume leading to volcanic eruptions, islands built to sea level, and catastrophic environmental conditions for planktic and benthic foraminifera. The biotic effects were severe, including dwarfing of all benthic and planktic species, a 90% reduction in species diversity, exclusion of all ecological specialists, near-absence of ecological generalists, and dominance of the disaster opportunist Guembelitria alternating with low O₂-tolerant species. These faunal characteristics are identical to those of the K–T boundary mass extinction, except that the fauna recovered after Site 216 passed beyond the influence of mantle plume volcanism about 500 kyr before the K–T boundary. Similar biotic effects have been observed in Madagascar, Israel, and Egypt. The direct correlation between mantle plume volcanism and biotic effects on Ninetyeast Ridge and the similarity to the K–T mass extinction, which is generally attributed to a large impact, reveal that impacts and volcanism can cause similar environmental catastrophes. This raises the inevitable question: Are mass extinctions caused by impacts or mantle plume volcanism? The unequivocal correlation between intense volcanism and high-stress assemblages necessitates a review of current impact and mass extinction theories.     

古代与现代火山成因块状硫化物矿床研究进展

    火山成因块状硫化物（VolcanogenicMas siveSulfide,简称VMS）矿床可见于前寒武纪至现代的各个地质时代。现代海底热液成矿作用为研究VMS矿床提供了一种新的途径,DSDP／ODP钻探资料揭示：①VMS矿床虽然可产生于不同环境,但均与张裂断陷有关。②成矿物质可能来源有 2种：一种是含矿火山岩系及下伏基底物质的淋滤;另一种是深部岩浆房挥发份的直接释放。③洋中脊海底热液循环呈双扩散对流模式。在有沉积物覆盖的洋中脊,热液循环更多地考虑流体与沉积物相互作用产生的效果。④从矿物组合的空间分布来看,热液硫化物堆积体上部以烟囱体为主,下部以块状硫化物为主,深部以网脉状硫化物为主,这在不同热液活动区似乎具有普遍性。
    VMS矿床的矿化模式反映的是一种热液成因,这种热液是深部（1～3 km）岩浆侵入所引起并通过海水在热穹隆之上循环产生的。VMS矿床的深入研究要求我们致力于发现新的矿产地,提高样品采集、分析技术,加强海底热液活动与构造、岩浆作用和环境演变的一体化研究。