Dynamics of intraseasonal sea level and thermocline variability in the equatorial Atlantic during 2002-03

Satellite and in situ observations in the equatorial Atlantic Ocean during 2002-03 show dominant spectral peaks at 40-60 days and secondary peaks at 10-40 days in sea level and thermocline within the intraseasonal period band (10-80 days). A detailed investigation of the dynamics of the intraseasonal variations is carried out using an ocean general circulation model, namely, the Hybrid Coordinate Ocean Model (HYCOM). Two parallel experiments are performed in the tropical Atlantic Ocean basin for the period 2000-03: one is forced by daily scatterometer winds from the Quick Scatterometer (QuikSCAT) satellite together with other forcing fields, and the other is forced by the low-passed 80-day version of the above fields. To help in understanding the role played by the wind-driven equatorial waves, a linear continuously stratified ocean model is also used. Within 3 degrees S-3 degrees N of the equatorial region, the strong 40-60-day sea surface height anomaly (SSHA) and thermocline variability result mainly from the first and second baroclinic modes equatorial Kelvin waves that are forced by intraseasonal zonal winds, with the second baroclinic mode playing a more important role. Sharp 40-50-day peaks of zonal and meridional winds appear in both the QuikSCAT and Pilot Research Moored Array in the Tropical Atlantic (PIRATA) data for the period 2002-03, and they are especially strong in 2002. Zonal wind anomaly in the central-western equatorial basin for the period 2000-06 is significantly correlated with SSHA across the equatorial basin, with simultaneous/ lag correlation ranging from-0.62 to 0.74 above 95% significance. Away from the equator (3 degrees-5 degrees N), however, sea level and thermocline variations in the 40-60-day band are caused largely by tropical instability waves (TIWs). On 10-40-day time scales and west of 10 degrees W, the spectral power of sea level and thermocline appears to be dominated by TIWs within 5 degrees S-5 degrees N of the equatorial region. The wind-driven circulation, however, also provides a significant contribution. Interestingly, east of 10 W, SSHA and thermocline variations at 10 40- day periods result almost entirely from wind-driven equatorial waves. During the boreal spring of 2002 when TIWs are weak, Kelvin waves dominate the SSHA across the equatorial basin (2 degrees S-2 degrees N). The observed quasi-biweekly Yanai waves are excited mainly by the quasi-biweekly meridional winds, and they contribute significantly to the SSHA and thermocline variations in 1 degrees-5 degrees N and 1 degrees-5 degrees S regions.

西南极南设得兰群岛中新生代火山岩基底沉积学及其大地构造制约

Livingston Island, the second island of South Shetland Island, constains Mesozoic-Cenozoic basement, Mesozoic-Cenozoic volcanic sequences, plutonic intrusions and post-subduction volcanic rocks, which document the history and evolution of an important part of the South Shetland Islands magmatic arc. The sedimentary sequence is named the Miers Bluff Formation (MBF) and is interpreted as turbidite since the first geological study on South Shetland Islands, and is interpreted as turbidite. It base and top are not exposed, but a thickness of more than 3000m has been suggested and seems plausible. The turbidite is overlain by Mid - Cretaceous volcanic rocks and intruded by Eocene tonalites. The age of the Miers Bluff Formation is poorly constrained Late Carboniferous -Early Triassic. Sedimentary Environment, tectonic setting and forming age of sedimentary rocks of the Miers Bluff Formation were discussed by means of the methods of sedimentology, petrography and geochemistry, combinig with the study of trace fossils and microfossil plants. The following conclusions are obstained. A sedimentary geological section of Johnsons Dock is made by outside measuring and watching, and then according the section, the geological map near the Spanish Antarctic station was mapped. Four pebbly mudstone layers are first distinguished, which thickness is about 10m. The pebbly mudstone is the typical rock of debris flow, and the depostional environment of pebbly mudstone may be the channel of mid fan of submarine fan. The sedimentsry structural characteristics and size analysis of sandstones show the typical sedimentary feature of turbidity flow and the Miers Bluff Formation is a deep-water turbidite (include some gravity-flow sediments). The materials of palaeocurrents suggest the continental slope dip to southeast, and indicate the provenance of turbidity sediment in the northwest area. By facies analysis, six main facies which include seven subfacies were recognized, which are formed in mid-fan and lower-fan of submarine, meanwhile, the sedimentary features of each facies and subfacies are summarized. The study of clastic composition, major elements, trace elements and rare earth elements indicates the forming setting of the Miers Bluff Formaton is active continental margin and continental island arc and the provenance is dissected magmatic arc which main composition is felsic gneiss. Many trace fossils of the whole succession were found in the turbidites of the Miers Bluff Formation. All these trace fossils are deep sea ichnofossils. There are fifteen ichnogenus, sixteen ichnospecies. Moreover, a new trace fossil was found and a new ichnogenus and new ichnospecies was proposed - Paleaichnus antarctics ichnogen, et ichnosp, nov.. Except the new ichnogenus and ichnospecies, others had been found in deep-sea flysch turbidites. Some are in mudstone and are preserved in the cast convex of overlying sandstone sole, they formed before turbidity flows occurred and belong to the high-different Graphoglyptida of fiysch mudstone. Others as Fucusopsis and Neonereites are preserved in sandstones and stand for trace assemblages after turbidity sedimentation. These trace fossils are typical members of abyssal "Nereites" ichnofacies, and provide for the depositional environment of the Miers Bluff Formation. Fairly diverse microfossil plants have been recovered from the Miers Bluff Formation, Livingston Island, including spores, pollen, acritarchs, wood fragments and cuticles. Containing a total of about 45 species (forms) of miospores, the palynofiora is quantitatively characterized by the dominance of non-striate bisaccate pollen, but spores of pteridophytes and pollen of gymnosperms are proportionate in diversity. It is somewhat comparable to the subzone C+D of the Alisporites zone of Antarctica, and the upper Craterisporites rotundus zone and the lower Polycingulatisporites crenulatus zone of Australia, suggesting a Late Triassic (possibly Norian-Rhaetian) age, as also evidenced by the sporadic occurrence of Aratrisporites and probable Classopollis as well as the complete absence of bisaccate Striatiti. The parent vegetation and paleoclimate are preliminarily deduced. At last, the paper prooses the provenance of sedimentary rocks of the Miers Bluff Formation locates in the east part to the southern Chile(or Southern South American). In the Triassic period, contrasting with New Zealand, Australia and South American of the Pacific margin of Gondwanaland, the Miers Bluff Formation is deposited in the fore-arc basin or back-arc basin of magmatic arc.

流体地球化学：成因、流动和流体-岩石相互作用及塔里木盆地实例研究

Geofluid in sedimentary basins is related to petroleum generation, migration, accumulation and preservation, and is a topic of geological frontier. By integrating the multi-discipline methods of petroleum geochemistry, sedimentology, hydrogeology, petroleum geology and experimental geochemistry, the thesis has carried out experiments of microcline dissolution in solutions with organic acids, crude oil, brines with high total dissolved solids (TDS), and has dealt with Al distribution between the crude oil and the brines after the experiments. Cases for study includes Central Tarim, Hetianhe Gas Field and Kucha forland basin with data containing fluid chemistry and isotopic compositions, thin sections of sandstones and carbonates, homogenization temperatures and salinities of fluid inclusions, isotopic compositions of bulk rock and autigenic minerals. The aims are to elucidate fluid origin and flow in the three areas, effect of hydrocarbon emplacement on diagenesis, and to show occurrence of microbe-mediated, and thermochemical sulfate reduction in the Tarim Basin. Microcline dissolution experiments show that after 100 hour, part of the dissolved Al distributes in the crude oil, and the Al concentrations in the crude oil rise when organic acids are added. The result can be used to explain that most oilfield waters in the Tarim Basin are characterized by less than 3mg/L Al. Crude oil added to the solutions can enhance microcline dissolution, which is also observed in the case - Silurian sandstones with early crude oil emplacement in the Central Tarim. Al and Si have higher concentrations in the experiments of oxalic acid than of acetic acid under the same pH conditions, suggesting that there exist Al-oxalate and Si-oxalate complexes. Presence of acetate can enhance the activity of Ca and Al, but Al concentrations have not been increased significantly due to formation of small Al-acetate complex during the experiments. Relationships between δD and δ~(18)O in conjunction with chemistry of oilfield waters show that the waters are evaporated connate waters, which subsequently mixed with meteoric water, and were influenced by water-rock interactions such as salt dissolution, dolomitization of calcite, albitization of feldspar. In the Hetianhe Gas Field where salt dissolution took place, δD and δ~(18)O values can be used to trace nicely meteoric water recharge area and flow direction, but TDS can not. Part of the waters have high TDS but very light δD and δ~(18)O. When combined with paleo-topography, or fluid potentials, meteoric water is suggested to flow eastward in the Hetianhe Gas Field, which is the same with the Central Tarim. Whist in the Kuche forland basin, meteoric water may have permeated Cambrian-Ordovician strata. Relationship between ~(87)Sr/~(86)Sr and 1/Sr can be used to indicate migration and mixing of brines from carbonate strata (low ~(87)Sr/~(86)Sr ratio but high Sr content), clastic strata (high ~(87)Sr/~(86)Sr ratio but low Sr content) and crystalline basement (high ~(87)Sr/~(86)Sr ratio and heavy δ~(18)O value). Using this approach, it can be found that ~(87)Sr-depleted brine from Ordovician carbonates have migrated up to and mixed with ~(87)Sr-enriched waters from Silurian and Carboniferous sandstones, and that Silurian brines have mixed with meteoric water. In the Kuche forland basin, brines from the Cambrian and Ordovician carbonates have higher ~(87)Sr/~(86)Sr ratios than those from the overlying sandstones, when combined with chemistry, δ~(15)N and ~3He/~4He ratios of the coexisting natural gases, suggesting that the brines were derived from the basement. There exists some debate on the effect of hydrocarbon emplacement on mineral diagenesis. Case-study from Silurian sandstones in the Central Tarim show that quartz has kept overgrowing secondarily when oil saturation was decreased by meteoric water flushing subsequently to hydrocarbon emplacement. Silicon precipitates on the water-wet quartz surface, leading to decreased Si concentration close to the surface. A Si grads can result in Si diffusion, which supplies Si for quartz overgrowth. Hydrocarbon oxidation-sulfate reduction is an important type of organic-inorganic interaction. Not only can it make secondary alteration of hydrocarbons, but generate H_2S and CO_2 gases which can improve reservoir property. Thermochemical sulfate reduction took place at the temperatures more than 125 ℃ to 140 ℃ in the Cambrian-Ordovician carbonates, the products - H_2S and CO_2 gases migrated up to the Silurian, and precipitated as pyrite and calcite, respectively. The pyrite has an average δ~(34)S value close to those of Ordovician seawater and anhydrite, and calcite has δ~(13)C value as low as -21.5‰. In the Hetianhe Gas Field, sulfate reduction bacteria carried by meteoric water flowing eastward may have preferentially depleted ~(12)C of light hydrocarbon gases, and results in heavier δ~(13)C values of the residual hydrocarbon gases and higher molar CO_2 in the natural gases in the west than in the east. Coexisting pyrite has δ~(34)S values as low as -24.9‰.

云南省白牛厂超大型银多金属矿床矿物学及矿床地球化学

白牛厂矿床是超大型银多金属矿床，除银储量(>7000t)达到超大型规模外，铅、锌、锡储量均达大型规模，同时伴生大量的分散元素（In、Cd、Ge、Ga等）。矿床位于滇东南个旧和都龙矿田之间，赋存于华南加里东褶皱系滇东南褶皱带西北缘的中寒武统细碎屑岩系之中，北西面以弥勒断裂与扬子地块分界，南西以红河断裂为界与哀牢山断块毗邻，南连越北古陆，东部文麻断裂与南岭褶皱系连为一体，区内地质构造、岩浆活动和矿化作用均较复杂，各构造单元的构造演化对白牛厂银多金属矿床均有不同程度的影响。 白牛厂银多金属矿床自80年代后期被发现以来，已有多家单位和个人在该区开展了一系列的研究工作。但是，在成矿物质及流体来源、矿床成因、矿床与花岗岩的关系等方面都存在诸多争议。本文在深入细致的野外地质工作基础上，对矿石进行了系统的显微镜鉴定，并对部分矿物做了电子探针定量及面扫描分析，详细研究了矿床成矿元素特征及主量元素、微量元素、稀土元素、同位素地球化学特征，主要取得以下结论性成果： 1. 银矿物的赋存状态及形成阶段。银主要以硫盐或复硫盐矿物的形式出现，方铅矿是主要的载银矿物。原生银矿物明显分为两组：一组为Ag的黝铜族矿物和Ag的锑硫盐矿物，产于方铅矿的内部或与方铅矿连生形成文象状连晶，与方铅矿具有相似的物源，属热水沉积成因；另一组为Ag的锡硫盐矿物，产于方铅矿边部，往往伴随锡石、黄锡矿、辉锑锡铅矿产出，可见黄锡矿交代锡石形成镶边结构，暗示了其岩浆热液成因。 2. 花岗岩特征及其与成矿的关系。白牛厂矿区花岗岩具有富硅、富碱及高钾低钠特点，属铝过饱和钙碱性岩，与花南改造型花岗岩相似，属同碰撞S型花岗岩，成岩物源主要是基底变质岩重熔作用形成的花岗岩浆，Ag、Pb、Zn、Sn等成矿元素含量较高；与矿石稀土元素对比研究表明，花岗岩稀土配分模式与矿区东南部穿心洞、对门山和阿尾矿段矿石相似，而与矿区西北部白羊矿段矿石相差较大，暗示后期岩浆叠加改造作用主要发生在矿区东南部诸矿段。 　　3. 矿床含矿沉积建造地球化学特征。通过与中国大厂、个旧典型热水沉积硅质岩，加拿大沙利文矿山的条带状富电气石热液沉积岩和加拿大Agnico-Eugle矿山的铁建造中的条带状燧石岩以及现代海底热水沉积物对应的主量元素、微量元素及稀土元素对比研究，为白牛厂矿床含矿沉积建造提供了热水沉积成因的地球化学证据，指出该区中寒武世可能发生了广泛的热水沉积事件。 　　4. 成矿物质及成矿流体来源。系统的铅、硫同位素研究表明，中寒武世热水沉积成矿期金属成矿元素及硫主要是由下地壳古老变质岩淋滤出来的；燕山期花岗岩也在矿区东南部叠加改造较强的部位提供了Sn等部分金属成矿元素及硫。碳、氧同位素及矿石稀土元素反映矿床早期成矿流体源于深部岩浆，晚期主要来源于燕山期花岗岩浆。 　　5. 矿床分散元素特征。分散元素In、Cd、Ga含量较高，平均含量分别为33.21×10-6、389.8×10-6、10.18×10-6，初步估计该矿床In、Cd、Ga储量分别大于180t、20000t、600t，闪锌矿是分散元素In、Cd、Ga主要的载体矿物。 6. 可能的矿床成因模式。白牛厂银多金属矿床是长期以来多种地质作用综合的产物，具有多来源、多期次成矿特点，经历了广泛且具有重要成矿意义的中寒世热水沉积成矿作用和燕山晚期岩浆热液叠加改造作用，热水沉积成矿作用形成了层状、似层状矿体，燕山期岩浆热液在矿区东南部对矿床强烈叠加改造，白牛厂银多金属矿床应属“热水沉积＋岩浆热液叠加改造”成因。