辽东北—吉南中生代火山岩地层与辽西义县组的对比

辽宁东北部桓仁—吉林南部通化地区分布有大面积的中生代火山岩,分别属于果松组、林子头组及小岭组。通过野外地质调查发现,这三个组的火山岩组合自下而上均显示为酸性—中性—酸性的岩石组合,在岩石组合上具有可对比性。对这三个组的典型火山岩进行LA-ICP-MS锆石U-Pb测年,结果显示果松组安山岩(GS-1-TWS)和流纹岩(GS-2-TWS)年龄为130.83±0.8Ma和118.5±1.1Ma;林子头组安山质凝灰岩(LZT1)和安山岩(LZT2)年龄为123.24±0.91Ma和126.0±2.9Ma;小岭组流纹岩(P03-29)和安山岩(P03-30)年龄为126.3±1.3Ma和129.0±1.4Ma,表明三个含有中生代火山岩的地层形成时代一致,均为早白垩世产物。辽西地区含有中生代火山岩的地层为义县组,其形成时代为133~118Ma之间,本文辽宁桓仁—吉林通化地区中生代火山岩形成时代为130~118Ma,二者为同时产物;并且二者均产有相同的热河生物群化石,所以辽东北—吉南果松组、林子头组、小岭组与辽西义县组可对比。!     

Sulfur isotopic geochemistry of the huize Pb-Zn ore field in yunnan province北大核心CSCD

In order to constrain sulfur isotope compositions of ore-forming fluids, ore-forming temperature, source of sulfur and mechanism of sulfur reduction in the Huize lead-zinc ore field, based on sulfur isotope compositions from previous studies, new data of sulfur isotopic composition of primary sulfide of upper ore-bodies in Qilinchang and newly-found sulfate outside the deposits were utilized in this study. It show that 5 values of primary sulfide vary from 8. Oft∗ to 17. 68 ft∗ , and sulfur isotopes in ore-forming fluid have reached equilibrium; S'lS values of sulfur out side the deposits vary from 17. 95ft∗ to 24. 30ft∗ with average value of 20. 14ft∗ , yielding sulfur isotopic composition of ore-for ming fluids as 14. 14ft∗ by the Pinekney method for mineral association. The value is close to 5'4S of marine sulfate. Ore-forming temperature is calculated as 1 34 - 388by isotope geological thermometer. The results of fluid inclusion thermometer indicate that barites were crystallized from hydrothermal fluid, which is suggested that sulfur in ore-forming fluid probably originates from marine sulfate of stratum in and outside the deposits or hydrothermal barites found in ore district. Reduction mechanism of sulfate is likely to be themio-chemical sulfate reduction.     

Late Holocene coastal sand movements in the Outer Hebrides, N.W. Scotland

Lithostratigraphical and biostratigraphical investigation of coastal marshes along the Atlantic coast of the Outer Hebrides from Lewis in the north to Barra in the south discloses inland-tapering sand units within marshland areas. The inland extent of each sand unit has been radiometrically dated and the units have been collectively interpreted as a proxy for past coastal storminess. The data appear to indicate that for the study sites investigated, the majority of the sand units were produced during episodes of climate deterioration both prior to and after the well-known period of Medieval warmth (MWP). Many were produced after ca. AD 1400. It is argued that the episodes of sand blow indicated by the deposits may reflect periods of increased cyclogenesis in the Atlantic associated with increased sea ice cover and an increase in the thermal gradient across the North Atlantic region.     

Hydrographic changes in the Labrador Sea, 1960–2005

The Labrador Sea has exhibited significant temperature and salinity variations over the past five decades. The whole basin was extremely warm and salty between the mid-1960s and early 1970s, and fresh and cold between the late 1980s and mid-1990s. The full column salinity change observed between these periods is equivalent to mixing a 6 m thick freshwater layer into the water column of the early 1970s. The freshening and cooling trends reversed in 1994 starting a new phase of heat and salt accumulation in the Labrador Sea sustained throughout the subsequent years. It took only a decade for the whole water column to lose most of its excessive freshwater, reinstate stratification and accumulate enough salt and heat to approach its record high salt and heat contents observed between the late 1960s and the early 1970s. If the recent tendencies persist, the basin’s storages of salt and heat will fairly soon, likely by 2008, exceed their historic highs.The main process responsible for the net cooling and freshening of the Labrador Sea between 1987 and 1994 was deep winter convection, which during this period progressively developed to its record depths. It was caused by the recurrence of severe winters during these years and in its turn produced the deepest, densest and most voluminous Labrador Sea Water (LSW_1987–1994) ever observed. The estimated annual production of this water during the period of 1987–1994 is equivalent to the average volume flux of about 4.5 Sv with some individual annual rates exceeding 7.0 Sv. Once winter convection had lost its strength in the winter of 1994–1995, the deep LSW_1987–1994 layer lost “communication” with the mixed layer above, consequently losing its volume, while gaining heat and salt from the intermediate waters outside the Labrador Sea.While the 1000–2000 m layer was steadily becoming warmer and saltier between 1994 and 2005, the upper 1000 m layer experienced another episode of cooling caused by an abrupt increase in the air-sea heat fluxes in the winter of 1999–2000. This change in the atmospheric forcing resulted in fairly intense convective mixing sufficient to produce a new prominent LSW class (LSW₂₀₀₀) penetrating deeper than 1300 m. This layer was steadily sinking or deepening over the years following its production and is presently overlain by even warmer and apparently less dense water mass, implying that LSW₂₀₀₀ is likely to follow the fate of its deeper precursor, LSW_1987–1994. The increasing stratification of the intermediate layer implies intensification in the baroclinic component of the boundary currents around the mid-depth perimeter of the Labrador Sea.The near-bottom waters, originating from the Denmark Strait overflow, exhibit strong interannual variability featuring distinct short-term basin-scale events or pulses of anomalously cold and fresh water, separated by warm and salty overflow modifications. Regardless of their sign these anomalies pass through the abyss of the Labrador Sea, first appearing at the Greenland side and then, about a year later, at the Labrador side and in the central Labrador Basin.The Northeast Atlantic Deep Water (2500–3200 m), originating from the Iceland–Scotland Overflow Water, reached its historically freshest state in the 2000–2001 period and has been steadily becoming saltier since then. It is argued that LSW_1987–1994 significantly contributed to the freshening, density decrease and volume loss experienced by this water mass between the late 1960s and the mid 1990s via the increased entrainment of freshening LSW, the hydrostatic adjustment to expanding LSW, or both.     

2001年冬春转换期间南海东北部水文和环流特征

根据2001年3月份南海东北部航次调查温、盐资料,分析了2001年冬末春初南海东北部温、盐结构和环流的特征.分析结果表明:观测期间南海东北部环流主要受一次海盆尺度气旋型冷环流支配,冷环流呈现双核结构,垂向尺度接近1000 m.吕宋海峡内侧断面的水交换在600 m以浅海水流入南海,在断面南部(20°N以南)中层和深层有流出,断面法向地转流向西净输运量为6.9×106m3/s;直接的黑潮入侵不超过120.5°E,但有部分的黑潮水沿陆坡达到台湾岛西南部海域,并更有一部分逸入东沙岛以西海域,与南海水混合变性.     

闽东北外海渔场捕捞中上层鱼类的渔具,渔法研究

本文分析了闽东北外海渔场资源特点，并就不同类型的拖网、围网渔具的适渔性对比试验进行了研究，认为以主机功率330.75kw及以上的拖网渔船，使用四片式疏目拖网和以主机功率183．75kw及以上的围网渔船，使用250m×150m的无囊灯光围网，于春、夏汛时在该渔场100m等深线附近海域能较有效地捕捞鲐鲹等中上层鱼类。