尼泊尔喜马拉雅山脉中央丘里亚冲断层的电子自旋共振测年

利用断层泥样品中石英颗粒的ESR信号,研究尼泊尔喜马拉雅山脉南段中央丘里亚冲断层(CCT)第四纪断层活动的时间模式。为了更好地理解重置过程,分析了不同石英粒度的ESR信号、累积剂量和年龄的变化。样品CCT3的E1’中心(ESR定年的一种信号)的ESR强度结果显示,大块、粗粒(200~250 μm)和细粒(40~80 μm)粒度组分存在显著的空间变化。第四纪断层的ESR数据,粗年龄为(5±0.5) ka,细分数平均年龄为(50±10) ka,显示了西瓦利克地区最近的伸展事件。

统计降尺度法对未来区域气候变化情景预估的研究进展

由于迄今为止大部分的海气耦合气候模式 (AOGCM)的空间分辨率还较低,很难对区域尺度的气候变化情景做合理的预测,降尺度法已广泛用于弥补AOGCM在这方面的不足。简要介绍了 3种常用的降尺度法:动力降尺度法、统计降尺度法和统计与动力相结合的降尺度法;系统论述了统计降尺度方法的理论和应用的研究进展,其中包括:统计降尺度法的基本假设,统计降尺度法的优缺点,以及常用的 3种统计降尺度法;还论述了用统计降尺度法预估未来气候情景的一般步骤,以及方差放大技术在统计降尺度中的应用;同时还强调了统计降尺度方法和动力降尺度方法比较研究在统计降尺度研究中的重要性;最后指出统计与动力相结合的降尺度方法将成为降尺度技术的重要发展方向。

统计降尺度法对华北地区未来区域气温变化情景的预估

迄今为止，大部分海气耦合气候模式（AOGCM）的空间分辨率还较低，很难对区域尺度的气候变化情景做合理的预测。降尺度法已广泛用于弥补AOGCM在这方面的不足。作者采用统计降尺度方法对1月和7月华北地区49个气象观测站的未来月平均温度变化情景进行预估。采用的统计降尺度方法是主分量分析与逐步回归分析相结合的多元线性回归模型。首先，采用1961-2000年的NCEP再分析资料和49个台站的观测资料建立月平均温度的统计降尺度模型，然后把建立的统计降尺度模型应用于HadCM3SRESA2和B2两种排放情景，从而生成各个台站1950-2099年1月份和7月份温度变化情景。结果表明：在当前气候条件下，无论1月还是7月，统计降尺度方法模拟的温度与观测的温度有很好的一致性，而且在大多数台站，统计降尺度模拟气温与观测值相比略微偏低。对于未来气候情景的预估方面，无论1月还是7月，也无论是HadCM3SRESA2还是B2排放情景驱动统计模型，结果表明大多数的站点都存在温度的明显上升趋势，同时7月的上升趋势与1月相比偏低。

欧亚大陆春季植被状况与东亚夏季大气环流的显著联系

地表植被覆盖的变化能通过改变陆面参数,以及生地化循环过程,对区域和全球气候产生重要影响。文中利用1982—2002年欧亚大陆春季归一化植被指数(NDVI)和欧洲中期数值天气预报中心再分析资料,采用奇异值分解分析方法,研究欧亚大陆春季植被状况与东亚夏季大气环流的关系。结果表明,贝加尔湖以西区域(55°—65°N,60°—100°E)春季植被状况与东亚夏季大气环流存在显著联系。当春季该区植被指数偏高时,在对流层高层从巴尔喀什湖、贝加尔湖至日本北部,以及中国华南和中南半岛上空存在显著的纬向风正异常,中国华北地区和江淮地区以北为显著负异常,异常中心自北向南依次为"正-负-正"分布,说明东亚夏季200hPa西风急流轴偏南;相应的在对流层中层15°—25°N地区西风偏强,伴随偏强上升气流,而在25°—42°N地区西风偏弱,并且在32°N附近存在显著下沉气流;在对流层低层,中国江淮流域以北、华北及贝加尔湖以东地区存在明显的反气旋型风场异常,而华南存在东北风异常。这种环流特征说明东亚夏季风偏弱,雨带偏南,并且使得中国华南降水偏多,华南以北大部分地区降水偏少,同时中国东南以及青藏高原东南部温度偏低,而中国北方以及江淮流域温度偏高。欧亚大陆春季植被状况与东亚夏季风的显著关系为东亚夏季风预测提供了有用的帮助。

气候和人为因素对黄土高原地区小麦生产的影响

为量化气候和人为因素对黄土高原地区小麦产量的影响，找到减少干旱对小麦生产影响的途径，利用气象数据和多种来源的作物数据模拟了1955～2004年冬小麦产量。结果表明，黄土高原地区的降水量、和蒸散量在1960～2000年间，以每10年高达20mm的速度减少，并且自20世纪90年代以来气温上升加剧了土壤水分的亏缺，但黄土高原稳定的春雨降低了气温上升带来的影响。在过去的50年里，人为因素（非气候，技术进步）对小麦总产量的走向起了决定性作用，然而最近10年来，模拟结果显示，气候影响已经上升到了60％，达到每10年每公顷300kg（总量约500kg）。现代农业中重型农机具的使用对黄土土壤质量和小麦产量都有不良影响。相反，免耕措施与小麦秸秆覆盖改进土壤水分平衡及其再分配，不仅增加了作物产量，而且降低了减产的风险。

Spatial and temporal variations and controlling factors of potential evapotranspiration in China:1956-2000

Based on the climatic data of 580 stations in China during 1956 and 2000, potential evapotranspiration are calculated using the Penman-Monteith Method recommended by FAO. The spatial and temporal distributions of the potential evapotranspiration over China and the temporal trends of the regional means for 10 major river basins and whole China are analyzed. Through a partial correlation analysis, the major climate factors which affect the temporal change of the potential evapotranspiration are analyzed. Major results are drawn as follows： 1） The seasonal and annual potential evapotranspiration for China as a whole and for most basins show decline tendencies during the past 45 years; for the Songhua River Basin there appears a slightly increasing trend. 2） Consequently, the annual potential evapotranspirations averaged over 1980-2000 are lower than those for the first water resources assessment （1956-1979） in most parts of China. Exceptions are found in some areas of Shandong Peninsula, western and middle basins of the rivers in Southwest China, Ningxia Hui Autonomous Region as well as the source regions of the Yangtze and Yellow rivers, which may have brought about disadvantages to the exploration and utilization of water resources. 3） Generally, sunshine duration, wind speed and relative humidity have greater impact on the potential evapotranspiration than temperature. Decline tendencies of sunshine duration and/or wind speed in the same period appear to be the major causes for the negative trend of the potential evapotranspiration in most areas.

Trends in Graded Precipitation in China from 1961 to 2000

Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. The last four grades together constitute the so called effective precipitation （〉 1 mm d^-1）. The spatial distribution and temporal trend of the graded precipitation days are examined. A decreasing trend in trace precipitation days is observed for the whole of China, except at several sites in the south of the middle section of the Yangtze River, while a decreasing trend in slight precipitation days only appears in eastern China. The decreasing trend and interannual variability of trace precipitation days is consistent with the warming trend and corresponding temperature variability in China for the same period, indicating a possible role played by increased surface air temperature in cloud formation processes. For the effective precipitation days, a decreasing trend is observed along the Yellow River valley and for the middle reaches of the Yangtze River and Southwest China, while an increasing trend is found for Xinjiang, the eastern Tibetan Plateau, Northeast China and Southeast China. The decreasing trend of effective precipitation days for the middle- lower Yellow River valley and the increasing trend for the lower Yangtze River valley are most likely linked to anomalous monsoon circulation in East China. The most important contributor to the trend in effective precipitation depends upon the region concerned.

Using Statistical Downscaling to Quantify the GCM-Related Uncertainty in Regional Climate Change Scenarios: A Case Study of Swedish Precipitation

There are a number of sources of uncertainty in regional climate change scenarios. When statistical downscaling is used to obtain regional climate change scenarios, the uncertainty may originate from the uncertainties in the global climate models used, the skill of the statistical model, and the forcing scenarios applied to the global climate model. The uncertainty associated with global climate models can be evaluated by examining the differences in the predictors and in the downscaled climate change scenarios based on a set of different global climate models. When standardized global climate model simulations such as the second phase of the Coupled Model Intercomparison Project （CMIP2） are used, the difference in the downscaled variables mainly reflects differences in the climate models and the natural variability in the simulated climates. It is proposed that the spread of the estimates can be taken as a measure of the uncertainty associated with global climate models. The proposed method is applied to the estimation of global-climate-model-related uncertainty in regional precipitation change scenarios in Sweden. Results from statistical downscaling based on 17 global climate models show that there is an overall increase in annual precipitation all over Sweden although a considerable spread of the changes in the precipitation exists. The general increase can be attributed to the increased large-scale precipitation and the enhanced westerly wind. The estimated uncertainty is nearly independent of region. However, there is a seasonal dependence. The estimates for winter show the highest level of confidence, while the estimates for summer show the least.

Heterogeneity of Physico-Chemical Properties in Structured Soils and Its Consequences

Structured soils are characterized by the presence of inter- and intra-aggregate pore systems and aggregates, which show varying chemical, physical, and biological properties depending on the aggregate type and land use system. How far these aspects also affect the ion exchange processes and to what extent the interaction between the carbon distribution and kind of organic substances affect the internal soil strength as well as hydraulic properties like wettability are still under discussion. Thus, the objective of this research was to clarify the effect of soil aggregation on physical and chemical properties of structured soils at two scales: homogenized material and single aggregates. Data obtained by sequentially peeling off soil aggregates layers revealed gradients in the chemical composition from the aggregate surface to the aggregate core. In aggregates from long term untreated forest soils we found lower amounts of carbon in the external layer, while in arable soils the differentiation was not pronounced. However, soil aggregates originating from these sites exhibited a higher concentration of microbial activity in the outer aggregate layer and declined towards the interior. Furthermore, soil depth and the vegetation type affected the wettability. Aggregate strength depended on water suction and differences in tillage treatments.

Climate-Induced Variability of Sea Level in Stockholm: Influence of Air Temperature and Atmospheric Circulation

This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift, is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months （June and August） that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables （zonal winds, vorticity and mean air temperature during the previous two months） and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.

Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical,magnetic and tectonic data reveal early plate tectonic genes flanking subduction margins

The Makhonjwa Mountains, traditionally referred to as the Barberton Greenstone Belt, retain an iconic Paleoarchean archive against which numerical models of early earth geodynamics can be tested. We present new geologic and structural maps, geochemical plots, geo- and thermo-chronology, and geophysical data from seven silicic, mafic to ultramafic complexes separated by major shear systems across the southern Makhonjwa Mountains. All reveal signs of modern oceanic back-arc crust and subductionrelated processes. We compare the rates of processes determined from this data and balance these against plate tectonic and plume related models. Robust rates of both horizontal and vertical tectonic processes derived from the Makhonjwa Mountain complexes are similar, well within an order of magnitude, to those encountered across modern oceanic and orogenic terrains flanking Western Pacific-like subduction zones. We conclude that plate tectonics and linked plate-boundary processes were well established by 3.2-3.6 Ga. Our work provides new constraints for modellers with rates of a 'basket' of processes against which to test Paleoarchean geodynamic models over a time period close to the length of the Phanerozoic.

IDENTIFICATION OF WOOD AND BARK EXTRACTIVES AND THEIR TOXICOLOGICAL EFFECTS ON THE TMP EFFLUENTS

Wood extractives in model TMP effluents and bio-treated TMP mill effluent were extracted, isolated with liquid-liquid extraction, and analyzed with GC/MS following sylilation. Acute and chronic toxicity of the effluent samples were tested with Ceriodaphnia dubia. Wood and bark extractives are responsible for the toxicity of the TMP effluent to aquatic life. Resin and fatty acids have a dominating contribution to acute toxicity. Removal of them from the effluent cannot deplete all toxicants, some neutral extractives such as phytosterols, are still chronically toxic to Ceriodaphnia dubia. Wood bark has a dramatic impact on acute toxicity of the TMP effluent. Only 5% of spruce bark addition can increase acute toxicity by 38.4%. However, it has a reverse trend for chronic toxicity, which indicates that some neutral wood extractives may play important role in chronic toxicity of the TMP effluent as well. Successful control of the debarking process and debark effluents is essential for achieving high-quality effluent treatment.

Four billion years of ophiolites reveal secular trends in oceanic crust formation

We combine a geological, geochemical and tectonic dataset from 118 ophiolite complexes of the major global Phanerozoic orogenic belts with similar datasets of ophiolites from 111 Precambrian greenstone belts to construct an overview of oceanic crust generation over 4 billion years. Geochemical discrimi- nation systematics built on immobile trace elements reveal that the basaltic units of the Phanerozoic ophiolites are dominantly subduction-related （75%）, linked to backarc processes and characterized by a strong MORB component, similar to ophiolites in Precambrian greenstone sequences （85%）. The remaining 25% Phanerozoic subduction-unrelated ophiolites are mainly （74%） of Mid-Ocean-Ridge type （MORB type）, in contrast to the equal proportion of RiftlContinental Margin, Plume, and MORB type ophiolites in the Precambrian greenstone belts. Throughout the Phanerozoic there are large geochemical variations in major and trace elements, but for average element values calculated in 5 bins of 100 million year intervals there are no obvious secular trends. By contrast, basaltic units in the ophiolites of the Precambrian greenstones （calculated in 12 bins of 250 million years intervals）, starting in late Paleo- to early Mesoproterozoic （ca. 2.0-1.8 Ga）, exhibit an apparent decrease in the average values of incom- patible elements such as Ti, P, Zr, Y and Nb, and an increase in the compatible elements Ni and Cr with deeper time to the end of the Archean and into the Hadean. These changes can be attributed to decreasing degrees of partial melting of the upper mantle from HadeanJArchean to Present. The onset of geochemical changes coincide with the timing of detectible changes in the structural architecture of the ophiolites such as greater volumes of gabbro and more common sheeted dyke complexes, and lesser occurrences of ocelli （varioles） in the pillow lavas in ophiolites younger than 2 Ga. The global data from the Precambrian ophiolites, representative of nearly 50% of all known worldwide greenstone belts provide significant clues for the operation of plate tectonic processes in the Archean.

Geochemical Characterization of Intermediate to Silicic Rocks in the Global Ophiolite Record

Ophiolites consist predominantly of mafic-ultramafic rocks but also contain in subordinate amounts intermediate to silicic intrusive–extrusive rocks in them.These rocks,although not in large volumes in comparison to mafic–ultramafic units,reveal significant clues about melt evolution,magmatic accretion processes,and partial melting of pre-existing oceanic crust during ophiolite evolution.They also yield ample accessory minerals,such as zircon and monazite,which are widely used to date the timing of oceanic crust generation.We present a global synthesis of the occurrence of such leucocratic,intrusive and volcanic rocks from 150 Phanerozoic to Archean ophiolites,and evaluate models for their genesis during the development of oceanic crust in different tectonic environments.In the ophiolite complexes we have investigated,intrusive and extrusive rocks show a wide range in composition.Intermediate rocks（with Si O2 between 52and 63 wt.%）include andesite and diorite,whereas the silicic rocks（with Si O2 more than 63 wt.%）include dacite,trondhjemite,tonalite and granite.For subduction-relatedandsubduction-unrelated MORB-type ophiolites in the Phanerozoic orogenic belts,the most commonly reported intermediate to silicic intrusive rocks,independent of their original tectonic setting,are trondhjemite,plagiogranite and tonalite,and less commonly quartz-diorite and diorite.These rock types have been documented from 80 percent of the 104ophiolites included in this study.Intermediate to silicic lavas and/or pyroclastic rocks（basaltic andesite,andesite,dacite and rhyolite）are less abundant,and have been reported from only 35 percent of the 104 ophiolites.Trachyte occurs in some of the Rift/Continental Margintype,subduction-unrelated ophiolitesEvolvedrocksinsubduction-unrelated,Rift/Continental Margin ophiolites are predominantly basaltic andesite and andesite,whereas MOR type（mid-ocean ridge）ophiolites exhibit nearly equal proportions of basaltic andesite/andesite and rhyodacite and Plume/MOR type ophiolites are characterized by rhyolites.Intermediate to silicic volcanic uints in the Backarc sub-group of subduction-related ophiolites are characterized by similar amounts of basaltic andesite/andesite and rhyodacite,whereas in the Backarc to Forearc,Forearc,and Volcanic Arc sub-groups they are mainly basaltic andesite/andesite.Intermediate to silicic rocks in Rift/Continental Margin and Plume/MOR type ophiolites are generally LREE-enriched,whereas those in the MOR type vary from LREE-depleted to LREE-enriched.The Backarc and Backarc to Forearc types are similar to the MOR type;silicic rocks of the Forearc and Volcanic Arc types are generally LREE-enriched.The main process in the formation of the majority of the intermediate to silicic rocks in both subduction-unrelated and subduction-related ophiolites is partial melting of basaltic and/or gabbroic rocks beneath the spreading centers,whereas a minor volume in subduction-related ophiolites are adakites that were produced from partial melting of a subducting slab.Silcic to intermediate rocks in Plume/MOR type ophiolites are generated by fractional crystallization of basaltic melt.The incompatible,non-conservative elements,such as Ba and Th,are weakly to strongly enriched in subduction-related ophiolites as a result of shallow to deep enrichment associated with subduction zone processes.The field occurrence and the geochemical character of leucocratic rocks in ophiolites show considerable variations,providing additional constraints on the petrogenesis of ophiolites in different tectonic settings.Fractional crystallization appears to have been an important process in the formation of the intermediate to silicic rocks in Rift/CM and P/MOR ophiolites in the subduction-unrelated class,as well as VA ophiolites in the subduction-related class.In these types of ophiolites magma chambers might have operated as closed-systems for a sufficient amount of time for fractionation and compositional zoning of the magma to take place（Fig.1C1）.Fractional crystallization was of subordinate importance during the igneous construction of the MOR,BA,FA,and BA-FA ophiolites.Instead,partial melting of hydrothermally altered crust was the most common process resulting in the majority of the intermediate to felsic rocks of the Rift/CM（estimated to 60%）,MOR（estimated to 95%）,and the BA,FA and BA-FA（estimated to 75%）ophiolites,as well as a high proportion of the VA ophiolites（;0%）(Fig.1C2).Slab-generated melts that result in the production of intermediate to silicic rocks of adakitic character represent a relatively small fraction（;5%in Phanerozoic ophiolites）of subduction-related ophiolites（Fig.1C3）.Some adakites are very low in incompatible elements（e.g.,La）,suggesting that these melts were generated from highly depleted MORB.Precambrian ophiolites contain a higher percentage of adakites（ca.35%）,indicating that physical conditions were more favorable for slab melting during the Precambrian than in the Phanerozoic.This phenomenon may have resulted from higher geothermal gradient along relatively shallow-dippingsubductionzonesduringthe Precambrian.

The First Natural Ventilation Assessment in Building Design in Djibouti

With a sustained period of economic growth, rapidly growing populations and with more diversified economies Africa need sustainable development; hence the greater need for massive investments in energy. Sub-Saharan countries such as Djibouti have the potential and ability to harness their natural ventilation as a passive cooling system for designing new houses. The rapid expansion of the Djibouti city is affecting negatively the environment and the safety and comfort of its inhabitants. Proper atmospheric urban planning and management are key to making cities environmentally friendly and sustainable. Based on energy consumption, climate conditions in Djibouti and numerical analysis using Computational Fluid Dynamics （CFD）, it is apparent that the natural ventilation creates a thermally comfortable indoor environment in buildings during the cool season of the year. Measured wind data from two measurement systems are presented and discussed. Statistical analyses, wind rose, Weibull distribution were carried out to understand the natural ventilation characteristic, which is used for evolving the basic criteria for economic viability of building in the semi-arid climate of Djibouti. The study found that it is possible to benefit from natural ventilation in buildings during the cool season of the year.

The Storm Tracks Response to Changes in Atmospheric Greenhouse Gas Concentration at the South of Brazil and Southwest Atlantic Ocean

Here we investigate the ocean-atmosphere coupling and the contribution of the Sea Surface Temperature (SST) variations in: 1) Brazil-Malvinas Confluence (BMC) region, 2) Southwest Atlantic Ocean and 3) Southern Brazil. Numerical simulations of the ECHAM5/MPI-OM coupled ocean-atmosphere model were used to analyze the changes in the seasonal trajectory of the extratropical cyclones, in terms of intensification of physical mechanisms and implications for future scenarios. The numerical experiment for the future scenario considered an atmospheric CO2 concentration of approximately 770 ppm, which represents an increment of more than 350 ppm over the current values recorded by the Mauna Loa reference station. For this scenario, the results indicated a Storm Tracks (ST) displacement of 5° latitude toward south and changes of the meridional transport of sensible heat, close to 50°S. The increase in SST induces ST intensification and consequently an increase in the occurrence of extratropical cyclones. Overall, in the BMC region, we found a change in the pattern of cyclogenetic activity occurrence, with less frequent, but more intense events. On the Southern Brazilian region, the results of this study indicate increases in rainfall during summer months, whereas, a decrease in frequency and an increase in intensity were found for wintertime. We suggest that these changes could impact the climate dynamic of the Brazilian South coast, with a magnitude yet unknown.

Arctic Sea Ice: Decadal Simulations and Future Scenarios Using BESM-OA

Important international reports and a significant number of scientific publications have reported on the abrupt decline of Arctic sea ice and its impact on the Global Climate System. In this paper, we evaluated the ability of the newly implemented Brazilian Earth System Model (BESM-OA) to represent Arctic sea ice and sensitivity to CO2 forcing, using decadal simulations (1980-2012) and future scenarios (2006-2100). We validated our results with satellite observations and compared them to Coupled Model Intercomparison Project, Phase 5 (CMIP5) for the same numerical experiment. BESM results for the seasonal cycle are consistent with CMIP5 models and observations. However, almost all models tend to overestimate sea ice extent in March compared to observations. The correct evaluation of minimum record of sea ice, in terms of time, spatial and area remains a limitation in Coupled Global Climate Models. Looking to spatial patterns, we found a systematic model error in September sea ice cover between the Beaufort Sea and East Siberia for most models. Future scenarios show a decrease in sea ice extent in response to an increase in radiative forcing for all models. From the year 2045 onwards, all models show a dramatic shrinking in sea ice and ice free conditions at the end of the melting season. The projected future sea ice loss is explained by the combined effects of the amplified warming in northern hemisphere high latitudes and feedbacks processes.

Testing the Proposed Municipality Resilience Index to Climate Change Shocks and Stresses in Mbale Municipality in Eastern Uganda

Since climate change shocks and stresses cannot be fully prevented, building resilient urban areas is gaining more attention in the global community. By building resilience, the negative impacts of climate change shocks and stresses can be alleviated. Several indices have been developed to measure urban resilience. Yet, most of these indices focus more on objective methods which require robust bio-physical and socio-economic data sets which are generally lacking in many developing countries. To reduce this challenge, the use of subjective methods has recently been suggested. This study proposed and tested a Municipality Resilience Index (MRI) which employed a subjective method to assess the resilience of Mbale municipality in Eastern Uganda against climate change shocks and stresses. The proposed MRI includes 46 variables describing the physical, social, economic and institutional dimensions. The MRI can be applied in any municipality in developing countries facing climate related shocks and stresses and with limited survey data. The application of this index to Mbale municipality shows that the municipality has a low resilience index of 0.2. Similarly, most variables in the four dimensions of resilience reflected very low resilience scores with other divisions being more resilient than the others. Furthermore, the social dimension has the lowest score as compared to the physical, economic and institutional dimensions. The findings indicate a spatial variability in the contribution of the resilience dimensions within this small geographic confine. Moreover, the findings show the strengths and weaknesses in the different dimensions of the proposed MRI. This can act as a guide for policy and practitioners on which sectors to target in order to enhance the resilience of Mbale municipality.

青藏高原东部全新世冬夏季风变化的高分辨率泥炭记录

在建立了全新世泥炭沉积物高分辨率冬夏季风代用指标时间序列的基础上,发现青藏高原若尔盖地区全新世冬夏季风的变化具有此消彼长和同时消长两种基本的模式,冬季风与夏季风在不同时间尺度上两种模式又相互嵌套.由冬夏季风指标叠加效应合成的气候状况却有与全球同步的规律性,表现出千年-百年尺度的不稳定性,6.2KA的季风突然减弱事件要比8.0KA的事件更显著,反映了亚洲季风的区域特点或它本身就是全球气候的一个窗口.

峨眉火成岩省内带岩浆硫化物含矿岩体橄榄石的成因意义

峨眉火成岩省内带出露数十个含Ni-Cu-铂族元素(PGE)硫化物矿床(或矿化)的镁铁质-超镁铁质侵入岩体.根据铂族元素(PGE)含量的不同,这些岩浆硫化物矿床可分为Ni-Cu型(如力马河和清水河)、Ni-Cu-PGE型(如清矿山和黄草坪)和PGE型(如金宝山和杨合武).不同类型含矿岩体的橄榄石电子探针分析表明,除了清矿山岩体少数几个橄榄石晶体属于镁橄榄石外(Fo90.1～Fo93.1),其余均为贵橄榄石(Fo76.8～Fo89.6).不同矿化类型的岩体的橄榄石成分差异明显.Ni-Cu型硫化物含矿岩体的橄榄石Fo为77～87,Ni含量变化范围为(976～2176)×10-6.Ni-Cu-PGE型硫化物含矿岩体的橄榄石Fo为80～86,Ni含量范围为(1024～2543)×10-6.PGE型硫化物含矿岩体的橄榄石Fo为78～84,Ni含量在(776～1755)×10-6之间变化.清矿山Ni-Cu-PGE型硫化物含矿岩体橄榄石具有高Fo(最高达93.1)和CaO含量(0.245%～1.14%)、以及非常低的Ni(266×10-6)的特征,可能是同化混染作用的结果.利用力马河岩体最高Fo含量的橄榄石成分计算表明,母岩浆是高镁苦橄玄武质岩浆.橄榄石分离结晶和硫化物熔离模拟显示:Ni-Cu型矿化侵入体母岩浆经历了最广泛的硫化物熔离(～0.1%),Ni-Cu-PGE型侵入体次之,大约为0.06%,而PGE型侵入体母岩浆硫化物熔离程度最低(～0.02%).早期结晶的橄榄石晶体与间隙硅酸盐熔浆之间再平衡过程是橄榄石成分变化的原因.