Reflectance spectroscopy and geochemical analyses of Lake Hoare sediments, Antarctica: implications for remote sensing of the Earth and Mars

Visible to infrared reflectance spectroscopic analyses (0.3-25 micromoles) have been performed on sediments from the Dry Valleys region of Antarctica. Sample characterization for these sediments includes extensive geochemical analyses and X-ray diffraction (XRD). The reflectance spectra and XRD indicate major amounts of quartz, feldspar, and pyroxene in these samples and lesser amounts of carbonate, mica, chlorite, amphibole, illite, smectite, and organic matter. Calcite is the primary form of carbonate present in these Lake Hoare sediments based on the elemental abundances and spectroscopic features. The particle size distribution of the major and secondary components influences their detection in mixtures and this sensitivity to particle size is manifested differently in the "volume scattering" and "surface scattering" infrared regions. The Christiansen feature lies between these two spectral regimes and is influenced by the spectral properties of both regions. For these mixtures the Christiansen feature was found to be dependent on physical parameters, such as particle size and sample texture, as well as the mineralogy. Semiquantitative spectroscopic detection of calcite and organic material has been tested in these quartz- and feldspar-rich sediments. The relative spectral band depths due to organics and calcite correlate in general with the wt% C from organic matter and carbonate. The amounts of organic matter and carbonate present correlate with high Br and U abundances and high Ca and Sr abundances, respectively. Variation in the elemental abundances was overall minimal, which is consistent with a common sedimentary origin for the forty-two samples studied here from Lake Hoare.     

板块构造,板块运移机制及裂谷作用

一系列西半球大陆分布的古地理分析认为，通过缓慢对流的下层岩石圈的上地幔施加到岩石圈底部的磨擦力在驱驶板块运动机制上可起到重要作用。通过这样的简化，与软流圈上涌以及与在造山带处岩石圈过厚有关的岩片抽拉和岩层波状起伏，洋脊推动和张应力偏量可以被认为是次要的板块运移力。全球的现在应力状态以及整个地质证据说明了主压应力可以通过大陆和海洋岩石圈远距离传送。主要大陆块体的组合（象ｐａｎｇｅａ联合古陆）可能具有单一施加在上地幔对流系统的效应。上地慢对流系统导致了大陆块体的衰亡和重组，由岩石圈中偏张应力的发育以及由施加在巨大大陆底部之上拖曳力引起大陆分裂，形成新的软流圈上涌体系。岩石圈扩张在断裂处形成高峰，接着软流圈物质主动平流进入到两个分散板块之间，作为洋壳加积。与此同时，洋隆对板块分散起着推动力的作用。如果远区域挤压应力阻止了不同板块进一步离散的话，沿着洋底的扩张轴的活动性可能突然终止。这可以解释在板块边界重组期间通常在远距离区域海底扩张轴的几乎同时消亡特征。假设一个有限的球体，在海底扩张轴处新的洋壳岩石圈的产生一定与由洋壳岩石圈消减数量和／或大陆地壳和下部地壳物质消减以及亚地壳消减地方的数量相匹配。由地慢对流系统以及     

湘中桃江中奥陶统黑色岩系岩石学地球化学及成因

桃江中奥陶统黑色岩系主要由黑色页岩等七类岩石组成,主要矿物为伊利石、绿泥石、玉髓等。该岩系经历了强的晚期成岩作用。碳同位素(δ~(13)C=-9.35～-20.13‰)等特征表明硫酸盐还原作用形成了富~(12)C的成岩碳酸盐矿物。黑色岩系富Mn、Ba等元素,B-V图解表明它们为海相,V/Cr值表明其形成于还原环境。湘中中奥陶统黑色岩系的空间分布、几何形态等表明其形成与氧最小带有关。     

小应力变化对大地震发生的影响

许多观测表明,相对小的应力变化就能触发或制止地震。这个结果令人惊奇,因为触发地震的应力扰动只是引发地震应力降的一小部分,我们用符合物理实际的数值模型模拟地震断层来研究这个现象,断层是不均匀的,因此,断层表面各处会有不同的破裂判据。我们将不均匀断层模拟成由许多小区域组成,大部分小区域是均匀的,在小区域上可发生简单的库仑破裂。因此那些小区域会多次（重复）破裂,断层上的存储应力会很不均匀。我们看到围限应     

Consistent fractionation of 13C in nature and in the laboratory: growth-rate effects in some haptophyte algae

The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] < or = 0.1 microM) fall above the b = f[PO4] line. Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.     

Endocrine disruption in a marine amphipod? Field observations of intersexuality and de-masculinisation

Intersexuality has been found in both males and females of the marine/estuarine amphipod, Echinogammarus marinus, at polluted and reference sites in East Scotland. Polluted sites had significantly more intersex specimens than reference sites, however the cause of intersexuality is unclear. Discriminant analysis of morphometric data showed that normal male specimens from the most polluted site resembled pooled intersex males, suggesting that subtle endocrine disruption (ED) maybe occurring in these otherwise apparently normal males. The main discriminating character was gnathopod size, recognised to be under androgenic gland control. The association of distinctive morphometry with intersexuality may provide a new approach to biomarkers of ED in crustaceans. The opportunities for other novel biomarkers, for example biochemical or behavioural markers, may also be explored through study of intersex animals.     

香港滑坡中原生火山组构和粘土分布状态的意义

香港火山岩地区大多数雨水诱发的滑坡层次浅,规模小。但是１９９５年香港岛上发生的两起严重滑坡使原生火山岩叶的叶量和高岭土堆积之间的关系明确起来了,这种关系也许在测定较大的崩塌场地有普遍意义。（１）在缓倾斜凝灰岩中平行层理的剪切带是高岭土堆积的位置,成为软弱的面状低透水层,起到顺坡崩塌的破裂面效果;（２）陡倾斜组构（条纹斑状叶理）和近于平行的密集节理发育在同火山期剪切带中,深层次风化作用沿着剪切带加深