西藏谢通门地区中侏罗世花岗岩的地球化学特征及时代依据

西藏谢通门县一带区域上属于冈底斯花岗岩带南亚带,侵入岩极其发育,目前填绘有白垩纪、古近纪和新近纪岩体。通过同位素年代学研究,获得12个锆石的U-Pb同位素年龄数据,在原划归白垩纪、古近纪和新近纪岩体中解体出侏罗纪侵入体,按其岩石类型特征,归并为早侏罗世东热村序列和中侏罗世东嘎乡序列。其中,在约拉嘎莫岩体中获得锆石U-Pb同位素年龄166.9±2.8Ma,时代为中侏罗世巴柔期。     

Impacts of mineralogical compositions on different trapping mechanisms during long-term CO<Subscript>2</Subscript> storage in deep saline aquifers

Deep saline aquifers in sedimentary basins are considered to have the greatest potential for CO₂ geological storage in order to reduce carbon emissions. CO₂ injected into a saline sandstone aquifer tends to migrate upwards toward the caprock because the density of the supercritical CO₂ phase is lower than that of formation water. The accumulated CO₂ in the upper portions of the reservoir gradually dissolves into brine, lowers pH and changes the aqueous complexation, whereby induces mineral alteration. In turn, the mineralogical composition could impose significant effects on the evolution of solution, further on the mineralized CO₂. The high density of aqueous phase will then move downward due to gravity, give rise to “convective mixing,” which facilitate the transformation of CO₂ from the supercritical phase to the aqueous phase and then to the solid phase. In order to determine the impacts of mineralogical compositions on trapping amounts in different mechanisms for CO₂ geological storage, a 2D radial model was developed. The mineralogical composition for the base case was taken from a deep saline formation of the Ordos Basin, China. Three additional models with varying mineralogical compositions were carried out. Results indicate that the mineralogical composition had very obvious effects on different CO₂ trapping mechanisms. Specific to our cases, the dissolution of chlorite provided Mg²⁺ and Fe²⁺ for the formation of secondary carbonate minerals (ankerite, siderite and magnesite). When chlorite was absent in the saline aquifer, the dominant secondary carbon sequestration mineral was dawsonite, and the amount of CO₂ mineral trapping increased with an increase in the concentration of chlorite. After 3000 years, 69.08, 76.93, 83.52 and 87.24 % of the injected CO₂ can be trapped in the solid (mineral) phase, 16.05, 11.86, 8.82 and 6.99 % in the aqueous phase, and 14.87, 11.21, 7.66 and 5.77 % in the gas phase for Case 1 through 4, respectively.     

海洋浮游微食物网结构及其影响因素

微食物环是海洋生态系统中重要的物质和能量过程,是传统食物链的有效补充。微食物环研究是当前海洋生态学研究的热点之一,但对其结构的系统研究较少,海洋微食物网结构在2000年才被Garrison提出。尽管微食物网各个类群的丰度在不同海洋环境中有相对变化,但是这些变化都处于一定的范围之内,其丰度结构约为纤毛虫10 cell ml-1、鞭毛虫103 cell ml-1、微微型真核浮游生物104 cell ml-1、蓝细菌104-5 cell ml-1、异养细菌106 cell ml-1、病毒107 particle ml-1。海洋浮游食物链中捕食者和饵料生物粒径的最佳比值为10:1,实际研究中该比值会略低,例如纤毛虫与其饵料的粒径比值为8:1,鞭毛虫为3:1。Pico和Nano浮游植物的丰度比（Pico:Nano）是研究微食物网结构的指数之一,该指数具有不受研究尺度影响的优点,可用于研究区域性和全球性微食物网结构。近年来,学者们从多角度对海洋微食物网的结构开展了研究,不同海区微食物网各类群丰度、生物量的时间和空间变化研究有很多报道,微食物网的结构可受空间、季节、摄食、营养盐等多种因素影响。在对不同空间微食物网的研究中,学者往往研究不同物理性质的水团中各类群生物丰度的不同,以此来表征微食物网结构的不同;同一海区微食物网结构的季节变化也是使用各个类群丰度和生物量的变化来表示,该变化主要受水文环境因素影响。摄食者对微食物网各类生物的影响通过三种途径：1. 中型浮游动物摄食;2. 中型浮游动物摄食微型浮游动物,通过营养级级联效应影响低营养级生物;3. 中型浮游动物通过释放溶解有机物、营养盐影响细菌和低营养级生物。浮游植物通过产生化感物质和溶解有机物影响微食物网结构,而营养盐的浓度及变化则可以对微食物网产生直接或间接影响。     

Influencing factors of seed long-distance dispersal on a fragmented forest landscape on Changbai Mountains,China

Seed long-distance dispersal(LDD) events are typically rare, but are important in the population processes that determine large-scale forest changes and the persistence of species in fragmented landscapes. However, previous studies focused on species dispersed via animal-mediated LDD, and ignored those dispersed by wind. The aim of this study was to assess the effects of canopy openness, edge, seed source, and patch tree density on the LDD of seeds by wind in forest. We collected birch seeds, a typical wind-dispersed species, throughout a larch plantation. We then assessed the relationship between birch LDD and each factor that may influence LDD of seeds by wind including distance to edge, canopy openness size, distance to mature forest, and the tree density of the larch plantation. We used univariate linear regression analysis to assess the influence of those factors on birch LDD, and partial correlations to calculate the contribution of each factor to LDD. The results showed that both canopy openness and edge had significant influences on birch LDD. Specifically, a negative relationship was observed between distance to edge and birch LDD, whereas there was a positive correlation between canopy openness size and LDD. In contrast, the distance to the mature forest was not correlated with birch LDD. Our results suggest that patch tree density could potently affect the probability of LDD by wind vectors, which provides novel and revealing insights regarding the effect of fragmentation on wind dynamics. The data also provide compelling evidence for the previously undocumented effect of habitat fragmentation on wind-dispersed organisms. As such, these observations will facilitate reasonable conservation planning, which requires a detailed understanding of the mechanisms by which patch properties hamper the delivery of seeds of wind-dispersed plants to fragmented areas.     

An integrative study of larval organogenesis of American shad <Emphasis Type="Italic">Alosa sapidissima</Emphasis> in histological aspects

We describe organogenesis at a histological level in American shad (Alosa sapidissima) larvae from 0 until 45 days after hatching (DAH). Larval development was divided into four stages based on the feeding mode, external morphological features, and structural changes in the organs: stage 1 (0–2 DAH), stage 2 (3–5 DAH), stage 3 (6–26 DAH) and stage 4 (27–45 DAH). At early stage 2 (3 DAH), American shad larvae developed the initial digestive and absorptive tissues, including the mouth and anal opening, buccopharyngeal cavity, oesophagus, incipient stomach, anterior and posterior intestine, differentiated hepatocytes, and exocrine pancreas. The digestive and absorptive capacity developed further in stages 2 to 3, at which time the pharyngeal teeth, taste buds, gut mucosa folds, differentiated stomach, and gastric glands could be observed. Four defined compartments were discernible in the heart at 4 DAH. From 3 to 13 DAH, the excretory systems started to develop, accompanied by urinary bladder opening, the appearance and development of primordial pronephros, and the proliferation and convolution of renal tubules. Primordial gills were detected at 2 DAH, the pseudobranch was visible at 6 DAH, and the filaments and lamellae proliferated rapidly during stage 3. The primordial swim bladder was first observed at 2 DAH and started to inflate at 9 DAH; from then on, it expanded constantly. The spleen was first observed at 8 DAH and the thymus was evident at 12 DAH. From stage 4 onwards, most organs essentially manifested an increase in size, number, and complexity of tissue structure.     

基于GF 1光谱数据的青藏地区冰川资源现状遥感调查

以2014—2015年的GF 1为主、少量OLI影像为基础,参考第二次中国冰川目录等文献资料,修编完成青海省和西藏自治区两省区的现代冰川编目,查明青藏两省区目前共有冰川24 796条,总面积约2624×104 km2,约占青藏两省区区域面积的137%,冰川储量为2027×103~2121×103 km3。调查区冰川数量以面积<10 km2、冰川面积介于10~100 km2之间的冰川为主,其中面积<10 km2的冰川有19 983条,占总数量的8059%,面积介于10~100 km2之间的冰川面积为11 96240 km2,占总面积的4559%;面积最大的中锋冰川的面积达23737 km2。调查区内的山系(高原)均有冰川分布,念青唐古拉山冰川数量最多,其次是喜马拉雅山和冈底斯山,这3座山系冰川数量占调查区内冰川总数量的6333%;念青唐古拉山、喜马拉雅山和昆仑山的冰川面积和冰储量位列前3位,其冰川面积和冰储量分别占总数的6809%和7344%;然而昆仑山和羌塘高原的单条冰川的平均面积大于念青唐古拉山和喜马拉雅山的平均面积。从冰川海拔分布来看,海拔5 000~6 500 m之间是冰川集中发育区域,约占调查区冰川数量和冰川总面积的85%以上。调查区的冰川在各流域的分布差异显著,恒河流域是冰川分布数量最多、面积最大的一级外流区,其数量占冰川总量的47%以上,面积占总面积的52%以上;青藏高原内陆流域的冰川数量、面积次之,其冰川数量占总数量的21%,面积占总面积的24%以上,并且内流区单条冰川的平均面积略大于外流区的平均面积。总体上,西藏的冰川数量、面积和冰储量分别占西藏和青海两省区的8492%、8492%、8668%,单条冰川的平均面积两省区相近。     

Petrology and PGE Abundances of High‐Cr and High‐Al Podiform Chromitites and Peridotites from the Bulqiza Ultramafic Massif,Eastern Mirdita Ophiolite,Albania

The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone (SSZ). However, economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone (MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr# values (100Cr/(Cr+Al)) (47.7–55.1 and 46.5–51.7, respectively) than those in the high-Cr chromitites (78.2–80.4), harzburgites (72.6–77.9) and mantle dunites (79.4–84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements (PGE). The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10–0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO2-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.