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71.
朝鲜北部狼林地块构造归属与地壳形成时代 总被引:18,自引:18,他引:0
朝鲜半岛北部的狼林地块一直被认为是中朝克拉通的重要组成部分。传统认为,它向南与我国辽东半岛的辽南太古宙地体相接,与其北部的鞍山-辽北-吉南太古宙地体(龙岗地块)具有基本类似的物质组成。两大太古宙地体之间是著名的以辽河群、集安群和老岭群为代表的辽吉古元古代岩系。辽吉岩系目前最主要的学术争论是,它是原本一体的太古宙地体的裂解产物,还是两个性质不同的太古宙地体拼合的结果。无论采用何种模型,学术界都普遍接受狼林地块主要由太古代岩石组成这一基本假定。为准确厘定狼林地块的地壳性质与形成时代,本文选择大同江、清川江、城川江、长津江、厚州川、厚昌江和秃鲁江中的河沙样品作为研究对象。这些河流均发源于狼林山脉,是狼林地块的核心区域,因而这些河流沉积物能够较好地全面反映狼林地块的物质组成情况。上述河流不同部位8件样品的分析结果显示,狼林地块主要由18~19亿年的古元古代岩石组成,太古宙岩石比例极为有限。但锆石Hf同位素模式年龄集中在28亿年左右,与华北克拉通全岩样品的Nd同位素模式年龄基本一致。结合狼林地块大量麻粒岩相变质表壳岩系和古元古宙花岗岩的发育,本文认为狼林地块是与辽吉岩系基本类似的古元古代地体,它可能是华北克拉通在古元古代期间东南大陆边缘的巨型造山带,我们可将其简称为辽-吉-朝古元古代造山带。因此,先前认为狼林地块主要由太古宙岩石组成的观点需要重新检查和认识。 相似文献
72.
朝鲜甑山“群”变质岩中锆石-榍石-金红石U-Pb体系:古元古代-中生代构造-热事件记录 总被引:5,自引:4,他引:1
朝鲜甑山地区甑山"群"(杂岩)的主要岩石类型包括石榴云母片麻岩、石榴角闪岩,并有少量大理岩。其原岩为泥质岩为主的碎屑岩,并含有少量火山岩和碳酸盐岩,经历了角闪岩相到麻粒岩相变质作用。本文对甑山"群"2件石榴云母片麻岩和1件石榴角闪岩样品进行了锆石-榍石-金红石U-Pb体系年代学研究。石榴云母片麻岩中分选出的锆石均为变质新生锆石,Pb-Pb加权平均年龄为1850±5Ma,没有发现继承锆石组分,暗示原岩为缺乏碎屑锆石的泥质岩。石榴角闪岩中的榍石根据成因不同,可分为两期,即早期麻粒岩相变质生长的榍石和后期热事件生长榍石。早期榍石具有高U、高Th/U比值特点,U-Pb分析构成一条不一致线,上交点年龄1831±5Ma代表了早期变质热事件冷却到榍石U-Pb体系封闭温度时代,下交点年龄155±3Ma代表后期热事件造成Pb丢失时代;另一种榍石具有低U低Th/U比值特点,U-Pb年龄为单一的153±3Ma,为中生代构造热事件的新生榍石。两类样品中的金红石少量颗粒保存有早期U-Pb年龄信息,绝大多数在~155Ma发生完全重置,并直到~110Ma一直处于U-Pb体系开放状态。以上数据说明,甑山"群"在~1850Ma前发生高级变质,1850~1830Ma开始抬升出露,并成为中新元古界沉积岩物源与沉积基底,中生代受到朝鲜广泛发育的岩浆-热事件的影响。 相似文献
73.
朝鲜半岛西北部古元古代高温变质-深熔作用:宏观和微观岩石学以及锆石U-Pb年代学制约 总被引:8,自引:8,他引:0
朝鲜半岛左接中国大陆右连日本岛链,其地质位置重要不言而喻,对其区域地质演化历史和构造属性的准确厘定,直接关系到对整个东北亚地质的全面理解和认识。本文对朝鲜半岛狼林地块西部的南浦群和甄山群的相关岩石进行了研究。野外露头、手标本和岩相学观察表明,南浦群和甄山群岩石保存了深熔作用的宏观和微观证据,矿物组合以及矿物间的反应结构表明南浦群和甄山群混合岩经历了角闪岩相到麻粒岩相的变质作用,并且在晚期熔体结晶过程中发生了逆反应或退变质过程。7件样品的锆石U-Pb定年结果显示,朝鲜半岛西北部地区在古元古代经历了多阶段(期)的变质和深熔作用过程。南浦群岩石在1917Ma可能经历了第一阶段(期)变质作用,在1877~1855Ma经历了第二阶段(期)变质深熔和石榴石持续生长,熔体冷却结晶时代为1842Ma。甄山群样品给出的变质深熔和石榴石生长的时代为1841~1830Ma,1785Ma可能代表深熔作用中抽取的熔体冷却的时代。但是,为何南浦群和甄山群样品记录的变质和深熔作用时代显示较大的差异,尚需更进一步的研究。综述前人研究成果可知,狼林地块与华北克拉通东部辽吉活动带,在变质和深熔作用类型方面存在不同之处,然而它们所记录的古元古代高温变质-深熔时代的一致性,表明二者可能至少在古元古代之前就形成了统一的大陆。 相似文献
74.
Comparison of growing thalli in alternating haploid and diploid phases of Grateloupia subpectinata (Rhodophyta) was studied. Fertile thalli from gametophyte and tetrasporophyte of G. subpectinata were collected from Yangyang, on the eastern coast of Korea. The size of the released tetraspores and carpospores was measured; the spores were then incubated at the temperature of 20°C, irradiance of 40 μmol photon m-2s-1 and photoperiod of 12L and 12D. Carpospores were also cultivated in the same conditions as the tetraspores culture. The crusts were subsequently transferred to a tank culture after six months. The specific growth rate (SGR) was measured by observing 50 crusts and 30 thalli. The released carpospores had a larger diameter (9.98 μm) than the tetraspores (9.38 μm). The crusts from the carpospores also show a higher specific growth rate (14.04% d-1) than tetraspores (13.39% d-1). After being transferred and cultured in a tank, the upright thalli grew slowly in May-June (13–15°C) and rapidly in July–September (17–22°C). The length of growing thalli of sporophyte from carpospores also revealed a higher specific growth rate (2.83% d-1) than gametophytic thalli (2.38% d-1). The specific growth rate of crusts and thalli developed from carpospores was higher than that of the crusts developed from tetraspores. This result suggests that the cultivation of sporophytes may be more profitable than gametophytes because harvesting can be done more efficiently. 相似文献
75.
Despite rapidly growing interest in the effects of ocean acidification on marine animals, the ability of deep-sea animals to acclimate or adapt to reduced pH conditions has received little attention. Deep-sea species are generally thought to be less tolerant of environmental variation than shallow-living species because they inhabit relatively stable conditions for nearly all environmental parameters. To explore whether deep-sea hermit crabs (Pagurus tanneri) can acclimate to ocean acidification over several weeks, we compared behavioral “boldness,” measured as time taken to re-emerge from shells after a simulated predatory attack by a toy octopus, under ambient (pH ~7.6) and expected future (pH ~7.1) conditions. The boldness measure for crab behavioral responses did not differ between different pH treatments, suggesting that future deep-sea acidification would not influence anti-predatory behavior. However, we did not examine the effects of olfactory cues released by predators that may affect hermit crab behavior and could be influenced by changes in the ocean carbonate system driven by increasing CO2 levels. 相似文献
76.
Young-Chan NOH Byung-Ju SOHN Yoonjae KIM Sangwon JOO William BELL Roger SAUNDERS 《大气科学进展》2017,34(11):1265-1281
A new set of Infrared Atmospheric Sounding Interferometer(IASI) channels was re-selected from 314 EUMETSAT channels.In selecting channels,we calculated the impact of the individually added channel on the improvement in the analysis outputs from a one-dimensional variational analysis(1D-Var) for the Unified Model(UM) data assimilation system at the Met Office,using the channel score index(CSI) as a figure of merit.Then,200 channels were selected in order by counting each individual channel's CSI contribution.Compared with the operationally used 183 channels for the UM at the Met Office,the new set shares 149 channels,while the other 51 channels are new.Also examined is the selection from the entropy reduction method with the same 1D-Var approach.Results suggest that channel selection can be made in a more objective fashion using the proposed CSI method.This is because the most important channels can be selected across the whole IASI observation spectrum.In the experimental trial runs using the UM global assimilation system,the new channels had an overall neutral impact in terms of improvement in forecasts,as compared with results from the operational channels.However,upper-tropospheric moist biases shown in the control run with operational channels were significantly reduced in the experimental trial with the newly selected channels.The reduction of moist biases was mainly due to the additional water vapor channels,which are sensitive to the upper-tropospheric water vapor. 相似文献
77.
Using 32 CMIP5(Coupled Model Intercomparison Project Phase 5) models, this study examines the veracity in the simulation of cloud amount and their radiative effects(CREs) in the historical run driven by observed external radiative forcing for 1850–2005, and their future changes in the RCP(Representative Concentration Pathway) 4.5 scenario runs for2006–2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics,four models—ACCESS1.0, ACCESS1.3, Had GEM2-CC, and Had GEM2-ES—are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average.All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about-0.99% K~(-1)and net radiative warming of 0.46 W m~(-2)K~(-1), suggesting a role of positive feedback to global warming. 相似文献
78.
An analytical model with three sub-regions for m2 tide in the yellow sea and the East China Sea 总被引:1,自引:0,他引:1
In this study an analytical tide model of uniform width with three sub-regions is presented. The three-subregions model takes
into account step-like variations in depths in the direction of the channel as a way to examine the M2 tide of the East China Sea (ECS) as well as the Yellow Sea (YS). A modified Proudman radiation condition has been applied
at the northern open head, while the sea surface elevation is specified at the southern open boundary. It is seen that, due
to the presence of an abrupt change in depth, co-amplitude lines of the M2 tide are splitted to the east and west near the end of the ECS shelf region. Variations in depths, bottom friction and the
open head boundary conditions all contribute to the determination of formation of amphidromes as well as overall patterns
of M2 tidal distribution. It is seen that increasing water depth and bottom friction in the ECS shelf results in the westward shift
of the southern amphidrome. There is however no hint at all of the well-known degenerated tidal pattern being formed. It is
inferred that a lateral variation of water depth has to be somehow incorporated to represent the tidal patterns in ECS in
a realistic manner. Regarding the radiation factor introduced by Fang et al. (1991), use of a value larger than one, possibly
with a phase shift, appears to be a proper way of incorporating the reflected waves from the northern Yellow Sea (NYS). Key
words - analytical model, M2 tide, Kelvin wave, Yellow Sea, East China Sea 相似文献
79.
A teleconnection pattern in upper-level meridional wind over the North African and Eurasian continent in summer 总被引:8,自引:0,他引:8
One-point correlation analysis on upper-level meridional wind identified the existence of a teleconnection pattern in July, which emerges from North Africa to East Asia along the westerly jet in the middle latitudes. We examined the spatial and temporal structures of this teleconnection pattern, and found the unique characteristics rather different from the patterns in other elements such as geopotential height, streamfunction and vorticity. We also investigated the relationship between this teleconnection and precipitation, and suggested that the teleconnection is a possible linkage of the EASM to the Indian monsoon, and even to subtropical heating anomalies over Atlantic. 相似文献
80.
In this study,an advanced probabilistic neural network(APNN)method is proposed to reflect the global probability density function(PDF)by summing up the heterogeneous local PDF which is automatically determined in the individual standard deviation of variables.The APNN is applied to predict the stability number of armor blocks of breakwaters using the experimental data of van der Meer,and the estimated results of the APNN are compared with those of an empirical formula and a previous artificial neural network(ANN)model.The APNN shows better results in predicting the stability number of armor blocks of breakwater and it provided the promising probabilistic viewpoints by using the individual standard deviation in a variable. 相似文献