青藏高原及邻区未来地震活动性趋势数值分析          下载免费PDF全文

董培育  石耀霖  程惠红  乔学军 《地球物理学报》2020,63(3):1155-1169

区域中长期地震危险性数值分析研究,需要对其初始构造应力场有所了解,但目前以及未来一段时期内仍无法直接观测到深部孕震层区域的应力场状况.本文首先基于岩石库仑-摩尔破裂准则,利用青藏高原及邻区百年历史范围内的强震信息,来反演估算该区域的初始应力场.然后,考虑区域构造应力加载及强震造成的应力扰动共同作用,重现了历史强震的发展过程.然而对于初始应力场的反演估算,本文仅能给出区域其上下限的极限值,并不能唯一确定.因此,采用Monte Carlo随机法,进行大量独立的随机试验计算,生成数千种有差异的区域初始应力场模型,且保证每种模型都能令历史强震有序发生,但未来应力场演化过程不尽相同.最后,将数千种模型在未来时间段内的危险性预测结果集成为数理统计结果,据此给出了区域未来的地震危险性概率分布图.初步结果显示未来强震危险性概率较高地区集中在巴颜喀拉块体边界及鲜水河断裂带地区.  相似文献   

江西相山酸性火山-侵入杂岩精确年代学与演化序列研究   总被引：7，自引：0，他引：7       下载免费PDF全文

郭福生  杨庆坤  谢财富  孟祥金  周万蓬  姜勇彪  张树明  吴志春 《地质科学》2015,(3):684-707

相山火山盆地主体岩石为一套由熔结凝灰岩、流纹英安岩、流纹英安斑岩、碎斑熔岩、粗斑花岗斑岩及似斑状花岗岩组成的酸性火山-侵入杂岩体, 构成了两个完整的喷发-溢流(侵出)-侵入的岩浆活动亚旋回。本文在野外地质调查的基础上, 采用SIMS、LA-ICP-MS技术对主要岩类进行了高精度的锆石U-Pb年代学研究, 并建立了火山-侵入杂岩体的演化序列。结果表明, 打鼓顶组熔结凝灰岩代表了相山火山-侵入活动的最早期产物, 其锆石U-Pb年龄为140.7±2.7 Ma、140.1±1.8 Ma和138.2±1.6 Ma, 第一亚旋回主体流纹英安岩的锆石U-Pb年龄135.0±1.8 Ma。鹅湖岭组熔结凝灰岩代表了火山-侵入活动的第二亚旋回的开始, 其U-Pb年龄为135.6±1.2 Ma, 第二亚旋回主体碎斑熔岩的锆石U-Pb年龄133.6±1.3 Ma, 沙洲单元的粗斑花岗斑岩和似斑状花岗岩属于该亚旋回最晚期的侵入岩, 其锆石U-Pb年龄代表了相山火山-侵入活动的结束时间(分别为133.4±1.2 Ma和133.9±1.1 Ma)。相山早白垩世火山-侵入活动延续时间较短, 整体上呈现一个连续的过程, 初始时间在141 Ma附近, 结束时间在132 Ma左右。概言之, 第一亚旋回(141~135 Ma)以形成熔结凝灰岩、流纹英安岩和流纹英安斑岩为主, 第二亚旋回(135~132 Ma)以熔结凝灰岩、碎斑熔岩、粗斑花岗斑岩和似斑状花岗岩为主。岩石地球化学和野外地质特征也与两个亚旋回火山-侵入岩浆活动相吻合。  相似文献   

2007年12月南京六次雨雾过程宏、微观结构演变特征   总被引：4，自引：1，他引：3  

于华英  牛生杰  刘鹏  刘畅  陆春松  黄佳欢 《大气科学》2015,39(1):47-58

利用2007年冬季南京信息工程大学对雾的综合观测资料,包括能见度仪、雨滴谱仪、雾滴谱仪、宽范围颗粒粒径谱仪(WPS)观测资料,并结合地面常规气象观测资料和NCEP(National Centers for Environmental Prediction)再分析资料,分析2007年12月南京六次雨雾过程的宏、微观结构演变特征。结果显示:(1)南京2007年12月的六次雨雾过程主要是受天气系统的影响,以雨中雾为主,最低能见度均大于250 m。雨雾多出现在偏东气流的作用下,南京地区先发生弱降水,空气近饱和,随后受到来自北方的弱冷空气影响,水汽凝结,雾形成。(2)雨雾发生前贴地层多有逆温,雨雾过程中2 m高度与地表温度差由正转为负,逆温消失。但900 hPa以下,雨雾发生前和过程中,都少有逆温层,雨雾结束后均无逆温结构。雨雾前中低层有云,云状为高积云Ac或高层云As及层积云Sc或碎雨云Fn,低云高0.3～2.5 km,雨雾过程中,600 hPa以下都是饱和层,多伴有Fn,低云高度明显下降,雨雾过后,近饱和层仍然有可能存在。雨雾前900 hPa附近有明显的风切变。(3)雨雾形成初期,大粒子(粒子直径D≥10 μm)和小粒子(1 μm相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987114000917     

Miyuki Tahata  Yusuke Sawaki  Yuichiro Ueno  Manabu Nishizawa  Naohiro Yoshida  Toshikazu Ebisuzaki  Tsuyoshi Komiya  Shigenori Maruyama 《地学前缘(英文版)》2015,6(1):121-136

Important ecological changes of the Earth(oxidization of the atmosphere and the ocean) increase in nutrient supply due to the break-up of the super continent(Rodinia) and the appearance of multi-cellular organisms(macroscopic algae and metazoan) took place in the Ediacaran period,priming the Cambrian explosion.The strong perturbations in carbon cycles in the ocean are recorded as excursions in carbonate and organic carbon isotope ratio(δ~(13)C_(carb) and δ~(13)C_(org)) from the Ediacaran through early Cambrian periods.The Ediacaran-early Cambrian sediment records of δ~(13)C_(carb) and δ~(13)C_(org),obtained from the drill-core samples in Three Gorges in South China,are compared with the results of numerical simulation of a simple one-zone model of the carbon cycle of the ocean,which has two reservoirs(i.e.,dissolved organic carbon(DOC) and dissolved inorganic carbon(DIC).The fluxes from the reservoirs are assumed to be proportional to the mass of the carbon reservoirs.We constructed a model,referred to here as the Best Fit Model(BFM),which reproduce δ~(13)C_(carb) and δ~(13)C_(org) records in the Ediacaran-early Cambrian period noted above.BFM reveals that the Shuram excursion is related to three major changes in the carbon cycle or the global ecological system of the Earth:(1) an increase in the coefficient of remineralization by a factor of ca.100,possibly corresponding to a change in the dominant metabolism from anaerobic respiration to aerobic respiration,(2) an increase of carbon fractionation index from 25‰ to 33‰,possibly corresponding to the change in the primary producer from rock-living cyanobacteria to free-living macro algae,and(3) an increase in the coefficient of the organic carbon burial by a factor of ca.100,possibly corresponding to the onset of a biological pump driven by the flourishing metazoan and zooplankton.The former two changes took place at the start of the Shuram excursion,while the third occurred at the end of the Shuram excursion.The other two excursions are explained by the tentative decrease in primary production due to cold periods,which correspond to the Gaskiers(ca.580 Ma) and Bikonor(ca.542 Ma) glaciations.  相似文献   

New rebbachisaurid (Dinosauria: Sauropoda) material from the Wessex Formation (Barremian, Early Cretaceous), Isle of Wight, United Kingdom     

Philip D. Mannion  Paul Upchurch  Stephen Hutt 《Cretaceous Research》2011,32(6):774-780

Rebbachisauridae is a poorly understood clade of diplodocoid sauropod dinosaurs, currently known only from the Cretaceous of Africa, Europe and South America. European representatives are particularly rare and fragmentary. Here, we report an anterior caudal vertebra from the Barremian (Early Cretaceous) Wessex Formation of the Isle of Wight, off the southern coast of England. This specimen possesses several features known only in rebbachisaurids and shares two synapomorphies with the Afro-European taxa Demandasaurus darwini and Nigersaurus taqueti, both pertaining to the morphology of the neural spine. These features are the development of triangular lateral processes and the presence of an elliptical fossa on the lateral surface, bounded by the lateral lamina and postspinal rugosity. The Isle of Wight specimen also shares several features solely with Demandasaurus, indicating a close relationship with the Spanish taxon. These include the presence of a hyposphenal ridge, as well as an anteriorly excavated caudal rib that is restricted almost entirely to the neural arch. However, it differs from Demandasaurus in a number of ways, including the lack of excavation on the posterior surface of the caudal rib, the orientation of the neural spine, and the composition and morphology of the lateral lamina. In addition, the Isle of Wight vertebra possesses one potential autapomorphy: bifurcation of the elliptical fossa on the neural spine. However, because of the fragmentary nature of the material, a new name is not erected. Along with Demandasaurus and Histriasaurus boscarollii, this caudal vertebra indicates the presence of at least three European rebbachisaurid taxa and provides new anatomical information on this enigmatic clade of sauropod dinosaurs.  相似文献   

山东省地下水环境演化规律          下载免费PDF全文

张中祥  罗斐  张海林 《山东国土资源》2018,34(10)

地下水环境演化是地下水系统在自然因素和人为因素影响下,发生在地质环境空间内质与量的变化过程和结果。在自然因素中地理、地质等条件可视为基本不变,最主要的是气候条件的变化,而大气降水又是气候条件中最为活跃的因子,其余如温度、风速虽也影响水分的蒸发,但年际变化不如降水大,故以狭义的降水来代表广义的气候条件。人类工程活动因素则主要是抽取地下水和污染物排放,这些因素的变化最终导致的是地下水动力场和化学场的变化。人类工程活动主要是抽取地下水和污染物排放,这些因素变化最终导致的是地下水动力场和化学场的变化。基于这一观点,以1978年为基准年,通过地下水动力场和化学场演化研究结果,采用"地下水环境演化综合指数法",对全省地下水环境演化程度进行综合评价,划分出"优向演化区、波动平衡区、劣向演化区",是对近30多年来人类工程活动影响下,山东省地下水环境演化规律的系统总结。  相似文献   

The Late Jurassic ray Kimmerobatis etchesi gen. et sp. nov. and the Jurassic radiation of the Batoidea     

《Proceedings of the Geologists' Association. Geologists' Association》2019,130(3-4):345-354

The laminated marine mudstones of the Late Jurassic of Kimmeridge, southern England, yield two exceptionally well-preserved partial skeletons of a previously unrecognised species of early batoid. These are described as a new genus and species, Kimmerobatis etchesi gen. et sp. nov. which has a general “guitarfish” bauplan as in all other batoids known from the Jurassic. This species possesses a combination of primitive characters such as centra present within the majority of the synarcual and antorbital cartilages that fail to reach the pectoral skeleton along with more derived characters, such as the lack of fin spines. Until now, little study has been carried out on the affinities of Jurassic batoids, despite their key role in understanding batoid evolution. Results from parsimony and likelihood phylogenetic reconstruction indicates that the whole-bodied Jurassic batoids Spathobatis, Belemnobatis, and Kimmerobatis gen. nov. form their own clade, Spathobatidae, and do not lend support to a monophyletic “Rhinobatidae”. Among Jurassic batoids, Kimmerobatis gen. nov. is most derived, but with derived characters being independently acquired compared to modern batoids (e.g. presence of a postpelvic process). The inclusion of whole bodied Jurassic fossils have generated a more resolved hypothesis of batoid evolution throughout the Cretaceous and into the Cenozoic.  相似文献   

In situ Pb and bulk Sr isotope analysis of the Yinchanggou Pb-Zn deposit in Sichuan Province (SW China): Constraints on the origin and evolution of hydrothermal fluids     

《Ore Geology Reviews》2017

The Yinchanggou Pb-Zn deposit, located in southwestern Sichuan Province, western Yangtze Block, is stratigraphically controlled by late Ediacaran Dengying Formation and contains >0.3 Mt of metal reserves with 11 wt% Pb + Zn. A principal feature is that this deposit is structurally controlled by normal faults, whereas other typical deposits nearby (e.g. Maozu) are controlled by reverse faults. The origin of the Yinchanggou deposit is still controversial. Ore genetic models, based on conventional whole-rock isotope tracers, favor either sedimentary basin brine, magmatic water or metamorphic fluid sources. Here we use in situ Pb and bulk Sr isotope features of sulfide minerals to constrain the origin and evolution of hydrothermal fluids. The Pb isotope compositions of galena determined by femtosecond LA-MC-ICPMS are as follows: ²⁰⁶Pb/²⁰⁴Pb = 18.17–18.24, ²⁰⁷Pb/²⁰⁴Pb = 15.69–15.71, ²⁰⁸Pb/²⁰⁴Pb = 38.51–38.63. These in situ Pb isotope data overlap with bulk-chemistry Pb isotope compositions of sulfide minerals (²⁰⁶Pb/²⁰⁴Pb = 18.11–18.40, ²⁰⁷Pb/²⁰⁴Pb = 15.66–15.76, ²⁰⁸Pb/²⁰⁴Pb = 38.25–38.88), and both sets of data plotting above the Pb evolution curve of average upper continental crust. Such Pb isotope signatures suggest an upper crustal source of Pb. In addition, the coarse-grained galena in massive ore collected from the deep part has higher ²⁰⁶Pb/²⁰⁴Pb ratios (18.18–18.24) than the fine-grained galena in stockwork ore sampled from the shallow part (²⁰⁶Pb/²⁰⁴Pb = 18.17–18.19), whereas the latter has higher ²⁰⁸Pb/²⁰⁴Pb ratios (38.59–38.63) than the former (²⁰⁸Pb/²⁰⁴Pb = 38.51–38.59). However, both types of galena have the same ²⁰⁷Pb/²⁰⁴Pb ratios (15.69–15.71). This implies two independent Pb sources, and the metal Pb derived from the basement metamorphic rocks was dominant during the early phase of ore formation in the deep part, whereas the ore-hosting sedimentary rocks supplied the majority of metal Pb at the late phase in the shallow part. In addition, sphalerite separated from different levels has initial ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7101 to 0.7130, which are higher than the ore formation age-corrected ⁸⁷Sr/⁸⁶Sr ratios of country sedimentary rocks (⁸⁷Sr/⁸⁶Sr_200 Ma = 0.7083–0.7096), but are significantly lower than those of the ore formation age-corrected basement rocks (⁸⁷Sr/⁸⁶Sr_200 Ma = 0.7243–0.7288). Again, such Sr isotope signatures suggest that the above two Pb sources were involved in ore formation. Hence, the gradually mixing process of mineralizing elements and associated fluids plays a key role in the precipitation of sulfide minerals at the Yinchanggou ore district. Integrating all the evidence, we interpret the Yinchanggou deposit as a strata-bound, normal fault-controlled epigenetic deposit that formed during the late Indosinian. We also propose that the massive ore is formed earlier than the stockwork ore, and the temporal-spatial variations of Pb and Sr isotopes suggest a certain potential of ore prospecting in the deep mining area.  相似文献   

岱崮地貌的基本特征、成因和演化          下载免费PDF全文

王 萌 李 理 周雄杰 王 博游远征  戴伊宁李 圯 辛 文 《地质科学》2017,(2):628-636

岱崮地貌是一种寒武系碎屑岩之上的平顶灰岩地貌，为中国五大地貌之一，对其研究具有地质学、古地理环境等科学意义。本文通过野外地质调查及室内研究，分析研究了岱崮地貌的特征、成因和演化，得出以下结论：1） 岱崮镇的崮主体呈NW向展布，由崮体和崮基组成。崮体包括崮顶、崮腰和崮底，崮顶为灰岩，崮腰和崮底以碎屑岩为主，崮基为前寒武系岩浆岩或太古宇泰山群；2） 近水平岩层是岱崮地貌发育的基础；3） NNW向、NW向和近EW向断层是岱崮地貌形成的根本因素，NW向和NE 向节理是主控因素，控制了岱崮地貌的走向、密度；4） 岱崮地貌古生代以来经历了多个时期的演化，经过加里东运动、海西运动和印支运动留存的寒武系-中奥陶统、上石炭统-二叠系是岱崮地貌形成的基础，燕山期中侏罗世末-晚侏罗世（162～149.8 Ma）、白垩纪（140～90 Ma）及喜马拉雅早期（65～43 Ma）产生的断层及节理是岱崮地。  相似文献   

我国海洋经济劳动生产率区域差异与演变分析          下载免费PDF全文

计利群  狄乾斌 《海洋开发与管理》2017,34(9):65-71

劳动生产率差异是导致区域经济发展差异的重要原因,提高劳动生产率是促进经济增长的有效手段。分析我国海洋经济的劳动生产率的区域差异与演变对发展我国海洋经济具有积极意义。在分析我国海洋经济劳动生产率的特点基础上,文章运用基尼系数和泰尔指数计算我国沿海地区1997—2014年海洋经济劳动生产率区域差异,并进行σ-收敛性检验,结果表明区域差异呈现倒V字形走势,1997—2005年呈现σ-发散,2005—2014年呈现σ-收敛。采用泰尔指数分解方法测度表明,环渤海、长三角、泛珠三角三大经济区海洋经济劳动生产率地区内差异占总体差异的比重达80%以上,而地区间差异比重较小,环渤海经济区地区内差异最大。分阶段对我国各沿海地区海洋经济的劳动生产率进行排名并观察演变过程。提出提高我国海洋经济劳动生产率的相关建议:一是努力提高海洋经济全要素生产率;二是促进海洋产业合理布局,努力提高传统海洋产业劳动生产率;三是统筹区域海洋经济发展。  相似文献