On the absence of the (0, 0) C2 Swan band from sunspot spectra     

David Branch 《Solar physics》1969,10(1):112-114

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Gold and tin of fluid-magmatic systems:causes of combination-separation of concentration elements     

I.I. Fatyanov  V.G. Khomich 《东北亚地学研究》2009,(3)

The aim of the investigation is to reveal possible causes of isolation and co-occurrence of the economically significant concentrations of gold and tin. Comparative analysis of the different-rank factors that influenced migration and concentration of these elements show that different geochemical properties of Au and Sn are responsible for isolation of their big concentrations giving rise to independent metallogenic provinces, zones, and ore nodes. These differences resulted in individualization of the elem...  相似文献   

Paleoproterozoic,High-Metamorphic,Metasedimentary Units of Siberian Craton     

Lena URMANTSEVA  Olga TURKINA 《《地质学报》英文版》2009,83(5):875-883

Abstract: Sensitive, high-resolution ion microprobe zircon U–Pb ages of Paleoproterozoic, high-grade, metasedimentary rocks from the south-western part of the Siberian Craton are reported. Early Precambrian, high-grade complexes, including garnet–biotite, hypersthene–biotite, and cordierite-bearing gneisses compose the Irkut terrane of the Sharyzhalgay Uplift. Protoliths of studied gneisses correspond to terrigenous sediments, ranging from greywacke to shale. The paragneiss model Nd ages of 2.4–3.1 Ga indicate Archean-to-Paleoproterozoic source provinces. Zircons from gneisses show core-rim textures in cathodoluminescence (CL) image. Round or irregular shaped cores indicate detrital origin. Structureless rims with low Th/U are metamorphic in origin. The three age groups of detrital cores are: ≥2.7, ~2.3, and 1.95–2 Ga. The ages of metamorphic rims range from 1.86 to 1.85 Ga; therefore, the sediments were deposited between 1.95 and 1.86 Ga and derived from Archean and Paleoproterozoic source rocks. It should be noted that Paleoproterozoic metasedimentary rocks of the Irkut Block are not unique. High-grade metaterrigenous sediments, with model Nd ages ranging from 2.3 to 2.5 Ga, are widely distributed within the Aldan and Anabar Shields of the Siberian Craton. The same situation is observed in the North China Craton, where metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 to 2.1 Ga (Wan et al., 2006). All of these sedimentary units were subjected to Late Paleoproterozoic metamorphism. In the Siberian Craton, the Paleoproterozoic sedimentary deposits are possibly marked passive margins of the Early Precambrian crustal blocks, and their high-grade metamorphism was related to the consolidation of the Siberian Craton.  相似文献   

Sand-mediated divergence between shallow reef communities on horizontal and vertical substrata in the western Indian Ocean     

SN Porter  GM Branch  KJ Sink 《African Journal of Marine Science》2017,39(1):121-127

Distinctions are rarely made between vertical and horizontal surfaces when assessing reef community composition, yet physical differences are expected because of hydrodynamic differences and sediment accumulation on flat surfaces. As sand often diminishes biotic cover, we hypothesised that vertical surfaces will support a greater biomass but have lower diversity due to domination by a few species. To test this, we quantified sessile communities on vertical and horizontal surfaces at three sites in the Delagoa Bioregion on the east coast of South Africa. Community composition consistently differed: vertical communities were dominated by various filter feeders, especially the ascidian Pyura stolonifera, whereas those on horizontal reef comprised a mixture of filter feeders and various algae. The total number of species and all diversity metrics were significantly greater for horizontal reef surfaces. Contrastingly, Simpson’s dominance and biomass were significantly greater for vertical reef surfaces. Percentage cover of sand explained much of the variation in community composition whereas depth did not. Small-scale topographic differences in substratum orientation associated with differences in sand inundation will therefore influence both α and β diversity. Coastal developments and activities that alter sand movements and delivery to the coastal zone are therefore likely to have a profound influence on the maintenance and diversity of shallow subtidal communities.  相似文献   

内蒙古集宁盆地阿尔布期——土伦期新地层的发现     

李艳霞钟宁宁  张枝焕刘琴周小惠  陶明华 《地质论评》2005,51(1):77-85,i002

在集宁盆地商都坳陷，首次应用丰富的孢粉、介形类和轮藻等化石资料论证并命名了一套新地层，自下而上为高勿素组和大囫囵组，在高勿素组中分别建立了孢粉Ⅰ．Cyathidites—Aequitriradites—Pilosisporites—Tricol popollenites组合；介形类Ⅰ．Mongolocypris infidelis—M．tera—M．longa组合；轮藻I．Obtusochara niaoheensis—Atopochara alanensis—S phaerochara datongensis组合。在大囫囵组中建立了孢粉Ⅱ．Schizaeoisporites—Taxodiaceaepollenites组合，包括2个亚组合，即①Cicatricosisporites-Classopollis亚组合，②Tricolpites-Polyporites亚组合；介形类Ⅱ．Mongolocypris cf．infidelis-M．cf．tera组合；轮藻Ⅱ．Grambastichara yuntaishanensis—Hornichara productas—Raskyaechara wumengensis组合。根据上述微体古生物化石，认为高勿素组相当于早白垩世晚期的阿尔布期，大囫囵组相当于晚白垩世早期的赛诺曼—土伦期。  相似文献   

内蒙古东部阿荣旗地区晚白垩世孤山镇组的建立     

孙广瑞  赵焕利  韩彦东  马江水  刘旭光  沙环宇  周世强  马丽玲 《地质通报》2005,24(9):862-866

通过1：25万阿荣旗幅地质调查，在阿荣旗孤山镇-东亚东镇一带发现一套酸-中酸碱性火山岩石组合，时代为晚白垩世，将其新建岩石地层单位——孤山镇组。孤山镇组主要分布于大杨树盆地南部，由流纹岩、流纹质火山碎屑岩、粗面岩和英安岩组成，上覆地层为嫩江组，下伏地层为甘河组。岩石高碱（Na2O＋K2O=7．83％-10．28％），属酸碱性系列。轻稀元素土富集，δEu=0．39-1．07；Nb、Ta基本无亏损，P、Ti强烈亏损，可能形成于陆内断陷盆地活动结束时期。  相似文献   

西藏羌北地区石炭纪■类动物群及其分带     

CHENG Li-ren  CHEN Shou-ming  ZHANG Yi-chun    WU Shui-zhong.College of Earth Sciences  Jilin University  Changchun  China.Nanjing Institute of Geology  Palaeontology  Chinese Academy of Sciences  Nanjing  China.Qinhuangdao Branch  Northeast University  Qinhuangdao  Hebei  China 《吉林大学学报(地球科学版)》2007,(1)

西藏羌北地区石炭纪■类动物群是笔者等于2004年首次发现的,并将动物群所在层位建立了瓦垄山组,该套地层中产大量的■类化石,种属多,分布连续。经研究,自下而上建立6个■类化石带:(1)Eosta ffella mosquensis带,(2)Millerella-Eostaf fella带,(3)Pseudostaf fella-Eostaf fella带,(4)Pro-fusuliena带,(5)Fusulina-Fusulinella带,(6)Protriticites-Triticites带。该套含竹蜓类化石地层的发现,为研究羌北地区晚古生代构造活动提供了信息,也为研究该区石炭纪地层、古生物、生物古地理、区域性地层划分和对比提供了依据。  相似文献   

济阳坳陷老斜452井介形类化石及其地层意义     

DENG Mei-yin  CHUN Ping  LI Jia-gui  GE Rui-quanGeological Logging Branch of Shengli Oilfield Company  SINOPEC  Dongying 《地层学杂志》2007,(Z2)

在对济阳坳陷老斜452井的古生物分析中,发现穴状女星介(相似种)Cypridea(Cypridea)cf.cavernosa、蒙阴女星介C.(C.)mengyinensis等介形类化石,说明该地区发育了白垩纪地层。济阳坳陷中生代地层的细分主要是依据区域岩性、电性及孢粉化石等地质资料,但白垩系的岩性、电性与上下地层相似,且化石稀少,缺乏充足的古生物资料,因此难以系统、准确地划分。老斜452井发现介形类化石给济阳坳陷白垩系的细分提供了重要的古生物学依据,为该区的深入研究提供了翔实的基础资料。  相似文献   

Low-luminosity Type II supernovae: spectroscopic and photometric evolution     

A. Pastorello  L. Zampieri  M. Turatto  E. Cappellaro  W. P. S. Meikle  S. Benetti  D. Branch  E. Baron  F. Patat  M. Armstrong  G. Altavilla  M. Salvo  M. Riello 《Monthly notices of the Royal Astronomical Society》2004,347(1):74-94

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东营凹陷广饶海相灰岩油藏的勘探与成因机制探讨   总被引：1，自引：1，他引：0  

李春光 《海相油气地质》1998,3(2):22-28

山东东营凹陷南部的广饶油藏为一奥陶系灰岩残丘山整带含稠油的大潜山油藏,其埋藏深度为６３４．４￣１５７５．０ｍ,现已探明含油面积３０．７ｋｍ＾２。１９９０年发现一个山头含油,１９９１￣１９９３年发现多个山头含油,１９９６￣１９９７年在各山头之间的部位钻探,结果探明潜山带南部整带含油。地质和地球化学资料分析证实,该油藏不仅是今生储潜山油藏,还是烃类经基岩风化壳运移、聚集而形成的稠油油藏。形成稠油的主要  相似文献