中国东南部下地壳物质与花岗岩成因探索   总被引：46，自引：6，他引：40  

徐夕生 ORei.  SY 《岩石学报》1999,15(2):217-223

在中国东南部中－新生代玄武质岩石中陆续找到了来自下地壳的辉长岩质麻粒岩／辉长岩深源捕掳体。本文着重研究了沿海地区广东麒麟新生代玄武质角砾岩筒中的辉长岩质麻粒岩捕掳体,并与内陆湖南道县早中生代玄武质角砾岩筒中的辉长岩、花岗片麻岩捕掳体作了比较。研究表明,辉长岩质麻粒岩是底侵作用形成的基性岩浆底垫于下地壳,并经变质作用的产物。底侵作用是重要的壳－幔作用过程,也是中国东南大陆边缘陆壳演化的重要过程。Ｓｍ－Ｎｄ同位素定年显示,中国东南大陆边缘底侵作用物质在地壳底部的结晶年龄约为１１２．３±１７．８Ｍａ,属晚中生代时期。此外,底侵作用在不同大地构造域的发育程度是不一致的,底侵作用发育强弱的标志是基性火山岩是否发育、壳幔型花岗岩是否广泛产出  相似文献   

Influence of Crude Oil on Denitrification in Subtidal Sediments in the Northern Gulf of Mexico     

《洁净——土壤、空气、水》2017,45(9)

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甘肃东南地区温泉流体地球化学特征     

吕超甲  刘雷  周晓成  杜建国  易丽 《地震》2017,37(1):52-60

根据氢、 氧、 氦同位素与水化学组分资料, 讨论了甘肃东南地区温泉水的来源、 地球化学变化及其与2008年汶川M_S8.0地震的关系。 测定结果表明: 样品的溶解性固体总量(TDS)范围为241.7~2 372.1 mg/L。 采集的7处温泉(通渭汤池河温泉、 清水地震台、 天水地震台、 武山地震台、 武山22号井、 成县地震台、 武都地震台)水样可归为四种化学类型: Na·Ca-SO₄、 Ca·Mg-SO₄、 Na-HCO₃·SO₄、 Ca·Mg-SO₄·HCO₃。 地下热水的化学类型与裂隙深度和围岩的岩性有关, 离子浓度和断裂深度基本成正相关。 通渭汤池河温泉和武都地震台的δ18O和δD值分别在-11.4‰ ~ -7.6‰和-85.7‰ ~ -57.1‰的范围内, 通渭汤池河温泉和武都地震台中³He/⁴He的值分别为0.4×10^-7和12.7×10^-7。 氢、 氧、 氦同位素组成特征表明温泉水源于大气降水, 在循环过程中经历了水岩反应, 且可能有地表水的混入。 2008年汶川M_S8.0地震发生后, 研究区域内温泉水中K⁺、 Ca²⁺含量总体上升, SO^2-₄、 Cl^-含量总体下降, Na⁺含量变化不明显; 热水循环深度受地震影响发生变化。 本文确定了甘肃东南地区温泉来源、 水化学类型成因及其与汶川M_S8.0地震的关系。  相似文献   

江苏太湖第四纪沉积环境   总被引：3，自引：0，他引：3  

陈义华 《江苏地质》2000,24(2):87-90

依据江苏太湖２２３’钻孔岩心的古地磁极性和沉积相分析,结合对比本区其他钻孔岩心资料,简要根据了江苏太湖第四纪沉积环境,早更新世时期,太湖区域曾是山间洪积扇与炭酸盐湖的沉积环境,中更新世时期,太湖平原为河湖交替的沉积环境。晚更新世时期,太湖平源三次遭受海水入侵,以致河湖喾环境曾三度变为潮坪沉积环境。全新世以来,太湖区域显现今日景观。  相似文献   

Isotopic fingerprints on lacustrine organic matter from Laguna Potrok Aike (southern Patagonia, Argentina) reflect environmental changes during the last 16,000 years     

Christoph Mayr  Andreas Lücke  Nora I. Maidana  Michael Wille  Torsten Haberzettl  Hugo Corbella  Christian Ohlendorf  Frank Schäbitz  Michael Fey  Stephanie Janssen  Bernd Zolitschka 《Journal of Paleolimnology》2009,42(1):81-102

A combination of carbon-to-nitrogen ratios (TOC/TN), Rock Eval-analyses, and stable isotope values of bulk nitrogen (δ¹⁵N) and organic carbon (δ¹³C_org) was used to characterize bulk organic matter (OM) of a piston core from the Patagonian maar lake Laguna Potrok Aike (Argentina) for the purpose of palaeoenvironmental reconstruction. Sedimentary data were compared with geochemical signatures of potential OM sources from Laguna Potrok Aike and its catchment area to identify the sources of sedimentary OM. Correlation patterns between isotopic data and TOC/TN ratios allowed differentiation of five distinct phases with different OM composition. Before 8470 calibrated ¹⁴C years before present (cal. yrs BP) and after 7400 cal. yrs BP, isotopic and organo-geochemical fingerprints indicate that the sediments of Laguna Potrok Aike consist predominantly of soil and diatom OM with varying admixtures of cyanobacterial and aquatic macrophyte OM. For a short phase of the early Holocene (ca. 8470–7400 cal. yrs BP), however, extremely high input of soil OM is implied by isotopic fingerprints. Previous seismic and geochronological results indicate a severe lake-level drop of 33 m below present-day shortly before 6590 cal. yrs BP. It is suggested that this lake level drop was accompanied by increased erosion of shore banks and channel incision enhancing soil OM deposition in the lake basin. Thus, isotopic data can be linked to hydrological variations at Laguna Potrok Aike and allow a more precise dating of this extremely low lake level. An isotopic mixing model was used including four different sources (soil, cyanobacteria, diatom and aquatic macrophyte OM) to model OM variations and the model results were compared with quantitative microfossil data.  相似文献   

Boron Isotopic Composition of Freshwater Lakes from Central Europe and Possible Contamination Sources     

A. Vengosh  S. Barth  K. G. Heumann  S. Eisenhut 《洁净——土壤、空气、水》1999,27(6):416-421

The boron isotopic compositions of common synthetic boron products, municipal wastewaters from Switzerland, and three Swiss freshwater lakes were investigated. The δ11B values (δ11B values are normalized to the standard NIST SRM-951) of synthetic Na-borates (–0.4 to 7.6‰) and Ca-Na-borates (–13.4 to –4.9‰) overlap with those of natural borate minerals and hence suggest that the isotopic signal of anthropogenic boron is not modified during the manufacturing process. As a result it is possible to predict the isotopic composition of synthetic boron products and their potential impact upon contamination of water resources. The δ11B values of municipal wastewaters from two locations in northern Switzerland (–7.7 to –4.5‰) reflect utilization of Na/Ca- and/or Ca-borates depleted in 11B. Freshwater lakes from Switzerland (Lake Zürich, Greifensee, Lake Lugano) yielded a δ11B range of –1.7 to 7.1‰ and boron concentrations of 17 to 102 mg L–1. The boron isotopic ratios decrease with increasing boron concentrations, indicating mixing between anthropogenic boron with a low δ11B signature and meteoric boron with a heavier isotopic signal. We suggest that the isotopic composition of meteoric boron over central Europe has δ11B values in the range of ca. 10 to 20‰, whereas in coastal areas the marine component is larger with a higher 11B/10B ratio (δ11B ∼ 30‰).  相似文献   

Trace-element characteristics of east–west mantle geochemical hemispheres     

Hikaru Iwamori  Hitomi Nakamura  Masaki Yoshida  Takashi Nakagawa  Kenta Ueki  Atsushi Nakao  Tatsuji Nishizawa  Satoru Haraguchi 《Comptes Rendus Geoscience》2019,351(2-3):209-220

Recent statistical analyses on the isotopic compositions of oceanic, arc, and continental basalts have revealed that the Earth's mantle is broadly divided into eastern and western hemispheres. The present study aimed to characterize the isotopically defined east–west geochemical hemispheres using trace-element concentrations. Basalt data with Rb, Sr, Nd, Sm, Pb, Th, and U in addition to the isotopic ratios ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb were selected mostly from the GEOROC and PetDB databases. A total of 4787 samples were used to investigate the global geochemical variations. The results show that the wide trace-element variations are broadly explained by the melting of melt-metasomatized and fluid-metasomatized mantle sources. The larger amount of the fluid component derived from subducted plates in the eastern hemisphere than that in the western hemisphere is inferred from the basalts. These characteristics support the hypothesis that focused subduction towards the supercontinent created the mantle geochemical hemispheres.  相似文献   

Research on basic characteristics of 2H, 18O and 14C in geothermal fluid in Guangdong Province,China     

ZENG Tu-rong 《地下水科学与工程》2019,7(1):42-52

In general, previous geothermal geochemical studies in Guangdong Province mainly involves single method to cover limited aspects and areas. In that way, various methods available cannot actually provide more convincing results of geothermal fluid's circulation system and evolution process from different dimensions, especially in terms of isotope. As a result, more comprehensive researches remain to be done on geochemistry of geothermal fluid, in particular, the space-time law of isotope's evolution pattern as well as recharge cycle. Based on data of environmental isotopes(~2H and ~(18)O) and the isotope of radiometric dating(~(14)C), geothermal geology, characteristics of groundwater flow field and types of goethermal reservior in Guangdong Province are taken into account in this paper, so as to analyze numerical rule and spatial distribution features of isotopes. Thus, corresponding main causes, mechanism and hydrogeological significance can be revealed to further study the potential of geothermal fluid to renew and recharge in the long run, which is conducive to enrich geothermal theories and solve existing hydrogeological problems.  相似文献   

Chemical and Spectroscopic Properties of Soil Hydrophilic Fulvic Acid Purified by Tangential Flow Ultrafiltration          下载免费PDF全文

Ian A. Navarrete  Kiyoshi Tsutsuki 《洁净——土壤、空气、水》2015,43(7):1044-1051

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Contribution of ESR/U-series dating to the chronology of late Middle Palaeolithic sites in the middle Rhône valley,southeastern France     

《Quaternary Geochronology》2015

The establishment of a chronology for late Middle Palaeolithic sites on the right bank of the Rhône valley in southeastern France is important for the knowledge of Neandertal dynamics and their demise in this area. The suite of dating methods that are directly applicable to fossils is limited for this period, especially around 50 ka where radiocarbon dating is beyond its technical limits. Currently applied to Middle and Lower Pleistocene periods, the use of combined ESR/U-series dating on Upper Pleistocene samples led to new issues, such as the acquisition of an age for samples yielding low equivalent doses and low uranium content in dental tissues. The gamma dose rate measurement thus plays a key role in age calculation. Beyond the discussion on methodological issues, the present study contributes to the establishment of a chronological framework that covers the Neandertal occupations between MIS 5 and MIS 3 for this area.  相似文献