核分析新技术:Alpha反冲径迹热年代学

矿物中U、Th及其子核进行α衰变释放出α粒子时,剩余重核受到反冲而产生辐射损伤.在适当条件下经化学蚀刻,这些辐射损伤成为在光学显微镜下可观测的核径迹.通过建立适当的蚀刻模型和定年模型,计算径迹面密度和体密度,并测量U、Th含量,便可得到年龄.Alph反冲径迹年代学的特点是可以确定较年轻的时代(百万年至数百年),故在资源环境、地理、考古等领域具有广泛的应用前景.     

核分析新技术:Alpha反冲径迹热年代学

矿物中U、Th及其子核进行α衰变释放出α粒子时，剩余重核受到反冲而产生辐射损伤。在适当条件下经化学蚀刻，这些辐射损伤成为在光学显微镜下可观测的核径迹。通过建立适当的蚀刻模型和定年模型，计算径迹面密度和体密度，并测量U、Th含量，便可得到年龄。Alpha反冲径迹年代学的特点是可以确定较年轻的时代（百万年至数百年），故在资源环境、地理、考古等领域具有广泛的应用前号。     

金云母中Alpha反冲径迹的蚀刻和退火行为

矿物中U、Th及其子核进行α衰变释放出α粒子时，剩余重核受到反冲而产生辐射损伤。在适当的条件下经化学蚀刻，这些辐射损伤成为在相干涉反差显微镜下可观测的核径迹。实验证明，蚀刻过程中，Alpha反冲径迹（ARTs）增长数和蚀刻时间成线性关系，随蚀刻时间增加，线性被破坏，最终达到一个“坪”。退火过程表明，Alpha反冲径迹的退火要比裂变径迹的退火容易，其退火率随退火时间的增长和温度的升高而增加，且温度对其影响显著，在350℃下加热样品20h，退火率达到90%左右，在400℃下加热4h，完成全退火。     

α反冲径迹定年

与裂变迹径定年类似，α反冲径迹定年（Alpha-Recoil Track）也是基于天然放射性元素所释放核粒子在固体中产生可蚀刻径迹的积累。铀钍及它们的子体核素进行α衰变时形成α反冲径迹，当发射一个α粒子时，重的剩余核反冲并造成30-40nm的辐射损失痕迹，经过蚀刻α反冲径迹可在干涉相差显微镜下观测。如果在样品形成以后全部迹径被保留下来，那么测定它们的总数就可以得到样品的年龄。Α反冲径迹定年是一种刚刚开始研究的新型热年代学核分析技术，研究样品可以是单个小云母片（约0.5mm），定年范围102-106a，该方法对第四纪地质、地理、灾害及考古等领域有很大的应用潜力。     

α径迹蚀刻方法及其在砂岩型铀矿中的应用——以HJQ砂岩型铀矿为例

α径迹蚀刻法是用感光胶片的片基记录放射性元素衰变产生的α粒子所造成的辐射损伤,经化学蚀刻扩大径迹的方法,多应用于铀矿研究,可简便有效地寻找岩石和矿石中颗粒细小的铀矿物并研究铀的分布状况、存在形式等,具有简单易行,灵明度高等优点。以HJQ地区砂岩型铀矿为例,利用α径迹蚀刻法对矿石中铀的分布形式研究,得出铀以分散吸附状态、铀矿物2种形式存在,为研究本地区铀成矿作用具有重要的理论与现实意义。     

关于径迹蚀刻测量的应用条件

我国将核径迹技术应用于铀矿找矿是从1974年开始的,到1976年已全面推广应用。十年来,径迹蚀刻测量的应用效果是好的,对突破红石泉矿床东段,401矿床西带和罗坑矿床的扩大以及303地区301号矿体的落实起了重要的作用。经典射气法、径迹蚀刻测量以及普通物探方法对3075矿床的发现和扩大都起了重要的作用。除此之外,径迹蚀刻测量用于寻找地下水源,用于预报地震和用于岩矿等地质研究,都取得了不少成绩。关于在铀矿找矿中径迹蚀刻测量在不同条件下的应用问题,我们将从地质、地球化学条     

α径迹蚀刻方法在砂岩型铀矿研究中的应用——以通辽地区砂岩铀矿为例

α径迹蚀刻法应用于铀矿研究,可简便有效地研究岩石、矿石中铀的分布状况、存在形式等,寻找岩石和矿石中颗粒细小的铀矿物,研究与铀矿化相关的蚀变作用等。以通辽地区砂岩型铀矿为例,利用α径迹蚀刻法对矿石中铀的分布形式,铀的富集规律进行研究,根据矿石的α径迹特点得出铀以分散吸附状态和铀矿物两种形式存在,后者通常与碳酸盐化、黄铁矿化相伴随。     

海南岛玻璃陨石(雷公墨)裂变径迹年龄的测定

引言许多绝缘固体如塑料、玻璃和天然矿物常常可以记录带电粒子的径迹(这些未经化学蚀刻的径迹可称为潜迹),这是带电粒子在绝缘固体内沿着自己运动的轨迹所造成的辐射损伤区。在天然矿物中所记录的裂变径迹是这类固体核径迹中的一种,它是直径大约50(?),长约20微米的柱形辐射损伤区,最初只能用高倍的电子显微镜才能观察到。     

两花岗岩体接触带铀系核素迁移的初步模拟

随着世界各国大力发展核电，放射性废料的安全处置已成为当今研究热点和前沿学科。高放废物深地质处置的安全性主要取决于处置库内放射性核素向生物圈的迁移程度。在侵入岩中，放射性核素主要是通过地下水沿岩石孔隙从处置库向生物圈迁移的。为了理解放射性核素在花岗岩体接触带的迁移行为，本文根据两花岗岩体接触带中样品的铀系核素放射性活度比值（^234U/^238U,^230Th/^234U,^226Ra/^230Th,^230Th/^238U)，利用 α-反冲（弹射）作用引起的放射性不平衡理论，计算了铀系核素子体^234U,^230Th,^226Ra在后期地下水的作用下在花岗岩体接触带及其裂隙内的迁出率、迁入率、并进行了质量平衡的计算。结果表明，经α-反冲作用进入流体的核素的迁出率要远大于因核素自然衰变的消亡率；裂隙充填物及裂隙能阻滞大量核素的迁移，其沉淀核素来自接触带花岗岩；花岗岩能强烈阻滞核素的迁移，可作为阻止放射性核素从核废料地下处置库向外迁移的有利天然屏障。     

石英裂变径迹蚀刻条件的对比实验研究

通过 40%的 HF溶液、KOH饱和溶液和 19 mol/L的 NaOH溶液这三种常用方法对大、小颗粒石英进行裂变径迹蚀刻实验的对比发现,用环氧树脂固定的小颗粒石英样品,不宜用 KOH饱和溶液(150 ℃)和 19 mol/L的 NaOH溶液(沸点,约 120 ℃)作为裂变径迹的蚀刻剂,宜用 40%的 HF溶液;三种方法均适宜于大颗粒石英,但不同的蚀刻方法蚀刻效率不同, 40%的 HF溶液(29 ℃)的蚀刻效率最高,且操作简单、安全性高.40%的 HF溶液最佳蚀刻时间为: 温度在 4 ℃左右(冬季)时为 40 min,温度在 29 ℃左右(夏季)时为 30 min,可在全年室内常温条件下操作.     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861