Vertical seismic profiling using distributed acoustic sensing with scatter-enhanced fibre-optic cable at the Cu–Au New Afton porphyry deposit,British Columbia,Canada

Wireline logs and vertical seismic profile data were acquired in two boreholes intersecting the main mineralized zone at the Cu–Au New Afton porphyry deposit, Canada, with the objectives of imaging lithological contacts, fault zones that may have acted as conduits that channelled the mineralization, and alteration zones. Log data provide physical rock properties for the main lithologies and alteration zones. Calliper logs reveal many faults and caved-in zones generally indicating rocks with low integrity at the borehole wall. The preponderance of these zones, as indicated by the logs, suggests that their response may dominate the seismic-reflection wavefield. Outside fault zones, compressional and shear-wave velocities exhibit significant variability due to porosity, the heterogeneity of volcanic fragmental rocks and alteration. Distributed acoustic sensing was used to acquire vertical seismic profiling data in the two boreholes surveyed with wireline logs. Straight and helically wound fibre-optic cables housed standard fibres and a fibre engineered to increase the intensity of backscattering at the distributed acoustic sensing interrogator. Standard and engineered optical fibres placed in the two boreholes were daisy-chained together to form two 5-km-long continuous fibres that were interrogated at once with two interrogators. A new generation of interrogator connected to the engineered fibres provided field data with lower noise level and higher signal-to-noise ratio. These data with higher signal-to-noise ratio from straight fibre-optic cable were processed and used for depth imaging. Depth images benefitted from new migration weights that account for the directional sensitivity of the straight fibre-optic cable and limit the extent of migration artefacts. Migration results show several reflectors with shallow dips to the northwest, some explained by faults intersecting the surveyed boreholes. The main sub-vertical lithological and alteration contacts at New Afton generated downgoing reflections that were not considered in the migration.     

10th International Conference on Asian and Pacific Coasts(APAC2019),Hanoi,Vietnam, September 25–28, 2019

正Introduction The International Conference on Asian and Pacific Coasts(APAC)is an international conference to promote academic and technical exchange on coastal related studies that include coastal engineering and coastal environmental problems,among the Asian and Pacific countries/regions.APAC     

Plagioclase buoyancy in oceanic basalts: Chemical effects

Certain petrological features of oceanic volcanic and plutonic rocks are not completely consistent with previously proposed models of crystal fractionation or magma mixing. For example, Sr is often higher in the differentiated basalts of a suite of aphyric rocks than in the relatively primitive basalts even though the differentiated basalts have apparently been produced by crystallization of large amounts of plagioclase with olivine and clinopyroxene. Additionally, oceanic basalts and gabbroic rocks often contain plagioclase crystals in excess of the appropriate cotectic proportions. Certain differentiated oceanic basaltic glasses and aphyric rocks crystallize plagioclase as the liquidus mineral, which would seem inconsistent with the strongly cotectic nature of the olivine + plagioclase + liquid surface.It is proposed here that plagioclase in mid-ocean ridge magma chambers separates from the basaltic liquid that it crystallizes in at a slower rate than does co-crystallizing olivine or pyroxene. Magma mixing in which a portion of the plagioclase remains suspended in the liquid during crystallization results in much more complex liquid lines of descent in mixed magmas and appears to resolve the apparent discrepancies noted above.     

恒山中元古代早期基性岩墙群的单颗粒锆石U—Pb年龄及其克拉通构造演化意义

华北克拉通中北部变质基底发育大规模的前寒武纪基性岩墙群,由于基性岩墙同位素定年技术存在问题,因此一直未获得岩墙群的确切年龄数据。本文利用单颗粒锆石U-Pb化学法,首次获得恒山地区北西向基性岩墙群的U-Pb年龄为1769.1±2.5Ma,并证明它代表基性岩墙群的侵位年龄,这一年龄数据也是华北克拉通大规模分布的未变质基性岩墙群已知的最古老年龄。综合分析同期岩浆活动的同位素年龄记录,本文提出中元古代早期华北的岩浆侵位发生于伸展构造背景下。     

多道面波分析方法在测量土壤压实度方面的应用研究

在农业和工程领域，土壤压实度是一个重要问题。虽然采用钻孔方法可以探测土壤压实度情况，但费用较高。本文采用多道面波分析方(MASW)研究了土壤压实度的问题，并将试验结果同电阻率测井数据、岩心数据、测井速度做了对比，结果表明该方法可以用于土壤压实度的探测，而且速度快、费用低、结果准确可信。     

Method to characterize aquitards above leaky aquifers with water supply wells

Leaky aquifers provide protected drinking water since the aquifer is overlain by an aquitard, and this study develops a method to estimate hydraulic properties of the latter deposit. Steady pumping, supply well shutdowns, and slug tests generate data in adjacent monitoring well clusters that characterize the aquitard. An existing steady model estimates a site-averaged value of the aquitard permeability k if its thickness is known, and this site-averaged estimate may be compared with local k estimates from conventional and extended slug tests. A shutdown attenuation model estimates a local value of the consolidation coefficient C _V, which combines with the local k value to specify the compressibility α of the aquitard. The method is illustrated for the Fowl Meadow Aquifer, a stratified drift deposit used as a drinking water supply in eastern Massachusetts (USA), with an overlying silt aquitard of 10 m thickness. Steady data and theory suggest a site-averaged k of 2.3?×?10^–17?m² for the aquitard, while the shutdown attenuation model generates local C _V values that vary from 10^–5 to 10^–3?m²/s. The slug tests yield a local k variation (10^–17–10^–13?m²) that brackets the site-averaged value, and an α range of 10^–9–10^–7?Pa^–1.     

The use of wetland water balances to link hydrogeological processes to ecological effects

A methodology for modelling wetland water levels using the water balance approach was developed for Pulborough Brooks Site of Special Scientific Interest in West Sussex, in the UK. The methodology was applied to assess potential groundwater abstraction impacts on communities and species of ecological importance in the wetland. The modelling methodology links regional hydrogeological processes to wetland hydrology and ecology that is typically influenced by processes that take place at a more reduced spatial scale. To assess impacts, it is necessary to understand the hydrological sources of water that are affected by abstraction as well as to consider how the magnitude of these processes relates to other processes that influence wetland water levels. Water levels are commonly the most important factor determining the presence or absence of species or communities in a wetland and the model predicts wetland water levels and assesses how suitable these water levels are for species of ecological significance. Model results show that typical historic rates of abstraction have not resulted in an adverse effect on the integrity of the Pulborough Brooks relative to a ‘natural’ (no abstraction) scenario.     

北美西部陆相白垩系-古近系界线孢粉学特征简介―兼评中国东部白垩系-古近系界线研究

已经报道的北美西部陆相白垩系-古近系界线剖面已达近百处,这些剖面分布在阿拉斯加南部向南经加拿大直到美国南部的新墨西哥州北部的广大北美西部内陆地区,其中很多属迄今所知全球很好的陆相白垩系-古近系界线剖面.这些剖面常有标志性的界线黏土,并伴有其他地球化学、生物地层学特征.因为这些剖面所在地当时都在湿润或半干旱地区内,有利于生物化石,特别是孢粉化石的保存,易于开展孢粉学研究.经过近四十年不懈努力,孢粉学已经成为北美精确确定陆相白垩系-古近系界线最重要的、也是迄今为止所知最为有效的古生物学工具.孢粉植物群在界线上下特征差别显著,容易区分.界线之下含有大量主要繁盛于白垩纪的被子植物花粉,而在临近界线时则突然消失或仅零星出现,界线附近则以一层孢子异常丰富层为古近系底部特征.进入古近纪之后,虽然被子植物花粉有所恢复,但是繁盛于白垩纪的成分却很少出现.北美和新西兰、日本白要系-古近系界线附近在沉积岩和孢粉学方面的相似性表明这一事件可能是全球性事件.简要回顾和讨论了我国与孢粉学相关的几个热点地区陆相白垩系-古近系界线的研究概况,我国东北及江苏北部和北美西部大部分地区白垩系-古近系界线附近的孢粉植物群及其沉积环境比较类似,在苏北到东北地区范围内首次发现陆相白垩系-古近系界线地层的可能性比其他地区大.