白垩纪温度较冷的估价

白垩纪温度较冷的估价Ｂ．ｗ．Ｓｅｌｌｗｏｏｄ等有关白垩纪气候的概念部分基于详尽的地质证据，如不耐寒冷的古生物（如：珊瑚的分布比现在偏极地５－１５℃）和特殊气候条件的沉积相的广泛分布。这些资料的解释反映２１℃的等温线在纬度上至少向两极移动５°，全球的平...     

Origin of the hydrocarbon component of carbonaceous chondrites: the star-meteorite connection

We report the results of an experiment that produced a residue which closely matches the hydrocarbon component of the Murchison carbonaceous chondrite. This experiment suggests that the parent material of the meteoritic component originated as polycyclic aromatic hydrocarbon species in carbon stars during their later stages of evolution. The experiments also indicate that the pathway from those formation sites to eventual incorporation into the meteorite parent body involved hydrogenation in a plasma in the solar nebula or in H II regions prior to the solar nebula. This model is consistent with what is known about the meteoritic hydrocarbon component including deuterium abundance, the observation of cosmic infrared emission bands best attributed to polycyclic aromatic hydrocarbon molecules, and the inherent stability of these molecules that allows their formation in stars and subsequent survival in the interstellar medium.     

强雷暴环境的中尺度模拟

1.引言本文评述了当前有限区域中尺度模式提供中纬度强雷暴环境的准确预报以及风暴对环境可能的反馈作用的能力.这里的"中尺度模式"指的是用水平格距Δx=10～100公里作为在静力学原始方程中的有限差分近似.对平流波来说,要有满意的截断误差至少需4—6个格点(Pielke,1981),而要准确地计算非线性波的相互作用,则需近10个格点(Gerrity,1972).因此,这些模式适合模拟的天气现象尺度为Orlanski(1975)定义的中β尺度(25—250公里)上部到中α尺度     

Selenium contamination in the Colorado River Basin, western USA： Remediation by leaching and nanof＇dtration membranes

Selenium （Se） is an essential micronutrient to biota, but can become a potent toxicant at elevated concentrations. The natural sources and chemical properties of Se species make the boundary between deficiency and toxicity narrow for some biota, with both phenomena common around the globe. Large areas of farmland in the Colorado River Basin （CRB） generate salinized drainage water with Se concentrations much higher than 5 μg/L, the U.S. Environmental Protection Agency chronic water-quality criterion for the protection of aquatic life. We have carried out detailed field and laboratory studies to investigate Se geochemistry and remediation in two of these areas： the Middle Green River Basin, Utah and the Salton Sea Basin, California, located respectively in the Upper and Lower CRB. Results from these and other studies show that approximately 90% of the dissolved Se in the Colorado River and its tributaries originally is derived from the Upper Cretaceous Mancos Shale and equivalent pyritic marine units that outcrop in the Upper CRB. Selenium is mobilized commonly by biogeochemical oxidation of this pyritic shale and is concentrated mainly as selenate （SeO4^2-） in soils and agricultural drainage water of dry climates by evaporation. Minor （0%-5%） amounts of Se are present as the selenite species （HSeO3^-） and （SEO3^2-）, but these species and the more reduced species, elemental Se （SeO） and selenide （Se^2-）, have much lower solubility and/or have high sorptive affinity towards organic matter, clay minerals and iron oxyhydroxides. The concentration of dissolved Se （-2.5 μg/L） and salinity in the Lower Colorado River water are among the highest of the world major rivers. Because of low precipitation （7 cm/a） and extreme evapotranspiration （-1.8 m/a） rates in the Salton Sea Basin, California, Se values in irrigation water imported from the Colorado River increase to 〉300 μg/L in drainage wastewater. Removal of Se from contaminated wastewater by nanofiltration membranes was demonstrated in laboratory and pilot-scale field experiments.     

Attenuation of aqueous metal transport at two natural acid rock drainage occurrences in the Yukon Territory, Canada

Naturally acidic drainage associated with pyritic black shale has been observed in many locations in the Yukon Territory. While not necessarily linked to known mineral deposits, most of these natural acid rock drainage occurrences show elevated dissolved concentrations of trace elements, especially zinc, nickel, copper, cadmium and arsenic. Based on field observations, microbial investigation, chemical analyses and geochemical modeling, the fate and transport of potentially deleterious elements at two natural acid drainage occurrences with slightly different settings are examined. The Macintosh Creek is a small, acidic stream （pH 2.98-3.40）, 2 km long, located in the Macmillan Pass area of east-central Yukon amidst known sedimentary exhalative massive sulfide mineralization but remains undisturbed by exploration activities. Its trace metal content is apparently derived from groundwater discharges, which gave as much as 5.0, 2.5, 0.7, 0.13 and 0.03 mg/L ofZn, Ni, Cu and As, respectively. Interaction and sorption reactions with algal mats, biofilms and iron oxyhydroxides appear to be the dominant mechanisms attenuating aqueous contaminant transport along the stream. Cryogenic precipitation further consolidates the ferricrete formation and reduces the mobility of the sorbed metals. The tributaries of the Engineering Creek along the Dempster Highway in northern Yukon drain through a series of dolomite, phyllite, argillite, limestone, black shale, sandstone and conglomerate with no known concentration of mineralization. In this area, the water chemistry fully reflects the local geology with acidic streams invariably associated with black shale occurrences. Groundwater seeps in the headwaters area of the km-180 Creek completely enclosed in black shale gave pH 3.0 and as much as 148, 39, 2.9 and 9.1 mg/L of Zn, Ni, Cu and As, respectively. Sorption with iron oxyhydroxide and organic matter appear to dominate the attenuation of contaminant transport along the stream. However, once entered into carbonate-dominated terrains, secondary carbonate minerals exercise additional geochemical control on the local water chemistry as a result of neutralization.     

湖南印支期过铝质花岗岩的形成: 岩浆底侵与地壳加厚热效应的数值模拟

在合理构建华南印支期地质-物理模型的基础上, 利用FLAC软件, 模拟了该区印支期过铝质富钾花岗岩形成与基性岩浆底侵, 及陆壳变形叠置加厚两种动力学背景的可能联系. 模拟结果表明, 220 Ma±的基性岩浆底侵能导致地壳含水矿物相岩石的深熔, 但除非印支期存在大规模基性岩浆的底侵作用, 否则其热效应持续时间和热效应波及范围难以形成具大岩基规模的湖南印支期花岗岩. 在陆壳叠置加厚模型中, 地壳的叠置加厚可导致中下地壳界面温度升高到700℃以上, 引起片麻质岩石熔融, 当加厚因子达1.3, 白云母矿物脱水熔融产生的熔体达到熔体流动临界比例(≥20%), 从而形成花岗岩基; 结合印支期挤压逆冲推覆构造和同期基性火山岩极少出露的地质事实, 认为陆壳变形加厚可能是湖南印支期构造岩浆作用形成的主导因素.     

岩石破裂实验研究中强震发生前主破裂形成时能量释放过程的分析

分析用方程Q（t)=Q(t1) A1-A2(tf-t)^m[1 ccos(2πlog(tf-t)/p-φ)]来模拟强震前地震能量释放过程的一些条件，式中的Q（t)是在时间t以前所累积的“贝尼奥夫”总应变，tf是主震的时间，A1，A2，c,m,p,ψ都是模型的参数，Q（t1)是已知量（t1≤tf时）。表明在一定假定条件下幂指数m=α（2-d) 1。这里d是主震周围地震潜在震源群震中的尺寸，参数α决定着幂律。根据这个规律，地震时释放的地震能量和总能量的比值随地震的震级而变化。模型可用于分析实验研究岩石破裂释放声能的动力学，也适用于对堪察加一些强震前地震活动性的回溯性分析。     

EXPERIMENTAL AND FIELD STUDY ON MINING-PIT MIGRATION

1 INTRODUCTION Because of the large quantity of sand and gravel in their beds, rivers have always been considered as a major source of sand and gravel for civil works. Acceptable quality, ease of extraction and economy are some of the reasons could be mentioned. Unfortunately, specific laws and regulations regarding the safe in-stream mining have not been provided for users and officials. What should be taken into account are the effects of over-mining of sand and gravel, which can cause …     

Reconstruction of the diagenesis of the fluvial-lacustrine- deltaic sandstones and its influence on the reservoir quality evolution-- Evidence from Jurassic and Triassic sandstones, Yanchang Oil Field, Ordos Basin

The reservoir quality of Jurassic and Triassic fluvial and lacustrine-deltaic sandstones of the Yanchang Oil Field in the Ordos Basin is strongly influenced by the burial history and facies-related diagenetic events. The fluvial sandstones have a higher average porosity (14.8%) and a higher permeability (12.7×10?3 ?m2) than those of the deltaic sandstones (9.8% and 5.8 ×10?3 ?m2, respectively). The burial compaction, which resulted in 15% and 20% porosity loss for Jurassic and Triassic sandstones, respectively, is the main factor causing the loss of porosity both for the Jurassic and Triassic sandstones. Among the cements, carbonate is the main one that reduced the reservoir quality of the sandstones. The organic acidic fluid derived from organic matter in the source rocks, the inorganic fluid from rock-water reaction during the late diagenesis, and meteoric waters during the epidiagenesis resulted in the formation of dissolution porosity, which is the main reason for the enhancement of reservoir-quality.