Control of dust emissions by geomorphic conditions, wind environments and land use in northern China: An examination based on dust storm frequency from 1960 to 2003

The degree to which dust emissions are controlled by geomorphic conditions, wind environments and land use was investigated using the dust storm frequency (DSF) and data from more than 300 meteorological stations throughout northern China. Our analysis showed that most dust emissions originated in gobi deserts that developed in piedmont alluvial fans of the Kunlun, Qilian and Helan mountains. Dust emissions are low from other gobi desert regions, such as the northern Gurbantunggut and eastern Taklimakan, where high vegetation coverage restrained dust emissions or where dust-size particles are not abundant after a long period of strong wind erosion. Sandy deserts with relatively high vegetation coverage or an extensive cover by mobile sands are not a major dust source. Although the highest dust emissions did not appear in regions with the highest wind energy, DSF trends in each region from 1960 to 2003 were closely related to local wind activity. DSF was low in regions with high levels of human activity, where the mean DSF from 1960 to 2003 did not exceed 4 days/year; even from the 1960s to the early 1970s, the period with the greatest DSF, frequency did not exceed 8 days/year, which indicates that extensive land use did not contribute to DSF. The low DSF in these areas might result from the fact that although land use could produce abundant fine soil fractions, vegetation coverage and soil moisture remained higher than in the gobi deserts of arid China, thereby decreasing dust-storm occurrence.     

The Paleoproterozoic carbonate-hosted Pering Zn–Pb deposit, South Africa: I. Styles of brecciation and mineralization

The Pering deposit on the Ghaap Plateau, Northwestern Province, South Africa, was the largest of several Zn–Pb occurrences hosted by Neoarchean platform dolostones of the Transvaal Supergroup. With a Paleoproterozoic mineralization age, these occurrences are widely regarded as the oldest representatives of Mississippi Valley-type Pb–Zn deposits. Hosting an initial resource of 18 Mt at an average grade of 3.6 wt% Zn and 0.6 wt% Pb, the Pering deposit was mined from 1984 until its final closure at the end of November 2002. In this study, available geological and grade distribution maps were evaluated and complemented by the examination of mining-related outcrops, drill core, and a large set of ore and host rock samples. Four different styles of brecciation can be distinguished at the Pering deposit: (1) pyritic rock matrix breccia; (2) chemical wear breccia; (3) mosaic breccia; and (4) crackle breccia. Geological and mineral paragenetic observations on these different breccia types suggest that the formation of the Pering deposit commenced with an initial stage of hydrothermal karstification. Large volumes of pyritic rock matrix breccia formed by wall rock collapsing into the open space attributed to carbonate dissolution. This stage of hydrothermal karstification acted as ground preparation for the subsequent mineralization event. By the upward advance of the hydrothermal karstification process, fluid reservoirs in the previously undisturbed dolostone host rock succession were tapped, ultimately leading to fluid mixing. Hydrothermal sulphides are the most abundant where fluid mixing was most effective, i.e. along the outer and upper margins of the breccia bodies, and in stratabound zones along permeable host rock units. Chemical wear brecciation and formation of large volumes of fine-grained replacive sphalerite mineralization mark the early stage of hydrothermal Zn–Pb mineralization associated with this fluid mixing. The fine-grained stage of sulphide mineralization was succeeded by very coarse-grained open-space-infill mineralization. The latter is very uniform across the entire deposit and typically cements mosaic and crackle breccia, but also fills remaining open space within chemical wear brecciated portions of the deposit.     

新近沉积粉细砂层地基的试验与评价

通过对邯郸市某车间地基的勘察．分析和探讨了新近沉积粉细砂地层的勘察手段、其物理力学性质，及其利用载荷试验确定承载力的标准取得了较为满意的结果，提出的一些分析方法，对新近沉积的粉细砂地层的勘察具有一定的借鉴作用。     

吉尔嘎朗图凹陷宝饶洼槽下白垩统层序地层与沉积体系

运用高分辨率层序地层学原理和方法,通过对钻井和地震资料的综合分析,在二连盆地吉尔嘎朗图凹陷下白垩统中识别出1个超长期基准面旋回(二级层序)SSC1和5个长期基准面旋回(三级层序):LSC1,LSC2,LSC3,LSC4,LSC5,分析了各旋回的发育特征。识别出五种类型的沉积体系:滨浅湖近岸水下扇、较深水湖浊积扇、滨浅湖扇三角洲、滨浅湖辫状河三角洲和河流沉积体系,并在等时地层格架内分析了各基准面旋回的沉积体系构成和储层砂体的发育情况。综合分析生、诸、盖条件后认为,在垂向上,LSC3旋回为本区最有利的储集层段,在平面上,本区的油气勘探应主要寻找宝饶构造带辫状河三角洲前缘砂体,主要储层砂体类型为前缘分流水道砂和前缘席状砂。     

The chromite deposits associated with ophiolite complexes, Southeastern Desert, Egypt： Petrological and geochemical characteristics and mineralization

1 Introduction The association of massive Fe-Ni-Cu sulfides andchromite is a very unusual feature of podiformchromitites occurring in mantle tectonites of ophioliticcomplexes. It has only been described in theSoutheastern Desert, Egypt, where sulfides a…     

REE/trace element characteristics of sandstone-type uranium deposits in the Ordos Basin

1 Introduction The Ordos Basin is the second largest sedimentary basin in China. During the last 10 years, a great progress has been achieved in the aspects of tectonic evolution, dynamics process, inner and outer geological processes during Mesozoic-Cen…     

REE characteristics of the Fanshan alunite deposit in Zhejiang Province, China

1 Introduction Alunite [KAl3(SO4)2(OH)6] is a very important non-ferrous metal resource, so many countries throughout the world have made great investments in research on the mechanism of its formation, its geological characteristics and applications. O…     

基于卡尔曼滤波的时间序列影像背景估计

文章将卡尔曼滤波理论应用于时间序列影像的背景估计,引入衰减记忆因子解决滤波的发散问题,最终实现了对背景信号的估计。     

藏南地区金和锑矿床(点)类型及其时空分布特征

本文首次对藏南地区金和锑矿床(点)地质特征、成因类型和空间分布特点进行了总结，对金和锑成矿作用与中新生代构造一岩浆活动的关系进行了论证，对区域地壳演化过程中金和锑成矿动力学机制进行了讨论。该区的金和锑矿床(点)可按容矿围岩划分为：①变质岩为主要容矿围岩矿床(点)，包括金和金一锑矿床(点)；②沉积岩为主要容矿围岩矿床(点)，包括金、锑、金一锑和锑多金属矿床(点)；③火山岩为主要容矿围岩矿床(点)，以金一银矿床为代表。根据金和锑矿床(点)空间分布特点和地质特点，将本区划分为4个矿化集中区：拉昂错一马攸木一帕羊金矿化集中区(A)，然勒金和锑矿化集中区(B)，洛扎一措美锑矿化集中区(C)和邛多江金一锑矿化集中区(D)。各矿化集中区内大多数金和锑矿床(点)与燕山晚期～喜马拉雅早期富碱火成岩具密切时空分布关系，它们是古板块对接碰撞期和碰撞期后大规模构造一岩浆活动的产物。近东西向挤压性和南北向张性断裂交汇部位以及富碱火成岩发育区是寻找金和锑矿床(点)的有利场所。     

层序的测井、地震响应特征研究

在层序地层学研究中,关键是层序划分和对比。而层序划分、对比的关键是层序识别。层序的识别包括层序界面(层序的底界面、初始海泛面和最大海泛面)的识别和构成层序的体系域识别。这里,在众多前人研究成果的基础上,详细研究了层序的测井、地震响应特征,即层序界面和体系域在测井曲线上和地震剖面上的特征。其中,层序底界面在测井上表现为突变的钟型、箱型或侧积式曲线的底界;在地震剖面上表现为剥蚀、顶超、上超、下超;而体系域在测井曲线上的响应为:低水位体系域的海底扇以漏斗形中、高幅的前积式,或钟型中、低幅的后积式模式为特征,陆坡扇成钟型、正向齿形,自下而上幅度由中高幅→低幅,即具后积式测井模式,低水位楔的测井曲线表现为旋回性进积模式特征,其特征表现为锯齿状箱型。海侵体系域的测井曲线呈现向上变细、变深序列,并表现为钟型、正向齿形或齿化状,幅度由高幅变化为低幅,包络线具后积式特征。高水位体系域相应的测井曲线呈现中幅箱形或桶形,不同体系域在地震剖面上的响应特征明显不同。