青海尕斯库勒盐湖沉积物孢粉组合特征与铀分布关系初探

以青海省柴达木盆地西部尕斯库勒盐湖干盐滩ZK06钻孔岩芯为研究对象,结合孢粉、年代学和铀含量数据,探讨了盐湖沉积物中铀分布与古气候变化的关系.研究表明,自280 ka以来,尕斯库勒盐湖经历6次成盐期和6次淡化期;植被演化趋势为疏林草原—灌丛草原—荒漠草原;气候由凉略湿逐渐变为冷干.盐湖沉积物中铀含量与孢粉总浓度、灌木浓度、蒿属浓度呈明显正相关;与草本植物浓度呈正相关.孢粉带内沉积物的铀含量比成盐期高得多,平均铀含量为成盐期的3倍.孢粉组合特征可能为研究铀及其他元素在盐湖沉积物中的影响因素提供一些古植物和古气候条件证据.     

渤海湾沿岸平原沉积物中铀、钍地球化学研究

本文利用U、Th元素化学性质上的某些差异研究它们在渤海湾沿岸沉积物中的含量、分布以及沉积过程的地球化学特点。在渤海湾沿岸沉积物中U元素含量为2.41ppm,Th为13.0ppm。研究表明,沉积物中U与砂的含量成负相关而与粘粒含量成正相关,并且U、Th元素含量与一些金属元素的丰度变化具有相关性。     

柴达木盆地西部尕斯库勒盐湖280ka以来沉积特征

以柴达木盆地西部尕斯库勒盐湖干盐滩6个钻孔岩芯为研究对象,从岩性特征、成盐期、沉积类型、沉积结构、沉积幅度等方面探讨尕斯库勒盐湖沉积特征。研究表明,自280 ka以来尕斯库勒盐湖经历相对湿润—干旱的气候波动和气候演化,在距今43.6 ka左右进入最干旱时期,可能属于柴达木盆地第二次成盐期;沉积结构层分异现象不明显;各成盐期平均沉积速率变化不大,平均沉积速率比新疆和内蒙古地区高;该湖沉积中心在盐湖的西北部。     

柴达木盆地西部尕斯库勒盐湖280 ka以来沉积特征

以柴达木盆地西部尕斯库勒盐湖干盐滩6个钻孔岩芯为研究对象,从岩性特征、成盐期、沉积类型、沉积结构、沉积幅度等方面探讨尕斯库勒盐湖沉积特征。研究表明,自280 ka以来尕斯库勒盐湖经历相对湿润-干旱的气候波动和气候演化,在距今43.6 ka左右进入最干旱时期,可能属于柴达木盆地第二次成盐期;沉积结构层分异现象不明显;各成盐期平均沉积速率变化不大,平均沉积速率比新疆和内蒙古地区高; 该湖沉积中心在盐湖的西北部。     

腾冲地区火山岩铀钍地球化学特征及其成因的初步探讨

腾冲火山岩位于云南省西部，主要分布于腾冲、梁河两县境内。处于印度板块和欧亚板块之间的缝合地带，是次一级的板块——腾冲断块。在广泛分布的中新生代花岗岩之上，堆积着大量新生代喷发的火山岩。     

越南在地球化学研究中用仪器中子活化分析测定铀和钍含量

自１９８５年以来，仪器中子活化分析方法以及重建的５００ＫＷ大叻核研究反应堆一直用于地质和环境样品的分析。该法具有灵敏度高、精度可靠、效率高的特点，所以满足了越南国内地质调查的需要。本文概述了越南在地球化学研究中应用仪器中子活化分析测定铀和钍含量所取得的主要结果。     

青海北祁连中南沟水系沉积物地球化学特征

青海北祁连中南沟高山切割明显,坡下植被发育,属高寒草甸景观,不利于颗粒物质的机械迁移。该地区不同粒级水系沉积物中成矿元素变化趋势一致,含量衰减迅速且在细粒级富集,并主要为硫化物相。研究结果说明,在该地区常规水系碎屑沉积物测量方法存在一定问题。由于草甸发育,颗粒物质迁移受到抑止,水系碎屑沉积物仅出现在2~3级水系。因此,在普查阶段可能会漏掉许多矿化信息;由于受其分布所限,详查阶段无法保证采集到真正的水系沉积物,只能用坡积物代替,导致采样介质不统一。     

柴达木盆地西部尕斯库勒油田原油地球化学特征及成因

尕斯库勒油田是柴达木盆地最大的油田,对于该大型油藏的形成机理一直是研究的重要课题。对尕斯库勒油田E31和N1-N2油藏原油的地球化学特征进行综合研究,结果表明:原油的正构烷烃呈偶奇优势,具有低的P r/Ph比值,含β-胡萝卜烷,反映它们形成于强还原环境;含丰富的伽玛蜡烷和>C30藿烷,指示它们形成于咸水-超咸水环境,但是,N1-N21原油的成油环境古盐度略高于E31原油;具有高含量的C27甾烷、规则甾烷、4-甲基甾烷、长链三环萜烷和低含量的二环倍半萜、烷基环已烷,说明它们母质主要为菌藻类,但是,两个油藏原油母质略有不同,E31原油较多的来自细菌,N1-N21油藏原油则较多的来自浮游生物;原油具有低的C29甾烷20S/20S 20R和ββ/ββ αα比值及T s/Tm比值和低丰度的重排甾烷,反映了它们都为未成熟-低成熟度原油,但是,E31油藏原油的成熟度略高于N1-N21油藏原油。油源研究表明E31和N1-N21油藏原油由第三系盐湖相生油岩中生物脂类与可溶有机质和干酪根一起在低成熟阶段所生成。     

森林沼泽景观区水系沉积物中腐殖作用的地球化学特征

水系沉积物是森林沼泽区的主要表生介质之一,对其中的有机碳、胡敏酸、富里酸和胡敏素分布状况以及富里酸相和胡敏酸相Cu、Pb、Zn、Ag、Sb 、Mn、Mo、Ni、As、Hg的分布特征进行了研究.发现有机质主要由胡敏素组成,其含量可占有机质的2/3左右,地球化学活性很强的富里酸和胡敏酸占腐殖质总量1/3左右.影响半数多元素在水系沉积物中地球化学活动性的主要腐殖酸是富里酸,而影响Hg、Ag、Pb、Sb的是胡敏酸.     

The Identification and Geological Significance of Fault Buried in the Gasikule Salt Lake in China based on the Multi-source Remote Sensing Data

The salinity of the salt lake is an important factor to evaluate whether it contains some mineral resources or not, the fault buried in the salt lake could control the abundance of the salinity. Therefore, it is of great geological importance to identify the fault buried in the salt lake. Taking the Gasikule Salt Lake in China for example, the paper established a new method to identify the fault buried in the salt lake based on the multi-source remote sensing data including Landsat TM, SPOT-5 and ASTER data. It includes the acquisition and selection of the multi-source remote sensing data, data preprocessing, lake waterfront extraction, spectrum extraction of brine with different salinity, salinity index construction, salinity separation, analysis of the abnormal salinity and identification of the fault buried in salt lake, temperature inversion of brine and the fault verification. As a result, the study identified an important fault buried in the east of the Gasikule Salt Lake that controls the highest salinity abnormal. Because the level of the salinity is positively correlated to the mineral abundance, the result provides the important reference to identify the water body rich in mineral resources in the salt lake.     

察尔汗盐湖正构烷烃和单体碳同位素分布特征及其古植被意义

对察尔汗盐湖ISL1A钻孔沉积物样品进行了有机分子地球化学分析, 检测出了丰富的类脂物, 包括正构烷烃、一元正脂肪酸、一元正脂肪醇等, 本文主要讨论正构烷烃类脂物的分布特征。正构烷烃的分布型式表明其来源于低等菌藻类生物和陆生高等植物, 正构烷烃的高碳数部分均有显著的奇偶优势, 高碳数正构烷烃全部以C31 为主峰碳。正构烷烃分布特征表明在110.1~50.1 ka B.P.期间, 察尔汗盐湖地区为草原植被景观。对C27、C29、C31 长链正构烷烃进行了单体碳同位素测定, 利用二元模式估算了C3 和 C4 植物的相对输入贡献, 结果表明, 以C3 植物为主。     

A chronology for the long pollen record from Lake Wangoom,western Victoria (Australia) as derived from uranium/thorium disequilibrium dating

The chronology of a long pollen record from Lake Wangoom, one of the few long palaeoenvironmental records from southeastern Australia, is discussed in light of the acquisition of new uranium/thorium disequilibrium (UTD) dates. Of crucial importance has been the estimation of ages for two major pre‐Holocene phases of forest expansion recorded in the sequence, with implications for the timing of periods of high effective precipitation in the region. The new UTD ages indicate that the oldest forest phase falls within the Penultimate Interglacial whereas the later phase corresponds with the Last Interglacial. This is older than indicated by previously reported UTD and radiocarbon dates, but confirms a chronology based on direct correlation with the pollen record from marine core E55‐6. The new chronology of the Lake Wangoom sequence provides evidence that phases of sustained forest development in southeast Australia relate to interglacial periods. In comparison, interstadial periods appear to be characterised by only minor arboreal development. Marked differences in the pattern of vegetation development evident in each of the interglacials are thought to reflect varying climatic and anthropogenic influences. Copyright © 2002 John Wiley & Sons, Ltd.     

Geochemical Characteristics of the Sandstone—type Uranium Deposits in Northern Sichuan Province

Described in detail in this paper are the geochemical characteristics of the sandstone-type uranium deposits in northern Sichuan Province .Favorable and unfavor-able conditions for the enrichment of uranium are explored on the basis of the elemental abundances and ratios of U,Th and K determined by gamma-ray spectroscopy. Gamma-ray spectroscopic(U, Th and K) and XRF analyses(As, Ba) are helpful to distinguish U-bearing light-colored sandstones from U-barren light-colored ones and red sandstones (red claystone) from light-colored sandstones. Therefore, the favorable target area for prospecting the sandstone-type uranium deposits can be difined in northern Sichuan Province.     

中国花岗岩型铀矿区域地球化学指示元素特征及异常模式

我国铀矿床主要划分为四大类型,包括花岗岩型铀矿床、火山岩型铀矿床、砂岩型铀矿床和碳硅泥岩型铀矿床。花岗岩型铀矿约占我国已探明铀矿总资源储量的三分之一以上,是我国重要的铀矿化类型。地球化学勘探方法对花岗岩型铀矿床勘查具有良好的效果。根据全国铀矿资源潜力评价项目研究成果,在大量研究中国花岗岩型铀矿化水系沉积物地球化学异常特征基础上,总结了一套对花岗岩型铀矿化勘查稳定的、行之有效的指示元素及其组合,确定了花岗岩型铀矿化地球化学异常模式,并以实例说明典型花岗岩型铀矿化异常模式。水柰沉积物地球化学异常是进行铀矿产预测评价的有效手段,对铀矿资源的潜力评价发挥了重要作用。     

Hydrochemistry of the Gasikule Salt Lake,Western Qaidam Basin of China

正The Qaidam Basin is a large intermontane depression in Qinghai Province,China,which located on the northern margin of the Tibet plateau,and surrounded by the Qilian,Kunlun and Aljun mountains which rise to more than 5000m.Some 27 salt lakes occur within the basin,occupying an area of approximately 1500 km2.Additionally,there are extensive areas of dry playas.Together,the playas and salt lakes cover about one quarter of the total basin area.Whereas the western     

Uranium/thorium dating of ferricretes from mid- to late pleistocene glacial sediments,western Tasmania,Australia

The uranium/thorium (U/Th) dating method was applied to pedogenic/diagenic ferricretes developed within glacial drifts from the northern West Coast Ranges of Tasmania. The dates derived from the method are, by definition, minima for the sediments, with the ferricretes being secondary mineral deposits which appear in the form of bands, horizons or nodules comprised of indurated masses of iron oxy(hydr)oxides developed post-depositionally within the host sediment or soil. The absence of such deposits in well-identified drift sediments of the last glaciation suggests the development of ferricrete horizons in glacial drifts occurred during earlier interstadials and interglacials. This has been confirmed by the uranium/thorium dating of ferricrete bands within glacigenic sediments obtained from three drill cores from the Boco Valley. The ages derived were found to be consistent with estimates for the timing of glaciation derived from palaeomagnetic analyses, radiocarbon dating and relative dating techniques. The results show that the uranium/thorium method can be used to successfully date ferricretes obtained from within glacial sediments of ages <350000 yr and provides valuable information regarding the minimum age of the host sediment. © 1997 John Wiley & Sons, Ltd.     

贵州省白马洞铀矿床地球化学特征及成因

白马洞铀矿床是一个铀、汞、钼多金属热液矿床,处于黔中侏罗山式褶皱带,近EW向白马洞深断裂上盘。区内热液活动明显,围岩蚀变强烈,铀、汞、钼矿体赋存在中寒武统高台组页岩上、下层间角砾岩带中。本文简要介绍地质背景、成矿特征,重点论述了地球化学特征及成因,为今后在省内深入研究碳硅泥岩型铀矿成矿规律和指导深部找矿起帮助作用。     

Distribution of uranium and thorium in Irtysh River and the upriver wastewater from a rare metal mine impact on it

Uranium and Th are important radioactive elements. Most studies were focused on their environmental impact from uranium deposits and mining sites. But other sorts of mines such as rare metals mines are associated highly with uranium and thorium, too. In China, the Irtysh River is the only river that runs into the Arctic Ocean. The famous Koktokay rare metal pegmatite deposit is located in the headwater region of this river and has been exploited for several decades. The waste ore piled along the riverside as long as several kilometers. The wastewater flom the concentrating plant is discharged into the river directly. In addition, uranium and thorium can be leached from the waste ore into the river in the weathering process. So it is necessary to study the uranium and thorium distribution in the branch and trunk streams of the Irtysh River and the wastewater from the mining site impact on it. In this study, the contents of uranium and thorium in water samples from the Irtysh River and rare metal mine wastewater have been detected directly with ICP-MS. Uranium and thorium distribution and geochemical behaviors in the Irtysh River basin have been studied. The environmental uranium and thorium pollution status in the Irtysh River and wastewater from a rare metal mine impact on it have also been evaluated. The study shows that uranium and thorium contents in wastewater from a rare metal mine are as high as 78.311 μg/L and 0.627 μg/L, respectively, so we should also pay attention to the radioactive pollution from the rare metal mine. The average contents of U and Th in the branch streams of the Irtysh River are 0.572 μg/L and 0.015 μg/L, respectively. At the mean time, in the trunk of the Irtysh River, average thorium content is 0.019 μg/L while U is up to 2.234 μg/L, much higher than the average content （0.0309 μg/L） of the world rivers. From upstream to downstream in the trunk of the Irtysh River, thorium content declines gradually due to dilution by other branches and deposition itself.