滇西龙川江盆地铀矿化特征

龙川江盆地是滇西主要的铀矿赋矿盆地之一,现已探明一批砂岩型铀矿床。本文根据野外地质调查及室内系列编图,运用水成铀矿成矿理论,对龙川江盆地的基本特征及铀矿化特征进行了讨论,认为铀矿床主要分布于西部斜坡带,赋存于冲积扇沉积体系砂体中,且与潜水层间氧化带关系密切。     

新疆十红滩砂岩型铀矿床基本特征及成因分析

新疆十红滩铀矿床是中国近年发现的层间氧化带型砂岩铀矿床。该矿床位于吐鲁番—哈密盆地西南部的艾丁湖斜坡带西侧,赋矿地层为中侏罗统西山窑组辫状河—曲流河相的含煤碎屑岩系;矿体严格受发育于河道砂体中的层间氧化带前锋线控制,矿体形态呈卷状或板状;含矿岩石主要为灰—深灰色疏松和次疏松细—粗粒长石石英砂岩,铀主要以吸附形式存在;全岩Pb同位素测定的主成矿年龄为24 Ma。研究认为:晚侏罗世后,持续干热气候条件下,层间氧化带的充分发育,高含氧水在富铀地层砂体中持续向前运移,在富还原剂地球化学障形成铀沉淀富集,是该铀矿床的成因。     

土壤离子电导率测量在可地浸砂岩铀矿找矿勘查中的实验研究

土壤离子电导率测量是隐伏金属矿床、贵金属矿床普查找矿的重要技术方法,本研究应用该方法对隐伏可地浸砂岩铀矿进行普查找矿实验研究。实验表明,本区土壤离子电导率背景值为22.91μs/cm,异常平均值为513.96μs/cm,最高异常值达1349.30μs/cm。它可以圈定舌状蚀变砂岩体与未蚀变砂岩的接触边界,从而可以圈定隐伏砂岩铀矿的产出位置,是隐伏可地浸砂岩铀矿普查找矿的既经济又有效的方法。     

含水矿物在真空下的释Ar机制:Ar-Ar热年代学面临的新问题

地质体的实际情况、激光显微探针束研究、XRD和SEM观测以及真空加热下Ar的释放特征都表明体积扩散不是含水矿物在真空加热中释放Ar的唯一机制。在低温下 ,Ar的释放主要受由缺陷引起的短程扩散和体积扩散共同作用的多途径扩散机制制约 ;而在高温下 ,由于含水矿物在真空中不够稳定 ,Ar的释放受到脱羟基、脱氢、氧化反应、分层作用等造成的晶体结构改变的强烈影响。含水矿物在高温下的氧化分解会导致矿物中原始Ar浓度梯度的均一化 ,因而无法得到真实的Ar分布剖面 ,也无法据此计算矿物的封闭温度 ,并进而可能影响到ArAr年龄坪的地质意义。     

攀西地区独立银矿的成矿地质条件及找矿前景

四川攀西地区具有特定的地质条件，区域地球化学特征、有利的成矿环境和已发现的银矿床点，都证明区内具有很好的成矿地质条件，寻找大型独立银矿很有前景。主攻内生型和沉积变质型银矿床是今后工作的重点。     

Pressure effect on Ti- or P-rich accessory mineral saturation in evolved granitic melts with differing K2O/Na2O ratios

The solubility of Ti- and P-rich accessory minerals has been examined as a function of pressure and K₂O/Na₂O ratio in two series of highly evolved silicate systems. These systems correspond to (a) alkaline, varying from alkaline to peralkaline with increasing K₂O/Na₂O ratio; and (b) strongly metaluminous (essentially trondhjemitic at the lowest K₂O/Na₂O ratio) and remaining metaluminous with increasing K₂O/Na₂O ratio (to 3). The experiments were conducted at a fixed temperature of 1000 °C, with water contents varying from 5 wt.% at low pressure (0.5 GPa), increasing through 5–10 wt.% at 1.5–2.5 GPa to 10 wt.% at 3.5 GPa. Pressure was extended outside the normal crustal range, so that the results may also be applied to derivation of hydrous silicic melts from subducted oceanic crust.

For the alkaline composition series, the TiO₂ content of the melt at Ti-rich mineral saturation decreases with increasing pressure but is unchanged with increasing K content (at fixed pressure). The P₂O₅ content of the alkaline melts at apatite saturation increases with increased pressure at 3.5 GPa only, but decreases with increasing K content (and peralkalinity). For the metaluminous composition series (termed as “trondhjemite-based series” (T series)), the TiO₂ content of the melt at Ti-rich mineral saturation decreases with increasing pressure and with increasing K content (at fixed pressure). The P₂O₅ content of the T series melts at apatite saturation is unchanged with increasing pressure, but decreases with increasing K content. The contrasting results for P and Ti saturation levels, as a function of pressure in both compositions, point to contrasting behaviour of Ti and P in the structure of evolved silicate melts. Ti content at Ti-rich mineral saturation is lower in the alkaline compared with the T series at 0.5 GPa, but is similar at higher pressures, whereas P content at apatite saturation is lower in the T series at all pressures studied. The results have application to A-type granite suites that are alkaline to peralkaline, and to I-type metaluminous suites that frequently exhibit differing K₂O/Na₂O ratios from one suite to another.     

Enrichissement en uranium authigène dans les sédiments glaciaires de l'océan AustralEnrichments in authigenic uranium in glacial sediments of the Southern Ocean

Four sediment cores from the Polar frontal zone and the Antarctic zone in the Indian sector of the Southern Ocean present an increase of authigenic uranium during glacial periods. We show that this increase in uranium is due to a combination of (i) an increase in the lateral transport of organic matter, (ii) a decrease in the oxygen in deep waters, and (iii) a process of diagenesis. It appears that uranium concentration cannot be used as a proxy of palaeoproductivity in the Southern Ocean, as previously suggested by Kumar et al. in 1995. To cite this article: L. Dezileau et al., C. R. Geoscience 334 (2002) 1039–1046.     

巴音宝力格隆起带中新生代盆地砂岩型铀矿成矿地质条件及远景分析

本根据野外调查及室内系列编图成果，分析了巴音宝力格隆起带中新生代盆地砂岩型铀矿成矿地质条件，认为下白里统巴彦花组是中新生代盆地的找矿目的层位，并存在古河道与潜水层间氧化带两种砂岩型铀矿类型。巴彦毛都、准巴彦塔拉、乌里雅斯太和伊勒门盆地是形成砂岩型铀矿的远景盆地。     

甘肃北山公婆泉盆地中生代地层特征与砂岩型铀成矿条件分析

根据野外实地考察，综合前人的工作资料，从地层结构、层位、沉积体系、岩性及形成砂岩型铀矿的条件出发，概括了公婆泉盆地中生代地层的主要特征；确定了目的层并浅要分析了砂岩型铀成矿条件，对下一步铀矿找矿工作具有一定的现实意义。