The solubility of gold and silver in the system AuAgSO2H2O at 25°C and 1 atm.

During supergene alteration of auriferous carbonate ore, the weathering fluids formed are likely to be alkaline and therefore unsuitable as a medium for gold transport as a chloride complex. Secondary gold remobilization in such deposits can often be attributed instead to gold complexing by sulphur-bearing ligands. Gold and silver solubility in the systems AuSO₂H₂O and AgSO₂H₂O respectively, from the thermodynamic data available, is due to complex formation with thiosulphate and bisulphide ligands. The most stable gold complexes, Au(S₂O₃)₂³⁻ (at φO₂ > 10⁻⁶⁰) and Au(HS)⁻₂ (atφO₂ < 10⁻⁶⁰), exist in neutral or alkaline solutions. Like gold, silver forms a stable thiosulphate complex, Ag(S₂O₃)³⁻₂ in moderately oxidizing, and bisulphide complexes, AgHS⁰ and Ag(HS)⁻₂ in reducing, alkaline media. Silver solubility in highly oxidized, neutral or acid solutions is increased by formation of AgS₂O₃⁻, Ag⁺ and AgSO₄⁻ complexes.Colloidal, crystalline and alloyed gold and silver reacted with 0.1 M Na₂S₂O₃ do not, however, demonstrate independent solubility. The rate of gold solubility in 0.1 M Na₂S₂O₃, for example, is increased both by the presence of silver-thiosulphate complexes and alloyed silver. It is possible that such behaviour is due to the formation a mixed metal complex of the type (Au, Ag)(S₂O₃)₂³⁻.The nature and mineral association of secondary gold in the oxidized zone of carbonate ore at Wau. in Papua New Guinea, is consistent with prior remobilization as a thiosulphate complex. Here the secondary gold is coarsely crystalline, alloyed with 50–75 at% Ag and enriched at the watertable and with manganese dioxide in the oxidized zone.     

Changes in the HOAr isotope composition of clays during retrograde alteration

K-Ar ages of illite alteration associated with Middle Proterozoic Athabasca unconformity-type U deposits in Saskatchewan range from 414 to 1493 Ma. The K-Ar ages correlate with water contents and δD values such that illites with young K-Ar ages have δD values as low as −169 and water contents as high as 7.7 wt.% whereas illites with older ages have δD values near −70 and water contents near 4 wt.%. Water extracted at 400°C from illites with low δD values and high water contents has low δD and δ¹⁸O values similar to those of modern meteoric water suggesting that some of the illites associated with the original deposition of the ore underwent varying degrees of retrograde alteration. The alteration is initiated by hydration of sites in the interlayer region of the illite which results in the partial resetting of the K-Ar ages and introduction of excess structural water in the form of interlamellar water. The interlamellar water is enriched in ¹⁸O by about 7 per mil relative to the water that physically surrounded the clay particle. Further alteration decreases the δD value and increases the δ¹⁸O value of the illite by isotopic exchange between the mineral and the interlamellar water. Although the chemical compositions and XRD patterns of the altered illites indicate that no detectable smectite component is present in the samples, the isotopic results suggest that the altered illites may be an early precursor in the formation of mixed-layer illite/smectite by retrograde alteration of pure illite. The wide variation of δD values of chlorite and kaolinite from these U deposits is analogous to that of the illite suggesting that retrograde alteration of clays by meteoric water can be substantial. The general association of altered clays with areas containing the highest concentrations of U is probably related to localized permeability within the ore zone.     

FeMgMn relations of ureilite olivines and pyroxenes and the genesis of ureilites

The Fe/Mn-Fe/Mg relations of published microprobe analyses of ureilite olivine cores suggest that FeO reduction in the magmatic stage was important in the genesis of some of these meteorites. Consideration of Mg/Mn and Fe/Mn partitioning between olivine and pigeonite cores shows that these two phases are not in equilibrium. The data are consistent with combined fractional crystallization and FeO reduction being the major processes of ureilite genesis. Few, if any, of the analyzed ureilites are consistent with a partial melting residue model.     

A sky survey at 102.5 MHz: Radio sources at declinations 27.5°–33.5° and 67.5°–70.5°

The results of observations on the Large Phased Array of the Lebedev Physical Institute made as part of a survey of the northern sky at 102.5 MHz are reported. Survey source lists for the declination ranges 27.5°–33.5° and 67.5°–70.5° are given, together with their coordinates, flux densities, and identifications with 4C objects. In total, there are 920 sources with flux densities S _102.5≥3.0 Jy in the two zones, which cover 0.73 star. The observing and data-reduction methods are described, and the reliability and completeness of the catalog are estimated.     

Evaluation of KAr isochron methods

The KAr isochron method is an attempt to obtain the initial age or reset age and the extraneous argon isotopic ratio of a suite of cogenetic samples of different K-contents. Some samples contain excess argon-40 and others lose argon-40. The resultant ages on single samples are not significant geologically. We have discussed the principles of three types of isochrons commonly used, the ⁴⁰Ar vs ⁴⁰K isochron, the ⁴⁰Ar/³⁶Ar vs ⁴⁰K/³⁰Ar isochron, and the ⁴⁰Ar/³⁶Ar vs ³⁹Ar/³⁶Ar isochron, and evaluated the first two types for ten different hypothetical cases. If a straight line is obtained in the ⁴⁰Ar vs ⁴⁰K isochron, a positive intercept indicates an approximately constant amount of excess argon, whereas a negative intercept indicates argon loss. A curved line or scattering of points indicates that the basic assumptions are not valid for the set of samples under consideration. The ⁴⁰Ar/³⁶Ar vs ⁴⁰K/³⁶Ar isochron method is valid, rigorously, only when all samples of the system under consideration have the same non-radiogenic argon isotope composition. This requires that either no excess argon is present in the system, or else each analysis contains the same proportion of excess and atmospheric argon. If these conditions do not hold, approximately, invalid ages and invalid intercepts are obtained. Any KAr isochron needs to be used with caution.     

中国北方地区(33°～41°N,108°～115°E)过去500年夏季降水量的周期成分分析

利用连续小波分析和经验模态分解方法,对我国北方地区(33°～41°N,108°～115°E)1470 ～2002年每年夏季降水量指数的时间序列进行了周期成分分析,探索全球气候变暖下的该地区降水量的多尺度变化特征.小波分析表明,降水量指数的可能周期有2.57a,4.83a,10.65a,23.25a,48.56a,68.30a和105.90a的周期,在95％置信水平有统计意义的周期是2.57a和23.25a的周期.这些周期和自然因素导致的周期相联系,不仅包含了气候系统内部(平流层准2a振荡和厄尔尼诺/南方涛动)的非线性作用,还包含了气候系统外(主要是太阳活动)受强迫的周期变化,且二者在原始降水量中所在比重相当,共同反映了原始降水量的绝大部分变化.降水量不只是在百年尺度上受太阳活动的驱动,在数十年尺度上也受到太阳活动的影响.我国北方地区的夏季降水量指数和夏季温度指数同相位反相关,全球增温并没有明显地改变二者之间的反相关关系.近百年来全球变暖期间,夏季降水量出现明显的新特征:短周期成分(小于30a的周期)的振幅比以往要显著大,而长周期成分的振幅比以往要显著小,同时呈现降水量逐年减少的长期变化趋势.     

Giant radio-galaxy candidates at declinations from 3.5° to 12°

A search for extended radio sources with peak flux densities higher than 10 Jy at 110.6 MHz has been carried out, and two giant radio-galaxy candidates found. Data from a 24-hour survey in an area spanning ～8° in declination were used for the search.     

Sediment thickness map of the Indian region 79°E–86°E, 2°S–8°S based on satellite gravity interpretation

Satellite free air gravity anomalies over the Indian ocean region 79°E–86°E, 2°S–8°S were obtained from the website http://topex.ucsd.edu and a contour map was compiled. Five profiles of the anomaly have been interpreted in terms of two-dimensional structures in the ocean. Thickness of sediments lying on the oceanic crust determined from the interpretation of gravity profiles were used to compile an isopach map of the region 79°E–86°E, 2°S–8°S. This map in combination with one of the isopach maps compiled by previous workers, provides information regarding the thickness of sediments up to 6° S. According to this map sediment thickness varies from ～600 m over the middle part of the region to ～800 m further south, indicating that thinning of sediments in the middle part of the region is only localized. Information provided by this gravity study may be useful in planning detailed seismological studies to delimit the outer edge of the continental margin of Sri Lanka, defined according to the United Nations Convention of the Law of the Sea (UNCLOS).     

90°—75°勘探钻孔用的金属轻便钻塔

吉尔吉兹加盟共和国部长会议所属地质保矿管理局的地质勘探队1959年10月钻进90°—75°角的斜孔时,利用了由作者设计的金属轻便钻塔。     

Kar and RbSr whole-rock ages reset during pan african event in the sinai peninsula (Ataqa Area)

A low pressure metamorphic Pan African terrain, composed mainly of schists and hornfels, ranging from high greenschist to low amphibolite facies, is exposed west of Dahab, southeastern Sinai, located between the metamorphic Kid Complex and the Feirani Volcanics.The studied metamorphic unit was dated using RbSr and KAr methods. A RbSr whole-rock isochron (based on seven samples) yields an age of 602 ± 11 Ma with an initial (⁸⁷Sr/⁸⁶Sr) ratio of 0.7041 ± 4. The RbSr age is assumed to be the age of a metamorphic phase (600 ± 10 Ma) well known in the area. On the other hand, KAr whole-rock ages (based on nine samples) show different values ranging from 590 to 526 Ma. These low KAr ages are due to the resetting of the KAr system by a thermal event, before 530 Ma affecting the Ar behaviour without disturbing the RbSr system. The Ar escape took place mainly from K-bearing feldspars, which were not affected by later textural, crystallographic or mineralogic variations.     

西南印度洋中脊48.6°~51.7°E沉积物地球化学特征

为了深入了解西南印度洋中脊调查区表层沉积物的物质来源和沉积环境,对大洋第30航次在该区域获取的21个表层沉积物样品进行了物相鉴定和主量元素、微量元素及稀土元素含量测试,分析结果显示,样品可分为Si质沉积物和Ca质沉积物两类,其中Si质沉积物富含Si、Mg、Fe、Al,稀土元素含量特征、轻重稀土元素分馏特征,以及稀土元素的北美页岩归一化曲线均表明沉积物保留了N-MORB的特征,主要为基性岩、超基性岩的风化产物;而Ca质沉积物富Ca、LOI、Sr,稀土元素以及微量元素之间的分配均指示沉积物物源为生源主导;所有站位均显示了两类沉积物不同程度的混杂,表明物质来源具有一定的多样性,调查区总体为稳定的偏氧化环境。     

Search for Dispersed Pulses at Declinations from +56° to +87°

Astronomy Reports - A survey of the northern hemisphere at the frequency 111 MHz is carried out. The total accumulation time for each point of the survey area was at least one hour. When searching...     

The RbSr age dating of some Carboniferous shales

The RbSr age dating method has been applied to a sequence of Carboniferous shales for which some geochemical information was already available. In the marine shales, the Rb/Sr ratio is higher than in the non-marine and brackish water shales. Although the range of values can be attributed to depositional processes, the range of Rb/Sr values is too small to give a depositional isochron, and thus the age of deposition can not be determined. If samples with a variable mineralogy had been selected for the isotope study, the range of Rb/Sr could have been extended. Only by chance, however, would the depositional age have been obtained.A comparison of the RbSr isotope values in the Carboniferous shales with those in probable source rocks shows that a reduction in the Sr⁸⁷/Sr⁸⁶ ratio relative to the Rb⁸⁷/Sr⁸⁶ ratio may have taken place. Such a reduction could have occurred on the Carboniferous land-mass during the formation of the clay minerals.     

西南印度洋中脊45.3°E~56°E蚀变玄武岩地球化学

<正>大洋21航次第七航段在西南印度洋中脊45.3°E~56°E洋脊段采集了20个站位的玄武岩和橄榄岩等岩石样品。本文选择了10件新鲜的和发生不同程度蚀变的玄武岩进行岩石地球化学研究,探讨热液