Creep parameters of rocks on an engineering scale

Vertical shafts of 137 cm diameter were excavated to measure creep deformations of carbonate shale, weathered limestone and tuff. Changes of diameter at successive time intervals were recorded under constant, radial pressure. Three typical models were chosen for a regression analysis of the experimental data and their fitness were compared to one another in a statistical approach.The introduction of a steady state flow term improves the data fit considerably, and the power law was found to yield an even better result. It was also determined that rock masses in the field contain numerous discontinuities which increase the plasticity of the three types of rock tested. The viscosities determined in-situ were found to be much lower than those derived from small intact specimens by up to several orders of magnitude.     

Sources, distribution and storage of heavy metals in the Río Pilcomayo, Bolivia

The Río Pilcomayo rises on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Bolivia, and flows in a southeasterly direction for ca. 600 km to Bolivia's southern border with Argentina. Mining of the Potosí deposits has occurred continuously since 1545, generating large quantities of waste materials in the headwater of the basin. In addition, a tailings dam breach at the Porco mine in 1996 released an estimated 235 000 m³ of tailings and fluid into the upper reaches of the Río Pilaya, the largest tributary to the Pilcomayo.Concentrations of As, Sb, Cd, Cu, Pb, Hg, Ag, Tl and Zn in contemporary channel sediments upstream of the Pilaya confluence are significantly elevated above background values. Elevated levels appear to be associated with pyrite- and other sulphide mineral-bearing tailings materials transported more than 200 km downstream of the Potosí mines. Significant downstream declines in elemental concentrations occur within 15 km, and again between 150 and 200 km, from the mines. The initial decrease in concentrations is due to the rapid dilution of nearly pure tailings effluent released to the river from milling facilities near Potosí. The latter decrease results from a combination of geomorphic processes including the storage of sediment-borne metals within the channel bed and the influx of ‘clean’ sediment from several large tributaries. Downstream of the Pilaya confluence, concentrations of Cu, Pb, Hg and Zn are only slightly elevated above background values, and Ag, Cd, Sb and Tl cannot be distinguished from background levels. These data suggest that while the Porco tailings spill may have had a significant short-term impact on sediment and water quality along the lower reaches of the Río Pilcomayo, its longer-term impacts were limited. Metals stored and eroded from alluvial deposits of historical age in upstream reaches appear to be an important source of metals to the river today. An additional, and perhaps more significant source, is the release of tailings effluent to the river from modern milling operations. The transport of these contaminants downstream of Icla (203 km from Potosí) appears to be restricted by aggradational processes occurring in the vicinity of Puente Sucre. In addition, downstream of the confluence of the Río Pilaya, inputs of large amounts of ‘clean’ sediment have caused dilution of the metal contaminants. Data from other studies where similar geomorphic processes have occurred suggest that the metals in the upper Pilcomayo may eventually be moved downvalley as the aggradational processes are reversed and channel stabilisation occurs. Thus, the most significant impacts of metal contamination may not be realised in downstream areas for decades.     

赣东北元古代蛇绿岩Sm—Nd同位素年龄及地质意义

江南古陆东南缘赣东北弋阳—德兴—婺源一线有一条蛇绿岩带,普遍认为它是二个一级大地构造单元的分界线,形成于元古代。推断蛇绿混杂岩是元古代古洋壳俯冲时被挤上来的碎片;也有人认为它是中生代二大古陆之间的缝合线。Sm-Nd矿物等时线给出1034±16Ma(MSWD=1.0)的同位素年龄,它符合元古代缝合带的观点,而不利于中生代缝合带。     

Major and trace elements in igneous rocks from apollo 15

The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na₂O, K₂O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow. At least two and possible three parent magmas can be identified from the samples of the quartz normative group on the basis of their concentration ratios of Sm to Eu. Within each group, the compositions of the samples appear to be related by crystallization of olivine or pyroxene. Significant variations of the ratio of concentration of Sm to Eu cannot be produced without plagioclase-liquid equilibrium. The source material of mare basalt may be depleted in Eu. Alternatively, the magmas may have assimilated a small volume of material similar to KREEP.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

Mapping of Ozone and Water in the Atmosphere of Mars near the 1997 Aphelion

We present absolute abundances and latitudinal variations of ozone and water in the atmosphere of Mars during its late northern spring (L_s=67.3°) shortly before aphelion. Long-slit maps of the a¹Δ_g state of molecular oxygen (O₂) and HDO, an isotopic form of water, were acquired on UT January 21.6 1997 using a high-resolution infrared spectrometer (CSHELL) at the NASA Infrared Telescope Facility. O₂(a¹Δ_g) is produced by ozone photolysis, and the ensuing dayglow emission at 1.27 μm is used as a tracer for ozone. Retrieved vertical column densities for ozone above ∼20 km ranged between 1.5 and 2.8 μm-atm at mid- to low latitudes (30°S-60°N) and decreased outside that region. A significant decrease in ozone density is seen near 30°N (close to the subsolar latitude of 23.5°N). The rotational temperatures retrieved from O₂(a-X) emissions show a mean of 172±2.5 K, confirming that the sensed ozone lies in the middle atmosphere (∼24 km). The ν₁ fundamental band of HDO near 3.67 μm was used as a proxy for H₂O. The retrieved vertical column abundance of water varies from 3 precipitable microns (pr-μm) at ∼30°S to 24 pr-μm at ∼60°N. We compare these results with current photochemical models and with measurements obtained by other methods.     

东天山哈密地区赤湖钼铜矿区斜长花岗斑岩锆石SHRIMP U-Pb年龄

东天山赤湖斑岩钼铜矿床的形成时代和成矿地质背景至今尚存在争议,前人根据同一成矿带中土屋-延东斑岩铜矿的同位素地质年龄信息,认为赤湖钼矿的形成时代为中-晚泥盆世,系塔里木板块北部活动陆缘泥盆纪岛弧火山-深成作用的产物;近期一些研究者根据赤湖斑岩钼铜矿区斜长花岗斑岩锆石U-Pb和谐曲线年龄,认为矿化斜长花岗斑岩的侵位时代为晚石炭世,成矿作用与哈萨克斯坦-准噶尔板块南部活动陆缘晚石炭世汇聚阶段钙碱性岩浆侵入作用有关.在前人研究基础上,笔者对赤湖斑岩钼铜矿区矿化斜长花岗斑岩体进行了锆石SHRIMP U-Pb定年研究,获得322Ma±10Ma(95%可信度)的年龄值,表明赤湖斑岩铜矿床的形成时代为晚石炭世,成矿作用与晚石炭世钙碱性岩浆浅成侵位有关.     

海南乐东地区抱伦金矿矿石特征及其成因矿物学意义

抱伦金矿为大型中温热液石英脉型矿床,矿石以含金石英脉型为主,次为含金蚀变岩型。主要金属矿物为黄铁矿和磁黄铁矿,次要金属矿物20多种;脉石矿物有石英、方解石、绢云母和绿泥石等。金矿物主要为自然金,次为金、铋和银的固溶体,含Au8.20%～99.30%,Ag≤52.71%,Bi≤91.20%。铋、碲矿物有自然金属、硫化物、铋化物、硫盐和碲化物等类型。金矿石含Bi0.18×10-6～16×10-6,平均4.11×10-6,富矿石中达419×10-6。该矿床属较特殊的富铋类型,与琼西戈枕剪切带的金矿有相似之处,在琼西-粤东金矿带大陆一侧存在类似矿床,它们在成因上均应与岩浆和韧—脆性断裂活动有关。     

The clean development mechanism’s contribution to sustainable development: a review of the literature

The challenges of how to respond to climate change and ensure sustainable development are currently high on the political agenda among the world’s leading nations. The Clean Development Mechanism (CDM) is part of the global carbon market developing rapidly as part of the Kyoto response towards the mitigation of global warming. One of the aims of the CDM is to achieve sustainable development in developing countries, but uncertainty prevails as to whether the CDM is doing what it promises to do. Close to 200 studies on the CDM have been carried out since its birth in 1997 including peer-reviewed articles and reports from the grey literature. This review of the literature serves to assess the state of knowledge on how the CDM contributes to sustainable development (SD) including poverty alleviation. The main finding of the review is that, left to market forces, the CDM does not significantly contribute to sustainable development.     

Origin of crystalline,cold desert salts in the McMurdo region,Antarctica

The distribution of crystalline salt minerals in deposits in the McMurdo region of Antarctica has been examined to study the origin of these salts. Sulphate, chloride, sodium and calcium salts are most frequently encountered. Salts containing chloride and sodium ions become less common away from the coast. Sulphate salts are more regularly distributed but tend to be related isotopically to sea water sulphate. Salts containing magnesium ion tend to exist mainly on substrates composed of basic igneous rocks, whereas calcium and carbonate salts are present on all rock types in the region.These distributions show that salts of marine origin are regionally and quantitatively most important but that chemical weathering of mafic materials in rocks and soils is also significant. However, biological, volcanic and hydrothermal processes are or have been active contributing to salts in local areas, that include penguin rookeries and eastern Taylor Valley, the summit area of Erebus Volcano, and subsurface rocks, respectively.