Rates of rock surface lowering,Princess Elizabeth land,Eastern Antarctica

A series of micro-erosion-meter sites on different rock types and in differing wind regimes was established and re-read after four years on two sites in the Larsemann and Vestfold Hills. These two oases in Eastern Antarctica are subjected to both wind abrasion and salt wedging. The measurements displayed bimodal distributions, indicating that both abrasion and single-grain detachment could be observed. Surface lowering rates of 0·015 and 0·022 mm a^?1 were demonstrated for the Larsemann and Vestfold Hills, respectively.     

Errors in measuring the percentage dry weight change of stone tablets

Portland Stone and Monks Park limestone tablets were used to assess weathering loss over a two-year study. Procedures involved in preparing tablets for exposure, attaching them to the exposure frame and reweighing might have influenced weight changes measured. The impact of each stage in the above procedures was tested to assess how much weight loss was generated and how significant the loss was comparing the two stone types and the final loss sustained upon weathering. Although all the procedures seem to produce a statistically insignificant amount of weight loss, the two stone types do respond differently to the procedures. This suggests that stone properties may be important in determining the accuracy with which tablets can be used to assess spatial patterns of weathering.     

The application of confocal microscopy to the study of stone weathering

Confocal scanning light microscopy is a valuable new method for examining the nature and progress of stone weathering at a level of resolution between optical microscopy and scanning electron microscopy. Not only is it non-destructive, but it can also create three-dimensional images.     

滇东磷矿风化型矿石的判别指标讨论及次生风化富集作用

风化型磷矿石－风化磷块岩是滇东最主要的磷矿石，为判别矿石为原生成风化磷块岩，前人已提出过１０余种作为判别标志的风化指标，但是这些指标的计算仅以矿石的化学组成为依据。笔者研究后指出，应以次生风化作用过程中磷块岩的组成和结构变化为基础，再合理使用上述某些判别指标，才能正确确定风化矿石，决定其利用价值和方法。笔者还指出，在次生风化作用中被溶蚀的不仅是碳酸盐，只要条件适当，石英和粘土矿物也可以溶蚀，使磷矿石品位增高，结构疏松，成为有利于洗选的优质矿石。     

Duricrust development and valley evolution: Process–landform links in the kalahari

Duricrusts are an important landscape component of the Kalahari region of central southern Africa. Their exposures within the dry valleys (mekgacha) of the Kalahari provide some of the most widespread surface outcrops of the terrestrial Jurassic to Holocene Kalahari Group sediments. Exposures have been extensively used in the construction of lithostrati-graphic sequences, on the assumption that valley systems have incised their courses through a pre-existing duricrust sequence. Recent work, however, has identified the role of groundwater erosion processes in valley development, which may have influenced duricrust formation. Studies of duricrusts from boreholes drilled within two mekgacha show that duricrust type is intrinsically related to the presence of a valley. Analyses of calcretes and silcretes in a series of profiles and thin sections from the Letlhakeng area of Botswana also indicate extensive alteration and diagenesis in association with former higher water tables. Sedimentary sequences within duricrust host materials can be identified but there is no evidence for correlation of duricrust cements between exposures. Profile studies from the Auob Valley in Namibia, however, suggest that this valley has incised through a sequence of duricrusts. Caution is advised in future attempts to correlate duricrust types on the basis of valley exposures, with the recommendation that where such exposures are used in a lithostratigraphic context, only duricrust host material characteristics and not cementing materials should be considered.     

湖北蛇屋山金矿区风化型金矿床地质特征及成因浅析

湖北嘉鱼蛇屋山金矿区风化型金矿床，矿体赋在于松散粘土层中，含不等量砾砂的粘土为含矿寄主岩。矿体呈似层状，产状平缓呈平卧状态。矿床规模大，长约１３００ｍ，宽约３５０ｍ，面积达０．５ｋｍ￣２，矿体厚１．２～４１．２ｍ，Ａｕ品位（１．１～７．６）×１０￣（－６）。矿石氧化程度高，金主要呈游离态次显微金形式存在。成矿控制因素主要受基岩岩性、地质构造环境和松散层性质。成矿物质主要来源于矿化原岩及下伏或附近基岩中的原生金矿体、具金矿化或金异常的含金地质体。矿床形成是表生风（红土）化作用的结果，为风化残积成因红土型金矿床。     

Sandstone weathering processes damaging prehistoric rock paintings at the Albarracin Cultural Park, NE Spain

The rock paintings in cliff-foot caves of the Albarracin Cultural Park are known as some of the most important evidences of the Levantine prehistoric art of Spain (8000–3000 BP). The paintings are on sandstone (Buntsandstein facies) of Triasic age, which may develop intense weathering. The analysis of the variables controlling the weathering indicate that salt and wetting-drying weathering are responsible for granular disintegration and flaking, which lead to rock painting deterioration.     

Cavernous weathering in the Capitol Reef Desert,Utah

Tafoni and honeycomb weathering are abundant in sandstones at Capitol Reef National Park. Cavities are particularly common in talus blocks resting on alkali-rich soil, in vertical walls of desert washes, and in sandstones containing calcareous cement. Chemical analyses, X-ray diffraction data, and field observations suggest that salt weathering is the most important cause of disintegration, but dissolution of calcite cement also occurs in calcareous sandstones. Cavernous weathering at Capitol Reef produces cavities similar in appearance to features found in arkose outcrops along the coast of northwest Washington, even though the environmental conditions at these two locations are very different.     

Neoformation of montmorillonite by post-depositional subsurface weathering in a slope deposit in central France

Observations on an Early Quaternary slope deposit in the Massif Central indicated that the texture and mineralogy of this deposit have been seriously altered by post-depositional subsurface weathering. Analyses of clay fractions and water samples show that the montmorillonite present is a stable mineral in this environment and is, and has been, newly formed. As shown by water analyses from nearby sites, the chemical environment is strongly dependent on local factors. Consequently it can be seen that great care should be taken firstly in correlating different slope deposits on the basis of texture and clay mineralogy and secondly in using these parameters as (paleo) climatic indicators.     

The decay of coastal forts in southeast Brazil and its implications for the conservation of colonial built heritage

The 500th anniversary of European arrival in Brazil was celebrated in 2000 and highlighted the need to review the condition of the countrys remaining colonial built heritage. This revision is particularly apposite in the adjacent cities of Rio de Janeiro and Niterói, where the heritage that survived twentieth century reconstruction has done so largely because of ownership by the church or military. However, whilst this may have protected buildings from demolition, detailed fabric can be neglected or abused. This paper investigates this possibility through an examination of two forts, built primarily of local augen gneiss, that guard the entrance to Guanabara Bay. Natural outcrops exposed to the same humid sub-tropical maritime environment show that this rock is susceptible to slow disaggregation through salt weathering. Surveys suggest that stonework in the forts that is sheltered from rainwash is heavily loaded with salt and has passed a threshold, wherein stresses accumulated over centuries of apparent stability, combined with the effects of a more recent increase in atmospheric pollution and apparently inappropriate intervention (re-pointing), have triggered rapid breakdown that requires immediate intervention.