Speculations on the causes of crustal rifting and subduction,with applications to the atlantic margin of Brazil

It is suggested that ideal regions for continental separation involve regions of crust dominated by granulite and amphibolite facies rocks. Such rocks are strong and refractory. The formation of thick crust of this type requires, at some stage, that the crust be tectonically thickened to about twice the equilibrium thickness which is itself controlled by melting. It is suggested that subduction is initiated by the basalt-eclogite transition in the upper oceanic lithosphere. A large sediment load may induce this reation and lead to subsidence or subduction. If the rate of sediment supply is small, subduction will be transient, or may not occur at all and sinking slow. Such motions could account for sporadic igneous activity by partial melting of slowly sinking ocean-floor materials.     

Changes in winter cyclone frequencies and strengths simulated in enhanced greenhouse warming experiments: results from the models participating in the IPCC diagnostic exercise

The effect of enhanced greenhouse warming on the behaviour of mid-latitude cyclones is examined for changes in the total number of cyclone events and for changes in the number of intense events using the daily averaged mean sea level pressure simulated by coupled climate models participating in the IPCC AR4 (Fourth Assessment Report) diagnostic exercise. Results are presented for a set of scenarios which were produced using a wide range of increasing levels of greenhouse gases. For the enhanced greenhouse warming experiments, the models simulated a reduction in the total number of events and an increase in the number of intense events. This is a robust result, which essentially all the models exhibit. Comparison of the results for each of the scenarios shows that the magnitude of the changes in the number of simulated events increases with increasing levels greenhouse gas forcing used in the scenarios. Even though the numbers of events change, there is no apparent change seen in the geographical distribution of the events, i.e. there is no obvious change in the positions of the storm tracks seen on hemispheric charts. This was also evident in the results for the filtered variance of the meridional wind which was used as a proxy for cyclone activity. In spite of this, it is possible that small shifts in the storm tracks, which are difficult to resolve with the relatively coarse grid used for analysis, could occur.     

The generation of batholiths

The formation of the melts which produce intrusions of the granite family are considered to result from the partial fusion of high-grade metamorphic rocks. The melting behaviour of such materials is considered. Such melts will rarely be water-saturated and the degree of water-saturation must set limits on the ability of the melt to rise. The natural residue of fractional fusion will be metamorphic rocks of the granulite facies. The motion of the melts seems reasonable in relation to the theory of Taylor instability and Stokesian rise of the materials. Differences between Archaean batholith patterns and those in modern belts of plate subduction will be considered. It is suggested that such differences could result from fusion processes in the upper mantle occurring at higher levels than at the present time and “ocean ridges” being more closely spaced.     

Advances in,and applications of,X-ray photoelectron spectroscopy (ESCA) in mineralogy and geochemistry

The important uses of X-ray photoelectron spectroscopy (XPS or ESCA) in mineralogy and geochemistry are described. Crystal chemical, oxidation state and chemical bonding information can be obtained from the chemical shifts of the observed peaks. The high surface sensitivity of ESCA enables detection of 0.01 of a monolayer for many ions on mineral surfaces. ESCA is extremely useful for monitoring adsorption, desorption, dissolution and exchange reactions on mineral surfaces. Future improvements in intensity and resolution will greatly enhance the crystal chemical applications of ESCA.     

Nuclear waste isolation: an urgent international responsibility

The isolation of nuclear wastes for at least thousands of years is an urgent world problem. It is an international problem, for in many nations with such wastes their geology is not suitable for long-term isolation.

A lead geo-question involves which are the best host rocks, with guaranteed long-term low permeability and the best ion-exchange, redox systems for the capture, retention, of the most dangerous nuclides. In general mud rocks on land or the sea floor must be considered.     

地球科学新的优先考虑的问题：自然科学、工程学、经济学的联合和知识发展的必要性

文章从分析生命支持系统的基本组成着手,指出愈来愈多的人类活动促使大气中ＣＯ２、ＣＨ４、Ｈ２Ｏ、Ｎ２Ｏ…含量不断增加,气候变暖;水资源危机愈加严重;对土壤产出的要求越来越高;地质灾害对人类自身的冲击更加严重;能源和原材料更大程度的短缺;废物的排放量增大及生物变异等新问题和生物种类的新发现。对上述现象的深入研究或解决,均是地球科学优先和急于考虑的问题。而这需要大批高素质,既具自然科学、工程学、经济学,又具管理知识的人才,因而这些优先考虑问题的重中之重是教育。     

Relationships between String Bag Craft Distributions,Language and Geographical Distance in the Upper Sepik and Border Mountains of Papua New Guinea

This paper describes analyses involving patterned string bags collected in the upper Sepik in Papua New Guinea. The Mantel test and correspondence analysis were used to explore whether variability in craft repertoires exhibits any covariance with the region's complex linguistic picture, and if so, whether this relationship is more significant than any spatial autocorrelation the data may exhibit. Bag construction techniques exhibited strong spatial autocorrelation, while for colour patterns the effect was weaker. An effect for language remained for both dependents after statistical control, but colour pattern characteristics had a slightly stronger association with language overall. The weaker spatial autocorrelation for colour pattern variability is argued to be due to higher rates of dissemination facilitated by the visibility of the patterns and their compatibility with a broad range of construction techniques. The effect for language, on the other hand, is argued to have resulted from of a higher rate of inter-settlement migration along a particular stretch of the Sepik where people speak the same language.     

Trace element chemistry of major rivers in Orissa State, India

 Geochemical analyses of surface waters from rivers flowing through Orissa State, India, indicated that trace element concentrations were extremely variable and consistently higher than world river average. The Brahmani River was the most solute-rich river studied, followed by the Baitarani and Mahanadi Rivers. Although all three rivers drain similar geology, the Brahmani River catchment is heavily industrialized, and water samples collected upstream and downstream from industries indicated that anthropogenic activity directly influenced its chemical composition. Samples collected from several towns, in all three river systems, did not invariably show similar patterns, with various elements having higher dissolved concentrations upstream. Because the concentration of total solids increased downstream, this implied that some components of the sewage had effectively sequestered available elements from solution and converted them to particulate material. Although the impact of pollution is clearly recognizable in water samples collected in proximity to the anthropogenic source, there are only slight elemental accumulations in the lower reaches of the Mahanadi River, with no accumulation in the Brahmani River. Apparently for these large rivers, discharged effluent becomes rapidly diluted, while complexation and sedimentation further removes trace elements from the water column. However, in the less voluminous Baitarani River, elementar enrichment near the river's mouth suggests that in this secondary river, where dilution effects are less, the concerns over regional water quality may be more prevalent. Received: 1 April 1995 · Accepted: 30 August 1995