Layered ultramafic-gabbro bodies in the Lewisian of northwest Scotland: geochemistry and petrogenesis

Layered ultramafic-gabbro bodies occur widely in the Archaean of northwest Scotland. They were metamorphosed at granulite or high amphibolite facies and were tectonically thinned and broken up during deformation. They comprise repeated ultramafic-gabbro layers, locally with Ni-poor sulphide-rich tops, each rhythmic unit showing decreasing MgO, Ni and normative anorthite with stratigraphic height. Major, trace and rare earth element data are presented for the range of rock types. In ultramafic rocks, MgO varies from 22 to 37 wt.%, Ni from 1000 to 2500 ppm and TiO₂ from 0.08 to 0.40 wt.%, while the MgO content of the gabbros ranges from 14 to 6 wt.%. The REE patterns are flat to LREE enriched with no significant Eu anomalies. In ultramafic rocks REE are from 4 to 10 times chondrite, and in the gabbros LREE range from 8 to 30 times chondrite and HREE from 6 to 15 times chondrite. Study of incompatible elements (Ti, Zr, Y) which are relatively immobile during metamorphism shows that neither garnet nor hornblende were involved in fractionation. Trace element modelling shows it is improbable that the ultramafic rocks represent primary MgO-rich liquids even though their incompatible element contents are quite high. The chemical trends are interpreted in terms of olivine and pyroxene settling from a tholeiitic high-Mg magma with 15–20 wt.% MgO derived by 30–40% partial melting of an undepleted mantle. The ultramafic rocks are the cumulates and the gabbros the derived liquids.     

North Atlantic Water in the Barents Sea Opening, 1997 to 1999

North Atlantic Water (NAW) is an important source of heat and salt to the Nordic seas and the Arctic Ocean. To measure the transport and variability of one branch of NAW entering the Arctic, a transect across the entrance to the Barents Sea was occupied 13 times between July 1997 and November 1999, and hydrography and currents were measured. There is large variability between the cruises, but the mean currents and the hydrography show that the main inflow takes place in Bjørnøyrenna, with a transport of 1.6 Sv of NAW into the Barents Sea. Combining the flow field with measurements of temperature and salinity, this results in mean heat and salt transports by NAW into the Barents Sea of 3.9×10¹³ W and 5.7×10⁷ kg s⁻¹, respectively. The NAW core increased in temperature and salinity by 0.7 °C yr⁻¹ and 0.04 yr⁻¹, respectively, over the observation period. Variations in the transports of heat and salt are, however, dominated by the flow field, which did not exhibit a significant change.     

Probing the magnetic field around protostars

We present recent JCMT polarimetric observations of the Oph A cloud core and the S106 HII region. We infer the magnetic field structure in these regions.     

Space debris and planet detection

Jane Greaves reviews the role of dusty debris in the detection and understanding of extrasolar planetary systems.     

Mitigation Lessons from the July 17, 1998 Papua New Guinea Tsunami

— The July 17, 1998 tsunami killed over 2,100 people, injured at least 800 severely enough to require hospitalization, permanently displaced over 10,000 and disrupted the social and economic framework of the coastal communities of eastern Saundaun Province, Papua New Guinea. Initial response to the disaster was delayed 16 hours because of the failure to communicate the magnitude of the impact outside the affected area. Once the scope of the disaster was known, international assistance was rapid and substantial. Medical teams, supplies, air transport and mobile field hospitals were provided to assist national medical personnel and facilities. Seven care centers were established for the displaced survivors. Nineteen countries and 17 NGOs (Non-Governmental Organizations) donated money, relief and rebuilding supplies valued at over 6 million US$ in addition to substantial contributions from national recovery funds and the Catholic Diocese. The three Malol villages, two Arop, four Sissano and the Warupu village were permanently abandoned and new villages established inland. Closure of the lagoon and restriction of coastal fishing impacted adjacent villages as well as tsunami survivors. By the second anniversary of the tsunami construction of schools, water and sanitation systems and some roads had been completed. Survivors were provided tools and building supplies to construct new homes, canoes and fishing equipment. Relief and recovery efforts were complicated by coordination difficulties among the many responding agencies and organizations, the disruption of daily routines for both survivors and villages hosting the care centers, and the intrusion of outside aid workers in a region that had been isolated before the disaster. Adaptation to the new village sites has been difficult due to their inland locations that are hotter, more insect-infested and have water and sanitation difficulties. The high number of casualties from the tsunami was the result of several factors: Population concentrated in the area of maximum tsunami impact. Date and time of occurrence. Siting of villages on vulnerable sand spits. Failure of residents to self-evacuate after feeling the earthquake. Substantial delay in mobilizing response. However, further losses were likely reduced because of the rapid deployment of air transport and medical teams, and massive international relief support. The tsunami has affected long-term tsunami mitigation in the Sissano region through the relocation of villages, heightened awareness and education programs. It has also had a significant effect on mitigation in other countries by illuminating the potential dangers of landslide-generated tsunamis and in media coverage of tsunami hazards.     

Assessing the impact of Celaque National Park on forest fragmentation in western Honduras

The effectiveness of parks as management regimes is much in debate. This study examines the effect of establishment of the Celaque National Park, Honduras, in 1987, on limiting deforestation through a comparison with the surrounding landscape using remote sensing, GIS and landscape pattern analysis. Pressure on the park region is found to relate spatially to the locations of towns and roads, with increasing deforestation in the landscape surrounding the park. In contrast, the park has been largely successful in maintaining forest cover. Although the extent of change within the park is not pronounced, the pattern of change is. Expansion of agriculture and coffee production have led to increasing pressure on the park boundaries, with as much as 25% of the landscape surrounding the park experiencing land cover change between 1996 and 2000. This has significant implications for the future of the park.     

Changes in Soybean Yields in the Midwestern United States as a Result of Future Changes in Climate, Climate Variability, and CO2 Fertilization

This modeling study addresses the potential impacts of climate change and changing climate variability due to increased atmospheric CO₂ concentration on soybean (Glycine max (L.) Merrill) yields in theMidwestern Great Lakes Region. Nine representative farm locations and six future climate scenarios were analyzed using the crop growth model SOYGRO. Under the future climate scenarios earlierplanting dates produced soybean yield increases of up to 120% above current levels in the central and northern areas of the study region. In the southern areas, comparatively small increases (0.1 to 20%) and small decreases (–0.1 to–25%) in yield are found. The decreases in yield occurred under the Hadley Center greenhouse gas run (HadCM2-GHG), representing a greater warming, and the doubled climate variability scenario – a more extreme and variableclimate. Optimum planting dates become later in the southern regions. CO₂fertilization effects (555 ppmv) are found to be significant for soybean, increasing yields around 20% under future climate scenarios.For the study region as a whole the climate changes modeled in this research would have an overall beneficial effect, with mean soybean yield increases of 40% over current levels.     

An algorithm for the computer arrangement of reactions about invariant points

A computerised algorithm is used to arrange fluid-absent reactions about invariant points in P—T space for an end-member model of blueschist facies metamorphism at Port Macquarie, N.S.W., consisting of the nine phases quartz, albite, jadeite, lawsonite, zoisite, paragonite, glaucophane, pyrope and chlorite. Inspection of the print-out (a table of reaction take-off angles for each invariant point) indicates that this multisystem consists of two mutually exclusive sets of invariant points; lawsonite-absent, paragonite-absent and glaucophane-absent versus the other six. The algorithm is completely general for any two intensive variables and can treat solid solution minerals or degeneracy in reactions/invariant points.Terms ABS(X) Absolute value of X - A(J) Slope of reaction J in degrees - V(J) Denominator variable in the slope fraction for reaction J - R(K, J) Reaction coefficient of phase K in reaction J - S(K, J) Stability pointer for phase K in reaction J, in degrees - SGN (X) Library function: =–1 when X<0; =+1 when X0 - B(Q) Correct take-off angle for the Q-absent reaction in degrees     

Late Quaternary palaeohydrology of the Konya Basin, Turkey, based on isotope studies of modern hydrology and lacustrine carbonates

The Konya plain in south central Anatolia, Turkey, which is now largely dry, was occupied around the time of the Last Glacial Maximum by a fresh-oligosaline lake covering more than 4000 km². Sediment cores from three residual water bodies (Pinarbai, Akgöl and Süleymanhaci) within the larger Pleistocene lake basin, have been analysed using a multidisciplinary approach. The sediment sequences are dated as spanning the last 50 Ka years, although breaks in sedimentation mean that there is only partial chronological overlap between them. Carbon and oxygen isotope analyses on lacustrine carbonate from the three cores give contrasting isotope profiles which reflect the different ages and independent hydrological behaviour of different sub-basins through the late Quaternary. Distinguishing changes that are regional from local effects is aided by modern isotope hydrology studies and by comparing the carbonate ¹³C and ¹⁸O values to diatom and other analyses undertaken on the same cores.