The correlation of Mesozoic gold ore districts at the Sino-Korean and Aldan-Stanovoi shields

The geological structure and gold ore potential of the activized Aldan-Stanovoi and Sino-Korean shields of East Asia are compared. These two regions show similar tendencies in their geological evolution during the Archean, Proterozoic, and Phanerozoic epochs but differ in types of tectonic structure and associations of ore deposits. According to recent studies by Russian and Chinese geologists, the Mesozoic complexes of these shields possess higher gold ore potential than was suggested before. As a result of these studies, the amount of conditions favoring the formation of large gold districts and deposits in the activized shields has strongly increased. Some of these deposits are polychronic and polygenetic (the Bam deposit), others are associated with J-K alkaline magmatism (the Central Aldan district), a third group of deposits are related to granites of the same age (the East Shandong district), and a fourth group includes stratiform deposits in the lower part of the udokan series (Ugui district). The various Mesozoic hydrothermal ore deposits of the northern framework of the Sino-Korean Shield are especially interesting. The study of problems of gold metallogeny was initiated in Russian geological science by Yu.A. Bilibin (1935–1940) in the central part of the Aldan Shield. Some new data concerning the gold ore potential of the Sino-Korean Shield extend our knowledge of gold ore districts in East Asia and make clear the necessity of more careful and systematic study of the gold ore potential of the Aldan-Stanovoi Shield.     

Isotopic signatures of deposition and transformation of Lower Cambrian saliferous rocks in the Irkutsk amphitheater: Communication 1. Sulfur isotopic composition

New isotope data on Lower Cambrian rocks of the Irkutsk amphitheater are reported in three communications. The first communication is devoted to the sulfur isotopic composition, which is most sensitive to ostsedimentary geochemical transformations of sulfate rocks in saliferous formations. It is shown that δ³⁴S values in Bel’sk and Zhigalovo boreholes are within 22–35‰ The lowest values are close to the sulfur isotopic composition of a halogenic basin, while the highest values are related to epigenetic sulfate reduction. This process was responsible for the elimination of 100 m of anhydrites from the Lower Cambrian section.     

Synchrotron IR study of hydrous ringwoodite (γ-Mg2SiO4) up to 30 GPa

High-pressure synchrotron infrared (IR) absorption spectra were collected between 650 and 4,000 cm⁻¹ at ambient temperature for hydrous Mg-ringwoodite (γ-Mg₂SiO₄) up to 30 GPa. The main feature in the OH⁻ stretching region is an extremely broad band centred at 3,150 cm⁻¹. The hydrogen bond is strong for most protons and the most probable site for protonation is the tetrahedral edge. With increasing pressure, this band shifts downward while decreasing its integrated intensity until disappearance at a pressure of 25 GPa. Only one band at 2,450 cm⁻¹ and an absorption plateau persist with a maximum wavenumber of 3,800 cm⁻¹. This behaviour is reversible upon pressure release. We interpret this as a second-order phase transition occurring in hydrated Mg-ringwoodite at high pressure (beyond ∼ 25 GPa). This result is compatible with the observation by Kleppe et al. (Phys Chem Miner 29:473–476, 2002a) who suggested the presence of Si–O–Si linkages and/or partial increase in the coordination of Si. Beyond the phase transition, the protons are delocalized and their environment on the ringwoodite structure is probably quite different from that at low pressure. Data obtained in situ at high pressures and temperatures are needed to better understand the effect of protonation on the structure and to better constrain this phase transition.     

Estimation of ship velocities from MODIS and OCM

Detection of ships and their tracks in the atmosphere from satellites was earlier demonstrated by Porch, Noone, and Kaufman, among others. In this letter, we have gone one step further to estimate the ship speed and direction by locating them and their tracks from multisatellite imagery. Exhausts from the ships create streaks of clouds in the atmosphere that help identify the same ship from two satellites. Ship velocities are estimated from displacements of ships. We have used optical sensors data from Moderate Resolution Imaging Spectroradiometer (MODIS) and Ocean Color Monitor (OCM) to demonstrate this technique. Estimated velocities of ships are within the expected range. Application of this approach has general interest to the navy, coast guards, shipping corporations, commercial ship owners, and fishermen. More satellite observations can be used to continuously monitor the ship velocities.     

Geocomputation, Geodemographics and Resource Allocation for Local Policing

The field of geodemographics is one of the most fertile applications areas of geocomputation research. Geodemographic profiles of the characteristics of individuals and small areas are pivotal to tactical and strategic resource management in many areas of business, and are becoming similarly central to efficient and effective deployment of resources by public services. In this context, this paper describes research that has been developed in partnership with the Devon and Cornwall Constabulary and Institute of Criminal Justice Studies (ICJS) at the University of Portsmouth to assess the potential use of geodemographics as a policing tool. Crime, the fear of crime and the efficacy of public services are issues that have moved to the top of the UK political agenda and have long been matters of serious public concern. This paper considers the ways in which police forces might use geodemographics to better deploy resources at a variety of spatial scales in England and Wales.     

The thermodynamic influence of subgrid orography in a global climate model

Assessments of the impacts of climate change typically require information at scales of 10 km or less. Such a resolution in global climate simulations is unlikely for at least two decades. We have developed an alternative to explicit resolution that provides a framework for meeting the needs of climate change impact assessment much sooner. We have applied to a global climate model a physically based subgrid-scale treatment of the influence of orography on temperature, clouds, precipitation, and land surface hydrology. The treatment represents subgrid variations in surface elevation in terms of fractional area distributions of discrete elevation classes. For each class it calculates the height rise/descent of air parcels traveling through the grid cell, and applies the influence of the rise/descent to the temperature and humidity profiles of the elevation class. Cloud, radiative, and surface processes are calculated separately for each elevation class using the same physical parametrizations used by the model without the subgrid orography parametrization. The simulated climate fields for each elevation class can then be distributed in post-processing according to the spatial distribution of surface elevation within each grid cell. Parallel 10-year simulations with and without the subgrid treatment have been performed. The simulated temperature, precipitation and snow water are mapped to 2.5-minute (~5 km) resolution and compared with gridded analyses of station measurements. The simulation with the subgrid scheme produces a much more realistic distribution of snow water and significantly more realistic distributions of temperature and precipitation than the simulation without the subgrid scheme. Moreover, the 250-km grid cell means of most other fields are virtually unchanged by the subgrid scheme. This suggests that the tuning of the climate model without the subgrid scheme is also applicable to the model with the scheme.