Geochemical Characteristics of Gold Polymetallic Deposits as Exemplified by the Laozuoshan Deposit,Heilong jiang,China

From the studies of ore deposit geologic settings,sulfur isotopes,lead isotopes,carbon isotopes and oxygen isotopes,fluid inclusions and petrochemistry in this paper,the authors have drawn a conclusion that the ore-forming hydrothermal solutions are the high-temperature magmatic hydrothermal solutions for the gold ore deposit,and at the same time,the involvemety of crustal materials can not be ruled out .It is the first time that the authors have proposed that the Laozuoshan gold-ploymetallic ore deposit in Heilongjiang Province was formed in the calc-alkaline series environment at the margin of an active continent.     

Distribution characteristics of Geo-hazards in Ganxi Valley after the Wenchuan earthquake

A devastating earthquake of Ms 8.0 struck the Wenchuan area on May 12, 2008. The quake triggered numerous landslides and avalanches in Ganxi Valley. Aerial photo interpretation indicates that the landslides and avalanches, presently in a stable state, are concentrated in 91 subregions of the valley, occupying 10.42 km², about 29% of the valley area. Some laws have been found on the gradient, aspect, elevation, distance of rupture, and formation lithology of geo-hazards in Ganxi Valley: (1) They are mainly situated on slopes between 30° and 50° and increase in number with increasing slope; (2) Failures are mainly in a southerly direction; and most occurred between 1,000 and 1,600 m, especially between 1,000 and 1,400 m; (3) Most are within 2,000 m of the Beichuan fault or within 1,000 m of other major faults; (4) most failures occurred from the T₁f + t formation in the study area. The geo-hazards status quo of Ganxi Valley provides foundation for the scheme of hazard reducing in the future.     

Natural and anthropogenic aquatic environmental changes reconstructed by paleolimnological analyses in Lake Kitaura,central Japan

In order to assess the recent anthropogenic environmental changes in Lake Kitaura, central Japan, changes during the past few centuries were reconstructed from results of radiometric and tephrochlonological age determination, magnetic susceptibility measurements, total organic carbon analyses, total nitrogen analyses and fossil diatom analyses on a sediment core from the lake. A total of six major and sub-zones are recognized according to the diatom fossil assemblages, and we discuss aquatic environmental change in Lake Kitaura mainly based on these diatom assemblage change. Zone Ia and Zone Ib (older than AD 1707) are marine to brackish. In Zone IIa (AD␣1707–AD 1836), most of the brackish diatoms disappeared, and were replaced by freshwater species indicating a decrease in salinity. We interpret the salinity decrease in Zone I–IIa as a sea-level fall during the Little Ice Age. The salinity of the lake decreased to near freshwater conditions in Zone IIb (AD 1836–AD 1970), which could arise from alteration in River Tone or development of a sandspit in the mouth of River Tone in addition to sea-level change. In Zone IIIa (AD 1970–AD 1987), the diatom assemblage indicates a freshwater environment, and sedimentation rates increase rapidly. These changes reflect sedimentary environment change and an ecosystem transition due to the construction of the tide gate. In Zone IIIb (AD 1987–AD 2002), the diatom flux (valves cm⁻² y⁻¹) increased and species composition changed. The changes in Zone IIIb show a good agreement with limnological monitoring data gathered from the lake. These paleolimnological data suggest that the recent human-induced changes of the aquatic environment of the lake after the 1970s exceed rates during the period concerned in this study.     

Assessing groundwater storage changes in the Nubian aquifer using GRACE data

Gravity Recovery and Climate Experiment (GRACE) level two (L2) data is used in estimating the groundwater storage changes (GWSC) in the Nubian Sandstone Aquifer System (NSAS). This set of data consists of spherical harmonics coefficients with specific degree and order. The GRACE data is de-correlated using a sixth degree polynomial in order to reduce the effect of the noise error resulting from the correlation between the spherical harmonics coefficients with the same degree parity. The GRACE estimates of GWSC are smoothed using Gaussian filter with half width of 1000 km. This half width is chosen in order to maximize the correlation between the GRACE estimates of GWSC and previous modeling results of the NSAS. The loss in groundwater storage occurring in each of the four countries sharing the NSAS is calculated to assess the sustainability of using the NSAS as a water resource in each country. The overarching finding in this study is that NSAS is losing its groundwater storage at a very high rate. Also, it is found that Egypt is the fastest in losing its groundwater storage from the NSAS. This loss of groundwater storage in Egypt may not necessarily be resulting from in-country extractions because of the trans-boundary nature of this aquifer. The GRACE-based estimates are found to be close to available data and previous modeling results of the NSAS.     

Linking multi-temporal analysis and community consultation to evaluate the response to the impact of Hurricane Stan in coffee areas of Chiapas,Mexico

This paper analyses the responses related to land use of coffee growers in Chiapas, Mexico to the impact of Hurricane Stan (October 2005). A multi-temporal analysis of the effect on land cover was performed through the combination of unsupervised classification of SPOT multispectral images and visual interpretation of panchromatic images (8 months previous to the hurricane, and 2, 14, and 40 months after the hurricane). The information provided by this geographic analysis was interpreted in light of information gathered though household surveys. Although the hurricane wrecked havoc across the region, the main impact in the study area was in the riparian zones where the extent of the loss experienced in terms of coffee harvest and soil was such that, even 14 months after the event, households with land in those areas were struggling to recover. Nevertheless, after 40 months, the zones that had suffered total soil loss began to support soil and vegetation, indicating the possibility of replanting coffee in those areas. Although the hurricane occurred when the coffee sector was particularly fragile as a result of the preceding several years of poor prices, the impact did not trigger extensive land use change. The surveys showed, however, that people are now more informed of the risk of living and farming on the river margins and are now performing soil conservation practices and planting trees to reduce risk.     

Pressure-temperature and evolution of fluid compositions of Al2SiO5-bearing rocks,Mica Creek,B.C., in light of fluid inclusion data and mineral equilibria

Metamorphosed pelitic rocks from Mica Creek, British Columbia contain sillimanite, kyanite with minor fibrolite and andalusite-bearing quartz pods. Mineral equilibria were used to infer peak P-T conditions and fluid compositions in equilibrium with the solid phases. Fluid inclusions in three schist samples appear to be good indicators of conditions affecting those rocks during and after peak metamorphic conditions. In samples from two localities, fluid inclusions from schist and quartz-rich segregations have densities appropriate to the peak metamorphic conditions. The observed compositions for these fluids (low salinity with 12 mole % dissolved CO₂) agree with calculated values of 0.84 to 0.85, based upon paragonite-quartz-albite-Al₂SiO₅ equilibria. The fluids unmixed as the schists were uplifted and cooled; fluid inclusions trapped during this stage outline a solvus in the CO₂-H₂O-NaCl system. A later influx of fluids containing CH₄ and N₂ accompanied formation of andalusite-bearing plagioclaserich segregations. The restricted association of andalusite-bearing pods and low density fluids suggest a localized but pervasive fluid influx during uplift. Preservation of high density fluid inclusions during uplift and erosion, coupled with evidence for unmixing of H₂O- and CO₂-rich fluids on the solvus, provide constraints on the P-T uplift path.     

Polarization in spectral lines

The general formalism, presented in a previous paper of this series (Landi Degl'Innocenti, 1983a), is particularized to deduce the radiative transfer equations for polarized radiation and the statistical equilibrium equations for a multi-level atom in the zero-magnetic field, collisionless regime. The formulae are developed both in the standard representation and in the representation of the statistical tensors. For resonance scattering in a two-level atom, in the limiting case of complete depolarization of the ground level, we recover the classical results for Rayleigh scattering and we derive the expression of the phase matrix in terms of ordinary rotation matrices. The law of scattering is then generalized to take properly into account the influence of the anisotropy of the radiation field on the atomic polarization of the ground level (depopulation pumping).     

Seismic model of the lithosphere of the East European Platform beneath the Baltic Sea-Black Sea profile

This paper presents the results of seismic measurements along the Baltic Sea-Black Sea profile. The basic wave groups recorded up to distances of 900 km are characterized. The main elements of a lithospheric model of the southwestern part of the Precambrian East European Platform are given. The thickness of the Earth's crust is about 45 km and the mean velocity of the crust is about 6.3 km/s. At a depth of 65 km, the velocity increases from 8.2 to 8.5 km/s. In the depth interval 110 to 135 km, there is a series of layers with low and high velocities. The lower boundary of the lithosphere is probably defined by the boundary at a depth of 110 km.     

The geochemistry of uranium occurrences and speciation in groundwater of Chinnar sub basin,South India

An attempt has been made in Chinnar sub basin of Dharmapuri district, South India to isolate the geochemistry of uranium occurrences in groundwater. The geology of the area is mainly of charnockite and granite gneiss. Groundwater samples were collected for two different seasons post and pre monsoon in two different litho units (granite gneiss and charnockite) and analysed for major, minor and uranium concentrations. Higher uranium (18.45 μg L^?1) has been recorded during pre monsoon season in granite gneiss with increasing pH. The saturation index calculation for the groundwater isolated minerals like uaraninite, coffinite, haiweeite and soddyite to be precipitating and uranium oxides like UO_2.25, UO_2.25beta, UO_2.33beta as oversaturated. The Eh-pH diagram attempted represents solubility of uraninite within the pH range of 6.0 to 8.0. The study isolate uranium in groundwater of the study area is controlled by the presence of (U₄O₉) uranium oxide.