Seawater nutrient and carbonate ion concentrations recorded as P/Ca, Ba/Ca, and U/Ca in the deep-sea coral Desmophyllum dianthus

As paleoceanographic archives, deep sea coral skeletons offer the potential for high temporal resolution and precise absolute dating, but have not been fully investigated for geochemical reconstructions of past ocean conditions. Here we assess the utility of skeletal P/Ca, Ba/Ca and U/Ca in the deep sea coral D. dianthus as proxies of dissolved phosphate (remineralized at shallow depths), dissolved barium (trace element with silicate-type distribution) and carbonate ion concentrations, respectively. Measurements of these proxies in globally distributed D. dianthus specimens show clear dependence on corresponding seawater properties. Linear regression fits of mean coral Element/Ca ratios against seawater properties yield the equations: P/Ca_coral (μmol/mol) = (0.6 ± 0.1) P/Ca_sw(μmol/mol) - (23 ± 18), R² = 0.6, n = 16 and Ba/Ca_coral(μmol/mol) = (1.4 ± 0.3) Ba/Ca_sw(μmol/mol) + (0 ± 2), R² = 0.6, n = 17; no significant relationship is observed between the residuals of each regression and seawater temperature, salinity, pressure, pH or carbonate ion concentrations, suggesting that these variables were not significant secondary dependencies of these proxies. Four D. dianthus specimens growing at locations with Ω_arag ? 0.6 displayed markedly depleted P/Ca compared to the regression based on the remaining samples, a behavior attributed to an undersaturation effect. These corals were excluded from the calibration. Coral U/Ca correlates with seawater carbonate ion: U/Ca_coral(μmol/mol) = (−0.016 ± 0.003) (μmol/kg) + (3.2 ± 0.3), R² = 0.6, n = 17. The residuals of the U/Ca calibration are not significantly related to temperature, salinity, or pressure. Scatter about the linear calibration lines is attributed to imperfect spatial-temporal matches between the selected globally distributed specimens and available water column chemical data, and potentially to unresolved additional effects. The uncertainties of these initial proxy calibration regressions predict that dissolved phosphate could be reconstructed to ±0.4 μmol/kg (for 1.3-1.9 μmol/kg phosphate), and dissolved Ba to ±19 nmol/kg (for 41-82 nmol/kg Ba_sw). Carbonate ion concentration derived from U/Ca has an uncertainty of ±31μmol/kg (for ). The effect of microskeletal variability on P/Ca, Ba/Ca, and U/Ca was also assessed, with emphasis on centers of calcification, Fe-Mn phases, and external contaminants. Overall, the results show strong potential for reconstructing aspects of water mass mixing and biogeochemical processes in intermediate and deep waters using fossil deep-sea corals.     

Diamond economics of the Prairie Creek lamproite, Murfreesboro, AR, USA

The Prairie Creek lamproite is the largest of seven ultramafic vents that make up the Prairie Creek lamproite province. Diamonds were first discovered in 1906, and commercial mining continued intermittently until about 1931. The evaluation program undertaken by the Arkansas State Parks Commission in the 1990s resulted in the mapping and evaluation of four major vent facies rock types: olivine lamproite, epiclastic sediments, phlogopite-rich tuff and olivine-rich tuff. Significant diamond contents were found only within the phlogopite-rich tuff (0.11 carat/100 tonnes) and olivine-rich tuff (1.1 carats/100 tonnes).Stratigraphic relationships indicate that the diamondiferous tuffs have undergone <50 m of erosion. Extrapolation of the surface rock units and their diamond contents to the pre-erosion surface suggests that 93,000 carats of diamonds were liberated and then concentrated as a natural surface enrichment. Early commercial production focused on the natural surface concentrations, an assumption supported by historic mining records. Historical grades suggest that 58,000 carats were contained in these surface deposits, about half of those diamonds being recovered during commercial operation. These relationships suggest that 35,000 carats remain as eluvial and alluvial deposits adjacent to the existing tourist area. This erosion model minimizes the prospects for either primary or alluvial commercial mining; however, it does validate early historic mining records and suggests areas for further tourist development within existing park boundaries.     

An evaluation of the health status of the Lavaca Bay, Texas ecosystem using Crassostrea virginica as the sentinel species

Locational risks for compromised ecosystem health for the eastern oysters (Crassostrea virginica) harvested from Lavaca Bay, Texas were estimated. Flow cytometric evaluation of variations in DNA content and the lysosomal destabilization assay were used for evaluation of genotoxicity and stress, respectively. Bayesian geo-statistical methods were utilized to estimate and evaluate spatial effects. For models with spatial risks, continuous surface maps of predicted parameter values were created to evaluate risk location. Lysosomal destabilization assay results were spatially oriented whereas flow cytometry results were fit best with the random effects model. While not spatially oriented, the highest levels of variations in DNA content were also present near industrial facilities. Locational risks of increased biomarkers of genotoxicity and stress in the eastern oyster (Crassostrea virginica) were increased with proximity to industrial facilities     

Cadmium distribution in coastal sediments and mollusks of the US

Cadmium (Cd) concentrations in the coastal United States were assessed using the National Status and Trends (NS&T) Mussel Watch dataset, which is based on the analysis of sediments and bivalves collected from 280 sites since 1986. Using the 1997 sediment data, Pearson correlation (r = 0.44, p < 0.0001) suggested that Cd distributions in sediment can, be to some extent, explained by the proximity of sites to population centers. The 2003 tissue data indicated that “high” Cd concentrations (greater than 5.6 μg/g dry weights [dw] for mussel and 5.4 μg/g dw for oysters) were related to salinity along the East and Gulf coasts. Along the West coast, however, these “high” sites appeared to be related to upwelling phenomenon. Additionally, sedimentary diagenesis was found to be the most likely explanation of why sediment and mollusk Cd content were not well correlated.     

Investment and regional development in Post-Mao China

This paper investigates China's changing investment systems, investment patterns and their impact on regional development. It reveals that the reforms have brought profound changes to Mao's investment system and investment allocation. Investment decentralization has given localities considerable autonomy and incentives in economic development. Budgetary investment has declined dramatically while enterprise funds, bank loans and foreign investment have increased significantly in China. An increasing amount of these new sources of fixed investment have been channeled to more profitable non-state sectors. In terms of regional changes, China's coastal provinces, particularly Guangdong, Jiangsu, and Zhejiang have recorded more rapid investment growth and have much higher per capita investment than many interior provinces. In addition, investment in the coastal provinces relies less on the state and is more profitable than that in the poorer interior. The sectoral and regional unevenness of fixed investment has significantly contributed to the uneven regional development in China. This research also has important theoretical implications, as it shows that regional investment is neither a cumulative causation process nor a convergent process, but influenced greatly by government policy, local states and local conditions, and foreign capital. An analysis of these factors should improve the understanding of investment allocation and regional development, especially for the transition economy in which the control and capacity of the central state has declined, while local and global forces have emerged as equally important forces shaping spatial change.     

Determination of the REE in Geological Reference Materials DTS-1 (Dunite) and PCC-1 (Peridotite) by Ultrasonic and Microconcentric Desolvating Nebulisation ICP-MS

Inductively coupled plasma-mass spectrometry is well suited for the precise, accurate and rapid determination of rare earth elements in most geological samples. However, determination of rare earth elements in certain mantle-derived materials, without applying preconcentration techniques, remains problematical due to low natural concentrations (generally < 1 ng g⁻¹). Consequently, USGS reference materials DTS-1 (a dunite) and PCC-1 (a partially serpentinized harzburgite) have only suggested rather than recommended values for the rare earth elements in reference material compilations. We compared results obtained using two ICP-MS instruments: a U-5000AT ultrasonic nebuliser coupled to a PQ2+ quadrupole ICP-MS and an ELEMENT sector field ICP-MS equipped with a MCN-6000 microconcentric desolvating nebuliser, with the suggested literature values for these two reference materials. Precision and accuracy of analytical methods employed by both instruments were demonstrated by excellent relative standard deviations (< 2%) and inter-laboratory agreement (< 5%) for numerous analyses of BHVO-1 and BIR-1, which are well established with rare earth elements contents at the μg g⁻¹ level. Repeat analyses of DTS-1 and PCC-1 at each laboratory indicate that each method is generally precise to better than 5% at sub-g g⁻¹ levels. Furthermore, values from both instruments generally agree to within 10%. Our DTS-1 and PCC-1 values agree reasonably well with selected data reported in the literature (except for Ce and Sm in DTS-1) but exhibit poorer agreement with reported compilation values. With the demonstrated level of precision and accuracy, we contend that these new values for DTS-1 and PCC-1, generated by two different instruments, are the best estimates of the true whole-rock composition of these samples reported to date.     

双核结构模式形成的自然基础

The dual-nuclei spatial structurs is composed of a regional central city,a port city and their spatial relations in certain regions.In general,this spatial structure could be found in most of the coastal regions or regions along big rivers.In terms of the mechanism,the dual-nuclei structure is the result of the spatial interaction and the complementary characteristics of the center city and the port city.The “marginal function” of the port city and its relationship with the central city has long been discussed in the literature.On the one hand,drainage area is the main natural grographical background of the formation of the dual-nuclei spatial structure;therefore,we can build a theoretical geographic structure that is based on the drainage area.On the other hand,vicissitude of the coastline also has important influence on the formation of the dual-nuclei spatial structure.It is especially meaningful if we can notice this when we examine deeply the research on the spatial structure of delta.     

Biot dispersion for P‐ and S‐wave velocities in partially and fully saturated sandstones

Ultrasonic compressional‐ and shear‐wave velocities have been measured on 34 samples of sandstones from hydrocarbon reservoirs. The sandstones are all of low clay content, high porosity, and cover a wide range of permeabilities. They were measured dry and brine‐saturated under hydrostatic effective stresses of 10, 20 and 40 MPa. For eight of the sandstones, ultrasonic velocity measurements were made at different partial water saturations in the range from dry to fully saturated. The Gassmann–Biot theory is found to account for most of the changes in velocities at high effective stress levels when the dry sandstones are fully saturated with brine, provided the lower velocities resulting when the dry sandstone initially adsorbs small amounts of moisture are used to determine the elastic properties of the ‘dry’ sandstone. At lower effective stress levels, local flow phenomena due to the presence of open microcracks are assumed to be responsible for measured velocities higher than those predicted by the theory. The partial saturation results are modelled fairly closely by the Gassmann–Biot theory, assuming heterogeneous saturation for P‐waves.     

Symplectites in upper mantle peridotites: Development and implications for the growth of subsolidus garnet,pyroxene and spinel

Silicate-oxide symplectites in complex mineral intergrowths are relatively common in upper mantle xenoliths and in xenoliths in the Jagersfontein Kimberlite, South Africa.Harzburgites of olivine and high-Al (1.9–3.6 wt%), Ca (0.6–0.9 wt%) and Cr (0.3–0.9 wt%) enstatite contain symplectites of spinel and diopside, or spinel, diopside and lower-Al (0.8–2.2 wt%), Ca (0.1–0.4 wt%) and Cr (0.02–0.8 wt%) enstatite. From textures and mineral chemistries these symplectites are interpreted to have formed by mineral unmixing and migration from Al–Ca–Cr discrete enstatite to adjoining mineral interfaces.Garnet harzburgites are composed of large (0.5–1 cm) olivine, equally large discrete low-Al (0.6–1.1 wt%), Ca (0.1–0.5 wt%), and Cr (0.1–0.3 wt%) enstatite and smaller interstitial garnet, diopside, and high-Cr and low-Al spinel. Symplectites are composed of either spinel+diopside+garnet, or garnet+spinel. Spinel diopside garnet symplectites have cores of spinel+diopside, resembling symplectites inharzburgites, but surrounded by rims of garnet or garnet+undigested globular spinel. From textures and chemistries we suggest that the spinel+diopside cores formed from Ca-Al-Cr-rich orthopyroxene initially as a nonstoichiometric homogeneous single phase clinopyroxene enriched in Fe, Cr and Al. This was followed by decomposition of the clinopyroxene to diopside+spinel, and subsequent garnet formation in a prograde reaction with olivine or enstatite. In bothharzburgites andgarnet harzburgites the metastable cellular structures may also have formed by the simultaneous precipitation of pyroxene and spinel. In all cases there is a strongly preferred embayment of symplectite bodies into olivine. Olivine appears to have activated adjacent