Petrology and geochemistry of greywackes from Goa-Dharwar sector,western Dharwar Craton: Implications for volcanoclastic origin

Late Archaean Supracrustals of the Goa-Dharwar sector (GDS) are composed of a thick sequence of greywacke sequence with narrow intercalations of quartzite, BIF and carbonates. Mafic volcanics occupy the base of the sequence. The greywackes are predominantly tuffacious containing chlorite-sericite and hornblende. Arkosic variations containing biotite dominate the western part of the sector. Fine-grained variations occur as isolated narrow lenses within other types of greywackes. The conglomeratic greywackes are localized along the western and the eastern margins of the sector. All of the greywackes are all typically immature containing coarser clasts of mostly plagioclase (18–23%) and quartz (32–34%). Lithic fragments of felsic volcanic rocks are common. The matrix is dominated by mafic material. Biotite and amphibole are related to metamorphic recrystallization. Chlorite, sericite, epidote, carbonate and chert are products of the interplay of diagenesis and low-grade metamorphism. Fe-Ti oxide, sphene, apatite and zircon are usual accessories. But for slight enrichment in K₂O, the major element chemistry of the GDS greywackes is similar to the chemistry of Late Archaean greywackes. They also compare in respect of V, Co, Hf contents, K₂O/Na₂O, SiO₂/Al₂O₃, Na₂O/Al₂O₃, Ba/Rb, Th/U, La/Th, Sm/Nd ratios, steep REE patterns with distinct LREE enrichment and HREE depletion. The GDS greywackes however are distinctly enriched in Rb, Ba, Sr, Th, U, Cu, Zr, Ce/Ce* and depleted in Cr, Ni, and Zn. The conglomeritic and biotite bearing verities contain considerable proportions of clasts derived from the basement tonalitic/granitic terrain. The common tuffacious greywackes containing hornblende and biotite-sericite however include only volcanic clasts and bear evidence of derivation from submarine weathering of predominantly felsic volcanics erupted on a large scale to form a magmatic arc in the later stages of geosynclinal deposition. Geochemical data suggest that the GDS greywackes were laid down in progressively changing basin geometry from a passive to active continental margin and island arc setting.     

A literature review of the saturation state of seawater with respect to calcium carbonate and its possible significance for scale formation on OTEC heat exchangers

An investigation has been made of available data on the saturation state of seawater with respect to calcium carbonate and its possible significance for scale formation on Ocean Thermal Energy Conversion (OTEC) heat exchangers. Pertinent oceanographic data is lacking at or near potential OTEC sites for the calculation of the degree of saturation of seawater with respect to calcium carbonate. Consequently, only “extrapolated” saturation values can be used. These indicate that near surface seawater is probably supersaturated, with respect to the calcium carbonate phases calcite and aragonite, at all potential OTEC sites. The deep seawater that would be brought to the surface at the potential Atlantic Ocean sites is also likely to be supersaturated with respect to calcium carbonate. The deep seawater at the potential Pacific Ocean sites may be slightly undersaturated.The fact that OTEC heat exchangers will be operating in seawater, which is supersaturated with respect to calcium carbonate, means that if nucleation of calcite or aragonite occurs on the heat exchanger surfaces, significant growth rates of calcium carbonate scale may be expected. The potential for calcium carbonate nucleation is highest at cathodic metal surface locations, which are produced as the result of aluminum corrosion in seawater. Consequently, corrosion and scale formation may be closely related. What the possible effects of biofouling may be on this process are not known.     

Comparative policy analysis: Neoliberalising New Zealand

Comparative policy analysis involves systematically examining the long‐term formation of public policies across a number of societies. It focuses particularly on the sequence of policy regimes: liberalism – Keynesianism/social democracy – neoliberalism. Since 1980, neoliberalism has been widely adopted as the guiding ideological structure for economic policy making. But neoliberalism encounters resistances that vary with national contexts. New Zealand is a particularly interesting case because of its reputation as a social democratic, welfare state that went neoliberal with a vengeance (Rogernomics).     

Research on red tide occurrences using enclosed experimental ecosystems in west Xiamen Harbor, China—Relationship between various factors and red tide occurrences

A series of enclosed ecosystem experiments were conducted in a land-based tank near the seaside of West Xiamen Harbor. The results of experiments conducted in different seasons and years showed a repeatable phytoplankton succession. In this relatively stable ecosystem with added nutrients and trace metals, diatoms dominated initially, dinoflagellates dominated in the later stage, and dinoflagellate red tides eventually occurred. Vitamin B₁₂ enrichment may speed up this succession process. Stirring the water column could stop this process. Soluble Mn at a level of 3–4 μg/L in seawater, which also is the existing concentration of soluble Mn in Xiamen Harbor seawater, is sufficient for the multiplication of algae and occurrence of red tide. The present study showed that excessive soluble Mn in Xiamen Harbor cannot cause red tide, and that Fe was one of the important factors causing diatiom red tide in this present study. Project 39570145 supported by NSFC.     

Rare earth elements in Huronian (Lower Proterozoic) sedimentary rocks: Composition and evolution of the post-Kenoran upper crust

The Huronian sequence (Lower Proterozoicl. north of Lake Huron, contains tillites and abundant fine-grained sedimentary rocks. Analyses of rare earth elements (REE) in the matrix of tillite samples from the Gowganda Formation (~ 2.3 Gal is considered to be a reasonable estimate of upper crustal REE abundances for the region north of Lake Huron at the time of Gowganda deposition. The average is characterized by a moderately steep pattern (σLREEσHREE = 9.1) and a slight negative europium anomaly ($\text{Eu}\text{Eu1}\text{= 0.89}$). This pattern is similar to estimates of the composition of the surface of the Canadian Shield and is intermediate between estimates of typical Archean and post-Archean sedimentary rocks. REE patterns for framework granitoid clasts from the tillite suggest that K-rich granites, which were apparently unimportant in the formation of Archean sedimentary rocks, were abundant in the source regions of the Gowganda Formation. This may explain the intermediate nature of the Gowganda pattern.Comparison of the tillites and associated Gowganda mudstones suggests that previous estimates of upper crustal REE abundances, which were based on the analyses of fine-grained sedimentary rocks, may be systematically high. Relative distributions, however, are the same.Analyses of mudstones from the McKim. Pecors. Serpent Gowganda Lorrain and Gordon Lake Formations suggest rapid evolution in the composition of the exposed upper crust at the close of the Kenoran orogeny. REE patterns at the base of the Huronian are similar to typical Archean sedimentary rocks. REE characteristics change up section: patterns at the top resemble typical post-Archean sedimentary rocks.It is inferred that an essentially episodic change from an early exposed upper crust dominated by a tonalite-greenstone suite to one approximating granodioritic composition is recorded in Huronian sedimentary rocks. A deviation from the evolutionary trend of the Huronian, documented in the Gowganda Formation, may be related to the glacial origin of the Gowganda.     

Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 2: a 200-Year Record of Atmospheric Lead-210 Flux Variations and its Palaeoclimatic Implications

Palaeovariations of the atmospheric ²¹⁰Pb flux in Northeast China (Long Gang area, Jilin province), quantified by high resolution ²¹⁰Pb measurements on seasonally laminated sediments of Lake Sihailongwan are presented on decadal scale. The mean flux of unsupported ²¹⁰Pb between 1790 and 1970 for the centre of the lake basin is 517 Bq m⁻² yr⁻¹ with maximum deviations between −23% and +27% of this value. Flux rates above this average were found between 1783 and 1813, around 1836, and between 1860 and 1901. The mean ²¹⁰Pb^exc flux rates derived were clearly lower around 1821, 1908, 1930, and 1953. The ²¹⁰Pb^exc flux reached its minimum of 344 Bq m⁻² yr⁻¹ during the period 1977–1982. The atmospheric flux of unsupported ²¹⁰Pb is correlated with the precipitation frequency during the summer monsoon and shows coinciding variability with geochemical proxies that document the groundwater inflow into the lake. Al₂O₃-rich dust of remote provenance scavenged by wet-deposition in the rainy season is the major carrier of the atmospheric ²¹⁰Pb^exc flux.     

澳大利亚的第三纪及第三纪一第四纪过渡期

第三纪的板块运动驱动着澳大利亚的气候和植被进行演化。广布的湿润森林区是澳 大利亚早第三纪的特征。一直到始新世,生物多样性都在不断地提高。毫无疑问,这是澳大利亚由高南纬区向北部中纬区运移的结果。从始新世到上新世,澳大利亚的气候总体上要比现在湿润,但降水量季节性变化的增强推动了中新世以后硬叶植物和旱生植物的发展。上新世晚期似乎与第四纪一样,都出现过周期性干旱。这种干旱与冰期条件有关,至少由南澳大利亚晚第四纪的记录可以认识到这一点,澳大利亚的这段历史与东亚的气候变迁是同步发生的。在东亚,印-澳板块的运动致使青藏高原抬升,从而引发了区内乃至全球气候的巨变。穿越赤道区的季风和信风的环流格局致使晚第三纪和第四纪中国与澳大利亚的气候系统的相关性更强。     

Geology and petroleum potential of the Fairway Basin in the Tasman Sea

The Fairway Basin is a large, generally north – south-trending, sediment-filled structure in water 1500 – 3000 m deep, on the eastern slope of the Lord Howe Rise in the Tasman Sea, and is partly within Australian jurisdiction. It was poorly known until a few years ago, when seismic profiling and piston coring cruises were carried out. The basin, about 1100 km long and 120 – 200 km wide, can be divided into three segments—north, central and south—that trend northwest, north and north-northwest, respectively. All three segments probably formed by thinning of continental crust during breakup of Lord Howe Rise and surrounding aseismic continental ridges in the Late Cretaceous and Paleocene. Normal faulting, large inputs of terrigenous sediment and subsidence to bathyal marine depths occurred during that time. A period of compression, perhaps related to overthrusting on New Caledonia, occurred in the Eocene, leading to uplift (and in parts, erosion) of northern Lord Howe Rise, and reversal of faulting in the basin. By the Oligocene, the area was again in bathyal depths, and pelagic ooze and some turbidites accumulated. The basinal sequence is generally 2000 – 4000 m thick, with 1200 – 3200 m of Cretaceous to Eocene sediment concentrated in depocentres, capped by 500 – 800 m of Oligocene and younger sediment. In the depocentres, numerous sedimentary diapirs pierce sedimentary sequences. The sedimentary diapirs appear to be fed by Cretaceous muds deposited during rifting. Often, these diapirs are overlain by faults extending to the seafloor, and hummocky bathymetry is possibly caused by fluid escape. The overall geology suggests that the Fairway Basin may be a large frontier hydrocarbon province. Seismic profiles display a bottom-simulating reflector above many depocentres, 500 – 700 m below the seafloor. The bottom-simulating reflector has positive polarity, which could result from a diagenetic phase transformation, a thin gas hydrate layer with a sharp top, or from the sharp base of a gas layer (probably beneath gas hydrates). Standard piston cores taken above diapirs and apparent fluid-escape features have recovered little gas. Other than drilling, the next steps in assessing petroleum potential are to clearly document fluid-escape structures, and to sample any fluids emitted for hydrocarbons.     

Large-scale structure in the NIR-selected MUNICS survey

The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep, photometric survey selected in the K' band. The project's main scientific aims are the identification of galaxy clusters up to redshifts of unity and the selection of a large sample of field early-type galaxies up to z < 1.5 for evolutionary studies. We created a Large Scale Structure catalog, using a new structure finding technique specialized for photometric datasets, that we developed on the basis of a friends-of-friends algorithm. We tested the plausibility of the resulting galaxy group and cluster catalog with the help of Color-Magnitude Diagrams (CMD), as well as a likelihood- and Voronoi-approach. This revised version was published online in August 2006 with corrections to the Cover Date.     

Local amplification of deep mining induced vibrations Part 1: Experimental evidence for site effects in a coal basin

The work presented in this paper lies under the scope of a research program aiming to assess the impact of deep coal mining induced vibrations on the surface constructions. The concerned section of the program is dedicated to the study of geological site effects and their influence on the mining induced vibrations for which the experimental investigations have been carried out and developed in this paper (Part 1). The empirical methods based on H/V spectral ratios have been applied on data sets provided from mining induced vibrations recorded within private residences above the deep coalmine as well as complementary measurements of ambient noise. The results evidence an amplified zone in the southern part of the Gardanne basin where drilling data confirmed the presence of particularly fractured and soft stratigraphic units. This joint analysis of induced seismicity and ambient noise enabled to validate the method based on H/V ratios applied to the mining context.