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51.
An improved method for the direct determination of organic carbon in calcareous marine sediments, organisms and particulate matter is described. Samples are dissolved in phosphoric acid to remove carbonates, purged with oxygen to remove CO2, and the resulting acidic solution is analysed for total (dissolved and particulate) organic carbon. The method is rapid, involves minimal sample manipulation, and is both accurate (better than ± 2%) and precise (better than ± 0.2 mg organic carbon/g sediment). The method is especially suitable for modern carbonate sediments which have low levels of predominantly acid-soluble organic carbon. 相似文献
52.
Persistent halogenated compounds in black guillemots (Cepphus grylle) from Greenland--levels, compound patterns and spatial trends 总被引:1,自引:0,他引:1
Twenty-seven black guillemot eggs and 39 livers were analysed for polychlorinated biphenyls (PCBs), chlorinated pesticides including chlordane-related compounds and toxaphene, and polybrominated diphenylethers (PBDEs). The samples were collected at Qeqertarsuaq (Godhavn, West Greenland) and Ittoqqortoormiit (Scoresbysund, East Greenland). The concentrations of halogenated organic compounds in samples from East Greenland were somewhat higher than the corresponding concentrations from West Greenland. Differences in compound patterns were found between West and East Greenland, with higher percentages of the heavier PCB molecules, p,p(')-DDE and alpha-HCH in the samples from Ittoqqortoormiit. Similarly, different levels and different compositions were observed for eggs and livers. The eggs had generally higher concentrations of all compounds as well as higher percentages of CHB-50, CHB-62 and alpha-HCH than liver samples from the same area. Dividing the liver samples into age groups revealed increasing concentrations with age. 相似文献
53.
The potential discharge of groundwater contaminated by oil sands process‐affected water (OSPW) is a concern for aquatic ecosystems near tailings ponds. Groundwater in the area, but unaffected by OSPW, may contain similar compounds, complicating the assessment of potential ecological impacts. In this study, 177 shallow groundwater samples were collected from riparian areas along the Athabasca River and tributaries proximate to oil sands developments. For “pond‐site” samples (71; adjacent to study tailings pond), Canadian aquatic life guidelines were exceeded for 11 of 20 assessed compounds. However, “non‐pond” samples (54; not near any tailings pond) provided similar exceedances. Statistical analyses indicate that pond‐site and non‐pond samples were indistinguishable for all but seven parameters assessed, including salts, many trace metals, and fluorescence profiles of aromatic naphthenic acids (ANA). This suggests that, regarding the tested parameters, groundwater adjacent to the study tailings pond generally poses no greater ecological risk than other nearby groundwaters at this time. Multivariate analyses applied to the groundwater data set separated into 11 smaller zones support this conclusion, but show some variation between zones. Geological and potential OSPW influences could not be distinguished based on major ions and metals concentrations. However, similarities in indicator parameters, namely ANA, F, Mo, Se, and Na‐Cl ratio, were noted between a small subset of samples from two pond‐site zones and two OSPW samples and two shallow groundwater samples documented as likely OSPW affected. This indicator‐based screening suggests that OSPW‐affected groundwater may be reaching Athabasca River sediments at a few locations. 相似文献
54.
Present and projected degree days in China from observation,reanalysis and simulations 总被引:1,自引:0,他引:1
Qinglong You Klaus Fraedrich Frank Sielmann Jinzhong Min Shichang Kang Zhenming Ji Xiuhua Zhu Guoyu Ren 《Climate Dynamics》2014,43(5-6):1449-1462
Degree days are usually defined as the accumulated daily mean temperature varying with the base temperature, and are one of the most important indicators of climate changes. In this study, the present-day and projected changes of four degree days indices from daily mean surface air temperature output simulated by Max Planck Institute, Earth Systems Model of low resolution (MPI-ESM-LR) model are evaluated with the high resolution gridded-observation dataset and two modern reanalyses in China. During 1979–2005, the heating degree days (HDD) and the numbers of HDD (NHDD) have decreased for observation, reanalyses (ERA-Interim and NCEP/NCAR) and model simulations (historical and decadal experiments), consistent with the increasing cooling degree days (CDD) and the numbers of CDD (NCDD). These changes reflect the general warming in China during the past decades. In most cases, ERA-Interim is closer to observation than NCEP/NCAR and model simulations. There are discrepancies between observation, reanalyses and model simulations in the spatial patterns and regional means. The decadal hindcast/forecast simulation performance of MPI-ESM-LR produce warmer than the observed mean temperature in China during the entire period, and the hindcasts forecast a trend lower than the observed. Under different representative concentration pathway (RCP) emissions scenarios, HDD and NHDD show significant decreases, and CDD and NCDD consistently increase during 2006–2100 under RCP8.5, RCP4.5 and RCP2.6, especially before the mid-21 century. More pronounced changes occur under RCP8.5, which is associated with a high rate of radiative forcing. The 20th century runs reflect the sensitivity to the initial conditions, and the uncertainties in terms of the inter-ensemble are small, whereas the long-term trend is well represented with no differences among ensembles. 相似文献
55.
Tsanyao?Frank?YangEmail author Gao-Hua?Yeh Ching-Chou?Fu Cheng-Chen?Wang Te-Fang?Lan Hsiao-Fen?Lee Cheng-Hong?Chen Vivek?Walia Quo-Cheng?Sung 《Environmental Geology》2004,46(8):1003-1011
Many mud volcanoes are distributed along the tectonic sutures in southern Taiwan and can be divided into five zones based on their relative positions in different tectonic domains. Most active mud volcanoes are exhaling methane-dominated gases. Nevertheless, some gases show unusual carbon dioxide-dominated and/or nitrogen-excess compositions. This implies that there are multiple sources for the gas compositions of mud volcanoes in Taiwan.For better understanding the total amount of exhalation gases and its flux, the gas flow and compositions were continuously measured in the interval of two minutes at Chung-lun (CL) bubbling mud pool for a few months. The major compositions of gases exhaling from this site were 75~90% of CO2 and 5~12% of CH4. The amount of gases exhaling from the mud pool can be estimated to be about 1.4 ton/year for CH4 and 28 ton/year for CO2, respectively. The preliminary results of exhaling gas flux from the major vents of representative active mud volcanoes, yielded an estimated total CH4 output of the mud volcanoes in Taiwan of ca. 29 ton/year during quiescent period. 相似文献
56.
The Hellenic ophiolites: eastward or westward obduction of the Maliac Ocean, a discussion 总被引:1,自引:0,他引:1
Jacky Ferrière Frank Chanier Pitaksit Ditbanjong 《International Journal of Earth Sciences》2012,101(6):1559-1580
Ophiolitic bodies in the Dinaro-Hellenic mountain belt are among the most important ones in the Peri-Mediterranean Alpine chains. The characteristic feature of this ophiolitic belt is its Middle to Late Jurassic age of obduction. The ophiolitic bodies form two major belts on each side of the Pelagonian zone: an east Pelagonian belt in the Vardarian domain and a Supra-Pelagonian ophiolitic belt (SPO) to the west. The different hypotheses relative to the origin of the SPO present geodynamic evolution models accounting for most of the available data: a mid-Triassic episode of rifting; a Ladinian–Jurassic episode of sea-floor spreading forming notably the Maliac Ocean; a Middle to Late Jurassic convergent period with subduction and obduction episodes, and finally, a late episode of Tertiary compressional deformation responsible for the westward thrusting of the Jurassic ophiolitic nappes over the external zones. Despite many studies dating from the early 1970s, the eastern or western Pelagonian origin of these ophiolites, especially the SPO, is still under dispute. Whatever the adopted hypothesis, we consider that the main SPO bodies (N-Pindos, Vourinos, Othris, Evia, Argolis) have the same origin because of their geographic continuity and of the similarities in their geological characteristics. We propose that this ocean corresponds everywhere to the Maliac Ocean, defined in Othris from the well-preserved sedimentary (oceanic margin) and ophiolitic nappes thrust during the Late Jurassic obduction onto the Pelagonian platform. There is strong evidence for the existence of two deep basins on both sides of the Pelagonian continental ridge during Triassic–Jurassic times. They correspond, respectively, to the Vardar area to the east and the Pindos domain to the west, one of these domains being at the origin of the SPO. The hypothesis of an eastward emplacement of the SPO from the Pindos domain is based mainly on sedimentological data from the margin series and on structural analyses of ophiolitic bodies. However, we conclude the westward obduction of the Maliac Ocean, originating from the Vardar area, to be the best fitting model. This westward model is supported by paleogeographic and structural constraints on regional scale. Notably, the absence of obducted ophiolites in the Jurassic series of the Koziakas units (units attributed to the western Pelagonian margin) and of the Parnassus domain (on the eastern side of the Pindos basin) is difficult to reconcile with an eastward obduction from the Pindos domain. Other observations, such as the distribution of ophiolitic detritus in the internal and external zones, also promote the westward Late Jurassic obduction of the Maliac Ocean. Our preferred model offers a consistent explanation for the mechanism and timing of the emplacement of the SPO, as well as providing insight on the origin and emplacement of the Vardarian ophiolites. Following this hypothesis, there is no need for a clear boundary between the SPO and the west Vardarian ophiolitic bodies as they were obducted from the same oceanic basin and during the same Jurassic tectonic event. In this paper, we develop evidence in favor of the eastern Pelagonian origin for the SPO (our adopted model) and provide discussion on the data supporting the main alternative hypothesis (western origin for the SPO). 相似文献
57.
Frank Wlotzka 《Meteoritics & planetary science》1991,26(3):255-262
58.
Regional-scale hydrothermal alteration in the Central Blake River Group,western Abitibi subprovince,Canada: implications for VMS prospectivity 总被引:1,自引:0,他引:1
Mark?D.?HanningtonEmail author Frank?Santaguida Ingrid?M.?Kjarsgaard Larry?M.?Cathles 《Mineralium Deposita》2003,38(4):393-422
The Late Archean Blake River Group is a thick succession of predominantly mafic volcanic rocks within the southern zone of the Abitibi greenstone belt. It contains a number of silicic volcanic centers of different size, including the large Noranda volcanic complex, which is host to 17 past-producing volcanogenic massive sulfide deposits. The Noranda complex consists of a 7- to 9-km-thick succession of bimodal mafic and felsic volcanic rocks erupted during five major cycles of volcanism. Massive sulfide formation coincided with a period of intense magmatic activity (cycle III) and the formation of the Noranda cauldron. Hydrothermal alteration in these rocks is interpreted to reflect large-scale hydrothermal fluid flow associated with rapid crustal extension and rifting of the volcanic complex. The alteration includes abundant albite, chlorite, epidote and quartz (silicification), which exhibit broad stratigraphic and structural control and correlate with previously mapped whole-rock oxygen isotope zonation. The Mine Sequence volcanic rocks are characterized by abundant iron-rich chlorite (Fe/Fe+Mg >0.5), hydrothermal amphibole (ferroactinolite) and coarse-grained epidote of clinozoisite composition (<10 wt% Fe 2O 3). Volcanic rocks of the pre-cauldron sequences, which contain only subeconomic stringer mineralization, are characterized by less abundant chlorite and mainly fine-grained epidote (>10 wt% Fe 2O 3) lacking the clinozoisite solid solution. Alteration in the Mine Sequence volcanic rocks persists along strike well beyond the limits of the main ore deposits (as far as several tens of kilometers) and can be readily distinguished from greenschist facies metamorphic assemblages at a regional scale. The lack of similar alteration in the pre-cauldron sequences is consistent with limited 18O-depletion and suggests that the early history of the volcanic complex did not support large-scale, high-temperature fluid flow in these rocks. Comparisons with a much smaller, barren volcanic complex in nearby Ben Nevis township reveal important differences in the alteration mineralogy between volcanoes of different size, with implications for area selection during regional-scale mineral exploration. The Ben Nevis Complex consists of a 3- to 4-km-thick succession of mafic, intermediate and felsic volcanic rocks centered on a small subvolcanic intrusion. Alteration of the volcanic rocks comprises mainly low-temperature assemblages of prehnite, pumpellyite, magnesium-rich chlorite (Fe/Fe+Mg <0.5), iron-rich epidote (>10 wt% Fe 2O 3) and calcite. Actinolite ± magnetite alteration occurs proximal to the intrusive core of the complex, but the limited extent of this alteration indicates only local high-temperature fluid circulation adjacent to the intrusion. A distal zone of carbonate alteration is located 4–6 km from the center of the volcano. Although iron-bearing carbonates are present locally within this zone, the absence of siderite argues against a high-temperature origin for this alteration. These observations do not offer positive encouragement for the existence of a fossil geothermal system of sufficient size or intensity to have produced a large massive sulfide deposit. 相似文献
59.
60.