Rock geochemistry of an iron ore field in the Divrigi region, Central Anatolia, Turkey. A new exploration model for iron ores in Turkey     

Henrik Stendal  Taner Ünlü 《Journal of Geochemical Exploration》1991,40(1-3)

One hundred and sixty rock samples of iron ore deposits and their host rocks from the Divrigi iron ore region were analysed for ten major and 31 trace elements, and 30 samples were analysed for rare earth elements. Statistical analyses divide rock types into different units (discriminant analyses) and several element associations (cluster and factor analyses). Individual rock types were also treated statistically. Different element associations and the geochemistry of the REE point to a genetic relationship between ore and host rocks and later hydrothermal overprints.The interpretation suggests iron ores are closely associated with mafic ultramafic rocks. This exploration model has been applied iron ore deposits in central Anatolia, Turkey. The results stimulated first air-magnetic and later ground-magnetic field surveys leading to discovery of new iron ore occurrences which are currently being evaluated for their economic potential.  相似文献   

Inferred Palaeoproterozoic arc rifting along a consuming plate margin: insights from the stratigraphy,volcanology and geochemistry of the Kangerluluk sequence,southeast Greenland     

W. Mueller  J. Dostal  H. Stendal 《International Journal of Earth Sciences》2002,91(2):209-230

The 200- to 300-m-thick volcano-sedimentary sequence in the Kangerluluk Fjord, associated with penecontemporaneous and late-tectonic dykes, as well as a synvolcanic plutonic suite, represents an integral component of the Palaeoproterozoic Ketilidian Mobile Belt, south Greenland. The ca. 1808-Ma Kangerluluk supracrustal sequence contains four distinct mappable lithofacies: (a) a conglomerate-sandstone lithofacies; (b) a pyroclastic lithofacies; (c) a volcanic lithofacies; and (d) a peperite lithofacies. The volcanic lithofacies, up to 200 m thick, is characterized by shallow-water subaqueous brecciated and pillowed flows. Flows are either (a) feldspar-phyric, or (b) feldspar-pyroxene-phyric, with 0.2- to 3-cm-size plagioclase and 0.2- to 3-cm-size pyroxene that constitute between 20 and 30% (locally up to 50%) of the flows. Mafic dykes intruded wet unconsolidated pyroclastic lithofacies, resulting in the formation of peperites. Geochemically, the volcanic and pyroclastic units represent a distinct tholeiitic magmatic suite enriched in incompatible trace elements including Th, La, Yb, Zr and Nb, and exhibiting (La/Yb)_n~10. The plutonic suite and associated dykes display a calc-alkaline trend with enriched LREE and unfractionated flat HREE patterns, La_n ranging between 50 and 100, (La/Yb)_n ratios between 8 and 22, and negative Nb and Ti anomalies on the mantle-normalized, incompatible multi-element patterns. The pillowed flows lie in the continental flood basalt field on the Y-Nb-Zr discrimination diagram, and display a Nb anomaly and K₂O-enrichment that collectively suggest a crustal component and/or a subduction-modified mantle source. The geology, stratigraphy of the Kangerluluk area and geochemistry can be used to infer a change in magma genesis from arc to rift volcanism. The 1850- to 1800-Ma calc-alkaline Julianehåb batholith represents a magmatic arc that rifted during crustal extension, allowing for the ascent of mantle-derived mafic magma. The geochemistry of the mafic volcanic flows, synvolcanic dykes and pyroclastic deposits favours a crustal component in magma genesis and offers new insights into the tectonic evolution of the Ketilidian Mobile Belt.  相似文献   

Water in boninite glass and coexisting orthopyroxene: concentration and partitioning   总被引：3，自引：0，他引：3  

Patrick F. Dobson  Henrik Skogby  George R. Rossman 《Contributions to Mineralogy and Petrology》1995,118(4):414-419

 Spectroscopic measurements of water in glass inclusions in pyroxene from boninite samples from the Bonin Islands conclusively document the high (2.8–3.2 wt %) primary water contents of boninite magmas. Associated quenched glass from pillow lava rims have slightly lower (2.2–2.4 wt %) water contents, suggesting that minor amounts of degassing occurred between the time of melt entrapment in the orthopyroxenes and subsequent eruption on the sea floor. Some zonation of molecular water contents in pillow rim glasses was observed. OH contents of the host orthopyroxene phenocrysts were also measured, allowing for the calculation of partition coefficients for water between boninite melt and orthopyroxene. These values (0.003–0.004) for water partitioning between orthopyroxene and mafic melts may help constrain petrogenetic models of mantle-derived magmas. Received: 20 September 1993 / Accepted: 26 June 1994  相似文献   

Effects of chronic oil pollution from refinery effluent on sediment microflora in a Danish coastal area     

Henrik Grüttner  Kurt Jensen   《Marine pollution bulletin》1983,14(12):456-459

Kalundborg Fjord is a Danish marine area which has been heavily oil polluted by refinery effluent, leading to accumulation of petroleum hydrocarbons in the surface sediments. A study of the occurrence in the sediment of heterotrophic bacteria, yeasts and filamentous fungi has been carried out, and the physiological composition of the microbial community has been recorded. Though the abundance of oil-degrading microorganisms was significant, a correlation between the number of these and the oil content of the sediment could not be demonstrated.  相似文献   

U–Pb dating of plutonic rocks involved in the nappe tectonic in southern Cameroon: consequence for the Pan-African orogenic evolution of the central African fold belt     

Sadrack Felix Toteu  Rose Yongue Fouateu  Joseph Penaye  Jacqueline Tchakounte  Aubin Ciriaque Seme Mouangue  William Randall Van Schmus  Etienne Deloule  Henrik Stendal 《Journal of African Earth Sciences》2006,44(4-5):479

TIMS-ID and SIMS U–Pb dating on zircons from metaplutonic rocks involved in the Pan-African nappe of southern Cameroon allow definition of three groups of subduction-related intrusions: group-I intrusions represented by the Masins metagabbro in the Lomie region yielded 666 ± 26 Ma; group-II intrusions represented by the Mamb metasyenogabbro and the Yaoundé pyriclasite yielded ca. 620 Ma and are broadly coeval with the deposition of the Yaoundé metasediments; group-III intrusions represented by the Elon augen metagranite and the Ngaa Mbappe metamonzodiorite yielded ca. 600 Ma. The onset of the nappe tectonics occurred under high-grade conditions in the range 616 to 610 Ma and continued around 600 Ma with the emplacement of the shallowest nappes. Finally, the construction of southern Cameroon proceeded by a multi-stage evolution characterized by a long-lived development of magmatic arcs associated with rapid opening and closure of sedimentary marginal basins in relation to a northward subduction.  相似文献   

Ecological Cost-Benefit Modelling of Herbivore Habitat Quality Degradation due to Range Fragmentation     

Henrik Lundqvist 《Transactions in GIS》2007,11(5):745-763

Fragmentation of grazing ranges and ensuing rise in edge effects decrease forage range quality for large herbivores. A method is proposed to quantify, in ecological cost‐benefit terms, the negative impact of fragmentation by linear structures with special emphasis on summer ranges of semi‐domesticated reindeer (Rangifer t. tarandus). The method is also applicable to other terrestrial species and on different scales. The term ‘reachability’ is introduced for this measurement, which integrates forage quality, quantity and availability, as well as the costs of the animal's movement in a variable landscape and across fragmenting linear structures. The method uses a cost‐distance algorithm, commonly available in GIS software. Effective distances and reachability over large areas are calculated from evenly distributed sample points. Effects of varying sample point distance, fragmenting structure friction weight and density, and edge effect depth were analysed for model calibration. In an example the model was used for estimation of reachability alteration due to linear structures in the summer ranges of the Handölsdalen reindeer herding district in Sweden, where hourly GPS positions of 10 free‐ranging female reindeer were available. In these data the reindeer population density appeared to decrease up to 1 km away from roads, but no effect from hiking trails was detected. The reachability model quantified a loss of 2.2–2.7% in range quality due to range fragmentation.  相似文献   

The distribution and relative toxic potential of organic chemicals in a PCB contaminated bay     

Sundberg H  Tjärnlund U  Kerman G  Blomberg M  Ishaq R  Grunder K  Hammar T  Broman D  Balk L 《Marine pollution bulletin》2005,50(2):195-207

For reliable monitoring of environmental improvement, the PCB contaminated bay Orserumsviken on Sweden's Baltic coast was investigated prior to remediation. We examined PCB congener patterns and the relative toxic potential of PCBs in extracts of three matrices: bottom sediment, settling particulate matter and the dissolved phase (obtained from semi-permeable membrane devices). Congener patterns were similar in all matrices. Three fractions were isolated from the extracts: (1) aliphatic and monocyclic aromatic compounds (MAC-fraction), (2) dicyclic aromatic compounds (DAC-fraction), including PCBs, and (3) polycyclic aromatic compounds (PAC-fraction), including PAHs. Total extracts and fractions were injected into newly fertilised rainbow trout eggs. At larval stage, hepatic EROD activities were quantified. Though high, the PCB contamination could explain only an estimated 1-5% of the total EROD induction. The order of EROD induction potential was: total extract > PAC-fraction > DAC-fraction > MAC-fraction in all matrices, suggesting that in Orserumsviken PACs made a larger contribution to the EROD induction potential than PCBs and other DACs.  相似文献   

Hydrogen incorporation in orthopyroxene: interaction of different trivalent cations     

Roland?StalderEmail author  Stephan?Klemme  Thomas?Ludwig  Henrik?Skogby 《Contributions to Mineralogy and Petrology》2005,150(5):473-485

The incorporation of hydrogen into ferrosilite, Fe-bearing enstatite and orthopyroxene containing different trivalent cations (Cr³⁺ and Al³⁺, Cr³⁺ and Fe³⁺) was investigated experimentally at 25 kbar. Hydrogen concentration was determined by FTIR-spectroscopy on oriented crystal sections and by secondary ion mass spectroscopy, whereas Mößbauer spectroscopy and optical spectroscopy were used to characterise the valence state of Fe in orthopyroxene. Results suggest that hydrogen incorporation in ferrosilite is achieved by a similar mechanism as in pure enstatite. In Cr-bearing samples, however, hydrogen incorporation is reduced by the presence of other trivalent cations by an increased tendency to form Tschermaks substitutions, e.g. Si _T ⁴⁺ + Mg _M1 ²⁺ ? Al _T ³⁺ + Cr _M1 ³⁺ . Thus, hydrogen solubility in natural orthopyroxenes from the Earth’s mantle, containing significant amounts of Cr³⁺, Al³⁺, and Fe³⁺, may be much more limited than expected from their trivalent cation content, as a large fraction of the trivalent cations does not participate in H-incorporating reactions as 2 Mg _M1 ²⁺ ? M _M1 ³⁺ + V_M1 + H _i ⁺ .  相似文献   

Improved estimates of the natural mortality rates of nine commercially important fish species included in the North Sea Multispecies VPA model   总被引：1，自引：2，他引：1  

Sparholt  Henrik 《ICES Journal of Marine Science》1990,46(2):211-223

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Changes in the North Sea fish community: evidence of indirect effects of fishing?   总被引：7，自引：4，他引：7  

Daan  Niels; Gislason  Henrik; G. Pope  John; C. Rice  Jake 《ICES Journal of Marine Science》2005,62(2):177-188

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