Geology and geochemistry of Pachmarhi dykes and sills,Satpura Gondwana Basin,central India: problems of dyke-sill-flow correlations in the Deccan Traps     

Hetu C. Sheth  Jyotiranjan S. Ray  Ranjini Ray  Loÿc Vanderkluysen  John J. Mahoney  Alok Kumar  Anil D. Shukla  Partha Das  Subhrashis Adhikari  Bikashkali Jana 《Contributions to Mineralogy and Petrology》2009,158(3):357-380

Many tholeiitic dyke-sill intrusions of the Late Cretaceous Deccan Traps continental flood basalt province are exposed in the Satpura Gondwana Basin around Pachmarhi, central India. We present field, petrographic, major and trace element, and Sr–Nd–Pb isotope data on these intrusions and identify individual dykes and sills that chemically closely match several stratigraphically defined formations in the southwestern Deccan (Western Ghats). Some of these formations have also been identified more recently in the northern and northeastern Deccan. However, the Pachmarhi intrusions are significantly more evolved (lower Mg numbers and higher TiO₂ contents) than many Deccan basalts, with isotopic signatures generally different from those of the chemically similar lava formations, indicating that most are not feeders to previously characterized flows. They appear to be products of mixing between Deccan basalt magmas and partial melts of Precambrian Indian amphibolites, as proposed previously for several Deccan basalt lavas of the lower Western Ghats stratigraphy. Broad chemical and isotopic similarities of several Pachmarhi intrusions to the northern and northeastern Deccan lavas indicate petrogenetic relationships. Distances these lava flows would have had to cover, if they originated in the Pachmarhi area, range from 150 to 350 km. The Pachmarhi data enlarge the hitherto known chemical and isotopic range of the Deccan flood basalt magmas. This study highlights the problems and ambiguities in dyke-sill-flow correlations even with extensive geochemical fingerprinting.  相似文献   

Early Cretaceous fish trails from La Rioja, Spain     

Loïc Costeur  Rubn Ezquerra 《Cretaceous Research》2009,30(4):1027-1030

We report a new find of the fish trail Undichna unisulca in fluvial sediments of the Lower Cretaceous Oliván Group of the Cameros Basin (Aptian-Albian; Valtrujal, La Rioja, northern Spain). It is the second Mesozoic record of Undichna unisulca after the first discovery in the Lower Cretaceous of central Spain (Las Hoyas, Cuenca, central Spain). The trails are characterized by single sinusoidal waves which in this case are often surrounded by well-preserved lateral levees that rule out an undertrail hypothesis.The continental depositional setting, a floodplain fluvial system, reflects the known broad palaeoenvironmental distribution of Undichna and confirms its occurrences in freshwater settings.  相似文献   

Removal of arsenic (V) from aqueous solutions using chemically modified sawdust of spruce (Picea abies): Kinetics and isotherm studies     

M. Urík M.Sc.  P. Littera  J. >Sevc Ph.D.  M. Kolen>cík  S. >Cer>nanský M.Sc. 《International Journal of Environmental Science and Technology》2009,6(3):451-456

Arsenic is a ubiquitous element in the environment and occurs naturally in both organic and inorganic forms. Under aerobic condition, the dominant form of arsenic in waters is arsenate, which is highly mobile and toxic. Arsenic poisoning from drinking water remains a serious world health issue. There are various standard methods for arsenic removal from drinking waters (coagulation, sorption, ion-exchange reactions or methods of reverse osmosis) and alternative methods, such as biosorption. Biosorption of arsenic from natural and model waters by native or chemically modified (with urea or ferric oxyhydroxides) plant biomass prepared from sawdust of Picea abies was studied. The kinetic of the adsorption process fitted well the pseudo second order adsorption model and equilibrium was achieved after 2 h. The results showed that biosorption was well described by both Langmuir and Freundlich isotherms. The maximum biosorption capacity of the sawdust modified with ferric oxyhydroxides, evaluated by Langmuir adsorption model, was 9.259 mg/g, while the biosorption capacity of unmodified biosorbent or biosorbent modified with urea was negligible. The adsorption capacity is comparable to results published by other authors, suggesting that the prepared chemically modified biosorbent has potential in remediation of contaminated waters.  相似文献   

Dating the exhumation of UHP rocks and associated crustal melting in the Norwegian Caledonides   总被引：2，自引：0，他引：2  

Urs?Sch?rerEmail author  Lo?c?Labrousse 《Contributions to Mineralogy and Petrology》2003,144(6):758-770

U–Pb and Rb–Sr dating was undertaken in combination with P–T estimates to (1) constrain the time of ultrahigh-pressure (UHP) eclogite formation in the Stadlandet UHP province of Norway, (2) date later crustal melting–migmatization of the eclogite country gneisses, and (3) temporally trace post-migmatite cooling and retrogression under amphibolite facies metamorphic conditions. In contrast to earlier U–Pb studies which used accessory minerals from the gneisses, we focused on the direct dating of minerals defining the HP assemblage. For the eclogite, rutile and omphacite fractions were analyzed for U–Pb, and from an adjacent migmatite leucosome titanites and K-feldspar. For Rb–Sr dating, phengite was measured for the eclogite, and biotite for two leucosome layers of the migmatite–eclogite complex. A U–Pb age of 389±7 (2σ) Ma is obtained if the full set of 12 rutile and five omphacite analyses is regressed (MSWD: 16), and 389±2 Ma for those nine data which strictly satisfy isochron conditions (MSWD: 0.78). The 389-Ma age is interpreted to date equilibration and freezing of the eclogite paragenesis at maximum temperatures of 770 °C, reached during decompression to 1.8 GPa. Decompression from 2.8 to 1.8 GPa occurred in the partial melting domain of granitic crust, with the migmatites being dated at 375±6 Ma by titanite and K-feldspar from an eclogite-adjacent granitic leucosome. This titanite age also shows that the U–Pb chronometer in rutile is very robust to high temperatures—it remained a closed system for at least 14 million years, at temperatures in excess to 650 °C. After decompression and migmatization, exhumation is accompanied by rapid cooling to reach the 300 °C isograde by 357± 9 Ma, determined by a biotite isochron for a leucosome in a slightly shallower structural level. In considering that the time of maximum pressure is bracketed by early zircon crystallization during subduction and later omphacite–rutile equilibration in the eclogites, an exhumation rate of 5 mm/year is deduced for initial exhumation, occurring between 394 and 389 Ma. For subsequent cooling from 770 to 600 °C, we obtain a rate of 2.3±1.3 mm/year. First stages of exhumation most likely occurred under an overall compressional regime, whereas Devonian basin formation is associated to detachment movements during 389–375 Ma exhumation. This period of extension is followed by a much younger, decoupled thermal phase at 327±5 Ma, occurring under static conditions within very restricted zones, most likely in association with the circulation of fluid phases along old discontinuities. Initial isotopic signatures of Sr and Pb substantiate Paleo- to Meso-Proterozoic crust formation times of the Stadlandet UHP province precursor lithologies.  相似文献   

Rutile/TiO<Subscript>2</Subscript>II phase equilibria     

Anthony?C.?WithersEmail author  Eric?J.?Essene  Youxue?Zhang 《Contributions to Mineralogy and Petrology》2003,145(2):199-204

The transition between rutile and α-PbO₂ structured TiO₂ (TiO₂II) has been investigated at 700–1,200 °C and 4.2–9.6 GPa. Hydrothermal phase equilibrium experiments were performed in the multi-anvil apparatus to bracket the phase boundary at 700, 1,000, and 1,200 °C. The equilibrium phase boundary is described by the equation: P (GPa)=1.29+0.0065 T ( °C). In addition, growth of TiO₂II was observed in experiments at 500 and 600 °C, although growth of rutile was too slow to bracket unambiguously the equilibrium boundary at these temperatures. Water was not detected in either rutile or TiO₂II, and dry synthesis experiments at 1,200 °C were consistent with the phase boundary determined in the fluid-bearing experiments, suggesting that the equilibrium is unaffected by the presence of water. Our bracket of the phase boundary at 700 °C is consistent with the reversed, dry experiments of Akaogi et al. (1992) and the reversals of Olsen et al. (1999). The new data suggest that the phase boundary is linear, in agreement with Akaogi et al. (1992), but in striking contrast to the phase diagram inferred by Olsen et al. (1999). The natural occurrence of TiO₂II requires formation pressures considerably higher than the graphite–diamond phase boundary.  相似文献   

A comparison of brachyuran crab community structure at four mangrove locations under different management systems along the Melaka Straits-Andaman Sea Coast of Malaysia and Thailand   总被引：2，自引：0，他引：2  

Elizabeth?C.?AshtonEmail author  Peter?J.?Hogarth  Donald?J.?Macintosh 《Estuaries and Coasts》2003,26(6):1461-1471

Brachyuran crab community structure was compared between mangrove sites under different management systems from four locations along the Melaka Straits-Andaman Sea Coast. Klong Ngao, a mangrove estuary in Ranong Province of southern Thailand, lies within a Biosphere Reserve designated in 1997. Sites were positioned in plantations at a former charcoal concession forest, a disused tin mine, and an abandoned shrimp pond along this estuary. The Merbok estuary in Kedah, Malaysia, is partially managed: the mangroves are cut for charcoal and poles on a small scale and the forests are left to regenerate naturally. The Matang Mangrove Forest Reserve in Perak, Malaysia, is heavily exploited but well managed, forRhizophora wood to produce charcoal, and has been for 100 years. Sites were positioned in plantations of different ages. Kuala Selangor Nature Park, Selangor, Malaysia, was established as a nature reserve in 1987 and contains mature mangrove forest regenerating naturally from previous selective felling. At Klong Ngao and Matang, mature reserve forest sites were also studied for comparison with plantation sites. The sites included both upstream and downstream locations and were of similar area, minimizing effects from possible species-area relationships. Sites were chosen with similar environmental conditions and with a dominance ofRhizophora spp. At each site per location, the brachyuran crabs were sampled quantitatively in 100 m² quadrats by three independent 15-min timed crab catches. The crab community recorded was analyzed by univariate and multivariate statistical techniques. Management history plays an important role in moderating the crab community structure. The crab community also changes with the age of the mangrove forest stand. Sesarmid crabs consistently dominated in mature forests, whereas young plantations were colonized mainly by ocypodid crabs. The findings show that heavily effected sites—e.g., disused tin mining areas, former concession forests, and abandoned shrimp ponds—can be rehabilitated by planting mangroves and that the crab community is a useful ecological indicator of habitat status.  相似文献   

Convection and crystal settling in sills     

Fergus G. F. Gibb  c. Michael B. Henderson 《Contributions to Mineralogy and Petrology》1992,109(4):538-545

It has been advocated that convective and crystal settling processes play significant, and perhaps crucial, roles in magmatic differentiation. The fluid dynamics of magma chambers have been extensively studied in recent years, both theoretically and experimentally, but there is disagreement over the nature and scale of the convection, over its bearing on fractionation and possibly over whether it occurs at all. The differential distribution of modal olivine with height in differentiated alkaline basic sills provides critical evidence to resolve this controversy, at least for small to medium-large magma chambers. Our own and others' published data for such sills show that, irrespective of overall olivine content, modal olivine contents tend to increase in a roughly symmetrical manner inwards from the upper and lower margins of the sill, i.e. the distribution patterns are more often approximately D-shaped rather than the classic S-shape generally ascribed to gravity settling. We concur with the majority of other authors that this is an original feature of the filling process which has survived more or less unchanged since emplacement. We therefore conclude that the magmas have not undergone turbulent convection and that gravity settling has usually played only a minor modifying role since the intrusion of these sills. We offer a possible explanation for the apparent contradiction between fluid dynamical theory and the petrological evidence by suggesting that such sills rarely fill by the rapid injection of a single pulse of magma. Rather, they form from a series of pulses or a continuous pulsed influx over a protracted interval during which marginal cooling severely limits the potential for thermal convection.  相似文献   

Durchschnittliche Schwankung und Periodenlänge von Jahresring-Breitenkurven als Klima-Indikatoren     

Prof. Dr. Dr. h. c. Bruno Huber 《International Journal of Earth Sciences》1964,54(1):441-448

Zusammenfassung Die Schwankungen der Jahresringbreiten von Jahr zu Jahr sind nicht nur bei verschiedenen Holzarten verschieden (bei Buche grö\er als bei Eiche, bei Lärche grö\er als bei Zirbelkiefer), sie zeigen auch bei derselben Holzart säkulare Schwankungen, mit einem Minimum in der Bronzezeit und im hohen Mittelalter (12.–13. Jahrhundert) sowie einem Maximum in der Jungsteinzeit und im 17. Jahrhundert (der c="/content/h53352116176gg51/xxlarge8222.gif" alt="ldquor" align="MIDDLE" BORDER="0">kleinen Eiszeitc="/content/h53352116176gg51/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">). Eine geographische c="/content/h53352116176gg51/xxlarge8222.gif" alt="ldquor" align="MIDDLE" BORDER="0">Eichungc="/content/h53352116176gg51/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0"> ergibt, da\ die Schwankungen in Mitteleuropa von Westen nach Osten zunehmen, da\ also stärkere Schwankungen als Zeichen eines irgendwie kontinentaleren Klimas gelten können.Auch die c="/content/h53352116176gg51/xxlarge8222.gif" alt="ldquor" align="MIDDLE" BORDER="0">Periodenlängec="/content/h53352116176gg51/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0"> von Jahresringbreiten-Kurven, d. h. die Zahl der Jahre, in welchen die Breite ohne Unterbrechung steigt oder fällt, weicht gesetzmä\ig von reiner Zufallsverteilung ab. Auch diese Kennzahl scheint klimabedingt säkularen Schwankungen zu unterliegen, deren statistische Sicherung noch geprüft wird.

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ckquote>Summary The average annual fluctuation of ring width shows secular differences with minimum in the bronce age and the high middle ages, and a maximum in neolithic times and the so called c="/content/h53352116176gg51/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">little ice timec="/content/h53352116176gg51/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> of the 17th century. This seems to be a sign of continental climate in the times of higher annual fluctuation.The same may hold truth for the average number of years the ring width increases or decreases (c="/content/h53352116176gg51/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">length of periodsc="/content/h53352116176gg51/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0">), a more frequent reversal of increasing to decreasing and vice versa being a sign of continental climate.ckquote>  相似文献   

Versuch einer meeresmorphologischen Deutung von Satelliten-Luftbildern     

Dr. Egbert Haase  Heinz Kaminski  Professor Dr. dr. h.c. Max Pfannenstiel 《Ocean Dynamics》1969,22(5):193-204

Zusammenfassung Während man schon seit einiger Zeit Satelliten-Luftbilder für Festlandsbereiche interpretierte, nahm man allgemein an, daß die Meere auf diesen Bildern von einem einheitlichen und undifferenzierten c="/content/p2707q6150775w56/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">Schwarzc="/content/p2707q6150775w56/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> wiedergegeben würden. Es stellte sich aber heraus, daß auf manchen Bildern im Bereich der Meere deutlich verschiedene Grautönungen zu erkennen sind, die die Vermutung aufkommen lassen, es könne hier ein primärer oder zumindest sekundärer Zusammenhang mit submarinen Strukturen bestehen und es müßten sich somit Satelliten-Luftbilder auch meeresmorphologisch auswerten lassen.Zur Prüfung dieser Möglichkeit wurden in der vorliegenden Arbeit aus einer Fülle von Aufnahmen 27 Satelliten-Luftbilder mit entsprechenden Seekarten und anderen Unterlagen verglichen. Es zeigten sich an einigen Stellen verblüffende Übereinstimmungen von gewissen Grautönungen mit bekannten submarinen Formen, während an vielen anderen Stellen zunächst nur unsichere Aussagen möglich sind. Vor allem läßt sich derzeit noch nicht entscheiden, ob und wieweit primäre oder sekundäre Zusammenhänge bestehen.Die zur Beurteilung der Satellitenbilder notwendigen technischen Angaben bezüglich des Aufnahme- und Übertragungsverfahrens werden kurz resumiert, ausführlicher wird darüber an anderen Stellen (vgl. Schrifttum) berichtet.Eine kritische Diskussion des Problems der Eindringtiefe von Licht in Wasser führte zu der Annahme, daß im Bereich des Sonnenreflexes größere Tiefen als bislang vermutet ausgeleuchtet werden und sich aus der c="/content/p2707q6150775w56/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">Zusammenschauc="/content/p2707q6150775w56/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> aus großer Höhe veränderte optische Bedingungen ergeben können, als wir sie gewohnt sind.Insgesamt sprechen die Ergebnisse dafür, daß die Aussagefähigkeit der Methode noch an technischen Mängeln und dergleichen leidet, im Prinzip aber doch neue Beiträge zur Ozeanographie erwarten läßt.

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ckquote>Essay of an ocean-morphological interpretation of Satellite-air-Picturesckquote>ckquote>Summary While for some time, Satellite-air-Pictures have already been interpreted for evaluation in the continental sphere, it was generally assumed that the oceans in such pictures were shown in an uniform and undifferentiated c="/content/p2707q6150775w56/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">blackc="/content/p2707q6150775w56/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> colour. However, it was concluded that on some of these photos, showing the oceans, greyish shades were clearly visible which fact led to the assumption that one is confronted here primarily or, at least, secondarily by a coherence with submarine structures and, therefore, Satellite-air-Photos could perhaps also be construed in an ocean-morphological way.In order to test such a possibility, 27 Satellite-air-Photos out of a lot of pictures have been compared with the respective sea-charts and other data. In some instances, amazing conformities of certain greyish hues with the known substratal forms got visible, while in many other spots, so far, only vague statements can be made. First of all, at this point, it cannot as yet be decided whether and how far a primary or secondary context exists.The necessary technical data for the evaluation of such Satellite-air-Photos, with reference to the receiving and transmitting procedures, will be summarized in short, yet reports in greater detail can be found in the comparable literature.A critical discussion of the problems of depth of light-penetration into the water led us to the assumption that in the sphere of sunreflexes greater depths than so far presumed can be reached and, by the synoptical view from enormous heights, completely changed optical conditions may result, than we are so far used until now.Altogether, the results prove that the capacity of this method is still suffering from technical shortcomings, principally however, new contributions to oceanography can be expected.ckquote>

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ckquote>Essai d'une exploitation des images par satellites pour la morphologie marineckquote>ckquote>R&eacute;sum&eacute; Tandis que depuis quelque temps d&eacute;jà on interpr&eacute;tait des images par satellites de zones continentales, il &eacute;tait admis en g&eacute;n&eacute;ral que les mers, sur ces images, seraient rendues par un «noir» uniforme sans nuances. Mais en fait, sur plus d'une image, on peut reconna&icirc;tre distinctement dans les zones maritimes diverses tonalit&eacute;s de gris qui donnent à penser qu'il pourrait y avoir là une relation de premier ou tout au moins de second ordre avec des structures sous-marines. Dans ces conditions des images par satellites devraient offrir un int&eacute;r&ecirc;t pour la morphologie marine.Afin de v&eacute;rifier cette possibilit&eacute;, dans la pr&eacute;sente &eacute;tude, on a compar&eacute; 27 images par satellites, tir&eacute;es d'un grand nombre de prises de vues, avec les cartes marines correspondantes et d'autres documents. En quelques points apparuent des concordances surprenantes entre certains tons de gris et des formes sous-marines connues, tandis qu'en beaucoup d'autres endroits on ne peut encore rien pr&eacute;ciser pour le moment. Avant tout, en l'&eacute;tat actuel des choses, on ne peut encore affirmer qu'il existe — et dans quelle mesure — des concordances d'ordre primaire ou secondaire.Les donn&eacute;es techniques n&eacute;cessaires pour l'appr&eacute;ciation des images par satellites en ce qui concerne les proc&eacute;d&eacute;s de prises de vue et de transmission, sont r&eacute;sum&eacute;es succinctement; elles sont trait&eacute;es de fa&ccedil;on plus d&eacute;taill&eacute;e ailleurs (voir bibliographie).Une discussion critique du problème de la profondeur de p&eacute;n&eacute;tration de la lumière dans l'eau, permet de supposer que dans la zone où p&eacute;nètre la lumière solaire, des profondeurs plus grandes que celles admises jusqu'alors sont &eacute;clair&eacute;es et aussi que de la «vue d'ensemble», de haute altitude, peuvent r&eacute;sulter des conditions optiques qui diffèrent de celles auxquelles nous sommes accoutum&eacute;s.Dans l'ensemble les r&eacute;sultats montrent que les informations à attendre de la m&eacute;thode, souffrent encore d'un insuffisance de moyens techniques et autres mais laisse entrevoir, en principe, de nouvelles contributions à l'oc&eacute;anographie.ckquote>  相似文献   

Records of cosmogenic radionuclides Be, Al and Cl in corals: First studies on coral erosion rates and potential of dating very old corals     

Devendra Lal  Christina D. Gallup  Loïc Vacher  Anthony J.T. Jull  Robert C. Speed  Amos Winter 《Geochimica et cosmochimica acta》2005,69(24):5717-5728

We present results of measurements of cosmogenic ¹⁰Be, ²⁶Al and ³⁶Cl, and the indigenous (intrinsic) concentrations of the stable elements Be, Al and Cl in 120-200 kyr old corals from Barbados and Puerto Rico. The concentration levels of these radionuclides in the corals lie in the range 10⁴ to 10⁸ atoms/g. A comparison of the measured nuclide concentrations with those expected to be produced in the corals by nuclear interactions of energetic cosmic radiation shows that (i) the radionuclides ²⁶Al and ³⁶Cl are derived from in situ cosmic ray interactions in the corals after their formation, but that (ii) the radionuclide ¹⁰Be owes its provenance in the coralline lattice primarily due to incorporation of dissolved beryllium in seawater in the lattice structure of the corals.  相似文献