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31.
One of the key-principles of the iron-sulphur world theory is to bring organic molecules close enough to interact with each
other, using the surface of pyrite as a substrate in a hydrothermal setting. The present paper explores the relationship of
pyrite and organic matter in a hydrothermal setting from the geological record; in hydrothermal calcite veins from Carboniferous
limestones in central Ireland. Here, the organic matter is accumulated as coatings around, and through, pyrite grains. Most
of the pyrite grains are euhedral-subhedral crystals, ranging in size from ca 0.1-0.5 mm in diameter, and they are scattered
throughout the matrix of the vein calcite. The organic matter was deposited from a hydrothermal fluid at a temperature of
at least 200°C, and gives a Raman signature of disordered carbon. This study points to an example from a hydrothermal setting
in the geological record, demonstrating that pyrite can have a high potential for the concentration and accumulation of organic
materials. 相似文献
32.
On the utility of identification schemes for digital earth science data: an assessment and recommendations 总被引:1,自引:1,他引:0
Ruth E. Duerr Robert R. Downs Curt Tilmes Bruce Barkstrom W. Christopher Lenhardt Joseph Glassy Luis E. Bermudez Peter Slaughter 《Earth Science Informatics》2011,4(3):139-160
In recent years, a number of data identification technologies have been developed which purport to permanently identify digital
objects. In this paper, nine technologies and systems for assigning persistent identifiers are assessed for their applicability
to Earth science data (ARKs, DOIs, XRIs, Handles, LSIDs, OIDs, PURLs, URIs/URNs/URLs, and UUIDs). The evaluation used four
use cases that focused on the suitability of each scheme to provide Unique Identifiers for Earth science data objects, to
provide Unique Locators for the objects, to serve as Citable Locators, and to uniquely identify the scientific contents of
data objects if the data were reformatted. Of all the identifier schemes assessed, the one that most closely meets all of
the requirements for an Unique Identifier is the UUID scheme. Any of the URL/URI/IRI-based identifier schemes assessed could
be used for Unique Locators. Since there are currently no strong market leaders to help make the choice among them, the decision
must be based on secondary criteria. While most publications now allow the use of URLs in citations, so that all of the URL/URI/IRI
based identification schemes discussed in this paper could potentially be used as a Citable Locator, DOIs are the identification
scheme currently adopted by most commercial publishers. None of the identifier schemes assessed here even minimally address
identification of scientifically identical numerical data sets under reformatting. 相似文献
33.
Abundant iron oxide deposits including banded iron formations, apatite iron oxide ores, and enigmatic marble/skarn-hosted magnetite deposits occur in the Palaeoproterozoic Bergslagen region, southern Sweden. During the last 100 years, the latter deposit class has been interpreted as contact metasomatic skarn deposits, metamorphosed iron formations, or metamorphosed carbonate replacement deposits. Their origin is still incompletely understood. At the Smältarmossen mine, magnetite was mined from a ca. 50-m-thick calcic skarn zone at the contact between rhyolite and stratigraphically overlying limestone. A syn-volcanic dacite porphyry which intruded the footwall has numerous apophyses that extend into the mineralized zone. Whole-rock lithogeochemical and mineral chemical analyses combined with textural analysis suggests that the skarns formed by veining and replacement of the dacite porphyry and rhyolite. These rocks were added substantial Ca and Fe, minor Mg, Mn, and LREE, as well as trace Co, Sn, U, As, and Sr. In contrast, massive magnetite formed by pervasive replacement of limestone. Tectonic fabrics in magnetite and skarn are consistent with ore formation before or early during Svecokarelian ductile deformation. Whereas a syngenetic–exhalative model has previously been suggested, our results are more compatible with magnetite formation at ca. 1.89 Ga in a contact metasomatic skarn setting associated with the dacite porphyry. 相似文献
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35.
Colin Neal Nils Christophersen Richard Neale Christopher J. Smith Paul G. Whitehead Brian Reynolds 《水文研究》1988,2(2):155-165
Variations in the concentration of Cl in rainfall and stream runoff are presented for two catchments in the Hafren forest of mid-Wales, Great Britain. Despite the large fluctuations in rainfall concentrations, Cl in the streamwater remains relatively constant. Using the two-reservoir Birkenes model, an attempt was made to simulate observed Cl in streamwater. The original model was unable to reproduce the observations and several modifications are suggested to provide better simulations. The resulting model is not the only one capable of reproducing the observations; other hydrochemical models will most probably also achieve this although emphasis will in each case be placed on different aspects. In this paper, it is suggested that the stochastic properties of water movement and chemical processes can account for the streamwater chemistry responses observed. On the catchment scale these processes will lead to an apparently deterministic behaviour that may well be described by simple relationships. 相似文献
36.
Nils Aall Barricelli 《Earth, Moon, and Planets》1988,43(3):307-309
Phobos' proximity to the Roche limit, and some of its consequences deserving attention by the Phobos' mission, are the subject of this note. 相似文献
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The apparent ionization constants for silicic acid, k1 and k2, and the ionic product of water, kw, have been determined in 0.05, 0.1, 0.2, 0.4 and 2.0 M Na(CI) media at 25°C. The medium dependence of these constants was found to fit equations of the form where K1 is the ionization constant in pure water, αi and bi are parameters of which bi has been adjusted to present data. The following results were obtained (αi, bi): pK1 = 9.84, (1.022, ?0.11); pK2 = 13.43, (2.044, ?0.20); and pKw = 14.01 (1.022, ?0.22). ki values are collected in Tables I and II. Attempts have been made to explain the medium dependence of k1 and k2 with weak sodium silicate complexing according to the equilibria giving k11 = 0.37M?1 and k21= 3.0M?1. However, these weak interactions cannot be interpreted unambiguously from potentiometric data at different 1-levels. Probably the medium dependence could equally well be expressed by variations in the activity coefficients.The measurements were performed as potentiometric titrations using a hydrogen electrode. The average number of OH- reacted per Si(OH)4, Z, has been varied within the limits 0 ? Z ? 1.1 and B1, the total concentration of Si(OH)4, between 0.001 M and 0.008 M. k1 was evaluated from experimental data with B ? 0.003 M, and k2 with B ? 0.008 M and Z ? 0.95. 相似文献