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Stratiform Cu-Pb-Zn (-Au-Ag) mineralization associated with black carbonaceous schists and acid metatuffs is restricted to distinct horizons within the Cretaceous sequence of the Diahot region. The sulphides occur in sharply bounded lenses which show varying degrees of compositional banding conformable with the foliation of the country schists. The deposits are sedimentary-exhalative of the Rio Tinto-type and have been modified by mid-Tertiary high-pressure metamorphism (lawsonite-albite and glaucophanitic greenschist facies). The ores are not strongly deformed by the metamorphism and sedimentary structures, pyrite framboids and atoll structures are preserved in some deposits. With increasing metamorphic grade sphalerite becomes more iron-rich, pyrrhotite becomes more abundant, and the sulphides show a general increase in grain-size which parallels that of the silicates in the enclosing rocks. In the more highly metamorphosed deposits the sulphide associations are retrograde assemblages. There is no evidence of large-scale metamorphic remobilization of sulphides. No differences were observed in either the sulphide assemblages or in the composition of the sulphides to indicate that the metamorphism was of the high pressure rather than the low pressure type. 相似文献
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The Great Barrier Island subvolcanic silver-gold deposits comprise a number of essentially east striking, quartz filled, mineralized fissures, which transect andesitic volcanics and an unconformably overlying, bedded sinter deposit of upper Tertiary to Quaternary age. Wall rock alteration is characterized by a propylitic assemblage in the least altered andesite, with argillic assemblages and silicification developed in close proximity to the veins. Some twentyfive hypogene and supergene ore minerals have been recognized, of which pyrite is the most common and finely disseminated pyrargyrite constitutes the main source of silver. The mineral assemblage is dominantly hypogene with minor supergene alteration occurring at surface exposures, and includes mainly sulfides, selenides and native metals. Fineness of electrum derived from two electron microprobe analyses is approximately 500, while total silver to gold ratio from a number of bulk chemical analyses is 30:1. Maximum depth of deposition is estimated to be in the order of 500 m and for some surface exposures 100 m. The mineralization is regarded as subvolcanic and along with other hydrothermal fissure deposits of Hauraki Province is considered to be of Pliocene-Pleistocene age, and hence is believed to be associated with the late phase extrusions and intrusions of acid magma in the volcanic belt. 相似文献
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An equivalent-boundary method for the shell analysis of buried pipelines under fault movement 总被引：2，自引：0，他引：2
Introduction The history of research work on the response of buried pipeline under the fault movement hasbeen about 30 years. Several simplified design methods have been proposed to obtain the maxi-mum stress or strain in pipe. These methods include the theoretical method and the finite elementmethod (FEM). In the theoretical method, the pipe is usually modeled as a cable (Newmark, Hall1975; Kennedy, et al, 1977) or a beam (Wang, Wang, 1995; LIU, ZHANG, 2002). These theoreti-cal me… 相似文献
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Associate-Professor K. A. Rodgers Dr. H. W. Kobe Dr. C. W. Childs 《Mineralogy and Petrology》1993,47(2-4):193-208
Summary Vivianite from Catavi Mine, Llallagua, Bolivia, has a near ideal composition with traces of Mg, Zn and Mn. Total rare-earth elements are < 1,gmg/g. Mössbauer spectroscopy shows FeIII/(FeII + FeIII) is approximately 0.04.a = 10.030Å,b = 13.434Å,c = 4.714Å, = 102.73dg. The middle-infrared powder spectrum shows H2O-related bands at 3490, 3290, 3130 cm–1 (stretch), 1618 cm–1 (bend), 825 cm–1 (rock), and at 665 cm–1 a possible M-OH2 twist. P04 bands occur at 1045-940 cm–1 (stretch) and 570-450 cm–1 (bend). Corresponding laser Raman microprobe bands occur at 1051 (ms), 986 (m), 948 (vs), 867 (mw), 828 (w), 568, 532, 453 (m), 442 (mw). Weak Raman bands at about 342, 303, 270 (w), 235 (ms), 227 (sh, ms), 196 (ms), 187 (sh, m), 162 (mw), and 126 (m) may arise from lattice vibrations. Differential thermal responses include a major endotherm from 115–235°C with a shoulder at 170°C and a maximum at 210°C resulting from loss of structural water combined with oxidation of Fe2+, and two small exotherms with maxima at 605 and 780°C related to structural transformations.
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Charakterisierung des Vivianits von Catavi, Llallagua, Bolivien
Zusammenfassung Vivianit von der Catavi Mine, Llallagua, Bolivien zeigt annähernd ideale Zusammensetzung mit Spuren von Mg, Zn und Mn. Der gesamte Gehalt an seltenen EvolElementen ist < 1 ppm. Die Mössbauer Spektroskopie liefert ein Fe3+/(Fe2+ + Fe3+) Verhältnis von ungefähr 0.04.a = 10.030,b = 13.434,c = 4.714 Å, = 102.73°. Das Infrarot-Pulverspektrum zeigt dem H20 zuzuordnende Banden bei 3490, 3290, 3130 cm–1 (Streckschwingungen), 1618 cm–1 (Deformationsschwingung), 825 cm–1 (Schaukelschwingung) und eine mögliche M-OH2 Torsionsschwingung bei 665 cm–1. PO4 Banden liegen bei 1045-940 cm–1 (Streckschwingung) und 570-450 cm–1 (Deformations-schwingung). Entsprechende Banden der Laser Raman Mikrosonde liegen bei 1051 (mst), 986 (m), 948 (sst) 867 (mschw), 828 (schw), 568, 532, 453 (m), 442 (mschw). Raman Banden bei etwa 342, 303, 270 (schw), 235 (mst), 227 (Schulter, mst), 196 (mst), 187 (Schulter, m), 162 (mschw) und 126 (m) können auf Gitterschwingungen zurückgeführt werden. Differential-thermoanalytische Untersuchungen zeigen einen endothermen Bereich von 115–235°C mit einer Schulter bei 170 und einem Maximum bei 210°C, was auf den Verlust von strukturellem Wasser, das an eine Oxidation des Fe2+ gebunden ist, zurückzuführen ist; zwei auf strukturelle Transformationen zurückzuführende exotherme Maxima liegen bei 605 und 780°C.
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