Microthermometry and geochemistry of fluid inclusions from the Tennant Creek gold-copper deposits: implications for ore deposition and exploration   总被引：1，自引：0，他引：1  

Khin Zaw  D. L. Huston  R. R. Large  T. Mernagh  C. F. Hoffmann 《Mineralium Deposita》1994,29(3):288-300

Gold-copper-bismuth mineralization in the Tennant Creek goldfield of the Northern Territory occurs in pipe-like, ellipsoidal, or lensoidal lodes of magnetite ± hematite ironstones which are hosted in turbiditic sedimentary rocks of Proterozoic age. Fluid inclusion studies have revealed four major inclusion types in quartz associated with mineralized and barren ironstones at Ten nant Creek; (1) liquid-vapour inclusions with low liquid/vapour ratios (Type I), (2) liquid-vapour inclusions with high liquid/vapour ratios or high vapour/liquid ratios and characteristic dark bubbles (Type II), (3) liquid-vapour-halite inclusions (Type III), and (4) liquid-vapour inclusions with variable liquid/vapour ratios (Type V). Type I inclusions are present in the barren ironstones and the unmineralized portions of fertile ironstones, whereas Types II and III inclusions are recognized in fertile ironstones. Trails of Types II and III inclusions cut trails of Type I inclusions. Type I fluid inclusions have homogenization temperatures of 100° to 350 °C with a mode at 200° to 250 °C. Type II inclusions in mineralized ironstones (e.g. Juno, White Devil, Eldorado, TC8 and Gecko K-44 deposits) have homogenization temperatures of 250 °C to 600 °C with a mode of 350 °C. Type I fluid inclusions have a salinity range of 10 to 30 NaCl equiv. wt %. Salinity measurements on fluid inclusions in the mineralized zones gave a range of 10 to 50 NaCl equiv. wt % with a mode of 35 NaCl equiv. wt %. Fluid inclusion studies indicate that the Tennant Creek ironstones were formed from a relatively low temperature and moderately saline fluid, where as gold and copper mineralization was deposited from later hydrothermal fluids of higher temperature and salin ity. Gas analysis indicates the presence of N₂ and CO₂, with very minor CH₄ in Types II inclusions but no N₂ or CH₄ gases in Type I inclusions. Microprobe analysis of the fluid inclusion decrepitates indicates that the inclusions from Tennant Creek contain sodium and calcium as dominant cations and potassium in a subordinate amount. The high temperatures ( 350 °C), high salinities ( 35 NaCl equiv. wt. %) and cation composition of the Tennant Creek ore fluids suggest that the ore fluids were derived from upward migrating heated basinal brines, although contribution from a magmatic source cannot be ruled out. Close association of vapour-rich Type IIb and salt-rich Type III inclusions in the mineralized ironstones (e.g. Juno, White Devil, Eldorado, TC8 and Gecko K-44) indicates heterogeneous trapping of ore fluids. This heterogeneous trapping is interpreted to be due to unmixing (exsolution) of a gas-rich (e.g. N₂) fluid during the upward migration of the metal bearing brines and/or due to degassing caused by reaction of oxidized ore fluids and host ironstones. Fluid inclusion data have important implications regarding the deposition of gold in the ironstones, and may have application in discriminating fertile from barren ironstones.  相似文献   

Chromosomes of the siberian snow sheep, Ovis nivicola, and implications concerning the origin of amphiberingian wild sheep (subgenus Pachyceros)     

K.V. Korobitsyna  C.F. Nadler  N.N. Vorontsov  R.S. Hoffmann 《Quaternary Research》1974,4(3):235-245

The chromosomes of Ovis nivicola, described for the first time, exhibit 2n = 52, the lowest diploid number to be reported for wild sheep and goats. The new chromosomal data, together with a review of the fossil history of the genus, lead us to conclude that the bighorned wild sheep (subgenus Pachyceros) evolved their distinctive characteristics while isolated in the ice-free Beringian refugium, and then migrated southward into western North America when the glacial barriers melted, as first suggested by Cowan (1940).  相似文献   

Molecular parameters of maturation in the Toarcian shales,Paris Basin,France—III. Changes in aromatic steroid hydrocarbons     

A.S Mackenzie  C.F Hoffmann  J.R Maxwell 《Geochimica et cosmochimica acta》1981,45(8):1345-1355

Three series of monoaromatic steroid hydrocarbons (basepeak = m/z 239, 253 and 267) and four series of triaromatic steroid hydrocarbons (basepeak = m/z 217, 231, 245 and 259) have been recognised by computerised gas chromatography-mass spectrometry in a variety of samples of Lower Toarcian shales from the Paris Basin. An increase in the extent of aromatisation of the monoaromatic steroid hydrocarbons in the m/z 253 series (measured by the abundance of monoaromatic components relative to triaromatic components in the m/z 231 series) is observed with increasing maturity. Variations between reported maximum burial depth and extent of aromatisation are explicable partly in terms of new maximum burial depth information for some of the shales. The extent of carbon-carbon bond cracking in the side chains of the aromatic steroid hydrocarbons has only begun to be significant in certain of the deepest samples.  相似文献   

Greigite (Fe₃S₄): magnetic properties and first domain observations     

V. Hoffmann 《Physics of the Earth and Planetary Interiors》1992,70(3-4):288-301

Recently the ferrimagnetic iron sulphide greigite (Fe₃S₄) has been recognized as an important carrier of magnetic remanence in young sediments. New magnetic measurements and properties of this rare mineral are presented. Magnetic domain observations were made using the Bitter method and the magneto-optical Kerr effect. In most cases the domain structures observed are very complicated and their interpretation is rather difficult. The cause of this domain structure is very likely high magnetostriction. A first attempt to establish a relationship between grain size and domain state is made.  相似文献   

Magnetic force microscopy imaging of domain walls in magnetite     

W. Williams  V. Hoffmann  F. Heider  T. Goddenhenrich  C. Heiden 《Geophysical Journal International》1992,111(3):417-423

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Crystal chemistry and optics of bazzite from Furkabasistunnel (Switzerland)     

Th. Armbruster  E. Libowitzky  M. Auernhammer  P. Bauerhansl  Ch. Hoffmann  E. Irran  A. Kurka  H. Rosenstingl  L. Diamond 《Mineralogy and Petrology》1995,52(1-2):113-126

Summary The crystal structure of blue bazzite (space group P6/mcc, Z = 2, = 9.501(1),c = 9.178(1) Å) with the composition Be₃(Sc_1.25Fe³⁺ _0.43Mg_0.32Mn_0.03Al_0.02)_=2.05 Si₆O₁₈[Na_0.32(n H₂O)] was refined from X-ray single-crystal data with 422 unique reflections to R = 2.2%. The structure is of the beryl type with octahedra strongly compressed parallel to the c-axis. The octahedral Me-O distance in bazzite is 2.080 A compared to 1.904 Å in beryl. The flattening of octahedra leads to a larger a cell dimension in bazzite compared to beryl (9.209 A). Two-valent cations (mainly Mg) in octahedral coordination are charge balanced by Na at (0, 0, 0) in the structural channels. Polarized single-crystal IR-spectra recorded between 400 and 8000 cm^–1 indicate that H₂O in the structural channels is oriented with the H-H vector perpendicular to thec-axis. The IR-spectra show more absorption bands than known for type II H₂O in beryl thus the existence of more than one H₂O species or even OH-groups is very likely.Refractive indices of the same bazzite were measured using a spindle-stage and employing the wavelength-temperature variation method yielding n_o = 1.6279(3), n_e = 1.6066(5) for 589 nm at 25°C. The birefringence = 0.0213 is significantly larger than the one of near end-member beryl ( = 0.0047). This high birefringence of bazzite is related to the electronic polarizability of octahedral Sc and Fe which increase n_o at a stronger rate than n_e. Transition metals in bazzite are also responsible for a higher refractive index dispersion than found for beryl.

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Kristallchemie und optische eigenschaften des bazzits aus dem Furkabasistunnel

Zusammenfassung Die Kristallstruktur eines blauen Bazzits (Raumgruppe P6/mcc, Z = 2,a = 9.501(1),c = 9.178(1) Å) mit der Zusammensetzung Be₃(Sc_1.25Fe³⁺ _0.43Mg_0.32Mn_0.03Al_0.02)_2=2.05 Si₆)O₁₈[Na_0.32(n H₂O)] wurde von Röntgeneinkristalldaten mit 422 Reflexen zu R = 2.2% verfeinert. Die Struktur ist die des Berylltyps mit der Besonderheit, daß die Oktaeder entlang der c-Achse stark zusammengedrückt sind. Die oktaedrischen Me-O Abstände im Bazzit betragen 2.080 Å, im Gegensatz zu 1.904Å im Beryll. Die Stauchung der Oktaeder im Bazzit führt zu einer längeren a-Achse als im Beryll (9.209 Å). Zweiwertige Kationen (vor allem Mg) in oktaedrischer Koordination werden durch Na auf (0, 0, 0), in den strukturellen Kanalen, neutralisiert. Polarisierte Einkristall-IR-Spektren zwischen 400 and 8000 cm^–1 zeigen, daß H₂O Moleküle in den strukturellen Kanalen mit dem H-H Vektor senkrecht zur c-Achse orientiert sind. Die IR-Spektren weisen außerdem mehr Absorptionsbanden auf, als für den H₂O Typ II bekannt sind, sodaß entweder mehr als eine H₂O Spezies oder sogar OH-Gruppen sehr wahrscheinlich sind.Brechungsindizes am gleichen Bazzit wurden auf einem Spindeltisch mit der Wellenlängen-Temperatur Variationsmethode gemessen und ergaben n_o = 1.6279(3), n_e = 1.6066(5) bei 589 nm und 25 °C. Die Doppelbrechung A = 0.0210 ist deutlich höher als für einen nahezu Endgliedberyll (A = 0.0047). Diese hohe Doppelbrechung des Bazzits wird durch die elektronische Polarisierbarkeit von oktaedrischem Sc und Fe verursacht, die n_o starker ansteigen läßt als n_e. Übergangselemente im Bazzit sind auch für die höhere Dispersion der Brechungsindizes als im Beryll verantwortlich.

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The mid-infrared structure of the bipolar nebulae AFGL 915, AFGL 618, and AFGL 2688     

Joseph L. Hora  Lynne K. Deutsch  William F. Hoffmann  Giovanni G. Fazio 《Astrophysics and Space Science》1995,224(1-2):361-364

We have obtained near diffraction-limited images of three bipolar PPN at UKIRT in October, 1993: AFGL 915 (the Red Rectangle), AFGL 618, and AFGL 2688 (the Egg Nebula). Images were taken at unidentified infrared (UIR) emission feature wavelengths and at several continuum wavelengths in the 10 and 20µm atmospheric windows. In all three PPN the emission is dominated by a central point source with fainter emission extending for several arcsec. In AFGL 2688, the mid-IR emission is extended in the same direction as the main optical lobes. In AFGL 915, the UIR feature emission is spatially separated from the central source. The spikes that have been observed at 2µm and give the nebula its rectangular appearance are also visible at 10µm.  相似文献   

Historical ecology of riverine fish in Europe     

Gertrud Haidvogl  Richard Hoffmann  Didier Pont  Mathias Jungwirth  Verena Winiwarter 《Aquatic Sciences - Research Across Boundaries》2015,77(3):315-324

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Towards radiocarbon calibration beyond 28 ka using speleothems from the Bahamas     

Dirk L. Hoffmann  J. Warren Beck  David A. Richards  Peter L. Smart  Joy S. Singarayer  Tricia Ketchmark  Chris J. Hawkesworth 《Earth and Planetary Science Letters》2010,289(1-2):1-10

We present a new speleothem record of atmospheric Δ¹⁴C between 28 and 44 ka that offers considerable promise for resolving some of the uncertainty associated with existing radiocarbon calibration curves for this time period. The record is based on a comprehensive suite of AMS ¹⁴C ages, using new low-blank protocols, and U–Th ages using high precision MC-ICPMS procedures. Atmospheric Δ¹⁴C was calculated by correcting ¹⁴C ages with a constant dead carbon fraction (DCF) of 22.7 ± 5.9%, based on a comparison of stalagmite ¹⁴C ages with the IntCal04 (Reimer et al., 2004) calibration curve between 15 and 11 ka. The new Δ¹⁴C speleothem record shows similar structure and amplitude to that derived from Cariaco Basin foraminifera (Hughen et al., 2004, 2006), and the match is further improved if the latter is tied to the most recent Greenland ice core chronology (Svensson et al., 2008). These data are however in conflict with a previously published ¹⁴C data set for a stalagmite record from the Bahamas — GB-89-24-1 (Beck et al., 2001), which likely suffered from ¹⁴C analytical blank subtraction issues in the older part of the record. The new Bahamas speleothem ?¹⁴C data do not show the extreme shifts between 44 and 40 ka reported in the previous study (Beck et al., 2001). Causes for the observed structure in derived atmospheric Δ¹⁴C variation based on the new speleothem data are investigated with a suite of simulations using an earth system model of intermediate complexity. Data-model comparison indicates that major fluctuations in atmospheric ?¹⁴C during marine isotope stage 3 is primarily a function of changes in geomagnetic field intensity, although ocean–atmosphere system reorganisation also played a supporting role.  相似文献   

北京石景山工业区附近一个污染土壤剖面的磁学研究   总被引：24，自引：2，他引：22       下载免费PDF全文

沈明洁  胡守云  U.Blaha  闫海涛  W.R 《地球物理学报》2006,49(6):1665-1673

对北京西郊石景山工业区附近的土壤剖面进行环境磁学研究,结合粒度、金属元素分析、磁学指标测试和多元统计分析,发现磁参数(χ,ARM,SIRM)与重金属元素(Mn,Cu,Fe,Pb,Zn,Al,Sr)含量呈同步垂向变化趋势.来源于工业区附近工业生产排放(钢铁厂、发电厂、水泥厂)的污染物是土壤剖面上部(0～3 cm)磁性和金属含量增强的主要原因,由富集在细粉砂和中粉砂的多畴磁铁矿主导了样品的磁性特征.3～10 cm重金属含量逐渐下降,土壤的磁性特征与上层相似,但磁性矿物含量降低,属于剖面中的迁移过渡阶段.10 cm以下,土壤基本未受到污染,磁性矿物和重金属含量都低,磁性颗粒大小变化稳定,基本代表了该地区土壤的自然背景.指标聚类和相关分析表明,土壤磁参数与重金属元素含量显著相关.结合模糊聚类分析,磁参数可用于追踪、识别工业污染物质在土壤剖面中的富集、迁移状态,揭示不同深度土壤的污染程度.  相似文献