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1.
We carried out experiments on crystallization of Fe-containing melts FeS2Ag0.1–0.1xAu0.1x (x = 0.05, 0.2, 0.4, and 0.8) with Ag/Au weight ratios from 10 to 0.1. Mixtures prepared from elements in corresponding proportions were heated in evacuated quartz ampoules to 1050 ºC and kept at this temperature for 12 h; then they were cooled to 150 ºC, annealed for 30 days, and cooled to room temperature. The solid-phase products were studied by optical and electron microscopy and X-ray spectroscopy. The crystallization products were mainly from iron sulfides: monoclinic pyrrhotite (Fe0.47S0.53 or Fe7S8) and pyrite (Fe0.99S2.01). Gold–silver sulfides (low-temperature modifications) are present in all synthesized samples. Depending on Ag/Au, the following sulfides are produced: acanthite (Ag/Au = 10), solid solutions Ag2–xAuxS (Ag/Au = 10, 2), uytenbogaardtite (Ag/Au = 2, 0.75), and petrovskaite (Ag/Au = 0.75, 0.12). They contain iron impurities (up to 3.3 wt.%). Xenomorphic micro- (<1–5 μm) and macrograins (5–50 μm) of Au–Ag sulfides are localized in pyrite or between the grains of pyrite and pyrrhotite. High-fineness gold was detected in the samples with initial ratio Ag/Au ≤ 2. It is present as fine and large rounded microinclusions or as intergrowths with Au–Ag sulfides in pyrite or, more seldom, at the boundary of pyrite and pyrrhotite grains. This gold contains up to 5.7 wt.% Fe. Based on the sample textures and phase relations, a sequence of their crystallization was determined. At ~1050 ºC, there are probably iron sulfide melt L1 (Fe,S ? Ag,Au), gold–silver sulfide melt L2 (Au,Ag,S ? Fe), and liquid sulfur LS. On cooling, melt L1 produces pyrrhotite; further cooling leads to the crystallization of high-fineness gold (macrograins from L1 and micrograins from L2) and Au–Ag sulfides (micrograins from L1 and macrograins from L2). Pyrite crystallizes after gold–silver sulfides by the peritectic reaction FeS + LS = FeS2 at ~743 ºC. Elemental sulfur is the last to crystallize. Gold–silver sulfides are stable and dominate over native gold and silver, especially in pyrite-containing ores with high Ag/Au ratios.  相似文献   

2.
1INTRODUCTION ORGANICALLY BOUNDSULFURCOMPOUNDSWEREPREVI OUSLYDETECTEDINTHEKUPFERSCHIEFER(P櫣TTMANNAND GO EL,1990;ROSPONDEKETAL.,1994).P櫣TTMANN ANDGO EL(1990)INVESTIGATEDTHEEXTRACTABLEORGANIC MATTERINTHEKUPFERSCHIEFERFROMTHENORTH SUDETIC SYNCLINEANDPROPOS…  相似文献   

3.
Microorganisms in the lateritic profiles of the Lianxian gold deposit in Guangdong were cultured, isolated and identified. The microorganisms include bacteria such as Bacillus, Enterobacter, Pseudomonas, Lactobacillus, Actinetobacter, Aeromona, Listeria, Agrobacteriura, Cotyttebacteriurn, and Moraxella, fungi such as Penicillium, Alter naria, Cladosporium, Saccharcornyces, Mucor, and the chemoautotrophic Thiobacillu.~. It is shown in a leaching experiment that the microorganisms can accelerate the leaching of Cu, Cd, Zn, and that the G- bacteria are most efficient for leaching Cu, Zn and the G^ bacteria are better for leaching Cd.  相似文献   

4.
An ‘autochthon’ model for the tectonic development of Timor is suggested, based on observations of Palaeozoic‐Mesozoic relationships from a broad area of central East Timor, including:

  1. (a) ‘allochthonous’ Permian rocks unconformable on metamorphic rocks

  2. (b) ‘allochthonous’ Permian units interbedded with ‘autochthonous’ Permian units, and

  3. (c) ‘autochthonous’ Triassic sediments stratigraphically overlying ‘allochthonous’ Permian rocks.

The model is supported by recent modifications in palaeogeographic interpretations for the Permian of north Australia (e.g. Powell, 1976; Thomas, 1976). Our observations support and extend the earlier suggestions of Grady (1975), and the resulting model is in contrast with some of the hypotheses of Audley‐Charles and his associates (as, most recently, Barber et al., 1977), Fitch & Hamilton (1974), Hamilton (1973, 1976), and Crostella (1976).

Our model involves no essentially allochthonous pre‐Cainozoic material in Timor. The Permian to Cretaceous units are envisaged as developing on the continental margin which was dominantly inactive, but affected to some extent by Late Jurassic rifting activity. Following the Pliocene collision with the Inner Banda Arc, uplift along the collision zone would have caused gravity gliding towards the south. Thus, surficial olistostrome deposits, originally from the island arc, could have eventually moved to the northern slopes of the Timor Trough, while at depth, reverse faulting could have developed as a result of gravity gliding.

We maintain that previous postulates of a pervasive, strongly imbricate structure for Timor, lack adequate substantiation in the literature. Furthermore, accounts of the tectonic development of Timor, involving large scale translation on low angle faults, are even less well substantiated.  相似文献   

5.
156 samples of naturally‐occurring molybdenite from 87 localities in Australia have been examined to determine the distribution of the hexagonal (2H1) and rhombohedral (3R) polytypes. 90% of the specimens examined are 2H1 polytypes, the remainder being 3R and mixtures of 2H1 and 3R polytypes. The 3R and mixed polytypes are more abundant in porphyry copper deposits or as disseminations, in veins, and in garnet‐quartz pipes in granite. 2H1 polytypes are the sole modification observed in pegmatites, quart‐pegmatite pipes, simple quartz veins, and skarns.

The highest average concentrations of rhenium are in molybdenite from porphyry copper deposits, quartz porphyry pipes, skarn deposits, garnet‐quartz pipes, and pegmatites. Low concentrations occur in molybdenite which is disseminated or in quartz veins in granite and in quartz or pegmatitic pipes. Molybdenites in which the 2H1 polytype is dominant have a lower average rhenium content than those with dominant 3R polytype.  相似文献   

6.
The ores of the Yata gold mine in China are rich in arsenic and antimony, so the exploitation of this mine may also lead to the release of As and Sb to adjacent environments, such as stream water, stream sediment, soil, plants, and crops. To understand the environmental impact of mine tailings, samples of water, sediment, soil, plant and crop were collected and analyzed. In summer of 2005, the tailings dump was seriously flushed by a heavy flood, and the mine waste was transported far away. Samples were collected in December of 2004 and January of 2006, respectively, and the impact of the flood on the release of toxic elements was evaluated. The result shows that the Yata creek, which drains the mining area, was severely contaminated by As and Sb. The dissolved As and Sb in water are 86-1140 μg/L and 65-370 μg/L, the particulate As and Sb are 38-2100 μg/L and 25-420 μg/L, whereas As and Sb in the sediment are 190-760 μg/g and 69-210 μg/g, respectively. In water environment, As and Sb show a similar feature to SO4^2- since As and Sb exist dominantly as anions--H2AsO4^-, HAsO4^2- and SbO3^-. In contrast to Fe, Cu, Pb, Zn, which migrate mostly in particulate form, As and Sb tend to transport in dissolved form.  相似文献   

7.
Most gold deposits in intrusive rocks were formed as a result of reworking processes. The intrusive rocks containing gold deposits and consisting of ultramafic-mafic, intermediateacid and alkaline rocks of the Archean, Proterozoic, Caledonian, Hercynian and Yenshanian periods occur in cratons, activated zones of cratons and fold belts. Among them, ultramaficmafic rocks, diorite, alkaline rocks, and anorthosite are products of remelting in the mantle or mantle-crust or mantle with crustal contamination. However, auriferous intermediate-acid rocks are products of metasomatic-remelting in auriferous volcanic rocks or auriferous volcanosedimentary rocks in the deep crust.  相似文献   

8.
The Duolanasayi gold deposit, 60 km NW of Habahe County, Xinjiang Uygur Autonomous Region, is a mid-large-scale gold deposit controlled by brittle-ductile shearing, and superimposed by albitite veins and late-stage magma hydrothermal solutions. There are four types of pyrite, which are contained in the light metamorphosed rocks (limestone, siltstone), altered-mineralized rocks (chlorite-schist, altered albite-granite, mineralized phyllite), quartz veins and carbonatite veinlets. The pyrite is the most common ore mineral. The Au-barren pyrite is present mainly in a simple form and gold-bearing pyrite is present mainly in a composite form. From the top downwards, the pyrite varies in crystal form from {100} and {210} {100} to {210} {100} {111} to {100} {111}. Geochemical studies indicate that the molecular contents of pyrite range from Fe1.057S2 to Fe0.941S2. Gold positively correlates with Mn, Sr, Zn, Te, Pb, Ba and Ag. There are four groups of trace elements: Fe-Cu-Sr-Ag, Au-Te-Co, As-Pb-Zn and Mn-V-Ti-Ba-Ni-Cr in pyrite. The REE characteristics show that the total amount of REE (ΣREE) ranges from 32.35×10 -6 to 132.18×10 -6; LREE/HREE, 4.466-9.142; (La/Yb)N, 3.719-11.133; (Eu/Sm)N, 0.553-1.656; (Sm/Nd)N, 0.602-0.717; La/Yb, 6.26-18.75; δEu, 0.628-2.309; δCe, 0.308-0.816. Sulfur isotopic compositions (δ 34S=-2.46‰--7.02‰) suggest that the sulfur associated with gold mineralization was derived from the upper mantle or lower crust.  相似文献   

9.
The Toolebuc Formation, which is a potentially important source of oil shale in the Eromanga Basin of NW Qld, exhibits a marked gamma‐ray response that has long beeen used as a stratigraphic marker. At Julia Creek, a large area of the Formation contains low‐grade oil shale that is accessible to mining. Detailed investigation, by gamma‐ray spectrometry and neutron activation analysis, of drill core samples from this deposit and from the type section of the Toolebuc Formation at Boulia (BMR Boulia 3A stratigraphic drill hole) show that the Toolebuc gamma‐ray anomaly in the northern Eromanga Basin is due to the presence of uranium. Analyses for organic carbon and phosphorus show that the uranium is associated primarily with organic matter in the oil shales and with phosphatic skeletal fish debris in the accompanying coquinites.

Drill core samples from Tibooburra, N.S.W. were also analysed (BMR Urisino‐1 stratigraphic drill hole) to investigate whether the gamma‐ray anomalies observed in the Bulloo Embayment on the southern margin of the Eromanga Basin (possibly correlative with the Toolebuc Formation) might also be indicative of oil shale. The results show that the much weaker anomaly at this locality is due principally to potassium and reflects the presence of an argillaceous siltstone within glauconitic sandstones.  相似文献   

10.
The Longquanzhan gold deposit hosted in granitic cataclasites with mylontization of the foot wall of the main Yishui-Tangtou fault. 3He/4He ratios in fluid inclusions range from 0. 14 to 0. 24 R/Ra,close to those of the crust-source helium. 40Ar/36Ar ratios were measured to be 289-1811, slightly higher than those of atmospheric argon. The results of analysis of helium and argon isotopes suggested that ore-forming fluids were derived chiefly from the crust. The δ18O values of fluid inclusions from vein quartz range from -1.78‰ to 4.07‰, and the δD values of the fluid inclusions vary between -74‰ and -77‰. The hydrogen and oxygen isotope data indicated that the ore-forming fluid for the Longquanzhan gold deposit had mixed with meteoric water in the process of mineralization. This is consistent with the conclusion from the helium and argon isotope data.  相似文献   

11.
Two epithermal gold deposits (Kartaldağ and Madendağ) located in NW Turkey have been characterized through the detailed examinations involving geologic, mineralogical, fluid inclusion, stable isotope, whole-rock geochemistry, and geochronology data.The Kartaldağ deposit (0.01–17.65 ppm Au), hosted by Eocene dacite porphyry, is associated with four main alteration types with characteristic assemblage of: i) chlorite/smectite–illite ± kaolinite, ii) quartz–kaolinite, iii) quartz–alunite–pyrophyllite, iv) quartz–pyrite, the last being characterized by three distinct quartz generations comprising massive/vuggy (early), fine–medium grained, vug-lining (early), and banded, colloform, comb (late) textures. Observed sulfide minerals are pyrite, covellite, and sphalerite. Oxygen and sulfur isotope analyses, performed on quartz (δ18O(quartz): 7.93 to 8.95‰ and calculated δ18O(H2O): − 7.95 to 1.49‰) and pyrite (δ34S(pyrite): − 4.8‰ and calculated δ34S(H2S): − 6.08 to − 7.20‰) separates, suggest a meteoric water source for water in the hydrothermal fluid, and an igneous source for the sulfur dissolved in ore-related fluids. Microthermometric analyses of primary fluid inclusion assemblages performed on quartz (late quartz generation) yield temperatures (Th) dominantly in the range of 245–285 °C, and generally low salinity values at 0 to 1.7 wt.% NaCl eq. Based on the quartz textures and the associated base metal concentrations, along with fluid inclusion petrography, the early vug-lining quartz is considered to have been associated with the mineralization possibly through a boiling and a late mixing process at > 285 °C.The Madendağ deposit (0.27–20.60 ppm Au), hosted by Paleozoic mica schists, is associated with two main alteration types: sericite–illite–kaolinite, and quartz–pyrite dominated by two distinct quartz generations i) early colloform, comb and banded quartz and ii) late quartz, forming the cement in hydrothermal breccia. Whereas oxygen isotope analyses of quartz (δ18O(quartz): 9.55 to 18.19‰ and calculated δ18O(H2O): − 2.97 to 5.54‰) suggest varying proportions of meteoric and magmatic sources for the ore bearing fluid, sulfur isotope ratios (δ34S(pyrite): − 2.2‰ and calculated δ34S(H2S): (− 3.63) to (− 3.75) ‰) point to an essentially magmatic source for sulfur with or without contribution from sedimentary sources. Microthermometric analysis carried out on primary fluid inclusion populations of a brecciated sample (early quartz), give a temperature (Th) range of 235–255 °C and 0.0 to 0.7 wt.% NaCl eq. salinity. Based on the textural relationship, base metal and high gold contents, the ore precipitation stage is associated with late stage quartz formation via a possible boiling process.The presence of alunite, pyrophyllite and kaolinite, vuggy quartz and covellite suggest a high-sulfidation type of epithermal deposit for Kartaldağ. On the other hand, Madendağ is identified as an adularia-sericite type owing to the presence of significant sericite, neutral pH clays (mostly illite, chlorite/smectite, and kaolinite), low temperature quartz textures (e.g., colloform, comb, and banded quartz), and limited sulfide minerals.Given the geographical proximity of Kartaldağ and Madendağ deposits, the similar temperature and salinity ranges obtained from their fluid inclusions, and the similar ages of igneous rocks in both deposits (Kartaldağ: 40.80 ± 0.36 to 42.19 ± 0.45 Ma, Madendağ: 43.34 ± 0.85 Ma) the mineralizing systems in both deposits are considered to be genetically related.  相似文献   

12.
The main task of this study was to reveal geochemical and distinctive features of gold–quartz vein ores of deposits in granitoid intrusive bodies and in terrigenous black-schist masses of the Yana-Kolyma folded belt. The results obtained point to the significant role of metamorphism of the enclosing terrigenous carbonaceous masses in ore formation of both types of deposits. The established facts are not contradictory to the metamorphic–magmagene model of the formation of gold deposits in the Yana–Kolyma belt. The geochemical similarity of both types of deposits shows that these are products of the same orogenic system, which confirms the validity of combining these deposits to form a unified gold–quartz formation.  相似文献   

13.

40Ar‐39Ar age spectra on minerals from granitic, metamorphic and hydrothermal rocks confirm that the Early Proterozoic Tennant Creek Block was affected by two thermal events during its evolution. Although extensive alteration of biotite and feldspar within the granites precludes the direct determination of their cooling history, 40Ar‐39Ar analyses for hydrothermal muscovite from several nearby gold‐copper deposits indicate that regional cooling to below ～ 300°C was not prolonged. Flat, uniform muscovite age spectra were obtained from gold deposits east of the Tennant Creek town site and indicate a minimum age of 1825–1830 Ma for their formation. These ages are within error of those for the felsic volcanism of the Flynn Subgroup, and a genetic relationship between the two may exist. Samples from gold deposits elsewhere in the area indicate disturbance of the K‐Ar isotope system. The second thermal event to affect the region occurred at around 1700 Ma, and is confirmed by the 40Ar‐39Ar muscovite ages for the ‘Warrego’ granite (1677 ± 4 Ma) and for the metamorphism of the Wundirgi Formation (1696 ± 4 Ma).  相似文献   

14.
Bindheimite has been identified in specimens from the Lvov Lease, N.W. Queensland. Chemical, microscopic and X‐ray data are given for the mineral which was found to possess a cubic lattice with a unit cell dimension of 10–427 A.  相似文献   

15.
A detailed Rb‐Sr total‐rock and mineral and U‐Pb zircon study has been made on suites of Proterozoic silicic volcanic rocks and granitic intrusions, from near Mt Isa, northwest Queensland. Stratigraphically consistent U‐Pb zircon ages within the basement igneous succession show that the oldest recognized crustal development was the outpouring of acid volcanics (Leichhardt Metamorphics) 1865 ± 3 m.y. ago, which are intruded by coeval, epizonal granites and granodiorites (Kalkadoon Granite) whose pooled U‐Pb age is 1862 +27 ‐21 m.y. A younger rhyolitic suite (Argylla Formation) within the basement succession has an age of 1777 ± 7 m.y., and a third acid volcanic unit (Carters Bore Rhyolite), much higher again in the sequence, crystallized 1678 ± 1 m.y. ago.

All of these rocks are altered in various degrees by low‐grade metamorphic events, and in at least one area, these events were accompanied by, and can be partly related to, emplacement of a syntectonic, foliated granitic batholith (Wonga Granite) between 1670 and 1625 m.y. ago. Rocks that significantly predate this earliest recognized metamorphism, have had their primary Rb‐Sr total‐rock systematics profoundly disturbed, as evidenced by 10 to 15% lowering of most Rb‐Sr isochron ages, and a general grouping of many of the lowered ages (some of which are in conflict with unequivocal geological relationships) within the 1600–1700 m.y. interval. Such isochrons possess anomalously high initial 87Sr/86Sr ratios, and some have a slightly curved array of isotopic data points. Disturbance of the Rb‐Sr total‐rock ages is attributed primarily to mild hydrothermal leaching, which resulted in the loss of Sr (relatively enriched in 87Sr in the Sr‐poor (high Rb/Sr) rocks as compared with the Sr‐rich rocks).  相似文献   

16.
With increasing intensity of metamorphism, and particularly metasomatism, it becomes more and more difficult to separate amphibolites in North‐western Queensland into ortho‐ and para‐amphibolites, and a stage is reached at which the two are indistinguishable. Field evidence, carefully sought, has enabled the origin of some apparently identical rocks to be determined, and laboratory methods were applied to these rocks to see if grounds for the separation of amphibolites of unknown origin could be determined. None of the six methods tried — mineralogy (including feldspar twinning), chemical analysis (including TiO2 content), spectrography, rock magnetism — proved to be as successful as the field method in distinguishing the two rock groups; some methods used with apparent success elsewhere, such as feldspar twinning or chemical analyses, are found to be unsuccessful here, which suggests that though the problem is world‐wide, solutions are only of local validity.  相似文献   

17.
The breccia-hosted epithermal gold–silver deposit of Chah Zard is located within a high-K, calc-alkaline andesitic to rhyolitic volcanic complex in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA), west central Iran. The total measured resource for Chah Zard is ∼2.5 million tonnes of ore at 12.7 g/t Ag and 1.7 g/t Au (28.6 t Ag, 3.8 t Au), making it one of the largest epithermal gold deposits in Iran. Magmatic and hydrothermal activity was associated with local extensional tectonics in a strike-slip regime formed in transtensional structures of the Dehshir-Baft strike-slip fault system. The host rocks of the volcanic complex consist of Eocene sedimentary and volcanic rocks covered by Miocene sedimentary rocks. LA-ICP–MS U–Pb zircon geochronology yields a mean age of 6.2 ± 0.2 Ma for magmatic activity at Chah Zard. This age represents the maximum age of mineralization and may indicate a previously unrecognized mineralization event in the UDMA. Breccias and veins formed during and after the waning stages of explosive brecciation events due to shallow emplacement of rhyolite porphyry. Detailed systematic mapping leads to the recognition of three distinct breccia bodies: volcaniclastic breccia with a dominantly clastic matrix; gray polymict breccia with a greater proportion of hydrothermal cement; and mixed monomict to polymict breccia with clay matrix. The polymictic breccias generated bulk-mineable ore, whereas the volcaniclastic breccia is relatively impermeable and largely barren. Precious metals occur with sulfide and sulfosalt minerals as disseminations, as well as in the veins and breccia cements. There is a progression from pyrite-dominated (stage 1) to pyrite-base metal sulfide and sulfosalt-dominated (stages 2 and 3) to base metal sulfide-dominated (stage 4) breccias and veins. Hydrothermal alteration and deposition of gangue minerals progressed from illite-quartz to quartz-adularia, carbonate, and finally gypsum-dominated assemblages. Free gold occurs in stages 2 and 4, principally intergrown with pyrite, quartz, chalcopyrite, galena, sphalerite, and Ag-rich tennantite–tetrahedrite, and also as inclusions in pyrite. High Rb/Sr ratios in ore-grade zones are closely related to sericite and adularia alteration. Positive correlations of Au and Ag with Cu, As, Pb, Zn, Sb, and Cd in epithermal veins and breccias suggest that all these elements are related to the same mineralization event.  相似文献   

18.
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19.
Please refer to the attachment(s) for more details  相似文献   

20.
Differential earth movements occurred during Eocene, Miocene, and late Caino‐zoic times. The faulting formed basins of sedimentation, led to dissection of land‐surfaces in some localities and burial in others, and faulted the Cainozoic sediments.

Laterite and silcrete cap remnants of relict landsurfaces of two different ages. Laterite formed before the Eocene; it was faulted and dissected during the Eocene in the north but continued to develop until the Miocene in the south. Silcrete formed from Eocene to Miocene times; its dissection was promoted by late Cainozoic tectonism.

Since laterite and silcrete formed on the same strata in warm, very moist environments, lithology and climate are not important genetic factors causing laterite to form at one time and silcrete at another. Only base levels of erosion differed. The silcrete surface was largely developed by streams flowing into mid‐Cainozoic lacustrine basins, whereas there is no evidence that these drainage conditions prevailed for laterite formation.  相似文献   

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