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1.
The presence of bacterial spores of the Bacillus cereus group in soils and stream sediments appears to be a sensitive indicator of several types of concealed mineral deposits, including vein-type gold deposits. The B. cereus assay is rapid, inexpensive, and inherently reproducible. The test, currently under investigation for its potential in mineral exploration, is recommended for use on a research basis.Among the aerobic spore-forming bacilli, only B. cereus and closely related strains produce an opaque zone in egg-yolk emulsion agar. This characteristic, also known as the Nagler of lecitho-vitellin reaction, has long been used to rapidly indentify and estimate presumptive B. cereus. The test is here adapted to permit rapid estimation of B. cereus spores in soil and stream-sediment samples. Relative standard deviation was 10.3% on counts obtained from two 40-replicate pour-plate determinations. As many as 40 samples per day can be processed. Enough procedural detail is included to permit investigation of the test in conventional geochemical laboratories using standard microbiological safety precautions.  相似文献   

2.
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3.
Summary The Late Paleozoic Kochbulak and Kairagach deposits are located on the northern slope of the Kurama Ridge, Middle Tien Shan, in the same volcanic structure and the same ore-forming system. Au–Ag–Cu–Bi–Te–Se mineralization is confined to veins and dissemination zones accompanied by quartz-sericite wall-rock alteration. The tellurides, calaverite, altaite, hessite, and tetradymite are widespread at both deposits; at Kairagach selenides and sulfoselenides of Bi and Pb are common, while at Kochbulak Bi and Pb telluroselenides and sulfotelluroselenides are typical. The paragenetic sequence of telluride assemblages are similar for both deposits and change from calaverite + altaite + native Au to sylvanite + Bi tellurides + native Te, Bi tellurides + native Au, and, finally, to Au + Ag tellurides with time. These mineralogical changes are accompanied by an increase in the Ag content of native gold that correlates with a decrease in temperature, fTe2 and fO2 and an increase in pH.  相似文献   

4.
A pilot survey on a microbial mineral exploration method based on soil Bacillus cereus spore counts was carried out across three different gold mining regions, which vary in soil type, climate condition and geological setting in northwestern Sichuan, China. B-horizon soils from these sites were analyzed for B. cereus spores, Au, Ag, Cu, Pb and Zn. The results show that the nmnbers of B. cereus spores generally increased in soils overlying gold mineralization. Specifically, elevated spore counts were found in samples slightly offset from the outcrops of orebodies, whereas soils directly above the outcrops of orebodies usually contained low spore counts. However, the background counts of B. cereus spores varied from place to place and were complicated by environmental and pedological factors, but the rela-tive ratios of spore counts still were indicative of the underlying gold mineralization.  相似文献   

5.
Abstract: A spectrum of intrusion-related vein gold deposits is recognized. Representative examples are described of the following geochemical associations: Au-Fe oxide–Cu, Au–Cu–Mo–Zn, Au–As–Pb–Zn–Cu, Au–Te–Pb–Zn–Cu and Au–As–Bi–Sb. The associated intrusions range from small outcropping stocks to complex batholiths. The different vein associations are believed to reflect the compositions of related intrusions, which themselves characterize distinct tectonic settings. The Au-Fe oxide–Cu and Au–Cu–Mo–Zn associations belong to two broad groups of deposits, Fe oxide–Cu–Au and porphyry Cu–Au, both of which are related to highly oxidized calc-alkaline intrusions emplaced in sub–duction–related arcs. The Au–As–Pb–Zn–Cu association seems to be linked to somewhat less oxidized intrusions emplaced in a similar setting. The Au–Te–Pb–Zn–Cu association, which possesses well-known epithermal counterparts, is also found with highly oxidized intrusions, but of alkaline composition and back-arc location. In contrast, the Au–As–Bi–Sb association, part of a newly recognized class of intrusion-hosted Au–Bi–W–As deposits, is related to relatively reduced intrusions, spanning the boundary between the magnetite– and ilmenite–series. Such intrusions, which may host major bulk-mineable gold deposits, were emplaced along the landward sides of arcs, possibly during lulls in subduction, as well as in continental collision settings. Therefore, a variety of geological environments is prospective for vein and, by extrapolation, other styles of gold mineralization, not all of them fully appreciated in the past. Several features of vein gold deposits, including imprecise relationships to individual intrusive phases, poorly developed mineral and metal zoning, apparent time gaps between intrusion and mineralization and presence of low–salinity, CO2–rich fluid inclusions, are commonly taken to indicate a non-igneous origin and to be more typical of orogenic (mesothermal) gold deposits generated during accretionary tectonic events. However, several or all of these features apply equally to some intrusion– related vein gold deposits and, therefore, do not constitute distinguishing criteria. The currently popular assignment of most gold-rich veins to the orogenic category requires caution, because of the geological convergence that they show with some intrusion-related deposits. A proper distinction between intrusion-related and orogenic gold deposits is crucial for exploration planning.  相似文献   

6.
《Applied Geochemistry》2005,20(4):767-787
The supergiant Pb–Zn–Ag Broken Hill orebody and numerous other minor mineral deposits occur within the limited outcrop of the Proterozoic Curnamona Province of Australia. The vast majority of this Province is concealed by up to 200 m of transported regolith, hampering conventional exploration strategies. Approximately 300 groundwater samples were collected over the southern Curnamona Province to test whether this medium could be helpful in the search for hidden mineral deposits. Sulphur, Sr and Pb isotope composition of the groundwaters were determined and S excess (SXS), i.e., the amount of S that can be ascribed neither to evaporation nor to mixing, was calculated. Many samples were recognised to have undergone an addition of 34S-depleted S, which can be attributed to oxidation of sulfides with a Broken Hill type δ34S signature (average ∼0‰ V-CDT). Furthermore, Sr isotopes identify the broad types of bedrock that the groundwater has been interacting with, from the less radiogenic Adelaidean rocks (and minerals) in the west (groundwater 87Sr/86Sr ratio as low as 0.708) to the highly radiogenic Willyama Supergroup in the east (87Sr/86Sr ratio up to 0.737). The groundwaters have 207Pb/204Pb and 206Pb/204Pb ratios comparable to, or intermediate between, various mineralisation types recognised in the area (Broken Hill, Rupee, Thackaringa, etc., types). The few samples taken in the vicinity of known mineralisation yield positive indicators (positive SXS, low δ34S, 87Sr/86Sr signature of bedrock type and Pb isotope fingerprinting of mineralisation type). This study also highlights several new locations under sedimentary cover where these indicators suggest interaction with mineralisation.  相似文献   

7.
Abstract

The Yilgarn Craton of Western Australia hosts a number of Cenozoic paleochannels, which have been incised into the underlying Paleozoic and Precambrian rocks, filled with sediments and subsequently weathered. The paleochannels are of particular interest in mineral exploration as they may not only host placer-type deposits but also overlie significant supergene and primary mineralisation. Paleochannels also pose particular challenges during exploration as they mask underlying geochemical anomalies, including gold and pathfinder elements. This study investigates a method of distinguishing transported overburden from residual regolith utilising a combination of field and laboratory-based techniques. At the Minotaur deposit, the residual regolith and transported overburden are mineralogically similar, although the presence of biotite, chlorite and muscovite is more characteristic of the residual regolith. Geochemically, Zr, Ti, Co and Sc ratios form distinct groupings allowing more confident discrimination of transported overburden from the underlying residual regolith units. The presence of a distinct gold depletion zone at the redox front was also identified to be a feature of the Minotaur deposit, with Au enrichment occurring above (within transported overburden) and below (within saprolite) the redox front, similar to other gold deposits on Lake Lefroy. The lithological, stratigraphic and Au-enrichment characteristics at Minotaur have also been compared with regional studies and suggest the long-lived impact of paleovalleys on the depositional systems and Au distribution of Lake Lefroy. This work provides a basis for future studies of the region in particular the variation of depositional sequences within regional paleochannel networks.  相似文献   

8.
The Dest-Or epigenetic Au deposit occurs in a breccia zone within gabbro, basalt and andesite of the Archean Upper Deguisier Formation. It is located approximately 30 km NE of Noranda. Quebec and 2.5 km N of the Porcupine-Destor Fault, an important vertical shear zone that extends east-west for more than 100 km. The known orebody contains 2.44 Mt of ore at 4.29 g/t Au.Host rocks of the Upper Deguisier Formation typically contain 3.6 ppb Au, 0.8 ppm Sb and 4.5 ppm As. The Au values are comparable to those of tholeiitic mafic rocks elsewhere in the world. but Sb and As values are a little higher.Gold values on approximately 30% of the area of the Dest-Or and Bassignac properties define a log-normal distribution with a median at 9.4 ppb Au (P16 at 3.1 and P84 at 27). These are referred to as ore zone halos: they envelop orebody halos which in turn envelop orebodies.An orebody halo can best be defined by close sampling in the immediate vicinity of a known orebody. Around the Dest-Or orebody, this halo is approximately 100 m wide (60 m on the hanging wall and 40 m on the footwall), and it has a median value at 37 ppb Au (P16 at 17 and P84 at 74).Gold enrichment in the orebody is 1900 times background value. There are also lesser but significant Sb and As enrichments (20 /sX each). High W values occur in the ore ( > 30 ppm W), but background values were too low ( <5 ppm) to be established with confidence.Gold analyses in the 0.2–100 ppb range can be gainfully used in the search for blind gold ore deposits: As, Sb and W can also be used, but anomalies are less extensive and enrichment is also less pronounced.  相似文献   

9.
To discriminate the mineral potentiality of the trachybasalt around the Miocene Sarcheshmeh porphyry copper deposit, petrogeochemical characteristics of more than 45 samples of the volcanic rocks were studied. Sarcheshmeh is one of the world's largest Miocene porphyry copper deposits in a continental arc setting and contains about 1200 million tonnes of ores with an average grade of 1.2 percent copper, 0.03 percent molybdenum, 3.9 g/t Ag and 0.11 g/t Au. The biotized and sericitized trachybasalts around the Sarcheshmeh deposit are associated with chalcopyrite, pyrite and molybdenite and and are enriched in Cu (>3108 ppm), K2O (>4.2%), Rb (>155 ppm) and MgO (>2.9%), but depleted in yttrium (<11 ppm), MnO (<0.06%), CaO (<0.6%), Na2O (<0.33%), Sr (<107 ppm), and Ba (<181 ppm). The propylitized trachybasalts are enriched in CaO (>9.1%), Na2O (>3.2%), MnO (>0.24%), Y (>18.2 ppm), and Ba (>323 ppm). The results demonstrate that the diagrams of loss on ignition ? Cu, Cu ? Y, K2O/K2O + Na2O + CaO ? Cu and Y ? MnO may be used as an exploration guide for undiscovered porphyry copper mineralization in the Central Iranian volcano—plutonic copper belt.  相似文献   

10.
The presence of base‐metal mineralization at Woodlawn was first recognised early in 1968 when a roadside reconnaissance geochemical sampling survey, conducted over felsic volcanic rocks in the Goulburn‐Tarago area, encountered anomalous B horizon soils containing up to 200 ppm Cu, 800 ppm Pb and 300 ppm Zn. Regional soil thresholds have been determined at 50 ppm Cu, 90 ppm Pb and 50 ppm Zn. Chip samples from the subsequently located gossan revealed up to 2000 ppm Cu, 8000 ppm Pb and 2000 ppm Zn, 500 ppm Sn, 25 ppm Ag and 3000 ppm As.

The first grid B horizon soil geochemical survey was conducted in 1968 over the gossan and surrounding area, and repeated with closer spaced sampling in the first half of 1970. The first survey delineated strong Cu (to 1000 ppm) and Pb (to 2500 ppm) anomalies coincident with the gossan zone, and intense hydromorphic zinc anomalies (to 3000 ppm) located down slope from the gossan in residual clay‐soils derived from dolerite bedrock. Threshold values have been determined at 140 ppm Cu, 700 ppm Pb and 580 ppm Zn. Ag and Sn in B horizon soils show pronounced anomalies coincident with the gossan and are suitable metals for geochemical target definition. Of fourteen trace elements determined in 1974 from B and C horizon soils on two lines across the ore zone Cu, Pb, Zn, Se, Ba, Sn and Ag show direct correlation with the mineralization, whereas Cd and Mn show moderate hydromorphic dispersion, having accumulated principally in clay soils derived from dolerite weathering. As, Sb and Bi, whilst responding over the ore zone, show elevated values in soils over hanging‐wall units; Ni and Co show maximum levels in soils over dolerite bedrock.

Bark and leaves of Acacia mearnsii, collected from a line across the gossan, contain anomalous levels of Cu, Pb, Zn, Sn and Ti near the ore zone, and weaker, but clearly anomalous Mn and Ni levels over dolerite bedrock. Both bark and leaves of Acacia mearnsii reflect the presence of concealed mineralization. The shrub Solanum linearifolium grows preferentially over and close to the Woodlawn ore zone, where it contains up to 840 ppm Cu, 250 ppm Pb, 7300 ppm Zn, 6 ppm Sn and 250 ppm Ti in leaf ash compared with levels of 200 ppm Cu, 2 ppm Pb, 400 ppm Zn, 0.8 ppm Sn and 60 ppm Ti in plants growing 1.5 km from the ore zone. This shrub has potential as an indicator of base‐metal mineralization.  相似文献   

11.
Ground-water, alluvium, and bedrock samples were collected from drill holes near the Chimney Creek, Preble, Summer Camp, and Rabbit Creek disseminated gold deposits in northern Nevada to determine if Au and ore-related metals, such as As, Sb, and W, are being hydromorphically mobilized from buried mineralized rock, and, if they are, to determine whether the metal-enriched ground water is reacting with the alluvial material to produce a geochemical anomaly within the overburden.Results of chemical analyses of drill-hole water samples show the presence of hydromorphic dispersion anomalies of Au, As, Sb, and W in the local ground-water systems associated with these deposits. Background concentrations for Au in the ground water up-gradient from the buried deposits was less than 1 nanogram per liter (ng/L), near the deposits the Au values ranged from 1 to 140 ng/ L, and in drill holes penetrating mineralized rock, concentrations of Au in the ground water were as high as 4700 ng/L. Highest concentrations of Au were found in ground-water samples where the measured Eh and the distribution of arsenic species, arsenite [As(III)] and arsenate [As(V)], indicated oxidizing redox potentials. Similarly, As, Sb, and W concentrations in the ground water near the deposits were significantly enriched relative to concentrations in the ground water up-gradient from the deposits. In general, however, the highest concentrations of As, Sb, and W occurred in ground-water samples where the measured Eh and the distribution of arsenic species indicated reducing conditions. Arsenic concentrations ranged from 9 to 710 micrograms per liter (μg/L); Sb, from less than 0.1 to 250 μg/L; and W, from 1 to 260 μg/L.In addition, analysis of sequential dissolution and extraction solutions of drill cuttings of alluvium and bedrock indicate geochemical anomalies of gold and ore-related metals in the overburden at depths corresponding to the location of the present-day water table. This relationship suggests that water-rock reactions around these buried deposits are active and that this information could be very useful in exploration programs for concealed disseminated gold deposits.  相似文献   

12.
This study investigates the potential risks associated with high levels and long term exposure of carbon dioxide (CO2) on the mobility and speciation of exchangeable metals in soils. CO2 incubation batch experiments at high pressure and temperature coupled with geochemical modelling were carried out to elucidate the behaviour and mobilisation of metals and the response of soil chemical parameters as a result of long term CO2 exposure. A t-Student analysis was performed to ascertain whether differences in the mean concentration of exchangeable metals in soils before and after CO2-incubations are attributable to increase of metal molibilisation because of the long term CO2 exposure. The t-Student revealed the CO2 long term incubation was statistically significant (p < 0.05) for the exchangeable concentration of Ni, Zn, and Pb. The CO2-soil incubation induces the acidification of the pore water of soils via CO2 hydrolysis and as a consequence, it increases the exchangeable concentration of Ni, Zn, and Pb in the soils. As, Al, Cr, Cu, and Fe show a different mobilisation pattern depending on the moisture content in soils. Al3+, Fe2+, Cr3+, and Cu2+ as free cations, As as HAsO2, Pb2+and PbHCO3−, Zn2+ and ZnHCO3−, are predicted to be the predominant aqueous complexes in the pore water of the incubated soils.  相似文献   

13.
Six epizonal gold deposits in the 30-km-long Yangshan gold belt, Gansu Province are estimated to contain more than 300 t of gold at an average grade of 4.76 g/t and thus define one of China's largest gold resources. Detailed paragenetic studies have recognized five stages of sulfide mineral precipitation in the deposits of the belt. Syngenetic/diagenetic pyrite (Py0) has a framboidal or colloform texture and is disseminated in the metasedimentary host rocks. Early hydrothermal pyrite (Py1) in quartz veins is disseminated in metasedimentary rocks and dikes and also occurs as semi-massive pyrite aggregates or bedding-parallel pyrite bands in phyllite. The main ore stage pyrite (Py2) commonly overgrows Py1 and is typically associated with main ore stage arsenopyrite (Apy2). Late ore stage pyrite (Py3), arsenopyrite (Apy3), and stibnite occur in quartz ± calcite veins or are disseminated in country rocks. Post-ore stage pyrite (Py4) occurs in quartz ± calcite veins that cut all earlier formed mineralization. Electron probe microanalyses and laser ablation-inductively coupled plasma mass spectrometry analyses reveal that different generations of sulfides have characteristic of major and trace element patterns, which can be used as a proxy for the distinct hydrothermal events. Syngenetic/diagenetic pyrite has high concentrations of As, Au, Bi, Co, Cu, Mn, Ni, Pb, Sb, and Zn. The Py0 also retains a sedimentary Co/Ni ratio, which is distinct from hydrothermal ore-related pyrite. Early hydrothermal Py1 has high contents of Ag, As, Au, Bi, Cu, Fe, Sb, and V, and it reflects elevated levels of these elements in the earliest mineralizing metamorphic fluids. The main ore stage Py2 has a very high content of As (median value of 2.96 wt%) and Au (median value of 47.5 ppm) and slightly elevated Cu, but relatively low values for other trace elements. Arsenic in the main ore stage Py2 occurs in solid solution. Late ore stage Py3, formed coevally with stibnite, contains relatively high As (median value of 1.44 wt%), Au, Fe, Mn, Mo, Sb, and Zn and low Bi, Co, Ni, and Pb. The main ore stage Apy2, compared to late ore stage arsenopyrite, is relatively enriched in As, whereas the later Apy3 has high concentrations of S, Fe, and Sb, which is consistent with element patterns in associated main and late ore stage pyrite generations. Compared with pyrite from other stages, the post-ore stage Py4 has relatively low concentrations of Fe and S, whereas As remains elevated (2.05～3.20 wt%), which could be interpreted by the substitution of As? for S in the pyrite structure. These results suggest that syngenetic/diagenetic pyrite is the main metal source for the Yangshan gold deposits where such pyrite was metamorphosed at depth below presently exposed levels. The ore-forming elements were concentrated into the hydrothermal fluids during metamorphic devolatilization, and subsequently, during extensive fluid–rock interaction at shallower levels, these elements were precipitated via widespread sulfidation during the main ore stage.  相似文献   

14.
We investigate the geology of Altar North (Cu–Au) and Quebrada de la Mina (Au) porphyry deposits located in San Juan Province (Argentina), close to the large Altar porphyry copper deposit (995 Mt, 0.35% Cu, 0.083 g/t Au), to present constraints on the magmatic processes that occurred in the parental magma chambers of these magmatic-hydrothermal systems. Altar North deposit comprises a plagioclase-amphibole-phyric dacite intrusion (Altar North barren porphyry) and a plagioclase-amphibole-biotite-phyric dacite stock (Altar North mineralized porphyry, 11.98 ± 0.19 Ma). In Quebrada de la Mina, a plagioclase-amphibole-biotite-quartz-phyric dacite stock (QDM porphyry, 11.91 ± 0.33 Ma) crops out. High Sr/Y ratios (92–142) and amphibole compositions of Altar North barren and QDM porphyries reflect high magmatic oxidation states (fO2 = NNO +1.1 to +1.6) and high fH2O conditions in their magmas. Zones and rims enriched in anorthite (An37–48), SrO (0.22–0.33 wt.%) and FeO (0.21–0.37 wt.%) in plagioclase phenocrysts are evidences of magmatic recharge processes in the magma chambers. Altar North and Quebrada de la Mina intrusions have relatively homogeneous isotopic compositions (87Sr/86Sr(t) = 0.70450–0.70466, εNd(t) = +0.2 to +1.2) consistent with mixed mantle and crust contributions in their magmas. Higher Pb isotopes ratios (207Pb/204Pb = 15.6276–15.6294) of these intrusions compared to other porphyries of the district, reflect an increase in the assimilation of high radiogenic Pb components in the magmas. Ages of zircon xenocrysts (297, 210, 204, 69 Ma) revealed that the magmas have experienced assimilation of Miocene, Cretaceous, Triassic and Carboniferous crustal rocks.Fluids that precipitated sulfides in the Altar deposit may have remobilized Pb from the host rocks, as indicated by the ore minerals being more radiogenic (207Pb/204Pb = 15.6243–15.6269) than their host intrusions. Au/Cu ratio in Altar porphyries (average Au/Cu ratio of 0.14 × 10?4 by weight in Altar Central) is higher than in the giant Miocene porphyry deposits located to the south: Los Pelambres, Río Blanco and Los Bronces (Chile) and Pachón (Argentina). We suggest that the increase in Au content in the porphyries of this region could be linked to the assimilation of high radiogenic Pb components in the magmas within these long-lived maturation systems.  相似文献   

15.
The paper considers the results of high-precision Pb–Pb isotopic analysis of 120 galena samples from 27 Au and Ag deposits of the South Verkhoyansk Synclinorium (SVS) including large Nezhdaninsky deposit (628.8 t Au). The Pb isotopic composition is analyzed on a MC-ICP-MS NEPTUNE mass-spectrometer from solutions with an error of no more than ±0.02% (2σ). Four types of deposits are studied: (i) stratified vein gold–quartz deposits (type 1) hosted in metamorphosed Upper Carboniferous–Lower Permian terrigenous rocks and formed during accretion of the Okhotsk Block to the North Asian Craton synchronously with dislocation metamorphism and related granitic magmatism; (ii) vein gold–quartz (Nezhdaninsky type) deposits also hosted in Lower Permian metasedimentary rocks; (iii) Au–Bi deposits localized at the contact zones of the Late Cretaceous granitic plutons; and (iv) Sn–Ag polymetallic deposits related to granitic and subvolcanic rocks of the Okhotsk Zone of the SVS. The deposits of types 2, 3, and 4 are postaccretionary. The general range of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios is 18.1516–18.5903 (2.4%), 15.5175–15.6155 (0.63%), and 38.3010–39.0481 (2.0%), respectively. In 206Pb/204Pb–207Pb/204Pb and 206Pb/204Pb–208Pb/204Pb diagrams, the data points of Pb isotopic compositions of all deposits occupy restricted, partly overlapping areas along a general elongated trend. The various SVS Au–Ag deposits can be classified according to the Pb isotopic composition in accordance with all three Pb ratios. Deposits of the same type show distinct Pb isotopic compositions that strongly exceed the scale of analytical error (±0.02%). The differences in Pb isotopic composition within specific deposits are low and subordinate and have little effect on variations in the Pb isotopic composition of the SVS deposits. The μ2 values (Stacey–Kramers model), which characterize the 238U/204Pb ratios of ore lead sources of the SVS deposits, widely vary from 9.7 to 9.38. The ω2 values (232Th/204Pb) are 39.82–36.61, whereas the Th/U ratios are 4.04–3.86. The content of all three radiogenic Pb isotopes and μ2 values of feldspars from SVS intrusive rocks are strongly distinct from those of galena of stratified gold–quartz and vein gold–quartz deposits and are identical to Pb of galena from Au–Bi and Sn–Ag polymetallic deposits, indicating a mostly magmatic origin for the Pb of these deposits. Detailed isotopic study of the Nezhdaninsky deposit shows different Pb isotopic composition of two consecutive mineral assemblages (gold–sulfide and Ag polymetallic): ~0.30, ~0.07, and ~0.22% for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios, respectively. These differences are interpreted as a result of involvement of at least two metal sources during the evolution of an ore-forming system: (i) host Lower Permian terrigenous rocks and (ii) a magmatic source similar in Pb isotopic composition to that of Sn–Ag polymetallic deposits. The Pb isotopic composition and μ2 and Th/U values show that lead of stratified gold–quartz deposits combines isotopic tracers of lower and upper crustal sources (Upper Carboniferous–Lower Permian terrigenous rocks), lead of which was mobilized by ore-bearing fluids. The high 208Pb/206Pb ratios and Th/U evolutionary parameter are common to all Pb isotopic composition of all studied Au–Ag deposits and SVS Cretaceous intrusive rocks and indicate that Pb sources were depleted in U relative to Th. Taking into account the structure of the region and conceptions on its evolution, we can suggest that the magma source was related to lower crustal subducted rocks of the Archean (~2.6 Ga) North Asian Craton and the Okhotsk terrane.  相似文献   

16.
In the Hetai goldfield, Guangdong Province, China, samples including rocks, soils and leaves of four plants (Pinus massoniana, Rhodomyrms tomenlosa, D. linearis var. dichotoma and Embelia laeta) collected from the gold mineralization zone and the background area were analyzed for Au, Ag, Cu, Pb, Zn, Hg, As and physiological parameters. The objective of this investigation is to study the geochemical and biogeochemical characteristics of studied plants, aiming at biogeochemical methods in Au exploration. The goldfield region shows geochemical and biogeochemical anomalies. Abundances of Au in rocks, soils, plants and the leaf pigments in the mineralized area are much higher than those in the surrounding region. The plants display unhealthy physiological and ecological characteristics in the Hetai goldfield area. The cell structures of the goldfield plants were anomalous and aberrant, and there were many nano-metal particles diffused in mitochondria and chloroplasts. Macro- and microscopic evidences of the vegetation in the goldfield areas are distinctly different from the background regions. The strongly anomalies in responses to Au are profound in further geochemical and botanic exploration studies.  相似文献   

17.
The concentration and distribution of metals were studied in metallophytes, growing on and in the vicinity of Pb–Zn gossans, NW Queensland. The study investigated the accumulation of metals in plant species and assessed their potential use as indicators in geobotanical and biogeochemical prospecting and as metal excluders in mine site rehabilitation. Plant species colonising the gossans tolerate high concentrations of metals. Total mean metal concentrations of soils ranged from minima of 14 ppm Cu, 28 ppm Pb and 34 ppm Zn in background areas to maxima of 660 ppm Cu, 12000 ppm Pb and 2100 ppm Zn over mineralised soils. Over the gossans, the grass species Eriachne mucronata forma, Enneapogon lindleyanus and Paraneurachne muelleri replace the characteristic grass Triodia molesta where the soils have high Pb and Zn concentrations. Of the 16 plant species identified, 3 of them, Hybanthus aurantiacus, Clerodendrum tomentosum and Bulbostylis barbata, were confined to the gossan sites. B. barbata appears to be of particular use in geobotanical prospecting as it indicates base metal mineralisation in the region.  相似文献   

18.
辽东地区金矿床主要分布在丹东、青城子、营口－盖县、清原等4个金矿化集中区（带）。S，Pb同位素特征显示金矿的成矿物主要来源于下地壳和上地幔。成矿流体中的CO2与金矿成矿关系密切，在成矿过程中流体的盐度较低，且由弱酸性向弱碱性变化，金矿多为中低温矿床。韧性剪切带对金矿化的空间分布显示出多级有序的控制作用，同时对金矿的矿床类型和矿化类型也表现出显著的控制作用，构造应变场和地球化学场的改变，促使成矿元素迁移富集而形成金矿。研究认为，在元古宇分布区，在深部寻找脆韧性变形带中的金矿仍然具有较大远景，同时要注意寻找与BIF建造有关的金矿新类型。  相似文献   

19.
李福让  吕新彪 《西北地质》2007,40(B07):71-78
南秦岭南部褶皱带是秦岭造山带的重要组成部分，随着找矿勘查工作的深入，相继发现了一系列金、银、锑、铅、锌、铜矿床（点），成为陕西省又一重要有色、贵金属成矿带。南秦岭南部元古宙至中生代多次发生火山成矿作用、沉积或喷流沉积成矿作用和构造-岩浆成矿作用，金、银、锑、铅、锌、铜成矿具有一定的规律，找矿前景好。从资源潜力及经济意义上来看，金应该是该区的主攻矿种。同时，应该兼顾银、锑、铅、锌、铜的找矿工作。开展自水江-留坝成矿带金、银锑找矿、牛山隆起北缘成矿带金铜多金属找矿和红椿坝断裂两侧铜金找矿是主要找矿方向。  相似文献   

20.
The Archaean Yilgarn Craton (Western Australia) is a world-class metallogenic province, hosting considerable resources of Au, Ag, Ni, Cu, Zn and Fe. Here we present trace element compositions of pyrite from > 30 orogenic Au and 5 volcanic hosted massive sulphide (VHMS) deposits across the Yilgarn. Pyrites from VHMS deposits tend to have higher Sn, Se, Cu, Pb, Bi and lower Ni relative to orogenic deposits. VHMS deposit pyrites commonly have Co > Ni, As > 100Au, Te > Au, Se > Te. Orogenic gold deposits could be subdivided based on association of Au with As or Te. Pyrites from AuAs ores generally have Pb/Bi > 5, Se/Te > 5, Pb/Sb < 5 and Tl/Te > 100 and the majority of Au is refractory (in pyrite structure). At the same time AuTe association pyrites are characterised by lower values of Pb/Bi, Se/Te and Tl/Te, higher values of Ag/Au, Pb/Sb and Au generally resides in inclusions of different compositions. Our data can be used at the exploration stage to distinguish between VHMS vs Orogenic Au signatures. For all studied deposits inclusion populations are summarised with implications for Au and Ag deportment. Orogenic Au deposits from the Yilgarn mostly have multistage formation histories reflected in the presence of multiple generations of pyrites. However, only some deposits record multiple high Au mineralisation events.  相似文献   

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