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1.
A kyanite mine in central Virginia produces a silicate-rich waste stream which accumulates at a rate of 450,000–600,000 tons
per year. An estimated 27 million tons of this waste stream has accumulated over the past 60 years. Grain size distribution
varies between 1.000 and 0.053 mm, and is commonly bimodal with modes typically being 0.425 and 0.250 mm and uniformity coefficients
vary from 2.000 to 2.333. Hydraulic conductivity values vary from 0.017 to 0.047 cm/s. Mineralogy of the waste stream consists
of quartz, muscovite, kyanite and hematite. Muscovite grains have distinct chemical compositions with significant Na2O content (1.12–2.66 wt%), TiO2 content (0.63–1.68 wt% TiO2) and Fe content, expressed as Fe2O3 (up to 1.37 wt%). Major element compositions of samples were dominated by SiO2 (87.894–90.997 wt%), Al2O3 (6.759–7.741 wt%), Fe2O3 (1.136–1.283 wt%), and K2O (0.369–0.606 wt%) with other components being <1.000 wt%. Elements of environmental concern (V, Cr, Ni, Cu, Zn, As, Ag,
Sn, Sb, Ba, Hg, Tl, and Pb) were detected; however, the concentrations of all elements except Ni were below that of the kyanite
quartzites in the region from which the waste is derived. Both major and trace element compositions indicate minimal variation
in composition. The waste stream has potential for recycling. Muscovite is suitable for recycling as a paint pigment or other
industrial applications. Muscovite and hematite are commonly intergrown and are interpreted to be material where much of the
elements of environmental concern are concentrated. Reprocessing of the waste stream to separate muscovite from other components
may enable the waste stream to be used as constructed wetland media for Virginia and nearby states. Recycling of this mine
waste may have a positive impact on the local economy of Buckingham County and aid in mitigation of wetland loss. 相似文献
2.
Mark Paul Speeg Krekeler C. Scott Allen Lance E. Kearns J. Barry Maynard 《Environmental Earth Sciences》2010,61(1):93-106
Kyanite Mining Corporation, located in Dillwyn, Virginia has been in operation for over 50 years and their local operation
is the largest kyanite mine in the world. As part of the processing at this location, a magnetic separate is generated and
a minimum estimation of 3.57 million tons of waste has accumulated. Currently no use for the magnetic separate has been identified.
We investigated eight representative samples of the magnetic mine waste which varied in color from a dark tan to black, to
determine if the waste could be recycled as an ore or could be used as an environmental media. Mineralogical investigations
indicate the composition of the magnetic mine waste is dominated by magnetite, kyanite, lesser amounts of hematite and charcoal.
Magnetite occurs as fine grained crystals and as inclusions in kyanite. Hematite occurs largely as botryoidal textures, as
discrete grains, and as coatings on kyanite grains. Fe-oxide spheres ranging in diameter from approximately 5–100 μm are common
and may compose up to 10% in some samples. Titanium dioxide was rarely observed as coatings on silicate mineral grains. Energy
dispersive spectroscopy analysis on magnetite crystals indicates they have end-member compositions. Bulk property investigations
indicate that grain size distributions of samples are primarily unimodal with 20–40% of material being between 0.600 and 0.250 mm.
Hydraulic conductivity values of samples investigated vary between 0.0036 and 0.0077 cm/s and are broadly consistent with
those expected of sands with similar grain size distributions. In addition to the magnetic waste stream a light blue, water
soluble, amorphous Cu sulfate occurs as a coating on surfaces of boulders. The coating is composed of rounded interlocking
particles 5–60 μm in diameter. This material is of some environmental concern for freshwater invertebrates, but can be managed
using sorption media. Hyperspectral data were gathered of the magnetic separate, kyanite ore samples, and the light blue Cu
sulfate. The signatures of the kyanite ore, the blue mineral coating, and a mixture of the two provide spectral fingerprints
that an imaging spectrometer could exploit for rapid detection and subsequent environmental monitoring. 相似文献
3.
Behavior of heavy metals in sulfide mine tailings and bottom sediment (Salair,Kemerovo region,Russia) 总被引:2,自引:1,他引:1
The given work focused on solving the problem of environmental geochemistry related to investigation of element speciation,
their mobility, and migration in polluted areas. The purpose was to describe quantitatively migration, distribution, and redistribution
of heavy metals by the example of the old tailings (Talmovaya sands) of the Lead Zinc Concentration Plant (Salair, Kemerovo
region, Russia) and technogenic bottom sediments of the Malaya Talmovaya river. Contents of elements in the sulfide tailings
range in the following limits: Zn: 1,100–27,000 ppm, Cd: 1.3–240 ppm, Pb: 0.01–0.81 ppm, Cu: 220–960 ppm, As: 15–970 ppm,
Fe: 19,000–76,000 ppm, and Ba: 80,000–1,00,000 ppm. Element concentrations in the river sediment are proportional to the element
contents in the sulfide tailings. Element speciations in the sulfide tailings and technogenic bottom sediments were investigated
by the modified sequential extraction procedure. Chemical forms of heavy metals in pore water and surface water were calculated
by WATEQ4F software. Principles of heavy metal migration in the sulfide tailings and technogenic bottom deposits were established.
The obtained results about element species in the sulfide tailings and sediment explain the main principles of element migration
and redeposition. In the mine waste and technogenic bottom deposits, there is vertical substance transformation with formation
of geochemical barriers. 相似文献
4.
Sean H. McClenaghan David R. Lentz Jillian Martin Wilfredo G. Diegor 《Mineralium Deposita》2009,44(5):523-557
The 329-Mt Brunswick No. 12 volcanogenic massive sulfide deposit (total resource of 163 Mt at 10.4% Zn, 4.2% Pb, 0.34% Cu,
and 115 g/t Ag) is hosted within a Middle Ordovician bimodal volcanic and sedimentary sequence. Massive sulfides are for the
most part syngenetic, and the bulk of the sulfide ore occurs as a Zn–Pb-rich banded sulfide facies that forms an intimate
relationship with a laterally extensive Algoma-type iron formation and defines the Brunswick Horizon. Zone refining of stratiform
sulfides is considered to have resulted in the development of a large replacement-style Cu-rich basal sulfide facies, which
is generally confined between the banded sulfide facies and an underlying stringer sulfide zone. Complex polyphase deformation
and associated lower- to upper-greenschist facies regional metamorphism is responsible for the present geometry of the deposit.
Textural modification has resulted in a general increase in grain size through the development of pyrite and arsenopyrite
porphyroblasts, which tend to overprint primary mineral assemblages. Despite the heterogeneous ductile deformation, primary
features have locally been preserved, such as fine-grained colloform pyrite and base and precious metal zonation within the
Main Zone. Base metal and trace element abundances in massive sulfides from the Brunswick No. 12 deposit indicate two distinct
geochemical associations. The basal sulfide facies, characterized by a proximal high-temperature hydrothermal signature (Cu–Co–Bi–Se),
contains generally low Au contents averaging 0.39 ppm (n = 34). Conversely, Au is enriched in the banded sulfide facies, averaging 1.1 ppm Au (n = 21), and is associated with an exhalative suite of elements (Zn–Pb–As–Sb–Ag–Sn). Finely laminated sulfide lenses hosted
by iron formation at the north end of the Main Zone are further enriched in Au, averaging 1.7 ppm (n = 41) and ranging up to 8.2 ppm. Laser ablation inductively coupled plasma-mass spectrometry (ICP-MS) analyses of pyrite
(n = 97) from the north end of the Main Zone average 2.6 ppm Au and range from the detection limit (0.015 ppm) to 21 ppm. Overall,
these analyses reveal a distinct Au–Sb–As–Ag–Hg–Mn association within pyrite grains. Gold is strongly enriched in large pseudo-primary
masses of pyrite that exhibit relict banding and fine-grained cores; smaller euhedral pyrite porphyroblasts, and euhedral
rims of metamorphic origin surrounding the pyrite masses, contain much less Au, Sb, Ag, As, and Sn. Arsenopyrite, occurring
chiefly as late porphyroblasts, contains less Au, averaging 1.0 ppm and ranging from the detection limit (0.027 ppm) to 6.9 ppm.
Depth profiles for single-spot laser ablation ICP-MS analyses of pyrite and arsenopyrite display uniform values of Au and
an absence of discrete microscopic inclusions of Au-bearing minerals, which is consistent with chemically bonded Au in the
sulfide structure. The pervasive correlation of Au with Sn in the Zn–Pb-rich banded sulfide facies suggests similar hydrothermal
behavior during the waxing stages of deposition on the seafloor. Under high temperature (>350oC) and moderate- to low-pH conditions,
Au and Sn in hydrothermal fluids would be transported as chlorocomplexes. An abrupt decrease in temperature and aH2S, accompanied by an increase in fO2 and pH during mixing with seawater, would lead to the simultaneous destabilization of both Au and Sn chlorocomplexes. The
enrichment of Au in fine-grained laminated sulfides on the periphery of the deposit, accompanied by sporadic occurrences of
barite and Fe-poor sphalerite, supports lower hydrothermal fluid temperatures analogous to white smoker activity on the flanks
of a large volcanogenic massive sulfide system. In lower temperature (<350oC) and mildly acidic hydrothermal fluids, Au would
be transported by thiocomplexes, which exhibit multifunctional (retrograde–prograde) solubility and a capacity to mobilize
Au to the outer parts of the sulfide mound. The sluggish nature of this low-temperature venting together with larger variations
in ambient fO2 could lead to a sharp enrichment of Au towards the stratigraphic hanging wall of massive sulfide deposits.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
This study reports on the transfer of contaminants from waste rock dumps and mineralised ground into soils, sediments, waters
and plants at the rehabilitated Mary Kathleen uranium mine in semi-arid northwest Queensland. Numerous waste rock dumps were
partly covered with benign soil and the open pit mine was allowed to flood. The mineralised and waste calc-silicate rock in
the open pit and dumps has major (>1 wt%) Ca, Fe and Mg, minor (>1,000 ppm) Ce, La, Mn, P and S, subminor (>100 ppm) Ba, Cu,
Th and U, and trace (<100 ppm) As, Ni, Pb, Y and Zn values. Consequently, chemical and physical weathering processes have
acted on waste rock and on rock faces within the open pit, mobilising many elements and leading to their dispersion into soils,
stream sediments, pit water and several plant species. Chemical dispersion is initiated by sulfide mineral breakdown, generation
of sulfuric acid and formation of several soluble, transient sulfate minerals as evaporative efflorescent precipitates. Radiation
doses associated with the open pit average 5.65 mSv year−1; waste dumps commonly have lower values, especially where soil-covered. Surface pit water is slightly acid, with high sulfate
values accompanied by levels of U, Cu and Ni close to or above Australian water guideline values for livestock. Dispersion
of U and related elements into soils and stream sediments occurs by physical (erosional) processes and from chemical precipitation.
Plants growing in the mine void, on waste dumps and contaminated soil display evidence of biological uptake of U, LREE, Cu
and Th and to a lesser degree of As, Ni, Pb, Y and Zn, with values being up to 1–2 orders of magnitude above background sites
for the same species. Although rehabilitation procedures have been partly successful in reducing dispersion of U and related
elements into the surrounding environment, it is apparent that 20 years after rehabilitation, there is significant physical
and chemical mobility, including transfer into plants. 相似文献
6.
Thorsten Beitter Thomas Wagner Gregor Markl 《Contributions to Mineralogy and Petrology》2008,156(6):689-707
In this study, we have investigated the formation of quartz–kyanite veins of the Alpe Sponda, Central Alps, Switzerland. We
have integrated field observations, fluid inclusion and stable isotope data and combined this with numerical geochemical modeling
to constrain the chemical processes of aluminum transport and deposition. The estimated P–T conditions of the quartz–kyanite
veins, based on conventional geothermometry (garnet–biotite, white mica solvus and quartz–kyanite oxygen isotope thermometry)
and fluid inclusion data, are 550 ± 30°C at 5.0 ± 0.5 kbar. Geochemical modeling involved construction of aqueous species
predominance diagrams, calculation of kyanite and quartz solubility, and reaction–path simulations. The results of the modeling
demonstrate that (1) for the given chemical composition of the vein-forming fluids mixed Al–Si aqueous species are dominant
in transporting Al, and that (2) fluid cooling along a small temperature gradient coupled with a pH decrease is able to explain
the precipitation of the quartz–kyanite assemblages in the proportions that are observed in the Alpe Sponda veins. We conclude
that sufficient amounts of Al can be transported in typical medium- to high-grade regional metamorphic fluids and that immobile
behavior of Al is not very likely in advection–dominanted fluid–rock systems in the upper and middle crust. 相似文献
7.
A quantitative estimation of the factors affecting pH changes using simple geochemical data from acid mine drainage 总被引:3,自引:0,他引:3
The behavior of heavy metals in acid mine drainage (AMD) is mainly controlled by pH values. Therefore, a quantitative estimation
of factors affecting pH values in AMD is very important in predicting the behavior of those metals. Many different factors
cause pH changes in streams affected by AMD and we quantitatively estimated those factors by making simple equations from
geochemical data collected from the Dalsung mine. In a stream from that mine, the pH values decrease as the stream flows downstream
from the AMD source, which is different from normal streams affected by AMD. The stream shows low pH ranges (4.04–5.96), high
electrical conductivity (1,407–1,664 μS/cm), and sulfate concentration (680–854 ppm). Most ion concentrations decrease or
do not show noticeable changes mainly due to dilution. The change of the iron content is most significant, even though the
concentration of iron is relatively low compared with other ions. The iron concentration (13.4 ppm) becomes almost 0 ppm due
to precipitation. Schwertmannite is the dominant precipitated phase downstream and whitish basaluminite is observed in the
upstream. From our pH estimation, precipitation is the most important process lowering pH values from 5.96 to 4.04. The dilution
factor was calculated by the concentration changes in sulfate ions. Dilution increases pH values, but compared with the precipitation
factor, the contribution of the dilution factor to pH is relatively small. Alkalinity is the main factor that buffers hydrogen,
which is released by precipitation. The redox changes, which were calculated from the pH and Eh values, also affect pH at
each sampling site. The trend of estimated pH changes is almost identical to the observed ones, but the values are slightly
different. Some errors are expected mainly due to the uncertainty in the observed Eh values and the chemistry of the added
water for dilution. 相似文献
8.
Summary Somma-Vesuvius is an alkaline volcano whose products (pumice, scoria and lava) have alkaline (Na2O + K2O) contents between 6 and 16 wt%, Mg number <50, SiO2 59–47 wt% and MgO 0–7.8 wt% (more than 50% of the samples have a content <2 wt%). Immobile-element ratios (Th/Yb, Ta/Yb,
Ce/Yb) indicate a shoshonitic character, while the K2O content (4–10 wt%) is characteristic of ultrapotassic rocks. The behavior of selected metals is discussed by grouping them
on the basis of the stratigraphic sequence and differentiating the volcanic activity between plinian and interplinian (Rolandi et al., 1998; Ayuso et al., 1998). This allows observation of the variation within each formation from 25.000 y. BP to the last historic eruptive
cycle (1631–1944 AD). The main processes to explain the wide distribution of the data presented are fractional crystallization
of a mantle-derived magma, magma mixing, and contamination with heterogeneous lower and/or upper crust. Variation diagrams
distinguish different behavior for groups of metals: Ag (0.01–0.2 ppm), Mo (1–8.8 ppm), W (1.3–13 ppm), Pb (16–250 ppm), Sb
(0.2–2.6 ppm), Sc (0.2–61 ppm), Li (15–140 ppm) and Be (1–31 ppm) increase with increasing differentiation and tend to correlate
with the incompatible trace elements (Th, Hf, etc). Cu (10–380 ppm), Au (2–143 ppb), Co (0.7–35.1 ppm) and Fe (1.3–6.2 wt%)
decrease towards advanced stage of differentiation. Iron also identifies three magmatic groups. The ratio Fe3+/Fe2+ ranges between 0.2 and 1.8, and Fe2O3/(Fe2O3 + FeO) ranges between 0.2 and 0.8, giving rise to an oxidized environment; exceptions are in the samples belonging to the
interplinian formations: I, II, medieval and 1631–1994 AD. Fluorine ranges between 0.1 and 0.4 wt% for the complete Mt. Somma-Vesuvius
activity, except for the Ottaviano and Avellino plinian (0.8 wt%) events. Chlorine has a wider range, from 0.1 wt% to 1.6 wt%.
Mt Somma-Vesuvius has some features similar to those of mineralized alkaline magmatic systems which coincide with the transition
between subduction-related compression and extension-related to continental rifting. We infer that a prospective time for
the formation of mineralization at Mt Somma-Vesuvius was during the 1631–1944 eruptive period.
Received March 27, 2000; revised version accepted February 28, 2001 相似文献
9.
Throughout the ultrahigh-pressure (UHP) metamorphic unit of the Dora-Maira massif, western Alps, pyrope megablasts contain
the typical assemblage clinochlore–kyanite–talc–rutile ± phlogopite ± ellenbergerite as prograde inclusions. In the upper
part of the UHP unit in Val Gilba, some megablasts (XMg=0.89–0.98) contain in addition polymineralic inclusions consisting
of various combinations of enstatite, gedrite, sapphirine, clinochlore, talc, magnesiostaurolite and rare corundum or spinel.
We present evidence that these assemblages developed from cracks running across the megablasts, and are therefore of late
origin, post-dating the highest-pressure stage. Enstatite (XMg=0.94–0.99) contains 0.7 to, typically, 3 wt% Al2O3, but up to 8.4 wt% in the presence of sapphirine. Sapphirine (XMg=0.96–0.998, Be-free) shows the largest compositional variations,
with Si contents ranging from 1.7 to at least 2.1 atoms pfu, thereby clearly exceeding the 2:2:1 stoichiometry. The late-stage
talc contains up to 4 wt% Al2O3, 0.35 wt% Na2O and 0.6 wt% F; gedrite 1.1–2.9 wt% Na2O and up to 0.36 wt% F. The successive development within pyrope of alternative hydrous assemblages involving first enstatite
plus an Al-rich phase (kyanite, sapphirine, magnesiostaurolite) ± clinochlore, then a gedrite compositionally close to pyrope,
then talc plus an Al-rich phase (sapphirine, corundum), is a clear record of decompression. However, the temperature conditions
implied under the assumption of high H2O activity are 100 to 150 °C higher than, and so inconsistent with existing constraints on the decompression path. These constraints
are in particular the stability of talc + phengite in the matrix assemblage during decompression, and the absence of regional
evidence for a granulite-facies event. This inconsistency can only be alleviated if H2O activity inside the garnet megablast was (or became) considerably reduced with respect to that in the matrix. Fluid influx
into an opening fracture in garnet, sealing of the fracture by breakdown products of pyrope and continued evolution under
closed-system conditions may have led to increasing solute concentration and such low H2O activity within the garnet megablast, driving the microsystem toward fluid-absent conditions. Micrometre-size inclusions of Ca-sulfate and
crandallite-type compounds in minerals of these reactive areas may be evidence for such residual brines and suggest that these
were phosphate- and sulfate- rather than halide-dominated. This finding is additional evidence for the very local control
that fluid composition and H2O activity may have on the occurrence of granulite-facies assemblages, regardless of temperature. It highlights the role of
deformation (here fracturing) in triggering reactions in otherwise unreactive systems. It also shows how carefully inclusion-
to-host relationships have to be considered, post-growth reaction within the host being more common than hitherto reported.
Received: 4 February 1999 / Accepted: 24 August 2000 相似文献
10.
D. M. Ruscitto P. J. Wallace A. J. R. Kent 《Contributions to Mineralogy and Petrology》2011,162(1):109-132
Primitive chemical characteristics of high-Mg andesites (HMA) suggest equilibration with mantle wedge peridotite, and they
may form through either shallow, wet partial melting of the mantle or re-equilibration of slab melts migrating through the
wedge. We have re-examined a well-studied example of HMA from near Mt. Shasta, CA, because petrographic evidence for magma
mixing has stimulated a recent debate over whether HMA magmas have a mantle origin. We examined naturally quenched, glassy,
olivine-hosted (Fo87–94) melt inclusions from this locality and analyzed the samples by FTIR, LA-ICPMS, and electron probe. Compositions (uncorrected
for post-entrapment modification) are highly variable and can be divided into high-CaO (>10 wt%) melts only found in Fo > 91
olivines and low-CaO (<10 wt%) melts in Fo 87–94 olivine hosts. There is evidence for extensive post-entrapment modification
in many inclusions. High-CaO inclusions experienced 1.4–3.5 wt% FeOT loss through diffusive re-equilibration with the host olivine and 13–28 wt% post-entrapment olivine crystallization. Low-CaO
inclusions experienced 1–16 wt% olivine crystallization with <2 wt% FeOT loss experienced by inclusions in Fo > 90 olivines. Restored low-CaO melt inclusions are HMAs (57–61 wt% SiO2; 4.9–10.9 wt% MgO), whereas high-CaO inclusions are primitive basaltic andesites (PBA) (51–56 wt% SiO2; 9.8–15.1 wt% MgO). HMA and PBA inclusions have distinct trace element characteristics. Importantly, both types of inclusions
are volatile-rich, with maximum values in HMA and PBA melt inclusions of 3.5 and 5.6 wt% H2O, 830 and 2,900 ppm S, 1,590 and 2,580 ppm Cl, and 500 and 820 ppm CO2, respectively. PBA melts are comparable to experimental hydrous melts in equilibrium with harzburgite. Two-component mixing
between PBA and dacitic magma (59:41) is able to produce a primitive HMA composition, but the predicted mixture shows some
small but significant major and trace element discrepancies from published whole-rock analyses from the Shasta locality. An
alternative model that involves incorporation of xenocrysts (high-Mg olivine from PBA and pyroxenes from dacite) into a primary
(mantle-derived) HMA magma can explain the phenocryst and melt inclusion compositions but is difficult to evaluate quantitatively
because of the complex crystal populations. Our results suggest that a spectrum of mantle-derived melts, including both PBA
and HMA, may be produced beneath the Shasta region. Compositional similarities between Shasta parental melts and boninites
imply similar magma generation processes related to the presence of refractory harzburgite in the shallow mantle. 相似文献
11.
Séverine Moune François Holtz Roman E. Botcharnikov 《Contributions to Mineralogy and Petrology》2009,157(6):691-707
The solubility of sulphur in sulphide-saturated, H2O-bearing basaltic–andesitic and basaltic melts from Hekla volcano (Iceland) has been determined experimentally at 1,050°C,
300 and 200 MPa, and redox conditions with oxygen fugacity (logfO2) between QFM−1.2 and QFM+1.1 (QFM is a quartz–fayalite–magnetite oxygen buffer) in the systems containing various amounts
of S and H2O. The S content of the H2O-rich glasses saturated with pyrrhotite decreases from 2,500 ppm in basalt to 1,500 ppm in basaltic andesite at the investigated
conditions. Furthermore, the reduction of water content in the melt at pyrrhotite saturation and fixed T, P and redox conditions
leads to a decrease in S concentration from 2,500 to 1,400 ppm for basaltic experiments (for H2O decrease from 7.8 to 1.4 wt%) and from 1,500 to 900 ppm (for H2O decrease from 6.7 to 1.7 wt%) for basaltic andesitic experiments. Our experimental data, combined with silicate melt inclusion
investigations and the available models on sulphide saturation in mafic magmas, indicate that the parental basaltic melts
of Hekla were not saturated with respect to sulphide. During magmatic differentiation, the S content in the residual melts
increased and might have reached sulphide saturation with 2,500 ppm dissolved S. With further magma crystallization, the S
concentration in the melt was controlled by the sulphide saturation of the magma, decreasing from ~2,500 to 900 ppm S. 相似文献
12.
Marlon M. Jean John W. Shervais Sung-Hi Choi Samuel B. Mukasa 《Contributions to Mineralogy and Petrology》2010,159(1):113-136
The middle Jurassic Coast Range Ophiolite (CRO) is one of the most important tectonic elements in western California, cropping
out as tectonically dismembered elements that extend 700 km from south to north. The volcanic and plutonic sections are commonly
interpreted to represent a supra-subduction zone (SSZ) ophiolite, but models specifying a mid-ocean ridge origin have also
been proposed. These contrasting interpretations have distinctly different implications for the tectonic evolution of the
western Cordillera in the Jurassic. If an SSZ origin is confirmed, we can use the underlying mantle peridotites to elucidate
melt processes in the mantle wedge above the subduction zone. This study uses laser ablation–inductively coupled plasma–mass
spectrometry (LA–ICP–MS) to study pyroxenes in peridotites from four mantle sections in the CRO. Trace element signatures
of these pyroxenes record magmatic processes characteristic of both mid-ocean ridge and supra-subduction zone settings. Group
A clinopyroxene display enriched REE concentrations [e.g., Gd (0.938–1.663 ppm), Dy (1.79–3.24 ppm), Yb (1.216–2.047 ppm),
and Lu (0.168–0.290 ppm)], compared to Group B and C clinopyroxenes [e.g., Gd (0.048–0.055 ppm), Dy (0.114–0.225 ppm), Yb
(0.128–0.340 ppm), and Lu (0.022–0.05 ppm)]. These patterns are also evident in orthopyroxene. The differences between these
geochemical signatures could be a result of a heterogeneous upper mantle or different degrees of partial melting of the upper
mantle. It will be shown that CRO peridotites were generated through fractional melting. The shapes of REE patterns are consistent
with variable degrees of melting initiated within the garnet stability field. Models call for 3% dry partial melting of MORB-source
asthenosphere in the garnet lherzolite field for abyssal peridotites and 15–20% further partial melting in the spinel lherzolite
field, possibly by hydrous melting for SSZ peridotites. These geochemical variations and occurrence of both styles of melting
regimes within close spatial and temporal association suggest that certain segments of the CRO may represent oceanic lithosphere,
attached to a large-offset transform fault and that east-dipping, proto-Franciscan subduction may have been initiated along
this transform. 相似文献
13.
Sushmitha Baskar R. Baskar Natuschka Lee A. Kaushik P. K. Theophilus 《Environmental Geology》2008,56(2):237-243
The Borra caves, Vishakapatnam, India, can be described as a speleothem cave with significant amounts of unexplored microbial
mats in spring waters. Here, we present the first observations and hypotheses on the possible impact of the microorganisms
in these mats on the cave formation, focusing on their role on iron mineral precipitation. The spring waters (pH neutral 7.5–7.7)
contained dissolved metals like iron and the organic mat sludge (pH 7.0–7.3) had a TOC content of approximately 5.4 wt%. Geochemically,
the spring waters deep below the microbial mats contained Fe 369 ppb, Sr 198 ppb; and the organic mat sludge contained Mg
9 ppm, Fe 427 ppb, Zn 149 ppb, Sr 190 ppb. XRD observations displayed Fe minerals (dominantly hematite), minor amounts of
zinc gallium sulfide and nitrofuryl compounds. At least four groups of bacteria identified by direct microscopy and SEM-EDX
on the basis of morphology could be observed in all samples: Leptothrix-like organisms, entombed bacterial mineral sheaths, a few stalks of Gallionella-like organisms and some additional bacteria that could not be further identified. Leptothrix-like organisms contained 43.22–60.08 wt % Fe and the mineral precipitated near and around these bacteria (in the actual unaltered
samples on site) contained 30.76–45.22 wt% Fe as identified and quantified by SEM-EDX. This study indicates that the precipitation
of these iron-rich mats in the spring waters could be linked to the presence of abundant active communities of iron precipitating
bacteria at Borra caves, Vishakapatanam. 相似文献
14.
This paper documents the occurrence of large amounts of talc within a continental normal fault. The talc-in reaction is deformation-enhanced
and occurs by the interaction between dolostones and silica-rich hydrothermal fluids. In the high-strain, foliated fault core,
talc forms an interconnected network of oriented (001) lamellae, 200–300 nm thick, locally associated with minor tremolite
fibres, up to 300 nm in diameter. The talc structure is affected by several strain-induced defects, among which (001) interlayer
delamination that produces talc “sublamellae” down to 10–30 nm thick. Micro/nanostructural observations definitely point to
a predominant deformation mechanism of (001) frictional sliding, further enhanced by pervasive delamination that gives rise
to an almost infinite number of possible sliding surfaces. These effects have fundamental implications in fault mechanics,
resulting in significant fault weakening. 相似文献
15.
Edward S. Grew Nikolai N. Pertsev Stanislav Vrána Martin G. Yates Charles K. Shearer Michael Wiedenbeck 《Contributions to Mineralogy and Petrology》1998,131(1):22-38
Kornerupine, (□,Fe,Mg)(Mg,Fe,Al)9(Si,Al,B)5 (O,OH,F)22, has been reported with talc in rocks from six localities worldwide, but only at Chilapila Hill in the Lufilian Arc, Zambia
do textural relationships imply that kornerupine (Krn) equilibrated with talc (Tlc) during a prograde metamorphic event at
T≈ 640 °C, P≈ 13 kbar; a prograde Krn + Tlc assemblage has also been reported from Mautia Hill, Tanzania (P ≤ 13 kbar). In order to estimate possible constraints on the stability range for the kornerupine + talc paragenesis in nature,
we constructed a P-T diagram in the model system MgO-Al2O3-SiO2-H2O (MASH) for seven phases quartz (Qtz), B-free kornerupine sensu stricto, anthophyllite (Ath), chlorite (Chl), cordierite
(Crd), kyanite (Ky), and talc. The minimum pressure for Krn + Tlc + Ky stability in MASH is close to that for Ky + Tlc stability,
i.e., 6–8 kbar, at T≤ 780 °C. However, in the natural system, B2O3 and Na2O are major constituents in Krn and orthoamphibole (Oam), respectively, and dravitic tourmaline (Tur) is widespread. The critical
assemblage alternative to Krn + Tlc in nature is Tur + Oam. The upper pressure limit of Tur + Ath is determined by the upper
pressure for anthophyllite: 7.7–10.5 kbar at 682–794 °C in the MgO-SiO2-H2O system (Chernosky et al. 1985, Am Mineral 70:223–236), and is undoubtedly higher in the presence of Na2O, CaO, and Al2O3. At three of the six localities, talc is a retrograde phase; nonetheless, it possibly equilibrated with kornerupine on the
retrograde path or during a later metamorphic event at P-T conditions appropriate for Ky + Tlc. At the sixth locality (Mulvoj, southwestern Pamir Mountains, Tajikistan), Krn is found
in the same thin section as talc and kyanite and all three minerals formed during a prograde metamorphic event at T≥ 650 °C, P near 7 kbar. However, Krn is restricted to a lens 4 to 6 mm thick of phlogopite + anthophyllite + Tur and it does not touch
either talc or kyanite. A reaction relating the Mulvoj and Chilapila Hill (Krn + Tlc + Ky + Qtz + Tur) parageneses is calculated
from compositions in the Mulvoj rock to be 0.40Tur + 2.55Ath + 1.33H2O + 0.27F = Krn + 2.16Tlc + 0.36B2O3 + 0.02Rutile + 0.19Na2O + 0.17CaO. Given the difference in metamorphic pressures estimated for Mulvoj and Chilapila Hill, Krn + Tlc is inferred
to be favored by increasing pressure as well as by low Na2O and CaO contents. Some FeO, F, Fe2O3, and BeO are present in measurable amounts in at least one of the phases in the Mulvoj and Chilapila Hill whiteschists (e.g.,
Krn contains 0.24–0.67 wt% BeO), but the effect of these constituents is subordinate to that of Na2O, CaO and B2O3. The Krn + Tlc could be a more important assemblage in B-bearing whiteschists than has been reported to date, particularly
at pressures where orthoamphibole is no longer stable.
Received: 21 April 1997 / Accepted: 13 October 1997 相似文献
16.
《Applied Geochemistry》2006,21(7):1093-1108
Peña del Hierro is an abandoned mine site located in the catchment area of the Tinto river (Pyrite Belt, SW Spain). As leaching from the spoils affect the quality of the stream water, the waste dumps have been characterized for mineralogy, geochemistry and granulometry to obtain an estimate of the potential pollution. Waste rock dumps in Peña del Hierro are very heterogeneous and are mainly composed of acid volcanic tuffs > gossan > shales > roasted pyrite ashes > floated pyrite. The volcanic tuffs, the gossan and the shales coexist in the same piles. The roasted pyrite ashes and the floated pyrite form more homogeneous dumps. The dissolution of pyrite concentrated in pyrite ashes and floated pyrite units can generate acid mine drainage. Nevertheless, acid volcanic tuffs, which are rich in pyrite and have no neutralizing minerals, are the main source of these acidic effluents. Only muscovite might partially neutralize the acidity, but the dissolution of this mineral is too slow to compensate for acidity. The occurrence of jarosite in the <2 mm fraction indicates that extreme acid mine drainage occurs. The gossan and roasted pyrite ashes have high contents of trace elements. According to their concentration, As (46–1710 ppm), Pb (113–3455 ppm) and Hg (0–53) are some of the most important toxic trace elements in these wastes. In dumps mainly composed of volcanic tuffs most of the trace elements derive from the gossan mixed in the piles. Gossan is stable in an oxidizing environment, but acidic effluents (pH < 2) can dissolve Fe oxyhydroxides from them and release high amounts of trace elements to the stream water. This research contributes to estimating the production of acid mine drainage and the actual contamination risk of potentially toxic elements in soils and waters of this area, and could be the base for possible future mitigation actions in other areas affected by mining wastes. 相似文献
17.
Vein-hosted mesothermal stibnite-gold mineralisation at the Hillgrove Au-Sb mine in northeastern New South Wales has a halo
of veinlet and disseminated auriferous arsenopyrite and arsenian pyrite in metasedimentary and granitic host rocks. About
50–55% of the gold produced at Hillgrove occurs invisibly in arsenopyrite and pyrite. Gold losses of ∼20% into tailings are
due to this mineral chemical factor. From PIXE probe analyses, it has been found that arsenopyrite contains 255–1500 ppm Au
and pyrite 24–223 ppm Au, with Au contents of each mineral correlating moderately with As content. Arsenopyrite and pyrite
also contain anomalous values of Cu, Ag and Sb, whereas paragenetically later stibnite contains little invisible gold, but
minor Fe, As, Ag, Cu and Pb. The precipitation of invisible gold in arsenopyrite and pyrite by a possible (Fe, Au)3+= (As-S)3− substitution mechanism may have been facilitated by rapid, non-equilibrium conditions involving pressure decreases and wall
rock reaction (sulphidation, carbonatisation), as a prelude to the main stage of stibnite and gold deposition.
Received: 15 January 1999 / Accepted: 12 October 1999 相似文献
18.
Namin Koo Kwon-Rae Kim Youn-Jung Choi Sang-Hwan Lee Gary Owens Jeong-Gyu Kim 《Environmental Earth Sciences》2012,65(3):689-697
To determine the appropriate allocation of resources for the future restoration of the abandoned mining district of Kangwon
in Korea, identification of the main pollutants and the main sources discharging these pollutants is crucial. Therefore, a
2-year study was undertaken to quantify the amount of pollutants in the Uchen stream (a potential sink for contamination),
which runs through the district, and to determine the potential sources of these pollutants, including mine drainage and soil.
Arsenic (As) was the main pollutant in mine drainage and soils showing concentrations above the Korean regulated standard
levels of 50 μg L−1 and 50 mg kg−1 for water and soil, respectively. In addition, the pollution index (PI) showed that mine drainages were polluted by As to
a moderate (2 ≤ PI < 3) or strong (4 ≤ PI < 5) degree. Consequently, As load in mine drainage and soil contributed to increased
amounts of As in the stream. The As loads in mine drainages (11 and 587 g month−1 for mine adit 1 and 2, respectively) accounted for only 9% of the total As load to the stream (6,378 g month−1); and the influence of mine drainages on As contents in the stream was more reliant on the total volume of mine drainage
generated rather than the As concentration in the mine drainage. Approximately 91% of the As in the stream was derived from
the soils within the study area. 相似文献
19.
Garnet-bearing tonalitic porphyry from East Kunlun,Northeast Tibetan Plateau: implications for adakite and magmas from the MASH Zone 总被引:7,自引:0,他引:7
Chao Yuan Min Sun Wenjiao Xiao Simon Wilde Xianhua Li Xiaohan Liu Xiaoping Long Xiaoping Xia Kai Ye Jiliang Li 《International Journal of Earth Sciences》2009,98(6):1489-1510
A garnet-bearing tonalitic porphyry from the Achiq Kol area, northeast Tibetan Plateau has been dated by SHRIMP U-Pb zircon
techniques and gives a Late Triassic age of 213 ± 3 Ma. The porphyry contains phenocrysts of Ca-rich, Mn-poor garnet (CaO > 5 wt%;
MnO < 3 wt%), Al-rich hornblende (Al2O3 ~ 15.9 wt%), plagioclase and quartz, and pressure estimates for hornblende enclosing the garnet phenocrysts yield values
of 8–10 kbar, indicating a minimum pressure for the garnet. The rock has SiO2 of 60–63 wt%, low MgO (<2.0 wt%), K2O (<1.3 wt%), but high Al2O3 (>17 wt%) contents, and is metaluminous to slightly peraluminous (ACNK = 0.89–1.05). The rock samples are enriched in LILE
and LREE but depleted in Nb and Ti, showing typical features of subduction-related magmas. The relatively high Sr/Y (~38)
ratios and low HREE (Yb < 0.8 ppm) contents suggest that garnet is a residual phase, while suppressed crystallization of plagioclase
and lack of negative Eu anomalies indicate a high water fugacity in the magma. Nd–Sr isotope compositions of the rock (εNdT = −1.38 to −2.33; 87Sr/86Sri = 0.7065–0.7067) suggest that both mantle- and crust-derived materials were involved in the petrogenesis, which is consistent
with the reverse compositional zoning of plagioclase, interpreted to indicate magma mixing. Both garnet phenocrysts and their
ilmenite inclusions contain low MgO contents which, in combination with the oxygen isotope composition of garnet separates
(+6.23‰), suggests that these minerals formed in a lower crust-derived felsic melt probably in the MASH zone. Although the
rock samples are similar to adakitic rocks in many aspects, their moderate Sr contents (<260 ppm) and La/Yb ratios (mostly
16–21) are significantly lower than those of adakitic rocks. Because of high partition coefficients for Sr and LREE, fractionation
of apatite at an early stage in the evolution of the magma may have effectively decreased both Sr and LREE in the residual
melt. It is suggested that extensive crystallization of apatite as an early phase may prevent some arc magmas from evolving
into adakitic rocks even under high water fugacity. 相似文献
20.
Chalcophile element geochemistry and petrogenesis of high-Ti and low-Ti magmas in the Permian Emeishan large igneous province,SW China 总被引:4,自引:0,他引:4
Christina Yan Wang Mei-Fu Zhou Liang Qi 《Contributions to Mineralogy and Petrology》2011,161(2):237-254
Sulfide-poor mafic layered intrusions, sills/dykes and lava flows in the Funing region, SW China, are part of the ~260 Ma
Emeishan large igneous province. They belong to either a high-Ti group (TiO2 = 1.6–4.4 wt%) with elevated Ti/Y ratios (351–1,018), or a low-Ti group (TiO2 < 1.2 wt%) with low Ti/Y ratios (133–223). This study investigates the role of fractionation of olivine, chromite and sulfide
on the distributions of chalcophile elements, Ni, Cu and PGE, of the high-Ti and low-Ti group rocks at Funing. The high-Ti
group rocks contain 1.6–5.3 ppb Pt + Pd, 0.06–0.43 ppb Ir and 0.01–0.13 ppb Ru, and show relative constant (Cu/Pd)PM ratios (4.0–9.7) and a negative correlation between Ni/Pd and Cu/Ir ratios. Fractionated IPGE/PPGE patterns and very negative
Ru anomalies of the high-Ti group rocks, together with low Fo values (59–62 mol%) of olivine, indicate that the high-Ti magmas
may have experienced fractionation of olivine and chromite under S-undersaturated condition. Based on the PGE concentrations,
the low-Ti group rocks can be further divided into two subgroups; a high-PGE low-Ti subgroup and a low-PGE low-Ti subgroup.
The high-PGE low-Ti group rocks are rich in MgO (10–20 wt%), but Fo values of olivine from the rocks are low (74–76 mol%).
The rocks contain highly variable PGE (Pt + Pd = 1.7–88 ppb, Ir = 0.05–1.3 ppb), Ni (179 –1,380 ppm) and Cu (59–568 ppm).
They have Cu/Zr ratios >1, low (Y/Pd)PM ratios (0.2–7.1) and nearly constant (Cu/Pd)PM ratios (1.5–3.8). The even and parallel chalcophile element patterns of the high-PGE low-Ti subgroup rocks are likely a result
of olivine-dominated fractionation under S-undersaturated condition. The low-PGE low-Ti group rocks have low MgO (4.5–8.9 wt%)
and very poor PGE (Pt + Pd 0.5–1.6 ppb, Ir 0.004–0.02 ppb) with low Cu/Zr ratios (0.1–0.5), high (Y/Pd)PM (26–70) and variable (Cu/Pd)PM ratios (2.8–14). The trough-like chalcophile element patterns of the low-PGE low-Ti subgroup rocks indicate that the magmas
were sulfide saturation and sulfide melts were extracted from the magmas. The extracted sulfide melts might be potential Ni–Cu
sulfide ores at depth in the Funing region. 相似文献