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1.
Hun-Bok Jung Seong-Taek Yun Bernhard Mayer Soon-Oh Kim Seong-Sook Park Pyeong-Koo Lee 《Environmental Geology》2005,48(4-5):437-449
Transport and sediment–water partitioning of trace metals (Cr, Co, Fe, Pb, Cu, Ni, Zn, Cd) in acid mine drainage were studied
in two creeks in the Kwangyang Au–Ag mine area, southern part of Korea. Chemical analysis of stream waters and the weak acid
(0.1 N HCl) extraction, strong acid (HF–HNO3–HClO4) extraction, and sequential extraction of stream sediments were performed. Heavy metal pollution of sediments was higher
in Chonam-ri creek than in Sagok-ri creek, because there is a larger source of base metal sulfides in the ores and waste dump
upstream of Chonam-ri creek. The sediment–water distribution coefficients (K
d) for metals in both creeks were dependent on the water pH and decreased in the order Pb ≈ Al > Cu > Mn > Zn > Co > Ni ≈ Cd.
K
d values for Al, Cu and Zn were very sensitive to changes in pH. The results of sequential extraction indicated that among
non-residual fractions, Fe–Mn oxides are most important for retaining trace metals in the sediments. Therefore, the precipitation
of Fe(–Mn) oxides due to pH increase in downstream sites plays an important role in regulating the concentrations of dissolved
trace metals in both creeks. For Al, Co, Cu, Mn, Pb and Zn, the metal concentrations determined by 0.1 N HCl extraction (Korean
Standard Method for Soil Pollution) were almost identical to the cumulative concentrations determined for the first three
weakly-bound fractions (exchangeable + bound to carbonates + bound to Fe–Mn oxides) in the sequential extraction procedure.
This suggests that 0.1 N HCl extraction can be effectively used to assess the environmentally available and/or bioavailable
forms of trace metals in natural stream sediments. 相似文献
2.
Prof. Dr. M. Okrusch Prof. Dr. P. Richter Dipl. Min. A. Gürkan 《Mineralogy and Petrology》1981,29(1):9-31
Summary The Habachtal emerald deposit, Hohe Tauern, is composed of blackwall sequences of the type: serpentinite — talc schist — ±chlorite schist or actinolite schist — biotite schist —albite gneiss and/or micaschist. 2 serpentinites, 33 blackwall rocks, 9 micaschists, 10 albite gneisses, and 5 aplitic gneisses were analyzed for major elements, and for Li, Be, Cr, Ni, Zn, Zr, Sn, in 36 samples also for Sc, Cu, Rb, Sr, Cs, Ba, W. The blackwall formation is due to a metasomatic exchange involving a transfer of Mg from the serpentinite to the silicic country rock, and of Si, Ca, K, and Al from the country rock to the serpentinite. Some of the trace elements were also mobile: Compared to serpentinite, Li and Be were enriched in all the blackwall rocks, and Sn and Cs in the actinolite, chlorite, and biotite schists; Sr was concentrated in the dolomite-bearing talc schists, and Zn, Rb, and Ba predominantly in the biotite schists.
With 5 Figures 相似文献
Geochemie der Blackwall-Folgen in der Smaragd-Lagerstätte Habachtal, Hohe Tauern, Österreich. Teil 1: Darstellung der geochemischen Daten
Zusammenfassung Die Smaragd-Lagerstätte Habachtal, Hohe Tauern, besteht aus Blackwall-Folgen vom Typ: Serpentinit — Talkschiefer — ±Chloritschiefer oder Aktinolithschiefer — Biotitschiefer — Albitgneis und/oder Glimmerschiefer. Von 2 Serpentiniten, 33 Blackwall-Gesteinen, 9 Glimmerschiefern, 10 Albitgneisen und 5 Aplitgneisen wurden chemische Analysen der Hauptelemente und von Li, Be, Cr, Ni, Zn, Zr, Sn vorgelegt; 36 Proben wurden auch auf Sc, Cu, Rb, Sr, Cs, Ba und W analysiert. Die Blackwall-Bildung geht auf einen metasomatischen Austausch zurück, bei dem Mg aus dem Serpentinit ins Nebengestein, Si, Ca, K und Al aus dem Nebengestein in den Serpentinit transportiert wurden. Daneben waren auch einige Spurenelemente mobil: Im Vergleich zum Serpentinit wurden Li und Be in allen Blackwall-Gesteinen, Sn und Cs in den Aktinolith-, Chlorit- und Biotitschiefern angereichert; Sr wurde(n) in den dolomitführenden Talkschiefern, Zn, Rb und Ba hauptsächlich in den Biotitschiefern konzentriert.
With 5 Figures 相似文献
3.
Trace element variations in olivine phenocrysts from Ugandan potassic rocks as clues to the chemical characteristics of parental magmas 总被引:2,自引:0,他引:2
Stephen F. Foley Dorrit E. Jacob Hugh St. C. O’Neill 《Contributions to Mineralogy and Petrology》2011,162(1):1-20
Olivine phenocrysts in ugandite and leucite basanite from the western branch of the East African Rift have been analysed for
up to 34 trace elements by Laser-ICP-MS with detection limits as low as 1 ppb. A combination of point analyses with varying
ablation crater diameters and line scans allow the identification of subtle zonations from core to rim, as well as characterization
of the chemical effects of contamination along cracks. Trace element concentrations are remarkably uniform between large and
small phenocrysts; fractionated leucite basanites (Mg# 59) have higher D
Ca and D
Al, and less fractionated LREE/HREE than MgO-rich ugandites (Mg# 75–80). Minor zonation is seen in elements with cation charges
from 5+ to 2+ (P, Ti, Zr, Cr, Al, Sc, V, Cu, Mn, Ni) and show correlation between Ti and Al, but not P. Early phenocryst cores
with high Li or Ni, low Mn, or enrichments in many trace elements can be identified, whereas xenocrysts have exceptionally
low Na, Cr, Ti, V and Co. Partition coefficients for Ni are 31–35, less than in lamproites, with which they demonstrate an
approximately linear correlation with K2O content, K2O/Al2O3 and K2O/Na2O of the melt, but none with SiO2 content or Mg#. D-values for Cr, Mn and Co overlap with those of basalts, whereas those for Sc (0.011–0.018), Zn (0.44–0.49) and Ga (0.006–0.007)
are lower. D
V of various potassic rocks (0.015 in the Ugandan rocks) confirms the dependence on fO2 calibrated by the Fe3+/(Fe3++Fe2+) of spinels; the Ugandan potassic rocks crystallized at fO2 = FMQ to FMQ + 1. The ugandite olivines have some trace element characteristics reminiscent of those in metasomatized Kaapvaal
peridotites, but not ocean islands. Line scan analyses are contaminated in Al, Ca, Cu, Ga, Sr, Zr, Nb, La and Ce, elements
that are also concentrated in microcracks between subgrains, indicating smearing out during polishing, and demonstrating that
large spot analyses produce the best results. 相似文献
4.
Surface slices of 20 sediment cores, off southwestern Taiwan, and bed sediment of River Kaoping were measured for major and
trace elements (Al, As, Ca, Cd, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Si, Ti, V, and Zn) to evaluate the geochemical
processes responsible for their distribution, including elemental contamination. Major element/Al ratio and mean grain size
indicate quartz-dominated, coarse grained sediments that likely derived from sedimentary rocks of Taiwan and upper crust of
Yangtze Craton. Bi-plot of SiO2 versus Fe2O3T suggests the possible iron enrichment in sediments of slag dumping sites. Highest concentrations of Cr, Mn, P, S, and Zn
found in sediments of dumping sites support this. Correlation analysis shows dual associations, detrital and organic carbon,
for Cr, P, S, and V with the latter association typical for sediments in dumping sites. Normalization of trace elements to
Al indicates high enrichment factors (>2) for As, Cd, Pb, and Zn, revealing contamination. Factor analysis extracted four
geochemical associations with the principal factor accounted for 25.1% of the total variance and identifies the combined effects
of dumped iron and steel slag-induced C–S–Fe relationship owing to authigenic precipitation of Fe–Mn oxyhydroxides and/or
metal sulfides, and organic matter complexation of Fe, Mn, Ca, Cr, P, and V. Factors 2, 3, and 4 reveal detrital association
(Ti, Al, Ni, Pb, Cu, and V), effect of sea salt (Cl, Mg, Na, and K) and anthropogenic component (As and Zn)-carbonate link,
respectively, in the investigated sediments. 相似文献
5.
Summary The timing of Zn–Pb mineralization hosted by early dolomitized lagoonal limestones (Crest facies) at Bleiberg (Carinthia,
Austria) has been constrained using Sr-isotopes. This late stage Zn–Pb mineralization is a special feature of the Bleiberg
deposit. Samples of the mineralized Crest facies are characterized by higher concentrations of minor and trace elements (except
Ba and Sr) compared to samples from the weakly mineralized Wetterstein limestone of the lagoonal facies. The samples from
the Crest facies indicate that a fluid with a minimum 87Sr/86Sr ratio of 0.7083 reacted at 210±30 Ma with carbonate rocks having 87Sr/86Sr ratios of approximately 0.7077 during a late stage of ore formation. The 87Sr/86Sr ratios correlate with the Mn and Cl concentrations. Lead isotope data of whole rock samples of Bleiberg yielded an isochron
age of 180±40 Ma. They furthermore confirm the presence of two types of common lead; an isotopically distinct ore lead component
is present within and close to the ore bodies. The other common Pb component is present in host rocks and in gangue minerals
and is distinguished from the ore lead by lower 207Pb/204Pb and 208Pb/204Pb ratios. The Sr and the Pb ages are consistent with geological evidence indicating a Triassic age of Pb–Zn mineralization
and support genetic models emphasizing the role of bacteriogenic sulfate reduction at low temperatures prior to subsidence
and burial. Elevated 87Sr/86Sr values (>0.7080) of gangue minerals indicate an epigenetic origin of strontium. Our results are consistent with a genetic
model postulating formation of the ore-bearing hydrothermal fluids “at depth” where they leached lead from pre-Upper Carboniferous
basement rocks. 相似文献
6.
A critical study of 311 published WR chemical analyses, isotopic and mineral chemistry of anorthosites and associated rocks
from eight Proterozoic massif anorthosite complexes of India, North America and Norway indicates marked similarities in mineralogy
and chemistry among similar rock types. The anorthosite and mafic-leucomafic rocks (e.g., leuconorite, leucogabbro, leucotroctolite,
anorthositic gabbro, gabbroic anorthosite, etc.) constituting the major part of the massifs are characterized by higher Na2O + K2O, Al2O3, SiO2, Mg# and Sr contents, low in plagioclase incompatible elements and REE with positive Eu anomalies. Their δ
18O‰ (5.7–7.5), initial 87Sr/86Sr (0.7034–0.7066) and ɛ
Nd values (+1.14 to +5.5) suggest a depleted mantle origin. The Fe-rich dioritic rocks occurring at the margin of massifs have
isotopic, chemical and mineral composition more close to anorthosite-mafic-leucomafic rocks. However, there is a gradual decrease
in plagioclase content, An content of plagioclase and XMg of orthopyroxene, and an increase in mafic silicates, oxide minerals content, plagioclase incompatible elements and REE from
anorthosite-mafic-leucomafic rocks to Fe-rich dioritic rocks. The Fe-rich dioritic rocks are interpreted as residual melt
from mantle derived high-Al gabbro melt, which produced the anorthosite and mafic-leucomafic rocks. Mineralogically and chemically,
the K-rich felsic rocks are distinct from anorthosite-mafic-leucomafic-Fe-rich dioritic suite. They have higher δ
18O values (6.8–10.8‰) and initial 87Sr/86Sr (0.7067–0.7104). By contrast, the K-rich felsic suites are products of melting of crustal precursors. 相似文献
7.
Trace element and isotope geochemistry of depleted peridotites from an N-MORB type ophiolite (Internal Liguride,N. Italy) 总被引:6,自引:0,他引:6
E. Rampone A. W. Hofmann G. B. Piccardo R. Vannucci P. Bottazzi L. Ottolini 《Contributions to Mineralogy and Petrology》1996,123(1):61-76
Mantle peridotites of the Internal Liguride (IL) units (Northern Apennines) constitute a rare example of the depleted lithosphere
of the Jurassic Ligurian Tethys. Detailed chemical (ICP-MS and SIMS techniques) and isotopic investigations on very fresh
samples have been performed with the major aim to constrain the timing and mechanism of their evolution and to furnish new
data for the geodynamic interpretation. The data are also useful to discuss some general geochemical aspects of oceanic-type
mantle. The studied samples consist of clinopyroxene-poor spinel lherzolites, showing incipient re-equilibration in the plagioclase-facies
stability field. The spinel-facies assemblage records high (asthenospheric) equilibration temperatures (1150–1250° C). Whole
rocks, and constituent clinopyroxenes, show a decoupling between severe depletion in highly incompatible elements [light rare
earth elements (LREE), Sr, Zr, Na, Ti] and less pronounced depletion in moderate incompatible elements (Ca, Al, Sc, V). Bulk
rocks also display a relatively strong M(middle)REE/H(heavy)REE fractionation. These compositional features indicate low-degree
(<10%) fractional melting, which presumably started in the garnet stability field, as the most suitable depletion mechanism.
In this respect, the IL ultramafics show strong similarity to abyssal peridotites. The Sr and Nd isotopic compositions, determined
on carefully handpicked clinopyroxene separates, indicate an extremely depleted signature (87Sr/86Sr=0.702203–0.702285; 143Nd/144Nd=0.513619–0.513775). The Sm/Nd model ages suggest that the IL peridotites melted most likely during Permian times. They
could record, therefore, the early upwelling and melting of mid ocean ridge basalt (MORB) type asthenosphere, in response
to the onset of extensional mechanisms which led to the opening of the Western Tethys. They subsequently cooled and experienced
a composite subsolidus evolution testified by multiple episodes of gabbroic intrusions and HT-LP retrograde metamorphic re-equilibration, prior to their emplacement on the sea floor. The trace element chemistry of IL peridotites
also provides useful information about the composition of oceanic-type mantle. The most important feature concerns the occurrence
of Sr and Zr negative anomalies (relative to “adjacent” REE) in both clinopyroxenes and bulk rocks. We suggest that such anomalies
reflect changes in the relative magnitude of Sr, Zr and REE partition coefficients, depending on the specific melting conditions.
Received: 15 February 1995/Accepted: 4 August 1995 相似文献
8.
Size fractionation of ~40 major and trace elements (TE) in peat soil solutions from the Tverskaya region (Russia) has been
studied using frontal filtration and ultrafiltration through a progressively decreasing pore size (5, 2.5, 0.22 μm, 100, 10,
5, and 1 kD) and in situ dialysis through 6–8 and 1 kD membranes with subsequent analysis by ICP-MS. In (ultra) filter-passed permeates and dialysates
of soil solutions, Fe, Al, and organic carbon (OC) are well correlated, indicating the presence of mixed organo-mineral colloids.
All major anions and silica are present in “dissolved” forms passed through 1 kD membrane. According to their behavior during
filtration and dialysis and association with mineral or organic components, three groups of elements can be distinguished:
(i) species that are weakly affected by size separation operations and largely (>50–80%) present in the form of dissolved
inorganic species (Ca, Mg, Li, Na, K, Sr, Ba, Rb, Cs, As, Mn) with some proportion of small (1–10 kD) organic complexes (Ca,
Mg, Sr, Ba), (ii) biologically essential elements (Co, Ni, Zn, Cu, Cd) mainly present in the fraction smaller than 1 kD and
known to form strong organic complexes with fulvic acids, and, (iii) elements strongly associated with aluminum, iron and
OC in all ultrafiltrates and dialysates with 30–50% being concentrated in large (>10 kD) colloids (Ga, Y, REEs, Pb, Cd, V,
Nb, Sn, Ti, Zr, Hf, Th, U). For most trace metals, the proportion in the colloidal fraction correlates with their first hydrolysis
constant. This implies a strong control of negatively charged oxygen donors present in inorganic/organic colloids on TE distribution
between aqueous solution and colloid particles. It is suggested that these colloids are formed during plant uptake of Al,
Fe, and TE from mineral matrix of deep soil horizons and their subsequent release in surface horizons after litter degradation
and oxygenation on redox or acid/base fronts. Dissolved organic matter stabilizes Al/Fe colloids and thus enhances trace elements
transport in soil solutions. 相似文献
9.
Nodules of various compositions, including ferromanganese nodules, have been found in bottom sediments of an artificial reservoir
in the central Altai Territory. The nodules were formed in the alkaline environment against the background of a high carbonate
content and saturation with oxygen. The rate of nodule growth is no less than 1.7–1.8 mm/yr and the pH value of water varies
from 8.0 to 9.7. Fe and Mn contents in soil and loam of the drainage area are lower than the global clarke value, whereas
Ca, K, and Na contents are much higher. The main mass of bottom sediments in the reservoir is markedly enriched in Cd, Mg,
Mn, Sr, Ni, Cr, Sb, V, and Pb, but they are depleted in Cu, Mo, Zn, and Li, relative to the soil and loam. Elements in ferromanganese
nodules are arranged in the following way in terms of the decreasing concentration coefficient: Mn (27) > Ba (13.4) > Co (10.7)
> Mo (9.2) > Cd (5.35) > Ni (3.88) > V (3.52) > Cu (3.3) > Fe (3.2) > Sb (2.17) > Sr (2.04) > Pb (1.5) > Zn (1.43) > Cr (1.1)
> Li (0.78) > Mg (0.75) > Na (0.69) > K (0.67) > Ca (0.51). The microelemental composition of nodules in the reservoir qualitatively
fits the composition of ferromanganese nodules in seas and oceans. However, the contents of major ore elements (Ni, Cu, Co,
Zn, Pb, Mo, and V) in ferromanganese nodules from the World Ocean are much higher than in nodules from the examined reservoir. 相似文献
10.
Background concentrations of heavy metals in aquatic bryophytes used for biomonitoring in basaltic areas (a case study from central France) 总被引:1,自引:0,他引:1
Studies were made of the aquatic bryophytes Fontinalis antipyretica Hedw., Platyhypnidium rusciforme (Neck.)Fleisch and Chiloscyphus sp. (Hoffm.)Dum. from streams embedded in basaltic rocks (Le Puy, central France). Water from these streams possessed elevated
levels of Cu, Zn, Sr, V, Ba, Ni and Co, reflecting the geochemistry of the basalts, a basic type of igneous rocks containing
elevated levels of these elements. The concentration of elements in bryophytes is correlated to the chemical composition of
water of their sampling sites. Contents of trace elements in plants were higher than background values. The elevated levels
of these elements possibly caused disturbances in the ionic equilibrium within the bryophytes. The molar ratio between contents
of Ca and Mg in water (from 0.44 to 1) was different from that typical for natural water.
Received: 16 September 1998 · Accepted: 17 December 1998 相似文献
11.
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
12.
经历反复埋藏暴露演化过程的河流阶地样品,难以用常规方法将原生宇宙核素10Be、26Al有效分离。本文在前人实验方法基础上,使用人工挑选、磁选仪分选及酸洗方法,分离样品中碳酸盐、含铁矿物及大气生成的10Be,进一步优化了石英提纯实验流程。结果表明:长度为9 cm、内径为1 cm的阴离子交换树脂装置匹配4 mol/L氢氟酸淋滤液,可将B、Mg、Ca、Cr、Fe、Mn、Ni、Ti和Be、Al有效分离,Be、Al回收率分别可达95.7%、85.7%。阳离子交换树脂能有效分离Be、Al,两元素回收率均达到85%。获得10Be/9Be和26Al/27Al流程空白分别为2.19×10-15和1.63×10-15。优化后的实验方法显著提高了河流阶地样品中原生宇宙核素10Be、26Al的纯化效率,且10Be/9Be和26Al/27Al流程空白数值与国内外实验室具有可比性。采用本方法获得了成都平原冲积物10Be、26Al暴露年龄分别是76.36±9.51 ka和69.44±14.13 ka,为评价龙门山前缘隐伏断裂构造特征和活动性提供了年代学依据。 相似文献
13.
A. I. Grabezhev 《Geology of Ore Deposits》2010,52(2):138-153
The Early Devonian Gumeshevo deposit is one of the largest ore objects pertaining to the dioritic model of the porphyry copper
system paragenetically related to the low-K quartz diorite island-arc complex. The (87Sr/86Sr)t and (ɛNd)t of quartz diorite calculated for t = 390 Ma are 0.7038–0.7045 and 5.0–5.1, respectively, testifying to a large contribution of the mantle component to the composition
of this rock. The contents of typomorphic trace elements (ppm) are as follows: 30–48 REE sum, 5–10 Rb, 9–15 Y, and 1–2 Nb.
The REE pattern is devoid of Eu anomaly. Endoskarn of low-temperature and highly oxidized amphibole-epidote-garnet facies
is surrounded by the outer epidosite zone. Widespread retrograde metasomatism is expressed in replacement of exoskarn and
marble with silicate (chlorite, talc, tremolite)-magnetite-quartz-carbonate mineral assemblage. The 87Sr/86Sr ratios of epidote in endoskarn and carbonate in retrograde metasomatic rocks (0.7054–0.7058 and 0.7053–0.7065, respectively)
are intermediate between the Sr isotope ratios of quartz dioritic rocks and marble (87Sr/86Sr = 0.70784 ± 2). Isotopic parameters of the fluid equilibrated with silicates of skarn and retrograde metasomatic rocks
replacing exoskarn at 400°C are δ18O = +7.4 to +8.5‰ and δD = −49 to −61‰ (relative to SMOW). The δ13C and δ18O of carbonates in retrograde metasomatic rocks after marble are −5.3 to +0.6 (relative to PDB) and +13.0 to +20.2% (relative
to SMOW), respectively. Sulfidation completes metasomatism, nonuniformly superimposed on all metasomatic rocks and marbles
with formation of orebodies, including massive sulfide ore. The δ34S of sulfides is 0 to 2‰ (relative to CDT);87Sr/86Sr of calcite from the late calcite-pyrite assemblage replacing marble is 0.704134 ± 6. The δ13C and 87Sr/86Sr of postore veined carbonates correlate positively (r = 0.98; n = 6). The regression line extends to the marble field. Its opposite end corresponds to magmatic (in terms of Bowman, 1998b)
calcite with minimal δ13C, δ18O, and 87Sr/86Sr values (−6.9 ‰, +6.7‰, and 0.70378 ± 4, respectively). The aforementioned isotopic data show that magmatic fluid was supplied
during all stages of mineral formation and interacted with marble and other rocks, changing its Sr, C, and O isotopic compositions.
This confirms the earlier established redistribution of major elements and REE in the process of metasomatism. A contribution
of meteoric and metamorphic water is often established in quartz from postore veins. 相似文献
14.
A multivariate statistical analysis was carried out with log-transformed values of Cu, Ni, Co, Pb, Zn, Ag, Cr, Mn, Ca, and Sr in several sets of samples collected across the mineralized base metal zone in sheared soda granite, feldspathic schist, and chlorite schist from the central section of Mosaboni Mine of the famous Singhbhum Copper Belt of eastern India. Linear correlation coefficient matrices of two sets of ore samples (>0.5% Cu)—one from levels 18 and 21 and the other from levels 25 and 28—indicate two well-defined and distinct clusters comprising Cu, Ni, Co, Pb, and Zn on one hand and Ca, Sr, and Mn on the other. Varimax-rotatedR-mode factor analysis of two above-noted sample sets, taken along with available geologic information, indicates that over 80% of the variability in data matrices for 9–10 elements can be accounted for by four distinct processes: (a) an early phase of copper mineralization which apparently replaced Mn, Ca, and Sr in the host rock; (b) a silicate-cum-oxide phase of crystallization/recrystallization of host rock; (c) remobilization of sulfide-forming ore elements (Cu, Ni, Co, Pb, and Zn); and (d) a phase of mineralization of Ag which appears to have replaced Cr, Ca and Cu. Process (c) was quantitatively most important. Factor score studies are suggestive of preferred introduction of Ni, Co, Pb, and Zn along central parts of preexisting copper-mineralized zones. 相似文献
15.
Geochemical characteristics of Cenozoic high-K igneous rocks from Liuhe-Xiangduo area, eastern Tibet
The major elements, trace elements and Nd-Sr isotopic composition of Cenozoic high-K igneous rocks and mafic deep-derived enclaves from the Liuhe-Xiangduo area, eastern Tibet, indicate the high-K igneous rocks are characterized as being enriched in Ca (CaO= 1.20% - 8.80% ), alkali (Na2O K2O= 3.47% - 10.65% ), especially K (K2O up to 5.96% ) and depleted in Ti (TiO2= 0.27% - 1.50% ). Their REE contents are very high (REE= 91.29 - 231.11 μg/g). Their REE distribution patterns are of the right-inclined type, characterized by intense LREE enrichment [(La/Yb)N= 7.44 - 15.73 ]. The rocks are distinctly enriched in Rb, Sr and Ba ( 46.3 -316 μg/g, 349-1220 μg/g and 386-2394 μg/g, respectively), high in U and Th ( 1.17 - 8.10 μg/g and 2.58 - 27.0 μg/g, respectively), moderate in Zr and Hf ( 87.5 -241 μg/g and 2.83 - 7.52 μg/g, respectively), and depleted in Nb and Ta ( 4.81 - 16.8 μg/g and 0.332 - 1.04 μg/g, respectively). In the primitive mantle-normalized incompatible element spidergram, U, K, Sr and Hf show positive anomalies, whereas Th, Nb, Ta, P, and Ti show negative anomalies. The rocks are strongly depleted in Cr and Ni ( 21.4 -1470 μg/g and 7.79 -562 μg/g, respectively), and their transition element distribution curves are obviously of type-W. The ( 87 Sr/ 86 Sr)i ratios range from 0.704184 to 0.707539 ; ( 143 Nd / 144 Nd)i from 0.512265 to 0.512564 ; and ε Nd (t) from -6.3 to -0.4 . These geochemical features might suggest that the potential source of the high-K igneous rocks in the Liuhe-Xiangduo area is similar to the EM2, which may be similar to the material enriched K that is located under the crust-mantle mixed layer. The mafic deep-derived enclaves in the high-K igneous rocks belong to chance xenoliths. Their ( 87 Sr/ 86 Sr)i ratios range from 0.706314 to 0.707198 ; ( 143 Nd / 144 Nd)i from 0.512947 to 0.513046 ; and ε Nd (t) from 7.0 to 9.0 . These geochemical features might indicate that the enclaves probably came from the depleted mantle. The P-T conditions of the enclaves also showed that the enclaves are middle-lower crust metamorphic rocks, which were accidentally captured at 20-50 km level by rapidly entrained high-K magma, whose source is over 50 km in depth. 相似文献
16.
Alteration zoning and primary geochemical dispersion at the Bronzewing lode-gold deposit, Western Australia 总被引:1,自引:0,他引:1
The Late Archaean Bronzewing lode-gold deposit is in the Yandal greenstone belt, Western Australia. It is located in a 500-m-wide,
N–S trending, structural corridor consisting of an anastomosing set of brittle–ductile shear zones and is chiefly hosted by
tholeiitic basalts, which are metamorphosed at mid- to upper-greenschist facies. Syn-peak metamorphic alteration surround
all ore bodies, and alteration extends laterally for ≤80 m from individual mineralised structures. Individual alteration haloes
partially overlap and form a >1.5-km-long and ≤300-m-wide domain. The alteration sequence, studied here at 140 m below the
present undisturbed surface, comprises distal calcite–chlorite–albite–quartz, intermediate calcite–dolomite–chlorite–muscovite–albite–quartz
and proximal ankerite–dolomite–muscovite–albite–quartz–pyrite zones. Mass transfer calculations indicate that chemical changes
during alteration include enrichment of Ag, Au, Ba, Bi, CO2, K, Rb, S, Sb, Te and W, and depletion of Na, Sr and Y. The elements Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, P, Ti, V, Zn and Zr
are immobile. The degree of chemical change increases with proximity to gold ore zones. In addition, abundant quartz veins
indicate substantial silica mobility during the hydrothermal event, although there is no large relative silica loss or gain
in the host rock. The broadest anomaly surrounding the Bronzewing gold deposit is defined by tellurium (>10 ppb) which, if
it is a hydrothermal anomaly, extends beyond the 400 × 600 m study area. Anomalous values for CO2, K, Rb and Sb also define wider zones than does anomalous gold (>4 ppb), although even the lithogeochemical gold anomaly
extends across strike for as much as 80 m away from ore and >600 m along the N–S strike of the shear zone corridor. Also carbonation
and sericitisation indices outline large exploration targets at the Bronzewing deposit. Sericitisation indices define anomalies
that extend for tens of metres beyond visible potassic alteration, whereas the anomalies defined by the carbonation indices
do not extend beyond visible carbonation. None of the individual alteration indices or pathfinder elements are able to define
consistent gradients towards ore. However, the respective dimensions of individual geochemical anomalies can be used as an
extensive, although stepwise, vector towards ore. This sequence is, from species with broadest dispersion first, as follows:
Te > CO2/Ca ≥ Sb, 3K/Al, Rb/Ti ≥ Au, W > Y/Ti (depletion) > Ag ≥ Bronzewing ore.
Received: 25 October 1999 / Accepted: 11 May 2000 相似文献
17.
First-order factors controlling the textural and chemical evolution of metamorphic rocks are bulk composition and pressure–temperature–time
(P–T–t) path. Although it is common to assume that major element bulk composition does not change during regional metamorphism,
rocks with reaction textures such as corona structures record evidence for major changes in effective bulk composition (EBC) and therefore provide significant insight into the scale, pathways, and mechanisms of element transport
during metamorphism. Quantifying changes in EBC is essential for petrologic applications such as calculation of phase diagrams
(pseudosections). The progressive growth of complex corona structures on garnet and Al2SiO5 porphyroblasts in orthoamphibole-cordierite gneiss Thor-Odin dome (British Columbia, Canada) reduced the EBC volume of the
rock during metamorphism and therefore had a dramatic effect on the evolution of the stable mineral assemblage. These rocks
contain a chemical and textural record of metamorphic reactions and preserve 3D networks (reaction pathways) connecting corona
structures. These coronal networks record long (>cm) length scales of localized element transport during metamorphism. P–T, T–X, and P–X pseudosections are used to investigate the control of effective bulk composition on phase assemblage evolution. Despite textural
complexity and evidence for disequilibrium, mineral assemblages and compositions were successfully modeled and peak metamorphic
conditions estimated at 750°C and 9 kbar. These results illustrate how textural and chemical changes during metamorphism can
be evaluated using an integrated petrographic and pseudosection approach, highlight the importance of effective bulk composition
choice for application of phase equilibria methods in metamorphic rocks, and show how corona structures can be used to understand
the scale of compositional change and element transport during metamorphism. 相似文献
18.
The Anqing-Lujiang quartz syenite rock belt consists of the Huangmeijian, Chengshan and Dalongshan composite batholiths which
intruded into the Mesozoic strata. The country rocks were subjected to thermal contact metamorphism with little sign of folding
and regional metamorphism. The rock belt is Late Yenshanian in age with a Rb-Sr isochron age of 135 Ma.
Major rock types are quartz syenite and, to a lesser extent, syenite porphyry and alkali feldspar granite. Rock-forming minerals
are dominantly potash feldspar (more than 50%) and lesser amounts of plagioclase and quartz. Mafic minerals, mostly Mg-biotite
with lesser amounts of amphibole and pyroxene, are rare. Occasionally, alkalic mafic minerals (aegirine, riebeckite) are found.
Characteristic accessary minerals of the earlier intrusives are magnetite, sphene and apatite and those of the later intrusives
are ilmenite and zircon. Typologic distribution and evolutionary trend of zircon population are very similar to those of granites
of mantle origin as suggested by Pupin, J. P.
Petrochemically, the rock belt is poor in Ca but rich in alkali and Al with Na2O+K2O > 10%. It belongs to the K-Na transitional series, with a high alkalinity ratio (A. R. = 3–7) and a K /Na (atom) ratio close
to unity. Rocks in the belt are rich in REE which tends to decrease from the early to the late stage, belonging to LREE type.
The initial Sr ratio is 0.7078–0.7064.
The rock belt is the Mesozoic anorogenic product of alkalic magmatic activity from a deep-seated source. According to a mantle-crust
mixing model for Sr and Pb isotopes, it is estimated that 60.2–53.8% of the materials has been derived from the mantle. Additionally,
its rich alkali, poor water content and anorogenic characteristics suggest that the belt is similar to the A-type granites. 相似文献
19.
Trace elements contamination of agricultural soils affected by sulphide exploitation (Iberian Pyrite Belt,Sw Spain) 总被引:1,自引:0,他引:1
Agricultural soils of the Riotinto mining area (Iberian Pyrite Belt) have been studied to assess the degree of pollution by
trace elements as a consequence of the extraction and treatment of sulphides. Fifteen soil samples were collected and analysed
by ICP-OES and INAA for 51 elements. Chemical analyses showed an As–Cu–Pb–Zn association related with the mineralisation of
the Iberian Pyrite Belt. Concentrations were 19–994 mg kg−1 for As, 41–4,890 mg kg−1 for Pb, 95–897 mg kg−1 for Zn and of 27–1,160 mg kg−1 for Cu. Most of the samples displayed concentrations of these elements higher than the 90th percentile of the corresponding
geological dominium, which suggests an anthropogenic input besides the bedrock influence. Samples collected from sediments
were more contaminated than leptosols because they were polluted by leachates or by mining spills coming from the waste rock
piles. The weathering of the bedrock is responsible for high concentrations in Co, Cr and Ni, but an anthropogenic input,
such as wind-blown dust, seems to be indicative of the high content of As, Cu, Pb and Zn in leptosols. The metal partitioning
patterns show that most trace elements are associated with Fe amorphous oxy-hydroxides, or take part of the residual fraction.
According to the results obtained, the following mobility sequence is proposed for major and minor elements: Mn, Pb, Cd, > Zn,
Cu > Ni > As > Fe > Cr. The high mobility of Pb, Cu and Zn involve an environmental risk in this area, even in soils where
the concentrations are not so high. 相似文献
20.
Petrographic, electron microprobe, and bulk-rock geochemical analyses indicate that the distribution and composition of ferromagnesian
silicates (biotite, garnet, and staurolite) in and adjacent to the metamorphosed Bleikvassli Zn–Pb–(Cu) volcanogenic massive
sulfide deposit, Norway, are dependent upon the competing effects of f O2–f S2 and host-rock composition. The enrichment in magnesium content of these silicates within the orebody and at distances of
as much as 5–10 m away is due to the increased f O2 and f S2 conditions imposed on the silicates in zones subject to minor hydrothermal alteration during regional metamorphism. Alternatively,
within pelitic country rocks at distances >5–10 m from ore, the host-rock chemistry controls the composition of metamorphic
silicate minerals. Also, country rocks within a few meters of ore are distinguished by the common presence of zinc-bearing
staurolite (up to 9 wt% ZnO) coexisting with biotite ± garnet. Rocks in the Bleikvassli deposit were hydrothermally enriched
in zinc and fluorine prior to metamorphism. The fluorine resides mainly in biotite, which is an additional contributing factor
to the magnesium enrichment of that mineral due to Fe2+–F avoidance. Our inference that the sulfidation–oxidation halo around the Bleikvassli ore deposit is only meters in width
contrasts with the view of Maiga (1983), who proposed the effects of sulfidation could be identified at distances >159 m from
ore. It is evident that the delineation of a sulfidation–oxidation halo bordering a metamorphosed massive sulfide deposit
must be done carefully in order to discriminate between the effects due to variations in primary rock composition versus those
resulting from a sulfur and oxygen fugacity gradient between the massive sulfides and the sulfur-poor country rocks.
Received: 1 March 1998 / Accepted: 3 May 2000 相似文献