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1.
Complexation of Si in hydrothermal systems 总被引：1，自引：1，他引：0
The Au-SiO2 and Sn-SiO2 complexes have been experimentally calibrated at varying temperature,silica comcentration and pH: Au^ H2SiO4^-=AuH3SiO4 lgK=-1.65436 9611.21/T; Sn^4 4H3SiO4^-=Sn(H3SiO4)4 lgK200℃=42.73 Compared with Au-Cl,Au-HS and Sn-OH complexes,AuH3SiO4 and Sn(H3SiO4)4complexes can be recognized as the dominant transport forms in Si-bearing solurtions under pH and Eh conditions of general interest.The decrease of SiO2 concentration and oxygen fugacity would reverse the direction of dissolution-complexing reactions,resulting in the precipitation of gold and silica,as well as cassiterite and silica.This study illustrates the significance of SiO2-complexation in hydrothermal solutions for gold,tin and other metallizations. 相似文献
2.
Xu Hong 《中国地球化学学报》1998,17(4):338-345
The Qixia gold deposit is one of the important quartz vein-type deposits hosted in metamorphic rocks in the east of Shandong,
China. Compositionally the wolframite which is associated with gold mineralization in the deposit is rich in iron, but poor
in manganese, showing that this mineral crystallized from hydrothermal solution at low temperature. The temperatures at the
main metallogenic stage of the Qixia gold deposit are within the range of 160–270°C. The gaseous phases in fluid inclusions
are dominated by H2O and CO2, while Na+, Ca2+ and Cl− are the major species in the fluid phase with K+ and F− present in relatively small amounts. The salinities of fluids are 4.2 wt% –8.0 wt% NaCl equiv. Meanwhile, the fluid is characterized
by either Ca2+ < Na+ < K+ (in five samples) or Na+ < Ca2+ < K+ (in two samples), quite similar to the composition of ore-forming fluid derived from meteoric water. Primary data on the
hydrogen and oxygen isotopic compositions of the ore-forming fluid fall within a wide range:
= − 56‱ − 95‱. and
= − 3. 6‱ − 4. 5‱ relative to SMOW. These isotopic values fully reflect the distribution features of meteoric water which
has exchanged with the metamorphic rocks of the Jiaodong Group at different temperatures and W/ R ratios, and the metallogenic
process is characterized by low W/R ratios. The Rb-Sr isochron age of the Qixia gold deposit is 125.8 ± 1.7 Ma, with (87Sr/86Sr)i being 0.7168, and the time interval between the gold deposit and its country rocks (granite or metamoprhic rocks) is very
large. The formation of the Qiaxia gold deposit is directly related to the evolution of geological history in eastern Shandong,
and a genetic model in which the deep convective circulating meteoric water reacts with the country rocks can be used to explain
the metallogenic mechanism of the deposit.
This project was financially supported by the National Natural Science Foundation of China (No. 49000020). 相似文献
3.
Genesis and Geological—Geochemical Characters of the ushan Gold Deposit,Shandong,China 总被引：3，自引：0，他引：3
The Rushan gold deposit, explored in recent years in the Jiaodong area, Shandong Province, is a quartz vein-type gold deposit
hosted in granite. The temperature of its major mineralization episode is between 220°C and 280°C. The salinity of the ore-forming
fluid is 5 % to 9% NaCl equivalent, with H2O and CO2 as the dominant gas constituents. The fluid is rich in Na+, Ca2+ and Cl−, but relatively impoverished in K+ and F−, characterized by either Ca2+ > Na+ > K+ (in three samples) or Na+ > Ca2+ > K+ (in six samples). Hydrogen and oxygen isotopes in the ore-forming fluid are highly variable with δ18
ranging between − 7.70‰ and 5. 97‰ and
between − 128‰ and − 71‰. The possibility of lamprophyre serving as the source of gold can be excluded in view of its low
gold content on the order of 2.5 × 10−9. Rb-Sr isochron ages of the deposit and the host Kunyushan granite are ( 104.8 ± 1.5) Ma and 134.6 Ma respectively with the
respective initial Sr ratios of 0. 71307 and 0.7096. It is considered that the emplacement of the lamprophyre under a tensile
environment had provided sufficient heat energy to facilitate deep circulation of meteoric water by which ore metals were
extracted from the Kunyushan granite through long-term water-rock reaction.
This project was financially supported by the National Natural Science Foundation of China. 相似文献
4.
On the basis of ore-forming periods and stages of the Dachang ore field, the pH and
conditions and the S isotopic systematics during ore formation have been thcrmodynamically treated in this paper. Calculations
show a progressively decreased pH, an increased oxidation regime and an intensified activity of sulfur from the early to the
late stage. Owing to the unreliability of inferring the S source from δ34Smin,
has been calculated using the Ohmoto’s model. Results indicate that the δ34
min frequency distribution is more concentrated than that of δ34Smin and the peak value shifts to negative region by 2.5%. The sulfur in the whole ore field seems to be of multiple source, i.e.,
different deposits have their own S sources. But the S isotopic composition pertaining to each stage is nearly constant, suggesting
that the ore-forming system be open to sulfur and the supply of sulfur be sufficient. The conclusions deduced from calculations
are supported by many lines of geological evidence. 相似文献
5.
Most altered clay minerals in uranium ore deposits in granites in the selected provinces of South China haveδ
18O
m
values ranging from 6.22 to 7.24,δDm from −60 to −70,δ
18O
from +3.05 to −3.07, and
from −20.2 to −37.5‰. Relative enrichment of32S in the uranium ore deposits and greater variations in Pb isotopic composition of galenas from them show that uranium ores
in the granites were formed in such a way that uranium in shallow-source granites had been mobilized by heated meteoric waters
and then migrated to local favourable locations along great faults to form uranium ore deposits.
Zhang Shaoli, Yang Wenjin, Tang Chunjing and Xu Wenxin did part of this work. 相似文献
6.
7.
Ligang Zhang 《中国地球化学学报》1988,7(2):109-119
Based on the oxygen isotopic compositions of 133 wolframite samples and 110 quartz samples collected from 30 tungsten ore
deposits in south China, in conjunction withδD values and other data, these deposits can be divided into four types.
Based on theδ
18O values of the coexisting quartz and wolframite and temperature data, two calibration equilibrium curves have been constructed,
and the corresponding equations have been obtained:
| (1) | Reequilibrated magmatic water-hydrothermal tungsten ore deposits. Theδ 18O values of wolframite and quartz samples from this type of tungsten ore deposits are about +5–+12‰, respectively. The calculatedδ 18O values of ore fluids in equilibrium with quartz are about +6.5‰, and theδ values of fluid inclusions in quartz range from −40 to −70‰ |
| (2) | Meteoric water-hydrothermal tungsten ore deposits. Theδ 18O values of wolframite in this type of tungsten deposits are around −1‰ |
| (3) | Stratiform tungsten ore deposits. In these deposits, theδ 18O values of quartz and wolframite are about +17 and +3‰, respectively. It is considered that these stratiform tungsten ore deposits are genetically related to submarine hot-spring activities. |
| (4) | Complex mixed-hydrothermal tungsten ore deposits. These tungsten ore deposits are characterized by multi-staged mineralization. Theδ 18O values of early wolframite are around +5‰, but of later wolframite are lower than +4‰, indicating that the early wolframite was precipitated from reequilibrated magmatic water-hydrothermal solutions and the late one from the mixture of hydrothermal solutions with meteoric waters or mainly from meteoric waters. |
|
相似文献
8.
Wolf Bernhard Dickoré 《GeoJournal》1991,25(2-3):265-284
Botanical results of the “Sino-German Joint Expedition to K2, 1986” are presented with remarks on vegetation of SW Kashgaria,
the W Kunlun Shan and the N declivity of the central Karakoram mountains. The vertical and horizontal zonation of the vegetation
and flora of a cross-section of the Karakoram/Kunlun N declivity from the edge of the Tarim basin to the summit-pyramid of
K2 is outlined. The transect covers altitudes between c. 1300 and 5200 m. Altitudinal vegetation belts distinguished along
the transect, their extension, and characteristic species are:
An annotated list of 301 species collected (1 Charophyta, 2 Pteridophyta, 6 Gymnospermae, 292 Angiospermae) is given. Floristical
and vegetation features of the Karakoram/Kunlun N declivity are discussed in connection with environmental factors and their
variation, and in relation to pleistocene glaciation. 相似文献
9.
提要：汤泉位于河北省遵化市西北部,为山前丘陵地貌,地热资源丰富。本文通过对该地区地热流体研究发现：Na+、Ca2+、K+、Mg2+与SO2-4、HCO-3、Cl-、NO-3是该地区地下热水的主要成分,水化学类型主要为SO2-4-Na+型,属于未污染的天然弱碱性水;流体中F-含量平均为9.36 mg/l,远高于国家地下水质量标准ⅴ级;可溶性SiO2的含量可作为地热温标;地热流体总矿化度平均为782.33 mg/l,属于淡水;为中等腐蚀型水,不结碳酸钙垢,无CaSO4?2H2O垢和SiO2垢生成的可能;地热流体属于含岩盐地层溶滤的陆相沉积水;根据氢氧稳定同位素可知,河北汤泉地热流体主要来源于大气降水。 相似文献
10.
The Saishitang skarn type copper deposit, located in the southeast part of the Dulan–Ela Mountain Triassic volcanic–magmatic arc and forearc accretionary wedge, belongs to the Tongyugou–Saishitang tin–copper polymetallic ore field in West Qinling, Qinghai province. Based on the contact/crosscutting relationships, mineral associations and mineralization characteristics, hydrothermal fluid evolution can be divided into three stages: skarn (I), quartz sulfide (II) and polymetallic sulfide-bearing quartz–calcite vein (III). The quartz sulfide stage (II) can be further divided into a massive sulfide stage (II-1) and a layered sulfide stage (II-2). This paper presents detailed analysis of fluid inclusions, H–O, S and Pb isotope compositions of rock samples from each of the above three stages as well as analysis of fluid inclusions from quartz diorite. The homogenization temperature, salinity, density and pressure of fluid inclusions in quartz diorite and typical transparent minerals showed a tendency of gradual decline in these evolutionary stages. The ore-forming fluid can be classified as a Na+–Ca2 +–SO42 − Cl− system with a minor proportion of a Na+–Ca2 +–NO3− SO42 − system, which likely resulted from mixing of magmatic and formation water. The H–O isotope composition indicates that the proportion of formation water increased during the ore-forming process, and meteoric water was mixed in the late quartz–calcite vein stage. The δ34S (CDT) values (− 6.45–5.57‰) and Pb isotope compositions show that the ore-forming materials were mainly derived from magmatic fluid. Ore-forming fluid was boiling during the main ore-forming stage (II-1) due to pressure decrease. Consequently, the physical and chemical conditions (i.e., pH, Eh, fO2, fS2) changed, and metallic elements (including Cu) in the fluid could no longer exist in the form of complexes and precipitated from the fluid. According to the integrated analysis of ore features, mineral associations, alteration characteristics, ore-forming environment and fluid evolutionary process, it is concluded that the Saishitang deposit is a typical skarn deposit. 相似文献
11.
河南桐柏老湾金矿床的成矿作用是在变基性火山碎屑沉积岩为矿源层的背景上演化的。本文根据矿床氢氧同位素研究,认为矿床的热液成矿期成矿流体为大气降水和老湾花岗岩岩浆水的混合,成矿Ⅰ阶段和Ⅱ阶段以岩浆水为主,成矿Ⅲ阶段以大气降水为主,但在成矿Ⅱ阶段大气降水已占有很大的比例。氦同位素分析表明,在老湾金矿形成过程中有地幔流体加入,且从成矿Ⅱ阶段至Ⅲ阶段,由于大气降水比例增大,其与地幔流体的混合导致成矿流体的3He/4He比值不断减小。 相似文献
12.
新水井铀(钍)矿床位于甘肃省龙首山成矿带,是碱交代型铀矿床的典型代表,其矿体完全产于钠交代蚀变花岗岩中,成矿过程可划分为钠交代蚀变、铀钍矿化和成矿后3个主要阶段。文章对该矿床花岗岩原岩、蚀变岩及矿石开展了系统主微量元素分析,采用Grant等浓度线法探讨了钠交代蚀变和铀钍矿化阶段的元素迁移规律,结果表明:钠交代蚀变阶段为富含Na、Ca、过渡族元素(Sc、V、Cr、Co、Ni)、U、Th及CO2、H2O等挥发分的复杂流体,钠交代过程中原岩中的大离子亲石元素(Rb、Ba)和部分轻稀土元素(LREE)不同程度带出;而铀钍成矿阶段成矿流体则富集重稀土元素(HREE)、U、Th、PO43-等成分,CO2等挥发分大量逸出。结合前人研究,认为新水井矿床成矿流体可能来自地幔流体和大气降水热液的混合;等挥发分CO2的逸出是新水井矿床最重要的矿质沉淀机制,导致了铀钍矿物和磷酸盐矿物(磷灰石)的共沉淀,而磷灰石的沉淀又促进了以磷酸盐形式搬运的Th元素的沉淀。 相似文献
13.
14.
Yang Liqiang Deng Jun Zhang Jing Guo Chunying Gao Bangfei Gong Qingjie Wang Qingfei Jiang Shaoqing Yu Haijun 《中国地质大学学报(英文版)》2008,19(4):378-390
The recently discovered Damoqujia (大磨曲家) gold deposit is a large shear zone-hosted gold deposit of disseminated sulphides located in the north of the Zhaoping (招平) fault zone, Jiaodong (胶东) gold province, China. In order to distinguish the temperature range of cluster inclusions from different mineralization stages and measure their compositions, 16 fluid inclusions and 5 isotopic geochemistry samples were collected for this study. Corresponding to different mineralization stages, the multirange peaks of quartz decrepitation temperature (250-270, 310-360 and 380-430℃(2) indicate that the activity of ore-forming fluids is characterized by multistage. The ore-forming fluids were predominantly of high-temperature fluid system (HTFS) by CO2-rich, and SO2-4-K type magmatic fluid during the early stage of mineralization and were subsequently affected by low-temperature fluid system (LTFS) of CH4-rich, and Cl--Na /Ca2 type meteoric fluid during the late stage of mineralization. Gold is transferred by Au-HS- complex in the HTFS, and Au-Cl- complex can be more important in the LTFS. The transition of fluids from deeper to shallow environments results in mixing between the HTFS and LTFS, which might be one of the most key reasons for gold precipitation and large-scale mineralization. The ore-forming fluids are characterized by high-temperature, strong-activity, and superimposed mineralization, so that there is a great probability of forming large and rich ore deposit in the Damoqujia gold deposit. The main bodies are preserved and extend toward deeper parts, thereby suggesting a great potential in future. 相似文献
15.
Two kinds of mylonite series rocks, felsic and mafic, have been recognized in the NW-striking shear zone of the Jiapigou gold
belt. During ductile deformation, a large amount of fluid interacted intensively with the mylonite series rocks: plagioclases
were sericitized and theAn values declined rapidly, finally all of them were transformed to albites; dark minerals were gradually replaced by chlorites
(mostly ripidolite). Meanwhile, large-scale and extensive carbonation also took place, and the carbonatization minerals varied
from calcite to dolomite and ankerite with the development of deformation. The δ13C values of the carbonates are −3.0‰ – −5.6‰ suggesting a deep source of carbon. The ductile deformation is nearly an iso-volume
one (f
v≈1). With the enhancement of shear deformation, SiO2 in the two mylonite series rocks was depleted, while volatile components suchs as CO2 and H2O, and some ore-forming elements such as Au and S were obviously enriched. But it is noted that the enrichment of Au in both
the mylonite series rocks did not reach the paygrade of gold. The released SiO2 from water-rock interactions occurred in the form of colloids and absorbed gold in the fluid. When brittle structures were
formed locally in the ductile shear zone, the ore-forming fluids migrated to the structures along microfractures, and preciptated
auriferous quartz because of reduction of pressure and temperature. Fluid inclusion study shows that the temperature and pressure
of the ore-forming fluids are 245–292°C and 95.4–131.7 MPa respectively; the salinity is 12.88–16.33wt% NaCl; the fluid-phase
is rich in Ca2+, K+, Na+, Mg2+, F− and Cl−, while the gaseous phases are rich in CO2 and CH4. The δD and δ18O, values of the ore-forming fluid are −84.48‰ – −91.73‰ and −0.247‰ – +2.715‰ respectively, suggesting that the fluid is
composed predominantly of meteoric water.
This project is financially supported by the National Natural Science Foundation of China (No. 9488010). 相似文献
16.
Ulrich Kramm 《Contributions to Mineralogy and Petrology》1979,69(2):143-150
In the Ultevis District, Northern Sweden, viridine occurs in a potassium rich, microcline-bearing leptite together with quartz, plagioclase, phlogopite, opaques, and a retrogradely formed muscovite. The formation of viridine in this rock may be described by a dealkalization process of microcline, in which opaque minerals are involved. A diffusion of K+ and H2O out of the centres of viridine formation and of H+ into these localities, which is a prerequisite of such type of reaction, may have been favoured by a contemporaneous migmatization of the rock, since the granite-like melts can be regarded as sinks for potassium and water. The following decomposition of viridine is initiated by the reverse reaction. Texturally this is indicated by small microcline seams along the contacts between viridine and quartz grains. The final alkalization of the viridine-quartz assemblage to form muscovite reflects increasing K+/H+-ratios and H2O-contents of the vapor phase and/or decreasing temperatures. The potassium and water amounts necessary for the viridine decomposition reactions may have been generated by the cooling of the granitic liquids. An intergrowth of sillimanite and the muscovite can be described by a degenerated reaction. It can be interpreted as giving way to an equilibration of the alumosilicates und the actual metamorphic conditions, that is here P, T,
, a
k
+, a
h
+ and a
Mn
3+.The viridine investigated has the lowest Mn-contents recorded so far for andalusite-type minerals with viridine optics (1.3–2.2 mol-% Mn2SiO5-component). Since no andalusite with lower Mn-contents occurs in the rock and since no other Al2SiO5-phase formed at this metamorphic stage it may be assumed that the incorporation of manganese stabilizes the andalusite structure under the P-, T-,
–, a
k
+-, a
h
+- and a
Mn
3+-conditions verified in this particular leptite.The temperature of viridine formation is estimated to be about 600 ° C, the decomposition of viridine +quartz into the muscovite-sillimanite assemblage may have happened between 650–500 ° C at 6–2.5 kb. 相似文献
17.
地质流体研究是地球科学领域的研究热点,矿物流体包裹体中成分是认识地质流体的关键。群体包裹体液相成分分析的传统方法大多采用单通道离子色谱分析阴离子,原子吸收光谱或电感耦合等离子体原子发射光谱分析阳离子,分析方法适用矿物种类少,单矿物需要量大（3g以上）。本文使用双通道离子色谱仪,经过大量条件实验,优化了样品爆裂、提取等前处理分析条件,确认了不同矿物可检测的离子,并采用富集方法将样品需要量由常规的3.00g减少到300mg,实现了石英、方解石、萤石、闪锌矿、石榴子石、磁铁矿和黄铁矿等多种矿物流体包裹体液相成分中Li+、Na+、K+、Mg2+、Ca2+、F-、Cl-、Br-、NO2-、NO3-、SO42-等阴阳离子的同时分析。所建立的离子色谱同时分析矿物流体包裹体液相微量成分分析方法简便、快速,成本低,用样量少,扩大了矿物种类的分析范围,为成矿流体研究提供了更加直接、有效的信息。 相似文献
18.
Isotope geochemistry of ore fluids for the Dongsheng sandstone-type uranium deposit, China 总被引：2，自引：1，他引：2
The Dongsheng sandstone-type uranium deposit is one of the large-sized sandstone-type uranium deposits discovered in the northern part of the Ordos Basin of China in recent years. Geochemical characteristics of the Dongsheng uranium deposit are significantly different from those of the typical interlayered oxidized sandstone-type uranium ore deposits in the region of Middle Asia. Fluid inclusion studies of the uranium deposit showed that the uranium ore-forming temperatures are within the range of 150–160℃. Their 3He/4He ratios are within the range of 0.02–1.00 R/Ra, about 5–40 times those of the crust. Their 40Ar/36Ar ratios vary from 584 to 1243, much higher than the values of atmospheric argon. The δ18OH2O and δD values of fluid inclusions from the uranium deposit are -3.0‰– -8.75‰ and -55.8‰– -71.3‰, respectively, reflecting the characteristics of mixed fluid of meteoric water and magmatic water. The δ18OH2O and δD values of kaolinite layer at the bottom of the uranium ore deposit are 6.1‰ and -77‰, respectively, showing the characteristics of magmatic water. The δ13CV-PDB and δ18OH2O values of calcite veins in uranium ores are -8.0‰ and 5.76‰, respectively, showing the characteristics of mantle source. Geochemical characteristics of fluid inclusions indicated that the ore-formation fluid for the Dongsheng uranium deposit was a mixed fluid of meteoric water and deep-source fluid from the crust. It was proposed that the Jurassic-Cretaceous U-rich metamorphic rocks and granites widespread in the northern uplift area of the Ordos Basin had been weathered and denudated and the ore-forming elements, mainly uranium, were transported by meteoric waters to the Dongsheng region, where uranium ores were formed. Tectonothermal events and magmatic activities in the Ordos Basin during the Mesozoic made fluids in the deep interior and oil/gas at shallow levels upwarp along the fault zone and activated fractures, filling into U-bearing clastic sandstones, thus providing necessary energy for the formation of uranium ores. 相似文献
19.
Sulfur Isotope Fractionation in Magmatic Systems：Models of Rayleigh Distillation and Selective Flux 总被引：2，自引：0，他引：2
郑永飞 《中国地球化学学报》1990,9(1):27-45
The effect of Rayleigh distillation by outgassing of SO2 and H2S on the isotopic composition of sulfur remaining in silicate melts is quantitatively modelled.A threshold mole fraction of sulfur in sulfide component of the melts is reckoned to be of critical importance in shifting the δ^34S of the melts mith respect to the original magmas.The partial equilibrium fractionation in a magmatic system is evaluated by assuming that a non-equilibrium flux of sulfur occurs between magmatic volatiles and the melts,while an equilibrium fractionation is approached between sulfate and sulfide within the melts.The results show that under high fo2 conditions,the sulfate/sulfide ratio in a melt entds to increase,and the δ^34S value of sulfur in a solidified rock might then be shifted in the positive direction.This may either be due to Rayleigh outgassing in case the mole fraction of sulfide is less than the threshold,or due to a unidirectional increase in δ^34S value of the sulfate with decreaing temperature,Conversely,at low fo2,the sulfate/sulfide ratio tends to decrease and the δ^34S value of total sulfur could be driven in the negative direction,either because of the Rayleigh outgassing in case the mole fraction of sulfide is greater than the threshold,or because of a unidirectional decrease inδ^34S value of the sulfide.To establish isotopic equilibrium between sulfate and sulfide,the HM,QFM or WM buffers in the magmatic system are suggested to provide the redox couple that could simultaneously reduce the sulfate and oxidize the sulfide.CaO present in the silicatte Melts is also called upon to participate in the chemical equilibrium between sulfate and sulfide,Consequently,the δ^34S value of an igneous rock could considerably deviate from that of its original magma due to the influence of oxygen fugacity and temperature at the time of magma solidification. 相似文献
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