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罗河铁矿(又称庐枞铁矿)是我国长江中下游火山岩地区大型铁矿床之一,是一种重要的矿床类型。十多年来,各研究单位和生产部门对该矿床进行了多方面、较系统的研究,取得可喜成果(张荣华等,1974;张荣华,1981;陈锦石等,1982)。然而,要进一步阐明这类矿床的成矿机理,还需要对该矿床的蚀变和成矿条件进行深入研究。本文着重讨论罗河铁矿的硫同位素分馏机制,并在此基础上结合地质和矿物包裹体的资料,近似定量地推算该矿床形成各阶段的物理化学条件范围及变化规律。 相似文献
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马城沉积变质型铁矿床是在近几年铁矿勘查中新发现超大型矿床,其矿体赋存于新太古界滦县群,铁矿形成后遭受了多期变质变形作用及后期热液蚀变。本文在野外工作的基础上,对马城沉积变质型铁矿床中不同类型磁铁石英岩中的石英开展了详细的流体包裹体研究,马城铁矿遭受绿帘-角闪岩相变质作用的峰期阶段主要形成IIb类气体包裹体和IV类含液态CO2三相包裹体,流体包裹体均一温度为314℃~580℃,盐度主要位于2wt%~10 wt%Na Cl区间,表现为低盐度特征;绿帘-角闪岩相变质作用峰后形成IIa类液体包裹体和III类含子矿物包裹体,流体包裹体主体均一温度为120~447℃,盐度0.88wt%~35.32wt%Na Cl,均一温度和盐度变化范围较大,可能代表了区域变质峰后阶段变质流体具有多期性的特点;后期热液蚀变阶段形成I类次生包裹体,包裹体均一温度为131~239℃,盐度为1.4wt%~21.6wt%Na Cl,表现为中低盐度特征。 相似文献
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矽卡岩岩浆对中国北方某些矽卡岩型矿床形成的制约——来自包裹体激光拉曼分析证据 总被引：4，自引：1，他引：3
本文将报道中国北方主要矽卡岩型矿床矿物熔融包裹体和流体-熔融包裹体的激光拉曼分析结果。研究目的是确认这些矿化矽卡岩矿物是否含熔融包裹体和流体-熔融包裹体,获取有关它们相态特征和相组成以及它们的分布状况(是局部的、偶然性的,还是广泛的)的信息。文章对邯邢铁矿、蒙库铁矿和杨家杖子钼矿等9个矿床12块标本中石榴石、辉石和方解石或白云石中23个包裹体进行了共聚焦激光拉曼光谱仪分析。拉曼分析结果表明,所研究的矽卡岩矿物均含熔融包裹体和/或流体-熔融包裹体,它们是岩浆矽卡岩的直接证据。结合本文激光拉曼分析结果、地质背景和其他地区岩浆矽卡岩矿物包裹体测温学研究,对所研究矽卡岩的形成机制和岩浆矽卡岩对中国北方某些矽卡岩型矿床的制约进行了讨论。认为含有熔融包裹体和/或流体-熔融包裹体的矿化矽卡岩系岩浆成因,其分布范围广泛,规模不小。中国北方某些矽卡岩型矿床的时空分布和规模受控于该地区分布的岩浆矽卡岩。希望本文有助于拓宽矽卡岩型矿床成矿规律研究和深部找矿勘探的思路。 相似文献
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矽卡岩矿床各种硅酸盐矿物中熔融包裹体和流体-熔融包裹体的显微测温资料和相成分让我们提出过大量矽卡岩是岩浆成因的建议。在本文中,我们提供沿长江中下游成矿带的许多矽卡岩矿床包含在石榴子石和辉石里的熔融包裹体和流体-熔融包裹体的激光拉曼分析结果,目的是证明所研究的并与Cu-Fe-Au矿床共生的矽卡岩系岩浆成因。我们的研究结果显示,熔融包裹体只含固体相和微量气相。流体-熔融包裹体除了含大量固相外,还含微量流体和气相以及没有被仪器检测到的气体。固体相与包裹体寄主矿物相同或类似。流体相主要为水或盐水溶液和包括C6H6、C3H6、C3H8、CH4、CO2和O2的气体。我们提出,熔融包裹体和流体-熔融包裹体是原始岩浆的最好代表。这就证明,矽卡岩组合是由一个原生岩浆直接结晶而成。此外,我们还讨论了岩浆矽卡岩形成的温度、分布范围和规模、形成机制和与Cu-Fe-Au矿化作用的联系。 相似文献
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吉伯特铁矿是新疆阿勒泰地区产于泥盆纪海相火山岩中的小型矿床。本文对吉伯特铁矿床的包裹体开展了研究,识别了熔体包裹体、熔体-流体包裹体以及富晶体的流体包裹体,并对其进行了初步的显微测温、激光拉曼光谱和电子探针等研究。熔体包裹体中含有富Si玻璃质、贫Si富Fe熔体、石英、萤石、方解石、磁铁矿等多种成分,它们分别组成不同的包裹体组合。熔体包裹体、熔体-流体包裹体和流体包裹体的存在表明它们被捕获时是一种熔体与流体共存的不混溶状态,这充分说明了吉伯特铁矿床的形成与岩浆熔体、岩浆-热液过渡性流体有直接的成因联系。吉伯特铁矿床中Fe的矿化是一个熔体相逐渐减少,流体相逐渐增加的连续演化过程,它受岩浆作用、岩浆-热液过渡性流体以及矽卡岩作用的共同制约。 相似文献
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成矿流体来源与矿床成因的关系一直是矿床学研究的重点与难点。通过流体包裹体显微测温、原位激光拉曼光谱分析和包裹体化学成分分析,对浩尧尔忽洞金矿床成矿流体进行了较系统的研究。测试结果表明:该矿床石英中流体包裹体分为气液包裹体、气体包裹体、纯气体包裹体和纯液相包裹体四类。大部分流体包裹体均一为液相,少量气体包裹体均一为气相。伟晶岩脉石英流体包裹体均一温度峰值260～340℃,炭质板岩内含矿石英细脉内石英流体包裹体均一温度峰值260～380℃。石英流体包裹体气相成分为H2O、CO2、CH4、N2和C2H6,液相成分为Cl-、SO2-4、Na+、K+、Mg2+和Ca2+。炭质板岩中石英流体包裹体的氢氧同位素(δD H2O=-96.20‰～-82.80‰,δ18O H2O=3.97‰～7.93‰)靠近原生岩浆水。认为浩尧尔忽洞金矿床成矿与海西期岩浆活动有关,属中高温低压浅成热液矿床。 相似文献
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研究气液包裹体有三个基本前提:(1)包裹体形成时,其内函物为均匀相;(2)包裹体形成后,其体积无明显变化;(3)包裹体封闭后,没有物质的加入和逸出。在这些前提下,才能利用包裹体的研究资料,来探讨矿物形成的物理化学条件。缺此,就失去研究包裹体的意义。因为只有在矿物形成过程中,封闭在其中的包裹体,才保存了原始矿液。所以在研究包裹体时,首先要认出那些包裹体是在矿物形成时形成的,那些是在矿物形成后形成的。前者称为原生包裹体,后者称为次生包裹体。 相似文献
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姑山铁矿床产在燕山期辉石闪长岩与中三叠统黄马青组砂页岩的接触带上。矿石具有典型的斑状、球颗状和骨架状结构。镜下研究表明,这些结构不是矿浆结晶的产物,而是热液成因微晶赤铁矿在后期地质过程中发生变晶生长所致。矿床中的蚀变和矿化自下而上呈现规律性的分带。碳酸盐化是特征性的蚀变类型,其形成与成矿密切有关,并可作为一种近矿找矿标志。在热液成矿过程中,辉石闪长岩中的铁很可能以羰基络合物的形式发生活化转移。在热液演化过程中由于氧逸度的升高和碱度、压力的降低,羰基络合物发生分解而使铁在接触带附近沉淀成矿。 相似文献
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《International Geology Review》2012,54(9):1122-1137
We have studied melt and fluid inclusions in minerals from alkali basalts, mantle xenoliths, and dawsonite-bearing sandstones from the Shuangliao volcanic field in southern Songliao Basin, Northeast China. The inclusions have been investigated using petrographic, geochemical, and laser Raman spectroscopic techniques. Volcanic rocks of the Shuangliao field are predominantly alkali olivine basalts that contain rare mantle xenoliths. Silicate melt and fluid inclusions are common in both olivine phenocrysts and the mantle xenoliths. The fluid inclusions are mainly composed of CO2 with small amounts of CO, CH4, N2, and H2O, which is consistent with an upper mantle origin. CO2 gas reservoirs in the southern Songliao Basin are mostly derived from a mantle–magmatic source. Coeval fluid-inclusion homogenization temperatures, coupled with the thermal burial history, show that the CO2 gas reservoirs in the southern Songliao Basin are Cenozoic (40–63 Ma) and coeval with the magmatism in the Shuangliao volcanic field. Despite the relatively small scale of this volcanic activity, it released large amounts of CO2. Much of the magma was not erupted, and CO2- and H2O-rich magma was probably intruded into the basin along deep faults, acting as a major source of inorganic CO2 gas in the southern Songliao Basin. 相似文献
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Cycles of the geosynclinal-orogenic-platformal development of the continental crust are separated by natural phases of crustal destruction. They are determined by pulses of degassing of the Earth’s core marked by decelerated inversions of the magnetic field. Such pulses occur under the influence of fluid flows that ascend from the core and loss hydrogen. Consequently, the fluids acquire acidic properties and become aggressive to rocks of the continental crust (H2 + 2CO = H2 O + 0.5CO2 + 1.5C). Oceanization of the continental crust represents the main result of its destruction accompanied by the formation of seas and sedimentary basins largely on the underwater margins of continents. Development of geodynamic compression setting of the Earth’s crust due to its evolution creates conditions that impede the loss of hydrogen from ascending fluid flows. Consequently, they acquire the ability to generate hydrocarbons (4H2 + 2CO = 2H2O + CH4 + C) and produce oil and gas pools. This setting is marked by intrusions of alkaline rocks with characteristic water-hydrocarbon inclusions in minerals and by the development of fold-thrust and reversed fault dislocations in depressions. The dislocations controlled not only the fluid-related leaching of rocks, but also the distribution of oil and gas pools within both sedimentary basins and their basement. 相似文献
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E. G. Konnikov W. P. Meurer S. S. Neruchev E. M. Prasolov E. V. Kislov D. A. Orsoev 《Mineralium Deposita》2000,35(6):526-532
The Dovyren layered dunite–troctolite–gabbro massif (northern Transbaikalia region, Russia) contains precious metal mineralization
related to sparsely disseminated sulfides (Stillwater type). The distribution of gases trapped in micro-inclusions and intergranular
pores of the Dovyren massif has been investigated. This type of study had previously only been undertaken on the traps or
peridotite–pyroxenite–norite intrusions hosting copper–nickel sulfide deposits. A novel method of analyzing trapped gases,
involving the grinding of samples under high vacuum at room temperature, was employed. A modified gas-chromatography and mass-spectrometry
approach was used to analyze the composition of the extracted gases. The concentrations of reduced gases (CH4 and H2) are higher in inclusions trapped by silicate minerals, whereas oxidized gases (H2O, CO2) are less common. The content of reduced gases (H2, CH4, CO), N2, He, radiogenic Ar, and C2H6 increases upward through the layered series of the massif. The distribution of all gases, especially methane and hydrogen,
show peak concentrations coincident with the PGE and gold reef type horizons. A correlation of the gas peaks and noble metal
contents appears to be related to their geochemical affinities. This conclusion is supported by the experimental modeling.
Received: 4 August 1999 / Accepted: 13 January 2000 相似文献
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A new condensation sequence appears if the ratio in a gas of otherwise solar composition is increased by less than a factor of two. As the ratio increases from the solar value of 0.6 to ? 1 the gas becomes extremely reduced, the condensation temperatures of silicates and oxides are depressed markedly ～ 400 K and a new suite of refractory minerals appears: AIN, CaS, MgS, SiC, TiN, graphite, Si2N2O and probably metastable (Fe,Ni)3C. Many of these minerals are unique to enstatite chondrites and may be analogues of the refractory silicates and oxides found in more oxidized meteorites such as Allende.The change in chemistry is related to the stability of CO, the most stable C or O compound at high T. Since the elements occur in a 1:1 ratio in CO, only the element which is in excess is free to form other compounds. But as T decreases CO reacts with H2 to form graphite, CH4 or other hydrocarbons thereby freeing O to form H2O. If equilibrium is maintained oxides and silicates form at about 1000 K (, Pτ = 10?4atm) as products of reactions among the carbides, nitrides, sulfides and the gas. The possibility that equilibrium was not maintained among the C-bearing species was also investigated. If either graphite or CH4 does not form as predicted the stability fields of the reduced minerals expands to lower temperatures. If neither graphite nor CH4 form as predicted, CO remains stable and the nebular gas is highly reduced at all temperatures.Enstatite chondrites appear to have originated in a region of the nebula where the ratio was somewhat higher than the solar value. Various fractionation mechanisms are considered. An interesting possibility is that graphite, which is quite refractory under a wide range of conditions, survived the collapse of the solar nebula. 相似文献
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M. Ahmad 《Australian Journal of Earth Sciences》2013,60(5):427-443
Tabular steeply dipping cassiterite‐bearing lodes in the Mount Wells region are hosted by lower greenschist fades metasediment of the Pine Creek Geosyncline within the contact aureole of late orogenic granitoids. The latter are predominantly I‐type, but S‐type phases are developed near the sediment‐granitoid contact. Quartz, cassiterite, pyrite, arsenopyrite, chalcopyrite and pyrrhotite are the main minerals. Two types of lodes are present: (i) Sn‐quartz lodes containing 5–10 vol% sulphide minerals; and (ii) Sn‐sulphide lodes containing ～ 70 vol% sulphide minerals. At the surface, the former appear as normal quartz veins and the latter as hematite‐quartz breccia resulting from the collapse of original sulphide‐rich lodes as a consequence of volume reduction due to oxidation and leaching. Two stages of quartz veining are recognized in both types of lodes. Cassiterite is present in stage I while stage II is composed of barren quartz with minor pyrite. Late stage III carbonate veinlets are present in Sn‐sulphide lodes. The lode‐wallrock contact is sharp with weak alteration effects confined to the fringe of the lodes. The alteration minerals include sericite, quartz, tourmaline, chlorite, pyrite and minor K‐feldspar. Four types of fluid inclusions are present in vein quartz and cassiterite: Type A (CO2 ± H2O ± CH4); Type B (H2O+～ 20% vapour); Type C (H2O+ < 15% vapour) and Type D (H2O+ < 15% vapour + NaCl). Early ‘primary’ inclusions represented by Types A and B are present in stage I only and have a well‐defined temperature mode at ～300°C and a salinity range of 1–20 wt% eq NaCl. Types C and D inclusions are ‘secondary’ in stage I and primary in stage II and have a temperature mode at 120–160°C and salinities from about 1 to more than 26 wt% eq NaCl. Variable H2O‐CO2 ratios of Type A inclusions and homogenization in CO2 or H2O phase at near identical temperature indicate entrapment at the H2O‐CO2 solvus and define a pressure of ～ 100 MPa. The melting sequence of frozen inclusions suggests that the ore fluids were mainly H2O‐CO2‐CH4‐Na‐Ca‐Cl brines. This is also confirmed by Raman Laser Spectrometry. Oxygen and sulphur isotope data are consistent with a magmatic origin of the ore fluids. The δD values are up to 20%0 higher than those expected for magmatic fluids and probably resulted from interaction of the latter with the carbonaceous strata. This interpretation is supported by δ13C data on the fluid inclusion CO2. Fluid inclusions, stable isotope and mineralogical data are used to approximate the physico‐chemical parameters of the ore fluids which are as follows: T 300°C, m Cl～2, fO2 ～ 10‐35, mSS ～ 0.01, Sn ～ 1 ppm, Cu ～ 1 ppm and pH ～ 5.5. It is suggested that fluids of granitic parentage interacted with the enclosing sediment and picked up CO2, CH4 and possibly Ca. The granitic phases became reduced due to this interaction and developed S‐type characteristics. Tin was probably partitioned into the CH4‐bearing reduced fluids. At some stage the fluid overpressure exceeded the lithostatic lode enforcing failure of the carapace and the intruded rocks by hydraulic fracturing causing CH4 and CO2 loss resulting in the precipitation of the ore minerals. 相似文献
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The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases(CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6) in the fluids were critical in the formation of barium sulfate versus carbonate.The δ~(34)S values of barite range from 38.26‰ to54.23‰(CDT),the δ~(34)S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰(CDT),and those in the wall rock from 11.60‰ to 19.06‰(CDT).We propose that the SO_4~(2-)generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4~(2-)also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ~(13)C values of witherite range from-27.30‰ to-11.80‰(PDB),suggesting that carbon was sourced from organic substances(like CH_4,C_2H_4,and C_2H_6).The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4~(2-) in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming witherite include high fluid temperatures,high Ba~(2+) concentrations,CO_2 in the fluids,low HS~- concentrations,and the subsequent rapid diffusion of H_2S during thermochemical sulfate reduction of the fluids. 相似文献
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Fluid and gas migration in the North German Basin: fluid inclusion and stable isotope constraints 总被引：1，自引：0，他引：1
Volker Lüders Christian Reutel Peer Hoth David A. Banks Birgit Mingram Thomas Pettke 《International Journal of Earth Sciences》2005,94(5-6):990-1009
Fluid inclusions have been studied in minerals infilling fissures (quartz, calcite, fluorite, anhydrite) hosted by Carboniferous
and Permian strata from wells in the central and eastern part of the North German Basin in order to decipher the fluid and
gas migration related to basin tectonics. The microthermometric data and the results of laser Raman spectroscopy reveal compelling
evidence for multiple events of fluid migration. The fluid systems evolved from a H2O–NaCl±KCl type during early stage of basin subsidence to a H2O–NaCl–CaCl2 type during further burial. Locally, fluid inclusions are enriched in K, Cs, Li, B, Rb and other cations indicating intensive
fluid–rock interaction of the saline brines with Lower Permian volcanic rocks or sediments. Fluid migration through Carboniferous
sediments was often accompanied by the migration of gases. Aqueous fluid inclusions in quartz from fissures in Carboniferous
sedimentary rocks are commonly associated with co-genetically trapped CH4–CO2 inclusions. P–T conditions estimated, via isochore construction, yield pressure conditions between 620 and 1,650 bar and temperatures between
170 and 300°C during fluid entrapment. The migration of CH4-rich gases within the Carboniferous rocks can be related to the main stage of basin subsidence and stages of basin uplift.
A different situation is recorded in fluid inclusions in fissure minerals hosted by Permian sandstones and carbonates: aqueous
fluid inclusions in calcite, quartz, fluorite and anhydrite are always H2O–NaCl–CaCl2-rich and show homogenization temperatures between 120 and 180°C. Co-genetically trapped gas inclusions are generally less
frequent. When present, they show variable N2–CH4 compositions but contain no CO2. P–T reconstructions indicate low-pressure conditions during fluid entrapment, always below 500 bar. The entrapment of N2–CH4 inclusions seems to be related to phases of tectonic uplift during the Upper Cretaceous. A potential source for nitrogen
in the inclusions and reservoirs is Corg-rich Carboniferous shales with high nitrogen content. Intensive interaction of brines with Carboniferous or even older shales
is proposed from fluid inclusion data (enrichment in Li, Ba, Pb, Zn, Mg) and sulfur isotopic compositions of abundant anhydrite
from fissures. The mainly light δ34S values of the fissure anhydrites suggest that sulfate is either derived through oxidation and re-deposition of biogenic
sulfur or through mixing of SO42−-rich formation waters with variable amounts of dissolved biogenic sulfide. An igneous source for nitrogen seems to be unlikely
since these rocks have low total nitrogen content and, furthermore, even extremely altered volcanic rocks from the study area
do not show a decrease in total nitrogen content. 相似文献
19.
In the New Caledonia high-pressure schists pyrite, pyrrhotite, chalcopyrite, rutile and sphene are common phases while hematite and ilmenite are rare and magnetite is absent. The parageneses of these minerals were clarified from their occurrence as inclusions in garnet, from phase relations in the Cu-Fe-S and Fe-Ti-O-S systems, and from phase rule considerations for the multi-component system. The sulfur fugacity estimated for pelites and basites containing pyrrhotite, pyrite and rutile increased with increasing metamorphic grade; the oxygen fugacity in these schists was less than 10–27.6 bars at 400° C, 10 kb and 10–22.3 bars at 500° C, 11 kb. Among the other components of the metamorphic fluid in pelites, H2O was major, CH4, CO2 and H2S minor, and H2, CO, COS and SO2 rare. The fluid composition altered with advancing metamorphic grade, such that H2O decreased while CO2, CH4 and H2S increased, and this change was linked to concurrent massive decarbonization in the rock matrices. 相似文献