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1.
Partial melting of sulfide ores during prograde metamorphism could have been more prevalent than generally accepted. However, identification of such melting is difficult as sulfide melts do not form glasses and the textures generated on quenching are obliterated due to the tendency of sulfides for ready recrystallization. The polymetallic base metal sulfide deposit at Rajpura–Dariba, Rajasthan, India is a typical stratiform ore metamorphosed to the middle amphibolite facies. The peak metamorphic temperature of 600 °C should have been sufficient to initiate sulfide melting as evident from experimental studies in the ZnS–PbS–Cu2S–FeS2–S system. Further, syn-metamorphic melting of the original SEDEX ore was abetted by the high fS2 condition that prevailed as a consequence of barite dissolution. A Zn–Fe–S melt containing minor Pb, Sb and Cu but no Ag fractionated from an initial melt in the above system resulting in a residual immiscible sulfosalt-bearing PbS melt. The final metallic melts, represented by formation of dyscrasite (Ag3Sb) from the sulfosalt-bearing melt and breithauptite (NiSb) or ullmannite (NiSbS) from the sulfosalt-absent melt, were a product of independent fractional crystallization of the immiscible sulfide and PbS–sulfosalt melts. 相似文献
2.
Melt loss and the preservation of granulite facies mineral assemblages 总被引：29，自引：3，他引：29
The loss of a metamorphic fluid via the partitioning of H2O into silicate melt at higher metamorphic grade implies that, in the absence of open system behaviour of melt, the amount of H2O contained within rocks remains constant at temperatures above the solidus. Thus, granulite facies rocks, composed of predominantly anhydrous minerals and a hydrous silicate melt should undergo considerable retrogression to hydrous upper amphibolite facies assemblages on cooling as the melt crystallizes and releases its H2O. The common occurrence of weakly retrogressed granulite facies assemblages is consistent with substantial melt loss from the majority of granulite facies rocks. Phase diagram modelling of the effects of melt loss in hypothetical aluminous and subaluminous metapelitic compositions shows that the amount of melt that has to be removed from a rock to preserve a granulite facies assemblage varies markedly with rock composition, the number of partial melt loss events and the P–T conditions at which melt loss occurs. In an aluminous metapelite, the removal of nearly all of the melt at temperatures above the breakdown of biotite is required for the preservation of the peak mineral assemblage. In contrast, the proportion of melt loss required to preserve peak assemblages in a subaluminous metapelite is close to half that required for the aluminous metapelite. Thus, if a given proportion of melt is removed from a sequence of metapelitic granulites of varying composition, the degree of preservation of the peak metamorphic assemblage may vary widely. 相似文献
3.
Forward modelling of Fe-rich phyllite is used to evaluate the effects of partial melting and melt loss on the concentration of iron in the residual rock package, leading to enrichment in Fe-oxide minerals (magnetite and hematite). The effect of melt loss during prograde metamorphism to peak conditions of ~ 850 °C was modelled using a series of calculated pressure–temperature (P–T) phase diagrams (pseudosections). The results show that metapelitic rocks with lower iron content are more fertile, produce more melt and therefore show a more significant increase (up to 35%) in the Fe-oxide content in the residual (melt depleted) rock package. Rocks with primary Fe-rich compositions are less fertile, lose less melt and therefore do not experience the same relative increase in the amount of Fe-oxides in the residuum. The results of the modelling have implications for the formation of economic-grade iron ore deposits in metamorphic terranes. Fe-rich compositions that represent primary ore horizons prior to metamorphism may not experience significant enrichment. However, those horizons with lower primary iron contents may be significantly upgraded as a result of melt loss, thereby improving the overall grade of the ore system. The application of the modelling to the highly metamorphosed Palaeoproterozoic Warramboo magnetite–hematite deposit in the southern Gawler Craton suggests that melt loss during granulite facies metamorphism led to upgrading of sub-economic units within the low-grade Price Metasediments to form the economically viable granulite facies Warramboo ore system. The results of this study suggest that high-temperature metamorphic terranes offer attractive exploration targets for magnetite-dominated iron ore deposits. 相似文献
4.
Three types of zircon occur in a complexly deformed and variably migmatized quartzofeldspathic gneiss from the Reynolds Range, central Australia. The oldest type is inherited from the granitic precursor of the gneiss, and is overgrown by a second group of zircon grains that formed during prograde, granulite facies metamorphism. Partial melting of the gneiss resulted in solution of both the inherited and metamorphic zircon. No new zircon growth accompanied crystallization of the partial melt, suggesting loss of zirconium–rich residual fluids. Hydrous, amphibolite facies retrogression of the gneiss and its migmatized variants during late shearing produced new, idiomorphic zircon in both the shear zone and its wall rocks.
Important implications of this study are that (i) zircon has a tendency to dissolve if it comes into direct contact with a melt produced from anhydrous biotite breakdown in a quartzofeldspathic granulite, (ii) melt crystallization is not necessarily accompanied by zircon growth, and (iii) euhedral zircon can grow from a hydrous fluid phase under subsolidus, amphibolite facies conditions, e.g. within shear zones. 相似文献
Important implications of this study are that (i) zircon has a tendency to dissolve if it comes into direct contact with a melt produced from anhydrous biotite breakdown in a quartzofeldspathic granulite, (ii) melt crystallization is not necessarily accompanied by zircon growth, and (iii) euhedral zircon can grow from a hydrous fluid phase under subsolidus, amphibolite facies conditions, e.g. within shear zones. 相似文献
5.
Andrew G. Tomkins 《Mineralium Deposita》2007,42(6):627-637
The relative importance of mechanical re-mobilisation, hydrothermal dissolution and re-precipitation, and sulphide melting
in controlling redistribution of metals during concurrent metamorphism and deformation is evaluated at the middle amphibolite
facies Montauban deposit in Canada. As at many other deposits, ductile deformation was important in driving mechanical re-mobilisation
of massive sulphides from limb regions into hinge regions of large-scale folds and is thus the most important for controlling
the economics of Pb and Zn distribution. Two possible stages of hydrothermally driven re-mobilisation are discussed, each
of which produces characteristically different alteration assemblages. Prograde hydrothermal re-mobilisation is driven by
pyrite de-sulphidation and concurrent chlorite dehydration and is thus an internally driven process. At Montauban, the H2S-rich fluid generated through this process allowed re-mobilisation of gold into the wall rock, where it was deposited in
response to sulphidation of Fe Mg silicates. Retrograde hydrothermal re-mobilisation is an externally driven process, whereby
large volumes of fluids from outside the deposit may dissolve and re-precipitate metals, and cause hydration of silicate minerals.
This second hydrothermally driven process is not recognised at Montauban. Sulphide melting occurred as temperatures neared
the peak metamorphic conditions. Melting initiated in the massive sulphides through arsenopyrite breakdown, and a small volume
of melt was subsequently re-mobilised into the wall rock. Trace element partitioning and fractional crystallisation of this
melt generated a precious metal-rich fractionate, which remained mobile until well after peak metamorphism. Thus, prograde
hydrothermal re-mobilisation and sulphide melting were the most important mechanisms for controlling the distribution of Au
and Ag. 相似文献
6.
Much of the exposed Archean crust is composed of composite gneiss which includes a large proportion of intermediate to tonalitic material. These gneiss terranes were typically metamorphosed to amphibolite to granulite facies conditions, with evidence for substantial partial melting at higher grade. Recently published activity–composition (a?x) models for partial melting of metabasic to intermediate compositions allows calculation of the stable metamorphic minerals, melt production and melt composition in such rocks for the first time. Calculated P?T pseudosections are presented for six bulk rock compositions taken from the literature, comprising two metabasic compositions, two intermediate/dioritic compositions and two tonalitic compositions. This range of bulk compositions captures much of the diversity of rock types found in Archean banded gneiss terranes, enabling us to present an overview of metamorphism and partial melting in such terranes. If such rocks are fluid saturated at the solidus, they first begin to melt in the upper amphibolite facies. However, at such conditions, very little (< 5%) melt is produced and this melt is granitic in composition for all rocks. The production of greater proportions of melt requires temperatures ～800–850 °C and is associated with the first appearance of orthopyroxene at pressures below 8–9 kbar or with the appearance and growth of garnet at higher pressures. The temperature at which orthopyroxene appears varies little with composition providing a robust estimate of the amphibolite–granulite facies boundary. Across this boundary, melt production is coincident with the breakdown of hornblende and/or biotite. Melts produced at granulite facies range from tonalite–trondhjemite–granodiorite for the metabasic protoliths, granodiorite to granite for the intermediate protoliths and granite for the tonalitic protoliths. Under fluid‐absent conditions the melt fertility of the different protoliths is largely controlled by the relative proportions of hornblende and quartz at high grade, with the intermediate compositions being the most fertile. The least fertile rocks are the most leucocratic tonalites due to their relatively small proportions of hydrous mafic phases such as hornblende or biotite. In the metabasic rocks, melt production becomes limited by the complete consumption of quartz to higher temperatures. The use of phase equilibrium forward‐modelling provides a thermodynamic framework for understanding melt production, melt loss and intracrustal differentiation during the Archean. 相似文献
7.
Located adjacent to the Banded Gneissic Complex, Rampura–Agucha is the only sulfide ore deposit discovered to date within
the Precambrian basement gneisses of Rajasthan. The massive Zn–(Pb) sulfide orebody occurs within graphite–biotite–sillimanite
schist along with garnet–biotite–sillimanite gneiss, calc–silicate gneisses, amphibolites, and garnet-bearing leucosomes.
Plagioclase–hornblende thermometry in amphibolites yielded a peak metamorphic temperature of 720–780°C, whereas temperatures
obtained from Fe–Mg exchange between garnet and biotite (580–610°C) in the pelites correspond to postpeak resetting. Thermodynamic
considerations of pertinent silicate equilibria, coupled with sphalerite geobarometry, furnished part of a clockwise P–T–t path with peak P–T of ∼6.2 kbar and 780°C, attained during granulite grade metamorphism of the major Zn-rich stratiform sedimentary exhalative
deposits orebody and its host rocks. Arsenopyrite composition in the metamorphosed ore yielded a temperature [and log f(S
2)] range of 352°C (−8.2) to 490°C (−4.64), thus indicating its retrograde nature. Contrary to earlier research on the retrogressed
nature of graphite, Raman spectroscopic studies on graphite in the metamorphosed ore reveal variable degree of preservation
of prograde graphite crystals (490 ± 43°C with a maximum at 593°C). The main orebody is mineralogically simple (sphalerite,
pyrite, pyrrhotite, arsenopyrite, galena), deformed and metamorphosed while the Pb–Ag-rich sulfosalt-bearing veins and pods
that are irregularly distributed within the hanging wall calc–silicate gneisses show no evidence of deformation and metamorphism.
The sulfosalt minerals identified include freibergite, boulangerite, pyrargyrite, stephanite, diaphorite, Mn–jamesonite, Cu-free
meneghinite, and semseyite; the last three are reported from Agucha for the first time. Stability relations of Cu-free meneghinite
and semseyite in the Pb–Ag-rich ores constrain temperatures at >550°C and <300°C, respectively. Features such as (1) low galena–sphalerite
interfacial angles, (2) presence of multiphase sulfide–sulfosalt inclusions, (3) microcracks filled with galena (±pyrargyrite)
without any hydrothermal alteration, and (4) high contents of Zn, Ag (and Sb) in galena, indicate partial melting in the PbS–Fe0.96S–ZnS–(1% Ag2S ± CuFeS2) system, which was critical for metamorphic remobilization of the Rampura–Agucha deposit. 相似文献
8.
This study explores the origin and geochemical evolution ofapatite, monazite, and xenotime along two metamorphic traverses.The first, from the Kigluaik Mountains, Seward Peninsula, Alaska,consists of a localized (85 cm) orthopyroxene–clinopyroxene-bearingdehydration zone. The second consists of orthopyroxene ±clinopyroxene-bearing granulite facies metabasite layers interlayeredwith metapelites over a 3–4 km traverse, along the ValStrona, Ivrea–Verbano Zone, Northern Italy (IVZ). In bothdehydration zones small Th- and U-poor inclusions of monaziteand/or xenotime occur in the apatite. These inclusions are metasomaticallyinduced and nucleated within the apatite via the coupled substitutionsNa+ + (Y + REE)3+ = 2 Ca2+ and Si4+ + (Y + REE)3+ = P5+ + Ca2+.These are not present in apatite from the original amphibolitefacies gneiss. Apatite, in both dehydration zones, also showsa relative increase in both F and Cl compared with apatite fromthe amphibolite facies zone. Granulite facies metabasites inthe IVZ also contain isolated monazite grains, which range fromuniform to complexly zoned in Th the (13–30·1 mol% ThSiO4). These are the product of breakdown and subsequentmobilization of the lanthanides and actinides from monazite-(Ce)in the metapelite layers into the metabasite layers at the startof granulite facies metamorphism. KEY WORDS: apatite; monazite; xenotime; KCl–NaCl brines; metasomatism; phosphate minerals; charnockite–enderbite; granulite facies metamorphism 相似文献
9.
碲作为稀散元素,很少形成独立矿床,主要以共伴生形式产出于多个类型矿床中,包括铜镍硫化物和铂族矿床、铁氧化物铜金(IOCG)矿床、块状硫化物(VMS)矿床、斑岩矿床、矽卡岩矿床、造山型金矿、卡林型金矿和浅成低温热液矿床等。研究表明,碲元素可以形成上百种碲矿物,除了自然碲之外,多与Au、Ag、Pb、Bi、Cu等形成碲化物,与S或者Se形成碲的硫化物或硒化物,也可以形成碲酸盐、硅酸盐、磷酸盐、硫酸盐等矿物;此外Te还可以以类质同象形式替换寄主矿物中的元素。在成矿带尺度、矿床尺度及其矿石中碲均表现出极不均匀的分布特征,与主矿种Cu、Au、Ag等具有成因关系。碲具有多来源特征,可以源自地幔,也可以是浅部壳源岩浆或是围岩地层提供。碲矿化一般发生在成矿的中晚阶段,流体可通过混合作用、水岩反应、沸腾作用等改变体系的物理化学条件(如pH值、硫逸度、氧逸度、碲逸度、温度等),导致流体pH值升高、硫逸度和氧逸度降低,碲逸度升高,这是诱发碲矿物富集和沉淀的主要机制。碲由于其受控成矿条件较为特殊,需要着重加强碲富集成矿的关键控制因素、成矿物质来源和富集沉淀机制的研究。 相似文献
10.
W. R. Ryall 《Mineralium Deposita》1981,16(3):425-435
Mercury concentrations of four Australian stratiform lead-zinc-silver deposits of Proterozoic age are not directly related to their metamoprhic grade and are probably determined by local factors. Average mercury contents of H. Y. C. mineralization (unmetamorphosed) is 1300 ppb, Mount Isa ore (greenschist facies) 8300 ppb, Squirrel Hills mineralization (amphibolite facies) 100 ppb, and Broken Hill ore (granulite facies) ranges from 1000 ppb for A lode to 37000 ppb for No. 3 lens. In present-day sulfidic muds from the Coorong region of South Australia, mercury is present as mercury sulfide either as inclusions or chemisorbed on mackinawite. This may be analogous to the manner of mercury occurrence in sediments which predated the ingress of lead-zinc-silver mineralization into ancient basins. In bedded H. Y. C. mineralization mercury is present principally in pyrite, but recrystallized mineralization contains mercury in both sphalerite and pyrite. In bedded Mount Isa ore mercury is present in sphalerite, but in remobilized ore which is enriched in galena, freibergite and pyrrhotite, it occurs in both sphalerite and freibergite. Mineralization from Squirrel Hills contains no tetrahedrite, and sphalerite is the host for most mercury. Normal Broken Hill ore contains mercury parti tioned approximately evenly between sphalerite and tetrahedrite, but mercury is enriched in remobilized ore. Veins generated during retrograde metamorphism of the Broken Hill lodes contain high levels of mercury, and multiple veins produced in this fashion around other deposits could result in mercury haloes that can be detected during exploration programs. The way mercury is held in stratiform leadzinc-silver deposits, and the lack of decrease of mercury contents with increasing metamorphic grade, rules out total loss of mercury during metamorphism. Primary mercury haloes around this type of mineralization are due to mercury in disseminated ore-forming minerals or late-stage vein systems contain secondary mercury-bearing minerals. 相似文献
11.
小营盘金矿床的含金石英脉主要赋存在两个地层单位中,第一个是浅色的麻粒岩段,第二个是暗色的变粒岩段。变火山岩地球化学特征表明,它们生成的最有利的构造环境是岛弧模式;控矿构造是倒转向斜翼部的冲断层;容矿围岩变质级别达到角闪岩相和麻粒岩相。根据物理化学条件所计算的金的成色与国外金矿床相比,该矿床是近地表条件下形成的。 相似文献
12.
Martin Schwindinger Roberto F. Weinberg Frediano Clos 《Journal of Metamorphic Geology》2019,37(3):339-358
Partial melting of continental crust and evolution of granitic magmas are inseparably linked to the availability of H2O. In the absence of a free aqueous fluid, melting takes place at relatively high temperatures by dehydration of hydrous minerals, whereas in its presence, melting temperatures are lowered, and melting need not involve hydrous minerals. With the exception of anatexis in water‐saturated environments where anhydrous peritectic minerals are absent, there is no reliable indicator that clearly identifies the presence of a free aqueous fluid during anatexis. Production of Ab‐rich magmas or changes in LILE ratios, such as an increase in Sr and decrease in Rb indicating increased involvement of plagioclase, are rough guidelines to the presence of aqueous fluids. Nevertheless, all indicators have caveats and cannot be unequivocally applied, allowing for the persistence of a bias in the literature towards dehydration melting. Investigation of mineral equilibria modelling of three metasedimentary protoliths of the Kangaroo Island migmatites in South Australia, shows that the main indicator for the presence of small volumes of excess water under upper amphibolite to lower granulite facies conditions (660–750°C) is the melt volume produced. Melt composition, modal content or chemical composition of peritectic minerals such as cordierite, sillimanite or garnet are relatively insensitive to the presence of free water. However, the mobility of melt during open system behaviour makes it difficult to determine the melt volume produced. We therefore argue that the presence of small volumes of excess water might be much more common than so far inferred, with large impact on the buffering of crustal temperatures and fertility, and therefore rheology of the continental crust. 相似文献
13.
The investigation of melt inclusions in the minerals of volcanic rocks from the massive sulfide deposits of Siberia and the Urals revealed some specific features in the development of their magmatic ore systems. It was shown that the petrochemical and rare earth element compositions of melt inclusions reflect the geodynamic conditions of their formation: island arc conditions for the massive sulfide deposits of Rudny Altai, eastern Tuva, and the Salair Range and a back arc basin environment for the Yaman-Kasy deposit. The silicic melts of inclusions from the volcanic rocks of massive sulfide deposits show some specific features with respect to the contents of volatile components. In all of the ore deposits studied, fluorine content was always low (0.03–0.08 wt %), whereas chlorine content (0.13–0.28 wt %) was higher than the average value for silicic melts (0.17 wt %). There is a strong differentiation of water content in melt inclusions, both between deposits and between various volcanics from a single deposit. Ore-bearing melts show the highest water contents of 3.34–4.07 wt %. High Cu contents in the silicic melts of the Yubileinoe and Kyzyl-Tashtyg deposits (up to 7118 and 3228 ppm, respectively) may indicate the affinity of some ore components to particular silicic magmas. This is supported by the elevated contents of Cu in the porphyry Cu deposits of Romania (Valea Morii), Mongolia (Bayan Ula), and Bolivia. On the other hand, the silicic melts of inclusions from the molybdenum-uranium deposit of the Strel’tsovka ore field show high contents of another group of ore components (U and F). 相似文献
14.
Using In Situ Trace-Element Determinations to Monitor Partial-Melting Processes in Metabasites 总被引：4，自引：0，他引：4
Peak metamorphism (800–850°C, 8–10 kbar) inthe Harts Range Meta-Igneous Complex (Harts Range, central Australia)was associated with localized partial melting by the reactionhornblende + plagioclase + quartz + H2O = garnet + clinopyroxene+ titanite + melt. In situ trace-element determinations of prograde,peak and retrograde minerals in migmatitic metabasites and associatedtonalitic melts using laser-ablation ICP–MS has allowedmonitoring of a range of partial-melting processes (melting,melt segregation and back-reaction between crystallizing meltand restitic minerals). Mass balance calculations indicate thattitanite is a major carrier of trace elements such as Ti, Nb,Ta, Sm, U and Th, and therefore may be an important accessoryphase to control the redistribution of these elements duringthe partial melting of amphibolites. Titanite preferentiallyincorporates Ta over Nb and, hence, residual titanite mightassist in the formation of melts with high Nb/Ta. The fact thatsingle minerals record different rare earth element (REE) patterns,from prograde to peak to retrograde conditions, demonstratesthat REE diffusion is not significant up to 800°C. Therefore,trace-element analysis in minerals can be a powerful tool toinvestigate high-grade metamorphic processes beyond the limitsgiven by major elements. KEY WORDS: Harts Range; laser-ablation ICP–MS; metabasites; partial melting; trace elements 相似文献
15.
南岭铋矿床的产出特征及成因探讨 总被引：1，自引：0，他引：1
南岭成矿带是我国乃至世界上最重要的铋矿产地。该区铋矿床的研究尽管起步较早,但进展缓慢,其产出特征及成因认识仍很薄弱。本文通过系统搜集、综合分析矿山基础地质资料和前人研究成果,在时空分布规律、含铋矿物类型、矿床成因等方面取得一定认识。南岭成矿带有湘南、粤北、崇-余-犹、于-赣等四大铋矿聚集区;铋矿床类型主要有石英脉型、矽卡岩型、蚀变花岗岩型、破碎带型、充填交代型、斑岩型等六种,以石英脉型铋矿数量最多,矽卡岩型铋矿储量最大;铋矿床形成年龄介于170~150 Ma之间,与相关花岗岩体侵入年龄相近。目前已发现含铋矿物30余种,涵盖自然元素、硫化物、含硫盐、氧化物、含氧盐、碲化物、铋化物、氟化物等类型,以铋的含硫盐最为丰富。含铋矿物组合在不同类型铋矿床中有所差异,但一般产在矿脉中下部,且由浅至深矿物中硫的原子百分比呈下降的趋势。南岭铋矿床的主要成矿物质来自花岗岩浆,在花岗岩浆形成过程中有地幔流体的加入,成矿中晚阶段大气降水的混入可能是铋大量沉淀的重要因素。 相似文献
16.
Ahmed G. Abd Allah 《Arabian Journal of Geosciences》2012,5(2):217-231
Volcanic-hosted (Cu–Zn–Pb) massive sulfide mineralizations are described from four prospects in the Eastern Desert: Helgate,
Maaqal, Derhib, and Abu Gurdi. Helgate and Maaqal prospects are hosted in island arc volcanics in a well-defined stratigraphic
level. Massive sulfides form veins and lenses. Although these veins and lenses are locally deformed, sulfides from Helgate
and Maaqal prospects show primary depositional features. They form layers and colloidal textures. Sphalerite, pyrite, chalcopyrite,
and galena are the major sulfides. Gangue minerals are represented by chlorite, quartz, and calcite. The sulfide mineralizations
at Helgate and Maaqal are Zn-dominated. Derhib and Abu Gurdi prospects occur as disseminations, small massive lenses, and
veins along shear zones in talc tremolite rocks at the contact between metavolcanics and metasedimentary rocks. The host rocks
at Derhib and Abu Gurdi are metamorphosed to lower amphibolite facies as revealed by silicate mineral assemblage and chemistry.
Chalcopyrite, pyrite, sphalerite, and galena are the major sulfide minerals while pyrrhotite is less common. Recrystallization,
retexturing and remobilization of sulfide minerals are reflecting postdepositional metamorphic and structural modifications.
Electrum and Ag–Pb–Bi tellurides are common accessories. Gangue minerals comprise amphiboles of actinolite and actinolitic
hornblende composition, talc, and chlorite. The ores at Derhib and Abu Gurdi are Cu–Zn and Zn-dominated, respectively. The
distinct geological, petrographical, and geochemical differences between sulfide mineralizations at Helgate–Maaqal on one
hand and Derhib and Abu Gurdi on the other hand suggest two genetic types of sulfide mineralizations; Helgate–Maaqal prospects
(type 1) are similar to the Archean analogs from Canada (Noranda type), while Derhib and Abu Gurdi (type 2) show similarity
to ophiolite-associated deposits similar to those described from Cyprus, Oman, and Finland. In genetic type 1, ore minerals
were deposited on the seafloor; the role of postdepositional hydrothermal activity is limited. In genetic type 2, base metals
were part of the ultramafic rocks and were later redistributed and mobilized during deformation to be deposited along shear
zones. The dominance and diversity of tellurides in genetic type 2 highlight the role of metamorphic–hydrothermal fluids. 相似文献
17.
新疆哈密黄山地区铜镍硫化物矿床的稀土元素特征及意义 总被引：29，自引：9，他引：20
通过对新疆哈密黄山铜镍矿带典型矿床矿石矿物和含矿岩石的稀土元素地球化学研究,发现产于造山带的铜镍硫化物矿床的容矿镁铁-超镁铁质岩具有富水特征,部分硫化物稀土曲线呈特殊的“三重弯曲”模式,反应出由于多种液相(流体和熔体)共存,硫化物熔体中含有大量热液流体,在主成矿期(岩浆熔离期)后逐渐演化出富含气液的成矿流体。本区矿床稀土特征不同于克拉通边缘的铜镍矿床,造成上述热液流体参与成矿的原因在于含矿岩体本身富水,可能与碰撞后富水洋壳的拆沉熔融有关。 相似文献
18.
《Resource Geology》2018,68(3):209-226
Shin‐Otoyo, Suttsu, Teine, Date, Chitose, and Koryu are sites rich in precious and base metal Miocene–Pleistocene epithermal deposits, and located in southwestern Hokkaido, Japan. The deposits are predominantly hosted by the Green Tuff Formation of Middle Miocene age. Ore petrographic study of these deposits shows the occurrence of variable quantities of Cu–As–Sb–Ag–Bi–Pb–Te sulfosalt minerals. Determination of mineralogical and chemical compositions of the sulfosalt minerals was undertaken to elucidate the time and spatial changes of the sulfide‐sulfosalt minerals. Various types of sulfosalt minerals identified from gold–silver and base metal quartz–sulfide veins represented some sulfosalt mineralization phases, such as the Cu–Fe–Sn–S phase of mawsonite and stannite; Cu–(As,Sb)–S phase of tetrahedrite–tennantite and luzonite–famatinite series minerals; (Cu,Ag)–Bi–Pb–S phase of emplectite, pavonite, friedrichite, aikinite, and lillianite–gustavite series minerals; (Ag,Cu)–(As,Sb)–S phase of proustite–pyrargyrite and pearceite–polybasite series minerals; and Bi–Te–S phase of tetradymite and kawazulite minerals. There are some trends in the paragenetic sequence of sulfosalt mineralization in southwestern Hokkaido (in complete or partial) as follows: sulfide → Cu–Fe–Sn–S → (Cu,Ag)–Bi–Pb–S → (Bi–Te–S) → Cu–(As,Sb)–S → ([Ag,Cu]–[As,Sb]–S). The formation of sulfosalt minerals is characterized by the introduction of some elements such as Sn, Bi, and Te at an earlier stage and an increase or decrease of some elements such as As and Sb, followed by the introduction of Ag at the later stage of ore mineral paragenesis sequence. Mineral composition of the Chitose and Koryu deposits are slightly different from those of Shin‐Otoyo, Suttsu, Teine, and Date due to their lack of Sn (tin) and Bi (bismuth) mineralization. The variable concentrations and relationships are not simply with redistributed trace elements from the original sulfide minerals of chalcopyrite, pyrite, galena, and sphalerite. Some heavier elements were also introduced during the replacement reaction, which is consistent with the occurrence of their associated minerals. 相似文献
19.
H. Wayne Nesbitt 《Contributions to Mineralogy and Petrology》1980,72(3):303-310
Materials balance calculations on amphibolite facies and granulite facies rocks from the Adirondack region and from some areas of New Quebec demonstrate that the rocks of the two facies differ by near granite-minimum melt compositions. The implication of these results are; granulites of both regions result from partial melting of greywacke-type metasedimentary rocks during upper amphibolite facies metamorphism. The New Quebec region contains granuites produced by partial melting as well as granulites produced by simple mineral dehydration reactions (no melting of the rocks occurred). These observations combined with the knowledge that some New Quebec granulites have produced abnormally high quantities of melts provide evidence that large sources and sinks for H2O exist in the lower crust and that there is significant H2O transport between these regions. 相似文献
20.
鞍本太古代绿岩盆地铁矿的成矿特征 总被引：5，自引：0，他引：5
辽宁省鞍山本溪地区是我国著名的铁矿产区。对于本区鞍山式铁矿的成矿特征,作者在前人工作的基础上,经过三年多的调查研究,认为本区鞍山式铁矿不是一种单一的矿床类型,而是赋存在不同时代、不同大地构造环境的两种矿床系列,即属于阿尔戈马型铁矿系列和苏必利尔型铁矿系列。并在划分成矿系列的基础上提出了本区的成矿模式。 相似文献