The Characteristics of Migration of Ore Solutions in No.6 East Tin Deposit of the Songshujiao Orefield, Gejiu

No. 6 East tin deposit in the Songshujiao orefield, Gejiu, is characterized by one-stage hydrothermal activity and monotonous country rocks. The authors selected this deposit and used the multivariate statistical analysis to study the types of association of main ore-forming elements at different temperatures and pressures and their distribution in the deposit. On that basis combined with the structural analysis of the deposit, the recto-geochemical features of No.6 East tin deposit have been revealed and the direction and channel of migration of the ore solutions in faults and the deposit have been deduced. This research can appropriately elucidate the control of faults on the migration of ore solutions and the sites where ore solutions are dispersed and accumulated, thus providing the theoretical basis for the prediction of hydrothermal deposits in question.     

Speciation and Precipitation of Uranium Complexes in Hydrothermal Solutions Related to Granite—type Uranium Deposits

Uranium-bearing hydrothermal solutions during the stage of ore deposition are weakly alkaline and of the Ca^2 -Na^ /HCO3^- -F^- type.UO2(CO3)2^2- and UO2F4^-, are dominant in the hydrothermal solutions with respect to their activity.Wall-rock hydrothermal alterations ,temperature and pressure drop and the reducing capability of rock assemblage (Δeh) led to a decrease in Eh of the hydrothermal solutions and an increase in Eh at which uranium began precipitating.Therefore,the mechanism of uranium precipitation is essentially the reduction of uranium complexes.The granite-type uranium deposits are the most important type of uranium resources in China.Discussions will be made in this paper concerning the hydrothermal speciation and precipitation mech-anisms of uranium complexes in the light of fluid inclusion and geological data from some major de-posits of this type in South China.     

Pegmatite fluids of different origins and their implications for mineralization

Characteristics of ore-forming fluids as inferred from detailed studies of inclusions indicate that pegmatites may have different origins.For example,the granitic pegmatite at Mufushan is originated from magma differentiation at 1100-200℃,while the No.3 Pegmatite Vein in Xinjiang may owe its origin to a pegmatitic magma produced via metamorphic anatexis at 1140-200℃.Pegmatite fluids of the above two types are a melt-liquid system and may evolve into a solid-melt or solid-liquid system that would have a critical bearing on metasomatism and intergranular solutions.The Minxi pegmatite,on the oter hand,resulted from metamorphic differentiation,with its fluid(formed at 400-180℃）exhibiting many features of metamorphism.Pegmatites of different origins are distributed in tectonic units of different characters and are different bot in the nature of ore-foming fluid and in the source of ore-metals.This concept of polygene launches a challenge to the traditional belief that pegmatite is exclusively originated from magma differentiation and may be helphfou for the establishment of a new theory of pegmatite genesis.     

Physicochemical Conditions of the Formation of Beryl and Aquamarin in Mufushan Granopegmatite Deposit,Hunan Province,China

The formation of the Mufushan granopegmatite was closely related to the Late Yenshanian multiphase and multistage magmatic activities,More than one generation of beryl and aquamarine occur in different types of pegmatite in the granites.The presence of melt and melt-fluid inclusions strongly indicates a melt-solution character of the pegmatitic magma.Forming temperatures of the different generations of beryl in a Na^ -K^ ,Ca^2 -CO3^2--Cl^--SO4^2- solution ranges from 990℃to 200℃.Aquamarine was formed at 720-180℃.The contents of alkali metals(Na^ K^ )in th ore-formming solution of aquamarine are lower than those in the beryl,but the contents of alkali earths(Ca) and salinity are higher,The granite was generated by remelting of the basement formation(meta-sedimentary rocks of the Lengjiaxi Group)which also served as the source of ore-forming material.Beryllium in the pegmatite was transported mainly in the form of Na[Be(CO3)2],with part of it being complexed with Cl^- and SO4^2-.During the generation and evolution of the pegmatite,equilibrium might have been reached in the solid-melt-fluid or solid-fluid system.The intergranular solutions may have reacted with the early crystallized minerals,resulting in potash-feldsparization,albitization and muscovitization during which the ore-forming elements were mobilized and transported in favour of ore deposition.     

Fluid Inclusion Studies and Geochemistry of Rare Earth Elements of Hydrothermal Fluorites from Pohrenk, Kirsehir, Central Turkey

Fluorite mineralization occurs along fractures and cracks of Middle Eocene and Pliocene limestones and marls in the north and northeast of the Pohrenk region (Qicekdagi, Kirsehir). Tb/Ca - Tb/La and Y/Ho ratios were obtained from REE contents of fluorites which have revealed that mineralization is of hydrothermal type. Negative Ce anomalies and positive Eu anomalies reflect that hydrothermal solutions once had high oxygen fugacity. Fluid inclusion studies indicate that homogenization temperatures of mineralization varied between 90℃ and 200℃, and hydrothermal solutions are composed of NaCl + KCl + MgCl2 + H2O. In addition, salinity measurements show that hydrothermal solutions were mixed with meteoric or rock formation water. Geologic setting, REE geochemistry and fluid inclusion studies suggest that mineralization was deposited from a solution generated by mixing of magmatic and meteoric water under epithermal conditions.     

Geochemical Characteristics of Gold Polymetallic Deposits as Exemplified by the Laozuoshan Deposit,Heilong jiang,China

From the studies of ore deposit geologic settings,sulfur isotopes,lead isotopes,carbon isotopes and oxygen isotopes,fluid inclusions and petrochemistry in this paper,the authors have drawn a conclusion that the ore-forming hydrothermal solutions are the high-temperature magmatic hydrothermal solutions for the gold ore deposit,and at the same time,the involvemety of crustal materials can not be ruled out .It is the first time that the authors have proposed that the Laozuoshan gold-ploymetallic ore deposit in Heilongjiang Province was formed in the calc-alkaline series environment at the margin of an active continent.     

Fluid Characteristics and Evolution of the Zhawulong Granitic Pegmatite Lithium Deposit in the Ganzi‐Songpan Region,Southwestern China

The Zhawulong granitic pegmatite lithium deposit is located in the Ganzi-Songpan orogenic belt. Fluid inclusions in spodumene and coexisting quartz were studied to understand the cooling path and evolution of fluid within albite–spodumene pegmatite. There are three distinguishable types of fluid inclusions: crystal-rich, CO2–NaCl–H2O, and NaCl–H2O. At more than 500°C and 350~480 MPa, crystal-rich fluid inclusions were captured during the pegmatitic magma-hydrothermal transition stage, characterized by a dense hydrous alkali borosilicate fluid with a carbonate component. Between 412°C and 278°C, CO2–NaCl–H2Ofluid inclusions developed in spodumene (I) and quartz (II) with a low salinity (3.3–11.9 wt%NaCl equivalent) and a high volatile content, which represent the boundary between the transition stage and the hydrothermal stage. The subsequentNaCl–H2Ofluid inclusions from the hydrothermal stage, between 189°C and 302°C, have a low salinity (1.1–13.9 wt%NaCl equivalent). The various types of fluid inclusions reveal the P–T conditions of pegmatite formation, which marks the transition process from magmatic to hydrothermal. The ore-forming fluids from the Zhawulong deposit have many of the same characteristics as those from the Jiajika lithium deposit. The ore-forming fluid provided not only materials for crystallization of rare metal minerals, such as spodumene and beryl, but also the ideal conditions forthe growth of ore minerals. Therefore, this area has favorable conditions for lithium enrichment and excellent prospecting potential.     

Petrologic and Geochemical Characteristics and Origin of Gusui Cherts,Guangdong Province,China

The characteristic structures of the Precambrian cherts from the Gusui section, Guangdong ,Chi-na, include bedded structure ,laminated structure ,massive structure and pseudobrecciated structure.The chert is characterized by consistently low abundance of TiO2,Al2O3 and most trace elements.Howevver ,it is enriched in Ba,As,Sb,Hg and Se.In Al-Fe-Mn ternary diagrams,it falls into the “hydrothermal field“ .Correspondence analysis and factor analysis show that many elements show up in the factor that represents the leaching of country rocks by hydrothermal solutions,and are the very characteristic element association fo the geochemically anomalous South China basement.Petrologic and geochemical evidence suggests a hydrothermal origin for the chert.The chert may have been formed in a Precambrian fift or an extension zone developed within the Yunkai marginal geosyncline, with a fault system linking it to an unknown heat source at depth.     

Isotope Geochemistry of Gold Ore Deposits in the Gezhen Shear Zone, Qiongxi, Hainan Island

Gold deposits hosted in the Gezhen shear zone at Qingxi, Hainan Island occur in the Preeambrian metamorphic rock series and are regionally developed in the N-E direction along the tectonic zone. From northeast to southwest are distributed the Tuwaishan-Baoban gold mining district, the Erjia gold mining district and the Bumo gold mining district, making up the most industrially important gold metallogenesis zone on the Hainan Island. Isotope geochemical studies of the typical gold deposits in this metallogenesis zone indicate that their ore-forming materials stemmed largely from the Baoban Group migmatite series, though the involvement of some plutonic materials could not be ruled out. The ore fluids are the mixture of migrnatitized hydrothermal solutions and meteoric waters in addition to the involvement of local magmatic hydrothermal solutions. The superimposition of plutonie materials and magmatic hydrothermal solutions is controlled by the deformation environment of the shear zone and later magrnatic activities. Obvious variations are noticed in isotopic composition in the region studied, probably related to tectonic deformation, metamorphism and other evolutionary characteristics. This study is of great significance in understanding the relationship between the shear zone and gold metallogenesis,the rules of gold metallogenesis and gold ore prognosis.     

The Mobility of Rare—Earth Elements During Hydrothermal Activity：A Review

The mobility of the rare-earth elements(REE)during hydrothermal activities is increasingly documented.Geological and experimental evidence suggests that REE may be mobile in solutions rich in F^-,Cl^-,HCO3^-,CO^2- 3,HPO4^2-,PO4^3-,or in combinations of the above ligands,even though little has been known about which ligand or which combination is most effective in mobilizing REE. The fractionation of REE resulting from hydrothermal activities is inconsistent.One set of field data implies the prererential mobility of the light rare-earth elements(LREE).whereas another set of field observations indicates the dominant mobilization of the heavy rare earth elements(HREE),and some theoretical prediction is comtradictory to the field evidence.The Eu anomalies due to hydrothermal activities are complex and plausible explanation is not available.The existing experimental approaches dealing with REE are not adequate for explanation ofREE behaviour in aqueous solutions.Systematic experimental approaches are suggested.     

岩浆-流体过渡和阿尔泰三号伟晶岩脉之成因

本文对新疆阿尔泰可可托海的三号伟晶岩形成的物理化学条件、特别是流体-熔融包裹体进行了研究，证明岩浆的确可以分出热液，对于三号伟晶岩脉来说，这种热液组分主要是NaCl－CO2－H2O流体。     

新疆阿尔泰可可托海伟晶岩型稀有金属矿床中磷灰石地球化学特征及意义

磷灰石可以记录和保存岩浆和热液活动的信息。可可托海伟晶岩型稀有金属矿床磷灰石发育,为研究该矿床伟晶岩成岩成矿过程提供了优良的条件。已有对可可托海伟晶岩型稀有金属矿床磷灰石的研究集中在其稀土元素特征,较少讨论其对伟晶岩成岩成矿过程的制约。本文选取可可托海伟晶岩型稀有金属矿床富矿伟晶岩脉（3号脉）和相对贫矿伟晶岩脉（1号、2b号和3a号脉）中的磷灰石作为研究对象,进行磷灰石岩相学和地球化学研究。岩相学分析表明,磷灰石主要与钠长石、石英、白云母、锰铝榴石等伴生。EPMA分析显示,磷灰石F含量为3.67%~4.41%,Cl含量小于0.67%,较低的Cl含量表明伟晶岩熔体出溶的流体Cl含量较低;大部分磷灰石MnO含量为4.67%~8.71%,但2b号脉磷灰石MnO含量变化较大（1.23%~14.28%）,这是由于2b号脉磷灰石具有分带结构,暗示其遭受后期热液作用,促使磷灰石溶解-再沉淀,导致MnO含量发生较大变化。LA-ICP-MS分析显示,贫矿伟晶岩脉磷灰石的稀土元素含量较低（< 180×10^-6）;相反,富矿伟晶岩脉磷灰石的稀土元素含量较高（>700×10^-6）,并具有明显的四分组效应（TE_1-3平均值为1.7）。1号脉和3a号脉磷灰石均显示轻稀土元素富集,反映其形成过程中有含Cl热液的参与。3号脉磷灰石显示强烈Eu负异常和Ce正异常,而2b号脉磷灰石显示强烈Ce负异常和中等Eu负异常,这种Eu、Ce异常的差异可能与岩浆-热液阶段大量流体出溶密切相关。磷灰石的沉淀将导致热液中HF含量的降低,促使磷灰石周围铌钽矿结晶和Nb、Ta进入磷灰石中。可见,在伟晶岩形成过程中,磷灰石并非保持稳定,其分带结构和主微量成分变化记录了后期热液活动,暗示后期热液活动对伟晶岩的成矿具有重要作用。

     

Chemical composition and species attribution of tourmalines from a rare-metal pegmatite vein with scapolite, Sangilen Upland, Tuva

A detailed study of the chemical composition and substitutions in calcium tourmalines from a scapolite-bearing rare-metal pegmatite vein from the Sol’bel’der River basin has shown that their species attribution is determined by occupancy of octahedral site Y. The composition of the yellow tourmaline most abundant in the central part of the pegmatite bodyis rather constant and characterized by the ideal formula Ca(Mg₂Li)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃F. Variations in the chemical composition of zonal tourmaline crystals from the contact part of the pegmatite are controlled by abrupt change in the chemical medium during their formation. The yellow cores of these crystals are close in composition to tourmaline from the central part of the pegmatite vein. The Mg content abruptly decreases toward the crystal margin: Mg²⁺ → Fe²⁺, 2Mg²⁺ → Li⁺ + Al³⁺, and Mg²⁺ + OH → Al³⁺ + O²⁻. The composition of dark green marginal zones in tourmaline is characterized by the ideal formula Ca(Al_1.5Li_1.5)Al₆(Si₆O₁₈)(BO₃)₃ (OH₂O)(F). The results indicate specific formation conditions of pegmatite. The crystallochemical formulas of the studied tourmalines allow us to regard them as new mineral species in the tourmaline group.     

Fluid—Melt and Fluid Inclusions in Mianning REE Deposit,Sichuan Southwest Cina

Abundant fluid-melt inclusions are found in the aegirine-augite-barite pegmatite and carbonatite veins in the Mianning REE deposit,Sichuan,They were trapped in early stage fluorite and quartz from a salt-melt system at temperatures higher than 5000℃,Meanwhile,fluid inclusions are also present in alrge amounts in bastnaesite.Homogenized between 150 and 270℃,these inclusions are thought to be representative of the physico-chemical conditions of REE mineralization.These results show that the Mianning REE deposit is of typical hydrothermal origin developed from a salt-melt system.     

Silicalites of Hydrothermal Origin in the Lower Cambrian Black Rock Series of South China

A silicalite bed was found in the hanging wall and foot wall of the sulfide-rich bed of the Lower Cambrian black rock series in South China.Its origin was not described before,On the oxide(SiO2-Al2O3,SiO2-MgO,SiO2-k2o Na2O)diagrams for discriminating silicalites of chemical,biological and volcanic origins(Liu Xiufeng,1991),most of the data points of silicalites fall within the areas representing silicalites of chemical and volcanic origins.On the Al-Fe-Mn diagram for discriminating silicalites of hydrothermal and biological origins(Yamamoto,1987),the data points fall within the areas representing silicalites of hydrotermal and hydrothermal-biological origins.On the SiO2-Al2O3 diagram for discriminating silicalites of hydrothermal and hydrogenous origins(Bonatti,1975),the data points mostly fall within the hydrothermal area.The ratios of SiO2/Al2O3,SiO2/(K2O Na2O),SiO2/MgO,and K2O/Na2O in the silicalites stand between those of volcanic sediments and of seafloor hydrothermal sediments.The total amount of rare-earth elements in the silicalites is low;the North american Shale-normalized REE patterns decline leftward with obvious negative Ce anomaly.The trace elements Mo,Zn,As,Sb,Se,U,and Ba are higher than those in non-hydrothermal sediments and U/Th≥1.The present authors think that the silicalites are derived from seafloor hot brines which had attracted elements from igneous rocks.     

Compositional evolution of grossular garnet from leucotonalitic pegmatite at Ruda nad Moravou, Czech Republic; a complex EMPA, LA-ICP-MS, IR and CL study

Five distinct paragenetic, morphological and compositional types of grossular garnet (G1, G2, G3, G4, G5) were distinguished within the individual (sub)units of the zoned leucotonalitic pegmatite cutting serpentinized lherzolite with rodingite dikes at ??ár near Ruda nad Moravou, Staré Město Unit, Northern Moravia. Detailed study using Electron Microprobe Analysis, Laser Ablation Inductively Coupled Plasma Mass Spectrometry, Cathodoluminiscence and Infrared Spectroscopy revealed distinct compositional trends in major, minor and trace elements. The contents of Fe³⁺, Mn, Mg and Ti increase from early garnet (G1) in the outermost grossular subunit through the interstitial garnet (G2) in the leucocratic subunit to graphic intergrowths of quartz+garnet (G3) in the coarse-grained unit. Then these constituents decrease in inclusions of garnet (G4) from the blocky unit and large crystals of garnet (G5) from the quartz core. Some trace elements (V, Ni, Y) exhibit the same trends, only Be evidently increases in garnet from border zone to the centre. Fluorine has negative correlation with Fe³⁺ as well as some trace elements (Ta, Pb). Concentrations of H₂O in garnets, up to 0.22 wt.% H₂O, are comparable with spessartine-almandine garnets from the Rutherford No. 2 pegmatite, Virginia, and grossular garnets from high-temperature calc-silicate rocks (skarns). Water contents correlate positively with Fe³⁺, but inversely with F. The use of water contents in garnet to elucidate the fluctuations of activity of H₂O during the pegmatite formation is only limited; the incorporation of hydrous defects seems to be controlled instead by crystal-structural constraints. However, the sum of all volatile components (H₂O + F) increases about twice from the outermost subunit to the centre of the pegmatite body.     

Formation Age and Evolution Time Span of the Koktokay No. 3 Pegmatite,Altai, NW China: Evidence from U–Pb Zircon and 40Ar–39Ar Muscovite Ages

The Koktokay No. 3 pegmatite is the largest Li–Be–Nb–Ta–Cs pegmatitic rare‐metal deposit of the Chinese Altai orogenic belt, and is famous for its concentric ring zonation pattern (nine internal zones). However, the formation age and evolution time span have been controversial. Here, we present the results of LA‐ICP–MS zircon U–Pb dating and muscovite ⁴⁰Ar–³⁹Ar dating. Four groups of zircon U–Pb ages (～210 Ma, ～193–198 Ma, ～186–187 Ma and ～172 Ma) for Zones II, V, VI, VII, and VIII, and a weighed mean ²⁰⁶Pb/²³⁸U age of 965 ± 11 Ma for Zone IV are identified. Also, Zones II, IV, and VI have muscovite ⁴⁰Ar–³⁹Ar plateau ages of 179.7 ± 1.1 Ma, 182.1 ± 1.0 Ma, and 181.8 ± 1.1 Ma, respectively. Considering previous U–Pb age studies (Zones I, V, and VII), the ages of emplacement, Li mineralization peak, hydrothermal stage of the No. 3 pegmatite are in ranges of 193–198 Ma, 184–187 Ma and 172–175 Ma, with weighted mean ²⁰⁶Pb–²³⁸U ages of 194.8 ± 2.3 Ma, 186.6 ± 1.3 Ma and 173.1 ± 3.9 Ma, respectively. The No. 3 pegmatite formed in the early Jurassic. The results of xenocrysts suggest that there is another pegmatite forming event of around 210 Ma in the mining district and the old zircon U–Pb ages imply that Neoproterozoic crustal rocks pertain to sources of the No. 3 pegmatite. Including the previous muscovite ⁴⁰Ar–³⁹Ar age studies (Zones I and V), a cooling age range of 177–182 Ma is considered as the time of hydrothermal stage and end of formation. The evolution process of the No. 3 pegmatite lasted 16 Ma. Therein, the magmatic stage continued for 9–11 Myr and the magmatic–hydrothermal transition and hydrothermal stages were sustained at 5–7 Ma. These time spans are long because of huge scale, cupola shape, large formation depth, and complex internal zoning patterns and formation processes. Considering some pegmatite dikes in the Chinese Altai, there is an early Jurassic pegmatite forming event.     

Research on fluid inclusions of the Yinshan polymetallic deposit, Jiangxi Province, China

In this paper some new advances in the study of fluid inclusions of the Yinshan deposit in Jiangxi Province,China,are presented.The fluid inclusions of the deposit can be divided into four types:1) gas-rich inclusions;2)liquid-rich inclusions;3)salt-saturated H2O inclusions;and 4)single-phase or multiphase CO2-rich inclusions.Homogenization temperatures of the fluid inclusions range from 100 to 520℃,aminly in the range 120-400℃.The daughter crystal-bearing multiphase inclusions present in quartz porphyries(including Nos.13 and 4 dikes)have been observed.In ore veins,some daughter crystal-bearing multiphase inclusions have been observed.too.On the basis of the results of fluid inclusion research,the authors suggest that the ore-forming fluid must have a close genetic relation to magmatic hydrothermal solution.The ore-forming fluid was dominantly originated from the depth and the mixing of magmatic solution with meteoric water was enhanced during ascending of the fluid,accompanying immiscibility and boiling of fluid.Teher may be a conceales igneous body at the depth of the Yinshan deposity,which furnishes the scientific basis for metallogenic prognosis at th depth of the Yinshan deposit.