Geochemistry of Granites Associated with Tantalum and Niobium Mineralization

Pollard, P. J.

doi:10.1007/978-3-642-87262-4_5

Cited by 24 publications

(16 citation statements)

References 35 publications

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“…They were generally considered as highly differentiated magmas deriving by fractionation from the spatially associated leucogranites (Pollard 1989), but recent studies suggest that they may derive from an independent magma ). In the Limousin area, the RMG appear either as pegmatitic, microgranitic to rhyolitic dykes, or as small granitic cupolas.…”

Section: The Main Types Of Granitoidsmentioning

confidence: 99%

Relationships between granitoids and mineral deposits: three-dimensional modelling of the Variscan Limousin Province (NW French Massif Central)

Veslud¹,

Cuney²,

Royer³

et al. 2000

Earth and Environmental Science Transactions of the Royal Socie

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Multidisciplinary three-dimensional modelling, involving geophysical, structural and geochemical data, has been used to study the relationships between magmatism, tectonics, fluid circulation and mineralisation in the northern Limousin, and to provide P-T-Z-t paths constrained by the available dating. The ore deposit occurrence displays little spatial relationship with granites emplaced in the 360-320 Ma period, probably because the low global permeability and tectonic regime did not allowed vertical fluid exchanges to be established. In contrast, the change in the tectonic regime induced by the delamination of the lower lithosphere (320-300 Ma), and characterised by the passage to general extension, has played a major metallogenic role. However, the ore deposit processes appear to be specific to each metal. Most of the W-Sn deposits appear to be synchronous with rare metal granites emplacement, atc.310 Ma, that allowed the focus of fluids of different origins towards the apex of plutons. In contrast, for Au and U, the whole mineralisation process covers several tens of-millions of years. It is controlled by the regional tectonic evolution of the Limousin area during the same period, and especially by a rapid exhumation of the ductile crust which occurred in the 310-300 Ma period.

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Section: The Main Types Of Granitoidsmentioning

confidence: 99%

Relationships between granitoids and mineral deposits: three-dimensional modelling of the Variscan Limousin Province (NW French Massif Central)

Veslud¹,

Cuney²,

Royer³

et al. 2000

Earth and Environmental Science Transactions of the Royal Socie

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“…5) may be related to granites. Tantalum and niobium mineralization is mainly associated with albite rich zones in granites (Pollard, 1989). Hafnium is also a common chemical element in granites and diorites as well as Zr (Pollard, 1989).…”

Section: General Characteristics Of Sedimentsmentioning

confidence: 99%

“…Tantalum and niobium mineralization is mainly associated with albite rich zones in granites (Pollard, 1989). Hafnium is also a common chemical element in granites and diorites as well as Zr (Pollard, 1989). The values of Hf/Zr ratio, used to discriminate different types of granites (ranging from 0.025-0.029, mean 0.027), are higher than several types of granites including granite pegmatites (Currie, 1968).…”

Section: General Characteristics Of Sedimentsmentioning

confidence: 99%

Geochemical and Mineralogical Fingerprints of the Sediments Supply and Early Diagenetic Processes in the Bizerte Lagoon (Tunisia)

et al. 2016

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The Bizerte Lagoon (Tunisia) functions as a sedimentation environment characterized by receiving allochthonous sediments mainly transported by the Ben Hassine, Rharek and Guenich streams, as well as marine sediments from the Mediterranean Sea. It is subjected to significant environmental changes due to the natural and anthropic influences altering the natural patterns of circulation, extraction and/or deposition of mineralogical materials. The aim of this investigation is to analyze the sediments supply and early diagenetic processes in Bizerte Lagoon. The physicochemical parameter of the sediment pore water, as well as their texture, mineralogical composition (X-Ray diffraction technique -XRD), magnetic susceptibility and their geochemical composition (namely lithogenic and biogenic chemical elements analyzed by ICP-MS) were analyzed in 10 sampling stations.The water temperature with an average of 15.2°C was stable in the study area. The sediments were generally characterized by fine granulometry, mainly mud and sandy mud, poorly to very poorly sorted, and constituted by two or more granulometric particle modes. The mineralogical results revealed the presence of phyllosilicates, quartz, pyrite, calcite, anatase and K-feldspar, and other minerals in smaller proportions. The fine sediment and high phyllosilicates and Al contents indicate the presence of weak currents in most part of the studied area. The results of sorting, skewness and kurtosis suggest that the currents are more active in the northern region of the lagoon, near the channel of communication with the Mediterranean Sea. They also evidence a coarser particle contribution of the Ben Hassine stream to the lagoon. The other streams seem to introduce mostly fine-grained sediments in the lagoon. The currents Journal of Sedimentary EnvironmentsPublished by Universidade do Estado do Rio de Janeiro 1(4): 432-448, circulation, the water residence time and the biological productivity influence the mineralogical and geochemical characteristics of the bottom sediments. The industrial activity is also an important factor, since it results in the accumulation of high levels of some metals, such as Fe. Metals are mostly retained in the sediment in areas with active biogeochemical activity due to high organic matter accumulation. Mineralogical and geochemical patterns indicate contributions from different rocks sources, diverse processes of transport and deposition of sediments and varied processes of production of autochthonous materials.

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“…Similar zonation has recently been documented in the South Mountain batholith (MacDonald and Home, 1987). However, high-silica magmas responsible for raremetal, volatile-rich granites compositionally similar to the DLC typically are vertically zoned prior to crystallization (Kovalenko and Kovalenko, 1984;Tuach and others, 1986;Hildebrand, 1986;Pollard, 1989). Proposed mechanisms that account for such zoning include thermal gravitational diffusion (Hildreth, 1981, convective diffusion (Irvine, 1979, convective fractionation (Rice, 1981;Sparks and others, 1984) and sidewall crystallization (Baker and McBirney, 1985).…”

Section: Magmatic Evolution Of the Dlcmentioning

confidence: 99%

Genesis and fluid evolution of the East Kemptville greisen-hosted tin mine, southwestern Nova Scotia, Canada

Richardson

Bell

Watkinson

et al. 1990

Geological Society of America Special Papers

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The East Kemptville greisen-hosted tin deposit (58 million tonnes of 0.165 percent Sn), southwestern Nova Scotia, Canada, occurs beneath undulations in the contact between granitic rocks of the Davis Lake complex (DLC) and Meguma Group metawacke. Cassiterite-topaz ore precipitated from a F-and Sn-rich fluid derived from the East Kemptville leucomonzogranite. Controls on tin mineralization include the unusual primary Sn and F abundances of the DLC magma, the vertical chemical zonation of the magma prior to crystallization, generation of an aqueous phase, and associated Sn-CI complexing before the separation of F from the magma and the flat-lying granitemetawacke contact.The Carboniferous DLC is composed of biotite-bearing monzogranites, leucomonzogranite, and high-F, low-B topaz greisen. The chemical and isotopic signatures of the monzogranites reflect the unusual source of this highly evolved pluton. Magmatic evolution was focused toward the granite-metawacke contact and culminated, at the current erosional level, in the East Kemptville deposit. Chemical variation is attributed to the vertical zonation of the magma prior to the fractionation of biotite, K-feldspar, ilmenite, and REE-bearing phosphate minerals. The remarkably high F and P contents resulted in unusual A1 and P distributions and concentration of metals beneath the contact as a result of increased magmatic depolymerization and diffusion.Pegmatitic segregations record the evolution of a F-and Sn-rich aqueous fluid. This aqueous phase scavenged CI, alkali elements, P, Sn, and other metals from the magma, concentrating them beneath the contact. In contrast to porphyry-style deposits, this fluid was not expelled from the granite. When crystallization was complete, more than 10,000 tonnes of F partitioned into this aqueous fluid, forming a hydrofluoric fluid that was neutralized by reaction with the leucomonzogranite. Quartz-topaz rock is either a direct precipitate from the F-rich fluid or extensively replaced leucomonzogranite. Quartz-mica greisen and incomplete greisen formed as the F/OH ratio in the fluid decreased. Veins and fractures emanating from massive greisen zones have alteration envelopes, indicating these structures were conduits for the F-rich fluid. Their orthogonal orientation suggests these veins are related to cooling, not hydraulic fracturing.Whole-rock Rb-Sr isotopic data from leucomonzogranite and quartz-topaz rocks yield dates and initial ratios statistically identical to the biotite monzogranite. High mean square of weighted deviations (MSWDs) resulting from the former data reflect contami-*Present address: , 1990, Genesis and fluid evolution of the East Kemptville greisen-hosted tin mine, southwestern Nova Scotia, Canada, in Stein, H. J., and Hannah, J. L., eds., Ore-bearing granite systems; Pedogenesis and mineralizing processes: Geological Society of America Special Paper 246. J. M. Richardson and Othersnation of the late-magmatic fluids by Sr derived from the metawacke and later thermal overprinting. Deformation, probably relat...

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Geochemistry of Granites Associated with Tantalum and Niobium Mineralization

Cited by 24 publications

References 35 publications

Relationships between granitoids and mineral deposits: three-dimensional modelling of the Variscan Limousin Province (NW French Massif Central)

Relationships between granitoids and mineral deposits: three-dimensional modelling of the Variscan Limousin Province (NW French Massif Central)

Geochemical and Mineralogical Fingerprints of the Sediments Supply and Early Diagenetic Processes in the Bizerte Lagoon (Tunisia)

Genesis and fluid evolution of the East Kemptville greisen-hosted tin mine, southwestern Nova Scotia, Canada

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