Concentrations Of Tourmaline Research Articles

In-situ boron isotope and chemical composition of tourmaline in the Gyirong pegmatite, southern Tibet: Implications for petrogenesis and magma source

Leucogranitic rocks, mainly including leucogranite-pegmatite systems, have been found to be widely distributed in the South Tibetan Himalaya, and they have received considerable interest because of their significance in crustal evolution and associated rare-metal mineralization. Although the nature and geodynamic setting of the Himalayan leucogranites have been well documented by numerous studies, the pegmatites spatially associated with these leucogranites are still poorly understood. Tourmaline is a ubiquitous phase from the leucogranite to the pegmatite. We have therefore conducted in situ major and trace element and boron isotope investigations of tourmaline from the Gyirong pegmatite, synthesizing published data on the Gyirong leucogranite, to document the origin of tourmaline and its genetic implications. Two types of tourmaline (Tur-Ⅰ & Tur-Ⅱ) have been identified in this contribution and they are enriched in Fe, Si and Al but depleted in Mg and Ca, with Mg/(Mg+Fe) ratios ranging from 0.22 to 0.45. Accordingly, the tourmalines belong to the alkali group and have schorl composition. Trace elements, such as Zn, Ga, V, Sc, Li, Sn, Sr, and Co in the tourmalines are relatively enriched, whereas, other trace elements record low concentrations less than 10 ppm. The trace element concentrations of tourmaline are mainly controlled by melt composition. Morphological and geochemical characteristics reflect that the tourmalines from the Gyirong pegmatite are magmatic in origin. The Gyirong pegmatitic tourmalines have S-type granitoids and pegmatites boron isotopic signatures with a tight range of δ11B values between −11.8 and −9.7‰, which is consistent with the magmatic tourmalines (Mg-poor) of the Gyirong leucogranite. This study suggests that the Gyirong pegmatite was the product of crustal anatexis and that the crustal metapelitic rocks within the Greater Himalayan Crystalline Complex were the most likely source components.

Tin Enrichment in Magmatic-Hydrothermal Environments Associated with Cassiterite Mineralization at Ardlethan, Eastern Australia: Insights from Rb-Sr and Sm-Nd Isotope Compositions in Tourmaline

Abstract Primary cassiterite mineralization is often associated with highly evolved granites, but the magmatic and hydrothermal processes that produce these deposits are often difficult to decipher. In this study, we employed the chemical and Sr-Nd isotope compositions of tourmaline to monitor processes of Sn enrichment in the magmatic and hydrothermal stages of the Ardlethan granite (Australia) and its associated Sn deposits. Initial 87Sr/86Sr (0.710–0.717) and ɛNd (–5.0 to −1.0) values of late magmatic tourmalines indicate derivation of the Ardlethan granite via an assimilation-fractional crystallization (AFC) process in which incorporation of Ordovician sediment into an I-type granitic parental magma produced an enrichment of Sn at least 30 times over that of the assumed mafic-dominated igneous source of the granite. The rare earth element and Sn concentrations of tourmaline in the greisen deposits together with δ18O of coprecipitated quartz indicate that exsolution of a late-stage, Cl-rich fluid from the Ardlethan granite led to cassiterite mineralization in these deposits. In contrast the Fe/(Fe + Mg) and initial εNd (–9.2 to −12.9) compositions of tourmaline that coprecipitated with cassiterite in the large breccia pipes adjacent to the Ardlethan granite suggest that granite-derived fluids scavenged Sn by chemical leaching of an older S-type granite that hosts the pipes. This study shows that tourmaline can act as a robust monitor of key geologic processes in complex and dynamic magmatic-hydrothermal Sn systems and that its 87Sr/86Sr and ɛNd isotope compositions are especially useful for constraining the nature of magmatic and hydrothermal sources that contributed to these deposits.

Inherited Eocene magmatic tourmaline captured by the Miocene Himalayan leucogranites

Abstract The Miocene Cuonadong leucogranites in the easternmost section of the Tethyan Himalaya, Southern Tibet, are characterized by two types of tourmaline. Tourmaline occurs as needle-like crystals in the two-mica ± tourmaline granites (Tur G) and large patches in the pegmatites (Tur P). Both the granite and the pegmatites yield Miocene ages (ca. 20 Ma) based on monazite U(-Th)-Pb dating, whereas 40Ar/39Ar geochronology of the coarse-grained tourmalines (Tur P) crosscut by pegmatite veins yielded an Eocene mini-plateau age of 43 ± 6 Ma. Major element concentrations of tourmaline indicate that both Tur P and Tur G belong to the schorl group with a magmatic origin, but trace elements such as V indicate that they are not cogenetic. Boron isotopes suggest that Tur P (average –9.76‰) was derived from typical crustal sources, whereas Tur G (average –7.65‰) contains relatively more mafic input. The capture of Eocene tourmaline by the Miocene leucogranites at Cuonadong suggests that the crustally derived Eocene magmatism may have occurred in the southern Tethyan Himalaya. Identification of the inherited magmatic tourmaline (Tur P), although not common, challenges the current application of tourmaline chemistry to the investigation of magmatic-hydrothermal systems.

Elemental substitutions and compositional evolution during tourmaline formation in metasomatic schistose rocks of Sikait area in the Southern Eastern Desert, Egypt

Tourmaline deposit in Sikait area (Southern Eastern Desert of Egypt [SEDE]) is closely associated with metapelitic schistose rocks that belong to Neoproterozoic time. The distribution of tourmaline was mostly controlled by Nugrus shearing, along with schist leucocratic rock varieties (leucogranite, pegmatite, and aplite dikes), which are syntectonically dissected by hydrothermal quartz veins. Local concentrations of tourmaline occur either as discontinuous tourmalinite bands/pockets or as disseminated isolated clusters of crystals within the metapelitic schistose rocks, pegmatites, and quartz veins. Chemical and mineralogical changes accompanying with tourmaline formation have been observed within the schistose rocks in contact with a pegmatitic bodies in Sikait area. Four mineral assemblages were identified on approaching to the pegmatite contact: (1) Quartz-Biotite-Potassium Feldspar-Chlorite assemblage (Q-B-K-C); (2) Quartz-Biotite-Tourmaline-Chlorite assemblage (Q-B-T-C); (3) Tourmaline-Quartz-Muscovite assemblage (T-Q-M); and (4) Tourmaline-Quartz assemblage (T-Q). Toward the pegmatite contact, K, Li, Rb, SiO2, CaO, MgO, Sr, and Ba are decreased, while Al2O3, B2O3, Na2O, Fe (tot), Zr, Y, and Th are moderately increased. Variations in the mineral assemblages and whole-rock chemistry within the four alteration zones appear to be controlled by boron metasomatism and potash leaching. The normalized rare earth element patterns of rock samples from the four alteration zones suggest a partial alteration of the original sedimentary patterns by the metasomatic-magmatic fluids. The alteration could be either a single phase of interactions between pegmatite fluid and schists with B-, Li-, Rb-carrying fluid or a couple of phases (B-, Mn-, Be-rich fluid and Rb-, Li-, K-rich fluid). In all cases, boron from the pegmatite-associated fluids reacts with the surrounding schistose rocks to breakdown of sheet silicate which acts as “traps” for Rb, Sr, Li, Ba, and K and hence leads to tourmaline-rich assemblages.

Effects of Tourmaline Concentration on Natural Rubber Foam

Natural rubber foam/tourmaline composite was prepared from natural rubber latex and vulcanized by sulfur curing system. Tourmaline powder was dispersed in potassium oleate before foaming production. The batch foaming production was used in this research. In order to investigate the effects of tourmaline concentration in natural rubber foam, mechanical properties, microstructure, and thermal skin temperature analysis were performed. Increasing of tourmaline concentration affected on high density and small microstructure of natural rubber foam, and the increasing of skin temperature. EDS result confirmed the good distribution of tourmaline powder in natural foam.

Design and manufacturing of warp-knitted filterable fabric with PET/PVDF fiber

In this paper, the filtering effect on fine particle of warp-knitted mesh fabrics was investigated. Polyester yarn (PET) and polyvinylidene fluoride (PVDF) fiber were used as materials to knit the fabrics with five different structures on KS4 tricot warp-knitted machine. After knitting, the fabrics were treated with tourmaline liquid with five different concentrations of tourmaline. Then, the filtration efficiency of samples was tested by the comprehensive test machine. By comparing the filtration efficiency of samples with different concentrations of tourmaline and different structures, the optimal process parameters were obtained that the concentration of tourmaline liquid was 30% and the structure of fabric was one by two insertion. The experimental data of the comprehensive test also revealed that the application of the PVDF and tourmaline did have effects on the promotion of the filtration performance of the warp-knitted fabrics.

Manufacture and filtration of the PM2.0 of microfiber warp-knitted mesh fabrics dealing with tourmaline

Tourmaline can enhance filtering efficiency to PM2.0 of microfiber warp-knitted mesh fabric. In this paper, microfiber warp-knitted mesh fabrics were designed with different mesh structures and mass fraction of tourmaline solution respectively. The effect of tourmaline concentration on filtering efficiency of fabrics was investigated. After the tourmaline solution, the strength of mesh fabrics and durability of tourmaline’s conglutination to the mesh fabrics were explored at the same time. The results shown that the filtering efficiency of microfiber warp-knitted mesh fabrics dealing with tourmaline was resentful. Breaking strength of fabrics decreases with increasing mass fraction of tourmaline solution. The resistant efficiency of fabrics and tourmaline adhesive on the mesh fabrics were still stable along with the increasing mass fraction of tourmaline.

Episodic tourmaline growth and re-equilibration in mica pegmatite from the Bihar Mica Belt, India: major- and trace-element variations under pegmatitic and hydrothermal conditions

AbstractMica pegmatites from the Bihar Mica Belt contain three distinct generations of tourmaline. The major-element composition, substitution vectors and trajectories within each group are different, which indicates that the three types of tourmalines are not a part of one evolutionary series. Rather, the differences in their chemistries as well their mutual microtextural relations, can be best explained by growth of tourmaline from pegmatitic melts followed by episodic re-equilibration during discrete geological events. The euhedral, coarse-grained brown type I tourmaline cores have relatively high Ca, Mg (XMgc. 0.37) and Al with correlated variation in Sr, Sc, Ti, Zr, Y, Cr, Pb and Rare Earth elements (REEs). They are inferred to have crystallized from pegmatitic melts. Monazites included within these tourmalines give chemical ages of 1290−1242 Ma interpreted to date the crystallization of the pegmatitic tourmaline. The bluish type II and greyish type III tourmalines with low Ca and Mg contents (XMg = 0.16−0.27) and high Zn, Sn, Nb, Ta and Na, formed by pseudomorphic partial replacement of the pegmatitic tourmaline via fluid-mediated coupled dissolution–reprecipitation, are ascribed to a hydrothermal origin. The ages obtained from monazites included in these tourmalines indicate two alteration events at c. 1100 Ma and c. 950 Ma. The correlated variation of Ca, Mg and Fe and the trace elements Sr, Sn, Sc, Zn and REE within the tourmalines indicates that the trace-element concentrations of tourmaline are controlled not only by the fluid chemistry but also by coupled substitutions with major-element ions.

Catalytic oxidative degradation of bisphenol A using an ultrasonic-assisted tourmaline-based system: Influence factors and mechanism study

Abstract Tourmaline was utilized as a heterogeneous catalyst for the oxidation of bisphenol A (BPA) with synergetic H 2 O 2 -catalytic ability and ultrasonic irradiation. Higher tourmaline concentration, an appropriate H 2 O 2 dose and a lower pH favored BPA depletion. The removal of 5.0 mg L −1 BPA reached 98.4% at 120 min under the following optimized reaction conditions: sonication (40 kHz, 500 W), tourmaline concentration 5.0 g L −1 , H 2 O 2 50 mM and pH 2.0. This high BPA removal could be caused by coordinating heterogeneous and homogeneous processes, based on the observed iron leaching and H 2 O 2 conversion data at different pHs. A retarded first-order kinetic model was employed to describe BPA degradation. The strong inhibition of BPA removal by radical scavengers indicated that the attack of hydroxyl radicals was mainly responsible for BPA removal. In view of the X-ray photoelectron spectroscopy (XPS) results during the reaction, a possible mechanism involving accelerated transfer in the Fe(III)/Fe(II) cycle on the tourmaline surface was proposed. Moreover, eight intermediates were evidenced by GC–MS and LC–MS/MS analyses, and a reaction pathway was also proposed, including the processes of hydroxylation, oxidative skeletal rearrangement, demethylation and dehydration.

Inactivation of bacteria in batch suspension by fluidized ceramic tourmaline nanoparticles under oscillating radio frequency electric fields

Here, we investigated the synergistic effect of fluidized ceramic tourmaline nanoparticles (NPs) with oscillating electric fields to the inactivation of Escherichia coli in batch suspension. Different amounts of tourmaline NPs (5–100mg) were dispersed in bacterial suspension (50ml) and oscillating radio frequency (RF) electric field was applied at 3V (equivalent of 1.5V/cm electric field strength) and at varying frequencies (100kHz and 1MHz). The results showed high inactivation efficiency when combining fluidized tourmaline NPs and oscillating electric fields as compared to individual treatments of electric fields or tourmaline NPs only. The results showed 2.5–5-log reduction of viable E. coli concentration depending on the tourmaline concentration, electric field frequency and solution temperature. The present method shows a lot of promise as a novel and low-cost bacterial inactivation technique for water treatment applications.

Effects of tourmaline on growth of three kinds of microorganisms

Tourmaline is a kind of widespread minerals and has been used in many fields of society. Owing to the special electric properties, tourmaline can destroy the hydrogen bond between water molecules. The growth of microorganism may be affected with addition of tourmaline; therefore the effects of tourmaline on three different kinds of microorganisms were studied using microcalorimetric method. The kinetic parameters of growth process were obtained through the thermogenic curves. The results show that high concentration tourmaline inhibited the growth of prokaryotic cells (the growth rate constant of Escherichia coli and Staphylococcus aureus decreased 68.77 and 35.25% at tourmaline concentration of 160 g/L), while promoted eukaryotic cell (the growth rate constant of Candida albicans increased 40.73% at tourmaline concentration of 160 g/L). However, the low concentration tourmaline had complex effects on growth of the studied microorganisms. Key words: Microcalorimetric, water cluster, growth rate, inhibitory ratio.

Boron isotope composition of tourmalinite and vein tourmalines associated with gold mineralization, Serra do Itaberaba Group, central Ribeira Belt, SE Brazil

Important concentrations of tourmaline occur as gold-bearing stratiform tourmalinites and in mineralized quartz–tourmaline veins at the Tapera Grande and Quartzito gold prospects in the Mesoproterozoic Serra do Itaberaba Group, central Ribeira Belt (São Paulo State, SE Brazil). The main rock types in both prospects constitute the volcanic–sedimentary Morro da Pedra Preta Formation, which formed in a submarine back-arc setting. At Tapera Grande, the volcanic–sedimentary sequence is composed of metabasic and metavolcaniclastic rocks, graphitic and sulfur-rich metapelites, banded iron formation, metandesite, metarhyolite, calc-silicates, tourmalinites and metahydrothermalites derived from mafic and felsic rocks. The Mesoproterozoic rocks at Quartzito prospect are lithologically similar but they have been affected by Neoproterozoic faulting and shearing and by the emplacement of granitic rocks, resulting in the formation of tourmaline-rich quartz–carbonate veins with gold and base metal mineralization. We conducted a chemical and B-isotope study of tourmalines in order to better understand the origin of the stratiform tourmalinites in the Morro da Pedra Preta Formation and their relationship with gold mineralization. The overall range of δ 11B values obtained for the tourmalinite and vein tourmalines is between − 15‰ and − 5‰, with the tourmalinites falling at the low end of this range (− 15 to − 8‰). Such values are typical for continental crust and inconsistent with a primary marine boron signature as expected from the submarine-exhalative model for the gold prospects. We conclude from this that tourmaline formed or recrystallized from crustal fluids related to the amphibolite-grade metamorphism which affected the Serra do Itaberaba Group and that gold deposition occurred syn- to post-peak metamorphism by phase immiscibility, as attested by fluid inclusions in Tapera Grande tourmalinite tourmaline and quartz. The vein-hosted tourmalines at Quartzito have isotopically variable boron signatures, with heavier δ 11B values of − 5‰ to − 8‰ for acicular green tourmalines and lighter values (− 15‰ to − 7‰ for light blue, Ti-free tourmaline from quartz–carbonate veins). We attribute the heavier boron to fluids derived from the volcano-sedimentary rocks of marine affinity whereas the lighter boron was contributed by crustal fluids related to the granitoids or metasediments in the continental crust.

Provenance of the Lower Paleozoic Balcarce Formation (Tandilia System, Buenos Aires Province, Argentina): Implications for paleogeographic reconstructions of SW Gondwana

Lower Paleozoic moderately sorted quartz–arenites from the Balcarce Formation deposited in eastern Argentina (Tandilia System) comprise mainly detrital material derived from old upper crustal material. The sources were magmatic, sedimentary, and subordinated felsic metamorphic terranes. High concentrations of tourmaline and Ti-rich heavy minerals, including zircon and nearly euhedral chromite, are common. Trace element concentrations (Nb, Cr) on rutile indicate pelitic and metabasaltic sources, respectively. Major element analyses on chromites indicate a basic volcanic protolith of mid-oceanic ridge origin, which was exposed close to the depositional basin. The delivery of chromite may be associated with convergent tectonics causing the consumption and obduction of oceanic crust during pre-Upper Ordovician times. The oblique/orthogonal collision of the Precordillera Terrane with the western border of the Rio de la Plata Craton, west of the Balcarce Basin or source further to the east from a Lower Palaeozoic extensional basin are possibilities. Geochemical and petrographic data exclude the underlying Precambrian and Cambrian sedimentary rocks as dominant sources, and favour the basement of the Río de La Plata Craton, including Cambrian rift-related granites of South Africa and the Sierras Australes (eastern Argentina), as main suppliers of detritus. Trace element geochemistry of recycled pyroclastic material, associated with the quartz–arenites, also suggests volcanic arc sources. The provenance of the pyroclastic material may either be the Puna–Famatina arc, located in north and central Argentina, or a hypothetical active margin further to the south. These ash layers are equivalent in age to volcanic zircons found in the Devonian Bokkeveld Group in western South Africa. The deposition of a glacial diamictite of Hirnantian age (Sierra del Volcán Diamictite) is interpreted as a member of the Balcarce Formation. Based on the stratigraphic re-location of the glacial diamictite and trace fossils, the Balcarce Formation is considered here to be Ordovician to Silurian in age. The Balcarce Formation can be correlated with similar rocks in South Africa, the Peninsula Formation, and the upper Table Mountain Group (Windhoek and Nardouw subgroups), including the Hirnantian glacial deposit of the Pakhuis Formation.

Decomposition of 2-chlorophenol using a tourmaline–photocatalytic system

10.0 wt.% tourmaline mineral was loaded onto amorphous TiO 2 and treated at 100–900 °C to obtain anatase and rutile structures, respectively, and were used for the photodecomposition of 2-chlorophenol. Tourmaline (10.0 wt.%)/TiO 2 (anatase) and pure TiO 2 (anatase) adsorbed 2-chlorophenol at 15 ppm and 8 ppm, respectively. 2-Chlorophenol was completely decomposed after 42 h in 10.0 wt.% tourmaline/TiO 2 (anatase), by a first-order rate equation. The decomposition rate increased with increasing catalyst amount and tourmaline concentration to give optimal conditions of 1.0 g/L and 12.5 wt.%, respectively. The decomposition of 2-chlorophenol was also affected by H 2O 2 addition and pH regulation. The decomposition rate reached 40.0 ppm/h when 10.0 mL/L of H 2O 2 was added to the feed solution, and 100 ppm of 2-chlorophenol was completely removed after 21 h at pH 11.0.

Modeling of an external light irradiation slurry photoreactor: UV light or sunlight-photoassisted Fenton discoloration of azo-dye Orange II with natural mineral tourmaline powder

A model for design and scale-up of an external light irradiation slurry photoreactor was developed on the basis of a model for the average light intensity in the photoreactor. In order to assess the design parameters in the proposed model, experiments for UV light or sunlight-photoassisted Fenton discoloration of azo-dye Orange II in water with iron ion eluted from the natural mineral tourmaline powder containing 4.49 wt% Fe 2O 3 were conducted using an external light irradiation cylindrical column photoreactor. The efficiency of discoloration increased as initial Orange II concentration decreased and the tourmaline concentration and UV light intensity increased. It was found that the optimal hydrogen peroxide concentration and pH are 500 mg L - 1 and 3, respectively. The proposed model, in which the change of light intensity with degradation time due to the discoloration of Orange II and the light scatter due to solid photocatalysts are taken into account, could simulate the experimental results both for UV light and sunlight irradiation conditions reasonably well. The model is applicable commonly both for UV light and sunlight irradiation. The results will be very useful for designing slurry photoreactors in the treatment of textile effluents.

Origin of tourmaline in the metamorphosed Sikait pelitic belt, south Eastern Desert, Egypt

A Neoproterozoic metapelitic schist belt at the Sikait area of the south Eastern Desert is a favourable environment for localisation of tourmaline mineralisation in the Pan-African Belt in Egypt. Local concentrations of tourmaline in the Sikait area are closely associated with stratiform metapelitic schists. They are confined to the Nugrus shear zone, along which various leucocratic rocks (leucogranite, pegmatite, aplite) are syntectonically emplaced with various stages of hydrothermal quartz veins. Tourmaline occurs either as disseminated isolated clusters of crystals or as discontinuous tourmalinite bands within the metapelitic rocks, pegmatites and quartz veins. Four types of tourmaline-rich rocks were distinguished: (i) fine-grained tourmaline-rich rocks, which are associated with the biotite schist along contacts with gneissose granites (TR1); (ii) tourmaline-rich rocks, associated with the metapelitic and amphibolitic closely to Nugrus thrust zones (TR2); (iii) tourmaline-rich rocks, associated with the pelitic hornfels at the contact between metapelitic schist and leucogranite (TR3); and (iv) tourmaline-rich rocks and quartz veins, associated with chlorite-graphite schist in contact aureoles with leucogranite and pegmatite veins (TR4). Microprobe analyses revealed that tourmalines are Al saturated for the given Fe/Mg alkali-deficient group tourmaline with minor X-site vacancy and substitution of Ca for Na. Tourmalines belong to the schorl-dravite solid solution series and have a wide compositional range, from nearly end member dravite for TR3 tourmalines to schorl for TR4 tourmalines; TR1 and TR2 tourmalines have intermediate compositions. The Fe/(Fe + Mg) varies between 0.02 and 0.89. Variation in composition of Al-rich tourmalines is essentially caused by variations in Mg, Fe, Na, Ca and Ti. The whole rock chemical analyses of tourmaline-rich rocks closely resemble the trends observed for metapelitic schist and leucocratic rock and reflect mixing between phyllosilicate-rich and quartz-rich end members, which indicates that tourmaline-rich rocks do not contain a significant detrital component. Chondrite-normalised patterns of rare earth elements (REE) in tourmaline-rich rocks and quartz-rich tourmalines are similar to those of the surrounding unaltered metapelitic schists and leucocratic rocks, respectively. Minor depletions of LREE and local negative Ce anomalies characterise the chondrite-normalised REE pattern of TR1 tourmaline-rich rocks, suggesting its formation in the presence of seawater-derived fluids. However, TR4 types are characterised by low content ΣREE, such as that of leucocratic rocks. Thus, the geochemical data imply relative immobility of Al, Ti, Cr and HREE during hydrothermal alteration and later metamorphism. The different tourmaline varieties and their respective compositions are interpreted in terms of multistage evolution. Formation of the TR1 tourmaline-rich rocks probably was the net result of several processes, including direct precipitation from B-rich hydrothermal fluids or colloids, early diagenetic reactions of biotite-pelitic sediments with these fluids and subsequent recrystallisation during late regional deformation and metamorphism to give TR2 tourmaline-rich rocks. The TR3 tourmaline-rich rocks mainly developed by the thermal metamorphic recrystallisation of TR1. Tourmaline-rich rocks and veins adjacent to leucogranite and pegmatite veins (TR4) are the result of B-metasomatism; the primary B having been recycled from tourmalinites during regional metamorphism and magmatism.

Significance of tourmaline-rich rocks in the North Range Group of the Cuyuna Iron Range, east-central Minnesota

Concentrations of tourmaline in Early Proterozoic metasedimentary rocks of the Cuyuna iron range, east-central Minnesota, provide a basis for redefinition of the evolutionary history of the area. Manganiferous iron ore forms beds within the Early Proterozoic Trommald Formation, between thick-bedded granular iron-formation having shallow-water alepositional attributes and thin-bedded, nongranular iron-formation having deeper water attributes. These manganese-rich units were previously assumed to be sedimentary in origin. However, a reevaluation of drill core and mine samples from the Cuyuna North range has identified strata-bound tourmaline and tourmalinite, which has led to a rethinking of genetic models for the geology of the North range. We interpret the tourmaline-rich rocks of the area to be a product of submarine-hydrothermal solutions flowing along and beneath the sediment-seawater interface. This model for the depositional environment of the tourmaline is supported by previously reported mineral assemblages within the Trommald Formation that comprise aegirine; barium feldspar; manganese silicates, carbonates, and oxides; and Sr-rich barite veins.In many places, tourmaline-rich metasedimentary rocks and tourmalinites are associated locally with strata-bound sulfide deposits. At those localities, the tourmaline-rich strata are thought to be lateral equivalents of exhalative sulfide zones or genetically related subsea-floor replacements. On the basis of the occurrence of the tourmaline-rich rocks and tourmalinites, and on the associated minerals, we suggest that there is a previously unrecognized potential for sediment-hosted sulfide deposits in the Cuyuna North range.

Chemical variation and significance of tourmaline from Southwest England

Tourmaline is a common and locally abundant mineral in all products of the granite magmatism and associated hydrothermal activity in southwest England, particularly in the county of Cornwall. Tourmaline of magmatic origin is homogeneous and is marked by high Fe/Mg, high F, and high Al in the place of divalent cations (R2 site). The substitution of Al for divalent cations such as Mg and Fe (super 2+) is charge-compensated by a deficit of alkalies and protons in other structural sites. Tourmaline compositions from the granites clearly reflect the sequence of increased differentiation among the magma types, with biotite granites as the least evolved, and topaz granites as the most evolved. In contrast, tourmaline of hydrothermal origin within granites displays fine-scale compositional zonation with a general tendency toward more magnesian compositions nearer the schorl-dravite solid solution (i.e., little or no Al in the R2 site). Metasomatic tourmaline precipitated in the surrounding pelitic and mafic rocks also possesses fine-scale zonation, and generally reflects the compositions of the host rocks. In addition, tourmaline formed in the country rocks has a higher proportion of Fe (super 3+) to Fe (super 2+) , which presumably indicates a higher oxidation state of fluids in the metamorphic rocks than in the granites. This variation may correlate with the mobilization of tin from the granites and its consequent deposition as cassiterite in the host rocks. The abundance of magmatic tourmaline is limited by the initial Fe-Mg content of the magmas to not more than a few modal or weight percent. Although they contain tourmaline, the biotite granites are not the most likely sources of boron for voluminous, late-stage tourmalinization. Magmas that contained only tourmaline or no Fe-Mg minerals at all, such as the those that formed the topaz granites, may have been sources of large quantities of boron. The most intense areas of tourmalinization do surround the small stocks and sheets of topaz microgranite. High concentrations of tourmaline, for example in hydrothermal veins and breccias, appear to require mixing of two different chemical reservoirs: one a source of boron (the magmas or fluids..

Tourmalinites in the Aphebian Mistassini Group, Quebec

Tourmalinites, or fine-grained sedimentary rocks containing 15–20% or more tourmaline, occur within the Papaskwasati Formation of the Aphebian Mistassini Group in central Quebec. The formation, which is largely composed of fluvial sand-stones and conglomerates with minor argillite beds, was deposited in a restricted embayment close to the transition into marine carbonates. Concentrations of tourmaline are limited to fine-grained sediments and intraclasts, and fine sedimentary structures are preserved within the resulting tourmalinites. This suggests that the tourmalinites formed from preexisting boron-rich muds. It is unlikely that the muds were formed from sea-floor hydrothermal emanations, as no hydrothermal manifestations or spenecontemporaneous vulcanism is known to be associated with this formation. An evaporitic origin for the tourmalinites is consistent with both the sabkha conditions postulated for the origin of nearby carbonates and the limited areal extent of the sedimentary basin.

Tourmaline concentrations in Proterozoic sediments of the southern Cordillera of Canada and their economic significance

Local concentrations of tourmaline occur in the lower Proterozoic (Helikian) Aldridge Formation of southeastern British Columbia, in some places in association with stratiform lead–zinc mineralization as at the Sullivan, Stemwinder, and North Star orebodies. The amount of boron in the rock is as much as two orders of magnitude above average levels reported for the Aldridge Formation or other similar types of sedimentary rocks. The concentrations are not detrital, but are caused by an anomalously high boron level, in a local area, at the time of sedimentation. The appearance of tourmaline within rip-up clasts, and in laminae within pebbles, is evidence of syngenetic introduction of boron.Three populations of tourmalines, on the basis of composition as determined by microprobe analyses, are described from the area:(1) A Proterozoic stock intruding the Aldridge Formation contains abundant schorl.(2) A tourmaline intermediate in composition between dravite and schorl is typical of Aldridge metasediments. Texturally this type occurs as (a) fine felted aggregates in the footwall of the Sullivan orebody, (b) disseminated through waste beds, and (c) in local concentrations removed from the Sullivan orebody.(3) Coarse-grained recrystallized tourmaline associated with the Sullivan ore is magnesium-rich. Recrystallization is erratic, and is probably related to uneven heat flow during metamorphism and to differences in bulk composition.The economic importance of tourmaline concentrations in the Aldridge Formation is their association in both space and time with stratiform sulfides.