Boron In Tourmaline Research Articles

Raman spectroscopic quantification of tetrahedral boron in synthetic aluminum-rich tourmaline

Abstract The Raman spectra of five [4]B-bearing tourmalines of different composition synthesized at 700 °C/4.0 GPa (including first-time synthesis of Na-Li-[4]B-tourmaline, Ca-Li-[4]B-tourmaline, and Ca-bearing ☐-[4]B-tourmaline) reveal a strong correlation between the tetrahedral boron content and the summed relative intensity of all OH-stretching bands between 3300–3430 cm–1. The band shift to low wavenumbers is explained by strong O3-H···O5 hydrogen bridge bonding. Applying the regression equation to natural [4]B-bearing tourmaline from the Koralpe (Austria) reproduces the EMPA-derived value perfectly [EMPA: 0.67(12) [4]B pfu vs. Raman: 0.66(13) [4]B pfu]. This demonstrates that Raman spectroscopy provides a fast and easy-to-use tool for the quantification of tetrahedral boron in tourma-line. The knowledge of the amount of tetrahedral boron in tourmaline has important implications for the better understanding and modeling of B-isotope fractionation between tourmaline and fluid/melt, widely used as a tracer of mass transfer processes.

Tourmaline boron and strontium isotope systematics reveal magmatic fluid pulses and external fluid influx in a giant iron oxide-apatite (IOA) deposit

Tourmaline is a common boron-bearing mineral in hydrothermal system and has been widely used as a mineral probe to reconstruct geological processes because of its broad range in composition and resistance to metasomatic alteration. The origin of Kiruna-type iron oxide-apatite (IOA) deposits, commonly linked to andesitic subvolcanic or volcanic rocks, is highly controversial. Constraints on the evolution of these mineralizing systems are needed to advance understanding of the ore-forming process. In this study, we apply in situ elemental and combined B-Sr isotopic analyses of tourmaline to elucidate the nature and evolution of the subsurface hydrothermal system associated with IOA mineralization in the giant Taocun deposit, eastern China. Taocun is hosted at the top of a diorite intrusion and exhibits three stages of hydrothermal alteration that contain tourmaline: pre-ore Na alteration (Tur I), syn-ore magnetite formation and associated Ca-Fe alteration (Tur II), and post-ore Ca-Mg alteration with sulfide veins (Tur III). Compositional data for each stage of tourmaline plot along the “oxy-dravite”–povondraite join, which is indicative of precipitation from relatively oxidizing fluids. Ranges of Sr-isotopic compositions in Tur I (0.7065–0.7078) and Tur II (0.7068–0.7076) are identical to those of the igneous host rocks, indicating precipitation from magmatic-hydrothermal fluids. The range of B-isotopic compositions in Tur I (δ 11 B values of −6.3‰ to −1.2‰) is also consistent with a magmatic source. Higher δ 11 B values (−2.4‰ to 5.4‰) obtained from Tur II are mainly ascribed to Rayleigh fractionation in the magmatic-hydrothermal system as tourmaline precipitated. Post-ore Tur III has a wide range of mostly lower B-isotopic compositions (−8.5‰ to 0.8‰) that record another pulse of magmatic fluid input. This interpretation is supported by the enrichment of Na, Li, Be, W, Sn, V, and Ti in Tur III, relative to Tur I and II. However, the higher Sr-isotope composition (0.7076–0.7086) of Tur III and available O-isotope composition (−7‰ to 3.5‰) of fluids of this stage record the infiltration of meteoric ground water from adjacent sedimentary country rocks. The results suggest that the Taocun IOA deposit formed in a magmatic-hydrothermal system characterized by two (or more) pulses of magmatic fluid discharge from subvolcanic diorite intrusions, followed by the influx of external ground water as the system waned. This study highlights the utility of tourmaline as a robust geochemical and isotopic monitor of ore-forming processes in such systems.

An experimental approach to quantify the effect of tetrahedral boron in tourmaline on the boron isotope fractionation between tourmaline and fluid

An experimental approach to quantify the effect of tetrahedral boron in tourmaline on the boron isotope fractionation between tourmaline and fluid

The boron isotopic evolution of the Little Three pegmatites, Ramona, CA

Tourmaline, mica, hambergite, danburite, and axinite from three pegmatite dikes (named Main, Swamp, and Spessartine) at the Little Three mine near Ramona, California, have been analyzed by secondary ion mass spectrometry (SIMS) for their boron isotopic compositions (δ11B). Tourmaline is the sole host of B in the massive footwall and hanging wall sections of the dikes, and the principal sink for B in the miarolitic cavities. In the thinner Spessartine and Swamp dikes, the pocket mineralogy includes foitite, spessartine, muscovite, axinite, danburite, and rare beryl. The thicker Main dike culminates in cavities containing topaz, elbaite, lepidolite, boromuscovite, hambergite, and rare stibiotantalite.Values of δ11BTur from the Little Three pegmatites are strikingly heavy (−0.1‰ to +13.8‰) compared to other pegmatitic tourmaline (~−27 to +9‰), which is best explained by inheritance from an 11B-enriched source material such as altered oceanic crust. Flat patterns of δ11BTur from margin-to-core of each pegmatite attest to a negligible fractionation of boron isotopes between tourmaline-granitic melt and granitic melt-aqueous fluid. Tourmaline samples from intermediate zones and miarolitic cavities have identical boron isotopic compositions, except for miarolitic cavities that contain axinite and danburite, whose B is in 4-fold structural coordination. In these cavities, the δ11B of tourmaline increases relative to tourmaline from the intermediate zone.Interpretations of δ11BTur from margin-to-core in these and other pegmatites are hampered by uncertainties in the boron isotopic fractionation factors for melt-aqueous fluid and for tourmaline-granitic melt. Based on modeled cooling and crystallization of these dikes, the growth of tourmaline should have been fast relative to the diffusivity of B through granitic melt. Hence, an equilibrium distribution of 11B and 10B between tourmaline, bulk melt, and an aqueous solution (i.e. Rayleigh fractionation process) is unlikely. The negligible isotopic fractionation of boron in tourmaline from margins to center, therefore, probably records only the bulk isotopic composition of the pegmatite-forming melts.

Fluid sources in the Twangiza–Namoya Gold Belt (Democratic Republic of Congo): Evidence from tourmaline and fluid compositions, and from boron and Rb–Sr isotope systematics

The Twangiza–Namoya Gold Belt (TNGB) developed in a Proterozoic, variably composed sedimentary sequence that is associated with felsic and mafic igneous rocks. During polyphase tectono-metamorphic episodes the basement was exposed to repeated periods of heat influx that mobilised hydrothermal fluids and, at the Meso- to Neoproterozoic boundary, led to the formation of “G4” granites and pegmatites. The evolution of the TNGB hydrothermal system and its associated gold mineralisation are poorly understood. Here we investigate the tourmaline major elemental and the boron isotopic composition from one pegmatite and seven tourmaline-bearing hydrothermal veins sampled from the Kamituga and the Lugushwa gold deposits.Tourmalines from the hydrothermal veins are essentially dravitic with variable Ca contents. In contrast, the pegmatitic tourmaline is schorl–elbaite dominated and largely Ca-free. The boron isotopic signature of hydrothermal tourmaline from the Kamituga deposit (δ11B: −18.4‰ to −15.3‰) is distinctly lighter than that from Lugushwa (δ11B: −13.0‰ to −8.9‰). Pegmatitic tourmaline from Kamituga shows intermediate δ11B values between −14.2‰ and −13.1‰ with an average of −13.9‰. The pegmatitic fluid most likely had a δ11B composition in the range of −12.8‰. The isotopically significantly lighter boron in tourmaline from hydrothermal veins from Kamituga cannot have formed by fractionation from this pegmatitic source.Using the Rb–Sr mineral isochron method we have dated the Kamituga pegmatite as 981±16Ma, which correlates in time with the regional late-Kibaran “G4” granites. Tourmaline-bearing veins from Lugushwa are significantly younger and formed during the early stages of the Pan-African orogenic period (677±17Ma; Rb–Sr mineral data).Fluid inclusions in quartz that are texturally associated with hydrothermal tourmaline contain abundant saline brines and CO2-rich fluids that are commonly associated with CH4 and in places with amorphous carbon and N2. We interpret these fluids as having been derived from the hosting sedimentary sequence. This model is in agreement with the observed tourmaline composition, which are most readily affiliated with a variably Ca- and Al-rich pelitic source. Our model based on the isotopic, age and mineral compositional evidence indicates a sedimentary source of fluids forming the tourmaline-bearing hydrothermal veins in Kamituga and Lugushwa.

Boron-isotope fractionation between tourmaline and fluid: an experimental re-investigation

The fractionation of boron isotopes between synthetic dravitic tourmaline and fluid was determined by hydrothermal experiments between 400 and 700°C at 200 MPa and at 500°C, 500 MPa. Tourmaline was crystallized from an oxide mix in presence of water that contained boron in excess. In one series of experiments, [B]fluid/[B]tour was 9 after the run; in another series it was 0.1. All experiments produced tourmaline as the sole boron-bearing solid, along with traces of quartz and talc. Powder XRD and Rietveld refinements revealed no significant amounts of tetrahedrally coordinated boron in tourmaline. 11B always preferentially fractionated into the fluid. For experiments where [B]fluid/[B]tour was 9, a consistent temperature-dependent boron isotope fractionation curve resulted, approximated by Δ11B(tour–fluid) = −4.20 · [1,000/T (K)] + 3.52; R2 = 0.77, and valid from 400 to 700°C. No pressure dependence was observed. The fractionation (−2.7 ± 0.5‰ at 400°C; and −0.8 ± 0.5‰ at 700°C) is much lower than that previously presented by Palmer et al. (1992). Experiments where [B]fluid/[B]tour was 0.1 showed a significant larger apparent fractionation of up to −4.7‰. In one of these runs, the isotopic composition of handpicked tourmaline crystals of different size varied by 1.3‰. This is interpreted as resulting from fractional crystallization of boron isotopes during tourmaline growth due to the small boron reservoir of the fluid relative to tourmaline, thus indicating larger fractionation than observed at equilibrium. The effect is eliminated or minimized in experiments with very high boron excess in the fluid. We therefore suggest that values given by the above relation represent the true equilibrium fractionations.

Tourmaline B-isotopes fingerprint marine evaporites as the source of high-salinity ore fluids in iron oxide copper-gold deposits, Carajás Mineral Province (Brazil)

Research Article| September 01, 2008 Tourmaline B-isotopes fingerprint marine evaporites as the source of high-salinity ore fluids in iron oxide copper-gold deposits, Carajás Mineral Province (Brazil) Roberto Perez Xavier; Roberto Perez Xavier * 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil *E-mail: xavier@ige.unicamp.br. Search for other works by this author on: GSW Google Scholar Michael Wiedenbeck; Michael Wiedenbeck 22GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Search for other works by this author on: GSW Google Scholar Robert B. Trumbull; Robert B. Trumbull 22GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Search for other works by this author on: GSW Google Scholar Ana M. Dreher; Ana M. Dreher 33Companhia de Pesquisa de Recursos Minerais/Serviço Geológico do Brasil, Av. Pasteur 404, 22290-240 Rio de Janeiro (RJ), Brazil Search for other works by this author on: GSW Google Scholar Lena V.S. Monteiro; Lena V.S. Monteiro 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil Search for other works by this author on: GSW Google Scholar Dieter Rhede; Dieter Rhede 22GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Search for other works by this author on: GSW Google Scholar Carlos E.G. de Araújo; Carlos E.G. de Araújo 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil Search for other works by this author on: GSW Google Scholar Ignacio Torresi Ignacio Torresi 11Departamento de Geologia e Recursos Naturais, Instituto de Geociências, Universidade Estadual de Campinas, 13083-970 Campinas (SP), Brazil Search for other works by this author on: GSW Google Scholar Geology (2008) 36 (9): 743–746. https://doi.org/10.1130/G24841A.1 Article history received: 02 Mar 2008 rev-recd: 16 May 2008 accepted: 10 Jun 2008 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Roberto Perez Xavier, Michael Wiedenbeck, Robert B. Trumbull, Ana M. Dreher, Lena V.S. Monteiro, Dieter Rhede, Carlos E.G. de Araújo, Ignacio Torresi; Tourmaline B-isotopes fingerprint marine evaporites as the source of high-salinity ore fluids in iron oxide copper-gold deposits, Carajás Mineral Province (Brazil). Geology 2008;; 36 (9): 743–746. doi: https://doi.org/10.1130/G24841A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Carajás Mineral Province in northern Brazil contains a variety of world-class (>100 Mt ore) iron oxide copper-gold (IOCG) deposits, including the only Archean examples of this deposit class (e.g., the Igarapé Bahia/Alemão and Salobo deposits). Tourmaline of schorl-dravite composition, a common gangue mineral in these deposits, precipitated shortly prior to and after the ore assemblage. A boron isotope study of texturally different tourmaline from three IOCG deposits (Igarapé Bahia, Salobo, and Sossego) using secondary ion mass spectrometry (SIMS) provides new evidence in the long-standing debate of magmatic versus non-magmatic sources for the high salinity (up to 50 wt% NaCl equiv.) of ore fluids in these deposits. Values of δ11B from 14‰ to 26.5‰ for the Igarapé Bahia and Salobo deposits confirm marine evaporite–derived brines in the ore fluids, whereas lower δ11B values for the Igarapé Bahia deposit (5.8‰ to 8.8‰) suggest that these fluids may have mixed with an isotopically different hydrothermal fluid, or one that had a mixed boron source. More variable and isotopically lighter boron in tourmaline from the Sossego deposit (−8‰ to 11‰) is attributed to mixed sources, including light boron leached from felsic intrusive and volcanic host rocks, and heavy boron derived from marine evaporites. The boron isotope data indicate that the characteristic high salinity of the ore fluids in the Carajás Mineral Province was acquired by the interaction of hydrothermal fluids with marine evaporites. For IOCG deposits that contain tourmaline as a common gangue mineral, boron isotopes offer a valuable tool to constrain the high-salinity source problem, which is a critical issue in metallogenesis of IOCG deposits worldwide. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The spectrophotometric determination of boron in tourmalines

A procedure for the spectrophotometric determination of macro amounts of boron in tourmaline with azomethine H is described. The used tourmaline concentrate was obtained by magnetic separation and heavy-liquids purification of the schorl zone of pegmatite or granite aplite. The samples of tourmaline were decomposed by fusion with anhydrous sodium carbonate and taken up in dilute hydrochloric acid. The interfering effects of iron and aluminium were eliminated by masking with an EDTA - NTA solution. After pH adjustment, the boron was reacted with azomethine H and the absorbance of the obtained coloured complex was measured at 415 nm. The results are compared with those obtained by other procedures. The relative error of the determination was less than 3 %.

Boron determination in tourmaline by neutron induced radiography

The technique of neutron induced radiography has been applied to determine the boron concentration and its spatial distribution in mineral tourmaline collected from Swat Tourmaline Granite, Northern Pakistan. The technique involves the simultaneous irradiation of sample and a standard fixed on a track detector with thermal neutrons and the counting of alpha and 7 Li tracks produced in the detector from the nuclear reaction 10 B( n,α) 7 Li . Boron concentration is determined by comparing the 7 Li and alpha particle tracks density with that of a standard of known boron concentration. Boron concentration in tourmaline has been found to be (3.40±0.01)% in this study which is on the upper side within the normal range (2.5–3.8)% reported in the world. The presence of somewhat higher concentration of boron in tourmaline indicates that the Swat Tourmaline Granite was generated as a late stage hydrothermal activity during the Himalayan Orogeny.

Application of sodium carbonate-zinc oxide decomposition mixture on ICP-AES determination of boron in tourmaline.

Boron in tourmaline, a high refractory mineral with a high boron content (approximately 3%), can be determined after aqueous leaching of a sodium carbonate-zinc oxide melt. Boron is separated effectively from the major elements of matrix, such as silicon, calcium and magnesium and especially from iron, the main spectral interfering element. Measurements were performed by inductively coupled plasma atomic emission spectrometry. A determination limit of 4 microg/g could be achieved when 200 mg of sample are analyzed with a precision of 5.2% RSD. This method could be applied to the determination of fluorine in the same solution.