Boron isotope systematics of tourmaline from granites and pegmatites: a synthesis

Jiang, Shao‐Yong; Palmer, Martin R.

doi:10.1127/ejm/10/6/1253

Cited by 105 publications

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“…Both of them suggested that boron isotope fractionation occurs during magmatic degassing and magmatic-hydrothermal evolution, whereby the heavy 11 B is preferentially partitioned into exsolved volatile aqueous fluids, resulting in a relative 10 B enrichment in the residual melt and magmatic tourmalines. This is in good agreement with the boron isotope Clarke et al, 1989;Swihart and Moore, 1989;Chaussidon and Albarède, 1992;Slack et al, 1993;Smith and Yardley, 1996;Jiang and Palmer, 1998;Kasemann et al, 2000;Jiang, 2001). fractionation trend for tourmalines from the quartz-tourmaline orbicules (δ 11 B = -32.1‰ to -37.3‰) and veins (δ 11 B = -21.3 to -28.2‰) at Lavicky.…”

Section: Boron Isotope Geochemistry Of the Lavicky Tourmalinessupporting

confidence: 71%

“…Study of boron isotopes in tourmaline should therefore yield valuable information regarding magma-volatile relationship, magmatic-hydrother- mal evolution, and origin of granitic rocks, particularly for B-rich peraluminous leucogranites and pegmatites. Although chemical compositions of tourmaline from granites and associated hydrothermal systems have been widely reported, boron isotopic studies of tourmaline in these settings are relatively rare (Swihart and Moore, 1989;Chaussidon and Albarède, 1992;Smith and Yardley, 1996;Jiang and Palmer, 1998;Tonarini et al, 1998;Jiang, 2001), and there is no report on boron isotopic compositions of tourmaline from quartz-tourmaline orbicules from leucogranite. In this paper, we present a chemical and boron isotopic study on tourmalines from quartz-tourmaline orbicules in a single magmatic-hydrothermal system-the Lavicky leucogranite in the Czech Republic, which provide important insights into the origin and evolution of the granite as well as the boron isotope fractionation mechanism during magma degassing and magmatic-hydrothermal processes.…”

Section: Introductionmentioning

confidence: 99%

“…3). Although previous studies have shown an overall large δ 11 B variation in tourmaline from granites and pegmatites worldwide (~30‰), only limited δ 11 B variations (<5‰) were found within any individual magmatic body (Swihart and Moore, 1989;Chaussidon and Albarède, 1992;Smith and Yardley, 1996;Jiang and Palmer, 1998;Tonarini et al, 1998). Smith and Yardley (1996) did a detailed investigation of boron isotope fractionation in granites and related W-Sn veins from magmatic to hydrothermal systems in Cornwall, Southwestern England.…”

Section: Boron Isotope Geochemistry Of the Lavicky Tourmalinesmentioning

confidence: 99%

“…Smith and Yardley (1996) did a detailed investigation of boron isotope fractionation in granites and related W-Sn veins from magmatic to hydrothermal systems in Cornwall, Southwestern England. Jiang and Palmer (1998) summarized the boron isotope systematics of tourmaline from granites and pegmatites. Both of them suggested that boron isotope fractionation occurs during magmatic degassing and magmatic-hydrothermal evolution, whereby the heavy 11 B is preferentially partitioned into exsolved volatile aqueous fluids, resulting in a relative 10 B enrichment in the residual melt and magmatic tourmalines.…”

Section: Boron Isotope Geochemistry Of the Lavicky Tourmalinesmentioning

confidence: 99%

“…Studies of these orbicules have sig-maline typically reflects the environment in which it crystallized (e.g., Henry and Guidotti, 1985;Slack, 1996). Previous boron isotope studies have revealed its large fractionation (~80‰ variation in δ 11 B) between the two isotopes of 10 B and 11 B in nature (Palmer and Swihart, 1996;Jiang, 1998;Jiang and Palmer, 1998). As a highly mobile element during magmatic and fluid-related processes, boron tends to be preferentially enriched in late exsolved volatile-rich fluids; and the exsolution of these fluids leads to depletion of boron and other "fluid mobile" elements in granites (London et al, 1996;Dingwell et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Chemical and boron isotopic compositions of tourmaline from the Lavicky leucogranite, Czech Republic

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Abundant tourmaline occurs in the Lavicky leucogranite, Czech Republic as spherical to ovoid quartztourmaline orbicules, typically 5 to 7 cm in diameter. The tourmalines also occur as fine-grained quartztourmaline veins (<1 cm thick) that cut the orbicule-rich granite. Electron microprobe analyses reveal that tourmaline from the quartz-tourmaline orbicules is Fe-rich schorl with a range of Fe/(Fe+Mg) ratio 0.62 to 0.77 and Na/(Na+Ca) ratio 0.82 to 0.95. In contrast, tourmaline from quartz-tourmaline veins is Mg-rich dravite with a range of Fe/(Fe+Mg) ratio 0.23 to 0.45 and Na/(Na+Ca) ratio 0.67 to 0.90. Very low δ 11 B values of -37.3 to -32.1‰ are found in the tourmalines from the orbicules, whereas tourmalines from the veins display relatively higher δ 11 B values of -28.2 to -21.3‰. The overall large δ 11 B variation is suggested to reflect mixing of different boron sources and boron isotope fractionation during magmatic degassing and magmatic-hydrothermal evolution at late solidus to early subsolidus stages of granite crystallization. Only non-marine evaporites show very negative δ 11 B values (<-20‰) in all natural boron reservoirs, hence, the very low δ 11 B values of the quartz-tourmaline orbicules likely indicate a major contribution of boron from non-marine evaporites that probably exist in the magma source regions or assimilated into the magma during its ascent. Quartz-tourmaline orbicules may have formed during a transition from magmatic to hydrothermal processes, whereas the vein tourmalines formed by mixing of the exsolved magmatic-hydrothermal fluids with an external fluid rich in Ca and Mg and having higher δ 11 B than the exsolved magmatic fluids.

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