Tourmalinization in the Dartmoor granite

Brammall, A.; Harwood, H. F.

doi:10.1180/minmag.1925.020.109.02

Cited by 18 publications

(8 citation statements)

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“…It is also noteworthy here that many Sn deposits are associated with quartz-tourmaline orbicule-bearing leucogranites, for example at Cornwall, England (Brammall and Harwood, 1925), Malaysia (Hutchison and Leow, 1963), Yukon Territory (Sinclair and Richardson, 1992), and Tasmania (Taylor, 1979).…”

Section: Disscusions On Possible Primary Boron Sources For the Granitementioning

confidence: 99%

“…However, their origin has been hotly debated. Some earlier workers believed that these orbicules formed by pneumatolysis and autopneumatolysis (Tilley, 1919;Brammall and Harwood, 1925), or by magmatic segregation (Knopf, 1913). Others have suggested a postmagmatic hydrothermal-metasomatic origin (Hutchison and Leow, 1963;Nêmec, 1975).…”

Section: Fig 2 Al-fe(tot)-mg Ternary Diagram In Terms Of Atomic Promentioning

confidence: 99%

“…Occurrences of quartz-tourmaline orbicules in granite have long been recognized worldwide (e.g., Knopf, 1913;Tilley, 1919;Brammall and Harwood, 1925;Hutchison and Leow, 1963;Nêmec, 1975;Sinclair and Richardson, 1992). Overall, these quartz-tourmaline orbicules share similar features such as size, shape, structure, mineralogy, and distribution in the uppermost part of leucogranites.…”

Section: Fig 2 Al-fe(tot)-mg Ternary Diagram In Terms Of Atomic Promentioning

confidence: 99%

“…nificant implications for evolution of magma and volatiles and in fluid-rock interactions, and have long invoked debate regarding their origin (Tilley, 1919;Brammall and Harwood, 1925;Hutchison and Leow, 1963;Nêmec, 1975;Samson and Sinclair, 1992).…”

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

et al. 2003

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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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Section: Disscusions On Possible Primary Boron Sources For the Granitementioning

confidence: 99%

Section: Fig 2 Al-fe(tot)-mg Ternary Diagram In Terms Of Atomic Promentioning

confidence: 99%

Section: Fig 2 Al-fe(tot)-mg Ternary Diagram In Terms Of Atomic Promentioning

confidence: 99%

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

et al. 2003

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“…The west-northwest joint trend compared favorably with Worth's (1930) data, and with Ormerod's (1869) and Gerrard's (1978) data as well. 1 The west-northwest joint trend was noted by Brammall and Harwood (1925) and by Blyth (1962). These published data sets are all much smaller than the ones used in this study.…”

Section: Comparison Of Lineations and Joint Patterns Orientationsmentioning

confidence: 69%

Comparison of Air Photo Lineations and Joint Patterns, Dartmoor, Southwest England

Ehlen¹

1992

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Destroy this report when no longer needed. Do not return it to the originator.The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.The citation in this report of trade names of commercially available products does not constitute official endorsement or approval of the use of such products. 'i thit C lthIt. 04 ,nlomnat~oE. ,., estlmated to 6-k-1qe howr ocf ecOne. n-dAC n I9

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Analysis of spatial relationships among geomorphic, petrographic and structural characteristics of the dartmoor tors

Ehlen

1992

Earth Surf Processes Landf

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The granite tors of Dartmoor are characterized by using the regional spatial patterns of 21 geomorphic, petrographic, and structural variables. The data were derived from topographic maps, field measurement, and laboratory analysis of rock samples collected in the field. Identification of spatial patterns and comparison of patterns between variables were made on contour maps generated from the data using ARC/INFO. Three tor types-summit tors, valleyside tors, and spur tors-are semiquantitatively characterized using these data and procedures.The three types of tors are distinguished with respect to variations in relative relief, joint spacing and joint type, rock texture, grain size, and composition. Summit tors have the highest relative relief (mean: 125.7 m), contain the most potassium feldspar (> 30 per cent), and have the most widely-spaced primary vertical (> 300 cm) and secondary horizontal joints (> 10 cm). The rocks are the most megacrystic

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Tourmalinization in the Dartmoor granite

Cited by 18 publications

References 1 publication

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

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

Comparison of Air Photo Lineations and Joint Patterns, Dartmoor, Southwest England

Analysis of spatial relationships among geomorphic, petrographic and structural characteristics of the dartmoor tors

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