Борные кислоты в процессах пегматитового и гидротермального рудообразования: петрологические следствия открытия сассолина (Н3ВО3) во флюидных включенияхстатья

Статья опубликована в журнале из списка RSCI Web of Science
Статья опубликована в журнале из перечня ВАК
Дата последнего поиска статьи во внешних источниках: 29 ноября 2013 г.

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[1] Борные кислоты в процессах пегматитового и гидротермального рудообразования: петрологические следствия открытия сассолина (Н3ВО3) во флюидных включениях / И. С. Перетяжко, В. Ю. Прокофьев, В. Е. Загорский, С. З. Смирнов // Петрология. — 2000. — № 3. — С. 241–266. Inclusions of boric acid solutions with daughter sassolite crystals were found for the first time in a number of minerals from miarolitic pegmatites of 11 world regions: four localities in central and eastern Transbaikalia, the middle Urals, the central and southwestern Pamirs, Afghanistan, Pakistan, Nepal, California, Elba and Madagascar islands. Experimental data on the properties of aqueous boric acid solutions were summarized and a method was proposed to calculate the concentration of boric acid from the temperature of sassolite dissolution. The peculiar properties of inclusions with berate-bearing solutions were described for the first time. They stem from the polymerization of orthoboric acid and other properties of boron-bearing aqueous solutions. The inclusions contain aqueous or water-carbon dioxide solutions of boric acid with Na, K, and Ca (sometimes Fe, Mg, Li, and Cs) chlorides, bicarbonates, fluorides, and probably minor amounts of other compounds. Boric acid solutions occurred in a wide range of mineral-forming conditions. The homogenization temperatures vary from 450 to 90 degrees C; fluid pressure, from 1480-40 bar; H3BO3 Concentration, from 26.5-2.4 wt %; and salinity, from 38.2-1.0 wt % NaCl equiv. The water-carbon dioxide inclusions contain 20.2-3.5 wt % CO2. It was found that concentrated boric acid fluids played an active role in the mineral-forming processes in zones near and directly in cavities of miarolitic pegmatites independent on the mineral composition, association, age, and geologic setting of pegmatites. An inference was substantiated on the crystallization of minerals of tourmaline-bearing assemblages in granitic pegmatites and other rocks of a hydrothermal origin under the influence of concentrated boric acid solutions. First, conclusive evidence was obtained on the participation of concentrated boron-bearing fluids in the processes of hydrothermal tourmaline formation. The petrologic consequences of the discovery of such solution are discussed with application to the understanding of granitic pegmatite genesis. It is suggested that inclusions of boric acid solutions will be found in all tourmaline-bearing and some topaz-beryl miarolitic pegmatites of the world, in the USA, Brazil, Afghanistan, Pakistan, Nepal, Africa (Tanzania, Mozambique, Nigeria, Zimbabwe, and Namibia), Madagascar, and Elba. It is highly probable that similar inclusions will be found in minerals from various boron-bearing hydrothermal rocks, greisens, hydrothermal associations, and products of volcanic exhalations. The importance of sassolite discovery for boron isotope geochemistry is emphasized. A method was proposed for the determination of the factor of boron isotope fractionation between solid phases and mineral-forming fluid using water extracts from minerals. [ DOI ]

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