Heterogeneity of water in garnets from UHP eclogites, eastern Dabieshan, China

Xia, Qing; Sheng, Yue; Yang, Xiaozhi; Huang, Yu

doi:10.1016/j.chemgeo.2005.08.003

Cited by 86 publications

(84 citation statements)

References 34 publications

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“…30,31 Clusters of water molecules were observed to occur by transmission electron microscopy (TEM) and FTIR together with structural hydroxyl in garnet from eclogite at the same locality. 32,33 For the online TC/EA-MS analysis, the garnet 04BXL02 and biotite NBS-30 were both preheated for 12 h at 908C to eliminate adsorbed water on the sample surface. Mineral grains of 40 to 60 mm size were used in the analysis.…”

Section: Nominally Anhydrous Mineralmentioning

confidence: 99%

An online method combining a thermal conversion elemental analyzer with isotope ratio mass spectrometry for the determination of hydrogen isotope composition and water concentration in geological samples

Gong

Zheng

Chen

2007

Rapid Comm Mass Spectrometry

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An online continuous-flow method, combining a thermal conversion elemental analyzer (TC/EA) with isotope ratio mass spectrometry (MS), is evaluated for the determination of both the hydrogen isotope composition and the water concentration of hydrous and nominally anhydrous minerals. The technique involves reduction of hydrous minerals or nominally anhydrous minerals by reaction with glassy carbon at 1450 degrees C in a helium stream. The product gases, H2 and CO, are separated on a gas chromatographic column prior to analysis in the mass spectrometer. Calibration curves for the H concentration analysis were generated from a standard of benzoic acid (C7H6O2) that has an H concentration of 5.0 wt%; the analytical uncertainties were better than +/-0.05% in our runs. Two standards of material with given D values, polyethylene IAEA-CH-7 and biotite NBS-30, were tested for the purpose of calibrating a natural garnet 04BXL02 representing nominally anhydrous minerals. Preheating at 90 degrees C for 12 h was found to be suitable for removing adsorption water on the sample surface. This results in constant D values and total H2O contents for the garnet, with weighted means of -94 +/- 1 and 522 +/- 11 ppm (wt), respectively. The TC/EA-MS technique allows routine analysis of sample sizes as small as 0.01 microL H2O. For natural minerals, absolute reproducibilities for D values are +/-0.5 to +/-2 (1) and relative uncertainties for total H2O concentrations are at levels of +/-1% to +/-3% (1). Therefore, this online method can be used for the quantitative determination of H isotope composition and H2O concentration of either hydrous or anhydrous minerals.

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Section: Nominally Anhydrous Mineralmentioning

confidence: 99%

An online method combining a thermal conversion elemental analyzer with isotope ratio mass spectrometry for the determination of hydrogen isotope composition and water concentration in geological samples

Gong

Zheng

Chen

2007

Rapid Comm Mass Spectrometry

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“…While some of these hydrous minerals may be present in small amounts in HP to UHP eclogites, some UHP eclogites may contain neither of these hydrous minerals. Instead, they contain hundreds to thousands of parts per million (ppm) H 2 O within NAMs such as garnet and pyroxene, not only as structural OH in point defects (Katayama and Nakashima 2003;Xia et al 2005;Katayama et al 2006;Chen et al 2007;Sheng et al 2007;Zhao et al 2007a) but also as molecular H 2 O in surface and volume defects (Su et al 2002;Xiao et al 2002;Fu et al 2003;Gao et al 2007;Ni et al, 2008;Zhang et al 2008;Meng et al 2009;Mukherjee and Sachan 2009). Analyses of the total water in NAMs yield the maximum water contents of about 2,500 ppm and about 3,500 ppm, respectively, in garnet and omphacite at UHP conditions (Chen et al 2011;Gong et al 2013).…”

Section: Water In Subduction-zone Rocksmentioning

confidence: 99%

Geochemistry of continental subduction-zone fluids

2014

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The composition of continental subduction-zone fluids varies dramatically from dilute aqueous solutions at subsolidus conditions to hydrous silicate melts at supersolidus conditions, with variable concentrations of fluid-mobile incompatible trace elements. At ultrahigh-pressure (UHP) metamorphic conditions, supercritical fluids may occur with variable compositions. The water component of these fluids primarily derives from structural hydroxyl and molecular water in hydrous and nominally anhydrous minerals at UHP conditions. While the breakdown of hydrous minerals is the predominant water source for fluid activity in the subduction factory, water released from nominally anhydrous minerals provides an additional water source. These different sources of water may accumulate to induce partial melting of UHP metamorphic rocks on and above their wet solidii. Silica is the dominant solute in the deep fluids, followed by aluminum and alkalis. Trace element abundances are low in metamorphic fluids at subsolidus conditions, but become significantly elevated in anatectic melts at supersolidus conditions. The compositions of dissolved and residual minerals are a function of pressure-temperature and whole-rock composition, which exert a strong control on the trace element signature of liberated fluids. The trace element patterns of migmatic leucosomes in UHP rocks and multiphase solid inclusions in UHP minerals exhibit strong enrichment of large ion lithophile elements (LILE) and moderate enrichment of light rare earth elements (LREE) but depletion of high field strength elements (HFSE) and heavy rare earth elements (HREE), demonstrating their crystallization from anatectic melts of crustal protoliths. Interaction of the anatectic melts with the mantle wedge peridotite leads to modal metasomatism with the generation of new mineral phases as well as cryptic metasomatism that is only manifested by the enrichment of fluid-mobile incompatible trace elements in orogenic peridotites. Partial melting of the metasomatic mantle domains gives rise to a variety of mafic igneous rocks in collisional orogens and their adjacent active continental margins. The study of such metasomatic processes and products is of great importance to understanding of the mass transfer at the slab-mantle interface in subduction channels. Therefore, the property and behavior of subduction-zone fluids are a key for understanding of the crust-mantle interaction at convergent plate margins.

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“…Удачная; [Matsyuk, Langer, 2004] -кимберлиты Сибирской платформы; [Bell et al, 2003] -кимберлитовые трубки Южной Африки; [Bell et al, 2004] -ме-гакристы кимберлитовой тр. Монастери, Южная Африка; [Li et al, 2008] -мантийные ксенолиты, базальты плато Колорадо; [Ingrin, Skogby, 2000] -ксенолиты шпинелевых лерцолитов, США; [Bell, Rossman, 1992] -кимберлитовые трубки Южной Африки; Peslier, 2010] -ксенолиты шпинелевых и гранатовых лерцолитов, США; [Katayama et al, 2006] -эклогиты из метаморфических пород сверхвысоких давлений, Кокчетавский массив, Казахстан; [Xia et al, 2005] -эклогиты из метаморфи-ческих пород сверхвысоких давлений, Дабишан, Китай; [Rossman et al, 1989] -ультрабарический массив Дора-Майра, Западные Альпы; [Matsyuk et al, 1998] -ксенолиты из кимберлитовых трубок Сибирской платформы; -ксенолиты эклогитов из кимберлитовой тр. Удачная; [Wang et al, 1996] -мегакристы из ультраосновных диатрем плато Колорадо; [Lu, Keppler, 1997] -ультрабарический массив Дора-Майра, Западные Альпы; ] -метаморфические породы сверхвысоких давлений Кокчетавский массив, Казахстан; [Smyth et al, 1991] -кимберлитовая тр.…”

Section: обсуждение результатовunclassified

WATER CONTENT IN MINERALS OF MANTLE XENOLITHS FROM THE UDACHNAYA PIPE KIMBERLITES (Yakutia)

2014

GiG

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Приведены результаты исследования распределения воды среди основных породообразующих номинально безводных минералов мантийных ксенолитов из кимберлитовой тр. Удачная (Якутия) с ис-пользованием инфракрасной спектроскопии. Были изучены образцы ксенолитов перидотитового и экло-гитового парагенезисов. Во всех минералах зафиксированы колебания, относящиеся к гидроксильным дефектам в их структурах. В перидотитах оливин содержит H 2 O (г/т) 23-75, ортопироксен -52-317, клинопироксен -29-126, гранат -0-95. В эклогитах гранат содержит H 2 O до 833 г/т, клинопи-роксен -до 1898 г/т (~ 0.19 мас. %). Сопоставление полученных данных с результатами предыдущих исследований содержания воды в отдельных минералах мантийных ксенолитов указывает на значитель-ный разброс концентраций Н 2 О как в пределах разных кимберлитовых провинций, так и в пределах отдельной кимберлитовой тр. Удачная. Исходя из объемных соотношений минеральных фаз в изученных ксенолитах, концентрация воды в перидотитах изменяется в узких пределах и оценивается в 38-126 г/т. В то же время содержание воды в исследованных ксенолитах эклогитов существенно выше и варьирует в широких пределах (391-1112 г/т). Номинально безводные минералы, верхняя мантия, эклогит, перидотит, ИК-спектроскопия. WATER CONTENT IN MINERALS OF MANTLE XENOLITHS FROM THE UDACHNAYA PIPE KIMBERLITES (Yakutia)A.L. Ragozin, A.A. Karimova, K.D. Litasov, D.A. Zedgenizov, and V.S. Shatsky Distribution of water among the main rock-forming nominally anhydrous minerals of mantle xenoliths of peridotitic and eclogitic parageneses from the Udachnaya kimberlite pipe, Yakutia, has been studied by IR spectroscopy. The spectra of all minerals exhibit vibrations attributed to hydroxyl structural defects. The content of H 2 O (ppm) in minerals of peridotites is as follows: 23-75 in olivine, 52-317 in orthopyroxene, 29-126 in clinopyroxene, and 0-95 in garnet. In eclogites, garnet contains up to 833 ppm H 2 O, and clinopyroxene, up to 1898 ppm (~0.19 wt.%). The obtained data and the results of previous studies of minerals of mantle xenoliths show wide variations in H 2 O contents both within different kimberlite provinces and within the Udachnaya kimberlite pipe. Judging from the volume ratios of mineral phases in the studied xenoliths, the water content varies over narrow ranges of values, 38-126 ppm. At the same time, the water content in the studied eclogite xenoliths is much higher and varies widely, 391-1112 ppm. Nominally anhydrous minerals, upper mantle, eclogite, peridotite, IR spectroscopy ВВЕДЕНИЕВода играет важную роль как в приповерхностных, так и в глубинных геологических процессах. Поведение и роль воды в верхней мантии и, в частности, в наиболее глубинных алмазсодержащих пара-генезисах обсуждается уже в течение длительного времени [Соболев, 1974]. Изучение мантийных ксенолитов ультраосновного состава из кимберлитовых трубок [Bell, Rossman, 1992] и магм мантийного происхождения [Michael, 1988] показало, что мантия остается громадным резервуаром воды внутри Земли. Водород в форме Н 2 О и гидроксил-и...

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Heterogeneity of water in garnets from UHP eclogites, eastern Dabieshan, China

Cited by 86 publications

References 34 publications

An online method combining a thermal conversion elemental analyzer with isotope ratio mass spectrometry for the determination of hydrogen isotope composition and water concentration in geological samples

An online method combining a thermal conversion elemental analyzer with isotope ratio mass spectrometry for the determination of hydrogen isotope composition and water concentration in geological samples

Geochemistry of continental subduction-zone fluids

WATER CONTENT IN MINERALS OF MANTLE XENOLITHS FROM THE UDACHNAYA PIPE KIMBERLITES (Yakutia)

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