Jadeitite from Guatemala : new observations and distinctions among multiple occurrences
Harlow, G. E. (American Museum of Natural History. Department of Earth and Planetary Sciences)
Sisson, V. B. (University of Houston. Department of Earth and Atmospheric Sciences)
Sorensen, S. S. (Smithsonian Institution. Department of Mineral Sciences)

Date:	2011
Abstract:	In Guatemala, jadeitite occurs as blocks in serpentinite mélange in distinct settings on opposite sides of the Motagua fault. Jadeitites north of the Motagua fault are associated with eclogites, blueschists, and garnet amphibolites and distributed over a 200km E-W area. Omphacitite, omphacite - taramite metabasite, albitite, and phengite rock are found with jadeitite. The assemblages indicate formation at 6-12kbar and 300-400°C, however jadeite - omphacite pairs yield T from ~200 to >500ºC for jadeite crystallization. Jadeitites south of the Motagua fault are sourced from three separate fault slices of serpentinite in Jalapa and Zacapa departments and are distinctive: 1) Jadeitite near Carrizal Grande is found in serpentinite with lawsonite eclogites, variably altered to blueschist, and rarely in schists. A large jadeite - omphacite gap and lawsonite suggests T=300-400°C, but at high P as indicated by the presence of quartz: P>12-20kbar. Lawsonite eclogites (P=20-25kbar, T=350-450°C) occur with these jadeitites. 2) At La Ceiba, jadeitites coexist with omphacite blueschists and contain late-stage veins of quartz, diopside, cymrite, actinolite, titanite and vesuvianite. A large jadeite - omphacite gap suggests 300-400°C, but at lower P as indicated by quartz + albite: P=10-14kbar. 3) At La Ensenada jade i tites occur with lawsonite-glaucophane blueschists and chloritite. It is a fine-grained jadeite-pumpellyite rock, intensely deformed and veined with grossular, omphacite, albite and titanite, but no quartz. A large jadeite-omphacite gap and pumpellyite suggest ~200-~300°C at lower P consistent with primary albite: P=6-9kbar. The silicates contain little iron.
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Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Jadeitite ; Serpentinite ; Mélange ; HP-LT rock ; Subduction processes
Published in:	Geologica acta, Vol. 9, Núm. 3-4 (setembre-desembre 2011) , p. 363-387, ISSN 1696-5728

Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/247927
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/105.000001694
DOI: 10.1344/105.000001694

30 p, 1.8 MB

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