Considerazioni sui rapporti tra le seri alte in K e l'arco vulcanico indonesiano alla luce dei vulcani Muria e Lasem (Giava)  [Relationship between the K-rich series and the Indonesian volcanic arc in light of data on the Muria and Lasem volcanoes, Java]

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Alternate Title:Relationship between the K-rich series and the Indonesian volcanic arc in light of data on the Muria and Lasem volcanoes, Java
Authors:Calanchi, N.; Lucchini, F.; Rossi, P. L.
Author Affiliations:Primary:
Univ. Bologna, Ist. Min. Petrogr., Bologna, Italy
Volume Title:Mineralogica et Petrographica Acta
Source:Mineralogica et Petrographica Acta, Vol.27, p.15-34. Publisher: Istituto di Mineralogia e Petrografia dell'Universita di Bologna, Bologna, Italy. ISSN: 0540-1437
Publication Date:1983
Note:In Italian with English summary. 2 p. refs.; illus. incl. 30 anal., 6 tables
Summary:The volcanoes of Muriah and Lasem in central Java were active in early-middle Pleistocene, their products consisting mainly of lahars, pyroclastic flows, fall and surge deposits with the lava flows limited to the collapse of domes. Samples studied petrographically and geochemically (21 major-element rock analyses) include: 1) a K-rich calc-alkaline series; 2) a shoshonite series; and 3) a highly undersaturated leucite K-alkaline series (these only in the area of the Murtah volcano). Members of the K-calc-alkaline suite range from high-K basaltic andesite to high-K dacite and are characterized by phenocrysts of plagioclase, salite, basaltic hornblende and sometimes orthopyroxene. The shoshonite series range from shoshonite basalts and shoshonites to trachytes, with phenocrysts of plagioclase, iron-rich pargasitic and tschermakitic amphiboles, biotite and salite, with sanidine in the trachytes. The undersaturated series are leucite tephrites with phenocrysts of leucite olivine (Fo89) and salite-diopside. Microprobe analyses are reported for most of these minerals. All three rock groups have high Al and low Ti abundances typical of island arc rocks; initial 87Sr/86Sr values are in the range 0.7040-0.7049 and preclude any substantial crustal contribution. No direct connection between the leucite-bearing rocks and rifting can be admitted. Such undersaturated rocks were probably generated by partial melting of phlogopite-rich peridotitic mantle followed by enrichment in volatile hygromagmatophile elements by migration of fluid through the mantle, triggered perhaps by transverse faults crossing the Muriah area. [R.A.H.]
Subjects:Calc-alkalic composition; Electron probe data; Igneous rocks; Island arcs; Major elements; Minor elements; Models; Petrology; Plate tectonics; Potassic composition; Subduction; Tectonophysics; Volcanic rocks; Volcanoes; Volcanology; Asia; Far East; Indonesia; Java; Lasem; Muria; Ratios
Abstract Numbers:86M/1043
Record ID:1987036338
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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