Chaotic three-dimensional distribution of Ba, Rb, and Sr in feldspar megacrysts grown in an open magmatic systemReportar como inadecuado




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Contributions to Mineralogy and Petrology

, Volume 162, Issue 5, pp 909–927

First Online: 19 April 2011Received: 09 August 2010Accepted: 25 March 2011

Abstract

As has been demonstrated in recent years, the heterogeneities of coeval magmas can be more successfully revealed by zoned megacrysts rather than by analysis of the whole rocks hosting them. Here, the geochemical heterogeneities of feldspar megacrysts from the Karkonosze granite, Poland, are investigated by LA-ICP-MS. The crystals are the product of migration and growth in regions of poorly mixed magmas. 3D-modeling of the Ba, Sr, and Rb distributions emphasizes the importance of micro-domain growth morphologies. Two models of element behavior—a relative concentration model and a composition gradient model—provide a potentially effective tool for tracking the mixing process on a microscale. Measured concentrations of elements of different mobilities do not agree with what might be expected from the mixing of two end-member magmas. If mixing was the only process occurring, linear correlations between the concentrations of any two elements should be observed; this, however, is not the case. For combinations of any two of the three elements, modeling reveals differing non-linear correlations between concentrations. The megacryst heterogeneities provide an insight into how mixing magmas are chaotically advected to growing crystals and the degree of inter-magma element exchange between the magmas.

KeywordsMixing Element mobility Diffusion Alkali feldspar 3D-depiction Cut-off value models Gradient models Probabilistic models Geochemical heterogeneity Karkonosze granite Communicated by J. Hoefs .

Electronic supplementary materialThe online version of this article doi:10.1007-s00410-011-0631-6 contains supplementary material, which is available to authorized users.

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Autor: Ewa Słaby - Michał Śmigielski - Tomasz Śmigielski - Andrzej Domonik - Klaus Simon - Andreas Kronz

Fuente: https://link.springer.com/



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