Subcompositional Patterns in Cenozoic Volcanic Rocks of Hungary
- PDF / 359,026 Bytes
- 24 Pages / 432 x 648 pts Page_size
- 41 Downloads / 157 Views
Subcompositional Patterns in Cenozoic Volcanic Rocks of Hungary1 J. A. Mart´ın-Fern´andez,2 C. Barcel´o-Vidal,2 ´ Kov´acs,3 and G. P. Kov´acs3 V. Pawlowsky-Glahn,2 L. O. Data selected from an extensive major element database of Cenozoic volcanic rocks (including calcalkaline andesites, dacites, rhyolites, and alkali basalts) of Hungary are used to illustrate the detection and modeling of subcompositional patterns using a statistical analysis based on the assumption that relative differences between the observed values are more meaningful than absolute ones. In particular, two roughly linear compositional patterns (associated one to the alkaline basalts, the other to the calcalkaline series) are revealed and evaluated, and it is shown how principal component analysis can be used to obtain the estimated subcomposition of their incidental intersection point. KEY WORDS: Aitchison geometry, biplot, logratio transformation, simplex, ternary diagram, volcanic rocks, major element geochemistry, petrogenesis, Carpatho–Pannonian Region.
INTRODUCTION The present study is based on an extensive major element database of Cenozoic volcanic rocks of Hungary. This data set has a fairly good representation of the young volcanic formations of the region except for the subduction-related calc´ Kov´acs and Kov´acs (2001) alkaline andesitic series of the Eastern Carpathians. O. give an introductory analysis of the database based on traditional statistical tools, mainly univariate and bivariate techniques. In the present paper we apply multivariate statistical methods based on the compositional methods introduced by Aitchison in 1986 (2003). In using these techniques, we assume that relative differences between the observed values are more meaningful than absolute ones. We analyze subcompositional patterns, which might contribute to the understanding of petrogenetic processes that occurred in the Carpatho–Pannonian Region during 1Received
20 February 2004; accepted 28 February 2005.
2Department d’Inform` atica i Matem`atica Aplicada, Campus Montilivi, Universitat de Girona, E-17071
Girona. E-mail: [email protected]; [email protected]; [email protected] Geological Survey, H-1440 Budapest, P. O. Box 17, Hungary. E-mail:lajos.okovacs @mgsz.hu; [email protected]
3Hungarian
729 C 2005 International Association for Mathematical Geology 0882-8121/05/1000-0729/1
730
´ Kov´acs, and Kov´acs Mart´ın-Fern´andez, Barcel´o-Vidal, Pawlowsky-Glahn, O.
the Cenozoic. More specifically, the aim of this work is to understand the major element compositional variation of the volcanic suites, based on a large number of samples, through establishing the principal subcompositional patterns within two groups (alkaline basalts and calc-alkaline series), and attempting to reveal or reject any possible link between the corresponding patterns. The two groups traditionally distinguished in the region (e.g., Szab´o, Harangi, and Csontos, 1992; P´ecskay and others, 1995) separate well based on both their chemical and mineralogical composit
Data Loading...
