Please use this identifier to cite or link to this item:
http://hdl.handle.net/10174/2969
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Title: | Understanding Geological Data Distribution and |
Authors: | Pereira, M. Francisco Lucio, Paulo |
Keywords: | Contingency table Multivariate analysis Non-symmetry Migmatites Shearing Melt flow |
Issue Date: | 2007 |
Abstract: | Insufficient field test results and a sufficiently large degree of spatial disorder
exhibited by melt flow properties on sheared migmatites leads us to use stochastic
methods to describe the distribution and orientation of leucogranitoid veins in sheared
continental crust. Qualitative data present challenges to evaluators seeking to analyse
visual information from spatial observations. In this manuscript, we work through
a structured approach to analyse qualitative data based on an interactive process of
considering the objective of the analysis, reviewing suitable options, and working
through interpretation. Techniques include grouping, summarizing, finding patterns,
discovering relationships, and developing and testing relationships. The aim of this
paper is to give an overview of the methodological contribution in multidimensional
categorical data analysis based on correspondence analysis, which enables the analysis
of a contingency table when the behaviour of one variable is supposed to be dependent
on the other cross-classified variable. The analytical procedures gave statistically
valid and significantly similar results for the geometrical relationships between different
attributes observed in the Almansor migmatites (Évora High-Grade Metamorphic
Terrains, Portugal)—leucogranitoid veins, boudins/rock fragments, folds, shear
planes, and host rock/diatexite layering. The interpretation of the obtained results allowed
the definition of two main geological implications. First, the association of the
host rock/diatexite with the leucogranitoids I defines the compositional layering of
these migmatites (with 290°–310°-trending). Secondly, the shearing is responsible
for the observed structural complexity. Here leucogranitoids tend to occur associated with local perturbations of the main 290°–310°-trending of the compositional layering.
They tend to occur discordant to the compositional layering (foliation) strike
filling 260°–270°-trending c′-type extensional shear planes, filling dilatant structures
in between or/and surrounding boudins/rock fragments and affected by folding. The
applied stochastic analysis was a useful approach to properly examine and quantify
the structural variability of this complex natural phenomenon. |
URI: | http://hdl.handle.net/10174/2969 |
Type: | article |
Appears in Collections: | GEO - Publicações - Artigos em Revistas Internacionais Com Arbitragem Científica
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