Quantitative characterization of textures in mantle spinel peridotite xenoliths
Felicity A. Tabor
Bryan E. Tabor
Hilary Downes
10.6084/m9.figshare.3454811.v1
https://geolsoc.figshare.com/articles/dataset/Quantitative_characterization_of_textures_in_mantle_spinel_peridotite_xenoliths/3454811
<p>A method for quantitative characterization of grain size in thin sections has been established for mantle spinel peridotite
xenoliths, using optical scanning of large areas of thin sections, skeletonization of grain-section outlines and computerized
measurement of individual grain-section areas. Measurements range from 218 for the coarsest example to more than 3000 in the
finest grained. Variability of the samples has been examined in relation to size and number of grain-section areas measured
by using multiple and orthogonal sections from several xenoliths. The results show a linear relationship of arithmetic mean
against additive standard deviation, including data from coarse-grained protogranular, through porphyroclastic to the finer-grained
equigranular examples. This suggests that peridotite textures form a continuous series rather than discrete groups, as suggested
by qualitative (subjective) assessment. The observed distributions of grain-section areas have been explored in relation to
their description and possible mechanistic origin. By direct measurement and comparison of cumulative number and area distribution
curves, we show that qualitatively assessed ‘typical grain sizes’ are influenced by a small number of larger grain sections.
Although the arithmetic mean and standard deviation provide a convenient method for comparison, in practice grain-section
area distributions show marked positive skewness more consistent with log-normal or power-law functions. Linear log-probability
curves also support the existence of a continuous series of peridotite textures, suggesting that the shallow lithospheric
mantle has been subject to processes of comminution and/or grain growth dependent on the Law of Proportionate Effect.
</p>
2016-06-21 12:22:08
results show
mantle spinel peridotite xenoliths
area distribution curves
peridotite textures form
grain sections
coarsest example
Proportionate Effect
peridotite textures
Measurements range
lithospheric mantle
Quantitative characterization
grain size
orthogonal sections
Geology