Petrogenesis of Basalts: Examination of REE Data Using Pattern Recognition Approach Through Principal Component Analysis
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In contrast with the tholeiites, the dominant component in alkalic basalts, shows excellent covariance among the LREE and MREE. Among the alkalic basalts, the alkali olivine basalts, show a different HREE behaviour. Comparison of the coefficient patterns of the dominant component of tholeiites and alkalic basalts suggests distinct differences in their source/mechanism of formation.
Theoretical computations involving partial melting and fractional crystallisation of only the major mineral (ol, opx, cpx, garnet/spinel) prove to be inadequate to simulate the observed coefficient patterns. The inclusion of 87Sr/86Sr isotopic ratios along with REE in the PCA, generates 'features' suggestive of additional sources (interstitial liquid, accessory minerals in the mantle and/or granitic crustal contamination) as contributing factors.
The PR approach described in this work allows one to extract more information from the REE data-set than what is possible by simple chondritic normalisation.
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