Strong, localised country-rock contamination and partial homogenisation of a mafic magma: An example from west central Sweden
(2006) In Lithos 86(3-4). p.212-228- Abstract
- A dolerite sill cutting slightly older basalt in west-central Sweden shows a strong chemical variation (54%<SiO2<73%) within a restricted area (<100x100 m(2)). The linear correlation among almost all elements is extremely high; in addition, epsilon(NdT) is strongly correlated with the SiO2 content. Least-square hyperbolic-ratio and three-element ratio modelling (common denominator) suggests that most of the chemical variation is explained by mixing and/or micro-mingling. In all, we test 407 hyperbolas, of which 402 are fitted. The five ratio pairs, which could not be fitted to a hyperbola using a least-square fitting procedure, have the ratio Th/Eu in common. Testing the goodness of fit is problematic for hyperbolic distributions;... (More)
- A dolerite sill cutting slightly older basalt in west-central Sweden shows a strong chemical variation (54%<SiO2<73%) within a restricted area (<100x100 m(2)). The linear correlation among almost all elements is extremely high; in addition, epsilon(NdT) is strongly correlated with the SiO2 content. Least-square hyperbolic-ratio and three-element ratio modelling (common denominator) suggests that most of the chemical variation is explained by mixing and/or micro-mingling. In all, we test 407 hyperbolas, of which 402 are fitted. The five ratio pairs, which could not be fitted to a hyperbola using a least-square fitting procedure, have the ratio Th/Eu in common. Testing the goodness of fit is problematic for hyperbolic distributions; for comparing purposes we 4 sum the distances to chords approximating the hyperbola. Mobile and immobile elements behave similarly, suggesting that no A elements are lost or added from outside the system. The data suggests that already the most mafic of the analysed rocks is a mixture of the 'normal' dolerite and a siliceous crustal rock. A mafic magma intruded into the base of the crust, where it fractionated resulting in a decreased Mg number. The magma was then contaminated with country rocks in an intermediate magma chamber due to country rock melting; during mixing/mingling almost no fractionation took place. The contaminated rock suggests the presence of a fluid phase. This was probably a prerequisite for country-rock melting. Enrichment in some incompatible elements suggests that besides major mixing/mingling a thermochemical separation process has affected the most felsic rock enriching it in light rare earths and Zr. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/417377
- author
- Lindh, Anders LU ; Kjollerstrom, A and Solyom, Zoltan LU
- organization
- publishing date
- 2006
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- major elements, contamination, trace elements, mixing, mingling, ratio correlation, hyperbolic modelling, Sm-Nd isotopes, dolerite
- in
- Lithos
- volume
- 86
- issue
- 3-4
- pages
- 212 - 228
- publisher
- Elsevier
- external identifiers
-
- wos:000235408700002
- scopus:30944451950
- ISSN
- 0024-4937
- DOI
- 10.1016/j.lithos.2005.06.005
- language
- English
- LU publication?
- yes
- id
- 2eb7bb5f-de89-41fb-95bc-4d1b1d645b66 (old id 417377)
- date added to LUP
- 2016-04-01 11:42:19
- date last changed
- 2022-01-26 17:00:42
@article{2eb7bb5f-de89-41fb-95bc-4d1b1d645b66,
abstract = {{A dolerite sill cutting slightly older basalt in west-central Sweden shows a strong chemical variation (54%<SiO2<73%) within a restricted area (<100x100 m(2)). The linear correlation among almost all elements is extremely high; in addition, epsilon(NdT) is strongly correlated with the SiO2 content. Least-square hyperbolic-ratio and three-element ratio modelling (common denominator) suggests that most of the chemical variation is explained by mixing and/or micro-mingling. In all, we test 407 hyperbolas, of which 402 are fitted. The five ratio pairs, which could not be fitted to a hyperbola using a least-square fitting procedure, have the ratio Th/Eu in common. Testing the goodness of fit is problematic for hyperbolic distributions; for comparing purposes we 4 sum the distances to chords approximating the hyperbola. Mobile and immobile elements behave similarly, suggesting that no A elements are lost or added from outside the system. The data suggests that already the most mafic of the analysed rocks is a mixture of the 'normal' dolerite and a siliceous crustal rock. A mafic magma intruded into the base of the crust, where it fractionated resulting in a decreased Mg number. The magma was then contaminated with country rocks in an intermediate magma chamber due to country rock melting; during mixing/mingling almost no fractionation took place. The contaminated rock suggests the presence of a fluid phase. This was probably a prerequisite for country-rock melting. Enrichment in some incompatible elements suggests that besides major mixing/mingling a thermochemical separation process has affected the most felsic rock enriching it in light rare earths and Zr.}},
author = {{Lindh, Anders and Kjollerstrom, A and Solyom, Zoltan}},
issn = {{0024-4937}},
keywords = {{major elements; contamination; trace elements; mixing; mingling; ratio correlation; hyperbolic modelling; Sm-Nd isotopes; dolerite}},
language = {{eng}},
number = {{3-4}},
pages = {{212--228}},
publisher = {{Elsevier}},
series = {{Lithos}},
title = {{Strong, localised country-rock contamination and partial homogenisation of a mafic magma: An example from west central Sweden}},
url = {{http://dx.doi.org/10.1016/j.lithos.2005.06.005}},
doi = {{10.1016/j.lithos.2005.06.005}},
volume = {{86}},
year = {{2006}},
}