Contrasting mechanisms for crustal sulphur contamination of mafic magma: evidence from dyke and sill complexes from the British
Palaeogene Igneous Province
Hannah S. R. Hughes
Adrian J. Boyce
Iain McDonald
Brett Davidheiser-Kroll
David A. Holwell
Alison McDonald
Anthony Oldroyd
10.6084/m9.figshare.3453968.v1
https://geolsoc.figshare.com/articles/dataset/Contrasting_mechanisms_for_crustal_sulphur_contamination_of_mafic_magma_evidence_from_dyke_and_sill_complexes_from_the_British___Palaeogene_Igneous_Province/3453968
<p>The addition of crustal sulphur to magma can trigger sulphide saturation, a process fundamental to the development of some
Ni–Cu–PGE deposits. In the British Palaeogene Igneous Province, mafic and ultramafic magmas intrude a thick sedimentary sequence
offering opportunities to elucidate mechanisms of magma–crust interaction in a setting with heterogeneous S isotope signatures.
We present S-isotopic data from sills and dykes on the Isle of Skye. Sharp contrasts exist between variably light δ<sup>34</sup>S in Jurassic sedimentary sulphide (−35‰ to −10‰) and a local pristine magmatic δ<sup>34</sup>S signature of −2.3 ± 1.5‰. Flat-lying sills have restricted δ<sup>34</sup>S (−5‰ to 0‰) whereas steeply dipping dykes are more variable (−0‰ to −2‰). We suggest that the mechanism by which magma is
intruded exerts a fundamental control on the degree of crustal contamination by volatile elements. Turbulent flow within narrow,
steep magma conduits, discordant to sediments, and developed by brittle extension or dilation have maximum contamination potential.
In contrast, sill-like conduits emplaced concordantly to sediments show little contamination by crustal S. The province is
prospective for Ni–Cu–PGE mineralization analogous to the sill-hosted Noril’sk deposit, and Cu/Pd ratios of sills and dykes
on Skye indicate that magmas had already reached S-saturation before reaching the present exposure level.
</p>
2016-06-21 11:49:02
sequence offering opportunities
crustal sulphur
S isotope signatures
elucidate mechanisms
magma conduits
Sharp contrasts
crustal contamination
sediments show
dykes
sill complexes
Contrasting mechanisms
sulphide saturation
mafic magma
ultramafic magmas
British Palaeogene Igneous Province
magmatic δ 34 S signature
exposure level
Turbulent flow
crustal S
variably light δ 34 S
crustal sulphur contamination
Geology