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the ultramaficfmafic source prevents this from clearly being identified.
However in
general both units would lend to plOI on an cxuapolated P4 as a result of the Fl scores,
suggeslingthat a recycled source did contribute.
The investigation detailed above suggests thai it is unlikely that discrimination
diagrams have much application in Ihe study of the geochemistry of 5aI1d.stones from a
mill.ed source. sioce a dominant chemical signature cannOI be identified. It is also
notable that a grain size effect seems marked in these samples, whereas Roser and
Karsch (1988) claim thaI the grain ~ize effecI is minimised by the use of these
discriminaliondiagrams.
5 ., 5 4 Major Element GtQCbcmjstry - Pi$lamjon
This study of major clemen! geochemistry has shown a number of lhings. Firstly.
a mafic or ultramafic source is suggested by the behaviour of magnesium. Secondly.
althougb this signature prevents the clear distinclion of any others, several of the
approaches ulilised suggest input from a recycled passive margin source. Although these
observations are not sU'l'rising given thtpelrographic cbaracteristics described in cbapler
4, they WQuld be far more diffICult lO interprel in the absence of petrography. This
indicates the inadvisability ofcarrying OUl geochemical investigations wilhout supporling
peuography.
In addilion, it is clear Ihat grain size has had a major effect on chemiSlry. and for
these samples nor.e of the methods discussed above can successfully overcome the grain
size effecl. which is ultimately a consequence of mode of deposition.