The fact that the highest LREE
/HREE ratio is found in claystone indicates that clay minerals are responsible for controlling LREEs
rather than HREEs.
The lower LREE
and HREE abundances in the QFP dyke, granodiorite stock, and Hawkshaw granite, relative to more primitive phases of the Pokiok Batholith, suggest low temperature fractionation process (e.
REE patterns display LREE
enrichment relative to HREE, with La and Yb concentrations about 100 and 10 times chondrite values, respectively.
REE patterns of volcanic and plutonic rocks are similar, with most showing parallel patterns and continuous depletion from LREE
to HREE, with the exception of slight positive Eu anomalies in a few samples (Fig.
Thorium and Nb show a similar behaviour to the LREE
, being most abundant in the red dust samples from Ormiston and Silverton, but depleted in the Ormiston river gravel.
Overall REE abundances show that all of the samples are LREE
enriched with La/Yb cn ratios ranging from [approximately equal to]7.
The fractional degree of HREE and LREE
is remarkable, and exhibits a distinct LREEs
-enriched pattern because of the sedimentary environment and climate change.
Garnet preferentially incorporates HREE over LREE
, so that a steepened REE slope (i.
The steep pattern with a negative slope is characteristic of alkalic basalts produced by partial melting of garnet bearing material (Ragland, 1989), where the HREE are retained in garnet relative to LREE
Results have consistently reconfirmed apparent uniform rare earth grades and an estimated, approximate 70% ratio of HREE to LREE
Geochemical pattern of LREE
and multi-elements show a strong fractionation La/Yb > 8 with typically low contents of Yb [less than or equal to] 1.
The Carrabassett Formation shows the largest range in REE abundances, with LREE
between 36 and 158 times chondrite values and [(La/Lu).