Roadend Nunatak, Touchdown Glacier

Metasomatic enrichment of the mantle by volatile elements originating from the lower mantle, and 

Accumulation of radiogenic Sr by radioactive decay of Rb in the mantle having a high Rb/Sr ratio as a result of alternatives 1 and 2 above 

The interpretation of Sr/ Sr ratios in continental tholei-ites is ambiguous. Presently available data on the Ferrar Group do not give strong support to models involving either selective contamination by crustal-derived components or generations of the tholeiites in a heterogeneous mantle. 

In a subsequent report, Kyle et al. (1983) wrote that the basalts on Gorgon Peak (Prince Albert Mountains)  

The correlations of major-elements with initial Sr/ Sr ratios are positive for SiO and TiO, and negative for AljOj, MgO, and CaO. In addition, the concentrations of the light rare earth elements and strontium show excellent positive correlations with initial Sr/ Sr ratios. Nevertheless, Kyle et al. (1983) argued that the initial Sr/ Sr ratio of the Ferrar magmas was about 0.709 and that the addition of crustal strontium raised the value only incrementally to 0.7115. However, the evidence that sills of Ferrar Dolerite have a distinctive crustal character compelled Kyle et al. (1983) to conclude  

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The exposed thickness of the Basement sill is 150 m but its true thickness is unknown because the lower contact is covered by the ice of the Touchdown Glacier. The thickness of the Peneplain sill is 148 m but its original thickness is also unknown because the top of the sill has been eroded. The dolerite exposed on the sununit of Roadend Nunatak is deeply weathered and is not covered by glacial erratics or till. 

Fig. 13.13 The Roadend Nunatak is located at the confluence of the Touchdown and Darwin glaciers close to Bastion Hill in the Brown Hills. This nunatak contains partial sections of the Basement siU and of the Peneplain sid. The Basement sill intruded the Hope Granite of the Granite Harbor Intrusives. " e Peneplain siU is underlain by a sliver of the Brown Hills...

Fig. 13.17 The concentrations of nickel closely follow MgO and reach a maximum of 299 ppm in the lower hypersthene dolerite zone of the Basement sill on Roadend Nunatak where copper reaches a minimum concentration of 103 ppm. The concentration profiles of nickel and copper in this sill closely resemble the distribution of these elements in the Vanda sill in Fig. 13.11 based on the data of Gunn (1966). The lower contact of the Basement sill of Roadend Nuntak is covered by the ice of the Touchdown Glacier (Data from Kibler 1981)...

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