Solo Nunatak

The majority of the flows in Fig. 12.19 have nearly uniform chemical compositions (e.g., SiO - 53%, MgO + CaO 18%). These profiles lack the discontinuities caused by the differences in cfamical composition of the low-Ti and high-Ti flows on Pain Mesa in Fig. 12.12. Therefore, all of the flows on Solo Nunatak belong to the low-Ti suite of the Kiikpatrick Basalt with concentrations of TiOj between 0.54% and 0.79% (Mensing 1987). 

The initial Sr/ Sr ratios of the low-Ti flows on Solo Nunatak reported by Mensing et al. (1984) range from 0.70985 to 0.71207 with an average of 0.71069 0.00001 (Ict) for 37 samples from 24 flows recalculated to 175 Ma using = 1.42 x 10 year. The average initial Sr/ Sr ratio of the Kirkpatrick Basalt on Solo Nunatak is virtually identical to the average initial St/ Sr ratios of the low-Ti flows on Pain Mesa, 

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Meisch A.T., 1969, The constant sum problem in geochemistry. In Merriam D.F. (ed.), Computer applicatiom in the earth sciertces. Plenum Press, New York, pp.. 161-176. Mensing T.M., Faure G., Jones L.M., Bowman J.R. and Hoefs J., 1984, Petrogenesis of the Kirkpatrick basalt, Solo Nunatak, northern Victoria Land Antarctica, based upon isotopic compositions of strontium, oxygen and sulfur. Contrib. Mineral. Petrol., 87, 101-108. 

The map identifies the location of Mt. Masley on Pain Mesa and of Solo Nunatak which are described in the text (Reproduced from Mensing 1987)... 

Fig. 12.17 Solo Nunatak at 72°50 S and 163°35 E is an erosional remnant located 22 km east northeast of the northern tip of Pain Mesa (Fig. 12.9). Is it composed of 23 flows of the Kirkpatrick Basalt of the low-Ti suite. Mensing...

Fig. 12.18 On the alkali-silica diagram of Cox et al. (1979) and Wilson (1989) the flows of Kirkpatrick Basalt of Solo Nunatak extend from basalt to basaltic andesite much like the lava flows on Pain Mesa (Fig. 12.14) and on Tobin Mesa (Fig. 12.10). However, the mineral composition of the phenocrysts cause all of the flows to be classified as subalkalic tholeiite basalt. In addition, all of the flows are composed of low-Ti basalt because the high-Ti basalt flows that cap Tobin and Pain mesas of the Mesa Range are not present and may have been eroded (Mensing 1987)...

Fig. 12.19 The concentration profiles of SiO and of MgO + CaO of the flows on Solo Nunatak of the Mesa Range reveal compositional irregularities of flows 2, 3, 4, and 8. However, all of the flows at this location belong to the low-Ti suite of the Kirkpatrick Basalt (Ti02 = 0.54 to 0.79%) (Mensing 1987 Mensing et al. 1984)...

Fig. 12.20 The initial Sr ratios of the 24 basalt flows on Solo Nunatak in the Mesa Range vary systematically within narrow limits between 0.70985 and 0.71207. These ratios are typical of the isotopic composition of strontium in the low-Ti flows of the Kirkpatrick Basalt of the Mesa Range. The high initial Sr/ Sr ratios indicate that the magma was either derived from a heterogeneous source in the mantle or that it was contaminated by rocks of the continental crust. The measured Sr/ Sr ratios were corrected for decay of Rb to t = 175 Ma and 1.42 x 10" year (Mensing et al. 1984)...

Fig. 12.22 The initial Sr/ Sr ratios at 175 Ma (X = 1.42 x 10" year"0 of the basalt flows on Solo Nunatak vary inversely with the reciprocals of their strontium concentrations. The fan-shaped array of data points supports the hypothesis that the magma was contaminated by strontium that was variably enriched in radiogenic Sr formed by decay of Rb in the Precambrian rocks of the crust of Antarctica (Mensing et al. 1984)...

Fig. 12. 21 The data points representing the flows on Solo Nunatak of the Mesa Range scatter above and below a 175-Ma reference isochron drawn through the average initial Sr/ Sr ratio at 0.71069 0.00007 (la). The failure of the data points to define a straight-line isochron indicates either that these flows had different initial Sr/ Sr ratios or that their Rb/Sr ratios were altered after crystallization, or both (Mensing et al. 1984)...

Fig. 12.23 Four flows (1, 3,7, and 15) on Solo Nunatak define a straight line in coordinates of the initial Sr/ Sr ratio (at 175 Ma) and the isotope composition of oxygen expressed as the value...

Fig. 12.28 The concentrations of TiO of the Kirkpatrick Basalt on Storm Peak in the Marshall Mountains range from greater than 0.4% to less that 2.4% but are not as sharply divided into low-H and high-H suites as the basalt flows on Solo Nunatak and Pain Mesa of northern Victoria Land (Data from EUiot 1970a, 1972 Faure et al. 1982 Mensing et al. 1984 Mensing 1987)...

The correlation of these parameters is consistent with mixing of basalt magma with a silica-rich partial melt of crustal rocks with elevated Sr/ Sr ratios depending on their Rb/Sr ratio and age. A second example of this phenomenon in Fig. 12.37 demonstrates that the increase of the initial Sr/ Sr ratios at 170 Ma on Storm Peak with decreasing concentrations of MgO. The pattern of variation supports the hypothesis that the basalt magma mixed with a crustal melt that had a low concentration of MgO and a high Sr/ Sr ratio. Additional correlations of initial Sr/ Sr ratios and other major elements were reported by Faure et al. (1974) for the flows on Storm Peak analyzed by Bowman (1971). The positive correlation of initial Sr/ Sr ratios of the basalt flows on Solo Nunatak (Section 12.4.1.3) was described by Mensing et al. (1983). 

Mensing TM (1987) Geology and petrogenesis of the Kirkpatrick Basalt, Pain Mesa and Solo Nunatak, northern Victoria Land, Antarctica Ph.D. dissertation. The Ohio State University, Columbus, OH... 

Flows of Kirkpatrick Basalt are also exposed on the Sheehan Tableland, Sculpture Mountain, the Monument Nunataks, and on many small nnnataks located east of the Mesa Range, including Solo... 

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