Mineralogy of the Gosse Pile ultramafic intrusion, central Australia. I. plagioclase
Titel:
Mineralogy of the Gosse Pile ultramafic intrusion, central Australia. I. plagioclase
Auteur:
Moore, Alan C.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 18 (1971) nr. 2 pagina's 115-125
Jaar:
1971-07
Inhoud:
An investigation of plagioclases from the Gosse Pile ultramafic layered intrusion has shown a negative correlation between strontium and anorthite content, irrespective of rock type or whether the plagioclases are cumulus or intercumulus. This general trend is regarded as reflecting the relative ease of entry of strontium into the plagioclase lattice with change in composition. Comparison of G values (Smith & Gay, 1958) of these plagioclases with those from other layered intrusions has shown that G values, measured using unheated plagioclases, cannot be used to construct a universal determinative curve. However, G values measured on heated samples can be used to determine indirectly compositions between about An45 and An86, irrespective of the source of the feldspar. The rocks from Gosse Pile show the development of antiperthite, an unusual and rare feature in layered basic intrusions, so far found only in parts of the Giles Complex. Although the cause of this is not known, especially as the K2O contents are comparable with those of “normal” plagioclases from other layered intrusions, it is suggested that high pressure may be a significant factor in promoting the exsolution of potassium feldspar.
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