Linearity spectrum analysis of multi-component magnetizations and its application to some igneous rocks from south-eastern Australia

Summary. A method that enables the objective resolution of almost parallel multi-component magnetizations is described and demonstrated. A feature distinguishing this method from others is its simultaneous analysis of demagnetization data from a group of specimens, rather than the analysis of data from one specimen at a time. The only prerequisite is that the specimens are derived from a homogeneous source. Thus for a formation carrying a simple single component magnetization, all specimens from the formation may be simultaneously reduced. For a more complicated two component magnetization it is shown that only specimens from a particular site can be considered homogeneous, and for a complex three component system each sample often requires undivided attention. Thus the workload is proportionally increased to achieve analyses of comparable reliability from data of variable quality. New pole positions from Mesozoic intrusions of the Sydney Basin, NSW are: from the Marsden Park Breccia pipe 48°S, 127°E (A95= 6°); the St Marys Breccia pipe 46°S, 150°E (A95= 8°); the Prospect Dolerite 60°S, 142°E (A95= 13°) and 53°S, 180°E (A95= 6°); and from the Dundas Breccia pipe 58°S, 162°E (A95= 36°) and 31°S, 195°E (A95= 16°). The last two formations possess multi-component magnetizations. These pole positions are consistent with previous results from south-eastern Australia.

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