Part I: The general geology of the Lacey's Creek area, Dayboro, south east Queensland. Part II: Petrological study of two ultramafic suites, Strangways Range, central Australia

Ranasinghe, Nimal Sripala (1976). Part I: The general geology of the Lacey's Creek area, Dayboro, south east Queensland. Part II: Petrological study of two ultramafic suites, Strangways Range, central Australia Honours Thesis, School of Physical Sciences, The University of Queensland.

       
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Author Ranasinghe, Nimal Sripala
Thesis Title Part I: The general geology of the Lacey's Creek area, Dayboro, south east Queensland. Part II: Petrological study of two ultramafic suites, Strangways Range, central Australia
School, Centre or Institute School of Physical Sciences
Institution The University of Queensland
Publication date 1976
Thesis type Honours Thesis
Supervisor N. C. Stevens
A. F. Wilson
Total pages 24
Language eng
Subjects 0403 Geology
Formatted abstract
Part I

The underlying formations of the Lacey's Creek area are the Bunya Phyllite and Neranleigh-Fernvale Beds. No significant variations of lithologies occur in the Bunya Phyllite. Due to later contact metamorphism its metamorphic grade has been modified from quartz-albite-muscovite-chlorite subfacies of the Greenschist Facies to quartz-biotite-muscovite-chlorite subfacies.

The Neranleigh-Fernvale Beds consist essentially of volcanics and sedimentary rocks. Development of a foliation and recrystalization in these beds is the result of mild regional metamorphism.

All rock units exhibit a north westerly bedding/foliation trend parallel with the regional strike and a southwesterly dip. The area lies on the eastern limb of a south plunging synform.

A chemically active environment of deposition suitable for rapid hydrothermal alteration has prevailed.

Greywacke, argillite and chert are indicative of continental slope to abyssal environments.

Part II

Two suites of rocks, (a) gedrite-spinel-bearing ultramafic rocks and (b) sapphirine bearing rocks, collected from the vicinity of Johannsen's Phlogopite Mine, Strangways Range, central Australia have been petrologically examined.

Based mainly on such properties as refraccive indices, and cell size determinations of the major mineral phases and on their textural relationships an attempt is made to elucidate the polymetamorphic his tory and original bulk compositions of the rocks. An original granulite facies metamorphism (Ml) affected the region. This produced cordierite, gedrite and hypersthene in appropriate rocks. During a second metamorphism (M2) orthopyroxene was developed at the expense of gedrite in one suite, whereas orthopyroxene and sapphirine were developed in the other. Though the pre-M2 orthopyroxene was developed at the expense of gedrite in one suite, whereas orthopyroxene and sapphirine were developed in the other. Though the pre-M2 mineral assemblages of the two suites were essentially similar, the preferential genesis of sapphirine is attributed to higher PH₂O at a given P and T. Subsequently a fluorine phlogopite was produced during K-metasomatism (M3), and this has affected the sapphirine-bearing suite more than the other.

In both suites the bulk composition can be related to metamorphic equivalents of a Precambrian aluminous soil profile.
Keyword Geology -- Queensland -- Lacey's Creek Region
Petrology -- Northern Territory -- Strangways Range
Ultrabasic rocks
Additional Notes Other Title: Petrological study of two ultramafic suites, Strangways Range, Central Australia.
Other Title: General geology of the Lacey's Creek Area, Dayboro, southeast Queensland.

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
 
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Created: Wed, 26 Nov 2014, 12:28:47 EST by Mary-Anne Marrington on behalf of Scholarly Communication and Digitisation Service