01whole.pdf (5.96 MB)
Download file

Contact metamorphism and granitic emplacement in the Tamworth area

Download (5.96 MB)
thesis
posted on 28.03.2022, 11:38 authored by David Hales
The Moonbi Adamellite is a Permo-Triassic 'I'-type pluton which has intruded into the upper crust in the New England Orogen, N.S.W. The wall rocks covered in this study make up part of the Tamworth Terrane. They consist of argillites, arenites, conglomerates and limestones. The limestones have been separated into autochthonous or allochthonous deposits. The mafic igneous rocks are considered to be intrusive. They include an as yet unrecognised intrusion: the Oaky Creek andesite, which is found to the north of the Tamworth area. -- Contact metamorphism has been recognized within an aureole 3-4 kms wide. Rocks of the upper hornblende hornfels fades are found at the highest grades along the contact. The biotite isograd was seen as the boundary between the contact metamorphic rocks and the regional Tamworth Terrane. The regional geology in the Tamworth Terrane indicates a confining pressure of approximately 1 kbar at the time of emplacement of the adamellite. Prograde metamorphic assemblages indicate that the contact metamorphic fluids were water rich (XcO2<0.25). The source of the fluids is from prograde reactions and from meteoric water. The precursor magma rose through the crust as a water under-saturated magma. The magma is considered to have absorbed fluids from the contact rocks through fractures and permeable units. The water is hypothesised to have been then released through pegmatite dykes as the magma crystallised. -- A model of transport and emplacement of the Moonbi Adamellite involves a twostage mechanism. Initial space was made through roof lifting along faults and fractures in the cold country rocks. Then as the rocks became hot and infiltrated by fluids they became susceptible to deformation as increasing magma joined the intrusion through a feeder dyke. This caused weak syn-intrusive deformation in the wall rocks.

History

Table of Contents

Introduction -- 2. Geology of the Tamworth Area -- 3. Contact metamorphism -- 4. Contact metamorphic fluids -- 5. Granitic transport and emplacement -- 6. Conclusion.

Notes

Bibliography: pages 85-90

Awarding Institution

Macquarie University

Degree Type

Thesis bachelor honours

Degree

BSc (Hons), Macquarie University

Year of Award

1993

Principal Supervisor

Ron H. Vernon

Rights

Copyright disclaimer: http://www.copyright.mq.edu.au Copyright David Hales 1993.

Language

English

Jurisdiction

New South Wales

Extent

98 pages illustrations (some colour), maps

Former Identifiers

mq:28055 http://hdl.handle.net/1959.14/266491 2073091