Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/126521
Type: Thesis
Title: The behaviour of metamorphic apatite from mid-amphibolite to granulite facies metapelites and metapsammites: insights from the Stafford Member from the Arunta region, Australia
Author: Baggs, T. W.
Issue Date: 2014
School/Discipline: School of Physical Sciences
Abstract: The chemical behaviour of metamorphic apatite was investigated in a quasi-unchanging rock composition to gain insight into the stability of apatite and distribution of heat production in the continental crust. Samples of two rock types were collected from the Stafford Member: metapelites and metapsammites, that record calculated metamorphic conditions from mid-amphibolite facies (~ 2.1 kbar, 590 °C) to granulite facies (~ 3.9 kbar, 800 °C) conditions. The chemical compositions, petrographic relationships and abundances of accessory phosphate minerals were investigated as a function of metamorphic grade, with a focus on the relationship between apatite and monazite, both of which increase in abundance with metamorphic grade. At mid-amphibolite facies metamorphic conditions, apatite growth is driven by the partial consumption of accessory xenotime and complete consumption of low-grade allanite and detrital apatite (Reaction 4). At upper-amphibolite facies conditions, apatite growth is driven by the partial breakdown of xenotime and plagioclase (Reaction 5). Additionally, apatite was found to be intimately linked with the breakdown of biotite and muscovite micas at all metamorphic conditions (Fig. 3 & 5), as they supply the F, Cl and OH component required for apatite growth. Granulite facies monazite growth is facilitated by the dissolution of apatite (Fig. 9) and the breakdown of xenotime (Reaction 2). However, as the major reservoir for P2O5 in the samples, the stability and high abundance of apatite at granulite facies conditions (Figures 10, 5e, 5f, 3c, 3d) is enhanced by the enrichment of P2O5 in residual samples (Table 2). Furthermore, during partial melting, heat producing elements U + Th preferentially remain in monazite relative to apatite and the melt, therefore the melt and apatite is relatively depleted in HPEs. Consequently, melt loss of HPE depleted segregates could enrich HPEs in the residual, partially melted monazite bearing rocks of the Stafford Member.
Dissertation Note: Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2017
Where: Arunta Block, Central Australia
Keywords: Honours; Geology; apatite; monazite; HPEs; REEs; metamorphism; geochemistry
Description: This item is only available electronically.
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the author of this thesis and do not wish it to be made publicly available, or you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals
Appears in Collections:School of Physical Sciences

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