Academic literature on the topic 'Olary Inlier'

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In the central part of the eastern Weekeroo Inlier, Olary Domain, two types of granite have been identified. This thesis explores both granite types in order to explain possible tectonic environments and geological evolution during the Proterozoic. The A-type Walter Outalpa granite is characterised by high Si02, Zr, Nb, Y, rare earth elements (REE) and low MgO, CaO, Ti02, P205 and light field strength elements (LFSE). High zircon saturation temperatures differentiate this fractionated A-type granite from potential fractionated I-type granites. The peraluminous granite is characterised by high Si0, Al203, Rb, U, Th, and low MgO, CaO, Ti02, Sr and light REE. It displays strong geochemical similarities to the Bimbowrie S-type granite. Consistent geochemical and isotopic characteristics for the Walter Outalpa granite and other similar A-type granites across the Olary Domain indicate a single regional crustal plus mantle source. Partial melting of lower Archaean crust due to lithospheric thinning is proposed. Geochemistry and isotopic analysis of the peraluminous granites suggest varying infracrustal sources for loosely grouped S-type granites in the Olary Domain. Previous interpretations for the depositional environment of the Willyama Supergroup metasediments in a continental rift setting are supported by comagmatic A-type volcanics and granites within the central part of the eastern Weekeroo Inlier. An extensional environment during emplacement is consistent with evidence for shallow level emplacement such as graphic texture, and the absence of a contact aureole for the Walter Outalpa granite. There is foliation development and evidence of folding for three deformation events during the Proterozoic Olarian Orogeny. Timing relationships between granitoids and metasediments in this area have constrained relative timing of emplacement. Low temperature solid state deformation affected the A-type Walter Outalpa granite after emplacement into Willyama Supergroup metasediments. Crosscutting relationships between the peraluminous granite and adjacent deformed metasediments imply a late to post D2 emplacement for this granite.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 1998

This item is only available electronically.
Analysis of granitoids from the Olary Block of South Australia, gave rise to the identification of three genetically different granitoids. The Bimbowrie Granite, characterised by high Al203, CaO, K2O, P205, Rb, Sr, Pb, Zn and low Na20, Nb, Zr, Ga and Y is an S-type granite, considered to be largely a product of partial anatexis and melt segregation from adjacent and underlying migmatitic metasediments during a high grade metamorphic event. The Basso Granodiorite with high Si02, Zr, Nb, Y and LREE and low CaO, Al203, MgO, V, Ba and Sr is a typical A-type granite, that is it formed from remelting of crust from which earlier granites had been extracted, or alternatively from fractionation of basaltic magma. It intrudes the host metasediments and is subsequently intruded by the Bimbowrie Granite. Thirdly, the Antro Tonalite exhibits I-type characteristics with high Fe203, Na20, CaO and Ti02 levels and low LREE and K2O. Rb-Sr dating produced an isochron age of 1642 ± 5 Ma for the Basso Granodiorite and metasedimentary units. The Rb-Sr isotope system is easily reset, and generally registers significantly younger ages. Hence, 1642 ± 5 Ma may reflect the timing of a metamorphic/deformational event. Sm-Nd isotope investigations into the Olary Block revealed a clustering of model ages. The Bimbowrie Granite has DM model ages of 2.6 - 2.67 Ga, recording the age of extraction from the mantle. One sample did however produce an age of 3.28 Ga, reflecting the granite’s source. That is, it may be sampling metasediment derived from older crust, present either as a basal sequence upon which the current stratigraphy is deposited or alternatively it may be sourcing a metasedimentary pile with a greater crustal residence time than the exposed metasediments. DM model age for the metasediment of 2.55 Ga further supports the notion that the Bimbowrie Granite formed as a result of in situ melting of the metasedimentary sequence. 2.12 - 2.13 Ga DM model ages were determined for the Basso Granodiorite. One sample did however have a TDM similar to the S-type granites of 2.61 Ga; this clearly indicates crustal contamination of this sample during emplacement, whereas the other samples reflect true mantle separation ages. Regardless of the exact rates of crustal growth, it is clear that large volumes of continental crust were formed during the Palaeo- Mesoproterozoic. Identification of crustal production peaks for the Australian continent at -3600 Ma, -2600 Ma, -2200 Ma and -1800 Ma by McCulloch (1987), are reinforced by the data obtained herein. Two peaks were established, one at -2600 Ma for the Bimbowrie Granite and the other at -2200 for the Basso Granodiorite. Controversy still remains over whether these periods are discrete growth episodes or simply reflect a variation in the rate of recycling of continental crust into the mantle.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 1994

Figure 5.13 is folded and in plastic pocket inside back cover.
Bibliography: leaves 147-168.
xiv, 184, [14] leaves, [35] leaves of plates : ill. (chiefly col.), maps ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1998