Structural and metamorphic controls on the distribution of zircon in an evolving quartzofeldspathic migmatite: an example from the Reynolds Range, central Australia

Dirks, Paul H.G.M.; Hand, Martin

doi:10.1111/j.1525-1314.1991.tb00514.x

Cited by 23 publications

(12 citation statements)

References 18 publications

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“…The formation of new zircon, in the form of overgrowths and small euhedral crystals, occurred in partial melts, pegmatites, shear zones and metasomatic zones in this part of the Arunta Block at c. 1588-1580Ma (Dirks & Hand, 1991;Collins & Williams, 1995;this study). Although the new zircon growth was enhanced in the presence of fluids, it is minor; inheritance typifies the zircon data (Dirks & Hand, 1991;Collins & Williams, 1995;this study). The zircons in the Lander Rock beds generally reflect a detrital origin and most show little departure from concordia.…”

Section: N T E R Pr Etat I 0 Nmentioning

confidence: 80%

“…Two mid-Proterozoic tectono-metamorphic cycles (Ml-D1 and M2-D2) affected rocks in the region Dirks & Wilson, 1990;Vernon et al, 1990;Clarke & Powell, 1991;Dirks et al, 1991;Hand et al, 1992). The first cycle (Ml-D1) affected the Lander Rock beds prior to the intrusion of c. 1820 Ma megacrystic granitoids.…”

Section: Geological Settingmentioning

confidence: 99%

“…Comparable early sillimanite fabrics occur in cordier-ites and garnets from many high-grade parts of the Reynolds Range -Anmatjira Range region, and have been attributed to deformation that occurred early during M2-D2 (e.g. Dirks et al, 1991, their fig. 8d; .…”

Section: High-grade Lander Rock Beds Sample X-524mentioning

confidence: 99%

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SHRIMP II dating of zircons and monazites: reassessing the timing of high‐grade metamorphism and fluid flow in the Reynolds Range, northern Arunta Block, Australia

Vry¹,

Compston

Cartwright

1996

Journal Metamorphic Geology

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Key insights into the timing of tectonometamorphic events in a complex high-grade metamorphic terrane can be obtained by combining results from SHRIMP I1 ion microprobe studies of individual monazite grains with SHRIMP I1 studies and scanning electron microscope (SEM)-based cathodoluminescence (CL) imaging of zircons. Results from the Reynolds Range region, Arunta Block, Northern Territory, Australia, show that the final episode of regional metamorphism to high-T and low-P granulite facies conditions is most likely to have occurred at c. 1580 Ma, not at 1785-1775 Ma, as previously accepted. The previous interpretation was based on zircon studies of structurally controlled granitoids, without SEM-based CL imaging. Monazites in a 1806 & 6 Ma megacrystic granitoid preserve rare cores that are interpreted to be inherited magmatic monazite, but record no evidence of another high-T event prior to 1580 Ma. Most monazites from the region record only a single high-T metamorphic event at c. 1580 Ma. Zircon inheritance is very common. Zircons or narrow overgrowths of zircon dated at c. 1580 Ma have only been found in two types of rocks: rocks produced by metasomatic fluid flow at high temperatures (2 750 "C), and rocks that have undergone local partial melting. Previous explanations that attributed these 1580 Ma zircon ages to widespread hydrothermal fluid fluxing associated with post-tectonic pegmatite emplacement at amphibolite facies conditions are not supported by the available evidence including oxygen isotope data.The observed high regional metamorphic temperatures require the involvement of advective heating. However, contrary to a previous tectonic model for the formation of this and other low-P, high-T metamorphic belts, the granites that are exposed at the present structural level do not appear to be the source of that heat, unless some of the granites were emplaced at c. 1580 Ma.

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Section: N T E R Pr Etat I 0 Nmentioning

confidence: 80%

Section: Geological Settingmentioning

confidence: 99%

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SHRIMP II dating of zircons and monazites: reassessing the timing of high‐grade metamorphism and fluid flow in the Reynolds Range, northern Arunta Block, Australia

Vry¹,

Compston

Cartwright

1996

Journal Metamorphic Geology

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“…Opinions also vary on the nature and sequence of the structural and metamorphic events (Collins & Shaw, 1995, Table 2). In this paper we use the structural terminology of , which relates most closely to that of Dirks & Wilson (1990) and Dirks et al (1991).…”

Section: The Reynolds Range and I T S Regional Contextmentioning

confidence: 99%

An extended episode of early Mesoproterozoic metamorphic fluid flow in the Reynolds Range, central Australia*

Williams

Buick

Cartwright

1996

Journal Metamorphic Geology

503

221

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A B S T R A C TThe products of metamorphic fluid flow are preserved in zones within the marbles and metamorphosed semipelites of the Upper Calcsilicate Unit in the granulite portion of the Late Palaeoproterozoic Reynolds Range Group, northern Arunta Block, central Australia. The zones of retrogression, characterized by minerals such as wollastonite, grossular and clinohumite, local resetting of oxygen isotopic compositions and local major element metasomatism, were channelways for water-rich fluids derived from granulite facies metapelites. U-Th-Pb isotopic ages measured by the SHRIMP ion microprobe on zircon and monazite from a granulite facies semipelite, an early semiconcordant aluminous quartz-rich fluid-flow segregation and a late discordant quartz-rich segregation record some of the extended thermal history of the area. Zircon cores from the semipelite show its likely protolith to be an igneous rock 1812+ 11 Ma old, itself derived from a source containing zircon as old as 2.2 Ga. Low-Th/U overgrowths on the zircon grew during granulite facies metamorphism at 1594 k 6 Ma. Monazite cooled to its blocking temperature at 1576 8 Ma. Zircon cores from the semiconcordant segregation are dominantly > 2.3 Ga old, indicating that the source of the fluids was not the particular metamorphosed semipelite studied. Two generations of low-Th/U overgrowths on the zircon give indistinguishable ages for the older and younger of 1589f8 and 1582+8 Ma, respectively. The monazite age is the same, 1576-t 12 Ma. Zircon from the late discordant segregation gave 1568 + 4 Ma. Fluid flow occurred for at least 18 3 ( 0 ) Ma and ended 26+3 ( 0 ) Ma after the peak of metamorphism, suggesting a very slow cooling rate of z 3 'C Ma-'. The last regional high-grade metamorphism in the Reynolds Range occurred at 1.6 Ga, not z 1.78 Ga as previously thought. The high-grade event at % 1.78 Ga is a separate event that affected only the basement to the Reynolds Range Group.

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“…Argentina, Sierra Pampeana (Rapela et al 2002). Australia, Reynolds Range (Dirks & Hand 1991). Australia, Mt Stafford (Greenfield et al 1996).…”

Section: Modelling Melt Transport Through a Feeder Zonementioning

confidence: 99%

Modelling mid-crustal migmatite terrains as feeder zones for granite plutons: the competing dynamics of melt transfer by bulk versus porous flow

Olsen

Marsh

Baumgartner

2004

Earth and Environmental Science Transactions of the Royal Socie

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The common association of mid-crustal migmatites with an upper-level granite pluton could indicate that the migmatites are a feeder zone for the pluton. If magma from a deeper level pervasively intrudes a high temperature metamorphic complex, most of the intruded magma would not freeze because of the prevailing temperature. The interaction between the magma and country rocks, which could include partial melting and crystallisation of the magma passing through, would modify magma to a more granitic composition, as found in the higher-level pluton.The physical aspect of the magma transport through such a hot feeder zone is modelled by introducing a dimensionless melt transport (MT) number, which is the ratio of the rate of melt movement caused by the bulk flow of the entire mass (melt+solid) to that of porous media flow of melt only through the solid framework. The MT number is strongly dependent on the melt content of the melt-rich zone (MRZ), the diameter of the MRZ and typical particle size in the MRZ.The w300-Ma, diatexitic, Lauterbrunnen migmatites (LM) in the Aar massif, Swiss Alps, may be such a feeder zone for the nearby 303-Ma Gastern granite (GG). The chemical and field evidence indicates that the LM formed by an intrusion of intermediate composition magma, which interacted with country rocks to produce a magma of GG composition.

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Structural and metamorphic controls on the distribution of zircon in an evolving quartzofeldspathic migmatite: an example from the Reynolds Range, central Australia

Cited by 23 publications

References 18 publications

SHRIMP II dating of zircons and monazites: reassessing the timing of high‐grade metamorphism and fluid flow in the Reynolds Range, northern Arunta Block, Australia

SHRIMP II dating of zircons and monazites: reassessing the timing of high‐grade metamorphism and fluid flow in the Reynolds Range, northern Arunta Block, Australia

An extended episode of early Mesoproterozoic metamorphic fluid flow in the Reynolds Range, central Australia*

Modelling mid-crustal migmatite terrains as feeder zones for granite plutons: the competing dynamics of melt transfer by bulk versus porous flow

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