Barium contents of granites: key to understanding crustal architecture in the southern Lachlan Fold Belt?

Rossiter, AG; Gray, C. M.

doi:10.1080/08120090801888586

Cited by 34 publications

(12 citation statements)

References 47 publications

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“…VandenBerg et al 2000) has failed to identify large sinistral strike-slip structures within the western Lachlan Orogen required by the composite terrane lateral-escape model of Glen et al (1992). The sedimentology of the western Melbourne Zone demonstrates strong links with the adjacent Bendigo Zone that began in the Late Ordovician and continued into the Early Devonian, in stark contrast to the model proposed by Rossiter & Gray (2008) which argues that these regions first came into juxtaposition during 'insertion' of the Selwyn Block into the interior of the Lachlan Fold Belt in the Late Silurian.…”

Section: Tectonic Modelsmentioning

confidence: 48%

“…Rossiter & Gray (2008) contend that the lower crust of the Selwyn Block must extend east of the Warby Springs Granite, the Wabonga Volcanic Complex and the Mt Taylor Granite, all of which are Ba-rich. This interpretation is consistent with the seismic data that shows Selwyn Block crust to be more extensive beneath the (south)western Tabberabbera Zone than previously realised.…”

Section: Tabberabbera Zonementioning

confidence: 98%

“…Fergusson et al 1986, and the 'basement terrane' concept of Chappell et al 1988). Variations on the composite crust concept include intraplate escape tectonic models such as that proposed by Glen et al (1992) and Rossiter & Gray (2008) where exotic terranes are juxtaposed across large strike-slip faults within the western Lachlan Orogen. In these model styles, simultaneous multiple subduction zones are not be required to explain the width or variations in structural style across the Lachlan Orogen.…”

Section: Tectonic Modelsmentioning

confidence: 99%

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Crustal architecture of central Victoria: results from the 2006 deep crustal reflection seismic survey

Cayley¹,

Korsch

Moore³

et al. 2011

Australian Journal of Earth Sciences

109

100

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A *400 km long deep crustal reflection seismic survey was acquired in central Victoria, Australia, in 2006. It has provided information on crustal architecture across the western Lachlan Orogen and has greatly added to the understanding of the tectonic evolution. The east-dipping Moyston Fault is confirmed as the suture between the Delamerian and western Lachlan Orogens, and is shown to extend down to the Moho. The Avoca Fault, the boundary between the Stawell and Bendigo Zones, is a west-dipping listric reverse fault that intersects the Moyston Fault at a depth of about 22 km, forming a V-shaped geometry. Both the Stawell and Bendigo Zones can be divided broadly into a lower crustal region of interlayered and imbricated metavolcanic and metasedimentary rocks and an upper crustal region of tightly folded metasedimentary rocks. The Stawell Zone was probably part of a Cambrian accretionary system along the eastern Gondwanaland margin, and mafic rocks may have been partly consumed by Cambrian subduction. Much of the Early Cambrian oceanic crust beneath the Bendigo Zone was not subducted, and is preserved as a crustal-scale imbricate thrust stack. The seismic data have shown that a thin-skinned structural model appears to be valid for much of the Melbourne Zone, whereas the Stawell and Bendigo Zones have a thick-skinned structural style. Internal faults in the Stawell and Bendigo Zones are mostly west-dipping listric faults, which extend from the surface to near the base of the crust. The Heathcote Fault Zone, the boundary between the Bendigo and Melbourne Zones, extends to at least 20 km, and possibly to the Moho. A striking feature in the seismic data is the markedly different seismic character of the mid to lower crust of the Melbourne Zone. The deep seismic reflection data for the Melbourne Zone have revealed a multilayered crustal structure that supports the Selwyn Block model.

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Section: Tectonic Modelsmentioning

confidence: 48%

Section: Tabberabbera Zonementioning

confidence: 98%

Section: Tectonic Modelsmentioning

confidence: 99%

See 1 more Smart Citation

Crustal architecture of central Victoria: results from the 2006 deep crustal reflection seismic survey

Cayley¹,

Korsch

Moore³

et al. 2011

Australian Journal of Earth Sciences

109

100

View full text Add to dashboard Cite

show abstract

“…VandenBerg et al 2000). These granites are geochemically distinctive, with higher Ba contents, lower initial 87 Sr/ 86 Sr ratios and lower oxygen fugacities than the adjacent granites, suggesting a basement more like that in Tasmania (Chappell et al 1988;Gray 1990;Rossiter & Gray 2008). The gold of the Woods Point-Walhalla region was introduced at about this time, after the intrusion of the dykes but before the granites.…”

mentioning

confidence: 94%

Magnetotelluric survey for undercover structural mapping, Central Victoria

Dennis

Moore

Cull

2011

Australian Journal of Earth Sciences

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“…This 'pluton-age' boundary has previously been used to infer a change in basement terrane across the Stawell and Bendigo Zones (Chappell et al 1988) (dashed line in Figure 1). Rossiter & Gray (2008) also suggested that the Selwyn Block underlies, and is more or less coincident with, a central granite superprovince based on Ba contents and granite geochemistry. This inferred underlying Proterozoic/Paleozoic block beneath the Bendigo and Melbourne Zones would be expected to influence the temperature of metamorphism of the overlying turbidites, as it would insulate heat flow from the mantle to the upper crust.…”

Section: Regional Geologymentioning

confidence: 99%

Illite crystallinity and the b-spacing values of white micas and their implications for gold mineralisation in the Lachlan Orogen

Wilson

McKnight

Dugdale

et al. 2009

Australian Journal of Earth Sciences

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Gold mineralisation in the Lachlan Orogen of western Victoria, is generally hosted in turbidites with very low-grade metamorphic assemblages. Metamorphic data from these turbidites are relatively rare because of the fine-grained nature of the pelitic component and lack of suitable assemblages for thermobarometric estimates. In this study, 'illite crystallinity' (Kü bler Index) and b-lattice spacing measurements were carried out on white micas in metapelites, collected from near the inferred western margin of the Selwyn Block, as well as three exploration targets, in an attempt to relate thermal and barometric conditions to mineralisation. Higher-grade (epizone) metamorphic conditions are recorded in sequences west of the Whitelaw Fault and lower-grade (anchizone) metamorphic conditions to the east of the fault. The change from epizonal to anchizonal grade is abrupt, resolved to a distance of a few hundred metres. The b-spacing values change adjacent to the Muckleford Fault. This is due to rocks to the east being exhumed as the edge of the Selwyn Block moved westward during the Middle Devonian Tabberabberan Orogeny at *380 Ma. We propose that the juxtaposition of rocks with contrasting thermal and barometric histories represents expression of the upper crustal location of the western margin of the Selwyn Block at the time of peak deformation, at about 440 Ma, and this crustal structure controlled the distribution of the major quartz-vein-type gold deposits. The Middle Devonian orogenic activity (*380 Ma) was accompanied by the formation of disseminated gold deposits such as Fosterville. This represents a mineralising event that overprints the earlier gold deposits in a corridor at least 50 km wide and to the west of the Whitelaw Fault, that parallels the margin of the Selwyn Block. The correlation between gold assays and 'illite crystallinity' results, from X-ray diffraction and from shortwave infrared-reflectance field-spectroscopy data, were ambiguous. Kübler Indices are not found to be effective in targeting of mineralisation as the values obtained from the alteration and the host-rock assemblages were similar and reflected the ambient P-T conditions at the time of mineralisation.KEY WORDS: b-spacing, cooling history, gold mineralisation, illite crystallinity, Kübler Index, Lachlan Orogen, metamorphism, Victoria, white micas. INTRODUCTIONThe majority of Victorian gold deposits are associated with low-metamorphic-grade turbidites that are overprinted by alteration halos (Dugdale et al. 2009). If these alteration halos are to be used as a vector to potential sites of mineralisation, it is necessary to determine in which direction the alteration or metamorphic overprint is increasing. A quantitative understanding of the P-T history of the metamorphic events preserved in the Lachlan Orogen (Figure 1) (Figure 1).In the current investigation a field-based technique, short-wave infrared reflectance (SWIR), has also been used to characterise the alteration adjacent to two gold prospects. The SWIR technique measures th...

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Barium contents of granites: key to understanding crustal architecture in the southern Lachlan Fold Belt?

Cited by 34 publications

References 47 publications

Crustal architecture of central Victoria: results from the 2006 deep crustal reflection seismic survey

Crustal architecture of central Victoria: results from the 2006 deep crustal reflection seismic survey

Magnetotelluric survey for undercover structural mapping, Central Victoria

Illite crystallinity and the b-spacing values of white micas and their implications for gold mineralisation in the Lachlan Orogen

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