Xenolith geotherms and crustal models in Eastern Australia

Cull, J. P.; O’Reilly, Suzanne Y.; Griffin, William L.

doi:10.1016/0040-1951(91)90109-6

Cited by 53 publications

(22 citation statements)

References 22 publications

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“…They may also result from existing thick piles of Ordovician mafic rocks present in the mid and lower crust . As proposed in previous studies (O 'Reilly 1989;Cull et al 1991;McDonough et al 1991) based on heat-flow models and the predominant mafic lower crustal rock types identified in xenoliths, magmatic and tectonic underplating has been a significant mechanism in the crustal growth. Finlayson et al (2002) and Glen et al (2002) also suggested from a seismic refraction profile the presence of an Azimuth is the direction of the fast axis ( ); Pl, plunge of the fast axis.…”

Section: Thickness (Km)mentioning

confidence: 61%

Crustal complexity in the Lachlan Orogen revealed from teleseismic receiver functions

Fontaine¹,

Tkalčić²

2013

Australian Journal of Earth Sciences

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There is an ongoing debate about the tectonic evolution of southeast Australia, particularly about the causes and nature of its accretion to a much older Precambrian core to the west. Seismic imaging of the crust can provide useful clues to address this issue. Seismic tomography imaging is a powerful tool often employed to map elastic properties of the Earth's lithosphere, but in most cases does not constrain well the depth of discontinuities such as the Mohorovi ci c (Moho). In this study, an alternative imaging technique known as receiver function (RF) has been employed for seismic stations near Canberra in the Lachlan Orogen to investigate: (i) the shear-wave-velocity profile in the crust and uppermost mantle, (ii) variations in the Moho depth beneath the Lachlan Orogen, and (iii) the nature of the transition between the crust and mantle. A number of styles of RF analyses were conducted: H-K stacking to obtain the best compressional-shear velocity (V P /V S ) ratio and crustal thickness; nonlinear inversion for the shear-wave-velocity structure and inversion of the observed variations in RFs with backazimuth to investigate potential dipping of the crustal layers and anisotropy. The thick crust (up to 48 km) and the mostly intermediate nature of the crustÀmantle transition in the Lachlan Orogen could be due to the presence of underplating at the base of the crust, and possibly to the existing thick piles of Ordovician mafic rocks present in the mid and lower crust. Results from numerical modelling of RFs at three seismic stations (CAN, CNB and YNG) suggest that the observed variations with back-azimuth could be related to a complex structure beneath these stations with the likelihood of both a dipping Moho and crustal anisotropy. Our analysis reveals crustal thickening to the west beneath CAN station which could be due to slab convergence. The crustal thickening may also be related to the broad Macquarie volcanic arc, which is rooted to the Moho. The crustal anisotropy may arise from a strong N-S structural trend in the eastern Lachlan Orogen and to the preferred crystallographic orientation of seismically anisotropic minerals in the lower and middle crust related to the paleo-Pacific plate convergence.

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Section: Thickness (Km)mentioning

confidence: 61%

Crustal complexity in the Lachlan Orogen revealed from teleseismic receiver functions

Fontaine¹,

Tkalčić²

2013

Australian Journal of Earth Sciences

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“…This event correlates with rifting along the eastern margin and with thermochronologic apatite fission track ages with long mean tracks located east of the Great Escarpment [ Rahmanian et al , ; Lowry and Longley , ; Gleadow et al , ]. The closing temperature for apatite fission tracks is 110±10°C, which corresponds to a minimum depth range of 1.8–2.2 km, based on a geothermal gradient calculated from mantle xenoliths [ Kohn et al , ; Cull et al , ]. Thus, fission track data should be insensitive to formation of the <1 km Great Escarpment.…”

Section: Discussionmentioning

confidence: 99%

Spatial and temporal patterns of Australian dynamic topography from River Profile Modeling

Czarnota

Roberts

White

et al. 2014

J. Geophys. Res. Solid Earth

128

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Despite its importance, the temporal and spatial evolution of continental dynamic topography is poorly known. Australia's isolation from active plate boundaries and its rapid northward motion within a hot spot reference frame make it a useful place to investigate the interplay between mantle convection, topography, and drainage. Offshore, dynamic topography is relatively well constrained and can be accounted for by Australia's translation over the mantle's convective circulation. To build a database of onshore constraints, we have analyzed an inventory of longitudinal river profiles, which is sensitive to uplift rate history. Using independently constrained erosional parameters, we determine uplift rates by minimizing the misfit between observed and calculated river profiles. Resultant fits are excellent and calculated uplift histories match independent geologic constraints. We infer that western and central Australia underwent regional uplift during the last 50 Myr and that the Eastern Highlands have been uplifted in two stages. The first stage from 120 to 80 Ma, coincided with rifting along the eastern margin and its existence is supported by thermochronological measurements. A second stage occurred at 80–10 Ma, formed the Great Escarpment, and coincided with Cenozoic volcanism. The relationship between topography, gravity anomalies, and shear wave tomographic models suggest that regional elevation is supported by temperature anomalies within the lithosphere's thermal boundary layer. Morphology and stratigraphy of the Eastern Highlands imply that these anomalies have been coupled to the base of the plate during Australia's northward motion over the last 70 Myr.

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“…Several workers (Sass & Lachenbruch 1979; O'Reilly & Griffin 1985; Cull et al 1991) noted that the xenolith‐derived geothermal gradients, having high temperature at shallow depths compared with the model conductive geotherms, can be modeled on the basis of the heat transferring by the cooling of basaltic melts intruded at the crust‐mantle transition zone. It is a probable cause for the elevated geotherm of Jeju Island.…”

Section: Discussionmentioning

confidence: 99%

Geothermal gradient of the upper mantle beneath Jeju Island, Korea: Evidence from mantle xenoliths

2001

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Ultramafic xenoliths found in alkali basalts from Jeju Island, Korea are mostly spinel lherzolites accompanied by subordinate amount of spinel harzburgites and pyroxenites. The combination of results from a two-pyroxene geothermometer and Ca-inolivine geobarometer yields temperature-pressure (T-P) estimates for spinel peridotites that fall in experimentally determined spinel lherzolite field in CaO-Fe-MgO-Al 2 O 3 -SiO 2 -Cr 2 O 3 (CFMASCr) system. These T-P data sets have been used to construct the Quaternary Jeju Island geotherm, which defines a locus from about 13 kbar at 880°C to 26 kbar at 1040°C. The geothermal gradient of Jeju Island is greater than that of the conventional conductive models, and may be as a result of a thermal perturbation by the heat input into the lithospheric mantle via the passage and emplacement of magma. Spinel-lherzolite is the main constituent rock-type of the lithospheric mantle beneath Jeju Island. Pyroxenites may be intercalated in peridotites at similar depth and temperature as re-equilibrated veins or lenses.

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Xenolith geotherms and crustal models in Eastern Australia

Cited by 53 publications

References 22 publications

Crustal complexity in the Lachlan Orogen revealed from teleseismic receiver functions

Crustal complexity in the Lachlan Orogen revealed from teleseismic receiver functions

Spatial and temporal patterns of Australian dynamic topography from River Profile Modeling

Geothermal gradient of the upper mantle beneath Jeju Island, Korea: Evidence from mantle xenoliths

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