The McKinnons gold mine, ∼35 km southwest of Cobar in New South Wales is a non-operational opencut mine with extensive regolith profile development down to a depth of ∼80 m. Twenty-three oriented paleomagnetic samples, from saprolite at different levels through the profile, yielded two well-defined paleomagnetic poles, one of Paleocene age (60 ± 10 Ma), and the other of Miocene age (15 ± 4 Ma). These reflect two periods of remagnetisation associated with deep, intense, oxidative weathering under humid conditions. They provide important time constraints for the history of climate change, weathering and landscape evolution of the Cobar region.

Saprolite

Regolith

Denudation

10.1080/08120090802547033

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Citations (14)

Landscape and regolith features related to Miocene leucitite lava flows, El Capitan northeast of Cobar, New South Wales

Australian Journal of Earth Sciences (2006)

Ken McQueen Ochoa González Ian C. Roach Brad Pillans W. J. Dunlap

Outcrops of leucitite lavas occur as scattered remnants up to 40 m thick in the El Capitan area, northeast of Cobar in western New South Wales. Two eruption sites have been located for these lavas. Preserved volcanic features indicate that the lavas were erupted on to a relatively low-relief, Early Miocene land surface, flowed along a shallow valley and underwent inflation. Geochemical analyses of the leucitites indicate only limited fractionation. Remnant outcrops of the leucitite lavas represent a very important time marker in the geomorphic history of the Cobar region, preserving evidence of both Early Miocene and post-Early Miocene landscape evolution and weathering conditions. A deep-weathering profile, similar to those common throughout the region and characterised by a ferruginous mottled zone and underlying bleached saprolite, is preserved beneath a dissected flow at one eruption site. Other deposits beneath the leucitite flows include baked soils, silcretes, and quartz-rich gravels and grits. Palaeomagnetic dating of the upper part of the deep-weathering profile indicates an Early to Middle Miocene age for hematite fixation. A new 40Ar/39Ar age on the volcanic plug at this site (17.14 ± 0.20 Ma, 2σ) refines the minimum eruption age for the leucitites and supports an Early Miocene age for ferruginisation of the deep-weathering profile. Topographic inversion of the basal contact of one of the leucitite flows indicates an average minimium erosion rate for the area of 1 m per million years. Weathering profiles on the leucitites are thin and lack significant ferruginisation or chemical leaching, indicating that post-Early Miocene weathering in the region has been very limited. These profiles also contain a significant aeolian component including abundant quartz dust.

Outcrop

10.1080/08120090600923311

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Citations (15)

Spinel phases associated with metamorphosed volcanic-type iron-nickel sulfide ores from Western Australia

Economic Geology (1977)

David I. Groves F. M. Barrett R. A. Binns Ken McQueen

Previous interpretations of spinels in Archean Fe-Ni sulfide ores from Western Australia must be revised in view of widespread metamorphic effects. When these effects are isolated, however, the spinels remain useful genetic indicators.Modified igneous chromites occur in the metamorphosed ultramafic host rocks but show no tendency toward gravity-induced basal accumulation. They may be distinguished from chromites of metasomatic origin in contact reaction zones and from Cr-bearing magnetites produced during serpentinization. Ragged magnetites also attributed to serpentinization reactions occur in disseminated and matrix ores. In addition, the ores contain large subhedral ferrochromites and more euhedral magnetites which appear to be relict crystallization products of sulfide-oxide melts; their presence provides supporting evidence for an initially magmatic origin of the ores. Despite changes in their distribution during deformation, some gravitational concentration of the ferrochromites within ore is apparent; this concentration is incompatible with a single-stage magmatic model.Both the lithophile and chalcophile chromites in mineralized ultramafic rocks are unusually rich in zinc, a feature apparently inherited from the magmatic stage, and one which may be useful in exploration.

Nickel sulfide

10.2113/gsecongeo.72.7.1224

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Citations (68)

Zircon dating of Devonian‐Carboniferous rocks from the Bombala area, New South Wales

Australian Journal of Earth Sciences (2000)

Keith Sircombe Ken McQueen

Zircons from two igneous and two sedimentary units in the Bombala area of southeastern New South Wales have been examined by the sensitive high resolution ion microprobe (SHRIMP) to establish a timeframe in which to interpret these rocks. Previous studies have correlated these rocks with Late Devonian units of the south coast, solely upon the basis of stratigraphy and lithology as palaeontological evidence was absent. The two igneous units are the Hospital Porphyry and Paradise Porphyry occurring beneath the sedimentary units. Both give a Frasnian age that can be correlated with the Boyd Volcanic Complex. The sedimentary samples are from the basal and upper sections of the Rosemeath Formation, a fluvial ‘redbed’ consisting of conglomerate, coarse sandstone, and associated red siltstone and mudstone. Detrital zircons from the basal conglomeratic section at Kilbrechin indicate a dominant provenance from local Silurian granites and volcanics and a maximum depositional age that can be correlated with the Frasnian‐Famennian Merrimbula Group. However, detrital zircons from the upper coarse sandstone section of the Rosemeath Formation at Endeavour Lookout challenge the positive correlation trend with a lack of Silurian‐age grains and a presence of grains ranging from Late Devonian to Early Carboniferous in age. These results imply either that the south coast correlation is not valid for the upper sequences, or that the Merrimbula Group sequences also extend upward into the Carboniferous. The general coarseness of the Rosemeath Formation also suggests a relatively local provenance. No Early Carboniferous source is known in the immediate vicinity suggesting that Early Carboniferous igneous activity in this region of the Lachlan Orogen may have been more extensive than is currently realised. Keywords: CarboniferousDevoniangeochronologySHRIMPzircon dating

Devonian

Late Devonian extinction

Siltstone

Lithology

Conglomerate

Paleocurrent

Geochronology

10.1046/j.1440-0952.2000.00830.x

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Citations (7)

The nature and distribution of regolith carbonate accumulations in southeastern Australia and their potential as a sampling medium in geochemical exploration

Journal of Geochemical Exploration (1999)

Ken McQueen S. M. Hill Katharine Foster

Regolith

10.1016/s0375-6742(99)00071-0

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Citations (43)