Compositional and textural variation in detrital chrome-spinels from the Murray Basin, southeastern Australia

2005 ◽  
Vol 69 (2) ◽  
pp. 191-204 ◽  
Author(s):  
M. Pownceby
Keyword(s):  
Major Element ◽  
Chrome Spinel ◽  
Processing Conditions ◽  
Minor Components ◽  
Source Areas ◽  
Southeastern Australia ◽  
Alteration Processes ◽  
Broad Variation ◽  
Murray Basin ◽  
Post Deposition

AbstractDetrital chrome-spinels are contaminant grains within heavy-mineral concentrates found in the Murray Basin of southeastern Australia. The presence of even minor levels of chromia in the predominantly ilmenite-rich concentrates downgrades their market value as potential feedstocks for the production of titania pigment.Compositions from a database of close to 5000 chrome-spinel analyses show a broad range in chemistry. The major element components and their ranges (wt.%) are Cr: 3.10–52.06, Al: 0.46–32.50, Fe: 3.50–44.48 and Mg: 0.03–15.79. Minor components include; Ti: 0.01–6.41, Zn: 0.00–23.00 and Mn: 0.00–5.82. The broad variation in composition suggests multiple source areas for the chrome-spinels although detailed textural examination indicates that variation has also been introduced through pre- and post-deposition alteration processes.The Murray Basin chrome-spinel database has the potential to be used in interpreting and predicting the effects of various processing conditions used to separate the chrome-spinels from the ilmenite.

Detrital chrome-spinel grains in heavy-mineral sand deposits from southeast Africa

2006 ◽  
Vol 70 (1) ◽  
pp. 51-64 ◽  
Author(s):  
M. Pownceby ◽  
P. Bourne
Keyword(s):  
Spinel Structure ◽  
Major Element ◽  
Positive Impact ◽  
Market Value ◽  
Heavy Mineral ◽  
Mineral Deposits ◽  
Chrome Spinel ◽  
Minor Components ◽  
Low Intensity ◽  
Strong Trend

AbstractDetrital chrome-spinels are contaminant grains within ilmenite concentrates produced from heavy-mineral deposits along the coast of southeast Africa. The presence of even minor levels of chromia in the predominantly ilmenite-rich concentrates, downgrades their market value as potential feedstocks for the production of titania pigment. An understanding of their composition can assist in their removal from the ilmenite concentrates.Compositions from a database of close to 900 chrome-spinel analyses shows the major element components and their ranges (in wt.%) are: Cr: 0.4-45.3, Al: 0.0-31.0, Fe: 8.5-69.6 and Mg: 0.0-12.2. Minor components include Ti: 0.1-11.4 and Zn: 0.0-13.7.The chrome-spinel data fall into two compositionally distinct groups. The first group of spinels is dominated by a strong trend reflecting the mutual substitution between Al3+ and Cr3+ in the spinel structure. The second group of spinels is characterized by compositions containing abundant Fe3O4 magnetite component. The clear division between chrome-spinel compositional types indicates the grains are derived from at least two chemically dissimilar provenances.The compositional differences between the chrome-spinel groups has a positive impact on subsequent ilmenite upgrading treatments as the spinels which contain the highest magnetite component are easily removed via low-intensity magnetic separation procedures.

Hydroxylian pseudorutile derived from picroilmenite in the Murray Basin, southeastern Australia

2003 ◽  
Vol 67 (4) ◽  
pp. 733-747 ◽  
Author(s):  
I. E. Grey ◽  
C. Li
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Chemical Weathering ◽  
Composition Range ◽  
Mineral Deposits ◽  
Molecular Water ◽  
Southeastern Australia ◽  
Murray Basin ◽  
Weakly Magnetic ◽  
Scanning Electron

AbstractIlmenite concentrates obtained from heavy mineral deposits in the Murray Basin, southeastern Australia contain appreciable quantities (up to 10 wt.%) of an unusual hydrated Fe titanate mineral in the form of orange to red coloured translucent grains. The grains are weakly magnetic and have a low apparent density (<3.3 g cm–3) due to microprosity, which enables them to be easily concentrated in a pure state. Samples from different deposits have similar analyses of 67–69% TiO2, 8 –9% Fe2O3, 2–3% FeO, 11 –12% H2O and 8 –9% of intra-pore impurities, mainly SiO2 and Al2O3. The powder pattern for the mineral closely matches that for pseudorutile; having a hexagonal subcell with a = 2.844 (1) Å, c = 4.575 (1) Å. The idealized composition range of the Fe titanate, calculated from analyses and structure refinements, is [FeTi6O12(OH)3].3H2O to [FeTi6O11(OH)5].2H2O. The molecular water is nonstructural, probably adsorbed on the surfaces of nano-scale domains of the mineral. Electron microprobe and scanning electron microscopy studies provide evidence for formation of the mineral by replacement reactions acting on MgO-rich ferrian ilmenite grains. The mineral represents a distinct intermediate in the chemical weathering of ilmenite, having a pseudorutile-like structure but a leucoxene-like composition. It is unusual in not having undergone any recrystallization to phases such as rutile and anatase.

Holocene lake salinity changes in the Wimmera, southeastern Australia, provide evidence for millennial-scale climate variability

2012 ◽  
Vol 77 (1) ◽  
pp. 65-76 ◽  
Author(s):  
Justine Kemp ◽  
Lynda C. Radke ◽  
Jon Olley ◽  
Steve Juggins ◽  
Patrick De Deckker
Keyword(s):  
Brine Shrimp ◽  
Optically Stimulated Luminescence ◽  
Weighted Averaging ◽  
Faecal Pellets ◽  
Low Salinity ◽  
Salinity Changes ◽  
Southeastern Australia ◽  
Wind Circulation ◽  
Murray Basin ◽  
Lake Salinity

Palaeosalinity records for groundwater-influenced lakes in the southwest Murray Basin were constructed from an ostracod-based, weighted-averaging transfer function, supplemented with evidence from Campylodiscus clypeus (diatom), charophyte oogonia, Coxiella striata (gastropod), Elphidium sp. (foraminifera), Daphniopsis sp. ephippia (Cladocera), and brine shrimp (Parartemia zietziana) faecal pellets, the δ18O of ostracods, and > 130 μm quartz sand counts. The chronology is based on optically stimulated luminescence and calibrated radiocarbon ages. Relatively wet conditions are marked by lower salinities between 9600 yr and 5700 yr ago, but mutually exclusive high- and low-salinity ostracod communities suggest substantial variability in effective precipitation in the early Holocene. A drier climate was firmly in place by 4500 yr and is marked at the groundwater-dominated NW Jacka Lake by an increase in aeolian quartz and at Jacka Lake, by a switch from surface-water to groundwater dominance. Short-lived, low-salinity events at 8800, 7200, 5900, 4800, 2400, 1300 and 400 yr are similar in timing and number to those recorded on Australia's southern continental shelf, and globally, and provide evidence for the existence of the ~ 1500-yr cycle in mainland southern Australia. We surmise that these are cool events associated with periodic equatorward shifts in the westerly wind circulation.

scholarly journals The Role of 36Cl and 14C Measurements in Australian Groundwater Studies

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 877-883 ◽  
Author(s):  
J R Bird ◽  
G E Calf ◽  
R F Davie ◽  
L K Fifield ◽  
T R Ophel ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Radioactive Decay ◽  
Stable Isotope Ratios ◽  
Tandem Accelerator ◽  
Southeastern Australia ◽  
Groundwater Samples ◽  
National University ◽  
Mass Spectrometry System ◽  
Murray Basin

An Accelerator Mass Spectrometry system has been developed using the 14UD tandem accelerator at the Australian National University. It has been used for 36Cl measurements on groundwater samples from the Murray Basin in southeastern Australia. Measurements of 14C have also been made on the same groundwaters. The information can be combined with stable isotope ratios and other data to illustrate the occurrence of processes such as radioactive decay and local recharge in different aquifers.

Sign in / Sign up

Export Citation Format

Share Document