B1 subdivisions in thin komatiites at Kambalda, Western Australia

1989 ◽  
Vol 126 (3) ◽  
pp. 263-270 ◽  
Author(s):  
B. Thomson
Keyword(s):  
Western Australia ◽  
Late Stage ◽  
Lateral Position ◽  
Total Thickness ◽  
Olivine Cumulates ◽  
High Degree ◽  
Peripheral Regions

AbstractB1 subdivisions are narrow foliated zones of stubby, skeletal olivine blades, situated at the top of the granular olivine cumulates (B2) in ponded komatiite lavas. They developed at a late stage in pond crystallization as a result of compaction-related circulation of intercumulus liquids through and along the top of the cumulates. The total thickness of a B1 and its degree of blade parallelism are related to lateral position within ponded lavas. The deeper, hotter and longer-lived core regions generated a thick B1 with a high degree of blade parallelism (ordered B1), whereas the shallower, peripheral regions produced a narrow B1 with a poor degree of blade parallelism (disordered B1), or failed to develop one at all.

The geochemistry of loveringite, a uranium-rare-earth-bearing accessory phase from the Jimberlana Intrusion of Western Australia

1978 ◽  
Vol 42 (322) ◽  
pp. 187-193 ◽  
Author(s):  
I. H. Campbell ◽  
P. R. Kelly
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Western Australia ◽  
Late Stage ◽  
The Other ◽  
Cr Content ◽  
Accessory Phase ◽  
Olivine Cumulates ◽  
Strong Depletion

SummaryThe distribution and geochemistry of loveringite, an accessory Ti, Fe±Cr oxide containing U and rare-earth elements (Ln) from the Jimberlana Intrusion, have been studied. Loveringite is most abundant in bronzite cumulates; it is found in trace amounts in early plagioclase-augite-hypersthene cumulates, but is not found in the olivine cumulates or in the late-stage differentiates. Loveringites from the bronzite cumulates have a high Cr content compared with those from the plagioclase-augite-hypersthene cumulates, suggesting that the mineral is stabilized by the presence of Cr in the intercumulus liquid. The Ln pattern shows a strong depletion trend from La to Eu, a sharp reversal between Eu and Tb and a second depletion pattern from Tb to Lu. This pattern suggests that the Ln are substituting into two sites, one much larger than the other.

Turbulent mixing and mesoscale distributions of late-stage fish larvae on the NW Shelf of Western Australia

2006 ◽  
Vol 15 (1) ◽  
pp. 44-59 ◽  
Author(s):  
M. G. MEEKAN ◽  
J. H. CARLETON ◽  
C. R. STEINBERG ◽  
A. D. MCKINNON ◽  
R. BRINKMAN ◽  
...  
Keyword(s):  
Western Australia ◽  
Turbulent Mixing ◽  
Late Stage ◽  
Fish Larvae

scholarly journals A Relation Between Snow Cover, Cirrus Cloud, and Freezing Nuclei in the Atmosphere

1956 ◽  
Vol 9 (4) ◽  
pp. 545 ◽  
Author(s):  
EG Bowen
Keyword(s):  
Snow Cover ◽  
Western Australia ◽  
Cirrus Cloud ◽  
Nucleus Concentration ◽  
High Degree ◽  
Calendar Dates

It is reasonable to suppose that observations like that of cirrus cloud in the upper air and heavy falls of snow in relatively warm latitudes correspond to the presence of a large number of freezing nuclei in the atmosphere. A 300-year record of snow covering the ground at Tokyo and a 10-year record of cirrus cloud in Western Australia are examined and compared with one year's measurement of freezing nucleus concentration. The curves show a high degree of correlation, and all three tend to maximize on certain calendar dates.

U-Pb and Sm-Nd Evidence for Episodic Orogenic Gold Mineralization in the Kalgoorlie Gold Camp, Yilgarn Craton, Western Australia

2021 ◽  
Author(s):  
Jordan A. McDivitt ◽  
Steffen G. Hagemann ◽  
Anthony I.S. Kemp ◽  
Nicolas Thébaud ◽  
Christopher M. Fisher ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Western Australia ◽  
Late Stage ◽  
Gold Mineralization ◽  
Hydrothermal Systems ◽  
Orogenic Gold ◽  
Yilgarn Craton ◽  
Gold Telluride ◽  
Icp Ms ◽  
Metamorphic Fluids

Abstract Different genetic and timing models for gold mineralization in the Kalgoorlie gold camp (Yilgarn craton, Western Australia) suggest either broadly synchronous, late-stage mineralization related to metamorphic fluids at ca. 2640 Ma or a punctuated mineralization history from ca. 2675 to 2640 Ma with the involvement of early magmatic-hydrothermal systems (represented by the Fimiston, Hidden Secret, and Oroya gold-telluride lodes) and late metamorphic fluids (represented by the Mt. Charlotte gold stockwork veins). The results of U-Pb and Sm-Nd geochronological studies of zircon, apatite, and titanite from pre-ore dikes and syn-ore dikes constrain the absolute timing of mineralization and provide new evidence to this timing controversy. Emplacement ages constrained by U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon data are interpreted to be similar for both the pre-ore dikes (n = 10) and syn-ore dikes (n = 7) at ca. 2675 Ma. An inferred emplacement age of ca. 2675 Ma for the syn-ore dikes is supported by a Sm-Nd isochron age from apatite (laser ablation-inductively coupled plasma-mass spectrometry; LA-ICP-MS) of 2678 ± 15 Ma and by a U-Pb titanite age (LA-ICP-MS) of 2679 ± 6 Ma. The results of chemical abrasion-isotope dilution-thermal ionization mass spectrometry U-Pb zircon analysis from the pre- and syn-ore dikes are complicated by multistage Pb loss, reverse discordance, and potential inheritance. However, the data are compatible with the emplacement of Fimiston/Hidden Secret gold mineralization at ca. 2675 Ma and suggest a younger age for Oroya mineralization at ca. 2665 Ma. These results contrast with models for orogenic gold deposits that invoke broadly synchronous, late-stage mineralization related to metamorphic fluids at ca. 2640 Ma. The bulk of the Kalgoorlie gold camp’s estimated 2,300 t Au endowment was emplaced at ca. 2675 Ma as Fimiston/Hidden Secret Au mineralization. This early Au mineralization was deformed and overprinted twice by subordinate Au mineralization at ca. 2665 (Oroya mineralization) and ca. 2640 Ma (Mt. Charlotte mineralization). Gold mineralization in the Kalgoorlie gold camp was protracted in nature from ca. 2675 to 2640 Ma and reflects the interplay of early magmatic (Fimiston, Hidden Secret, Oroya) and late metamorphic (Mt. Charlotte) hydrothermal fluid systems in the formation of hybrid intrusion-related and metamorphic orebodies.

Petrology and stratigraphy of some texturally well preserved thin komatiites from Kambalda, Western Australia

1989 ◽  
Vol 126 (3) ◽  
pp. 249-261 ◽  
Author(s):  
B. Thomson
Keyword(s):  
Heat Loss ◽  
Western Australia ◽  
Lateral Position ◽  
Flow Profile ◽  
Western Margin ◽  
Lateral Margins ◽  
Greenstone Belts ◽  
Temporal And Spatial ◽  
Geochemical Profiles ◽  
Facies Types

AbstractArchaean komatiite volcanics at Kambalda, Western Australia have been metamorphosed to upper greenschist–lower amphibolite grade and have experienced intense though heterogeneously developed polyphase deformation. Despite this, preservation of igneous textural features is often good, particularly in areas which underwent only ‘static style’ metamorphism. Thin lavas from the Tripod Hill Member of the Kambalda Komatiite Formation over the western margin of the Hunt nickel shoot display textural elements and facies variations which are virtually identical to those found in fresher thin komatiite sequences in other Archaean greenstone belts. Four principal flow profile (facies) types are defined, comprising nine subtypes. These represent stages in a facies continuum, ranging from ‘mature’ profiles which comprise thick spinifex textured tops and close packed cumulate bases through to massive, jointed ‘immature’ profiles devoid of mesoscopic spinifex texture. The causes of textural diversity within and between profiles are many and complex. However, facies variations can be attributed mainly to the effects of lava velocity at the time of major heat loss, combined with relative lateral position within any flow. The most mature textural (and geochemical) profiles developed in parts of lavas which had become ponded prior to major heat loss, whereas the least evolved profiles developed along the lateral margins (levees) of moving lavas. The study area komatiites occur as alternating stacks of flows of similar type. This stratigraphy records temporal and spatial shifts in the locus of lava ponding over the western margin of the Hunt nickel shoot. Such shifts may have been caused by irregularities in the underlying volcanic topography and/or by synvolcanic faulting and subsidence.

scholarly journals Comparison of Decidual Vasculopathy in Central and Peripheral Regions of Placenta with Implication of Lateral Growth and Spiral Artery Remodeling

2020 ◽  
Vol 1 (3) ◽  
pp. 158-168
Author(s):  
Peilin Zhang
Keyword(s):  
Late Stage ◽  
Late Gestation ◽  
Central Portion ◽  
Lateral Growth ◽  
Spiral Artery ◽  
Peripheral Portion ◽  
Vascular Regeneration ◽  
Artery Remodeling ◽  
Morphologic Changes ◽  
Peripheral Regions

Decidual vasculopathy at late gestation was shown to be associated with spiral artery remodeling at implantation. Dramatic decidual vascular transformation from early to late stage pregnancy suggests a dynamic spatiotemporal relationship between the various vascular components in spiral artery remodeling and decidual vasculopathy. The central and peripheral portions of 105 placentas with decidual vasculopathy at term were examined with or without preeclampsia to see if temporal vascular regeneration was present. Central and peripheral vasculopathy and central and peripheral regeneration were compared. The peripheral portion showed more decidual vasculopathy (88 of total 105, 83.8%) than central portion (72 of total 105, 68.6%, p < 0.0001). However, central portion showed more vascular regeneration (51 of total 105, 48.6%) than the peripheral portion (23 of total 105, 21.9%, p < 0.0001). There was no difference in vasculopathy or regeneration with or without preeclampsia. Spiral artery remodeling is non-synchronous during placental growth and vascular regeneration. This spatiotemporal sequence may help interpretation of morphologic changes of decidual vasculopathy.

Corrigendum to: Drosera × sidjamesii (Droseraceae): systematics and ecology of a natural hybrid from Western Australia

2007 ◽  
Vol 20 (2) ◽  
pp. 186
Author(s):  
Allen Lowrie ◽  
John G. Conran
Keyword(s):  
Western Australia ◽  
Parental Species ◽  
Elevation Gradient ◽  
Natural Hybrid ◽  
Peat Soils ◽  
Cytological Examination ◽  
White Sand ◽  
Water Field ◽  
Almost All ◽  
High Degree

The natural hybrid Drosera � sidjamesii Lowrie & Conran from Lake Gnangarra north of Perth, Western Australia is described and defined as a cross between D. nitidula Planch. subsp. omissa Marchant & Lowrie auct. non Diels and D. pulchella Lehm., between which it shows a high degree of intermediacy for almost all characters. Cytological examination of the hybrid and its parents confirms that the former at 2n = 46 is a combination of the 2n = 28 in D. nitidula subsp. omissa and 2n = 18 in D. pulchella. The hybrid grows along a narrow ecotone between the parental species, largely on sandy peat and along a presumed soil moisture/elevation gradient caused by the nearby lake. Nevertheless, within this ecotone the hybrid is significantly more frequent than either parental species, with D. pulchella mainly growing in peat soils closer to the lake and D. nitidula subsp. omissa on white sand further from the water. Field observations of morphotypes also suggest that the hybrid has arisen several times at the site, and that a limited number of plants at the site are becoming fertile and setting seed.

Drosera × sidjamesii (Droseraceae): systematics and ecology of a natural hybrid from Western Australia

2007 ◽  
Vol 20 (1) ◽  
pp. 44 ◽  
Author(s):  
Allen Lowrie ◽  
John G. Conran
Keyword(s):  
Western Australia ◽  
Parental Species ◽  
Elevation Gradient ◽  
Natural Hybrid ◽  
Peat Soils ◽  
Cytological Examination ◽  
White Sand ◽  
Water Field ◽  
Almost All ◽  
High Degree

The natural hybrid Drosera × sidjamesii Lowrie & Conran from Lake Gnangarra north of Perth, Western Australia is described and defined as a cross between D. nitidula Planch. subsp. omissa Marchant & Lowrie auct. non Diels and D. pulchella Lehm., between which it shows a high degree of intermediacy for almost all characters. Cytological examination of the hybrid and its parents confirms that the former at 2n = 46 is a combination of the 2n = 28 in D. nitidula subsp. omissa and 2n = 18 in D. pulchella. The hybrid grows along a narrow ecotone between the parental species, largely on sandy peat and along a presumed soil moisture/elevation gradient caused by the nearby lake. Nevertheless, within this ecotone the hybrid is significantly more frequent than either parental species, with D. pulchella mainly growing in peat soils closer to the lake and D. nitidula subsp. omissa on white sand further from the water. Field observations of morphotypes also suggest that the hybrid has arisen several times at the site, and that a limited number of plants at the site are becoming fertile and setting seed.

New species of Torrendia (Fungi, Agaricales) from remnant woodlands in the wheatbelt region of Western Australia

1999 ◽  
Vol 12 (1) ◽  
pp. 145 ◽  
Author(s):  
Neale L. Bougher
Keyword(s):  
New Species ◽  
Western Australia ◽  
Late Stage ◽  
Soil Surface ◽  
Spore Dispersal ◽  
Diagnostic Features ◽  
Two New Species ◽  
Stipe Elongation ◽  
Eucalypt Woodland

Two new species of sequestrate (truffle-like fungi) Basidiomycetes of the putatively ectomycorrhizal genus Torrendia Bres. with contrasting basidiome morphology are described from remnant patches of eucalypt woodland in the wheatbelt of Western Australia: Torrendia grandis Bougher and Torrendia inculta Bougher.Like other species of Torrendia, they have basidiomes which develop and mature mostly underground but may break through to the soil surface at a late stage of maturity. The gleba of Torrendia species does not become powdery. A comparison of the main diagnostic features of all known taxa of Torrendiais provided. T. grandishas stocky basidiomes with an agaric-like pileus. T. inculta has a gleba which fragments during stipe elongation. The basidiome development of T. incultaisdescribed and illustrated, and some possible mechanisms of spore dispersal are discussed.

Genetic diversity and the utilisation of Acacia species complexes in agroforestry in Western Australia

2003 ◽  
Vol 16 (1) ◽  
pp. 49 ◽  
Author(s):  
M. Byrne ◽  
L. Broadhurst
Keyword(s):  
Western Australia ◽  
Native Species ◽  
Genetic Relationships ◽  
Dryland Salinity ◽  
Woody Perennials ◽  
Woody Perennial ◽  
Acacia Species ◽  
Species Complexes ◽  
Agricultural Areas ◽  
High Degree

Dryland salinity is a major problem in the agricultural areas of Western Australia, having significant detrimental impacts in both agricultural and non-agricultural arenas. Development of new woody perennial tree crops is an option for recharge control in the management of salinity and there is a focus on development of native species that are adapted to low-rainfall areas, with potential for commercial production. Acacia is an important genus for utilisation of woody perennials as there is a large number of species occurring in a wide variety of habitats, and many Acacia species are utilised throughout the world for a range of purposes. In Western Australia, the following three species are of interest for development for commercial utilisation in agroforestry plantings: A.�microbotrya, A. acuminata and A. saligna. All three species show a high degree of morphological variation and are likely to consist of several taxa. Lack of understanding of taxonomic entities and their genetic relationships will hinder the utilisation and development of these species. A combined genetic and taxonomic study has defined the morphological and genetic variation within the A. acuminata complex and identified several taxa. Similar studies will also be expected to define taxa within the A. microbotrya and A. saligna complexes.

Sign in / Sign up

Export Citation Format

Share Document