Showing papers by "Macquarie University published in 1977"

Oxygen and hydrogen isotope compositions as indicators of granite genesis in the New England Batholith, Australia

Abstract: Oxygen and hydrogen isotope studies of a number of granite suites and mineral separates from the New England Batholith indicate that δO18 can be used to discriminate the major granite protoliths. The granite suites previously subdivided on the basis of mineralogical and geochemical criteria into S-type (sedimentary) and I-type (igneous) have δO18 values consistently higher in the S-type granites (10.4–12.5) than in the spatially related I-type plutons (7.7–9.9). There appears to be a systematic variation in δO18 from the most S-type to the most I-type granites, the dividing point between the two occuring at δO18 equal to 10. A group of leucocratic granites that form about half of the batholith and difficult to classify mineralogically and geochemically is found to have low δO18 values (6.4–8.1), suggesting an affinity to the most I-type granites. A single leucogranite pluton with minor muscovite has a δO18 of 9.6 which is significantly higher than other leucogranites indicating a different origin perhaps involving amphibole fractionation.

Garnet in silicic liquids and its possible use as a P-T indicator

Abstract: Melting experiments on a model pelitic composition yield low-spessartine garnet as an important residual phase at pressures above 7 kb. The K D values for distribution of iron and magnesium between coexisting garnet and liquid in the pelitic composition are mainly sensitive to temperature, but also have a small pressure dependence. At temperatures above 950 ° C garnet has a higher $$\frac{{Mg}}{{Mg + Fe}}$$ value than coexisting liquid, but below 950 ° C the garnet $$\frac{{Mg}}{{Mg + Fe}}$$ value is lower than that of the coexisting liquid. Thus at temperatures below 950 ° C silicic magmas may fractionate garnet and produce more magnesian derivative liquids. Reconnaissance experiments with added MnO content in the model pelite demonstrate that spessartine-rich garnets are stable in silicic liquids to pressures as low as 3 kb. The MnO and CaO contents of the experimentally crystallized garnets show an antipathetic relation. Also, the grossular content of near-liquidus garnets crystallizing from a range of compositions increases with increasing pressure. The spessartine and grossular contents of most natural garnets in eastern Australian granitic rocks suggest that these garnets formed at pressures greater than 5 kb. Increased spessartine content allows crystallization of garnet in equilibrium with a silicic magma well within the pressure limit of stability of cordierite, provided the garnet contains ≧10 mol.% spessartine. Thus the depth range over which garnet and cordierite may coexist in a silicic melt is broadened, subject to the availability of MnO. The effect of increased Mn content on the low-pressure stability limit of garnet may also explain the lack of resorption of some garnets in granitic magmas, as these magmas rise to shallower levels. These euhedral garnets characteristically show zoning from an Mn-poor core (typically 4 % MnO) and may reflect continued growth of the garnet in a low pressure regime, stabilized by Mn concentrated in the residual liquid fractions of the crystallizing magma.

Two-dimensional magnetotelluric inversion

Abstract: Summary. When complex structure is encountered in magnetotelluric surveys, interpretation by locally fitted layered models is of questionable validity. However, when the processed data show two-dimensional structure, numerical inversion schemes for two-dimensional models may be constructed as an aid to regional data interpretation. The twodimensional magnetotellurics inversion problem is here formulated in a way that may be applied to many problems. A resulting computer program is analysed carefully in terms of its cost relative to that of simpler layered modelling. As an example, the method is applied to some field data where the interpretive advantages of the program become evident.

Two ``S-type'' granite suites with low initial 87 Sr/ 86 Sr ratios from the New England Batholith, Australia

Abstract: Two “S-type” (pelitic) granite suites from the New England Batholith, N.S.W., have Upper Carboniferous ages, indicating that they predate by 40 m.y. the intrusion of hornblende biotite granites, and are the oldest plutons of the batholith. Mineralogically and geochemically both suites have “pelitic” characteristics, one suite containing an Al-rich biotite, muscovite and cordierite, the other an Al-rich biotite and rare pyrope-almandine garnet. Low initial 87Sr/86Sr ratios of 0.706 for both suites probably reflect the volcanoclastic nature and young age of the sedimentary source of these granites at the time of melting. The age of the suites coincides with the last stages of (Andean type?) volcanism along an andesite/dacite volcanic chain to the west, suggesting an origin for the “S-type” granitic magma by partial melting of deformed sediments marginal to a continental region.

Prenatal alcohol consumption and open-field behaviour in rats: effects of age at time of testing.

Abstract: Throughout gestation pregnant Wistar rats consumed a nutritious liquid diet containing 35% ethanol-derived calories. Control mothers were fed lab-chow. Subsequently, the offspring of the ethanolfed mothers displayed significantly greater activity (ambulation) in an open-field test at 28 and at 56 days of age, but not at 112 days of age. No differences in defecation were observed at any age.

Are rare earth elements mobile during spilitisation

Abstract: FROM the study of rare earth elements (REE) in basalts, spilites and hydrothermally altered basalts in the ocean floor1–5, ophiolites6,7, geosynclines3,8 and low-grade to greenschist facies regions9 it has come to be accepted that the REE are immobile during rock alteration. This conclusion has led to the use of certain abundance ratios, particularly La/Sm and La/Yb, as indicators of parent magma type and genesis. Despite some suggestions2,10 that REE, such as La and Ce, may be mobile during sea-water/rock interaction, hydrothermal alteration or spilitisation of igneous rocks, the REE continue to be treated (e.g. refs 6 and 7) in an analgous fashion to Ti, Y and Zr (ref. 11). Here we show from analyses of a variably altered tholeiite flow that spilitisation may, in some circumstances, affect the REE abundances and their chondrite normalised pattern.

A unique cytogenetic system in monotremes

Abstract: All 3 extant genera of monotremes show a unique kind of cytogenetic system involving the formation of a structurally heterozygous chain multiple apparently coupled with a system of complementary gametic elimination. In the echidna Tachyglossus there are 63 chromosomes in the male and 64 in the female. This is associated with an X1X2Y♂/X1X1X2X2♀ sex chromosome system. Additionally in both sexes there are 6 mitotic chromosomes (a-f) which have no obvious homologous partners. At male meiosis these are included with the 3 sex chromosomes in a chain multiple of nine which has the constitution X1·Y·X2·f·e·d·c·b·a. This shows convergent orientation at first metaphase leading to the production of two kinds of sperm, namely X1X2 eca and Yfdb. Since no individual of either sex has been found homozygous for any of the a-f elements it follows that only gametes carrying different combinations of the three unpaired elements give rise to viable offspring. Whether this depends on gametic selection or on zygotic lethality is not known. An apparently identical system operates in Zaglossus. In the platypus Ornithorhynchus, on the other hand, there are 52 chromosomes in both males and females associated with an XY♂/XX♀ sex chromosome mechanism and the presence of 4 consistently unpaired elements (a-d) at mitosis. A chain multiple of 10 forms at male meiosis involving the 2 sex chromosomes, the 4 unpaired elements and two of the small pairs of autosomes. Additionally the six longest autosome pairs in Tachyglossus and the X1 show a polymorphism for size which in heterozygous combination leads to the formation of unequal bivalents at male meiosis.

Separation of Inflation and other Effects from the Distribution of Non-Life Insurance Claim Delays

Abstract: In recent years, as a result of more concentrated research together with the ravages wrought upon some insurers by inflation, the fundamental significance of the so-called run-off triangle in the calculation of provisions for outstanding claims has been increasingly recognised. The run-off triangle, which is a two-way tabulation—according to year of origin and year of payment—of claims paid to date, has the following form, where Cij is the amount paid by the end of development year j in respect of claims whose year of origin is i, i.e. Cij is the total amount paid in year of origin i and the following j years.The information relating to the area below this triangle is unknown since it represents the future development of the various cohorts of claims.

Last‐glacial alluvial fan sedimentation in the Lower Derwent Valley, Tasmania

Abstract: Alluvial fans of the last glacial age in the lower Derwent Valley in southeastern Tasmania were built by debris flows and stream flows. The deposits were derived from periglacial and nivational slope mantles at the highest altitudes in the fan catchments, and from regolith of uncertain affinities at the lowest elevations. The apical and middle parts of the fans commonly consist of coarse-grained debris flow and water-laid deposits, while the distal deposits are predominantly water-laid sheetflood silts and clays. Channels are important in the proximal parts of the fans and are mostly filled with water-laid sediments, less commonly by debris flow deposits. A first approximation to the mean velocity of the last stage of debris flow in a channel is between 4 m/sec and 6 m/sec. A group of ‘water-laid’ sediments shows very poor separation of particle sizes, and two explanations have been offered for these sediments. Firstly, the large quantities of unsorted debris available from the catchments produced moderately well-sorted slurries, or, secondly, openwork stream gravels were infiltrated by later water flows charged with fines. The streams crossing the fans also produced water flows with relatively low suspended sediment concentrations resulting in reasonably good sorting. The debris flows and ‘water-laid’ muddy sediments cannot be distinguished using CM plots. The debris flows display considerable variation in thickness and grain-size characteristics, which is attributable to properties inherent in debris flow behaviour.

Cenozoic sedimentation cycles in Western Australia

Abstract: Cenozoic sediments, mainly carbonates, of the passive margin of Western Australia have been deposited during four cycles of sedimentation: late Paleocene to early Eocene, middle to late Eocene, late Oligocene to middle Miocene, and late Miocene and younger. The Western Australian margin is suitable for a study of the cycles as it has not been deformed except for postrift downwarp, and the low relief of the hinterland has resulted in little deposition of terrigenous sediments during most of the Cenozoic. The cycles may reflect large sea-level fluctuations probably caused by events of global significance. The inferred sea-level variation is greater than that caused by Quaternary glacial eustasy. Present-day sea level is close to the maximum sea level attained during the Cenozoic.

Temperature-induced Changes in Hill Activity of Chloroplasts Isolated from Chilling-sensitive and Chilling-resistant Plants

Abstract: The effect of temperature on Hill activity has been compared in chilling-sensitive and chilling-resistant plants. The Arrhenius activation energy (Ea) for the photoreduction of 2,6-dichlorophenolindophenol by chloroplasts isolated from two chilling-sensitive plants, mung bean (Vigna radiata L. var. Mungo) and maize (Zea mays L. cv. PX 616), increased at low temperatures, below 17 C for mung bean and below 11 C for maize. However, the Ea for this reaction in pea (Pisum sativum L. cv. Massay Gem), a chilling-resistant plant, likewise increased at temperatures below 14 C. A second change in Ea occurred at higher temperatures. The Ea decreased above about 28 C for mung bean, 30 C for maize, and 25 C for pea. At temperatures approaching 40 C, thermal inactivation of Hill activity occurred. These results, when taken together with previous results obtained with the chilling-resistant plant barley, indicate that chloroplasts from both chilling-sensitive and chilling-resistant plants can undergo a change in chloroplast membrane activity at low temperatures above freezing and that the presence of such a change in chloroplast membranes is not necessarily correlated with chilling sensitivity.

Late Quaternary lake levels in southern Afar and the adjacent Ethopian Rift

Abstract: A PERENNIAL problem in using evidence of changing lake levels and river activity to reconstruct Quaternary environments in East Africa stems from our frequent inability to distinguish between effects produced by volcanic and tectonic activity and those related to climatic change. We report here evidence for roughly synchronous changes in lake levels in the volcanically and tectonically active regions of southern Afar and the Ethiopian Rift, which parallel those reported from the Sahel1, the Nile valley2, Kenya3 and Saudi Arabia4. Such synchronous changes in lake levels, allied to independent evidence of moister conditions during phases of high lake levels, are best explained through regional fluctuations in climate.

A dislocation model of grain boundary electrical resistivity

Abstract: Grain boundary electrical resistivities are calculated on the assumption that the scattering is due primarily to the dislocations which constitute these boundaries. Dislocation densities in grain boundaries have been estimated using Frank's formula as modified to take account of lattice symmetry. Dislocation resistivities are calculated ab initio assuming resonance scattering at the Fermi surface, and measured dislocation resistivities are also used where these are available. The calculated grain boundary resistivities are in satisfactory agreement with experimental data for thirteen of the fourteen metals from seven subgroups of the periodic table, for which data is available.

Resolving anisotropy in layered media by joint inversion

Abstract: A finite number of layers must normally be used to represent the electrical properties of a horizontally-layered region. It is well known that these representative layers must include anisotropy. Applying the concept of joint inversion to DC resistivity and magnetotelluric (electromagnetic) data from a structure consisting of many fine layers, we show how the resistivities in the horizontal and vertical directions can be separately determined in each layer. The results are related to the contrasts existing in the interbeds which comprise the composite layers. The method has applications in both engineering and exploration.

English and Sinhala bilingualism in Sri Lanka

Abstract: This study describes the language situation of Sri Lanka (Ceylon) and examines the factors governing the language choice of Sinhalese bilinguals while attempting to correlate such factors with domains and role relations. It also examines the way in which such correlations reflect social differences in Sri Lankan society. The use of two languages by the same speakers almost inevitably affects the forms of the languages so used. The use of English by Sinhalese speakers has led to the functional elaboration of both English and Sinhala. Bilinguals show varying degrees of proficiency in the languages they use. Such disparities in performance have led to differing patterns of bilingualism manifested in different phonological and grammatical features. Materials are drawn from the English of newspapers, fiction, drama, poetry etc. and personal knowledge. (Language as a class indicator; bilingualism; conflict of speech norms; Sri Lankan English.)

Studies on metatherian sex chromosomes VI*. A Third state of an x-linked gene: partial activity for the paternally derived pgk-a allele in cultured fibroblasts of macropus giganteus and M. parryi

Abstract: The locus for the glycolytic enzyme phosphoglycerate kinase A (PGK-A) is sex-linked in the eastern grey kangaroo (M. giganteus) and the pretty-face or whip tail wallaby (M. parryi). Females older than the pouch life stage of development do not express their paternally derived allele in some tissues such as blood and liver. This phenomenon is called paternal X inactivation and is characteristic of kangaroos. This distinguishes them from eutherian females, which are mosaics of two kinds of cell brought about by random X inactivation of either the paternally derived or the maternally derived X chromosome. But in skeletal and cardiac muscle the paternally derived allele is weakly expressed. This paper reports data which show that in fibroblast cells cultured from tissue explants of these two species the paternally derived allele is also weakly expressed. This suggests the possibility of a form of mosaicism as in eutherians but with unequal proportions of the two types of cell. Our results show this is not so. Cloning experiments have been performed with cultured cells from three heterozygous M. giganteus females. A total of 49 clones was obtained and each clone was like its parent culture, i.e. there was a strongly active maternally derived allozyme and a weak paternally derived one. Two interpretations of these data are possible. Each cell may have a fully active maternally derived allele and a partly active paternally derived one. Or the clones themselves may be heterogeneous, such that one or the other of the X-linked alleles may switch on or off every few cell generations or less. Since X inactivation is known to be rather stable this latter hypothesis is considered the less likely. Autoradiography shows that the longer arm of the X chromosome in the cultured cells is late-replicating. Thus later replication of the X chromosome in kangaroos does not necessarily mean complete inactivity. Differences in morphology between the two X chromosomes in females are described.

Water Potential, Growth, and Polyribosome Content of the Stressed Wheat Apex

Abstract: The effect of drought on the growth, ribosomal content, and water potential of the immature floral apex of wheat plants was studied under controlled environment conditions. During drought the water potential of the apex (measured with a thermocouple psychrometer) de creased at approximately the same rate as that of expanded leaves. Elongation and differen tiation of the floral apex ceased at approximately —12 x 105 Pa and the polyribosomal content decreased from 50% of the total ribosomal population to less than 10%. At this water potential also, elongation of expanding leaves was severely inhibited. With continued drought the water potential of the apex continued decreasing. The exposed leaves died at a water potential of about —35 x 105 Pa but the apex was still alive at a water potential of —60 x 105 Pa and after rewatering it eventually resumed growth.

Are wave functions uniquely determined by their position and momentum distributions

Abstract: The problem of determining a square integrable function from both its modulus and the modulus of its Fourier transform is studied. It is shown that for a large class of real functions the function is uniquely determined from this data. We also construct fundamental subsets of functions that are not uniquely determined. In quantum mechanical language, bound states are uniquely determined by their position and momentum distributions but, in general, scattering states are not.

Self-thinning driven by leaf area not by weight

Abstract: THE self-thinning rule is perhaps the most widely applicable principle in plant population dynamics. White1 has shown that it applies to more than 70 species ranging from herbs to trees, in many nutrient conditions. The rule states that W=Kp−3/2, where W is average plant weight, p is the density of plants, and K is a constant. In other words when the log of average weight is plotted against the log of average density for a crowded even-aged plant population, numbers must be lost as the individuals gain weight in such a way that the population's trajectory is held under a line of slope −3/2.

Rare earth element investigation of the Cliefden Outcrop, N.S.W., Australia

Abstract: The effect of low grade hydrous burial metamorphism (prehnite-pumpellyite facies) upon the rare earth elements (REE) has been studied by using samples from the Cliefden Outcrop, New South Wales. The REE, together with other reputedly ‘immobile’ elements, have been mobilised during the metamorphism. Although mobile, the REE have behaved remarkably coherently with little light rare earth (LREE) fractionation. This is reflected in the chondrite normalised patterns which are sub-parallel to parallel in shape. High correlations of REE with other elements can be used to predict the maximum likely variation of these elements in the studied outcrop. The high correlations do not necessarily mean that, for similarly metamorphosed terrains, crystallisation-differentiation processes have operated but may rather have resulted from strong geochemical coherence during post-crystallisation elemental redistribution. The REE do not appear to be strongly domain controlled within the Cliefden Outcrop.

Interpretation of metamorphic assemblages containing fibrolitic sillimanite

Abstract: Microstructural criteria distinguish two types of fibrolitic sillimanite-bearing aggregates, namely: (1) those with fibrolitic sillimanite in clear microstructural equilibrium with the other minerals, and (2) those with fibrolitic sillimanite that appears to have grown without evident modification of pre-existing grain boundaries of the other minerals. However, microstructural criteria rarely permit unambiguous inferences of the relative “timing” of metamorphic reactions producing fibrolitic sillimanite.