Journal and Proceedings of
The Royal Society of New South Wales
Volume 134 Parts 1 and 2
Colour and Cash: The Exquisite Minerals of the Oxidized Zone
Presidential Address 2001
Peter A. Williams
Abstract: The geochemistry and chemical mineralogy of the oxidized zones of orebodies are extraordinarily complex, much more so than the primary deposits from which they are derived. The zones themselves are of great economic importance, especially to Australia. Many of the free-milling gold ores exploited over the last two decades are of supergene origin (secondary gold) and cobalt, nickel and copper deposits of the same kind are of increasing importance. We know much of the equilibrium chemistry of such mineral settings for some elements and something of the general processes that play a part in the development of ore grades in the oxidized zone. For other elements the situation is somewhat more sketchy and of certain aspects, including kinetics of crystallization, temperatures of mineral formation and solid-solution phenomena, we know very little indeed. Oxidized zone mineralization, some of which is exquisitely beautiful, is described in terms of its origin and the associated chemistry necessary to extract metals from these sorts of deposits. Further research directions are highlighted, together with problems that remain to be solved.
Surface Modification: Advancing the Functionality of Materials
Pollock Memorial Lecture in Mathematics and Physics
Marcela M.M Bilek
Abstract: The surface properties of materials are most commonly optimised for their applications by coating with a layer of a material that has the required surface properties. Surface modification allows us to mix and match surface and bulk properties to optimise materials for their applications. For example, base metal door knobs can be made to shine like gold for decorative purposes, the surfaces of steel cutting tools can be hardened by a layer of titanium nitride, and skeletal prosthetic implants can be made more biocompatible by doping with magnesium (Bilek et al. 2000).
A good coating needs to be both contiguous and well adherent. Physical vapour deposition is a flexible coating technique with advantages over wet chemical methods such as electroplating, especially in minimising hazardous waste. The problems of porous films with voids have been solved by the use of techniques in which a fraction of the surface reacting species impinges with elevated energy. The downside of these techniques is that they often lead to significant amounts of intrinsic compressive stress in the films produced. This stress limits the thickness to which films can be grown and often causes films to delaminate exposing parts of the original surface. This is a particularly serious problem in applications where even small exposures of the original surface cannot be tolerated, such as in corrosion protection and biomaterials. In prosthetic implants, the delaminated material presents an even greater problem because it will be released into the body.
In this paper we describe a new generation of methods that offer solutions for the problem of intrinsic stress in surface modifying coatings. The physics behind their ability to alleviate intrinsic stress is presented together with experimental results. The paper concludes with a discussion of further work necessary to develop the techniques to a stage where they can readily be used to coat complex and varied shaped components used in real world applications, with particular reference to the field of biomaterials.
The Centenary of Mary Everitt's ``Gundungurra'' Grammar
Communicated by Michael K. Organ
C.R. Illert
Abstract: Year 2001 marks the centenary of a unique scientific paper (Mathews & Everitt, 1900), on the Gundunara Aboriginal language, whose primary authorship has been in dispute ever since it was read before the Royal Society of New South Wales on 5th December 1900. Complex grammatical forms and structures, accurately preserved in the raw phonetic data within the paper, have been largely overlooked by successive generations of scholars and linguists (Kohen, 1993; Russell, 1914; Turbet, 1989; Dixon, 1980). In fact, Appendix 2 of the present paper is the first attempt by anyone in 100 years to decipher the Gundunara women's Evening-Star Song, a treasure originally published in (Mathews & Everitt, 1900), whose meaning no modern scholar has ever even speculated about. Such has been the rate of research in this neglected field. And, whereas numerous large biographies including (Elkin, 1975) were long-ago written about one of the coauthors, the other coauthor Mary Martha (``Minnie'') Everitt (1854-1937) is still virtually unknown and the important story of how the paper came into being has never been properly told. New advances at the cutting edge of linguistic theory now enable us to demonstrate that the grammar is actually women's language likely to have been collected by Mary Everitt, not her male ``coauthor'', thus shedding light on the principal authorship of this historic and important century-old paper.
ABSTRACTS OF THESES
The Genesis and Tectonic Significance of Chromitite-bearing Serpentinites in Southern NSW
Ian Terence Graham
Abstract of a Thesis submitted for the Degree of Doctor of Philosophy
University of Technology, Sydney 2000
The Tumut Serpentinite Province consists of four major serpentinite belts and numerous small serpentinite bodies, that occupy a long narrow tract within the Lachlan Fold Belt of southern NSW. The tectonic setting of one belt, the Coolac Serpentinite Belt, has been contentious. Much of the uncertainty results from lack of a combined study on the major belts and inadequate age constraints. Resolving the uncertainty will benefit construction of a tectonic model for the evolution of the Lachlan Fold Belt.
The belts mainly comprise massive serpentinite or harzburgite, with internal shear zones of schistose serpentinite, and intrusions of plagiogranite, gabbro, basalt, pyroxenite, dunite and chromitite. The main foliation has a consistent NNW-SSE trend and is similar in the adjacent rock units. The various rock types of the serpentinite belts are geochemically akin to similar rocks from ophiolite sequences.
Podiform chromitites are geochemically, mineralogically and geometrically akin to those in the mantle sequence of most ophiolites. The different chromitite types are interpreted in terms of the degree of evolution of the MORB-type magma and hence the extent of fractionation of the source. Serpentinisation and rodingitisation occurred during progressive cooling of the chromitites and host rocks and were accompanied by systematic fracturing and remobilisation of chemical components.
Radioisotope dating gives an age of crystallisation of 412-400 Ma for the plagiogranites and leucogabbros, whilst an inherited zircon age of 430 Ma appears to be derived from Early Silurian felsic volcanic rocks of the region. As the plagiogranites, leucogabbros and other rock types within the serpentinite belts have common deformational and metamorphic histories, their crystallisation age constrains the ages of deformation and metamorphism.
The serpentinite belts are interpreted as ophiolites of the `embryonic' type that formed within a back-arc basin setting in the Late Silurian-Early Devonian. Crystallisation of the MORB sequence and emplacement onto continental crust, together with metamorphism and deformation may have only spanned 20 Ma. In the Late Silurian to Early Devonian, the Tumut Serpentinite Province differed from basins elsewhere within the Lachlan Fold Belt in that a volcanic arc was ruptured by mantle-derived MORB magmas which ascended to the surface. Their extrusion was short-lived and after the Early Devonian, the development of the Tumut region differed little from that in the rest of the Lachlan Fold Belt.
The development of oceanic crust within the Tumut Serpentinite Province and the generation of granitic magmas within the central and eastern parts of the Lachlan Fold Belt are symptomatic of the same Late Silurian to Early Devonian tectonothermal event. An important aspect of this is that oceanic and crustal rocks need not form from different events or in substantially different tectonic settings.
Ian.T.Graham
Department of Earth Sciences
University of Pretoria, Pretoria 0002
Republic of South Africa
Characterisation of Sperm Surface Antigens in the Guinea Pig
Isurani Ilayperuma
Abstract of a Thesis Submitted for the Degree of Doctor of Philosophy
University of Otago, Dunedin, New Zealand
Fertilisation is one of the most complex and exciting areas in biology. Mammalian fertilisation involves sperm capacitation in the female reproductive tract, passage through the cumulus mass, induction of the acrosome reaction, penetration through the zona pellucida and fusion with the egg plasma membrane. The surface of the sperm head plays a central role in each of these events. The mammalian spermatozoon has a highly regionalised surface. Identification and characterisation of sperm membrane proteins that are involved in gamete recognition and sperm-egg membrane fusion is one of the key problems in current research on mammalian fertilisation.
G11 is a sperm-specific membrane protein implicated in sperm-egg binding and fusion. The main body of this thesis describes characterisation of the G11 antigen. The G11 antigen was purified using anion-exchange chromatography, immuno-affinity chromatography and preparative SDS-PAGE and was subjected to amino acid microsequencing. Internal amino acid sequence data on the 48 kDa G11 antigen revealed sequence homology with the recently discovered guinea pig sperm protein, sperad. Sperad is a transmembrane protein present in the peri-acrosomal membrane of the acrosome-intact spermatozoa. Guinea pig sperad has already been cloned and sequenced. A striking feature of the cytoplasmic domain of sperad is the presence of a repetitive proline-rich sequence, PPQPEQ, which is unique to sperad. Oligonucleotide primers made from the published sperad nucleotide sequence were used to amplify the cytoplasmic domain of sperad from a guinea pig testis cDNA expression library. Three additional forms of the sperad cytoplasmic domain were consequently identified. These isoforms of the cytoplasmic domain of sperad were tested for their ability to bind monoclonal antibody G11 by expression in a prokaryotic gene fusion system as fusion with glutathione S-transferase. Results obtained from these experiments confirmed that the G11 epitope is specific for the cytoplasmic domain of sperad. It is likely that the predominant epitope recognised by the monoclonal antibody G11 is the intracellular repetitive PPQPEQ motif.
Evidence suggests that mammalian spermatozoa fuse with eggs using the equatorial segment plasma membrane. My findings provide evidence that the equatorial segment plasma membrane contains sperad. Sperad is of interest in the context of sperm-egg adhesion and egg activation for a number of reasons. First sperad carries a Arginine-Glycine-Aspartic acid sequence that could potentially dock the equatorial segment plasma membrane with the integrins on the egg surface. Second it is related to a biliary glycoprotein family of adhesion molecules. Third, the repetitive proline-rich cytoplasmic domain of sperad, which is unique to sperad, could act like other cytoplasmic proline-rich regions as an intracellular signaling molecule. Since the cytoplasmic domain of sperad is exposed to the egg following sperm-egg fusion it could act as an egg-activating molecule.
I. Ilayperuma
Faculty of Medicine,
University of Ruhuma,
PO Box 70, Galle,
Sri Lanka
Reef Growth and Lagoonal Sedimentation at High Latitudes, Lord Howe Island, Australia
Dr David M. Kennedy
Abstract of a Thesis Submitted for the Degree of Doctor of Philosophy, University of Sydney, New South Wales, Australia.
The southern limit of coral reef growth in the world occurs on Lord Howe Island (33o30'S, 159o05'E) in the form of a discontinuous 6 km long fringing reef along the western side of the island. Compared with other fringing reefs worldwide it is large being attached to the shoreline only at its northern and southernmost ends while the central portion encloses a lagoon over a kilometre wide. The reef and lagoon are developed over an antecedent surface composed of reefs of Last Interglacial age and calcarenite dunes; however, there appears to be little relation between its topography and that of the modern surface.
Carbonate sediments were being deposited within the lagoon around 6500 years BP coincident with sea level reaching close to its modern level. High-energy open ocean conditions dominated the reef with robust branching corals dominating the developing reef. Sedimentation during this initiation phase strongly reflected the morphology of the antecedent surface. Growth of the reef crest between 6000 and 5000 years BP lead to a reduction in the energy environment of the lagoon allowing for mud deposition. During this period sedimentation occurred at rates of around 5 mm/yr, but up to 10 mm/yr, which infilled almost all the available accommodation space in the lagoon. By 4000 years BP the reef and lagoon were very close to the modern surface having accumulated over 11 m, possibly up to 30 m, of sediment. Sediments younger than 3000 years BP form a veneer over these older units with the main deposition being confined to embayments, the coastal plain and infilling blue holes.
Reef growth and lagoonal infill at the southernmost environmental limit have been luxuriant and rapid, comparable with low-latitude reef systems. The main period of growth occurred during the mid-Holocene. Modern sedimentation appears to be restricted to the lagoon and there is little reef progradation. The reef on Lord Howe therefore appears to be related to luxuriant growth in the mid-Holocene.
Dr David M. Kennedy
School of Geosciences,
University of Wollongong,
Wollongong NSW 2522,
Australia