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This CD contains a collection of reports on samples from Arafura Basin wells (biostratigraphy, organic petrology, fluid inclusions - GOI, organic geochemistry and geohistory modelling) generated by GA staff and by external contractors and collaborators based on new analyses carried out during 2004 and 2005.

The relative distributions and stable carbon isotopic compositions of aliphatic and certain aromatic biomarkers from eleven torbanites from Scotland, South Africa and Australia covering the Late Carboniferous to Late Permian rich in B. braunii fossils are stringently scrutinised for any evidence of molecular features which may be characteristic of palaeogeographical location of deposition. Torbanites from South Africa and Australia (Temi) were deposited in the Permian and Late Carboniferous when Gondwana was covered by an extensive ice sheet. Australian (Newnes) torbanites were deposited in the Late Permian when the climate began to warm up changing from glacial to temperate. Other samples from Scotland are of Carboniferous age and were deposited when Laurasia was located within the equatorial zone. All torbanites are composed of abundant n-alkanes and novel macrocyclic alkanes. These compounds are ascribed a B. braunii algeanan origin based on similar ?13C. All samples are also characterised by a high cyanobacterial input. Differences in other biomarker distributions and stable carbon and isotopic compositions can be used to classify the torbanites into 3 groups (A, B and C), which also correlate to three different palaeogeographical locations: Group A - southern Africa and eastern Australia (Temi) torbanites are characterised by a high relative abundance of cyanobacterial hopanoids, methylotrophic hopanoids and abundant branched hydrocarbons (including 13C enriched novel monomethylalkanes) (ii) Group B - eastern Australia (Newnes and Glen Davis) torbanites contain relatively high amounts of drimanes and abundant 13C enriched novel monomethylalkanes (iii) and Group C - Scottish torbanites (Torbane Hill and Westfield) contain high relative amounts of cyanobacterial hopanoids, methylotrophic hopanoids and abundant branched aliphatics (but no 13C enriched novel monomethylakanes).

Abundant, micron-scale, spherical aggregates of 2?5 nm diameter sphalerite (ZnS) particles formed within natural biofilms dominated by relatively aerotolerant sulfate-reducing bacteria of the family Desulfobacteriaceae. The biofilm zinc concentration is about 106 times that of associated groundwater (0.09 ? 1.1 ppm Zn). Sphalerite also concentrates arsenic (0.01 wt %) and selenium (0.004 wt %). The almost monomineralic product results from buffering of sulfide concentrations at low values by sphalerite precipitation. These results show how microbes control metal concentrations in groundwater and wetland-based remediation systems and suggest biological routes for formation of some low temperature ZnS deposits.

This report provides a detailed account of several important aspects relating to the organic geochemical analyses of oil, gas and source rocks in the AGSO - Geoscience Australia laboratory. It focuses on the main methods used for the molecular analysis of the sterane, hopane and alkylaromatic biomarkers as well as the stable carbon isotopic (bulk and CSIA) analysis of these materials. In the following description of these methods the areas of sample preparation, instrumental analysis and data processing/reporting are separately addressed.

Harold Raggatt Award for Distinguished Lecturer Series: "Offshore Australian oil families and petroleum systems" by Dr Dianne Edwards presented as a powerepoint presentation on 1 August 2001.

The technique of Reaction Gas Chromatography-Mass Spectrometry (R-GCMS) has been applied to the analysis of the polar extracts from a Heartbreak Ridge lignite (Bremer Basin, Western Australia; Eocene age) and a Monterey Formation shale (Naples Beach, USA; Miocene age). A catalyst, palladium black, is packed into glass liners for split vaporising injection. The liners are then placed into the injection port to catalyse the gas phase reaction of volatile polar mixtures. Hydrogen gas is used both as the reactant for hydrogenation/hydrogenolysis, and as the carrier gas for the subsequent separation. The reaction products are mostly hydrocarbons, and are swept on to the column where they are chromatographically resolved by the non-polar stationary phase. The products are then identified by mass spectrometry. The fully active catalyst is effective in hydrogenating and isomerising alkenes as well as partially hydrogenating aromatic moieties. Desulphurisation of thiols, sulphides, and thiophenes readily occurs also. Oxygenated compounds such as primary alcohols, acids, esters and ethers undergo a decarbonylation/decarboxylation, while secondary alcohols are reduced to the parent hydrocarbon. Polar fractions react to produce compound distributions that are characteristic of the organic matter source, namely angiosperm-derived triterpenoids and bacterially-derived hopanoids. The reaction of the polar fraction from the Monterey Formation shale results in the formation of high relative amounts of pristane and phytane. A suite of steroids and triterpenoids, typical of marine organic matter, is also observed. R-GCMS provides less detailed information on the exact nature of the functionalised lipids partitioned within the polar fraction compared to more conventional wet chemical analyses. However, this technique requires only a GCMS instrument fitted with a vaporising injector, which acts as a chemical reactor at the inlet of the column. The main advantages of R-GCMS are its speed, low sample requirement, and production of easily resolved and identified products.

Compelling evidence is presented for the process of lipid sulfurisation in humic coal-forming environments. The production of reduced inorganic sulfides by sulfate-reducing bacteria during early diagenetic marine transgression enabled the selective sequestration of functionalised lipids in the polar and asphaltene fractions from the Eocene, marine-influenced Heartbreak Ridge lignite deposit, southeast Western Australia. Nickel boride desulfurisation experiments conducted on these fractions released small, but significant, quantities of sulfur-bound hydrocarbons. These comprised mostly higher plant triterpanes, C29 steranes and extended 17?(H),21?(H)-hopanes, linked by one sulfur atom at, or close to, sites of oxygenation in the original natural product precursors. These sulfurised lipids mostly derive from the same carbon sources as the free hydrocarbon lipids, the exception being the sulfurised extended hopanoids, which may be partially derived from a different bacterial source compared to the free hopanoids. These results indicate that the selectivity and nature of steroid and hopanoid vulcanisation in coal-forming mires is akin to that observed in other sedimentary environments. However, the diversity of sulfurised higher plant triterpanes is greater than that typically reported in immature coals. This selective preservation mechanism explains the formation of the structurally-related biomarkers in more mature sulfur-rich humic coals.

AGSO's 1995-96 Petrel Sub-basin Study was undertaken within AGSO's Marine, Petroleum and Sedimentary Resources Division (MPSR) as part of MPSR's North West Shelf Project. The study was aimed at understanding the stratigraphic and structural development of the basin as a framework for more effective and efficient resource exploration. Specifically, the study aimed to: - define the nature of the major basement elements underlying the Petrel Sub-basin and their influence on the development of the basin through time, - determine the nature and age of the events that have controlled the initiation, distribution and tectonic evolution of the basin; - define the nature and age of the basin fill, and the processes that have controlled its deposition and deformation; and, importantly, - determine the factors controlling the development and distribution of the basin's petroleum systems and occurrences.