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The Permo-Trias sic Bowen Basin is the northernmost structural element of the ca. 2000 km long Bowen—Gunnedah—Sydney Basin System in eastern Australia (Figure 1). The Bowen Basin formed through back-arc extension and foreland subsidence prior to the break-up of Gondwana, resulting in a series of distinct domains reflecting basement morphology and the effects of tectonism (Fielding et al., 1990; Murray, 1990; de Caritat and Braun, 1992). It contains up to 10 000 m of terrestrial and shallow marine siliciclastic sediments (Totterdell et al., 1995), and is economically significant, containing abundant coal and widespread accumulations of coal seam and natural gas.

The Permo-Triassic Bowen Basin (Figure 1) is a backarc extentional foreland basin that contains up to 6500 m of mainly terrigenous siliciclastic felsic sediments. The basin is heavily intruded by mafic intrusions and lesser dykes and sills as a result of intense magmatism which accompanied the breakup of the supercontinent of Gondwana in the middle to late Mesozoic (Veevers, 1989). Magmatism continued episodically throughout the Cretaceous and Tertiary (Baker et al., 1995; Raza et al., 1995; Golding et al., 1996).

Preface M. Mastalerz, M. Glikson. Regulatory Regimes Strategies Economic Analysis and Regulations of Coalbed Methane. Resource Assessment Exploration & Reservoir Evaluation. Sources & Thermal History Effect on Quantity, Quality, Retention and Migration of Coalbed Methane. Reservoir Quality Evaluation In-Situ Stress Structure, Hydrogeology, Micro-Structure. Methane Emission to the Atmosphere & Their Management. Modelling Coalseam Methane and Oil Generation in Hydrothermal Systems. Coal-Sourced Liquid Hydrocarbons: Generation, Accumulation. Notes/Short Papers.

We model the hydrothermal maturation of hydrocarbons in the Bowen Basin of Australia with the program HYDROMAT (Lopez et al., these proceedings). HYDROMAT is used to determine the vitrinite reflectance and the generation of bulk hydrocarbons, hydrocarbons with one to four carbons, and hydrocarbons with five carbons or more during the evolution of the Bowen Basin. The uplift, subsidence, erosion, deposition, fluid flow and heat transfer, and thermal history of the Bowen Basin are reconstructed in order to model the maturation history of the hydrocarbon producing sediments. The effect of high temperature Cretaceous intrusions on the Bowen Basin is also modeled. We focus on the German Creek and Pleiades coal seams and find good agreement between our results and actual data for vitrinite reflectance. Our results support previous experimental studies, which suggested that hydrothermal fluid circulation and high temperature sills and dikes created the high ranking coals and methane gas deposits found in the Bowen Basin. According to our modeling results the regional Triassic high heat flow event was responsible for generating the largest fraction of the total hydrocarbons produced during the entire history of the Bowen Basin. This is consistent with the coexistence of bitumen and minerals of hydrothermal alteration in the Bowen Basin sediments.

Coal seam gases collected from Bowen Basin cores have moderately negative methane carbon isotope compositions (−51 ± 9 per mil) which overlap the published range for Australian coal seam methane of −60 ± 11 per mil. No systematic relationship between coal rank and methane δ13C value is apparent. A thermogenic origin for methane has been assigned when its carbon isotope composition is heavier than −60 per mil, although biogenic methane generated in closed systems may have similar δ13C values from −60 to −40 per mil depending on the methanogenic pathway and the carbon isotope composition of the source. Subordinate inputs from biogenic methane could account for some of the isotopic variability of the desorbed methane; however, a good correlation between desorbed methane volumes and bitumen/pyrobitumen content suggests that much of the methane sorbed in the coal was produced by secondary cracking of bitumen.

A two-dimensional computer program (HYDROMAT) for modeling the maturation of coal in sedimentary basins affected by hydrothermal circulation has been constructed. The program considers the effect of fluid flow on the thermal regime through time. The program contains: 1) a geodynamic module to simulate compaction, erosion, deposition, and tectonic uplift and subsidence of the sediments, 2) a fluid flow and thermal module to solve the coupled fluid flow and heat transfer equations, and 3) a chemical kinetic module to simulate the maturation of organic matter. The effect of magmatic intrusions during the evolution of a basin is considered. Coordinates fixed to the strata (Lagrangian coordinates) are used to follow the evolution of the coal generating units. The kinetic module uses the distribution of activation energies for parallel Arrhenius-type first order rate expressions to calculate the extent of chemical transformations over the thermal history of the basin. The program has been used to assess the effect of advective and/or convective fluid circulation on the generation of hydrocarbons. Our initial results suggest that for basins affected by high heat flow and fluid circulation, HYDROMAT can reproduce better the maturation of organic matter than conventional conductive models.

Chaotically structured diamictite from the inner ring syncline surrounding the central uplift of the Woodleigh impact structure contains shocked metamorphic and impact melt-rock fragments, largely derived from Ordovician and Devonian target sandstones. Coarse illite fractions ( 0.2 μm fractions from the diamictite without smectite and K-feldspar cluster around 360 Ma, consistent with Rb–Sr data. Crystallisation of newly formed illite in the impact melt rock clasts and recrystallisation of earlier formed illite in the sandstone clasts preserved in the diamictite, are attributed to impact-induced hydrothermal processes in the Late Devonian. The illitic clays from the diamictite and from the sandstones have very similar trace element compositions, with significantly enriched incompatible lithophile elements, which increase in concentrations correlatively with those of the compatible ferromagnesian elements. The unusual trace element associations in the clays may be due to the involvement of hot gravity-driven basinal fluids that interacted with rocks of the Precambrian craton to the east of the study area, or with such material transported and reworked in the studied sedimentary succession.

Selected Papers from the 5th International Symposium on Applied Isotope Geochemistry, Heron Island, Great Barrier Reef, Australia, 26–30 May 2003

Dawsonite, NaAlCO3(OH)2, is widespread as a cement, replacement, and cavity filling in Permo-Triassic sedimentary rocks of the Bowen-Gunnedah-Sydney basin system, eastern Australia. The origin of dawsonite in these rocks was studied by petrographic and stable isotope analysis. Dawsonite d13C (PDB) values range from -4.0 to +4.1% and are remarkably consistent throughout the Bowen-Gunnedah-Sydney basin system. These values indicate either a marine carbonate or magmatic source for carbon in the dawsonite. A magmatic carbon source is considered more likely on the basis that (1) evidence of and the cause for widespread marine carbonate dissolution in the sedimentary successions are not apparen , (2) dawsonite is widespread in both marine and nonmarine facies, (3) the region has been the site of major igneous activity, (4) other dawsonite deposits of similar carbon isotopic composition are linked to igneous activity, and (5) magmatic CO2 accumulations are known in parts of the Bowen-Gunnedah. Sydney basin system. The timing of igneous activity in the Bowen Basin constrains the timing of dawsonite formation in the Bowen-Gunnedah-Sydney basin system to the Tertiary, consistent with textural relationships, which indicate that dawsonite formed late during the burial history of the Permo-Triassic sequences. The distribution and interpreted origin of dawsonite implies magmatic CO2 seepage in the Bowen-Gunnedah-Sydney basin system on a continental scale.

Background/Aims: Previous studies of body composition in cirrhosis have either measured only one body compartment, used alcoholic subjects, or not corrected body composition for physical characteristics. The aim of this study was to perform a detailed analysis of body composition in subjects with nonalcoholic cirrhosis. Methods: Simultaneous measurements of total body potassium and total body water were performed and values of body cell mass and body fat were corrected for physical characteristics. Results: Child's class C patients had a significantly lower mean total body potassium index (i.e., percent observed value/expected value) and body fat index than class A or B patients. Eighty-one percent of class C patients had simultaneous reductions in body fat and body cell mass, and 71% of patients with class A disease had a significant reduction in either or both compartments. Nine patients showed the pattern of tissue loss seen with short-term starvation. Fourteen patients showed the pattern of tissue loss seen in physiological stress. Conclusions: Severe liver disease is characterized by significant reductions in body fat and body cell mass, most class A patients have a significant reduction in some nutritional compartments, and the pattern of tissue loss may reflect mechanisms of tissue wasting.

The phyllic alteration in a number of circum-Pacific porphyry Cu-Au deposits is related to high-temperature saline magmatic fluids. This contradicts the widely used genetic models wherein phyllic alteration formed as the result of mixing between magmatic and meteoric fluids. At the Endeavour 26 North porphyry deposit in eastern Australia, the transition from early potassic to the main-stage phyllic alteration is associated with fluids that with time decline in total salinity, NaCl/KCl, and temperature from ~600 to ~550 degrees C. Calculated and measured delta^18 O and delta D compositions of fluids (5.1-8.5 parts per thousand, -57 to -73 parts per thousand delta D) confirm a primary magmatic origin for both the early potassic and main- stage phyllic alteration. These results are consistent with other recent studies (e.g., El Salvador, Chile, Far Southeast, Philippines, and Panguna and Porgera, Papua New Guinea) and suggest that, rather than these results being unusual, a major revision of porphyry Cu genetic models is required.

A suite of variably metasomatised camptonite dykes and rare stocks, named the Fu Intrusives, has been recognised within thrust plates of Mesozoic slates in a 3000-km2 portion of the New Guinea Thrust Belt. The intrusions were emplaced prior to Oligo-Miocene fold deformation and low-grade regional metamorphism of their host, and consequently have foliated margins and are cross-cut by metamorphic quartz veins. Samples from the less altered stocks display primary cumulophyric aggregates of kaersutite + titansalite + titanbiotite, set in a matrix of albite + salite + apatite ± olivine ± quartz. Calcite ocelli are occasionally present. REE patterns ( La CN Lu CN ∼ 10 , La ∼ 100 × chondrite) and initial Sr ratios (∼0.7042) are typical of alkaline lamprophyres. Kaersutite and titanbiotite separates from such samples have yielded concordant KAr ages of ∼75 Ma (Campanian), which we accept as the age of intrusion. However, the dykes have suffered heavy texture-destructive carbonate-sericite alteration, though relict cumulophyric texture and globular structures are sometimes observed. Composition-volume calculations suggest that metasomatism was accompanied by loss of Na, Ti and P; and systematic addition of Ca, Fe and CO2, as well as progressive LREE depletion and Fe reduction. Alteration carbonates exhibit a narrow range of δ18O-values (+ 13.8 to + 14.9‰), indicating uniform conditions of metasomatism throughout the terrain. The calculated fluid δ18O at a model temperature of 300 ± 50°C is +8±2‰ , which corresponds with that deduced from the δ18O-value (+ 12.3‰) of the cleanest sericite separate. The four analysed sericite separates have a mean δD of −64 ± 12‰ , implying an hydrogen isotopic composition for the alteration fluid of −58 ± 30‰ at 300 ± 50°C. The calculated fluid composition therefore overlaps the normal range of metamorphic and magmatic waters. However, C and Sr isotopic ratios of the alteration carbonates (δ13C − 7.3 to + 0.4‰; 87 Sr 86 Sr 0.7076–0.7126) strongly support a crustal source for the metasomatic fluids. This is corroborated by field evidence that country rock slates adjacent to the dykes are unaffected by carbonate metasomatism and hence were in equilibrium with the alteration fluid. We therefore conclude that regional carbonate metasomatism of the Fu Intrusive Suite occurred as a result of metamorphic dewatering of their host rocks during slaty cleavage development.

It is commonly assumed1,2 that seawater-derived carbon in altered volcanic rocks is the only major pre-metamorphic carbon-in-carbonate reservoir in Archaean greenstone belts. Thus carbonates from Archaean gold deposits with stable isotope ratios too negative (median δ13C ≈ −3‰) to have been derived from such carbon (δ13C usually assumed to be near 0‰) have been interpreted as being derived from a local felsic magmatic source1. Barley and Groves3, however, recognize two carbonate-alteration styles that predate regional metamorphism and gold mineralization in the Norseman–Wiluna greenstone belt of Western Australia: evidence is summarized below. These are seafloor alteration and fault-controlled regional alteration, which, as shown below, have completely different carbon isotope compositions. The latter (median δ13C = −4.8‰) implies a major juvenile carbon (CO2) flux from the mantle during greenstone-belt evolution, and is thus of fundamental importance in itself. However, here we show why the mere existence of two carbon-in-carbonate reservoirs and variation in carbon isotope ratios of carbonates between individual gold deposits in one area, negate some of the fundamental assumptions used to support magmatic-fluid models1.

The ability to distinguish ancient lamprophyres from other mafic and ultramafic intrusive rock types has become increasingly important. Lamprophyres have been used as marker horizons in the mapping of several Precambrian terranes, they have been recognized for decades as possible indicators of gold mineralization, and their presence has implications for the tectonic interpretation of ancient greenstone belts. Whilst fresh, undeformed lamprophyres are readily recognized, metamorphosed, altered and/or deformed examples are more problematical. The intrusive ages of Kambalda lamprophyres are constrained by available field and geochronological evidence, including direct dating of one kersantite, to the period 2684-2660 Ma. These rocks therefore belong to the world's oldest group of alkaline rocks and lamprophyres so far recognized, which also includes contemporaneous examples from Canada, Zimbabwe and, probably, Tanzania. Despite their extreme age and low- to medium-grade regional metamorphic history, these rocks still preserve characteristic lamprophyric textures, chemistry and mineralogy. Only where metamorphism has been overprinted by gold-related alteration and deformation do the lamprophyres cease to be recognizable petrographically. However, their unique chemistry persists and, despite losses of the most mobile elements from presumed magmatic compositions, altered and deformed specimens still retain far higher contents of Sr, K, Ba, Th, Nb, P, Zr and Ce than basalts of the local greenstone succession. Even lamprophyres which have been converted to biotite-plagioclase-carbonate-pyrite schists retain this distinctive chemical signature. During both alteration and metamorphism, ‘mobile’ elements (K, Rb, Sr, Ba) display far larger changes than archetypal ‘immobile’ elements (Ce, Nb, Zr, P, Ti), clearly sanctioning traditional preference for the latter in assessing altered rocks. However, the surprising loss of Nb during biotitization of hornblende indicates that negative Nb anomalies, conventionally regarded as indicators of subduction-related magmatism, can also be induced purely by alteration processes.

The no. 4 lode is a silicified, pyritic shear zone with gold telluride mineralization which is located in the Golden Mile dolerite along the western limb of the Kalgoorlie syncline. Wallrocks in this zone have undergone a series of metamorphic and metasomatic events. This alteration is characterized by an increase in the KO/NaO ratio, introduction of CO and S, and significant enrichment of Au, Ag, Te and other ore-forming constituents. Major- and trace-element and isotopic data are presented (40 chemical analyses). Ore mineralization is thought to have formed by reaction of chloritic host rocks with a moderately-reduced, near-neutral hydrothermal fluid at T 250 + or - 50oC. Isotope and geochemical data suggest that these ore fluids were of metamorphic derivation and may have incorporated magmatic C, S, and possibly precious metals at deeper levels in the crust.- J.E.S.

High- CO 2 gas fields serve as important analogues for understanding various processes related to CO 2 injection and storage. The chemical signatures, both within the fluids and the solid phases, are especially useful for elucidating preferred gas migration pathways and also for assessing the relative importance of mineral precipitation and/or solution trapping efficiency. In this paper, we present a high resolution study focused on the Gorgon gas field and associated Rankin Trend gases on Australia’s North West Shelf. The gas data we present here display clear trends for CO 2 abundance (mole %) and δ 13 C CO 2 both areally and vertically. The strong spatial variation of CO 2 content and δ 13 C and the interrelationship between the two suggests that processes were active to alter the two in tandem. We propose that these variations were driven by the precipitation of a carbonate phase, namely siderite, which is observed as a common late stage mineral. This conclusion is based on Rayleigh distillation modeling together with bulk rock isotopic analyses of core, which indicates that the late stage carbonate cements are related to the CO 2 in the natural gases. The results suggest that a certain amount of CO 2 may be sequestered in mineral form over short migration distances of the plume.

Summary The recent advances in numerical simulation for primary coalbed methane (CBM) recovery and enhanced coalbed-methane recovery (ECBMR) processes are reviewed, primarily focusing on the progress that has occurred since the late 1980s. Two major issues regarding the numerical modeling will be discussed in this review: first, multicomponent gas transport in in-situ bulk coal and, second, changes of coal properties during methane (CH4) production. For the former issues, a detailed review of more recent advances in modeling gas and water transport within a coal matrix is presented. Further, various factors influencing gas diffusion through the coal matrix will be highlighted as well, such as pore structure, concentration and pressure, and water effects. An ongoing bottleneck for evaluating total mass transport rate is developing a reasonable representation of multiscale pore space that considers coal type and rank. Moreover, few efforts have been concerned with modeling water-flow behavior in the coal matrix and its effects on CH4 production and on the exchange of carbon dioxide (CO2) and CH4. As for the second issue, theoretical coupled fluid-flow and geomechanical models have been proposed to describe the evolution of pore structure during CH4 production, instead of traditional empirical equations. However, there is currently no effective coupled model for engineering applications. Finally, perspectives on developing suitable simulation models for CBM production and for predicting CO2-sequestration ECBMR are suggested.

Mineralogical studies were performed on authigenic clay minerals of mudrocks, sandstones, and bentonites from 38 boreholes in the Late Permian coal measures of the Bowen Basin. Clay-mineral separations of samples from the northern Bowen Basin consist mainly of (Reichweite, R) R = 1 and R greater than or equal to 3 interstratified illite-smectite (I-S), chlorite, and kaolinite. In the southern Bowen Basin, samples from higher stratigraphic sections are characterized by randomly ordered (R = 0) I-S mixed layers, and kaolinite and chlorite in smaller amounts. Samples from the lower sections consist of (R greater than or equal to 3) I-S, chlorite, chlorite-rich chlorite-smectite (C-S), and laumontite. Examination of the mineralogy and distribution of authigenic clay minerals from the Late Permian coal measures in the northern part of the Bowen Basin indicated that the presence of clay minerals is not systematically related to depth and clay occurrences do not occur regularly. These mineralogical variations of clay in volcaniclastic sediments are incompatible with thermal control. Variations in the rate of fluid flow and potassium supply owing to permeability exert major influences on clay-mineral paragenesis and the reaction of illitization. In more permeable zones (possibly faults or fracture zones), highly illitic clays with lath-shaped morphologies may have precipitated directly from potassium-rich fluids migrating from deeper parts of the basin. In addition, abundant chlorite precipitated contemporaneously with illitic clays, which may have resulted from sufficient magnesium and iron occurring in the fluids as a result of dissolution of intermediate or mafic-rock fragments. At the same time, clay paragenesis with less illitic I-S, kaolinite, and minor chlorite occurs outside the channelized zones of high fluid flow, where a diffusive-flow regime may have predominated with lower ratios of the activities of K+ and H+ (i.e., alpha(K+)/alpha(H+)) in the solutions. In the southern Bowen Basin, depth-related changes in the distribution of clay minerals are evident and may be indicative of thermal control on clay-mineral reactions. Zeolites are present locally in the Late Permian volcaniclastic rocks in the southern Bowen Basin, but not in the north. This is attributed to a low ratio of alpha(CO2)/alpha(H2O) (where alpha = activity) and/or more saline and alkaline solutions.

A hypothetical pilot-scale project was studied to investigate the capabilities of existing coalbed methane (CBM) models in simulating the multicomponent gas sorption and diffusion in coalbeds for CO2-sequestration enhanced coalbed methane (ECBM) production. Further, the effects of coal properties, e.g. cleat permeability, porosity, cleat spacing, sorption isotherms of CH4 and CO2, and initial reservoir conditions, on CO2 breakthrough and methane recovery were investigated as well. The calculated results suggested that the multicomponent sorption equilibria described using IAS/Langmuir isotherm and extended Langmuir isotherm are quite different. The gas diffusion rate can not be accurately modeled using Warren & Root equation based on dual-porosity model (pseudo-steady state approach), which is so far the most popular approach used in CBM models to describe gas diffusion process. This indicates that a rigorous multicomponent gas diffusion model should be incorporated in CBM models to improve numerical simulation and prediction of CBM/ECBM production.

This experimental study aims to characterize the bioavailability of six Surat Basin Walloon coals to exogenous methanogenic consortia, and the possible compositional and environmental factors that control bioavailability. Finely crushed coal cores samples were inoculated with digested sludge culture sourced from domestic wastewater treatment plants in biomethane potential bottles (BMP bottles) maintained at mesophilic temperature. Degradation of coal compounds was demonstrated via GC-MS characterization of methanol and dichloromethane (DCM) extracts of coals, as well as analysis of volatile fatty acids and alcohols and total dissolved organic carbon (TOC) in water eluents of coals conducted before and after biodegradation. The resulting methane yields ranged from 14 to 33 μmol/g, with an average of 21 μmol/g (0.515 m3/t) achieved within 30 days. Organic solvent-extractable materials accounted for 3.8 to 12% of coal weight. Aliphatic compounds, primarily medium-long-chain n-alkanes, n-alcohols and esters dominated the solvent extracts. Aromatics were detected up to three fused rings, and are rich in dibenzofuran, alkyl benzene, alkyl polyaromatic hydrocarbons, and acetyl diphenyl. The abundance of solvent-extractable matter was found to rely on liptinite content, particularly suberinite. Preservation of these compounds was thought to be facilitated by vitrinite, such as telinite and collotelinite that are rich in micropores, serving as storage for the hydrocarbons. On the other hand, environmental factors, such as microbes-carrying groundwater might compromise coal extractability by converting coal hydrocarbons to biogas. The study has revealed three levels of dependence regarding coal bioavailability: 1) Water solubility - An average 98% of aqueous compounds (based on TOC) was eliminated via biodegradation. These were mainly volatile fatty acids and alcohols, and to a lesser degree, medium-chain n-alcohols, esters and aliphatic amine; 2) Solvent extractability – approximately 35% of solvent-extractable compounds were biodegraded on average, with aliphatics being more bioavailable than aromatics; 3) Heterogeneous moieties, particularly aliphatic hydroxyl, ester bond, ether bond and C-N bond in aliphatic amine - These functional groups are characteristics of compounds that were heavily degraded. The study is to our knowledge, the first coal bioavailability research that demonstrated a detailed linkage between biomethane generation and bio-elimination of coal extractable compounds with connections to petrographic composition and possible environmental factors.