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Samples from fresh and propylitically altered rocks from the Black Mountain porphyry Cu-Au deposit were used to study the suitability of apatite as an indicator of the source, chemistry, and evolution of magma and hydrothermal fluids. The rocks all showed homogeneous textures but distinct luminescence. Apatite in the altered rocks had distinct compositions of Cl, Mn, Fe, Mg, Sr, and Pb and a slightly different delta O18 value, suggesting mobilisation during hydrothermal alteration. This suggests that apatite texture, chemistry, and isotopes can be modified by hydrothermal fluids. Altered and magmatic apatite had comparable concentrations of REEs, Y, U,, Th, and Zr and also Nd isotope signatures, indicating retention of some primary magmatic characteristics during alteration. The study showed that cathodoluminescence, elemental compositions, and Sr-O isotope signatures in apatite can be modified during hydrothermal alteration, whereas other components (REE, Y, U, Th, and Zr) and the Nd isotope composition are preserved. It is concluded that these features can be used to constrain the origin, chemistry, and evolution of the primary magma and ore-forming hydrothermal fluids., Samples from fresh and propylitically altered rocks from the Black Mountain porphyry Cu-Au deposit were used to study the suitability of apatite as an indicator of the source, chemistry, and evolution of magma and hydrothermal fluids. The rocks all showed homogeneous textures but distinct luminescence. Apatite in the altered rocks had distinct compositions of Cl, Mn, Fe, Mg, Sr, and Pb and a slightly different delta O18 value, suggesting mobilisation during hydrothermal alteration. This suggests that apatite texture, chemistry, and isotopes can be modified by hydrothermal fluids. Altered and magmatic apatite had comparable concentrations of REEs, Y, U,, Th, and Zr and also Nd isotope signatures, indicating retention of some primary magmatic characteristics during alteration. The study showed that cathodoluminescence, elemental compositions, and Sr-O isotope signatures in apatite can be modified during hydrothermal alteration, whereas other components (REE, Y, U, Th, and Zr) and the Nd isotope composition are preserved. It is concluded that these features can be used to constrain the origin, chemistry, and evolution of the primary magma and ore-forming hydrothermal fluids.

Pre- and syn-mineralised rocks at the Black Mountain porphyry Cu-Au deposit preserve magmatic and hydrothermal minerals spanning the complete paragenesis of the deposit. Variation in Sr isotope profiles suggest there are two types of plagioclase grains present at the deposit: Type-I show homogeneous Sr isotope compositions, indicating crystallisation from a stable felsic magma chamber; Type-II have a wider range of Sr isotope compositions, consistent with recharge of mafic and/or felsic magmas. Late magmatic titanite shows slightly increased Nb/Ta but decreased Zr/Hf and Y/Ho values. Hydrothermal titanite and epidote have ratios similar to those in the whole rock. These patterns reflect crystallisation effects imposed during the magmatic stage but an absence of differentiation during the hydrothermal stage. The consistent gradual decrease in total rare earth element, Y, Zr, and U contents in titanite and epidote from early to late stages indicates the effect of hydrothermal fluid evolution with decreasing temperature. The variation of 87Sr/86Sr values indicates the addition of mafic magma-derived fluid into the felsic magma-derived fluid. One extra source of fluid (probably derived from wall-rock limestone) was required to generate the highly radiogenic 87Sr/86Sr values of some epidote. It is concluded that in situ elemental and Sr isotope variation in minerals from different paragenetic stages can be used to interpret formation process and source for both magmas and hydrothermal fluids., Pre- and syn-mineralised rocks at the Black Mountain porphyry Cu-Au deposit preserve magmatic and hydrothermal minerals spanning the complete paragenesis of the deposit. Variation in Sr isotope profiles suggest there are two types of plagioclase grains present at the deposit: Type-I show homogeneous Sr isotope compositions, indicating crystallisation from a stable felsic magma chamber; Type-II have a wider range of Sr isotope compositions, consistent with recharge of mafic and/or felsic magmas. Late magmatic titanite shows slightly increased Nb/Ta but decreased Zr/Hf and Y/Ho values. Hydrothermal titanite and epidote have ratios similar to those in the whole rock. These patterns reflect crystallisation effects imposed during the magmatic stage but an absence of differentiation during the hydrothermal stage. The consistent gradual decrease in total rare earth element, Y, Zr, and U contents in titanite and epidote from early to late stages indicates the effect of hydrothermal fluid evolution with decreasing temperature. The variation of 87Sr/86Sr values indicates the addition of mafic magma-derived fluid into the felsic magma-derived fluid. One extra source of fluid (probably derived from wall-rock limestone) was required to generate the highly radiogenic 87Sr/86Sr values of some epidote. It is concluded that in situ elemental and Sr isotope variation in minerals from different paragenetic stages can be used to interpret formation process and source for both magmas and hydrothermal fluids.

Major research discoveries have included numerous particulate-poor, gas-rich (CO2-CH4) hydrothermal plumes emanating from arc-front volcanoes, actively forming porphyry-copper-gold style mineralisation, and new backarc spreading systems erupting alkali basalt-trachyandesite magmas. Key goals of the studies have been identification of modern analogues to ancient volcanogenic massive sulphide ore bodies, and quantification of the volatile fluxes though supra-subduction zone systems., Major research discoveries have included numerous particulate-poor, gas-rich (CO2-CH4) hydrothermal plumes emanating from arc-front volcanoes, actively forming porphyry-copper-gold style mineralisation, and new backarc spreading systems erupting alkali basalt-trachyandesite magmas. Key goals of the studies have been identification of modern analogues to ancient volcanogenic massive sulphide ore bodies, and quantification of the volatile fluxes though supra-subduction zone systems.

This report is a review of the current status of the various techniques used to monitor the near-surface environment above a GCS (geological CO2 storage) project, with specific reference to Barrow Island. The review covers a range of environments, broadly sub-divided into near-surface atmospheric, soil gas, groundwater and the near-shore and marine environment. For each environment the key parameters likely to be indicative of migrant CO2 (including CO2 directly) are considered. The techniques covered include geochemical, isotopic, geophysical, microbial, marine and near-surface atmospheric. For each technique what parameters are measured, the effectiveness of each, the stage of development, relative cost and footprint and some of the practicalities of implementing such a system on Barrow Island are described. Included in the report is a review of where these technologies are being deployed or researched at different GCS sites around the world. There are few commercial scale GCS projects, the majority are demonstration scale and the monitoring techniques being applied are as much for technology development as leakage detection. One of the major difficulties with a near-surface environmental monitoring system is the need to be able to demonstrate detectability of a small or non-existent signal within an inherently noisy system. There are potentially many ways to detect CO2 or parameters affected by its presence; however, they need to be coupled with a method to quantitatively distinguish them from the background environmental or anthropogenic variability. For each of the technologies reviewed, three common themes emerged. The first is that no single technology is likely to meet all of the monitoring objectives. The need for targeted, high intensity monitoring sites at high risk locations should be coupled with lower resolution, larger scale monitoring at low risk sites. There are technologies that are appropriate for each of these; small scale (centimetre to metres)

Two drill core samples of haematite/goethite from the Robe River channel iron ore deposits (CID) were dated using (U-Th)/He methods in order to constrain the timing of iron oxide formation and thereby provide a temporal context for CID genesis. (U-Th)/He ages (He ages) from these samples range from late Oligocene to Late Miocene and, despite a high degree of scatter, corroborate relationships expected from the internal ooidal stratigraphy. For individual ooids, the ages from haematitic core are older than or indistinguishable from the ages of the surrounding goethitic cortex. The goethitic cortices are, in turn, older than the ferruginised wood fragments recovered from the cementing goethitic matrix. The data suggest the following succession of ore formation phases: haematitic cores in ooids of both samples formed in the Early to Middle Miocene; goethitic cortices of both samples formed in the late Middle to early Late Miocene, the age of goethite cortex formation regardless of depth in the core, which does not support the top-down infill genetic model proposed by Heim et al (2006); and wood fragments forming a prominent component of the matrix were ferruginised during the Late Miocene. Thus the data suggest that the unique environmental conditions for the CID formation existed during the Miocene. A methodological implication is that the temperature utilised for He extraction from iron oxides has a critical impact on the mobility of parent nuclides; the typical 1 100 degree C laser heating used for crystalline minerals like apatite or zircon induces loss of U and Th and results in erroneously old ages., Two drill core samples of haematite/goethite from the Robe River channel iron ore deposits (CID) were dated using (U-Th)/He methods in order to constrain the timing of iron oxide formation and thereby provide a temporal context for CID genesis. (U-Th)/He ages (He ages) from these samples range from late Oligocene to Late Miocene and, despite a high degree of scatter, corroborate relationships expected from the internal ooidal stratigraphy. For individual ooids, the ages from haematitic core are older than or indistinguishable from the ages of the surrounding goethitic cortex. The goethitic cortices are, in turn, older than the ferruginised wood fragments recovered from the cementing goethitic matrix. The data suggest the following succession of ore formation phases: haematitic cores in ooids of both samples formed in the Early to Middle Miocene; goethitic cortices of both samples formed in the late Middle to early Late Miocene, the age of goethite cortex formation regardless of depth in the core, which does not support the top-down infill genetic model proposed by Heim et al (2006); and wood fragments forming a prominent component of the matrix were ferruginised during the Late Miocene. Thus the data suggest that the unique environmental conditions for the CID formation existed during the Miocene. A methodological implication is that the temperature utilised for He extraction from iron oxides has a critical impact on the mobility of parent nuclides; the typical 1 100 degree C laser heating used for crystalline minerals like apatite or zircon induces loss of U and Th and results in erroneously old ages.

Recent advances in exploration for volcanic-hosted Cu-Zn in Western Australia have included the discovery of Au-rich lenses at depths of as much as 1 300 m through innovative geology and drilling campaigns and the successful use of electromagnetic techniques. However, differentiating between conductive black shales and massive sulphides through conductive overburden remains a major challenge for geophysical exploration. Advances in airborne hyperspectral surveying techniques have identified regional alteration patterns that represent potential targets. Significant progress in the exploration and understanding of modern seafloor hydrothermal systems is also being applied to exploration for ancient massive sulphides in Australia. The volume brings together a diverse range of expertise in chapters on these and other exploration techniques and on the geology and mineralisation of particular massive sulphide deposits or hydrothermal systems in Western Australia and in Canadian and Papua New Guinean provinces., Recent advances in exploration for volcanic-hosted Cu-Zn in Western Australia have included the discovery of Au-rich lenses at depths of as much as 1 300 m through innovative geology and drilling campaigns and the successful use of electromagnetic techniques. However, differentiating between conductive black shales and massive sulphides through conductive overburden remains a major challenge for geophysical exploration. Advances in airborne hyperspectral surveying techniques have identified regional alteration patterns that represent potential targets. Significant progress in the exploration and understanding of modern seafloor hydrothermal systems is also being applied to exploration for ancient massive sulphides in Australia. The volume brings together a diverse range of expertise in chapters on these and other exploration techniques and on the geology and mineralisation of particular massive sulphide deposits or hydrothermal systems in Western Australia and in Canadian and Papua New Guinean provinces.

The Black Mountain porphyry Cu-Au deposit in the Baguio district, Northern Luzon, is associated with late Miocene to Pliocene intrusive rocks that retain primary crystallisation signatures, providing an excellent natural laboratory to study the details of magma chamber processes. Each igneous phase contains disequilibrium textures, including resorptive textures in plagioclase and distinct core rim textures in amphibole. High crystallisation temperatures and pressures in felsic (ca. 880 degrees C, 2.8 kbar) and mafic (ca. 1 030 degrees C, 7.7 kbar) rocks recorded by amphibole phenocrysts reflect crystallisation in the magma chamber. Amphibole in felsic rocks aged 6.39 ± 0.49 to 2.83 ± 0.23 Ma have similar crystallisation temperatures and pressures, suggesting a long-lived and hot felsic magma chamber under the Black Mountain deposit. The common occurrence of rounded or elongated sulphide inclusions in the megacrystic amphibole from the mafic rocks (2.81 ± 0.15 Ma) suggests a greater enrichment of Cu in mafic rocks relative to the ore-forming porphyries (2.91-2.83 Ma). This is also consistent with higher Cu contents (3.4 ± 0.9 ppm) in the megacrystic amphibole from the mafic rocks relative to amphibole in felsic rocks (1.0 ± 0.2 ppm) and may indicate up to 3.4 times higher Cu in the mafic magma relative to felsic magma. Therefore, large-scale mafic magma recharge (particularly at 2.8 Ma), likely introduced ore-forming metals to the long-lived felsic magma chamber, further contributing to the fertility of the felsic rocks and ultimately to Cu-Au mineralisation at the Black Mountain deposit., The Black Mountain porphyry Cu-Au deposit in the Baguio district, Northern Luzon, is associated with late Miocene to Pliocene intrusive rocks that retain primary crystallisation signatures, providing an excellent natural laboratory to study the details of magma chamber processes. Each igneous phase contains disequilibrium textures, including resorptive textures in plagioclase and distinct core rim textures in amphibole. High crystallisation temperatures and pressures in felsic (ca. 880 degrees C, 2.8 kbar) and mafic (ca. 1 030 degrees C, 7.7 kbar) rocks recorded by amphibole phenocrysts reflect crystallisation in the magma chamber. Amphibole in felsic rocks aged 6.39 ± 0.49 to 2.83 ± 0.23 Ma have similar crystallisation temperatures and pressures, suggesting a long-lived and hot felsic magma chamber under the Black Mountain deposit. The common occurrence of rounded or elongated sulphide inclusions in the megacrystic amphibole from the mafic rocks (2.81 ± 0.15 Ma) suggests a greater enrichment of Cu in mafic rocks relative to the ore-forming porphyries (2.91-2.83 Ma). This is also consistent with higher Cu contents (3.4 ± 0.9 ppm) in the megacrystic amphibole from the mafic rocks relative to amphibole in felsic rocks (1.0 ± 0.2 ppm) and may indicate up to 3.4 times higher Cu in the mafic magma relative to felsic magma. Therefore, large-scale mafic magma recharge (particularly at 2.8 Ma), likely introduced ore-forming metals to the long-lived felsic magma chamber, further contributing to the fertility of the felsic rocks and ultimately to Cu-Au mineralisation at the Black Mountain deposit.

The Triassic Pulang porphyry Cu-Au deposit, located in the South Yidun terrane, is the oldest and one of the largest porphyry deposits in the southeastern Tibetan Plateau. Mineralisation occurs mostly in the potassic alteration zone of the Pulang intrusive complex. U-Pb-He triple dating, namely apatite (U-Th)/He, zircon U-Pb, and zircon (U-Th)/He dating, together with inverse thermal modelling, reveals that the Pulang complex was emplaced at a palaeodepth of 5.0-6.5 km at 215 ± 2 Ma. The deep-level emplacement of the complex, coupled with the episodic replenishment of the magma chamber, gave rise to the establishment of a prolonged magmatic-hydrothermal system at Pulang. Although a range of single-grain zircon and apatite (U-Th)/He ages were obtained on each sample, the weighted mean zircon and apatite (U-Th)/He ages vary systematically with elevation, defining a multistage cooling/denudation history at Pulang. Specifically, three phases of cooling were recognised from inverse thermal modelling. Overall, results indicate that the Pulang complex experienced two stages of exhumation at 33 to 45 m/m.y. and 5 to 17 m/m.y. Based on these data, it is estimated that approximately 558-1 099-m thickness of materials have been removed from the Pulang complex during uplift and erosion, including a large volume of ore. The long time span (more than 50 m.y.) of extremely slow cooling and erosion at Pulang could be related to the formation and preservation of a peneplain on the southeastern Tibetan Plateau since the Late Cretaceous. A relict peneplain thus signifies a favourable tectonic environment for the preservation of ancient porphyry systems worldwide., The Triassic Pulang porphyry Cu-Au deposit, located in the South Yidun terrane, is the oldest and one of the largest porphyry deposits in the southeastern Tibetan Plateau. Mineralisation occurs mostly in the potassic alteration zone of the Pulang intrusive complex. U-Pb-He triple dating, namely apatite (U-Th)/He, zircon U-Pb, and zircon (U-Th)/He dating, together with inverse thermal modelling, reveals that the Pulang complex was emplaced at a palaeodepth of 5.0-6.5 km at 215 ± 2 Ma. The deep-level emplacement of the complex, coupled with the episodic replenishment of the magma chamber, gave rise to the establishment of a prolonged magmatic-hydrothermal system at Pulang. Although a range of single-grain zircon and apatite (U-Th)/He ages were obtained on each sample, the weighted mean zircon and apatite (U-Th)/He ages vary systematically with elevation, defining a multistage cooling/denudation history at Pulang. Specifically, three phases of cooling were recognised from inverse thermal modelling. Overall, results indicate that the Pulang complex experienced two stages of exhumation at 33 to 45 m/m.y. and 5 to 17 m/m.y. Based on these data, it is estimated that approximately 558-1 099-m thickness of materials have been removed from the Pulang complex during uplift and erosion, including a large volume of ore. The long time span (more than 50 m.y.) of extremely slow cooling and erosion at Pulang could be related to the formation and preservation of a peneplain on the southeastern Tibetan Plateau since the Late Cretaceous. A relict peneplain thus signifies a favourable tectonic environment for the preservation of ancient porphyry systems worldwide.

Around 30 Western Australian deposits and prospects (including the various Golden Grove deposits) are listed with their age, terrain, year of discovery, depth, discovery methods, tonnages, grades and literature references. Lead isotopic signatures and lithogeochemistry are discussed and the Horseshoe, Mount Gibson and Nimbus deposits described including the economic benefits of their deep weathering and supergene enrichment. Almost all deposits, though with a few notable exceptions, have had some form of Fe-rich gossan at surface, while the discovery of Jaguar at 450 m depth has improved perceptions of the effectiveness of electromagnetic exploration techniques. Homogeneous Pb isotope signatures signify discrete metallogenic events, especially in the Murchison and Eastern Goldfields terranes, and have potential for screening alteration and geochemical targets. Further surface discoveries are still likely as well as deeper brownfield ones, but better understanding of weathering and transport is needed for greenfield exploration., Around 30 Western Australian deposits and prospects (including the various Golden Grove deposits) are listed with their age, terrain, year of discovery, depth, discovery methods, tonnages, grades and literature references. Lead isotopic signatures and lithogeochemistry are discussed and the Horseshoe, Mount Gibson and Nimbus deposits described including the economic benefits of their deep weathering and supergene enrichment. Almost all deposits, though with a few notable exceptions, have had some form of Fe-rich gossan at surface, while the discovery of Jaguar at 450 m depth has improved perceptions of the effectiveness of electromagnetic exploration techniques. Homogeneous Pb isotope signatures signify discrete metallogenic events, especially in the Murchison and Eastern Goldfields terranes, and have potential for screening alteration and geochemical targets. Further surface discoveries are still likely as well as deeper brownfield ones, but better understanding of weathering and transport is needed for greenfield exploration.

Past trends are illustrated by graphs of copper and zinc prices since 1955 that show the sharp decline in real Cu prices from 1965 onwards, a bar chart of Australian base-metal exploration expenditure from 1980-81 to 2002-03 and a list of Australian discoveries from 1871 to 2003 with metals, deposit types, exploration methods and references. The objectives and expenditure on research and development of the various Australian cooperative research centres in exploration, mining and metallurgy are listed and CSIRO's research and development in base-metal exploration for copper-zinc deposits in the Yilgarn craton is outlined. Accurate data with which to quantify the R&D effort and to evaluate its economic benefits are difficult to assemble. The trend in base-metal exploration research is towards a more holistic and integrated approach, determining the types of ore systems that best meet industry needs and increasing understanding of how they are formed and preserved as well as how they can be detected in a variety of terrains., Past trends are illustrated by graphs of copper and zinc prices since 1955 that show the sharp decline in real Cu prices from 1965 onwards, a bar chart of Australian base-metal exploration expenditure from 1980-81 to 2002-03 and a list of Australian discoveries from 1871 to 2003 with metals, deposit types, exploration methods and references. The objectives and expenditure on research and development of the various Australian cooperative research centres in exploration, mining and metallurgy are listed and CSIRO's research and development in base-metal exploration for copper-zinc deposits in the Yilgarn craton is outlined. Accurate data with which to quantify the R&D effort and to evaluate its economic benefits are difficult to assemble. The trend in base-metal exploration research is towards a more holistic and integrated approach, determining the types of ore systems that best meet industry needs and increasing understanding of how they are formed and preserved as well as how they can be detected in a variety of terrains.

Case studies of Grasberg, Batu Hijau and Ciemas in Indonesia used multiple geochronometry techniques to test the hypothesis that rapidly cooled porphyry deposits display higher copper-grade hypogene ore shells than their more slowly cooled counterparts. Grasberg, in Irian Jaya, cooled extremely rapidly at a rate of more than 1 000 degrees C/m.y., due to emplacement within 1 km of the surface. Batu Hijau, in Nusa Tengarra, cooled more slowly at around 450 degrees C/m.y. while the sub-economic Ciemas prospect, in Java, cooled at only 60 degrees C/m.y. and was only exhumed from depths of 5-8 km during the Miocene. At such depths it would have been hard for high Cu grades to have been generated by a thermally driven deposition process, as the original magmatic Cu would have been homogeneously distributed over a larger volume of rock., Case studies of Grasberg, Batu Hijau and Ciemas in Indonesia used multiple geochronometry techniques to test the hypothesis that rapidly cooled porphyry deposits display higher copper-grade hypogene ore shells than their more slowly cooled counterparts. Grasberg, in Irian Jaya, cooled extremely rapidly at a rate of more than 1 000 degrees C/m.y., due to emplacement within 1 km of the surface. Batu Hijau, in Nusa Tengarra, cooled more slowly at around 450 degrees C/m.y. while the sub-economic Ciemas prospect, in Java, cooled at only 60 degrees C/m.y. and was only exhumed from depths of 5-8 km during the Miocene. At such depths it would have been hard for high Cu grades to have been generated by a thermally driven deposition process, as the original magmatic Cu would have been homogeneously distributed over a larger volume of rock.

Gold mineralisation at Freegold Mountain is temporally and spatially related to Late Cretaceous rhyolitic volcanism. Gold-bearing veins are high-grade, low-tonnage deposits with grades ranging from 0.4 to 1.0 oz/t. Petrographic and fluid inclusion studies suggest that the Laforma vein can be divided into three zones: deep ore, boiling and upper ore. The mineralogy shows vertical zonation: base metal sulphides occur below the boiling zone; tennantite is present only above the boiling zone, and pyrite and arsenopyrite occur throughout the mine depth. The deposit was an active near-surface hydrothermal system operating during the Late Cretaceous. Although the deep ore waters have a meteoric water isotopic composition, the temporal and spatial relationship between high-level rhyolite dykes, hypabyssal plutons and gold deposits in the area, the relatively high CO2 contents of the hydrothermal fluid, and the occurrence of tourmaline are consistent with a magmatic contribution to the hydrothermal system., Gold mineralisation at Freegold Mountain is temporally and spatially related to Late Cretaceous rhyolitic volcanism. Gold-bearing veins are high-grade, low-tonnage deposits with grades ranging from 0.4 to 1.0 oz/t. Petrographic and fluid inclusion studies suggest that the Laforma vein can be divided into three zones: deep ore, boiling and upper ore. The mineralogy shows vertical zonation: base metal sulphides occur below the boiling zone; tennantite is present only above the boiling zone, and pyrite and arsenopyrite occur throughout the mine depth. The deposit was an active near-surface hydrothermal system operating during the Late Cretaceous. Although the deep ore waters have a meteoric water isotopic composition, the temporal and spatial relationship between high-level rhyolite dykes, hypabyssal plutons and gold deposits in the area, the relatively high CO2 contents of the hydrothermal fluid, and the occurrence of tourmaline are consistent with a magmatic contribution to the hydrothermal system.

Age relationships determined for apatite by fission-track and (U-Th)/He methods can be used to record the low-temperature history of a magmatic-hydrothermal system cooling through the respective closure temperatures of around 125 and 75 degrees C. Data for Chuquicamata indicate that the deposit's missing portion should have been located at least 600 m above the present ground surface on the western side of the West fault, at a current elevation of 3 600 m above sea level. Because nearby parts of the fault zone do not attain this elevation, it is presumed that the orebody has been removed by erosion. The Mansa Mina deposit, at 2 400 m above sea level, cannot be a shallow, high-sulphidation portion of the Chuquicamata deposit. If deeper parts of Mansa Mina are present east of the fault, they should be at about 1 800 m. The rapid cooling of the Chuquicamata intrusive complex implies emplacement at less than 4 km depth, whereas the Fortuna complex to the west of the fault was emplaced at a deeper crustal level., Age relationships determined for apatite by fission-track and (U-Th)/He methods can be used to record the low-temperature history of a magmatic-hydrothermal system cooling through the respective closure temperatures of around 125 and 75 degrees C. Data for Chuquicamata indicate that the deposit's missing portion should have been located at least 600 m above the present ground surface on the western side of the West fault, at a current elevation of 3 600 m above sea level. Because nearby parts of the fault zone do not attain this elevation, it is presumed that the orebody has been removed by erosion. The Mansa Mina deposit, at 2 400 m above sea level, cannot be a shallow, high-sulphidation portion of the Chuquicamata deposit. If deeper parts of Mansa Mina are present east of the fault, they should be at about 1 800 m. The rapid cooling of the Chuquicamata intrusive complex implies emplacement at less than 4 km depth, whereas the Fortuna complex to the west of the fault was emplaced at a deeper crustal level.

In Luise Harbor, sedimentary and hydrothermal processes have combined to form submarine lenticular deposits, several cm thick and several m wide, of colloform Fe sulphide, largely marcasite and pyrite, centred around hydrothermal vents. The gases associated with their formation are likely to have attained gas-liquid equilibrium in an underlying hydrothermal system at 250-350 degrees C. Contact with aerated sea water has led to oxidation of H2S and H2 and the generation of comparatively acid and oxidising conditions conducive to the alteration of Fe-bearing minerals in the first few metres of the sediment. This process is also likely to have controlled the geometry of the deposits. Alternating deposition of pyrite and marcasite is likely to have resulted from temporal variations in local acidity, in response to variations in the exposure of rising hydrothermal fluids to aerated sea water. There is no evidence for deep hydrothermal circulation of meteoric or sea water. The processes are therfore probably identical to those producing subaerial acid sulphate hot springs., In Luise Harbor, sedimentary and hydrothermal processes have combined to form submarine lenticular deposits, several cm thick and several m wide, of colloform Fe sulphide, largely marcasite and pyrite, centred around hydrothermal vents. The gases associated with their formation are likely to have attained gas-liquid equilibrium in an underlying hydrothermal system at 250-350 degrees C. Contact with aerated sea water has led to oxidation of H2S and H2 and the generation of comparatively acid and oxidising conditions conducive to the alteration of Fe-bearing minerals in the first few metres of the sediment. This process is also likely to have controlled the geometry of the deposits. Alternating deposition of pyrite and marcasite is likely to have resulted from temporal variations in local acidity, in response to variations in the exposure of rising hydrothermal fluids to aerated sea water. There is no evidence for deep hydrothermal circulation of meteoric or sea water. The processes are therfore probably identical to those producing subaerial acid sulphate hot springs.

The thermal and exhumation histories of magmatic ore deposits are quantified by combining numerical modelling techniques with (U-Th)/He thermochronometry and U-Pb geochronology data. By integrating magmatic and exhumation cooling models for igneous intrusions and constraining the time-temperature histories with radiometric age data, it is possible to construct complete geological histories for magmatic-hydrothermal systems. The model was tested using thermochronology and geochronology data from the Sar Cheshmeh porphyry Cu deposit in Iran., The thermal and exhumation histories of magmatic ore deposits are quantified by combining numerical modelling techniques with (U-Th)/He thermochronometry and U-Pb geochronology data. By integrating magmatic and exhumation cooling models for igneous intrusions and constraining the time-temperature histories with radiometric age data, it is possible to construct complete geological histories for magmatic-hydrothermal systems. The model was tested using thermochronology and geochronology data from the Sar Cheshmeh porphyry Cu deposit in Iran.

Sampling and trace element analysis of vegetation growing over and around Au deposits on Lihir and Simberi Islands was conducted to assess the potential application of biogeochemical exploration techniques in densely forested tropical regions. The tree Astronidium palauense was used for sampling. Soil sampling was also carried out for correlation of the results. A highly significant correlation was found between the Au and As concentrations in bark and Au in soils. The spatial distribution of Au and As enrichment in trees over the Simberi Island deposits were found to delineate deep ore zones more closely than the geochemical anomalies found in the soil. The method was found to be very successful and cost-effective, with low equipment requirements and rapid turnaround of results. The technique should be applicable throughout the tropical southwest Pacific due to the widespread distribution of Astronidium palauense., Sampling and trace element analysis of vegetation growing over and around Au deposits on Lihir and Simberi Islands was conducted to assess the potential application of biogeochemical exploration techniques in densely forested tropical regions. The tree Astronidium palauense was used for sampling. Soil sampling was also carried out for correlation of the results. A highly significant correlation was found between the Au and As concentrations in bark and Au in soils. The spatial distribution of Au and As enrichment in trees over the Simberi Island deposits were found to delineate deep ore zones more closely than the geochemical anomalies found in the soil. The method was found to be very successful and cost-effective, with low equipment requirements and rapid turnaround of results. The technique should be applicable throughout the tropical southwest Pacific due to the widespread distribution of Astronidium palauense.