Mineral exploration is a risky business due to the inherent geological and economic uncertainties that accompany the discovery and exploitation of mineral deposits. Consequently, the ability to quantify the risk in terms of the economic consequences of exploration can lead to improved decision-making and more profitable exploration. Quantifying economic risk in exploration requires an understanding of the economic value of exploration. This in turn requires information about possible numbers and sizes of undiscovered deposits, in addition to the economics associated with the discovery, delineation and mining of these undiscovered deposits. A method for quantifying exploration risk based on these requirements is detailed here and demonstrated via a four part case study, which examines the economic risk associated with exploration for undiscovered porphyry Cu and VHMS deposits in the Yarrol region (SE Queensland) and their contained copper and gold resources. The first part of the case study outlines the study rationale and background, and presents descriptive geological models for eastern Australian porphyry Cu and VHMS deposits. The deposit models were then used to delineate permissive tracts for each deposit type. In the second part, prospectivity modelling was carried out on a sub-block basis using a multivariate Bayesian weighted probabilistic neural network (PNN). The PNN was used to integrate geological data and estimate the conditional probability that a sub-block belonged to one of twelve classes, defined by a set of mineral deposit types. Prior to modelling, the geological data used in the PNN underwent preparation that involved quality control and conversion to a set of geological themes which accentuate characteristics associated with mineralisation in the Yarrol region. To compensate for inherent imprecision in the data, fuzzy set algorithms were used to sample the themes prior to PNN modelling. The algorithms were designed to handle the line, polygon and raster data using fuzzy membership functions and fuzzy entropy. The final PNN input vector contained 50 fuzzy variables, describing lithology, structure and geophysics. Because the PNN is an intrinsic classifier, which uses the training samples as nodes in the network, independent validation with classified samples not used in training is required to appropriately gauge performance. To overcome the issue of excluding classified samples from training, multiple PNN tests were carried out using randomly selected 70:30, training to validation, splits of the classified samples. In the case study 100 PNN tests were carried out and independent validation recorded a mean of 84 % correct classifications, with 4 % standard deviation. After each PNN test, unclassified subblocks covering the case study region were classified by the trained PNN and the results used to map the prospectivity of the region. The prospectivity maps highlighted both geological features and areas prospective for the different mineral classes. A total of 26 areas were modelled as being prospective for porphyry Cu and VHMS deposits of which 6 corresponded to the deposits used in training. In the third part of the case study, estimates of the undiscovered mineral resources in the Yarrol region were modelled using a Monte Carlo simulation. Simulation involved generating grade and tonnage models for eastern Australian porphyry Cu and VHMS deposits, and estimating the numbers of undiscovered deposits in the region using the probabilities generated by prospectivity modelling. Models and estimates were converted to cumulative distribution functions using histogram smoothing and normal score transformation. This approach differs from the documented proportional method and the benefits of using the new approach, such as better fitting and more representative grade and tonnage models, are shown. Results of the mineral resource simulation found that the simulated Cu resources in undiscovered VHMS deposits were much smaller than those estimated in undiscovered porphyry Cu deposits (i.e. Kt rather than Mt) while the probabilities for VMHS resources were an order of magnitude higher. For example, there was a 30 % chance of 100 Kt or more Cu in a VHMS deposit compared to a 2 % chance of 1 Mt or more Cu in an undiscovered porphyry Cu deposit. However, in the case of undiscovered Au resources the VHMS deposits had similar resource sizes to the porphyry Cu deposits but the probabilities were much higher for VHMS deposits (e.g. there was a 2 % chance of 5 Moz of Au, or more, in a porphyry Cu deposit and a 15 % chance of 5 Moz of Au, or more, in a VHMS deposit). These results reflected the high probability (i.e. 92 % chance) for zero undiscovered porphyry deposits and much higher Au grades in the VHMS deposits. In the final part of the case study the mid-term value (mine value) and the long-term value of exploration were estimated in terms of NPV and RoR. The mid-term values were calculated using mining cost models based on mining capacity calculated via Taylor’s rule. A new approach using variable mine capacity and scheduled development costs is presented and demonstrated. Results for the mid-term values indicate that economic risk was lower for resources in VHMS deposits. For example, the expected NPV1 for an undiscovered porphyry Cu deposit was $ 27 million compared to $ 53 million for a VHMS deposit and the probabilities of these occurring were 0.03 (a 3 % chance) and 0.2 (a 20 % chance), respectively. However, a risk assessment using utilities for the mid-term NPV indicated that a risk taker would favour porphyry Cu exploration because of the possibility for extremely large porphyry deposits. The long term value of exploration was estimated using an exploration model that randomly sampled both a discovery cost model (which mapped the cost of exploration to the probability of a discovery) and the simulated undiscovered resources (which act as possible targets for exploration). A range of exploration budgets were examined for both deposit types. Results demonstrated that smaller budgets had higher risk because they resulted in longer discovery times which reduce profits and increased the chance of missed economic opportunities due to Gambler’s Ruin (e.g. a budget of $ 2 million/year had a 50 % of Gambler’s Ruin after 6 years, whereas a $ 6 million/year budget had only a 3 % chance). It was also shown that economic returns levelled out as the budget increased because the increased chance of making a discovery is balanced out by higher exploration costs and lower discounted returns for the discovered deposit. Small and large exploration budgets were examined in detail and it was shown that in both cases exploration for VHMS deposits has less risk. For example1, a $ 2 million/year exploration budget targeting VHMS deposits had a 13 % chance of returning a NPV of $ 50 million, or greater, whereas the same budget targeting porphyry Cu deposits had only a 3 % chance of returning the same NPV, or greater. The RoR results displayed a similar outcome. The case study concluded with a sensitivity study examining the effects that variation in Cu price, Au price, exchange rate, mean exploration cost, development costs and operating costs has on the long-term economic values for both deposits types. In the case of porphyry Cu deposits both the NPV and RoR were highly sensitive to variations in Cu price and to a lesser extent operating and development costs. The long-term value of VHMS exploration was highly sensitive to the Cu price, Au price and the exchange rate. (the latter related to commodity prices and mining costs). It is recommended that future prospectivity studies could include geochemical and alteration data to assist in modelling the location of an undiscovered deposit. The use of historical exploration data (e.g. drill hole density maps) in the prospectivity modelling process would also help to identify areas that either lack detailed exploration or have been extensively explored. The use of more localised mining costs models, incorporating real Australian mine development and production costs is also recommended. Probably the most important recommendation deals with improvements to the exploration model such as the use of more accurate exploration costs and staged exploration processes. It is also suggested that other economic risk analysis techniques (i.e. portfolio analyses, capital asset fixing etc.) could be used to model the exploration process.

Assessed values from the files of the New Zealand Valuation Department are the main dependent variable in this research. Unimproved values for individual parcels of land are aggregated into 301 areal units and multiple regression analysis is used to explain the spatial pattern of values in 1970. Temporal variations in the pattern of unimproved values and the influence of increasing values on the distribution of agricultural land use are also explored. The study area comprise most of the territory over which the Auckland Regional Authority has jurisdiction. Both 'accessibility' and 'area-characteristics' models are used to interpret the pattern of unimproved values in 1970. In general the area-characteristics models are the most successful, but higher R2 values are achieved with hybrid models that combine road distance from the CBD modified by travel time, with such characteristics of areas as size of holding, land use, and terrain. In analysing the pattern of values in 1955, 1960, and 1365 compared with 1970, the statistical contribution of road distance to the CBD compared with terrain is stressed. Distance becomes a more effective predictor of value through time, while the explanation contributed by terrain-characteristics deteriorates. The large increases in the value of land that the region has experienced during the period studied are shown to have had less influence on the distribution of agriculture than has been suggested in other contexts. The main reasons advanced for the resilience of agriculture is its ability to compete for land, which is influenced by legislation allowing the postponement of rates (territorial local authority land taxes) on some agricultural land. The means by which quotas are allocated to farmers supplying liquid milk, and the marketing of fruit and vegetables direct to consumers, are also important in maintaining agricultural land in production.

Assessed values from the files of the New Zealand Valuation Department are the main dependent variable in this research. Unimproved values for individual parcels of land are aggregated into 301 areal units and multiple regression analysis is used to explain the spatial pattern of values in 1970. Temporal variations in the pattern of unimproved values and the influence of increasing values on the distribution of agricultural land use are also explored. The study area comprise most of the territory over which the Auckland Regional Authority has jurisdiction. Both 'accessibility' and 'area-characteristics' models are used to interpret the pattern of unimproved values in 1970. In general the area-characteristics models are the most successful, but higher R2 values are achieved with hybrid models that combine road distance from the CBD modified by travel time, with such characteristics of areas as size of holding, land use, and terrain. In analysing the pattern of values in 1955, 1960, and 1365 compared with 1970, the statistical contribution of road distance to the CBD compared with terrain is stressed. Distance becomes a more effective predictor of value through time, while the explanation contributed by terrain-characteristics deteriorates. The large increases in the value of land that the region has experienced during the period studied are shown to have had less influence on the distribution of agriculture than has been suggested in other contexts. The main reasons advanced for the resilience of agriculture is its ability to compete for land, which is influenced by legislation allowing the postponement of rates (territorial local authority land taxes) on some agricultural land. The means by which quotas are allocated to farmers supplying liquid milk, and the marketing of fruit and vegetables direct to consumers, are also important in maintaining agricultural land in production.

Although snow petrels are ubiquitous around the Antarctic, population estimates of this “not so charismatic” top predator are generally limited. Such information is highly valuable for the monitoring and management of Antarctic and Southern Ocean ecosystems, especially in a climate change context. There is a need to complement long–term temporal demographic information obtained at a limited number of monitoring sites with spatial distribution data. Systematic surveys of snow petrels and Wilson’s storm petrels were undertaken at Casey (2002-2003) and Mawson (2004-2005) in order to provide better regional population estimates and test the performance of predictive distribution models based on topographic and substrate variables for refining such estimates. As habitat selection modelling is rarely used in Antarctic regions, methodological developments focus on dealing with the peculiarities of a semi-colonial hollow-nesting species, testing habitat selection modelling approaches and comparing the output of four types of models (Generalized Linear and Generalized Additive Models, Classification Trees and Ecological Niche Factor Analysis) across a range of scales. Snow petrel nest distribution was directly related to the nature of the rock substrate and to major topographic/geomorphological parameters such as hill slope and the direction of the prevailing winds. Model performance varied with the scale at which models were implemented, suggesting that nest selection processes happen predominantly at the habitat unit and individual nest scales. Further study at the nest scale highlighted that the influence of biotic related parameters such as conspecific attraction (modelled as autocorrelation due to coloniality) may be of lesser influence than selection based on individual nest quality. An alternative modelling method, ENFA, which creates environmental envelopes for the niche of the species with presence data only was identified as valuable for Antarctic data sets, which often lack comprehensive records of species absence. The validation of the models created at Casey with nest data collected in the Mawson region returned satisfactory prediction rates in two different habitat types, coastal islands and inland mountains, suggesting that it may be possible to predict snow petrel distribution across East Antarctica using remotely sensed information on topography and geomorphology, for example high-resolution aerial photography to guide in the design of and complement ground surveys. Similar modelling procedures applied to Wilson’s storm petrels produced more mitigated results and selection for this species appeared to be based principally on nest microhabitat characteristics. However, modelling provided useful information on the large-scale habitat preferences and ecological requirements of both species

Assessed values from the files of the New Zealand Valuation Department are the main dependent variable in this research. Unimproved values for individual parcels of land are aggregated into 301 areal units and multiple regression analysis is used to explain the spatial pattern of values in 1970. Temporal variations in the pattern of unimproved values and the influence of increasing values on the distribution of agricultural land use are also explored. The study area comprise most of the territory over which the Auckland Regional Authority has jurisdiction. Both 'accessibility' and 'area-characteristics' models are used to interpret the pattern of unimproved values in 1970. In general the area-characteristics models are the most successful, but higher R2 values are achieved with hybrid models that combine road distance from the CBD modified by travel time, with such characteristics of areas as size of holding, land use, and terrain. In analysing the pattern of values in 1955, 1960, and 1365 compared with 1970, the statistical contribution of road distance to the CBD compared with terrain is stressed. Distance becomes a more effective predictor of value through time, while the explanation contributed by terrain-characteristics deteriorates. The large increases in the value of land that the region has experienced during the period studied are shown to have had less influence on the distribution of agriculture than has been suggested in other contexts. The main reasons advanced for the resilience of agriculture is its ability to compete for land, which is influenced by legislation allowing the postponement of rates (territorial local authority land taxes) on some agricultural land. The means by which quotas are allocated to farmers supplying liquid milk, and the marketing of fruit and vegetables direct to consumers, are also important in maintaining agricultural land in production.

Assessed values from the files of the New Zealand Valuation Department are the main dependent variable in this research. Unimproved values for individual parcels of land are aggregated into 301 areal units and multiple regression analysis is used to explain the spatial pattern of values in 1970. Temporal variations in the pattern of unimproved values and the influence of increasing values on the distribution of agricultural land use are also explored. The study area comprise most of the territory over which the Auckland Regional Authority has jurisdiction. Both 'accessibility' and 'area-characteristics' models are used to interpret the pattern of unimproved values in 1970. In general the area-characteristics models are the most successful, but higher R2 values are achieved with hybrid models that combine road distance from the CBD modified by travel time, with such characteristics of areas as size of holding, land use, and terrain. In analysing the pattern of values in 1955, 1960, and 1365 compared with 1970, the statistical contribution of road distance to the CBD compared with terrain is stressed. Distance becomes a more effective predictor of value through time, while the explanation contributed by terrain-characteristics deteriorates. The large increases in the value of land that the region has experienced during the period studied are shown to have had less influence on the distribution of agriculture than has been suggested in other contexts. The main reasons advanced for the resilience of agriculture is its ability to compete for land, which is influenced by legislation allowing the postponement of rates (territorial local authority land taxes) on some agricultural land. The means by which quotas are allocated to farmers supplying liquid milk, and the marketing of fruit and vegetables direct to consumers, are also important in maintaining agricultural land in production.

Assessed values from the files of the New Zealand Valuation Department are the main dependent variable in this research. Unimproved values for individual parcels of land are aggregated into 301 areal units and multiple regression analysis is used to explain the spatial pattern of values in 1970. Temporal variations in the pattern of unimproved values and the influence of increasing values on the distribution of agricultural land use are also explored. The study area comprise most of the territory over which the Auckland Regional Authority has jurisdiction. Both 'accessibility' and 'area-characteristics' models are used to interpret the pattern of unimproved values in 1970. In general the area-characteristics models are the most successful, but higher R2 values are achieved with hybrid models that combine road distance from the CBD modified by travel time, with such characteristics of areas as size of holding, land use, and terrain. In analysing the pattern of values in 1955, 1960, and 1365 compared with 1970, the statistical contribution of road distance to the CBD compared with terrain is stressed. Distance becomes a more effective predictor of value through time, while the explanation contributed by terrain-characteristics deteriorates. The large increases in the value of land that the region has experienced during the period studied are shown to have had less influence on the distribution of agriculture than has been suggested in other contexts. The main reasons advanced for the resilience of agriculture is its ability to compete for land, which is influenced by legislation allowing the postponement of rates (territorial local authority land taxes) on some agricultural land. The means by which quotas are allocated to farmers supplying liquid milk, and the marketing of fruit and vegetables direct to consumers, are also important in maintaining agricultural land in production.

The active Orakeikorako-Te Kopia geothermal system was drilled in the mid-1960’s, down to 1405m, as part of a programme to investigate its electrical generation capability. Four wells were completed at Orakeikorako (23km NNE of Taupo) and two at Te Kopia, 9.5km further northeast. The exploration drilling provided information on the present day hydrological and thermal regime which is as hot as 265°C (1137m drilled depth (-801m RL) in OK-2). Major flows into the wells occurred at depths down to 850m, although poor permeability and decline in mass output discouraged development. The waters discharged were of near neutral pH and had low salinities (highest Cl content from OK-2 ≈546mg/kg), low discharge enthalpies and indicated water temperatures (TSiO2 and TNaKCa) of 2l0°C to 240°C. A hydrologic model proposed here envisages a hot water reservoir in the OK-2 area (northeastern part of the Orakeikorako thermal area) with a lateral flow supplying water to the Red Hill (OK-4 area) in the southern part of the system and a concealed northeast flow which reaches the surface at Te Kopia. The Orakeikorako thermal area occupies a surface area of about 1.8km2, mainly on the east bank of the Waikato River, where dilute chloride-bicarbonate water discharges along faults and fractures in association with an extensive silica sinter sheet, boiling springs and geysers. The occurrence of a mordenite-smectite assemblage at shallow depths, plus the oxygen and hydrogen isotopic composition of surface discharge waters, indicate that the ascending chloride fluids are diluted by near surface (heated?) groundwaters. The δD shift from local groundwater composition may be evidence for a magmatic component to the convecting hydrothermal system. Incursion of fluids from the relatively cool (<l20°C) steam-heated carapace into deep levels of the system and its mixing with the alkali-chloride fluids, produces argillic alteration, sealing and will eventually result in the demise of the system. Old silica sinter on the west bank, at the foot of the Tutukau Rhyolite Dome, is covered by Oruanui Ash (22,700 years B.P.) and demonstrates that the hydrologic character of this part of the system has changed due to a combination of fault movement, changes in the height of the watertable and sealing. The Te Kopia thermal area is located along 2.5km of the Paeroa Fault scarp, a major structural feature inferred to be controlling migration of deep hydrothermal fluids in the Orakeikorako-Te Kopia area. Surface activity at Te Kopia is characterised by acid alteration (including fumaroles, warm acid pools and steaming ground), although neutral pH alkali-chloride fluids discharged here within the last 3000 years and deposited silica sinter (C14 age on wood enveloped by sinter is 3026 +/- 43years B.P.). New thermal areas in the past --year have begun to develop in the northwestern part of Te Kopia, whilst cold hydrothermally altered ground (hosting a mordenite + clay assemblage) records a decline in activity in the southern part of the Te Kopia thermal area. The system is hosted by a generally SE dipping sequence of Pliocene to Quaternary ignimbrite, tuff and rhyolite lavas of the Taupo Volcanic Zone. Point counting, electron microprobe analyses of surviving primary phases (Fe, Mg, Al and Ti contents of hornblende and biotite), together with X-ray fluorescence and neutron activation analysis were used to distinguish three extensive ignimbrites encountered in the Orakeikorako-Te Kopia drillholes: (0.33Ma, sanidine-bearing) Paeroa, (0.35Ma) Te Kopia and (undated) Akatarewa Ignimbrites, despite their having been hydrothermally altered. Ignimbrite recognition is made on the basis of a combination of immobile trace and rare earth element abundances and ratios: Ta and Yb (ppm), P2O5(%) and the ratios Zr/Yb, Zr/Y, Yb/Hf, La/Lu, Nb/Hf, Zr/Nb, Zr/Lu, Yb/Ta, Ta/Lu, La/Tb and Nb/Ta. The Paeroa Ignimbrite is distinguished by is Eu anomaly ((Eu/Eu*)cn is 0.48 to 0.54), whereas the Te Kopia and Akatarewa Ignimbrites are characterised by their flatter REE Spidergrams ((Eu/Eu*)cn is ~1.0 and ~0.8 respectively). The correlation of the extensive ignimbrites was satisfactorily effected by a combination of their characteristic bulk rock and pumice chemistry, plus primary mineralogy, to enable the subsurface stratigraphy and structure of the Orakeikorako-Te Kopia geothermal system to be defined. The alteration assemblage below 500m consists of quartz, albite+adularia, with variable abundence and distribution of chlorite, pyrite, calcite, wairakite, epidote, pyrrhotite, titanite, leucoxene, siderite and clinozoisite; illite is a late overprint. Rare almandine occurs in rhyolite in OK-1: 1312.5m; this is the first known occurrence of garnet in an active geothermal system of the TVZ. The surficial alteration assemblage of kaolin, cristobalite, alunite, hematite and jarosite reflects alteration by acid sulphate-steam heated waters. The occurrence and textual relations exhibited by the hydrothermal mineral assemblage define the geochemical structure and thermal evolution of the Orakeikorako-Te Kopia system The activities of components of minerals, determined from electron microprobe analyses and composition-activity relationships (OK-2 discharge: logαK+/αH+=3.6, logαNa+/αH+=4.8) support the petrologic observation that illite is now the stable potassium phase (overprinting adularia), although a state of equilibrium between the sheet silicate and the fluids is clearly not fully reached. The Na/K ratio of the altering fluid is controlled by the albite-adularia reaction (dissolution of albite and replacement by adularia, after andesine), whilst the H2/H2S ratio is buffered by the virtually complete replacement of pyrrhotite by pyrite. The fluids are now slightly undersaturated with respect to calcite, this is shown by etched surfaces on some calcite grains. In the past the deep fluid boiled adiabatically from >300°C to ~250°C as it ascended, resulting in the deposition of adularia, quartz and bladed calcite. The system has cooled, resulting in lower subsurface temperatures (as recorded by fluid inclusion geothermometry) suppressing boiling, and migrated northwards as a consequence of self sealing. The thermal decline and retention of CO2 in the deep alkali-chloride fluid shifted the alteration assemblage from one of albite-adularia stability to illite stability. The homogenisation (Th) temperatures of primary and secondary liquid-rich inclusions in 27 cores from different depths mostly match measured temperature profiles (e.g. OK-1 (shallow levels) and OK-2). Never-the-less, fluid inclusion data support mineral-inferred stability temperatures which indicate that parts of the Orakeikorako-Te Kopia system have cooled appreciably (e.g. OK-1, deep levels) and OK-4 (maximum Tbore=238°C, maximum Th=312°C; epidote abundant). In contrast, the northwestern margin (OK-6 area) has heated (OK-6:1113.4m; Tbore=261°C, Th=210-221°C). Some inclusions in the Te Kopia drillholes have Th values that exceed Tbore by as much as 50°C, and are deduced to have been uplifted by movement on the Paeroa Fault. Freezing data indicate that the trapped fluid was dilute (~0.2 to 1.7 wt% NaCl equivalent) since most Tm values range from -0.1 to -0.5°C. The outflow portion of the Orakeikorako-Te Kopia system has evolved recently, both chemically and physically. Movement on the Paeroa Fault, that uplifted pyroclastic rocks hosting a quartz-adularia-illite assemblage, combined with a lowering of the watertable has resulted in an overprinting of the neutral pH hydrothermal mineral assemblage by a kaolinite-alunite type assemblage which derives from an acid sulphate fluid. Quartz crystals found 150m above the base of the Paeroa Fault scarp host dilute (~1.5wt% NaCl equivalent) fluid inclusions with Th values that range from 180-206°C (average 196°C). Bladed quartz (after calcite) did not contain usable inclusions. It is deduced that the inclusions formed about 120-160m below the ground, which indicates uplift in the order of ~300m. Assuming a constant rate of uplift of 4m/ka (based on the offset of 330ka Paeroa Ignimbrite), the minimum duration of activity at Te Kopia is 75,000 years.

Some 2500 specimens of Monotis from more than 500 localities within New Zealand were studied by statistical and traditional descriptive methods. From this analysis 20 taxa are recognised as constituting the New Zealand Monotis fauna, with the future possible addition of two further taxa. M. richmondiana Zittel, claimed by some overseas workers as a junior synonym of M. ochotica (Keyserling), is established as validly separable and is seen to include Trechmann's (1918) Pseudomonotis ochotica var. acutecostata as a subspecies. The presence of the New Caledonian M. routhieri and M. ochotica gigantea (Avias, 1953) is confirmed and the latter is transferred to M. subcircularis Gabb. Monotis salinaria var. hemispherica and var. intermedia (of Trechmann, 1918) are reinstated as valid taxa and given full specific rank. M. calvata Marwick (1953) is retained as a full species. In addition, the following species and subspecies are proposed: awakinoensis, kiritehereensis, maniapotoi, marwicki, murihikuensis, murihikuensis taringatura, pinensis aotearoa, rauparaha, rauparaha aries, rauparaha mokaui, subcircularis discordans, wairakae, and warepana. Only Pseudomonotis richmondiana var. truncata Frech (1908) amongst names previously proposed for New Zealand Monotis is rejected as a nomen dubium; it is probably synonymous with M. richmondiana acutecostata (Trechmann). The species-group concept of Westermann (1973b) is formalised by the proposal of five subgeneric divisions to accommodate the 55 definite and up to 5 possible taxa included in the genus. The subgenera Monotis, Entomonotis Marwick (type: M. richmondiana), Eomonotis n.subgen. (type: Pseudomonotis scutiformis var. typica Kiparisova), Inflatomonotis n.subgen. (type: Monotis salinaria var. hemispherica Trechmann), and Maorimonotis n.subgen. (type: Monotis routhieri) are differentiated on the basis of adult size, prominence and sculpture of the posterior auricle, the degree to which it is separated from the disc, shell inflation, radial ribbing and shell thickness. Eomonotis is the oldest subgenus and the stem-stock for the others; it probably evolved from Otapiria. It is unclear from morphologic evidence whether Monotis (s.s.) and Entomonotis developed one from the other or both from Eomonotis independently. Maorimonotis is confidently believed to have sprung from an Entomonotis similar to M. pachypleura (Teller) and Inflatomonotis is most likely to have evolved from an Eomonotis with strongly inflated left valve (e.g. M. jakutica (Teller) or M. iwaiensis Ichikawa). Eomonotis and Entomonotis are geographically the most widespread, the former being absent only from the Andean area of Monotis distribution and Entomonotis not having been recorded in the western or central Tethys. Monotis (s.s.) is common only in the western Tethys. Inflatomonotis and Maorimonotis are confined to New Zealand-New Caledonia except for one record of the former in British Columbia. In many regions the stratigraphic sequence of Monotis is too inadequately known for evolutionary sequences to be deduced but some examples of chronologic and geographic subspeciation are pinpointed. The only clearly defined lineage is that within Maorimonotis from maniapotoi through awakinoensis and routhieri to calvata. The genus can be seen to have a high taxonomic diversity and rapid rate of evolution. Apart from three questionable lower Triassic and lower Jurassic species, Monotis is confined to the Norian Stage, and possibly to the Columbianus and Suessi Zones of the mid and upper Norian. Monotis is postulated as having been epibyssate throughout life and normally epiplanktonic on drifting or floating marine vegetation, with coexisting taxa occupying different microenvironments on different parts of the plants. A serious objection to this mode of life is the massive algal production necessary to provide a substrate for the tremendous numbers of individuals involved in Monotis shellbeds. Reduction of the byssal ear in Maorimonotis is seen as a significant event and coupled with the trend to an equivalved condition is interpreted as indicating change to an endobyssate benthic existence for M. routhieri and calvata; this adequately explains the restricted distribution of this subgenus. Detailed stratigraphic analysis of Monotis in Murihiku sequences necessitates rejection of the Rocky Dome section as stratotype for the Warepan Stage on the grounds that although M. richmondiana has been cited as the marker fossil for the stage, past usage has clearly equated the base of the stage with the incoming of the genus, and richmondiana is not the oldest member of the genus to be found in Murihiku sections. Earlier members are absent from the stratotype which therefore must be relocated in order to retain the stage in its accepted scope. The Kiritehere coastal section suffers the disadvantage of penecontemporaneous submarine slumping, but is proposed as stratotype for a new Marakopan Stage because it is the thickest, best exposed, clearest and best known sequence of Monotis beds and adjacent strata in New Zealand. Within this stage a sequence of five formal and three informal chronozones is defined. The lower Marakopan Mokaui and Murihikuensis Chronozones can be grouped together as an Eomonotis chronozone when faunas are too poor for better correlation, and similarly the overlying Acutecostata, Richmondiana and Calvata Chronozones can be grouped as an Entomonotis chronozone. In addition a topmost Marakopan chronozone can be recognised from the absence of Monotis and basal Otapirian indicators and the presence of a fauna which at present seems common to the two stages. Monotis is the most common fossil in the Torlesse Super-group and the lower four Chronozones, and probably also the Calvata Chronozone, are all represented. Most forms present in Murihiku rocks are also present in Torlesse, but two common Torlesse forms are unknown in Murihiku sequences and this is believed to indicate both communication and barriers between the two regions in Marakopan times. Monotis-bearing Torlesse lithologies are more varied than Murihiku and indicate different depositional regimes. Whilst Murihiku Marakopan strata are all of normal clastic lithologies and show a southwards increase in grain-size, the Torlesse picture is more complex. Firstly, an increasingly deeper and offshore situation is suggested by some deposits with Murihiku faunas: inner or middle neritic origin for Monotis-bearing clasts in a (?) late Jurassic conglomerate at Morrinsville which possibly accumulated in the outer neritic zone or slightly deeper, outer neritic for in situ strata near Aria, slightly further offshore accumulation for ? middle Jurassic mélange in the Oroua Valley and Marakopan slump deposits in the Otaki Gorge, and bathyal or even abyssal deposition for argillites with scattered Monotis in the Mt Arthur-Bealey area. The Aria Monotis beds lie west of the Waipa Fault, yet fit best into Kear's (1967, 1971) Morrinsville Facies, and indicate that the Hakarimata Anticline, Waipa Fault and the facies relations postulated by Kear date from the mid-Jurassic and that there was no feature like the modern continental edge and slope during upper Triassic times in the region. Close paleogeographic relations between these areas and the Murihiku region in Marakopan times is indicated and is not disproven by any sedimentologic evidence yet known. One lithologic association not represented in and showing distinct geographic separation from the Murihiku area is the shell limestone-submarine lava-chert association, which is that containing Monotis species endemic to the Torlesse. This is postulated as having been formed in localised offshore shoal areas (guyots) formed by submarine volcanism; even these regions had some connection with Murihiku seas.

A database was developed for the storage and convenient analysis of inorganic background soil constituent data within specific geological groups in Victoria, Australia. A statistical analysis of the data revealed the relative abundances of metals and, in particular, arsenic within soils of various geological units. These units included the Quaternary Aeolian (Qpw) (highest concentration of zinc, lowest concentration of chromium) the Quaternary Fluvial (Qrc) (highest chromium and nickel, equal highest copper, lowest lead and equal lowest arsenic); the Quaternary Newer Volcanics (Qvn) (equal lowest arsenic concentration); Silurian Anderson Creek Formation (Sla) (highest arsenic); Silurian Dargile Formation (Sud) (highest lead, equal highest copper); Tertiary Brighton Group (Tpb) (lowest nickel) and Older Volcanics (Tvo) (lowest copper and zinc). The identification of arsenic as a significant background constituent prompted a formal study of this element with respect to the nature of its sorption onto different kinds of soils, its bioavailability and speciation. Arsenic soil sorption analyses were conducted in the laboratory on clay loam, light clay, sand and silt loam soils. These experiments demonstrated that the sorption of arsenic was dependent on soil type and time of soil exposure to the arsenic solution. The bioavailability of arsenic from soil was also investigated using a relative bioavailability test method referred to as the 'geophagy gut simulation' extraction method. The adaptation of this method to these investigations showed it to be a viable, fast and simple technique. The experimental results indicated that the relative bioavailability of sorbed total arsenic was dependent on soil type. Given that the toxicity of arsenic is dependent on its speciation, techniques were also evaluated to assess arsenic speciation in soil extracts. To this end, the utility of electrospray mass spectrometry (ESI-MS) for the qualitative and quantitative assessment of arsenic and phosphorus speciation in solution was explored. Although this technique yielded interesting qualitative outcomes it was deemed not to be suitable for quantification. From the qualitative data, various postulates were formulated for the interaction between different species that were subsequently tested by quantum chemical calculations. A technique, based on extraction into chloroform, for quantifying the amount of AsIII in a sample was adapted to these investigations and was found to be highly accurate and discriminating, albeit time consuming. All phosphorus and arsenic species found to coexist in the ESI-MS experiments were modelled using high-level density functional theory (DFT). From these calculations, the relative energies of the species could be determined as well as reaction energies for their inter-conversion. This allowed hypotheses to be proposed for the distribution of such species in solution and how they might be taken up into clay structure. The DFT calculations also yielded geometrical information on a wide range of species as well as their electrostatic potential energy maps.