Characterization of hydrogeologic properties for a multi-layered alluvial aquifer using hydraulic and tracer tests and electrical resistivity survey

A multi-layered aquifer, typical of riverbank alluvial deposits in Korea, was studied to determine the hydrologic properties. The geologic logging showed that the subsurface of the study site was comprised of four distinctive hydrogeologic units: silt, sand, highly weathered and fresh bedrock layers. The electrical resistivity survey supplied information on lateral extension of hydrogeologic strata only partially identified by a limited number of the geologic loggings. The laboratory column tracer test for the recovered core of the sand layer resulted in a hydraulic conductivity of 5.00×10⁻² cm/s. The slug tests performed in the weathered rock layer yielded hydraulic conductivities of 4.32–7.72×10⁻⁴ cm/s. Hydraulic conductivities for the sand layer calculated from the breakthrough curves of bromide ranged between 2.08×10⁻³ and 2.44×10⁻² cm/s with a geometric mean of 6.89×10⁻³ cm/s, which is 7 times smaller than that from the laboratory column experiment. The trend of increasing hydraulic conductivity with an increase in tracer travel length is likely a result of the increased likelihood of encountering a high conductivity zone as more of the aquifer is tested. The combined hydrogeologic site characterization using hydraulic tests, tracer tests, and column test with geologic loggings and geophysical survey greatly enhanced the understanding of the hydrologic properties of the multi-layered alluvial aquifer.     

Dynamics and interaction of organic carbon, turbidity and bacteria in a karst aquifer system

The dynamics of organic carbon (OC), turbidity, faecal indicator bacteria and physicochemical parameters was studied in a karst system near Yverdon, Switzerland. Online measurements and sampling were done at a swallow hole draining an agricultural surface (the input), and two groups of springs (the outputs) that often show bacterial contamination. A fluorescent tracer that was injected into the swallow hole during low-flow conditions first arrived at the springs 10–12 days after injection; the total recovery rate was 29%. Previous tracer tests during high-flow conditions gave shorter travel times. After a major rainfall event, a primary turbidity peak was observed at the springs. It coincides with the rising limb of the hydrograph, indicating remobilisation of autochthonous particles from the aquifer. A secondary turbidity peak occurs several days later, suggesting the arrival of allochthonous particles from the swallow hole. Wider peaks of OC and bacteria were observed simultaneously. Applying methods from molecular microbiology (PCR-DGGE) allowed characterisation of the bacterial communities at the swallow hole and the springs. The results demonstrate that the swallow hole is an important source of groundwater contamination, while its contribution to aquifer recharge is insignificant. OC appears to be a better indicator for bacterial contamination than turbidity.     

Combined interpretation of radar, hydraulic, and tracer data from a fractured-rock aquifer near Mirror Lake, New Hampshire, USA

An integrated interpretation of field experimental cross-hole radar, tracer, and hydraulic data demonstrates the value of combining time-lapse geophysical monitoring with conventional hydrologic measurements for improved characterization of a fractured-rock aquifer. Time-lapse difference-attenuation radar tomography was conducted during saline tracer experiments at the US Geological Survey Fractured Rock Hydrology Research Site near Mirror Lake, Grafton County, New Hampshire, USA. The presence of electrically conductive saline tracer effectively illuminates permeable fractures or pathways for geophysical imaging. The geophysical results guide the construction of three-dimensional numerical models of ground-water flow and solute transport. In an effort to explore alternative explanations for the tracer and tomographic data, a suite of conceptual models involving heterogeneous hydraulic conductivity fields and rate-limited mass transfer are considered. Calibration data include tracer concentrations, the arrival time of peak concentration at the outlet, and steady-state hydraulic head. Results from the coupled inversion procedure suggest that much of the tracer mass migrated outside the three tomographic image planes, and that solute is likely transported by two pathways through the system. This work provides basic and site-specific insights into the control of permeability heterogeneity on ground-water flow and solute transport in fractured rock.

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Resumen Una interpretación integrada de radar experimental de campo transversal a pozos, trazadores, y datos hidráulicos demuestra el valor de combinar el monitoreo geofísico realizado en periodos de tiempo con mediciones hidrológicas convencionales en la caracterización mejorada de un acuífero rocoso fracturado. Se llevó a cabo tomografía de radar por periodos de tiempo y diferencia de atenuación durante un experimento con trazadores salinos en el sitio de investigación hidrológica de roca fracturada del Servicio Geológico de Estados Unidos cerca del Lago Espejo, Condado Grafton, New Hampshire, USA. La presencia del trazador salino eléctricamente conductivo refleja efectivamente fracturas permeables o trayectorias para imágenes geofísicas. Los resultados geofísicos orientan la construcción de modelos numéricos tri-dimensionales de flujo de agua subterránea y transporte de solutos. En un esfuerzo por explorar explicaciones alternativas para los datos tomográficos y trazadores se considera un conjunto de modelos conceptuales que involucran campos de conductividad hidráulica heterogéneos y transferencias de masa de ritmo limitado. La calibración de datos incluye concentraciones de trazadores, el tiempo de llegada de la concentración pico en la salida, y presión hidráulica en régimen permanente. Los resultados del procedimiento de acoplamiento invertido sugieren que mucho de la masa del trazador migró fuera de los tres planos de imagen tomográfica, y que el soluto es probablemente transportado por dos trayectorias a través del sistema. Este trabajo aporta ideas básicas y específicas del sitio en relación con el control de la heterogeneidad de permeabilidades en el flujo de agua subterránea y transporte de solutos en rocas fracturadas.

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Résumé Une interprétation intégrée détudes de terrain (radar entre puits, traçages, données hydrauliques) démontre la valeur de la combinaison entre la géophysique des temps finis et les mesures hydrologiques conventionnelles pour une interprétation améliorée dun aquifère de roche fracturée. La tomographie au radar a été mise en uvre durant un traçage artificiel au sel au site de recherche sur lhydrologie des roches fracturées du Service Géologique des US, à proximité du Lac Mirror, Conté de Grafton, Nouvel Hampshire, USA. La présence du traceur électriquement conducteur met en relief, grâce à la géophysique, la présence de fractures ou découlements préférentiels. Les résultats de la géophysique ont permis la construction de modèle hydrogéologique tri-dimensionnel des écoulements et du transport de soluté. Dans loptique dexplorer des interprétations alternatives des données de traçage et de tomographie, différents modèles conceptuels sont utilisés concernant lhétérogénéité des conductivités hydrauliques et des taux limités de transferts de solutés. Les données du calibrage incluent les données de concentration du traceur, le temps darrivée du pic de restitution et les données piézométriques en régime permanent. Les résultats de la procédure dinversion couplée suggèrent quune quantité très importante du traceur migre au delà de la fenêtre de visualisation des tomographies, et que le soluté est transporté via deux voies découlement préférentiel. Ce travail apporte des connaissances de base et spécifiques au site concernant la distribution de la perméabilité dans laquifère et le transport de soluté dans les roches fracturées.

     

Comparison between Neuman (1975) and Jacob (1946) application for analysing pumping test data of unconfined aquifer

Pumping test of a water table aquifer is carried out to estimate the aquifer parameters, the obtained data were analysed through the solution of both Neuman (1975) and Jacob (1946) methods through AQTESOLV and Spreadsheet programs, the results of each methods are compared to evaluate the applicability and accuracy of the solution theoretically and practically. In the paper an example is presented, which is conducted for a constant rate pumping test from Ohio, in Fairborn (near Dayton), and it supplied by S.E. Norris (U.S. Geological Survey, Columbus, Ohio). The main objective of this study is to introduce both program and the way of the applications, and compare the results and the hand on of both programs in the field.     

新西兰城市防震减灾

本文介绍了新西兰的地震背景以及城市防震减灾工作的组织机构、动作及相关措施。     

Mid-Cretaceous granitic magmatism during the transition from subduction to extension in southern New Zealand: a chemical and tectonic synthesis

Regional geochronological studies indicate that mid-Cretaceous plutonism (the Hohonu Suite at 110 Ma) in the Hohonu Batholith, Western Province of New Zealand, occurred during a period of rapid tectonic change in the SW Pacific portion of Gondwana. The 30–40 m.y. preceding Hohonu Suite magmatism were dominated by the subduction-related plutonism of the Median Tectonic Zone volcanic arc. Between 125–118 Ma there was a major collisional event, inferred to be the result of collision between the Median Tectonic Zone and the Western Province. This collision resulted in melting of the Median Tectonic Zone arc underplate and generation of a distinctive suite of alkali-calcic granitoids, termed the Separation Point Suite. At 110 Ma there was another pulse of magmatism, restricted to the Buller terrane of the Western Province, and including the Hohonu Suite granitoids. This was followed almost immediately by extension, culminating in the opening of the Tasman Sea some 30 m.y. later. The Hohonu Suite granitoids overlap temporally with the last vestiges of collisional Separation Point magmas and the onset of crustal extension in the Western Province, and thus represent magmatism in a post-collisional setting. Hohonu Suite magmas are typically calc-alkaline, but retain a chemical signature which suggests that the earlier Separation Point Suite magmas and/or sources were involved in Hohonu Suite petrogenesis. A model is proposed in which rapid isothermal uplift, resulting from the post-collisional collapse of continental crust previously thickened during the Median Tectonic Zone collision, caused melting of lower continental crust to generate the Hohonu Suite granitoids. In this example, granitoid composition is a consequence of the composition of the source rocks and the conditions present during melting, and no geochemical signature indicative of the tectonic setting during magmatism is present.     

Back to the Future? Reflections on past reforms and future prospects for health services in New Zealand

In 1991 the New Zealand health system began to experience what has been termed the `turbulent decade'. Without health sector consultation or public mandate, an era of imposed market oriented reforms began. These changed the overall culture of health care delivery and the expectations of New Zealanders regarding the role of the state in the provision of welfare. In retrospect the ideologically driven imposition of the market-oriented reforms was not an exercise of bold leadership but one of political arrogance and rejection of established community values. Within the community, the neoliberal experiment heightened income and health inequalities, created a loss of social cohesion and generally provoked feelings of powerlessness. In the health sector, the reforms polarised clinical and commercial cultures and changed the geography of health care delivery. This occurred not only because place was de-emphasised, but also because decentralisation of purchasing created four health systems with widely divergent contracting arrangements and standards of care. The lessons of the health reforms have been painful, and must not be lost. A fundamental lesson is that market approaches to the delivery of health care have major limitations and that the ultimate goal of a health system should be the equitable, effective and efficient provision of care, not the profitable sale of commodities. Since 1997 there has been a retreat from the market, although it is not clear whether recent policy developments represent a new or distinctive `third way' or a pragmatic `pick and mix', combining the best from the market and the managerialism first introduced by Labour in the 1980s. Quite clearly, the experiment with the market was not sustainable. Whether this will also be true of the more recent and pragmatic `pick and mix' approach of the `third way' to health care reform is uncertain. This revised version was published online in July 2006 with corrections to the Cover Date.     

Welfare reform and the intra-regional migration of beneficiaries in New Zealand

This paper investigates the net effect of major cuts in welfare benefits and associated changes in the delivery of housing assistance on the relocation behavior of beneficiaries. It does so against an international literature which has documented the tendency of welfare recipients to adjust their costs of living by moving from urban to rural settlements. The paper reviews the literature on welfare and migration, introduces a theoretical framework based on a metropolitan labour market and then tests several hypotheses about the possible effects of benefits cuts on spatial adjustment. The research design uses quinquennial census data to compare core beneficiary relocation patterns with those of non-beneficiaries before and after the cuts to welfare benefits in the Wellington region of New Zealand in 1991. The period following the benefit cuts in New Zealand was characterised by increasing job opportunities which helped to mitigate their adverse effect and made it difficult to identify a more general down-market residential adjustment. While a downward adjustment in housing consumption by core beneficiaries was identified, residential movement from urban to the cheaper settlements in adjacent rural areas was only observed from former State house areas where the income effects of benefit cuts were compounded by increases in rents on former State houses. Thus, while this paper supports the findings of independent sample survey work, our census based analysis underscores the highly contingent nature of that response. Evidence of urban-rural migration is placed in the context of the government's `remote area policy' which attempts to dissuade beneficiaries (who are receiving a social security benefit related to their employment status) from moving without good reason to `remote' locations where job prospects are weak. The paper raises the more general policy issue where benefit cuts, designed to stimulate more active job searching among the unemployed, actually prompt some beneficiaries to relocate to the urban fringe and in some cases to remote parts of the country where job prospects are weak. The theoretical and policy implication of this paper is that there are geographical correlates to the reservation wage which need to be integrated into thinking about the participation consequences of setting benefit levels.     

Evaluation of methods for determination of hydraulic properties in an aquifer–aquitard system hydrologically connected to a river

Field and laboratory methods have been used to determine the hydraulic properties in a multiple-layer aquifer–aquitard system that is hydrologically connected to a river. First, hypothetical pumping tests in aquifer–aquitard systems were performed to evaluate the feasibility of MODFLOW-PEST in determining these parameters. Sensitivity analyses showed that: the horizontal hydraulic conductivity in the aquifer has the highest composite sensitivity; the vertical hydraulic conductivity has higher composite sensitivity than the horizontal hydraulic conductivity in the aquitard; and a partial penetration pumping well in an aquifer layer can improve the quality of the estimated parameters. This inverse approach was then used to analyze a pumping-recovery test conducted near the Platte River in southeastern Nebraska, USA. The hydraulic conductivities and specific yield were calculated for the aquitard and aquifer. The direct-push technique was used to generate sediment columns; permeameter tests on these columns produced the vertical hydraulic conductivities that are compatible with those obtained from the pumping-recovery test. Thus, the combination of the direct-push technique with permeameter tests provides a new method for estimation of vertical hydraulic conductivity. The hydraulic conductivity, determined from grain-size analysis, is smaller than the horizontal one but larger than the vertical one determined by the pumping-recovery test.     

SHRIMP monazite and zircon geochronology of high-grade metamorphism in New Zealand

Ion microprobe dating of zircon and monazite from high-grade gneisses has been used to (1) determine the timing of metamorphism in the Western Province of New Zealand, and (2) constrain the age of the protoliths from which the metamorphic rocks were derived. The Western Province comprises Westland, where mainly upper crustal rocks are exposed, and Fiordland, where middle to lower crustal levels crop out. In Westland, the oldest recognisable metamorphic event occurred at 360–370 Ma, penecontemporaneously with intrusion of the mid-Palaeozoic Karamea Batholith (c. 375 Ma). Metamorphism took place under low-pressure/high-temperature conditions, resulting in upper-amphibolite sillimanite-grade metamorphism of Lower Palaeozoic pelites (Greenland Group). Orthogneisses of younger (Cretaceous) age formed during emplacement of the Rahu Suite granite intrusives (c. 110 Ma) and were derived from protoliths including Cretaceous Separation Point suite and Devonian Karamea suite granites. In Fiordland, high-grade paragneisses with Greenland Group zircon age patterns were metamorphosed (M1) to sillimanite grade at 360 Ma. Concomitant with crustal thickening and further granite emplacement, M1 mineral assemblages were overprinted by higher-pressure kyanite-grade metamorphism (M2) at 330 Ma. It remains unclear whether the M2 event in Fiordland was primarily due to tectonic burial, as suggested by regional recumbent isoclinal folding, or whether it was due to magmatic loading, in keeping with the significant volumes of granite magma intruded at higher structural levels in the formerly contiguous Westland region. Metamorphism in Fiordland accompanied and outlasted emplacement of the Western Fiordland Orthogneiss (WFO) at 110–125 Ma. The WFO equilibrated under granulite facies conditions, whereas cover rocks underwent more limited recrystallization except for high-strain shear zones where conditions of lower to middle amphibolite facies were met. The juxtaposition of Palaeozoic kyanite-grade rocks against Cretaceous WFO granulites resulted from late Mesozoic extensional deformation and development of metamorphic core complexes in the Western Province.     

基于高分辨率示踪技术的岩溶隧道涌水来源识别及含水介质研究

利用高分辨率示踪技术探讨了重庆三泉隧道突水来源,并对含水介质进行了刻画,结果表明:（1）隧道涌水段受长滩地下河影响,而麦阴槽落水洞为长滩地下河的补给来源之一;（2）试验段岩溶含水介质通畅,地下水流速快,为典型紊流态;地下河管道结构不均匀,发育两条过水通道,为主管道并联支管道,无溶潭和地下湖发育;利用Qtracer2软件,计算得到地下河几何参数及水文地质参数:地下管道储水体积为1 148.4 m3,表面积为1.30×106 m2,平均直径为1.37 m,长度为780 m;摩擦系数为0.51,舍伍德数为1 055.1,施密特数为1 140,水力深度为1.08 m,分子扩散边界层厚度为1.3 mm;（3）因试验时间短、试验为小流量期及存在其他地下河出口等条件制约,示踪剂天来宝的回收率较低,上湾洼地与隧道涌水段连通关系有待进一步研究;（4）由于三泉隧道涌水点与地表水具有直接水力联系,且涌水量大,建议引走地表洼地水源、填埋隧道上方麦阴槽落水洞或在隧道下方新建泄水洞排水。      

Delineation of groundwater protection zones based on tracer tests and transport modeling in alluvial sediments

 Regulations aiming to protect exploitable groundwater resources were edicted in Belgium a few years ago. Therefore, prevention and protection zones are defined by law and must be determined practically around each pumping well or spring, based on local hydrogeological conditions. The determination of hydrodynamic and hydrodispersive parameters, characterizing the local flow and transport properties of the aquifer, requires pumping and tracing tests. The interpretation of these field experiments, considering the heterogeneity of the geological layers, is performed through the use of numerical FEM simulations of the groundwater flow and pollutant transport conditions in a deterministic framework. After calibration of the model on experimental measurements, multiple simulations with contaminant injections at various points of the modeled domain allow the determination of the transfer time of the pollutant in the studied aquifer whilst taking the updated heterogeneity into account. On the basis of the computed transfer times in the saturated zone, the various prevention and protection areas can be assessed based on provisions of the law. Received: 27 June 1997 · Accepted: 29 July 1997     

Integration of zircon color and zircon fission-track zonation patterns in orogenic belts: application to the Southern Alps, New Zealand

An exhumed crustal section of the Mesozoic Torlesse terrane underlies the Southern Alps collision zone in New Zealand. Since the Late Miocene, oblique horizontal shortening has formed the northeastern–southwestern trending orogen and exhumed the crustal section within it. On the eastern side, rocks are zeolite- to prehnite–pumpellyite-grade greywacke; on the western side rocks, they have the same protolith, but are greenschist to amphibolite facies of the Alpine Schist. Zircon crystals from sediments in east-flowing rivers (hinterland) have pre-orogenic fission-track ages (>80 Ma) and are dominated by pink, radiation-damaged grains (up to 60%). These zircons are derived from the upper 10 km crustal section (unreset FT color zone) that includes the Late Cenozoic zircon partial annealing zone; both fission tracks and color remain intact and unaffected by orogenesis. Many zircon crystals from sediments in west-flowing rivers (foreland) have synorogenic FT ages, and about 80% are colorless due to thermal annealing. They have been derived from rocks that originally lay in the reset FT color zone and the underlying reset FT colorless zone. The reset FT color zone occurs between 250 and 400 °C. In this zone, zircon crystals have color but reset FT ages that reflect the timing of orogenesis.     

On the sensitivity of Holocene talus-derived rock glaciers to climate change in the Ben Ohau Range,New Zealand

The morphology and surface ages of talus-derived rock glaciers are investigated to establish the timing of rock glacier formation in the central Southern Alps. Samples of rock weathering rinds show that all rock glaciers studied were formed during the Neoglacial period, but differences exist between sites in the number of new rock glacier lobes formed by Holocene climatic fluctuations. A qualitative conceptual model is proposed to explain rock glacier formation in terms of two thresholds. An external threshold relates to the presence of a cool climate capable of allowing internal ice to form within talus slopes. An internal threshold relates to the presence of sufficiently thick talus at a site to generate a shear stress capable of overcoming internal friction within the talus/ice mass. The model produces a non-steady-state response to explain why unmodified talus, single-lobed and double-lobed rock glaciers developed at adjacent sites under the same climatic regime. Individual landforms have different sensitivities to formation, which depend partly on the previous history of talus accumulation and rock glacier activity at a site. The model demonstrates how successive cool climate periods may be fully represented by rock glacier lobes at sensitive sites but under-represented at insensitive sites. Sensitivity (and therefore climatic representativeness) is favoured by high rates of debris supply. By implication, the timing of formation of rock glacier lobes in regions of prolonged cool climate and low debris production is less likely to correspond to the timing of climatic cooling and more likely to follow the ‘rules’ of deterministic chaos.     

Conceptual model of a coastal aquifer system in northern Greece and assessment of saline vulnerability due to seawater intrusion conditions

This paper refers to the development of a conceptual model for the management of a coastal aquifer in northern Greece. The research presents the interpretation and analysis of the quantitative (groundwater level recordings and design of piezometric maps) regime and the formation of the upcone within the area of investigation. Additionally it provides the elaboration of the results of chemical analyses of groundwater samples (physicochemical parameters, major chemical constituents and heavy metals and trace elements) of the area which were taken in three successive irrigation periods (July–August 2003, July–August 2004 and July 2005), in order to identify areas of aquifer vulnerability. The study identifies the areas where ion exchange phenomena occur, as well as the parts of the aquifer where the qualitative degradation of the aquifer system is enhanced. The paper, finally, assesses the lack of any scientific groundwater resources management of the area by the local water authorities, as well as the current practices of the existing pumping conditions scheme as applied by groundwater users.An erratum to this article can be found at     

Delineation of a landfill leachate plume and flow channels in coastal sands near Christchurch, New Zealand, using a shallow electromagnetic survey method

The Burwood landfill, which serves the city of Christchurch, New Zealand, is situated on coastal sands underlain by a sequence of aquifers and aquitards. Groundwater flow is toward the coast, located approximately 700 m from the landfill boundary. Shortly after completion of the first phase of the landfill, an array of wells was installed to detect any contaminant from the landfill. Leachate was detected in the wells closest to the landfill. A shallow electromagnetic (EM31) survey was carried out between the landfill and the coast, in order to delineate any leachate plume that may be present. On the basis of the geophysical results, a contaminant plume and buried channels connected to the coast were identified. Leachate flow initially occurs in what is probably a channel or pair of channels. Downgradient, the plume spreads out to the north and south as it moves eastward toward the coast. Using the geophysical results as a guide, a new set of wells was installed to confirm the presence of high leachate concentrations. Pore-water sampling confirms the presence of a leachate plume. Received, June 1998 /Revised, March 1999, January 2000/Accepted, January 2000     

新西兰科罗曼德尔半岛金（铜）矿床地质特征、成因及找矿意义

新西兰科罗曼德尔半岛火山岩带是世界知名的浅成低温热液型金矿成矿省,也是新西兰最为重要的金银矿矿集区,在环太平洋成矿带内占有重要的地位。科罗曼德尔半岛浅成低温热液型金矿主要赋存于科罗曼德尔群中新世安山岩和英安岩中,矿化类型主要为石英脉型和角砾岩型2种。矿床的成矿流体特征表现出明显的大气降水特征,并显示有少量的岩浆水加入,成矿物质具岩浆来源特征,为石英±方解石±冰长石±伊利石亚型浅成低温热液型金矿。区内金矿成矿时代为16.3~2.0Ma,主要集中于7.0~6.0Ma之间,金矿的大规模形成与诺特兰德火山弧与科尔维—劳火山弧共同作用有关,区域构造背景由挤压转变为伸展环境的转折期,为金矿形成的高峰期。区内零星出露与浅成低温热液型金矿化有关的斑岩型铜矿化表明,该地区具有较好的斑岩型铜矿化潜力。     

The role of tectonism in sequence development and facies distribution of Upper Oligocene cool-water carbonates: Coromandel Peninsula, New Zealand

The Torehina Formation is part of a cool‐water carbonate succession of Oligocene age in New Zealand that crops out on the Coromandel Peninsula, North Island. It contains two major transgressive sequences that record successive onlap of a once emergent landmass. The first sequence records marine flooding of non‐marine to marginal marine fan delta/estuarine facies, followed by deepening upward and formation of a low‐energy, deep (100+ m) muddy carbonate ramp. The capping sequence boundary is characterized by differential uplift and varies considerably in its character over a small (9 km²) area, varying from a burrowed glauconitic firmground to an erosional hardground to an undulatory marine contact to a palaeokarst with < 25 m relief. Sequence 2 sediments, which overlie the palaeokarst with minor (< 10°) angular unconformity, are clayey, marine (offshore) siltstones, whereas open‐marine limestones of equivalent age overlie the other boundary types with no apparent angular discordance. The siliciclastics could either represent lowstand channel deposits or may define interbank deposits contemporary with adjacent carbonates. Palaeogeographic restriction of palaeokarst and sequence 2 siliciclastics identifies a structural corridor oriented strike‐parallel to the adjacent Harauki Graben, which began to develop by this time. Palaeogeographical differences in the character of the basal limestone facies of sequence 2 also occur. These differences identify variation in accommodation during initial stages of deposition imposed by previous differential movement of fault blocks. As a result, relatively warm‐water (20 °C) Amphistegina‐bearing limestones in one area contrast with co‐existing deeper water, silty foraminiferal (benthic > planktic), echinoderm and bivalve limestones in another. This variation disappears upsection, which suggests that initial bathymetric differences were eliminated with renewed rise in sea level, yielding deeper water inner‐shelf sediment facies followed by the accumulation of still deeper, but higher energy, outer‐shelf bivalve and bryozoan facies. The sequence architecture of the Torehina Formation is controlled by tectonism, both long‐term subsidence and short‐term differential uplift. This arose as a result of increasing tectonic activity throughout proto‐New Zealand during the Late Oligocene. In such a system, local and regional variation in tectonism among adjacent basins can impose subtle to marked differences in the timing of sequence boundaries and the character of basin‐fill patterns.     

新西兰科罗曼德尔半岛金（铜）矿床地质特征、成因及找矿意义

新西兰科罗曼德尔半岛火山岩带是世界知名的浅成低温热液型金矿成矿省,也是新西兰最为重要的金银矿矿集区,在环太平洋成矿带内占有重要的地位。科罗曼德尔半岛浅成低温热液型金矿主要赋存于科罗曼德尔群中新世安山岩和英安岩中,矿化类型主要为石英脉型和角砾岩型2种。矿床的成矿流体特征表现出明显的大气降水特征,并显示有少量的岩浆水加入,成矿物质具岩浆来源特征,为石英±方解石±冰长石±伊利石亚型浅成低温热液型金矿。区内金矿成矿时代为16．3-2．0Ma,主要集中于7．0-6．0Ma之间,金矿的大规模形成与诺特兰德火山弧与科尔维一劳火山弧共同作用有关,区域构造背景由挤压转变为伸展环境的转折期,为金矿形成的高峰期。区内零星出露与浅成低温热液型金矿化有关的斑岩型铜矿化表明,该地区具有较好的斑岩型铜矿化潜力。