Terrestrial heat flow at Hirabayashi on Awaji Island, south-west Japan

Abstract Terrestrial heat flow at Hirabayashi in Awaji Island, south-west Japan, was investigated using the deep borehole penetrating through the Nojima Fault, which was activated during the 1995 Hyogo-ken Nanbu earthquake, by measuring the thermal conductivity of basement rocks. Using the temperature logging data, the value of terrestrial heat flow in Hirabayashi was found to be 56.6 ± 5.2 mW/m². The relationship between cut-off depth of aftershocks of the Hyogo-ken Nanbu earthquake in Hirabayashi and terrestrial heat flow are discussed. The cut-off depth roughly corresponds to isotherms of 300°C.     

Terrestrial heat flow in Japan

Terrestrial heat flow, Q=K×ΔT/ΔZ cal/cm² sec has been determined at 51 localities (39 on land and 12 in the sea) in and around the Japanese Islands. The average values of observed heat flow in land and sea are 1.53µ cal/cm²sec and 1.48µcal/cm²sec respectively. These value do not differ greatly from the world’s averages. The outstanding features of the heat flow distribution are as follows:a) High heat flow region (Q>2.0µcal/cm²sec) exists in the Inner Zone of the Honshu Arc. This region of high heat flow is more distinct in the northeastern Japan than in the southwestern Japan.b) The High heat flow region seems to extend, through the Fossa Magna area, down to the Izu-Mariana Arc.c) It is also probable that a similar high heat flow zone exists in the inner side of the Kurile Arc.d) These zones of high heat flow precisely coincide with the zones of the Cenozoic orogeny in the area concerned.e) Far off the coast of the northeastern Japan, the area at about 150° E may be a high heat flow region.f) Low heat flow (Q<1.0µcal/cm²sec) prevails in the Pacific coast side of the northeastern Japan and in the oceanic area directly east of it, including the area of the Japan Trench.g) The region bounded by the above mentioned high and low heat flow regions has heat flow which is more or less normal. Based on these measurements, a « steady state ” temperature distribution in the crust has been calculated for each of the above regions of high, low and intermediate heat flow, and it was found that there is a large temperature differences between the bottom of the crust of the high and low heat flow regions: the temperature at the Moho boundary in the high heat flow regions should be as high as some 800～1000°C (d=27 km), whereas that under the low heat flow region should be only about 200°C (d=23 km). The high general temperature at the Moho under the high heat flow region seems to favor a production of magma in the upper mantle. Calculated Moho temperatures disfavor the hypothesis that the Moho boundary is due to phase transition.     

Terrestrial heat flow in Hungary

Summary The geothermal gradient in the Carpathian Basin lies between 40–70 C/km. According to careful measurements in shafts the value of terrestrial heat flow in the southern part of Hungary is (2.055–3.066)·10^–6 cal/cm² sec. These measurements are believed the first ever attempted in continental Europe. Systematic heat flow measurement are being extended to other part of this country.     

Terrestrial heat flow in Hungarian Permian strata

Summary Latest measurements of terrestrial heat flow in the Hungarian and Russian parts of the Carpathian basin confirm previously measured high flow values between 2.0–3.3 cal/cm² sec. Recent measurement in the Permian anticline structure of the Mecseck. Mts. in Hungary gave 2.4 cal/cm²sec, whereas in the Russian part of the basin, near to the Hungarian border 2.6 cal/cm² sec was measured in Miocene sediments. For more than 100000 km² surface of the Carpathian basin covered by Hungary and parts of Slovakia and Russian the high heat flow is an established fact.     

Genesis of lavas of the Taupo Volcanic Zone, North Island, New Zealand

The Taupo Volcanic Zone forms part of the Taupo-Hikurangi subduction system, and comprises five volcanic centres: Tongariro, Taupo, Maroa, Okataina and Rotorua. Tongariro Volcanic Centre is formed almost entirely of andesite while the other four centres contain predominantly rhyolitic volcanics and later fissure eruptions of high-Al basalt. Estimated total volume of each lava type are as follows: 2 km³ of high-Al basalt (< 0.1%); 260 km³ of andesite (< 2.5%); 5 km³ of dacite (< 0.1%); > 10,000 km³ of rhyolite and ignimbrite (> 97.4%).The location of the andesites and vent alignments suggest a source from a subduction zone underlying the area. However, the lavas differ chemically from island-arc andesites such as those of Tonga; in particular by having higher contents of the alkali elements, light REE and Sr and Pb isotopes. This suggests some crustal contamination, and it is considered that this may occur beneath the wide accretionary prism of the subduction system. Amphibolite of the subduction zone will break down between 80 and 100 km and a partial melt will rise. A multi-stage process of magma genesis is then likely to occur. High-Al basalts are thought to be derived from partial melting of a garnet-free peridotite near the top of the mantle wedge overlying the subduction zone, locations of the vents controlled largely by faults within the crust. Rhyolites and ignimbrites were probably derived from partial melting of Mesozoic greywacke and argillite under the Taupo Volcanic Zone. Initial partial melting may have been due to hydration of the base of the crust; the “water” having come from dehydration of the downgoing slab. The partial melts would rise to form granodiorite plutons and final release of the magma to form rhyolites and ignimbrites was allowed because of extension within the Taupo graben.Dacites of the Bay of Plenty probably resulted from mixing of andesitic magma with small amounts of rhyolitic magma, but those on the eastern side of the Rotorua-Taupo area were more likely formed by a higher degree of partial melting of the Mesozoic greywacke-argillite basement. This may be due to intrusion of andesite magma on this side of the Taupo volcanic zone.     

Lacustrine shore platforms at Lake Waikaremoana,North Island,New Zealand

This paper examines the morphology and processes governing the development of shore platforms at Lake Waikaremoana, North Island, New Zealand. Shore platforms at Lake Waikaremoana are recent features, and were formed when a new sequence of shoreline development was initiated, due to lowering of the lake by 5 m in 1946 for hydroelectric power development. Three predominant platform morphologies were identified around the lake. These include gently sloping platforms (c.1·5 to 3·9°), ramp platforms (c.6·8 to 9·2°), and concave ramp platforms (c.7·9 to 12°). Platform widths ranged from 11 to 31 m, with the gently sloping platforms characterized by the widest morphologies. Erosion rates were estimated using perched sandstone boulders and were found to range from 3·4 to 12·5 mm a^?1, with a mean erosion rate of 5·9 mm a^?1. Higher rates of erosion were identified at lower platform elevations, due to a greater frequency of wetting and drying cycles coincident with storm waves, while lower erosion rates were identified at higher elevations. Field evidence suggests that shore platforms at Lake Waikaremoana were likely initiated and continue to develop as a result of subaerial wetting and drying cycles. Waves, coincident with fluctuating lake levels, play an important role by removing the weathered material from the platforms, and appear to control the width of the platforms. A conceptual model of platform development is presented, and analogies are drawn between this model, and the formation of shore platforms in oceanic environments. Copyright © 2002 John Wiley & Sons, Ltd.     

Terrestrial heat flow in various parts of India

Results of heat flow studies made in different parts of India including Kolar Gold Field, Cuddapah basin, Singhbhum thrust zone, Aravalli mountain system of Precambrian age, Godavary valley of Mesozoic age and Cambay basin of Cenozoic age are discussed. Heat flow has been found to be low in the southern part of the Preambrian shield. Relatively higher values have been obtained along the northeastern (Singhbhum) and the northwestern parts of the shield (Aravallies). High heat flow has been found along the southeastern part of the Godavary valley and the Cambay basin. The correlation of heat flow with geology and tectonic history in the respective areas is discussed.     

Early deformation fabrics of melange in the Mesozoic Waipapa Terrane, North Island, New Zealand

Abstract The Waipapa Terrane in northern North Island, New Zealand, is a Mesozoic accretion-ary complex formed along the Gondwana margin. It contains abundant melange rocks with distinctive characteristics. Precise analyses of their mesoscopic fabrics in Waiheke Island near Auckland have revealed the following sequence of deformation. The earliest phase of deformation of the sandstone/mudstone association, which is the main constituent of this terrane, originated by chaotic mixing of sand and mud due to liquidization of water-saturated, poorly consolidated sediments. The second phase was characterized by hydrofracturing and subsequent forceful injection of ductile mud into rather brittle sand. Local intrusions of sand forming dykes and sills followed these events, as well as intrusions of pelagic/hemipelagic green argillite originally underlying the sandstone/mudstone association. An abundant occurrence of these mixing and multi-stage injection/intrusion fabrics strongly suggest that the Waipapa Terrane around the study area was a site of high pore-fluid pressure. Scaly-foliated melange fabrics with monoclinic symmetry, originating from layer-parallel shearing, were then locally superimposed on the pre-existing melange fabrics. Similar scaly-foliated fabrics also developed in the chert beds originally intercalated between the green argillite and the uppermost part of the oceanic crust. These scaly fabrics might have been related to the regional stacking and juxtaposition of the accreted sediments. The sequence and variation in style of deformation forming the melange fabrics presumably reflected changes in porosity and state of compaction of accreted sediments in a shallow tectonic level.     

Terrestrial heat flow in the natural steam field at Larderello

Summary Measurements of thermal gradients and rock conductivity in the steam field of Larderello, along a cross section of about 12 km length, reveal a great anomaly of terrestrial heat flow. Heat flow varies between 6 and 14 cal-cm² sec, while thermal gradients are between 200 and 800 deg C-km. The measurements show that heat flow values characterize better the productive areas than thermal gradient anomalies. Knowing the heat flow it is possible to set up the thermal balance of the steam producing area, which is of considerable importance in planning the production of the steam field.     

查干凹陷大地热流

查干凹陷是银根—额济纳旗盆地最具勘探潜力的凹陷, 但是查干凹陷及整个银根—额济纳旗盆地的大地热流研究仍为空白, 严重制约该盆地的油气资源的评价. 本文通过测试19口井107块岩芯的岩石热导率和岩石热导率原位校正, 利用协和平均公式计算得到查干凹陷各地层的岩石热导率大小; 并利用9口井的温度数据, 结合岩石热导率数据对查干凹陷的地温梯度和大地热流进行了计算. 研究结果表明查干凹陷具有构造稳定区和构造活动区之间的中温型地温场特征, 其平均地温梯度和大地热流分别为33.6℃/km, 74.5 mW/m2. 本文的研究成果为查干凹陷及银根—额济纳旗盆地油气资源评价提供地热参数.     

Magnetic polarity stratigraphy of a Plio-Pleistocene marine sequence of North Island, New Zealand

Thick sequences of relatively undisturbed Plio-Pleistocene sediments in the Wanganui Basin, North Island, New Zealand consist of well exposed silts, clayey silts, sandstones, rare limestones, and several tephras. Oriented specimens were collected from a section more than 2500 m thick and palaeomagnetic measurements were made using A.C. demagnetisations in fields up to 35 mT. With the aid of tephrochronology the age of the upper sequence is now well established and falls within the Matuyama epoch. The lower two-thirds of the section except for the basal 500 m is predominantly normally magnetised and is interpreted as a very extended sequence of the Gauss epoch. The lowest 500 m then represents the Gilbert epoch. The Plio-Pleistocene boundary, as defined at Vrica, Italy, falls within the upper part of the section studied, in the Upper Nukumaruan stage. For the first time a reliable correlation is made with the international boundary, using as intermediaries the palaeomagnetic and tephrostratigraphy of deep-sea cores from the southwest Pacific.

As a result of the high deposition rate (of the order of 1.2 m/ky) and the apparent lack of unconformities, the temporal resolution is high; short-lived magnetic events are detected, especially in the lower Matuyama and upper Gauss epochs. These generally correlate well with events reported from other extended sections.     

Identifying and linking source areas of flow and P transport in dairy‐grazed headwater catchments,North Island,New Zealand

We examined the applicability of the critical‐source area (CSA) concept to the dairy‐grazed 192‐ha Upper Toenepi catchment and its 8·7‐ha Kiwitahi sub‐catchment, New Zealand. We evaluated if phosphorus (P) transport from land into stream is dominated by saturation‐excess (SE) and infiltration‐excess (IE) runoff during stormflow and by sub‐surface (<1·5 m depth) flows during baseflow. We measured stream flow and shallow groundwater levels, collected monthly stream, tile drain (TDA) and groundwater samples, and flow‐proportional stream samples from the Kiwitahi sub‐catchment, and determined their dissolved reactive phosphorus (DRP) and total phosphorus (TP) concentrations. In the Kiwitahi sub‐catchment, during storm events, IE contributions were significant. Contributions from SE appeared significant in the Upper Toenepi catchment. However, in both catchments, sub‐surface contributions dominated stormflow and baseflow periods. Absence of water table at the surface and the water table gradient towards the stream indicated that P transport during events was not limited to surface runoff. The dynamics of the groundwater table and the occurrence of SE areas were influenced by proximity to the stream and hillslope positions. Baseflow accounted for 42% of the annual flow in the Kiwitahi sub‐catchment, and contributed 37 and 52% to the DRP and TP loads, respectively. The P transport during baseflow appeared equally important as P losses from CSAs during stormflow. The close resemblance in P levels between groundwater and stream samples during baseflow demonstrates the importance of shallow groundwater for stream flow. In the Upper Toenepi catchment, contributions from effluent ponds (EFFs) dominated P loads. Management strategies should focus on controlling P release from EFFs, and on decreasing Olsen P concentrations in soil to minimize leaching of P via sub‐surface flow to streams. Research is needed to quantify the role of sub‐surface flow as well as to expand management strategies to minimize P transfers during stormflow and baseflow conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Cenozoic volcanism, stress gradient and back-arc opening in the North Island, New Zealand: Origin of Taupo-Rotorua Depression

Abstract Extensive subduction-related and intraplate volcanism characterize Cenozoic magmatism in the North Is., New Zealand. Volcanics in the central North Is., predominantly intermediate to felsic, form above the dipping seismic zone and show tectonic/geochemical features common to magmatism in most subduction zones. Basaltic volcanism in Northland, the northern part of the North Is., has chemical characteristics typical of intraplate magmatism and may be caused by the upwelling of asthenospheric materials from deeper parts of the mantle. The rifting just behind the present volcanic front (the Taupo-Rotorua Depression), which follows the trench ward migration of the volcanic front and the gradual steepening of the subducted slab, is also a feature of the North Is. A possible mechanism for the back-arc rifting in the area is injection of asthenospheric materials into the mantle wedge; this asthenospheric flow results from the mantle upwelling beneath Northland and pushes both the rigid fore-arc mantle wedge and the subducted slab trenchwards. This mechanism is also consistent with the stress fields in the North Is.: dilatation in Northland, northwest-southeast tension in the Taupo-Rotorua Depression, and the northeast-southwest compression in the fore-arc region.     

Slope control on the frequency distribution of shallow landslides and associated soil properties,North Island,New Zealand

The extrapolation of results from field trials to larger areas of land for purposes of regional impact assessment is an important issue in geomorphology, particularly for landform properties that show high stochastic variability in space and time, such as shallow landslide erosion. It is shown in this study, that by identifying the main driver for spatial variability in shallow landslide erosion at field scales, namely slope angle, it is possible to develop a set of generic functions for assessing the impact of landslides on selected soil properties at larger spatial scales and over longer time periods. Research was conducted within an area of pastoral soft‐rock Tertiary hill country in the North Island of New Zealand that is subject to infrequent high intensity rainfall events, producing numerous landslides, most of which are smaller than several hundred square metres in size and remove soil to shallow depths. All landslides were mapped within a 0·6 km² area and registered to a high resolution (2 m) slope map to show that few landslides occur on slopes < 20° and 95% were on slopes > 24°. The areal density of landslides from all historical events showed an approximately linear increase with slope above 24°. Integrating landslide densities with soil recovery data demonstrates that the average value of a soil property fluctuates in a ‘saw‐tooth’ fashion through time with the overall shape of the curve controlled by the frequency of landslide inducing storm events and recovery rate of the soil property between events. Despite such fluctuations, there are gradual declines of 7·5% in average total carbon content of topsoil and 9·5% in average soil depth to bedrock, since the time of forest clearance. Results have application to large‐scale sediment budget and water quality models and to the New Zealand Soil Carbon Monitoring System (CMS). Copyright © 2012 John Wiley & Sons, Ltd.