Investigation of temperature variations in borehole Kun-1 (Kunashir Island)

Doklady Earth Sciences -     

Temperature changes in the KUN-1 borehole, Kunashir Island, induced by the Tohoku Earthquake (March 11, 2011, M = 9.0)

The results of continuous (September 2010?CSeptember 2011) temperature monitoring in the 300-m-deep borehole on Kunashir Island are presented. There were several earthquakes, including the Tohoku one (March 3, 2012, M = 9.0), during the observation period, and they produced a significant coseismic response in the temperature field. The Tohoku earthquake was preceded by a constant decrease in temperature at the depth of 240 m with a mean rate of 0.02 K per month. The coseismic response was manifested in an abrupt (in à day) growth of temperature by 1.2 K. The relationships between the earthquake characteristics (magnitude, epicentral distance) and the amplitude of the coseismic temperature response in the borehole have been estimated. The deformation mechanism of the temperature response to earthquake preparation and implementation processes is suggested.     

Indian MORB-type mantle beneath the Kuril Island arc: Isotopic investigation of the mafic lavas of Kunashir Island

New data on the Hf, Pb, and Nd isotopes of the mafic rocks of various ages from Kunashir Island were used to address the nature of the sub-arc mantle of the southern segment of the Kuril island arc. At least since Late Cenozoic, its isotopic characteristics have been the MORB-type mantle of the Indian Ocean. Its boundary with the mantle reservoir of the Pacific MORB-type coincided probably with the Kuril-Kamchatka Trench.     

北京怀柔HR_（88－1）钻孔剖面磁性地层学研究

在系统古地磁样品采集、处理和测量的基础上，运用磁性地层学的研究方法，对北京怀柔地区ＨＲ（８８－１）钻孔剖面进行了详细地层划分，分别确定了该区上新统、下更新统、中更新统和上更新统的分布深度及地质年代。     

北京怀柔HR_（88－1）钻孔剖面磁性地层学研究

在系统古地磁样品采集、处理和测量的基础上，运用磁性地层学的研究方法，对北京怀柔地区ＨＲ（８８－１）钻孔剖面进行了详细地层划分，分别确定了该区上新统、下更新统、中更新统和上更新统的分布深度及地质年代。     

Fahlores of the Prasolovka Au-Ag volcanogenic deposit, Kunashir Island, Russian Far East

The chemical study shows that fahlores from the Prasolovka deposit are complex compounds with significant variations in their composition and the proportions of their constituent elements. Based on their major-element composition, they are subdivided into 3 species and 11 inter-and intra-species varieties. The chemical composition of the fahlores in different mineral assemblages from different ore types indicates that As fahlores subsequently replaced by Sb, Te-Sb, and Te fahlores during ore precipitation. The revealed evolution of the ore solutions from the early to late stages testifies that different ores at the Prasolovka deposit were formed under different physicochemical conditions.     

Pleistocene basaltic volcanism of Kunashir Island (Kuril island arc): Mineralogy,geochemistry, and results of computer simulation

New mineralogical, geochemical, and isotope data in combination with numerical modeling were used to reconstruct the physicochemical and geodynamic conditions of the formation of Pleistocene basalts of Kunashir Island. Although they are petrologically close to the Holocene basalts of Tyatya Volcano, their eruption occurred during a brief period of island arc extension, which was accompanied by the high degree melting of mantle wedge asthenosphere. Numerous geological, petrological, and paleogeographical data testify that Pleistocene is an important stage in the geodynamic reorganization of the Kuril island arc. This stage was responsible for uplifting of the southern islands above sea level accompanied by catastrophic endogenous events, deformation, topographic reorganization of the large area of the Sea of Japan and adjacent land, and final folding stage in the West Sakhalin Mountains.     

Role of back-arc tectonics in the origin of subduction magmas: new Sr,Nd, and Pb isotope data from Middle Miocene lavas of Kunashir Island (Kurile Island Arc)

Sr, Nd, and Pb isotope data for basaltic rocks of different ages from Kunashir Island (southern Kurile island arc) provide clues to investigate the subduction magmatic history. Signatures of a high-temperature slab component (melt and/or supercritical liquid produced by melting of slab sediments) involved in Early Miocene–Pleistocene back-arc basaltic magmatism indicate a relatively hot (> 800 °C) slab surface. Depleted isotope characteristics of Holocene basaltic lavas in both volcanic front and back arc indicate their origin with the participation of a cold aqueous fluid produced by dehydration of altered oceanic crust of the Pacific MORB type. The difference in geological, geochemical and isotope patterns in the Pleistocene and the Holocene lavas may be a response to stress change from extension to compression in the Kurile back-arc basin and the Kurile arc.     

Post-drilling destabilization of temperature profile in borehole Yaxcopoil-1, Mexico

As part of the International Continental Scientific Drilling Program (ICDP), the 1.5-km-deep borehole Yaxcopoil-1, located in the Chixculub meteor impact structure in Mexico, has undergone further study after drilling operations ceased. Temperature logs were repeated ten times at intervals 0.3–0.8, 15, 24 and 34 months after borehole shut-in. The logs bear a distinct signature of transient heat transfer by groundwater flow manifested by a gradual distortion of the linear temperature profile when a cold wave of 0.8–1.6°C amplitude was detected propagating downward from 145 to 312 m at a rate of 4–6 m/month. To understand the nature of this moving anomaly, a 20-day monitoring of the cold wave was carried out at a depth of 307 m that showed further cooling of 0.6°C during the first 16 days of the passage followed by temperature stabilisation. As an explanation of this unusual phenomenon, a theory is proposed, whereby the drilling mud has accumulated within the overlying and cooler highly porous and permeable karstic rocks during the drilling and migrates downward. The observed migration rate suggests a permeability higher than 10^?11 m². This indicates a high vulnerability to contamination of the only freshwater aquifer in the Yucatan region.     

Magmatism of Kunashir island (Kuril island arc) from aerogeophysical evidence

The existence of a lateral volcanic zoning in the Kuril island arc (KIA) was confirmed by the analysis of the 1: 50 000 scale maps of the abundances of natural radioactive elements (NRE). Trends of the NRE ratios were calculated for the magmatic complexes of the KIA, and their relation to fluidization processes was proved. Based on aerogeophysical data (maps of NRE ratios and the magnetic field), the main cyclic sequence of the formation of active volcanoes and magmatism was distinguished. Multicyclic volcanoes related to mantle sources usually show the predominance of calc-alkaline volcanic complexes, the occurrence of magnetite precipitation processes, and weak development of metasomatic aureoles. Other volcanoes connected to crustal sources are characterized by the development of calcic complexes and extensive hydrothermal-metasomatic systems.     

Chemical and isotopic characteristics of hydrocarbon gases from Mendeleev and Golovnin volcanoes,Kunashir Island

This paper reports the analysis of the distribution of hydrocarbon and other gases in Mendeleev and Golovnin volcanoes and other occurrences of Kunashir Island. It was shown that, in addition to methane, the solfatara gases and gases dissolved in thermal waters contain ethane, propane, and butane. The volume concentration of methane in gas samples was no higher than 0.4 vol %. Carbon isotopes were analyzed in methane, ethane, and carbon dioxide in free and dissolved states. The hydrocarbon gases of Kunashir I. are of the thermogenic and metamorphogenic types, and their distribution depends on the position of springs relative to the eruptive centers of the volcanoes. Thermogenic gases are probably products of the high-temperature transformation of sedimentary organic matter buried during the formation of volcanic edifices. General gas geochemical characteristics are presented for Kuril volcanoes, and it was found that hydrocarbon generation in the sediments of the Kuril Basin increases toward volcanic edifices.     

Role of backarc processes in the origin of across-arc geochemical zoning in volcanics of early evolutionary stages in Kunashir Island

Geochemical data obtained on volcanic rocks produced during the early evolutionary stages in Kunashir Island provide insight into certain important aspect of the evolution of the subduction system. The mafic lavas of all age intervals exhibit clearly pronounced across-arc geochemical zoning, which implies that these rocks were produced in the environment of a subducted oceanic slab. The high Ba/Th and U/Th ratios of basalts from the frontal zones suggest that an important role in magma generation was played by a low-temperature aqueous fluid. The arc lavas of the Early Miocene, Pliocene, and Pliocene-Pleistocene episodes in the evolution of the island arc system provide evidence of the melting of subducted sediments, which testifies, when considered together with the calculated P-T conditions under which the high-Mg basalts were derived, that backarc tectono-magmatic processes affected subduction-related magmatic generation. Active mantle diapirism and volcanic activity in the opening Kurile Basin resulted in the heating of the suprasubduction mantle in the rear zone, the involvement of the upper sedimentary layer of the oceanic slab in the process of melting, and the eventual generation of basaltic magmas with unusual geochemical characteristics.     

高温钻孔测斜仪研制

针对高温高压干热岩钻井定位轨迹探测设备存在耐高温高压性能差、稳定性差、测量精度不高、电能消耗大等问题,研制一套高温钻孔测斜装置,解决高温高压多点连续钻孔测斜及测温问题。选择耐高温元器件,设计控制和测量电路;采用自动间歇供电方法,减少散热,降低功耗;设计保温探管、承压探管,利用ANSYS有限元软件对承压外管的屈服强度和保温探管的温度场与压力场进行耦合分析和校核。最后进行仿真测试和野外试验,根据测试数据表明,设备能在280℃和12 MPa高温高压环境条件下实现深井倾角、方位角、工具面向角及温度的测量。     

Estimating heat flow from an unsteady temperature log of submarine borehole BDP-98 (Lake Baikal)

We have applied the method of one temperature log suggested by Kutasov in 1987 to process an unsteady temperature log of the 674 m deep submarine borehole BDP-98-2 (Akademichesky Ridge, Lake Baikal) and found it suitable to reconstruct the primary steady thermal gradient not disturbed by drilling. The steady gradient we derived using a special formalism, with reference to drilling conditions and measured thermal properties of sediments, was 63 mK/m, more than two times the unsteady gradient at different depths. Heat flow calculated with this gradient and a mean thermal conductivity of 1.1 W/(m·K) was 70 mW/m², which is consistent with earlier geothermal data from the same area. Thus, the one-log procedure is a useful tool to predict the original undisturbed thermal gradients and estimate approximate heat flows if a single unsteady temperature log is available.     

Behavior of rare earth elements during mixing of different types of water (Kunashir,the Kurile Islands)

The fractionation of rare earth elements (REE) was evaluated under the conditions of natural acidic water mixing with fresh and sea waters using the example of unique objects on Kunashir Island (the Kislaya and Lesnaya rivers). It was shown that the concentrations and fractionation of REE in the water types considered are diverse and controlled by a number of factors. The concentrations of dissolved REE normalized to the North American Shale Composite show an increase from the light to the heavy REE, which reflects both the character of the REE input with the thermal waters and the more active sorption of the light REE and their preferential removal to suspended solids. This is supported by the similar REE patterns in the suspended matter of the Kislaya River. The mixing of the waters of the Kislaya and Lesnaya rivers, which are assigned to different chemical types, is accompanied by active REE coprecipitation with Fe, Al, and Mn oxides and the more extensive removal of the light REE compared with the heavy REE. During acidic water mixing with seawater, more than 80% of the REE were precipitated at a salinity of 8‰.     

Disperse megaspores in the Lower Visean deposits of the Kaluga oblast (1P/A Aleksandrovskaya borehole)

Disperse megaspores were first found in the Lower Visean deposits of the Kaluga region (1P/A borehole). A layered distribution of the megaspores in the studied section is shown. A large number of megaspores were established in the lower part of the section of the Bobrikovskian deposits. Higher along the section, there is a trend to a decrease in the number of megaspores until they disappear completely in the Tula deposits. Two megaspore assemblages were identified. A great variety of species was observed in the lower assemblage; the dominant megaspores are Zonalesporites brasserti and Aphanozonatisporites triglobatus. The only dominant species was recorded in the upper assemblage, Zonalesporites brasserti, with a low species diversity of the entire assemblage. The miospore and megaspore assemblages that are typical of the Lower Visean in the section of the analyzed borehole are compared.     

The nature of climate and climatic variations

The climate system consists of the atmosphere, the oceans, the cryosphere (land ice, snow, sea ice), the lithosphere, and the biomass. The behavior of the individual components of the system is governed by processes occurring over a broad range of time and space scales. The components are coupled by physical, biological, and chemical processes, and the coupled system seems capable of undergoing fluctuations on all time scales. In addition to these “internal” climatic processes, external processes (such as variability in the solar irradiance or human activities) must also be considered. Space and time scales of climatic variability are reviewed, with emphasis on the Holocene. Regional patterns of climatic variability may be associated with changes in the amplitude and longitudinal position of the long waves in the westerlies of midlatitudes, and with changes in the intensity and latitude of meridional circulation features such as the Hadley cell. Possible examples of this are mentioned. The variance spectrum of climatic time series is described and certain implications for climate modeling are suggested.     

Boron isotope variations in nature: a synthesis

The large relative mass difference between the two stable isotopes of boron, ¹⁰B and ¹¹B, and the high geochemical reactivity of boron lead to significant isotope fractionation by natural processes. Published ¹¹B values (relative to the NBS SRM-951 standard) span a wide range of 90. The lowest ¹¹B values around — 30 are reported for non-marine evaporite minerals and certain tourmalines. The most ¹¹B-enriched reservoir known to date are brines from Australian salt lakes and the Dead Sea of Israel with ¹¹B values up to +59. Dissolved boron in present-day seawater has a constant world-wide ¹¹B value of + 39.5. In this paper, available ¹¹B data of a variety of natural fluid and solid samples from different geological environments are compiled and some of the most relevant aspects, including possible tracer applications of boron-isotope geochemistry, are summarized.

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Résumé La grande différence relative de masse entre les isotopes stables du bore, ¹⁰B et ¹¹B, et la grande réactivité geochimique du bore ont pour conséquence un fractionnement isotopique naturel important. Les valeurs de ¹¹B publiées (par rapport au standard NBS SRM-951) varient de 90. Les valeurs de ¹¹B les plus basses (–30) correspondent aux evaporites non-marines et à certaines tourmalines. Le réservoir le plus enrichi en ¹¹B est représenté par les saumures des lacs salés d' Australie et par la Mer Morte en Israël, qui ont des valuers de ¹¹B allent jusqu'à + 59. L'eau de mer a une valeur de ¹¹B mondialement constante de + 39.5. Des valeurs de ¹¹B des solutions naturelles ainsi que des roches et minéraux de différentes origines, publiées jusqu'à présent, sont présentées ici. En outre quelques aspects importants concernant la géochimie des isotopes du bore y compris quelques applications sont exposés.

     

Organic carbon content and carbon isotope variations across the Permo-Triassic boundary in the Gartnerkofel-1 borehole,Carnic Alps,Austria

The Gartnerkofel borehole is one of the most thoroughly studied and described Permo-Triassic sections in the world. Detailed bulk organic carbon isotope studies show a negative base shift from ? 24‰ to ? 28‰ in the Latest Permian which latter value persists into the Earliest Triassic after which it decreases slightly to ? 26‰. Two strongly negative peaks of > ? 38‰ in the Latest Permian and a lesser peak of ? 31‰ in the Early Triassic are too negative to be due to a greater proportion of more negative organic matter and must be due to very negative methane effects. The overall change to more negative values across the Bulla/Tesero boundary fits the relative rise in sea level for this transition based on the facies changes. A positive shift in organic carbon isotope values at the Late Permian Event Horizon may be due to an increase in land-derived organic detritus at this level—a feature shown by all Tethyan Permo-Triassic boundary sections though these other sections do not have the same values. Carbonate carbon isotope trends are similar in all sections dropping by 2–3 units across the Permo-Triassic boundary. Gartnerkofel carbonate oxygen values are surprisingly, considering the ubiquitous dolomitization, compatible with values elsewhere and indicate reasonable tropical temperatures of 60 °C in the Latest Permian sabkhas to 20–40 °C in the overlying marine transition beds. Increased land-derived input at the Late Permian Event Horizon may be due to offshore transport by tsunamis whose deposits have been recognized in India at this level.