Melt migration and melt-rock reaction in the Alpine-Apennine peridotites:Insights on mantle dynamics in extending lithosphere     

Elisabetta Rampone  Giulio Borghini  Valentin Basch 《地学前缘(英文版)》2020,11(1):151-166

The compositional variability of the lithospheric mantle at extensional settings is largely caused by the reactive percolation of uprising melts in the thermal boundary layer and in lithospheric environments.The Alpine-Apennine(A-A)ophiolites are predominantly constituted by mantle peridotites and are widely thought to represent analogs of the oceanic lithosphere formed at ocean/continent transition and slow-to ultraslow-spreading settings.Structural and geochemical studies on the A-A mantle peridotites have revealed that they preserve significant compositional and isotopic heterogeneity at variable scale,reflecting a long-lived multi-stage melt migration,intrusion and melt-rock interaction history,occurred at different lithospheric depths during progressive uplift.The A-A mantle peridotites thus constitute a unique window on mantle dynamics and lithosphere-asthenosphere interactions in very slow spreading environments.In this work,we review field,microstructural and chemical-isotopic evidence on the major stages of melt percolation and melt-rock interaction recorded by the A-A peridotites and discuss their consequences in creating chemical-isotopic heterogeneities at variable scales and enhancing weakening and deformation of the extending mantle.Focus will be on three most important stages:(i)old(pre-Jurassic)pyroxenite emplacement,and the significant isotopic modification induced in the host mantle by pyroxenite-derived melts,(ii)melt-peridotite interactions during Jurassic mantle exhumation,i.e.the open-system reactive porous flow at spinel facies depths causing bulk depletion(origin of reactive harzburgites and dunites),and the shallower melt impregnation which originated plagioclase-rich peridotites and an overall mantle refertilization.We infer that migrating melts largely originated as shallow,variably depleted,melt fractions,and acquired Si-rich composition by reactive dissolution of mantle pyroxenes during upward migration.Such melt-rock reaction processes share significant similarities with those documented in modern oceanic peridotites from slow-to ultraslow-spreading environments and track the progressive exhumation of large mantle sectors at shallow depths in oceanic settings where a thicker thermal boundary layer exists,as a consequence of slow-spreading rate.  相似文献   

Abundance and spatial dynamics of bacterioplankton in the Seven Rila Lakes, Bulgaria     

Silvena Boteva  Ivan Traykov  Anelia Kenarova  Valentin Bogoev 《中国海洋湖沼学报》2010,28(3):451-458

In the high mountain oligotrophic Seven Rila Lakes (2 095–2 535 m a.s.l.) bacterial abundance was recorded in July and September 2006. In July, bacterial abundance (average (3.32±2.5)×10⁵ cell/ml) in the lakes correlated negatively with elevation, while in September (average (26.39±7.1)×10⁵ cell/ml) this pattern was altered and the greatest abundance of bacteria occurred at the highest ((39.05±1.5)×10⁵ cell/ml) and the lowest ((30.63±6.0)×10⁵ cell/ml) elevated lakes. Regression analyses suggested that the principal factor controlling bacterial abundance, in both July and September, was inorganic nitrogen (NO₃-N and NH₄-N; R ²=0.70, P<0.05). Other major regulating factors were temperature (R ²=0.66, P<0.03) in July and filter-feeding zooplankton (R ²=0.95, P<0.01) in September. All factors, except NO₃-N, had a positive effect on bacterial abundance.  相似文献   

The 2011 submarine volcanic eruption in El Hierro (Canary Islands)   总被引：1，自引：0，他引：1  

Juan Carlos Carracedo  Francisco Pérez Torrado  Alejandro Rodríguez González  Vicente Soler  José Luis Fernández Turiel  Valentin R. Troll  Sebastian Wiesmaier 《Geology Today》2012,28(2):53-58

Forty years after the Teneguía Volcano (La Palma, 1971), a submarine eruption took place off the town of La Restinga, south of El Hierro, the smallest and youngest island of the Canarian Archipelago. Precursors allowed an early detection of the event and its approximate location, suggesting it was submarine. Uncertainties derived from insufficient scientific information available to the authorities during the eruption, leading to disproportionate civil protection measures, which had an impact on the island's economy—based primarily on tourism—while residents experienced extra fear and distress.  相似文献   

Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions     

B?rje Dahren  Valentin R. Troll  Ulf B. Andersson  Jane P. Chadwick  Màiri F. Gardner  Kairly Jaxybulatov  Ivan Koulakov 《Contributions to Mineralogy and Petrology》2012,163(4):631-651

Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite of thermobarometric models. These include clinopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, clinopyroxene composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage in the region of 2–8 km beneath Krakatau, while existing seismic evidence points towards mid- to deep-crustal storage zone(s), at 9 and 22 km, respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7–12 km, while plagioclase records both shallow crustal (3–7 km) and sub-Moho (23–28 km) levels of crystallization. These magma storage regions coincide with well-constrained major lithological boundaries in the crust, implying that magma ascent and storage at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified a separate upper crustal (<7 km) and a lower to mid-crustal magma storage region (>7 km). Both petrological and seismic methods are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes.  相似文献   

Gold and Platinum-Group Element Analysis of Geochemical and Platinum Reference Materials Using Fluoroxidation Decomposition     

Valentin N. Mitkin 《Geostandards and Geoanalytical Research》2000,24(2):157-170

A novel method is described for the rapid dissolution of various geological, geochemical and related reference samples for the determination of Au and the platinum-group elements. The decomposition procedure is based on reaction with the fluoroxidants, liquid bromine trifluoride or molten potassium tetrafluorobromate. Results by this novel procedure are compared with data obtained by traditional methods of sample decomposition, including fire assay, autoclave techniques and an aqua regia leach. The oxidative fluorination procedure with the subsequent conversion of fluorocomplexes into the chloride form was found to be an effective and rapid method for the quantification of all the precious metals in a range of sample types.  相似文献   

Prairie Network Fireballs: Data of motion and ablation offireball bodies obtained by local-ballistic method applied tovariably-sliding path-segment     

Valentin V. Kalenichenko 《Astrophysics and Space Science》2000,274(3):489-502

The electronic version of an extensive catalogue of the results of the fireball physics inverse problem solution for the precise observational data of the Prairie Network Fireballs (DTHM-values) obtained by local-ballistic method of a variably-sliding path-segment contains a set of the physical parameters for the 480 fireball images of the 248 cosmic body entries into the Earth's atmosphere (PNVK-values). The parameters are: the fireball velocity with the corresponding values of the mass to cross-section area ratio for the fireball-generating body a teach measured point of the fireball path, the ablation factor and the ratio of the luminous fireball energy to the drag work for the body in the Earth's atmosphere using a factor inversely proportional to the density of the body. The catalogue of all PNVK-values, about 3.1 Mbytes in ASCII is accessible from ftp://ftp2.mao.kiev.ua/pub/astro/pnvk, files pnvk.cat and pnvks.cat This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Accuracy of tretyakov precipitation gauge: Result of wmo intercomparison     

Daqing Yang  Barry E. Goodison  John R. Metcalfe  Valentin S. Golubev  Esko Elomaa  Thilo Gunther  Roy Bates  Timothy Pangburn  Clayton L. Hanson  Douglas Emerson  Voilete Copaciu  Janja Milkovic 《水文研究》1995,9(8):877-895

The Tretyakov non-recording precipitation gauge has been used historically as the official precipitation measurement instrument in the Russian (formerly the USSR) climatic and hydrological station network and in a number of other European countries. From 1986 to 1993, the accuracy and performance of this gauge were evaluated during the WMO Solid Precipitation Measurement Intercomparison at 11 stations in Canada, the USA, Russia, Germany, Finland, Romania and Croatia. The double fence intercomparison reference (DFIR) was the reference standard used at all the Intercomparison stations in the Intercomparison. The Intercomparison data collected at the different sites are compatible with respect to the catch ratio (measured/DFIR) for the same gauge, when compared using mean wind speed at the height of the gauge orifice during the observation period. The Intercomparison data for the Tretyakov gauge were compiled from measurements made at these WMO intercomparison sites. These data represent a variety of climates, terrains and exposures. The effects of environmental factors, such as wind speed, wind direction, type of precipitation and temperature, on gauge catch ratios were investigated. Wind speed was found to be the most important factor determining the gauge catch and air temperature had a secondary effect when precipitation was classified into snow, mixed and rain. The results of the analysis of gauge catch ratio versus wind speed and temperature on a daily time step are presented for various types of precipitation. Independent checks of the correction equations against the DFIR have been conducted at those Intercomparison stations and a good agreement (difference less than 10%) has been obtained. The use of such adjustment procedures should significantly improve the accuracy and homogeneity of gauge-measured precipitation data over large regions of the former USSR and central Europe.  相似文献   

Compliance of the Parties to the Kyoto Protocol in the first commitment period     

Igor Shishlov  Romain Morel  Valentin Bellassen 《Climate Policy》2016,16(6):768-782

This article provides an ex post analysis of the compliance of the Parties to the Kyoto Protocol during the first commitment period (2008–2012) based on the final data for national GHG emissions and exchanges in carbon units that became available at the end of 2015. On the domestic level, among the 36 countries that fully participated in the Kyoto Protocol, only nine countries emitted higher levels of GHGs than committed and therefore had to resort to flexibility mechanisms. On the international level – i.e. after the use of flexibility mechanisms – all Annex B Parties are in compliance. Countries implemented different compliance strategies: purchasing carbon units abroad, stimulating the domestic use of carbon credits by the private sector and incentivizing domestic emission reductions through climate policies.

Overall, the countries party to the Protocol surpassed their aggregate commitment by an average 2.4 GtCO₂e yr^–1. Of the possible explanations for this overachievement, ‘hot-air’ was estimated at 2.2 GtCO₂e yr^–1, while accounting rules for land use, land-use change and forestry (LULUCF) further removed 0.4 GtCO₂e yr^–1 from the net result excluding LULUCF. The hypothetical participation of the US and Canada would have reduced this overachievement by a net 1 GtCO₂e yr^–1. None of these factors – some of which may be deemed illegitimate – would therefore on its own have led to global non-compliance, even without use of the 0.3 GtCO₂e of annual emissions reductions generated by the Clean Development Mechanism. The impact of domestic policies and ‘carbon leakage’ – neither of which is quantitatively assessed here – should not be neglected either.

Policy relevance

Given the ongoing evolution of the international climate regime and the adoption of the Paris Agreement in December 2015, we believe that there is a need to evaluate the results of the first commitment period of the Kyoto Protocol. To our knowledge there has been no overarching quantitative ex post assessment of the Kyoto Protocol based on the final emissions data for 2008–2012, which became available in late 2015. This article attempts to fill this gap, focusing on the domestic and international compliance of the Parties to the Kyoto Protocol in the first commitment period.  相似文献   

Volcanic particles in agriculture and gardening          下载免费PDF全文

Valentin R. Troll  Juan Carlos Carracedo  Beatrice Jägerup  Michael Streng  Abigail K. Barker  Frances M. Deegan  Francisco Perez‐Torrado  Alejandro Rodriguez‐Gonzalez  Harri Geiger 《Geology Today》2017,33(4):148-154

Volcanic pyroclasts of small size, such as lapilli and small pumice stones, are widely used in agriculture, gardening, and for pot plants as natural inorganic mulch. The technique of using pyroclasts to enhance topsoil stems from the eighteenth century, and specifically from the ad 1730–1736 eruption on Lanzarote. Critical observations on plant development during and after the eruption showed that the vegetation died when buried under a thick layer of lapilli, but grew vigorously when covered thinly. While the agriculture of Lanzarote was restricted to cereals before the eruption, it diversified to many kinds of fruit and vegetables afterwards, including the production of the famous Malvasía wines in the Canaries. The population of Lanzarote doubled in the years after the eruption, from about 5000 in 1730 to near 10 000 in 1768, predominantly as a result of the higher agricultural productivity. This outcome led to widespread use of lapilli and pumice fragments throughout the islands and eventually the rest of the globe. Lapilli and pumice provide vesicle space for moisture to be retained longer within the planting soil, which can create an environment for micro‐bacteria to thrive in. Through this route, nutrients from volcanic matter are transported into the surrounding soil where they become available to plant life. The detailed processes that operate within the pyroclasts are less well understood, such as the breakdown of nutrients from the rock matrix and transport into the soil by biological action. Further studies promise significant potential to optimize future agricultural efforts, particularly in otherwise arid areas of the globe.  相似文献   

Caldera formation in the Rum Central Igneous Complex, Scotland     

Valentin R. Troll  C. Henry Emeleus  Colin H. Donaldson 《Bulletin of Volcanology》2000,62(4-5):301-317

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