Genesis of a Magnetite Layer in the Gabbro-10 Intrusion,Monchegorsk Complex,Kola Region: U–Pb SHRIMP-II Dating of Metadiorites     

Groshev  N. Yu.  Pripachkin  P. V.  Karykowski  B. T.  Malygina  A. V.  Rodionov  N. V.  Belyatsky  B. V. 《Geology of Ore Deposits》2018,60(6):486-496

Geology of Ore Deposits - The Gabbro-10 intrusion is located in the southeastern part of the Early Proterozoic Monchegorsk layered complex of the Kola region. The intrusion, 1.4 × 0.7 km in...  相似文献   

U-Pb SHRIMP geochronology of Th-poor, hydrothermal monazite: An example from the Llallagua tin-porphyry deposit, Bolivia     

U. Kempe  B. Lehmann  N. Rodionov  U. Schwengfelder 《Geochimica et cosmochimica acta》2008,72(17):4352-4366

In situ U-Pb SHRIMP analysis of hydrothermal monazite virtually free of Th and poor in U (<0.2 ppm Th, 40-103 ppm U) from the world-class Llallagua tin porphyry deposit in Bolivia defines a mineralization age of 23.4 ± 2.2 Ma (MSWD 0.48) confirming earlier K-Ar sericite alteration age data. These ages are, however, in contrast with a weighted mean single crystal ²⁰⁷Pb/²⁰⁶Pb evaporation age of 39.3 ± 6.0 Ma, and a related Pb-Pb inverse isochron age of 42.4 ± 4.0 Ma (MSWD 0.66) on zircon from a post-porphyry dike, as well as with an earlier single crystal Sm-Nd apatite isochron age.Our data points to a significant time gap between emplacement of the ore-hosting porphyry intrusion (magmatism) and its hydrothermal overprint (tin mineralization), suggesting long-lived magmatic-hydrothermal activity in this part of the Andean back-arc crust. The decoupling of porphyry magmatism and hydrothermal activity may explain the unusual occurrence of relatively little fractionated felsic rocks together with extensive tin mineralization.Our study demonstrates the usefulness of the application of the U-Pb SHRIMP method to direct age determination of ore mineralization using Th-poor hydrothermal monazite even when dealing with geological young events. The common assumption of synchronous magmatism and hydrothermal ore formation in porphyry systems may not always be warranted.  相似文献   

Modelling of thermochemical plumes and implications for the origin of the Siberian traps     

Nickolay L. Dobretsov  Alexey A. Kirdyashkin  Anatoliy G. Kirdyashkin  Valery A. Vernikovsky  Igor N. Gladkov 《Lithos》2008,100(1-4):66-92

Thermochemical plumes form at the base of the lower mantle as a consequence of heat flow from the outer core and the presence of local chemical doping that decreases the melting temperature. Theoretical and experimental modelling of thermochemical plumes show that the diameter of a plume conduit remains practically constant during plume ascent. However, when the top of a plume reaches a refractory layer, whose melting temperature is higher than the melt temperature in the plume conduit, a mushroom-shaped plume head develops. Main parameters (melt viscosity, ascent time, ascent velocity, temperature differences in the plume conduit, and thermal power) are presented for a thermochemical plume ascending from the core–mantle boundary. In addition, the following relationships are developed: the pressure distribution in the plume conduit during the ascent of a plume, conditions for eruption-conduit formation, the effect of the P–T conditions and controls on the shape and size of a plume top, heat transfer between a thermochemical plume and the lithosphere (when the plume reaches the bottom of a refractory layer in the lithosphere), and eruption volume versus the time interval t₁ between plume formation and eruption. These relationships are used to determine thermal power and time t₁ for the Tunguska syneclise and the Siberian traps as a whole.

The Siberian and other trap provinces are characterized by giant volumes of lavas and sills formed a very short time period. Data permit a model for superplumes with three stages of formation: early (variable picrites and alkali basalts), main (tholeiite plateau basalts), and final (ultrabasic and alkaline lavas and intrusions). These stages reflect the evolution of a superplume from the ascent of one or several independent plumes, through the formation of thick lenses of mantle melts underplating the lithosphere and, finally, intrusion and extrusion of differentiated mantle melts. Synchronous syenite–granite intrusions and bimodal volcanism abundant in the margins of the Siberian traps are the result of melting of the lower crust at depths of 65–70 km under the effect of plume melts.  相似文献   

Magnetostratigraphy of the Middle–Upper Cambrian Verkhnyaya Lena Group and Lower Ordovician Ust-Kut formation in the southern Siberian Platform     

V. P. Rodionov 《Stratigraphy and Geological Correlation》2016,24(5):464-485

The available paleomagnetic data on the Verkhnyaya Lena Group from different areas of the southern Siberian Platform are revised. The group rests unconformably upon the Lower Cambrian strata and is overlain by Lower Ordovician rocks, which determines conditionally the age of its red-colored deposits. Paleomagnetic correlation of composite sections through the region using defined zones of normal and reversed magnetic polarity serves as a basis for development of the magnetostratigraphic scale for the Verkhnyaya Lena Group. The scale includes nine magnetic zones, which play the role of markers; seven of them are traceable in all the examined sections of the southern Siberian Platform. By the distribution of zones with normal (N) and reversed (R) polarity, the magnetostratigraphic scale is subdivided into three parts. Its lower part is represented by reversed polarity, which is characteristic of the second half of the Lower Cambrian. The middle part is characterized by frequently alternating zones with normal and reversed polarity corresponding to the Middle Cambrian. The upper part of the scale corresponds to the interval of reversed polarity characteristic of the Upper Cambrian and Lower Ordovician. The Middle–Upper Cambrian boundary is located near the last N–R reversal of the geomagnetic field in the Cambrian. The magnetostratigraphic scale includes nine orthozones united into three superzones, which are attributed to two hyperzones of magnetic polarity.  相似文献   

Late Jurassic (151–147 Ma) Dike Magmatism of the Northeastern Margin of the Siberian Craton     

Fridovsky  V. Yu.  Yakovleva  K. Yu.  Vernikovskaya  A. E.  Vernikovsky  V. A.  Rodionov  N. V.  Lokhov  K. I. 《Doklady Earth Sciences》2020,491(1):117-120

Doklady Earth Sciences - Dikes of intermediate and felsic composition from the area of the Vyun deposit and the Shumnyi occurrence, both of which belong to the Yano–Kolyma gold belt...  相似文献   

Vyacheslav Ivanovich Kovalenko (on his 70th birthday)     

A. I. Khanchuk  S. M. Rodionov  G. L. Kirillova 《Geotectonics》2006,40(6):483-484

Chronicle

Vyacheslav Ivanovich Kovalenko (on his 70th birthday)  相似文献   

U-Pb zircon age of diorites of the Chusovsk Gabbrodiorite Series of the Verkhisetsk Massif (Middle Urals)     

E. A. Zinkova  G. B. Fershtater  N. V. Rodionov 《Doklady Earth Sciences》2009,425(1):239-242

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Tracking volcanic sulfur dioxide clouds for aviation hazard mitigation     

Simon A. Carn  Arlin J. Krueger  Nickolay A. Krotkov  Kai Yang  Keith Evans 《Natural Hazards》2009,51(2):325-343

Satellite measurements of volcanic sulfur dioxide (SO₂) emissions can provide critical information for aviation hazard mitigation, particularly when ash detection techniques fail. Recent developments in space-based SO₂ monitoring are discussed, focusing on daily, global ultraviolet (UV) measurements by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite. OMI’s high sensitivity to SO₂ permits long-range tracking of volcanic clouds in the upper troposphere and lower stratosphere (UTLS) and accurate mapping of their perimeters to facilitate avoidance. Examples from 2006 to 2007 include eruptions of Soufriere Hills (Montserrat), Rabaul (Papua New Guinea), Nyamuragira (DR Congo), and Jebel at Tair (Yemen). A tendency for some volcanic clouds to occupy the jet stream suggests an increased threat to aircraft that exploit this phenomenon. Synergy between NASA A-Train sensors such as OMI and the Atmospheric Infrared Sounder (AIRS) on the Aqua satellite can provide critical information on volcanic cloud altitude. OMI and AIRS SO₂ data products are being produced in near real-time for distribution to Volcanic Ash Advisory Centers (VAACs) via a NOAA website. Operational issues arising from these improved SO₂ measurements include the reliability of SO₂ as proxy for co-erupted ash, the duration of VAAC advisories for long-lived volcanic clouds, and the potential effects of elevated concentrations of SO₂ and sulfate aerosol in ash-poor clouds on aircraft and avionics (including cumulative effects after multiple inadvertent transits through dilute clouds). Further research is required in these areas. Aviation community assistance is sought through continued reporting of sulfurous odors or other indications of diffuse volcanic cloud encounters, in order to validate the satellite retrievals.  相似文献   

New SHRIMP U-Pb,Sm-Nd,and Rb-Sr data on the campanian age and genesis of gneissic plagiogranites of the Kol and Krutogorova massifs (Sredinnyi Kamchatka Uplift)     

V. K. Kuz’min  E. S. Bogomolov  N. V. Rodionov 《Doklady Earth Sciences》2014,456(1):505-511

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A galaxy halo model of large-scale structure     

Mark C. Neyrinck  rew J. S. Hamilton  Nickolay Y. Gnedin 《Monthly notices of the Royal Astronomical Society》2005,362(1):337-348

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