Scattering and dissipation of seismic waves in the presence of nonlinearity     

A. V. Nikolaev 《Pure and Applied Geophysics》1989,131(4):687-702

The processes of seismic wave scattering and dissipation are examined in a medium that, in addition to being inhomogeneous and anelastic, is nonlinear and seismically active (seismic emission). In such a medium, there is a complex interrelation between the effects of nonlinearity, scattering and dissipation. Thus, nonlinear interactions between the various components (primary, scattered and induced) of a developing wavefield cause nonlinear (or wave-on-wave) scattering and, by transferring part of the wave energy to the high-frequency region, contribute to its scattering and dissipation. On the other hand, whereas dissipation opposes the accumulation of nonlinear effects by reducing the wave amplitudes, scattering assists it by increasing the propagation distance (and hence the interaction time).Estimates based on results of field experiments involving vibrators indicate that, as a rule, scattering on inhomogeneities is much stronger than nonlinear scattering, and that nonlinear effects may often dominate dissipative ones.The nonlinearity of the transmitting medium explains observedQ-value anomalies, and its seismic activity explains the existence ofP coda and the temporal changes in codaQ.  相似文献   

Test of the Ballhaus–Berry–Green <Emphasis Type="Italic">Ol–Opx–Sp</Emphasis> oxybarometer and calibration of a new equation for estimating the redox state of melts saturated with olivine and spinel     

G. S. Nikolaev  A. A. Ariskin  G. S. Barmina  M. A. Nazarov  R. R. Almeev 《Geochemistry International》2016,54(4):301-320

Testing the Ballhaus–Berry–Green Ol–Opx–Sp oxybarometer (BBG) on independent experimental data indicates that it overestimates the oxygen fugacity by 0.6–1.3 log units under mildly reduced conditions (near the C–CO buffer) and by as much as 2–3 log units under reduced conditions (at the IW buffer and below it). A newly developed oxibarometer is suggested to minimize this effect and enhance the capabilities of redoxometry of low-pressure mineral associations, including magmatic melts undersaturated with respect to orthopyroxene (Opx). The new empirical equation of the oxybarometer is applicable to a wide range of mafic–ultramafic magmas of normal alkalinity, including terrestrial, lunar, and meteoritic systems under pressures of 0.001–25 kbar and oxygen fugacity ranging from IW–3 to NNO + 1. The derived regression fits the ΔQFM values of the calibration dataset (154 experiments) accurate to ~0.5 log units. The new oxybarometer eliminates systematic errors when redox parameters are evaluated for the reduced region (from IW–3 to C–CO) and for crystallization of magmas without Opx on the liquidus. The efficiency of the suggested model is demonstrated by its application to natural rocks: (1) low-Ti lunar basalts, (2) tholeiites from the Shatsky Rise, (3) Siberian flood basalts, (4) rocks of the layered series of the Yoko-Dovyren intrusion, and (5) mantle xenoliths collected in southern Siberia, Mongolia, China, and the southern Russian Far East. The values yielded by such oxybarometers for intrusive rocks, which underwent long-lasting cooling and postcumulus reequilibration, should be regarded with reserve.  相似文献   

New Data on the Genetic Linkage of the Beryl and Chrysoberyl Chromophores of the Ural’s Emerald Mines with Chromium-Bearing Spinels of the Bazhenov Ophiolite Complex     

Popov  M. P.  Sorokina  E. S.  Kononkova  N. N.  Nikolaev  A. G.  Karampelas  S. 《Doklady Earth Sciences》2019,486(2):630-633

Doklady Earth Sciences - The distribution of chromophores and the composition of chromium-bearing spinels in Uralian emeralds and alexandrites were studied for the first time. It was prooved the...  相似文献   

Hydrothermal Synthesis of Framed Titanosilicates of the Ivanyukite Mineral Structure     

Gerasimova  L. G.  Nikolaev  A. I.  Shchukina  E. S.  Maslova  M. V. 《Doklady Earth Sciences》2019,487(1):831-834

Doklady Earth Sciences - Phase formation within the Na2O–TiO2–SiO2–H2SO4–H2O system under hydrothermal treatment was studied in view of the development of new types of...  相似文献   

The paleoproterozoic Kandalaksha Anorthosite Massif: New U–Pb (ID–TIMS) data and geochemical features of zircon     

E. N. Steshenko  A. I. Nikolaev  T. B. Bayanova  S. V. Drogobuzhskaya  V. V. Chashchin  P. A. Serov  L. M. Lyalina  A. I. Novikov 《Doklady Earth Sciences》2017,477(2):1454-1457

New U–Pb and Sm–Nd isotope data have been obtained in the Kandalaksha–Kolvitsa zone, Baltic Shield, on accessory zircon and rutile, along with whole-rock and secondary metamorphic minerals. Isotope U–Pb age of single zircon grains from metagabbro of the Kandalaksha Anorthosite Massif is 2453.5 ± 4.8 Ma, which is close to the U–Pb age of zircon from the Kolvitsa Massif metagabbro (2448 ± 5 Ma). For the first time, REEs in zircon grains of the Kandalaksha metagabbro have been analyzed and the results have been plotted. Ti-in-zircon thermometry has been applied using LA–ICP–MS: it yielded an average temperature of zircon crystallization of 844°C. The isotope and geochemical new data obtained indicate a magmatic genesis of the zircon crystals studied.  相似文献   

Post-collisional magmatism of western Chukotka and Early Cretaceous tectonic rearrangement in northeastern Asia     

P. L. Tikhomirov  V. Yu. Prokof’ev  I. A. Kal’ko  A. V. Apletalin  Yu. N. Nikolaev  K. Kobayashi  E. Nakamura 《Geotectonics》2017,51(2):131-151

The paper presents new data on the isotopic age and chemical composition of volcanic rocks from the Tytyl’veem and Mangazeika basins of western Chukotka superposed on Mesozoides of the Verkhoyansk–Chukotka Tectonic Region. The results of SIMS U–Pb zircon dating (121.4 ± 2.8 and 118.0 ± 2.0 Ma) corroborate the Aptian age of the Tytyl’veem Formation. This age, in turn, indicates its formation after closure of the South Anyui ocean (Neocomian), but before origination of the Okhotsk–Chukotka Belt (Albian–Campanian). Post-collisional Aptian igneous rocks are widespread in the northern Verkhoyansk–Chukotka Tectonic Region; the legth of the corresponding igneous province is no less than 1400 km. In geochemical characteristics, the post-collisional volcanic rocks occurring in Western Chukotka are similar with the rocks from Andean-type igneous belts.  相似文献   

The crystallization temperature of vein quartz estimated from the concentration of the titanium paramagnetic center in quartz: A case study of the Peschanka porphyry copper–molybdenum–gold deposit,Western Chukchi Peninsula,Russia     

A. D. Prudnikova  D. G. Koshchug  S. V. Vyatkin  I. A. Baksheev  E. V. Nagornaya  L. I. Marushchenko  Yu. N. Nikolaev  A. F. Chitalin 《Moscow University Geology Bulletin》2017,72(2):106-114

The concentration of the Al and Ti paramagnetic impurity centers in pre-ore and ore-stage quartz at the Peschanka porphyry copper–molybdenum–gold deposit in the Western Chukchi Peninsula, Russia were determined using electron paramagnetic resonance spectroscopy (EPR). The [AlO ₄ ^- /h⁺]⁰ concentration in pre-ore and ore-stage quartz varies from 29 to 124 and from 13 to 101 at. ppm, respectively. The contents of the [TiO ₄ ^- /Li⁺]⁰ and [TiO ₄ ^- /H⁺]⁰ centers reach 20 and 6.3 at. ppm, respectively. Pre-ore quartz associated with the formation of biotite–potassium feldspar–quartz alteration and ore-stage quartz associated with the formation of quartz–sericite rocks followed by the ore deposition differ considerably in the Ti center content, especially the [TiO ₄ ^- /H⁺]⁰ center. The [TiO ₄ ^- /H⁺]⁰ concentration is much higher in the pre-ore quartz (>2 at. ppm) than that in the ore-stage quartz related to copper mineralization (<2 at. ppm). The [TiO ₄ ^- /Li⁺]⁰ concentration also decreases from pre-ore to ore-stage quartz. Taking the data we obtained into account, the formation temperature of pre-ore and ore-stage quartz estimated from a titaniumin-quartz geothermometer is 590–470°C (weighted average 520°C) and 510–310°C (weighted average 430°C), respectively. The obtained temperature range of 590 to 310°C is similar to that determined from homogenization of fluid inclusions in quartz.  相似文献   

Gold-telluride mineralization of the Western Chukchi Peninsula, Russia: Mineralogy, geochemistry, and formation conditions     

Yu. N. Nikolaev  V. Yu. Prokof’ev  A. V. Apletalin  E. A. Vlasov  I. A. Baksheev  I. A. Kal’ko  Ya. S. Komarova 《Geology of Ore Deposits》2013,55(2):96-124

Mineralogy, geochemistry, and formation conditions of the Sentyabr’sky prospect—the first economic occurrence of Au-Te mineralization in the Chukchi Peninsula—was studied. Gold occurs in native form and as telluride compound (petzite). Petzite and hessite are the major ore minerals of the gold-telluride assemblage; native gold is superimposed on them. Altaite, coloradoite, and paratellurite have been also identified. The study of fluid inclusions in sphalerite and quartz associated with ore minerals shows that the Au-Te mineralization of the Sentyabr’sky prospect and the low-sulfide Au-Ag ore of the adjacent Dvoinoi deposit were formed from different fluids and under different conditions. The multistage hydrothermal process developed in the frames of long-living porphyry-epithermal system functioned in the Ilirnei district. The Au-Te mineralization at the Sentyabr’sky prospect is related to alkaline magmatism. The high-salinity (above 5 wt % NaCl equiv) fluid inclusions in hydrothermal quartz can be indicators of such mineralization. Mineralogy and geochemistry of ore at the Sentyabr’sky prospect provide evidence for its deposition at the middle level of porphyry-epithermal system and testify to prospectivity of deep levels.  相似文献   

SPINMELT-2.0: Simulation of spinel–melt equilibrium in basaltic systems under pressures up to 15 kbar: I. model formulation,calibration, and tests     

G. S. Nikolaev  A. A. Ariskin  G. S. Barmina 《Geochemistry International》2018,56(1):24-45

The paper presents results of testing currently used models proposed to describe Cr-spinel–melt equilibrium: models of the MELTS family by M.S. Ghiorso with colleagues, the SPINMELT program by A.A. Ariskin and G.S. Nikolaev, and the “MELT–CHROMITE spinel calculator” by А.А. Pustovetov and R.L. Roeder. The new calibration of the SPINMELT model presented in this publication enables calculating a sixcomponent (Mg, Fe²⁺, Cr, Al, Fe³⁺, and Ti) composition of Cr-spinel and the \(T - {f_{{o_2}}}\) parameters of its stability on the liquidus of basaltic melts under pressures up to 15 kbar. The model is based on results of 392 runs from 43 experimental studies, including systems of normal alkalinity at \({f_{{o_2}}}\) ≤ QFM + 2. The experimental dataset (which was extended compared to that used for the previous calibration) allowed us not only to estimate the pressure effect, but also apply the model to aluminous and hydrous systems. Tests of the SPINMELT-2.0 model show that the errors of the calculated temperature of the spinel–melt equilibrium increase with pressure from 16°C at 1 atm to 50°C at 15 kbar. Experimental spinel compositions are reproduced by the model accurate to < 3 at % Al and Cr, and no worse 1 at % for the other cations.  相似文献   

Features of Ore Mineralization of Alyarmaut Rise (Western Chukotka)     

V. Yu. Prokofiev  I. A. Kalko  A. V. Volkov  Yu. N. Nikolaev  N. N. Krivitskaya  A. A. Sidorov 《Doklady Earth Sciences》2018,479(1):310-315

The Au mineralization of Alyarmaut Rise was formed from the ore-forming fluids of two types strongly differing in pressure. The first type of fluid is similar to fluids of the orogenic Au–quartz deposits in terms of the physicochemical parameters and composition. These fluids were formed at a high pressure from heterogeneous, carbon dioxide–aqueous fluids with a low salinity at a depth of 5–7 km. The second type of fluid, which is also heterogeneous, has a shallower origin with a wide range of salinity variation and a small amount of carbon dioxide. This type of fluid is similar to the fluids of epithermal deposits. The wide range of pressure variation characterizing the mineralization of the rise indicates the vertical displacement of the block of the host rocks followed by erosion. Judging by the presence the secondary halos of Au, Ag, As, Sb, Pb, Zn, and Cu in the Upper Paleozoic carbonate–terrigenous rocks of the Alyarmaut Rise, there are prospects to reveal sites with new epithermal Au–Ag mineralization, which are essential for the area and unusual for the Anyui-Chukotka Fold System.  相似文献