Rare gas isotopes and parent trace elements in ultrabasic-alkaline-carbonatite complexes, Kola Peninsula: identification of lower mantle plume component   总被引：2，自引：0，他引：2  

I.N. Tolstikhin  I.L. KamenskyB. Marty  V.A. NivinV.R. Vetrin  E.G. BalaganskayaS.V. Ikorsky  M.A. GannibalD. Weiss  A. VerhulstD. Demaiffe 《Geochimica et cosmochimica acta》2002,66(5):881-901

During the Devonian magmatism (370 Ma ago) ∼20 ultrabasic-alkaline-carbonatite complexes (UACC) were formed in the Kola Peninsula (north-east of the Baltic Shield). In order to understand mantle and crust sources and processes having set these complexes, rare gases were studied in ∼300 rocks and mineral separates from 9 UACC, and concentrations of parent Li, K, U, and Th were measured in ∼70 samples. ⁴He/³He ratios in He released by fusion vary from pure radiogenic values ∼10⁸ down to 6 × 10⁴. The cosmogenic and extraterrestrial sources as well as the radiogenic production are unable to account for the extremely high abundances of ³He, up to 4 × 10⁻⁹ cc/g, indicating a mantle-derived fluid in the Kola rocks. In some samples helium extracted by crushing shows quite low ⁴He/³He = 3 × 10⁴, well below the mean ratio in mid ocean ridge basalts (MORB), (8.9 ± 1.0) × 10⁴, indicating the contribution of ³He-rich plume component. Magnetites are principal carriers of this component. Trapped ³He is extracted from these minerals at high temperatures 1100°C to 1600°C which may correspond to decrepitation or annealing primary fluid inclusions, whereas radiogenic ⁴He is manly released at a temperature range of 500°C to 1200°C, probably corresponding to activation of ⁴He sites degraded by U, Th decay.Similar ⁴He/³He ratios were observed in Oligocene flood basalts from the Ethiopian plume. According to a paleo-plate-tectonic reconstruction, 450 Ma ago the Baltica (including the Kola Peninsula) continent drifted not far from the present-day site of that plume. It appears that both magmatic provinces could relate to one and the same deep-seated mantle source.The neon isotopic compositions confirm the occurrence of a plume component since, within a conventional ²⁰Ne/²²Ne versus ²¹Ne/²²Ne diagram, the regression line for Kola samples is indistinguishable from those typical of plumes, such as Loihi (Hawaii). ²⁰Ne/²²Ne ratios (up to 12.1) correlate well with ⁴⁰Ar/³⁶Ar ones, allowing to infer a source ⁴⁰Ar/³⁶Ar ratio of about 4000 for the mantle end-member, which is 10 times lower than that of the MORB source end-member. In (³He/²²Ne)_PRIM versus (⁴He/²¹Ne)_RAD plot the Kola samples are within array established for plume and MORB samples; almost constant production ratio of (⁴He/²¹Ne)_RAD ≅ 2 × 10⁷ is translated via this array into (³He/²²Ne)_PRIM ∼ 10. The latter value approaches the solar ratio implying the non-fractionated solar-like rare gas pattern in a plume source.The Kola UACC show systematic variations in the respective contributions of in situ-produced radiogenic isotopes and mantle-derived isotopes. Since these complexes were essentially plutonic, we propose that the depth of emplacement exerted a primary control on the retention of both trapped and radiogenic species, which is consistent with geological observations. The available data allow to infer the following sequence of processes for the emplacement and evolution of Kola Devonian UACC: 1) Ascent of the plume from the lower mantle to the subcontinental lithosphere; the plume triggered mantle metasomatism not later than ∼700 to 400 Ma ago. 2) Metasomatism of the lithosphere (beneath the central part of the Kola Peninsula), including enrichment in volatile (e.g., He, Ne) and in incompatible (e.g., U, Th) elements. 3) Multistage intrusions of parental melts, their degassing, and crystallisation differentiation ∼370 Ma ago. 4) Postcrystallisation migration of fluids, including loss of radiogenic and of trapped helium. Based on model compositions of the principle terrestrial reservoirs we estimate the contributions (by mass) of the plume material, the upper mantle material, and the atmosphere (air-saturated groundwater), into the source of parent melt at ∼2%, 97.95%, and ∼0.05%, respectively.  相似文献   

Accretion and early degassing of the Earth: Constraints from Pu-U-I-Xe Isotopic systematics     

I. Ya. Azbel  I. N. Tolstikhin 《Meteoritics & planetary science》1993,28(5):609-621

Abstract— A review of problems related to Xe isotopic abundances in meteorites and terrestrial materials leads to four postulates which should be taken into account to build a model of the Earth's accretion and early evolution. 1. The pre-planetary accretion time scale was shorter than the ¹²⁹I half-life, 17 Ma, so the initial ratio of ¹²⁹I/¹²⁷I had not been decreased considerably when planetary accretion started; therefore, this must also be the case for the ²⁴⁴Pu abundance. 2. The initial relative abundance of involatile refractory ²⁴⁴Pu in proto-planetary materials should be the same as in chondrites, that is, ²⁴⁴Pu/²³⁸U = 0.0068; this value corresponds to initial ²⁴⁴Pu 0.30 ppb in the bulk silicate earth. In contrast, I is a highly volatile element; its initial abundance, accretion history and even the present-day mean concentrations in principal terrestrial reservoirs are poorly known. 3. There is much less fission Xe in the upper mantle, crust, and atmosphere than is predictable from the fission of ²⁴⁴Pu (Xe(Pu)) based on the above argument. Therefore, Xe(Pu) has been mainly released from these reservoirs. 4. A mechanism for Xe(Pu) escape from the complementary upper mantle-crust-atmosphere reservoirs, for example, atmospheric escape via collisions of a growing Earth with large embryos and/or hydrodynamic hydrogen flux, etc., operated during the Earth's accretion. These postulates have been used as a background for a balance model of homogeneous Earth accretion which envisages: growth of the Earth due to accumulation of planetesimals; fractionation inside the Earth and segregation of the core; degassing via collision and fractionation; and escape of volatiles from the atmosphere. During the post-accretion terrestrial history, the processes described by the model are continuous fractionation, degassing and recycling of the upper mantle and crust. The lower mantle is considered as an isolated reservoir. Depending on the scenario invoked, the accretion time scale varies within the limits of 50–200 Ma. In the light of recent experimental data, the latter value is inferred to the most realistic version which explains a high Xe(U)/Xe(Pu) ratio in the upper mantle. Contrary to previous suggestions, the ¹²⁹I-¹²⁹Xe subsystem is considered to be meaningless with regard to the terrestrial accretion time scale. The terrestrial inventory of ¹²⁹Xe(I) is controlled by the initial abundance of volatile elements (including I and Xe) in proto-terrestrial materials and the subsequent degassing history of the Earth. The residence time of a volatile element (e.g., Xe) in the bulk mantle (bm) during accretion, < t (Xe)_bm>, is approximated by the ratio of < t (Xe)_bm> m _bm(t)/φ_{bm, mf} ≤ 10 Ma, where m _bm(t) is the mantle mass, and φ_{bm, mf} is the rate of metal/silicate fractionation, which provided segregation of the core; φ_{bm, mf} is determined by involatile siderophile element abundances in the upper mantle. This relationship implies a link between the abundance of involatile siderophile and volatile incompatible elements. A short <t(Xe)_bm> reflects a high degassing rate due to extremely high φ_{bm, mf} 10²⁰ g/year. A small ratio of the atmospheric amount of Xe over the total amount of this gas in prototerrestrial materials, ≤0.01, is in accord with the process of Xe escape and fractionation in the primary Earth atmosphere.  相似文献   

Helium isotopes in the earth's interior and in the atmosphere: A degassing model of the earth     

I.N. Tolstikhin 《Earth and Planetary Science Letters》1975,26(1):88-96

A first-order degassing model was applied to describe the evolution of helium content and isotope composition in the earth and in the atmosphere. The main events described by the model are: (1) the earth-trapped primordial rare gases at the moment of its accretion; (2) later, the solid earth lost primordial and radiogenic rare gases, and (3) they were accumulated in the atmosphere; (4) in addition,³He was formed in the atmosphere due to cosmic irradiation, accretion from solar wind, etc.; (5)³He and⁴He dissipated into space at different loss rates.Study of this model confirms the concept that some of primordial helium is retained in the interior of the earth; terrestrial helium (³He/⁴He～ 2 × 10^?5) was most probably formed as a mixture of primordial (³He/⁴He= 3 × 10^?4) and radiogenic (³He/⁴He～ 3 × 10^?8) helium. For achondritic concentrations of heavy radioactive elements (U= 2.25 × 10^?8g/g) the calculated⁴He flux from the earth is equal to 5.7 × 10⁶ at cm^?2 sec^?1. The corresponding³He flux is about 114 at cm^?2 sec^?1. In discussing the aeronomic problem of helium it is necessary to take into account that the earth is the main source of the light helium isotope.  相似文献   

Mobility of Radiogenic Isotopes 4Не and 3Не and Their Retention in a Mineral (by the Example of Amphibole)     

Gudkov  A. V.  Kolobov  V. V.  Tarakanov  S. S.  Tolstikhin  I. N. 《Doklady Earth Sciences》2019,488(2):1193-1195

Doklady Earth Sciences -  相似文献   

Origin,Occurrence, and Mobility of He and Ar Isotopes in Meliphanite     

Lyalina  L. M.  Kamensky  I. L.  Tolstikhin  I. D. 《Doklady Earth Sciences》2019,488(1):1120-1122

Doklady Earth Sciences - The U, Th, and 4He contents of meliphanite correspond to an age of metamorphism (1800 Ma) indicating good preservation of radiogenic 4He in mineral but contradicting the...  相似文献   

Isotope composition of helium in ultrabasic xenoliths from volcanic rocks of Kamchatka     

I.N. Tolstikhin  B.A. Mamyrin  L.B. Khabarin  E.N. Erlikh 《Earth and Planetary Science Letters》1974,22(1):75-84

The purpose of this work is to refine our knowledge about the nature of helium with a high abundance of the rare isotope³He(³He/⁴He= 10^?5) discovered in terrestrial volcanic gases in 1968.We will discuss here the results of isotope analyses of helium released by step-wise heating of ultrabasic xenoliths and some volcanic rocks. On the basis of these results, possible sources of³He in the earth due to fission and nuclear reactions are considered critically. The most probable source of the high abundance of³He is shown to be due to the capture and trapping of primordial He by the earth during its formation (primordial helium³He/⁴He= 3 × 10^?4), a small but significant fraction of which has been retained to the present time.  相似文献   

The Formation and Balance of the Atmospheric Precipitations,Surface Water,and Groundwater on the Southern Slopes of the Khibiny Massif (Based on Data on the Isotopic Composition of Oxygen and Hydrogen)     

Gudkov  A. V.  Tokarev  I. V.  Tolstikhin  I. N. 《Water Resources》2021,48(1):124-132

Water Resources - The δ2H and δ18O values of the atmospheric precipitations in the Khibins vary within the range –147 ≤ δ2H ≤ –37‰, –20 ≤...  相似文献   

Evidence of submarine hydrothermal discharge to the northwest of Guadeloupe Island (Lesser Antilles island arc)     

B.G. Polyak  Ph. Bouysse  V.I. Kononov  G.Yu. Butuzova  A. Criaud  V.I. Dvorov  M.D. Khutorskoy  V.G. Matveev  V.I. Paduchikh  E.P. Radionova  A.A. Rot  I.N. Tolstikhin  A.I. Voznesenskiy  V.P. Zverev 《Journal of Volcanology and Geothermal Research》1992,54(1-2)

During the Soviet-French survey carried out on board of the R.V. Akademik N. Strakhov, between Guadeloupe and Montserrat island in the central Lesser Antilles, evidence of submarine hydrothermal activity was discovered on the southeastern tip of the Shoe-Rock escarpment. The latter is part of a large, 130 km long, transverse structure, the Montserrat-Marie Galante fault, which crosses the Guadeloupe archipelago. Another locus of activity, probably of subdued importance nowadays, is represented by the d'Entrecasteaux dome, a small faulted seamount, located about 25 km to the SW of the former area.The evidence for hydrothermal activity is: (a) a wide range of values of conductive heat flow (q=6–11 mW/m²) and regular vertical variation at some sites with extreme values located close to the two above-mentioned features (average regional value, q = 105 mW/m², s.d. = 32); (b) occurrence of secondary mineralizations (todorokite, nontronite, etc.) replacing locally the primary matrix of basal upper Pliocene deposits; (c) geochemical anomalies in seawater near the sea bottom, showing enrichment in mantle-derived ³He (δ³He up to 10.2%), correlated with a sharp Zn anomaly (content up to 523 ppb).Further investigations along the submerged segments of the Montserrat-Marie Galante fault should probably lead to other discoveries of hydrothermal venting and/or mineralizations.  相似文献   

Sites and Origin of Noble Gases in Minerals: A Case Study of Amphibole from Alkaline Granitoids of the Kola Peninsula     

M. A. Gannibal  I. N. Tolstikhin  A. B. Verchovsky  V. I. Skiba  V. R. Vetrin  A. V. Gudkov 《Geochemistry International》2018,56(11):1084-1092

  相似文献   

The tritium-helium-3 method and its application to groundwater dating by the example of the Kirovsk mine region,Murmansk oblast     

A. V. Gudkov  I. L. Kamensky  G. S. Melikhova  V. I. Skiba  I. V. Tokarev  I. N. Tolstikhin 《Geochemistry International》2014,52(7):587-594

The measurement of ³H, ³He, ⁴He, and ²⁰Ne concentrations in waters at the Tsentralny pumping station (southern Khibiny massif, Kola Peninsula) showed that they are a mixture of young (>90%) and old (<10%) waters. The excess noble gas component from the young water is caused by the dissolution of air bubbles trapped during recharge in the unsaturated zone. The ³H-³He(³H) age of the young water is 21 ± 1.5 yr. The U-Th-4He age of the old water is about 50 ka. The high concentrations of helium and some toxic elements (e.g., aluminum) in this old water are caused by dissolution of the alkaline rocks of the Khibiny massif as a result of water-rock interaction.  相似文献