Pure strontium-87 isotope in rubidium biotite from the ukrainian shield
In lithium pegmatites of Shpoljano-Tashlyksky ore area (Kirovograd block of the Ukrainian shield) the biotites enriched with rubidium are distinguished. X-ray and electron-microprobe study of these minerals has shown that they attributed to low ferruginous biotites of structural modification 1M. By...
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| Zitieren: | Pure strontium-87 isotope in rubidium biotite from the ukrainian shield / A.V. Andreev, A.A. Valter, N.P. Dikiy1, A.N. Dovbnya, G.K. Eremenko2,Yu.V. Lyashko, A.I. Pisansky, V.E. Storizhko, V.L. Uvarov // Вопросы атомной науки и техники. — 2011. — № 3. — С. 54-59. — Бібліогр.: 14 назв. — англ. |
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irk-123456789-1112442017-01-10T03:02:16Z Pure strontium-87 isotope in rubidium biotite from the ukrainian shield Andreev, A.V. Valter, A.A. Dikiy, N.P. Dovbnya, A.N. Eremenko, G.K. Lyashko, Yu.V. Pisansky, A.I. Storizhko, V.E. Uvarov, V.L. Ядернo-физические методы и обработка данных In lithium pegmatites of Shpoljano-Tashlyksky ore area (Kirovograd block of the Ukrainian shield) the biotites enriched with rubidium are distinguished. X-ray and electron-microprobe study of these minerals has shown that they attributed to low ferruginous biotites of structural modification 1M. By nuclear-physics methods the concentration of rubidium, ⁸⁷Rb and ⁸⁷Sr were defined. By X-ray-fluorescent method Sr/Rb-ratio was defined. From these data the cleanliness ⁸⁷Sr s%=⁸⁷Sr/Srtot×100=96⁺⁴₋₆% received. The natural isotopic abundance of ⁸⁷Sr is 7%. Rb/Sr age of the mineral is estimated as 2.14 billion years that will be coordinated with earlier results. У літієвих пегматитах Шполяно-Ташлицького рудного району (Кіровоградський блок Українського щита) зустрінуті біотити, збагачені на рубідій. Рентгенографічне і електронно-мікрозондове вивчення цих мінералів доводить, що вони відносяться до низькозалізистих біотитів структурної модифікації 1M. Ядерно-фізичними методами визначені концентрації ⁸⁷Rb і ⁸⁷Sr, рентген-флюоресцентним методом - Sr/Rb - співвідношення. За цими даними отримали чистоту ⁸⁷Sr s%=⁸⁷Sr/Srtot×100=96⁺⁴₋₆% порівняно із звичайною розповсюдженістю ⁸⁷Sr 7%. Rb/Sr вік мінерала оцінений в 2.14 мільярди років, що узгоджується з результатами, що були отримані раніше. В литиевых пегматитах Шполяно-Ташлыкского рудного района (Кировоградский блок Украинского щита) встречены биотиты, обогащённые рубидием. Рентгенографическое и электронно-микрозондовое изучение этих минералов показало, что они относятся к низко железистым биотитам структурной модификации 1M. Ядерно-физическими методами определены концентрации ⁸⁷Rb и ⁸⁷Sr, рентген-флюоресцентным методом - Sr/Rb - отношение. Из этих данных получили чистоту ⁸⁷Sr s%=⁸⁷Sr/Srtot×100=96⁺⁴₋₆% по сравнению с обычной распространённостью ⁸⁷Sr 7%. Rb/Sr возраст минерала оценен в 2.14 миллиарда лет, что согласуется с ранее полученными результатами. 2011 Article Pure strontium-87 isotope in rubidium biotite from the ukrainian shield / A.V. Andreev, A.A. Valter, N.P. Dikiy1, A.N. Dovbnya, G.K. Eremenko2,Yu.V. Lyashko, A.I. Pisansky, V.E. Storizhko, V.L. Uvarov // Вопросы атомной науки и техники. — 2011. — № 3. — С. 54-59. — Бібліогр.: 14 назв. — англ. 1562-6016 PACS: 29.17.+w; 28.41.Kw http://dspace.nbuv.gov.ua/handle/123456789/111244 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Ядернo-физические методы и обработка данных Ядернo-физические методы и обработка данных |
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Ядернo-физические методы и обработка данных Ядернo-физические методы и обработка данных Andreev, A.V. Valter, A.A. Dikiy, N.P. Dovbnya, A.N. Eremenko, G.K. Lyashko, Yu.V. Pisansky, A.I. Storizhko, V.E. Uvarov, V.L. Pure strontium-87 isotope in rubidium biotite from the ukrainian shield Вопросы атомной науки и техники |
| description |
In lithium pegmatites of Shpoljano-Tashlyksky ore area (Kirovograd block of the Ukrainian shield) the biotites enriched with rubidium are distinguished. X-ray and electron-microprobe study of these minerals has shown that they attributed to low ferruginous biotites of structural modification 1M. By nuclear-physics methods the concentration of rubidium, ⁸⁷Rb and ⁸⁷Sr were defined. By X-ray-fluorescent method Sr/Rb-ratio was defined. From these data the cleanliness ⁸⁷Sr s%=⁸⁷Sr/Srtot×100=96⁺⁴₋₆% received. The natural isotopic abundance of ⁸⁷Sr is 7%. Rb/Sr age of the mineral is estimated as 2.14 billion years that will be coordinated with earlier results. |
| format |
Article |
| author |
Andreev, A.V. Valter, A.A. Dikiy, N.P. Dovbnya, A.N. Eremenko, G.K. Lyashko, Yu.V. Pisansky, A.I. Storizhko, V.E. Uvarov, V.L. |
| author_facet |
Andreev, A.V. Valter, A.A. Dikiy, N.P. Dovbnya, A.N. Eremenko, G.K. Lyashko, Yu.V. Pisansky, A.I. Storizhko, V.E. Uvarov, V.L. |
| author_sort |
Andreev, A.V. |
| title |
Pure strontium-87 isotope in rubidium biotite from the ukrainian shield |
| title_short |
Pure strontium-87 isotope in rubidium biotite from the ukrainian shield |
| title_full |
Pure strontium-87 isotope in rubidium biotite from the ukrainian shield |
| title_fullStr |
Pure strontium-87 isotope in rubidium biotite from the ukrainian shield |
| title_full_unstemmed |
Pure strontium-87 isotope in rubidium biotite from the ukrainian shield |
| title_sort |
pure strontium-87 isotope in rubidium biotite from the ukrainian shield |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2011 |
| topic_facet |
Ядернo-физические методы и обработка данных |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/111244 |
| citation_txt |
Pure strontium-87 isotope in rubidium biotite from the ukrainian shield / A.V. Andreev, A.A. Valter, N.P. Dikiy1, A.N. Dovbnya, G.K. Eremenko2,Yu.V. Lyashko, A.I. Pisansky, V.E. Storizhko, V.L. Uvarov // Вопросы атомной науки и техники. — 2011. — № 3. — С. 54-59. — Бібліогр.: 14 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-08T01:50:38Z |
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| fulltext |
PURE STRONTIUM-87 ISOTOPE IN RUBIDIUM BIOTITE
FROM THE UKRAINIAN SHIELD
A.V.Andreev2,3, A.A.Valter2∗, N.P.Dikiy1, A.N.Dovbnya1, G.K.Eremenko2,
Yu.V. Lyashko1, A.I. Pisansky2, V.E. Storizhko2, V.L. Uvarov1
1National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine
2Institute of Applied Physics NAS Ukraine, 40030, Sumy, Ukraine
3T. Shevchenko National University, 03022, Kiev, Ukraine
(Received April 15, 2011)
In lithium pegmatites of Shpoljano-Tashlyksky ore area (Kirovograd block of the Ukrainian shield) the biotites
enriched with rubidium are distinguished. X-ray and electron-microprobe study of these minerals has shown that they
attributed to low ferruginous biotites of structural modification 1M. By nuclear-physics methods the concentration
of rubidium, 87Rb and 87Sr were defined. By X-ray-fluorescent method Sr/Rb–ratio was defined. From these data
the cleanliness 87Sr σ%=87Sr/Srtot×100=96+4
−6% received. The natural isotopic abundance of 87Sr is 7%. Rb/Sr age
of the mineral is estimated as 2.14 billion years that will be coordinated with earlier results.
PACS: 29.17.+w; 28.41.Kw
1. INTRODUCTION
A pure strontium-87 isotope is formed in mineral
by accumulation of the products from a β-decay of
rubidium-87 according to the law [1]:
Crg = Crd
[
exp(
t ln2
T1/2
)− 1
]
, (1)
where Crg is the current content of a radiogenic iso-
tope, Crd is the current content of a radioactive iso-
tope, t is the age of a mineral, T1/2 is the the half-life
period of radioactive isotope.
The accumulation of a pure isotope is promoted
by geochemical and crystal-chemistry factors [2].
Earlier [2,3] we have established the isotope cleanli-
ness of radiogenic 187Os, resulting from a β-decay of
187Re and present to the extent of 99.99% (while its
natural abundance is 1.64%, or 1.96% [4,5]) in ancient
Re-bearing molybdenites from Ukrainian ores. This
fact can be due to rarity of osmium in geochemical
systems, affinity of sedimentation conditions for rhe-
nium and molybdenum from hydrotherms and dura-
bility of retention of radiogenic osmium in a molyb-
denite structure.
87Sr formed as a result of the β-decay of 87Rb has
a half-life of 4.88·1010 years and an isotope abundance
of 7% [4,5].
The strontium sharply enriched with a radi-
ogenic isotope, was first examined by O. Hahn et
al. [6] in pollucite (Karbib, South West Africa).
L.G. Arens and Z. Mattauh observed nearly pure
87Sr in rubidium-containing late Proterozoic lepido-
lites from alkaline pegmatites of Manitoba (Canada).
Recently new varieties of ancient highly rubidic
micas in Canada and on Kola peninsula have been
studied [8,9], however, without reported data on ra-
diogenic strontium.
2. Rb-BIOTITE OF THE UKRAINIAN
SHIELD
We have investigated the ancient Rb-bearing biotite
of the Ukrainian shield as potential mineral carrier of
isotopic pure strontium-87.
In 1889-1990 in the western part of the Kirovograd
block the new Shpoliano-Tashlyksky ore area (Fig.1)
has been discovered. There the rare metal miner-
alization is connected with late Proterozoic gran-
ite pegmatites having lithium specialization [9]. In
the Stankovatsko-Lipnjazhsky pegmatite field in this
area, thin (2...3 cm) streaks of Rb-bearing biotite
glimmerites are widely spread, tracing the contacts
with amphibolites and their replaced xenolites [10].
The biotite contains increased concentrations of
rare alkalis, mainly rubidium. Special studies were
carried out on samples of biotite selected by G.K. Ere-
menko, as well as on those offered through the cour-
tesy of V.N. Bugaenko and D.K. Voznjak.
After additional cleaning by gravitational sepa-
ration and selection under microscope, the samples
were subjected to microprobe analysis and XRD-
study.
∗Corresponding author E-mail address: avalter@iop.kiev.ua
54 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2011, N3.
Series: Nuclear Physics Investigations (55), p.54-59.
Fig.1. Schematic diagram of the geological position of the studied rubidic biotite - the carrier of pure
strontium-87 isotope. 1 Archaean blocks of the Ukrainian shield (in circles): 1 - Podolsk; 2 - Pridneprovsky.
2 Kirovograd Proterozoic block. 3 Dneprovo-Donesk basin. 4 Granitoids of the Kirovograd massive. 5 Ra-
pakivi granites and the basic rocks of the Korsun-Novomirgorod pluton. 6 Shpoljano-Tashlyksky ore area (a
cross indicates the display of Stankovatsky deposit with rubidium-containing biotites). 7 Central-Ukrainian
Uranium ore area. 8 geological borders: (a) blocks borders; (b) other borders
The factors of crystal-chemistry formulas of
biotite samples have been calculated (Tabl.2)
from the quantitative microanalysis data (analyst
V.M. Vereshchak, Camebax SX-50 with a wave spec-
trometer) taking into account earlier chemical analy-
sis [12,13].
Table 1. Crystal chemical formulas of biotite samples investigated
Nu. Nu. of borehole;
depth, m
Crystal chemical formula calculated for Si = 3
4 59-89; 126.0 (Cs0.2Rb0.15K0.44Na0.05)(Fe1.21Mg1.5Al0.59Ti0.07)(AlSi3O10)F0.1OH1.9
5 72-90; 247 (Cs0.02Rb0.07K0.87Na0.06)(Fe0.75Mg1.73Al0.14Ti0.08)(AlSi3O10)F0.95OH1.05
6 3-91; 97.5 (Rb0.04K0.80Na0.05Ca0.01)(Fe0.85Mg1.70Al0.64Ti0.08)(AlSi3O10)F0.17OH1.83
7 33-91; 181.5 (Rb0.05K0.84Na0.02)(Fe0.97Mn0.02Mg1.11Al0.71Ti0.12)(AlSi3O10)F0.26OH1.74
9 34-91; 113.5 (Rb0.05K0.99Na0.02)(Fe1.18Mn0.02Mg1.29Al0.7Ti0.02)(AlSi3O10)F0.25OH1.75
10 34-91; 112-113 (Rb0.05K1.02Na0.01)(Fe1.14Mn0.02Mg1.21Al0.64Ti0.13)(AlSi3O10)F0.26OH1.74
X-ray diffractometer patterns recorded by
E.E. Grechanovskaja (DRON-2, CuKα γ-radiation,
with the speed of the counter rotation of 2◦/min)
(Fig.2) compared with data from [13] allow biotite
to be ascribed to the ferriferous low variety and the
structural modification 1M.
55
Fig.2. X-ray diffraction pattern of biotite samples. On the right: numbers of samples; above: peak indexes
for 1M modification
3. THE INVESTIGATION OF THE
RUBIDIUM-STRONTIUM ISOTOPE
SYSTEM IN BIOTITE
Our goal was to determine the content and cleanliness
of 87Sr in ancient Rb-biotites and to obtain additional
data for their isotope dating.
The natural isotope cleanliness of radiogenic 87Sr
in biotite does not seem to be as high as the 187Os
cleanliness in molybdenite. Strontium has a far
greater natural occurrence, than osmium. Moreover,
the attachment of strontium atoms to the biotite
structure is not so strong as that of osmium in molyb-
denite. In interlayer spaces of the mica structure,
the Sr2+ ion, approaching in size one-charge ions of
alkali metals, can be fixed, creating a certain defect
demanding indemnification of valencies, obviously ac-
cording to the scheme Rb, OH → Sr, O.
This leads to a rather high average content of
strontium in biotites of granitoids (0,012%), basic
rocks (0,01%) and, especially, alkaline rocks (0.1%)
[15], which is approximately by 9 and 10 tenths of the
order greater than the probable initial content of os-
mium in molybdenite. It is not impossible, however,
that reported in [15] average data are considerably
increased at the expense of radiogenic strontium.
Measurements of the concentrations of radioac-
tive (87Rb) and radiogenic (87Sr) nuclides were per-
formed using photoactivation analysis on nuclear re-
actions. The irradiations of biotite samples were car-
ried out with 10 MeV electrons from linear acceler-
ators for 87mSr isomer excitation (T1/2=2.805 hour)
and bremsstrahlung with Emax=23 MeV for determi-
nation of the 87Rb content (T1/2=48.8·109 years).
The activities of 87mSr and 84,86Rb were measured
with a Ge(Li)-detector (∆1/2=3.2 keV for 1333 keV)
and a HP Ge detector (∆1/2=295 eV for 5.9 keV)
using standard Rb compounds as well as SrCO3 with
natural and enriched 87Sr isotope concentrations.
4. DETERMINATION OF 87Rb
The intensity of lines 881.5 keV (85Rb(γ,n)84Rb) and
1077 keV (87Rb(γ,n)86Rb; 85Rb(n,γ)86Rb) were mea-
sured by Ge(Li)-detector (Fig.3) after activation of
the samples and standards.
The results were normalized (measurement time,
time after activation, distance from the sample to the
detector, detector efficiency, sample mass) and aver-
aged for samples (usually 4 measurements on each
sample throughout 80 days after activation) and for
standards. As standards RbCl and Rb2CO3, were
used normalized to the mass of the Rb content.
The ratio of the obtained values determines the
general Rb and 87Rb content in the samples. For a
56
less intensive 1077 keV line the statistics was found
twice as worse on the average and these data were
neglected. The general rubidium was calculated.
Errors in the determination (%) for Rb and 87Rb
were assumed equal, being dependent on the accu-
racy of measurements of the 881.5 keV line intensity.
Fig.3. A fragment of a typical γ-spectrum of biotite
(sample 7, tab.1) activated with a LEA. 37 days
after the activation; exposure for 4 hours
5. DETERMINATION OF 87Sr
Determination of 87Sr was made using the reactions
87Sr(e,e
′
)87mSr and 87Sr(γ,γ
′
)87mSr (2.803 h) → 87Sr
(stab); E=388.5 keV, ni=82.1%.
For 87Sr owing to much lower concentrations, than
in the case of rubidium, poorer statistics of counts
was used. For the most enriched Sr sample (Nu.4)
measurements on 87Sr were performed twice: with
11 MeV γ and 10 MeV electrons. The resulting val-
ues were practically similar indicating an insignificant
error for these concentrations.
6. DETERMINATION OF THE GENERAL
STRONTIUM AND CALCULATION OF
THE ISOTOPE CLEANLINESS OF 87Sr
To determine the general strontium the Rb/Sr-ratios
were measured by X-ray-fluorescence. The deter-
minations were conducted on separate crystals (by
20 grains with the calculated average value) by the
intensity of Kα-lines with the use of an energy-
dispersive X-ray spectrometer and monochromatic
exciting radiation (crystal-monochromator LiF was
adjusted to the Kα-line of a Mo anode of an X-ray
tube).
The results for rubidium and strontium in the in-
vestigated biotite samples are summarized in Tabl.2.
As can be seen from the table, only 3 of 6 detec-
tions give acceptable values: Srtot/
87Sr > 1. These
are the samples most enriched by strontium. For
three other samples this relation is less than unity,
i.e. is not meaningful. It would be reasonable to at-
tribute such grouping of results to a low accuracy of
the determination of 87Sr and Sr/Rb-ratios in low-
strontium samples. Assuming the extreme value for
Srtot/87Sr=100%, we will arrive at the following aver-
age value for 6 samples σ%=87Sr/Srtot×100=96+4
−6%
against the natural 87Sr prevalence of 7%.
Table.2. Determination of Rubidium (mass %) and Strontium (ppm) in biotites
No. Borehole,
depth,m
Chemical
analysis
(recal-
culation
on
oxides)
µ-probe Total Rb
(on the
basis of
87Rb)
Ratio
Sr/Rb
(on the
basis of
X-rays
fluores-
cence)
Total Sr
(on the
basis of
87Rb and
X-rays
fluores-
cence)
87Sr by
accelera-
tor based
technique
87Sr on the
basis of
87Rb (as-
sumption
t=2.1·109
yr. for all
samples)
87Sr/Srtot
from
columns
7/6 and
8/6 (in
brack-
ets)
1 2 3 4 5 6 7 8 9
4 59-89,
126.0
2.23 2.14±0.22 2.6±0.02 0.0093
±0.0013
244 225.5±8.8 226.5 92.4
5 72-90,
247
N/A 1.52±0.06 1.4±0.009 0.0092
±0.0015
130.5 122.8±6.0 122.9 94.1
6 3-91,
97.5
0.80 0.61±0.04 0.82±0.005 0.089
±0.0008
73.1 85.4±3.7 71.1 116.8
(96.2)
7 33-91,
181.5
1.16 0.87±0.01 0.9±0.006 0.0085
±0.0006
74 96.4±3.2 83.1 130.2
(111.4)
9 34-91,
113.5
1.10 0.89±0.02 1.02±0.006 0.0092
±0.0008
94.2 88.7±4.3 88.4 93.8
10 34-91,
112-113
N/A 0.85±0.03 0.79±0.005 0.0084
±0.0007
66.4 85.1±3.7 68.4 128
(100.7)
7. DETERMINATION OF ISOTOPE
87Rb/87Sr AGE IN BIOTITES WERE
STUDIED
On the graph (Fig.4) small circles and square show
the 87Rb–87Sr values for the studied samples. Three
results, referring to the richest rubidium and stron-
tium samples (Nu. 4, 5 and 9, Tabl.1 and 2) give
a straight line (1) 87Sr=0.031·87Rb+1 with a slope
corresponding to the age of 2.14 billion years. This
age correlates with the data [11] indicating a greater
age of pegmatites in comparison with the enclosing
granitoids (1.8-2.0 billion years).
57
Fig.4. 87Sr–87Rb ratios in biotites under study (explanations in the text)
The value of a free member corresponding to
the 87Sr value at the moment of mineral formation
(87Sr0 = 1 ppm) agrees with the data on the isotope
cleanliness of the samples. Assuming as a first ap-
proximation, the same parity of strontium isotopes
in the mineral forming environment of the alkaline
pegmatites at the moment of their crystallization,
as now, we will have the average content of other
strontium isotopes in three investigated samples, viz.
≈ 13 ppm, which, within the accuracy of measure-
ment, agrees with data in tab.2 (≈ 9,7 ppm). Pro-
ceeding from this data, the value of the average iso-
tope cleanliness σ%=87Sr/Srtot×100≈92% is in good
agreement with the average determined for an indi-
vidual sample.
Other three values, corresponding to rubidium-
poorer samples (Nu. 6, 7 and 10) follow a straight line
(2) 87Sr=0.025·87Rb+28 with a slope corresponding
to the age t=1.76 million years. This value of the
effective age is possible as a result of a far-gone gran-
itization process. It is more difficult to explain a high
value of 87Sr0=28 ppm. Under the assumption of a
normal isotope ratio of initial strontium it agrees with
the general content of strontium of 400 ppm, which is
in conflict with the analytical data. The explanation
assuming an abnormal initial isotopic ratio of stron-
tium in rubidic mica, contradicts the establishment
of the Sr/Rb balance 1.76 billion years ago. A con-
sistent explanation of these data can hardly be given.
The description of the positions of all 6 points
by a single dependence leads to a straight line (3)
87Sr=0.028·87Rb+17 for which the value of the free
member is also outside reasonable geological esti-
mates.
We investigated the third possibility, viz. all
6 points follow the same dependence determined by
the position of high-rubidium samples (Nu. 4, 5 and
9, Tabl.1 and 2) assuming for the same maintenance
of rubidium that of 87Sr, corresponding to the age of
2.14 billion years. This brought the 87Sr values closer
to realistic data with the exception of sample Nu.7.
Thus, it seems justified to consider the determi-
nations of strontium and, especially of 87Sr in low-
maintenance Rb and Sr samples (Nu. 6, 7 and 10)
to be insufficiently accurate for geochemical simula-
tions.
8. CONCLUSIONS
1. In ores of Ukraine in the mineral carrier - a
Rb-biotite - isotopic pure 87Sr (96+4
−6%) was found in
concentrations of 225...90 ppm.
2. From nuclear microanalysis data obtained for
the 87Sr/87Rb ratio the age of formation of this bi-
otite was estimated at 2.14·109 years.
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ЧИСТЫЙ ИЗОТОП СТРОНЦИЙ–87 В РУБИДИЕВОМ БИОТИТЕ УКРАИНСКОГО
ЩИТА
А.В Андреев, А.А. Вальтер, Н.П. Дикий, А.Н. Довбня, Г.К. Ерёменко, Ю.В. Ляшко,
A.И. Писанский, В.Е. Сторижко, В.Л. Уваров
В литиевых пегматитах Шполяно-Ташлыкского рудного района (Кировоградский блок Украинского
щита) встречены биотиты, обогащённые рубидием. Рентгенографическое и электронно-микрозондовое
изучение этих минералов показало, что они относятся к низкожелезистым биотитам структур-
ной модификации 1M. Ядерно-физическими методами определены концентрации, 87Rb и 87Sr,
рентген-флюоресцентным методом – Sr/Rb - отношение. Из этих данных получили чистоту 87Sr
σ%=87Sr/Srtot×100=96+4
−6% по сравнению с обычной распространённостью 87Sr 7%. Rb/Sr возраст ми-
нерала оценен в 2.14 миллиарда лет, что согласуется с ранее полученными результатами.
ЧИСТИЙ IЗОТОП СТРОНЦIЙ–87 У РУБIДIЄВОМУ БIОТИТI УКРАЇНСЬКОГО
ЩИТА
А.В. Андрєєв, А.А. Вальтер, М.П. Дикий, А.М. Довбня, Г.К. Єрьоменко, Ю.В.
Ляшко, О.I. Писанський, В.Ю. Сторiжко, В.Л. Уваров
У лiтiєвих пегматитах Шполяно-Ташлицького рудного району (Кiровоградський блок Українського
щита) зустрiнутi бiотити, збагаченi на рубiдiй. Рентгенографiчне i електронно-мiкрозондове вивчення
цих мiнералiв доводить, що вони вiдносяться до низькозалiзистих бiотитiв структурної модифiкацiї 1M.
Ядерно-фiзичними методами визначенi концентрацiї 87Rb i 87Sr, рентген-флюоресцентним методом –
Sr/Rb - спiввiдношення. За цими даними отримали чистоту 87Sr σ%=87Sr/Srtot×100=96+4
−6% порiвня-
но iз звичайною розповсюдженiстю 87Sr 7%. Rb/Sr вiк мiнерала оцiнений в 2.14 мiльярди рокiв, що
узгоджується з результатами, що були отриманi ранiше.
59
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