Radiogeochemical specialization of the Late Jurassic and Cretaceous intrusive complexes of the Kolyma

1.

Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского
Radiogeochemical specialization of the Late Jurassic and
Cretaceous intrusive complexes of the Kolyma.
Autor: Vorobev Iurii V.
Scientific supervisor: PhD Kashkevich Marina P.

2.

The structure of the presentation
Relevance of the research
Purpose of the research
Research methodology
Main results
Conclusion
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского

3.

Relevance of the research
Practical
Fundamental
The depletion of the reserves of the Kolyma placer deposits
made the search for primary gold deposits actual. Intrusive
complexes are key to formation of gold deposits in the region.
Determining the type of complex at the stage of airborne
geophysical work will significantly increase the efficiency
of prospecting work.
The ability to record metasomatic processes by radiogeochemical zoning will make it possible to identify the type
of predicted ore objects.
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского
Establishing a relationship between the composition of
intrusive formations and metasomatic changes with radiogeochemical characteristics.

4.

Purpose of the research
The aim is to establish the radio-geochemical specialization of petrotypes of the
main igneous complexes and to find out the relationship between
the composition of the complexes and the radio-geochemical specialization.
Tasks:
• Create a database of the main igneous complexes of the Kolyma
based on the available geological, geochemical and geophysical information;
• Classify complexes using ARC technology, based on modern airborne gamma-spectrometric data
• Conduct radiogeochemical analyzes of samples taken during the 2019-2020 work.
• Correlate radio geochemical classification and important characteristics of igneous complexes ;
The object of research are the igneous complexes of the Kolyma.
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского

5.

Research methodology
1. Creation of digital models of K, U, Th concentrations according to modern AGS surveys.
2. Isolation of the correlated component using the ARC technology.
3. Determination of specialization within the known contours of intrusive massifs.
4. Establishing correlations with the available characteristics.
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского
Басугуньинский плутонический комплекс диорит-гранодиоритовый
Название массива
Возраст
Состав
Корабль
J3 b 3-6
монцодиориты шестой фазы,
гранодиориты четвертой фазы,
диориты третьей фазы
Рудные формации
золото-кварцевая,
грейзеновая (W)
С-З часть массива (диориты): K
С-В часть массива (монцодиориты): K
Ю часть массива (гранодиориты): U-K
Радиогеохимическая специализация
Чалбыканские
штоки
J3 b 4-5
шток Большой Чалбыкан
сложен гранодиоритами
четвертой фазы, Малый
Чалбыкан – гранитами пятой
фазы, преимущественно
золото-редкометалльная, грейзеновая (W,
Mo, Sn, Bi)
Большой Чалбыкан: Th-U, с областями Th и U
специализации.
Малый Чалбыкан: U-K, U к юго-востоку

6.

Main resalts
Uncorrelated thorium component
Uncorrelated potassium component
Басугуньинский плутонический комплекс диорит-гранодиоритовый
Название массива
Возраст
Состав
Корабль
J3 b 3-6
монцодиориты шестой фазы,
гранодиориты четвертой фазы,
диориты третьей фазы
золото-кварцевая,
грейзеновая (W)
Рудные формации
С-З часть массива (диориты): K
С-В часть массива (монцодиориты): K
Ю часть массива (гранодиориты): U-K
Радиогеохимическая специализация
Чалбыканские
штоки
J3 b 4-5
шток Большой Чалбыкан
сложен гранодиоритами
четвертой фазы, Малый
Чалбыкан – гранитами пятой
фазы, преимущественно
золото-редкометалльная, грейзеновая (W,
Mo, Sn, Bi)
Большой Чалбыкан: Th-U, с областями Th и U
специализации.
Малый Чалбыкан: U-K, U к юго-востоку
Магаданский плутонический комплекс гранит-гранодиоритовый
Название массива
Uncorrelated uranus component
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского
Возраст
Победа
K2 m
Профессорский
K2 m
Состав
граниты пятой фазы,
кварцевые диориты третьей
фазы. (по карте диориты и
гранодиориты)
двуслюдяные граниты 2 фазы,
порфировидные граниты 1
фазы, риолиты 3 фазы
Рудные формации
Радиогеохимическая специализация
золото-кварцевая,
золото-серебряная,
грейзеновая (Bi)
U-K, K, некоторые области K-Th и U.
золото-кварцевая,
грейзеновая (Mo)
ярко выраженная U
Correlation tables

7.

Conclusion
1. From east to west, the contents of U and Th increase over large massifs. Moreover, the nature of radioactivity, including
for the host sedimentary rocks, gradually changes from significantly potassium to significantly uranium. In the case of
sedimentary rocks, this pattern as a whole reflects the change of Permian deposits to Triassic from southwest to
northeast. As for the intrusive massifs, this pattern does not correlate with the belonging of the arrays to different
complexes. Perhaps this is due to a different level erosional cut.
2. A common feature of all large intrusions is the presence of lateral radiogeochemical zoning. Regardless of belonging to a
particular complex along the periphery of the massif, in the endocontact zone, the thorium-potassium nature of
radioactivity, which indicates a partial removal of uranium from here.
3. Younger intrusions of the Neorchansk and Magadan complexes are generally more radioactive than intrusions the rest of
the complexes, which corresponds to the geochemical criteria for the distribution of radioactive elements.
4. Abnormal values ​on Vetrenskaya area are the Professorsky massifs (U content up to 10.5 10-4%) and Western
Butugychag (Th content up to 44 · 10-4%)).
5. Intrusive massifs assigned to the same complexes have different specialization. Siberdyk complex: massifs of Malye
Porogov, Yaryga, Siberdyk-3 and Siberdyk-4, - K, K-Th specialization, Siberdyk-1, Siberdyk-2, Pravo-Obinsky - mostly U
(Th-U); Magadan complex: Victory - K (U-K) specialization, stock Professorial U specialization; Neorchan complex Western Butugychag - Th specialization, Eastern Butugychag - K (K-Th, U-K).
6. Rocks of the same intrusion phase belonging to different massifs can have different specializations. For example, the
Bolshoi Chalbykan stock and the southern block of the Ship massif are composed of granodiorites of the 4th intrusion
phase, however in the radiogeochemical field, the rocks of the first intrusion have Th-U specialization, and the rocks of
the second, U-K. Such differences indicate metasomatic processing of rocks.
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского

8.

Conclusion
7. The heterogeneity of the massifs belonging to the same complex is also emphasized by the difference in useful fossils.
So, for example, in Western Butugychag, rich deposits of U and Sn have been discovered and are being developed, and
the points of Mo mineralization are confined to the East. In addition, in the southern part of Eastern Butugychag there is
an area (about 0.5 - 0.6 km in diameter) with underlined uranium ((6.5-7.5) 10-4%) and thorium ((15–16) · 10-4%)
components, which may also indicate the presence of promising mineralization.
8. According to the theoretical regularities of the distribution of U, Th, and K, with an increase in silicic acidity, contents of
Th and U. Similarly, with increasing alkalinity, but the Th / K bond is more rigid than U / K, therefore an increase in
concentrations is accompanied by an increase in the Th / U ratio. Also, for large multiphase differentiated intrusions of
granitoids are characterized by an increase in the content of U and Th from early phases to later and from inner facies to
marginal facies. For rocks of the Korabl massif, the first condition is fulfilled in the series: diorite ≈ monzodiorite granodiorite, second: diorite - granodiorite ≈ monzodiorite, third: diorite - granodiorite - monzodiorite. For example The
Ship massif shows that an increase in the content of Th and U occurs in the series granodiorite (phase 4) - diorite (phase
3) - monzodiorite (phase 6), an increase in Th / U in the series granodiorite - monzodiorite - diorite. Such inconsistencies
in correlations is associated with the redistribution of matter, which indicates a significant metasomatic processing.
9. High content of uranium (7.72 10-4%) and low for igneous rocks thorium-uranium (1.89) rock ratio Professorial stock can
serve as a direct indication that the rocks of this stock have been subjected to strong metasomatic changes. According to
the PI map, points of mineralization were found on the territory of the stock development Mo and Au. The combination of
these features indicates the possibility of detecting hydrothermal deposits. greisen, gold-quartz formations.
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского

9.

Au revoir et bonne chance.
Всероссийский научно-исследовательский
геологический институт им. А.П. Карпинского