Honoring the master's thesis entitled "Reconstructing the thermal history of metamorphic rocks of the Chupa Belt of the Belomorian Province through U-Pb systematics of accessory minerals", a RAS medal with a prize was awarded to Maria Sukhanova, first-year Doctoral Student at the Institute of Geology KarRC RAS specializing in Petrology and Volcanology (code 1.6.3) and Junior Researcher at the Institute of Precambrian Geology and Geochronology (IPGG) RAS in St. Petersburg.
Maria Sukhanova at work on a field trip
Maria Sukhanova is a graduate of the St. Petersburg State University. In 2025, she completed her Master's degree at the Institute of Earth Sciences of the St. Petersburg State University and entered the Doctoral program at the Karelian Research Centre RAS, where she is studying under the supervision of Doctor of Geological and Mineralogical Sciences Sergey Svetov. In the course of her studies and work at the IPGG RAS, she has become proficient in uranium-lead (U-Pb) isotope research of geochronometer minerals. This term is applied to minerals that help date the rocks within which they are found and link this dating to the formation conditions – temperature, pressure, etc. Maria conducts geochronological research at the Isotope Geology Laboratory of the IPGG RAS, where she works under the guidance of RAS Corresponding Fellow Alexander Kotov and Leading Researcher Ekaterina Salnikova.
Karelian territory is part of the ancient Precambrian Fennoscandian Shield, where rocks up to 3.2 billion years old are exposed on the Earth's surface. Over the billions of years since their formation, the rocks of the Fennoscandian Shield have undergone multiple episodes of high-temperature alteration and tectonic reworking, so deciphering their formation history is a non-trivial task.
The research object – Belomorian Province of the Fennoscandian Shield
The Belomorian Province of the Fennoscandian Shield is one of the most challenging areas to study, which is one of the things that makes it so enticing for researchers. Here, scientists have identified several large-scale episodes of mountain system formation, for which knowing the precise ages of geological processes is crucial. Maria Sukhanova's research is designed to unpack the history of the Belomorian Province – more specifically, two ancient orogens (mountain systems) that existed in the territory: the Belomorian and the Lapland-Kola orogens.
The novelty of Maria Sukhanova's work, started back in her master's studies, is that the evolutionary history of rocks is reconstructed using not one, but a whole suite of geochronometer minerals: zircon, monazite, titanite, and rutile.
Each of these minerals forms under specific conditions, and their isotopic systems "close" at different temperatures, so each contributes its part to unpacking the history, complementing one another. Zircon has the highest closure temperature for the U-Pb isotopic system, at 900–950 °C, while rutile has the lowest, at 380–450 °C, with monazite and titanite occupying intermediate positions. By dating these minerals one can determine the temperature pattern over the evolutionary history of orogens within individual tectonic blocks. For example, in rocks near Ambarny, Louhi District of Karelia, Maria managed to study three minerals at once – rutile, monazite, and zircon. Through their analysis, the age of metamorphic events was established and the thermal history of this segment of the Earth's crust was deciphered.
Flowchart of the thermochronology method
A substantial part of the complex and multi-stage pipeline of determining the age of geological processes is done by the young researcher herself: she finds suitable samples in the field, participates in preparing them for analysis and mineral extraction, selects suitable grains – those within 100 microns (1 micron = 0.001 mm), chooses the protocols for their acid digestion, and performs measurements using a thermal ionization mass spectrometer (TIMS). There are only a few such instruments in Russia, one of them at the IPGG RAS.
The dating process is complicated by the fact that minerals are not always found in nature in their pure form. Geochronometer minerals often become ‘overgrown’ on the outside or contain inclusions of other minerals. If one tries to dissolve them, they get mixed with one another, rendering analysis of this mixture, however precise, useless. Staff of the Isotope Geology Laboratory at the IPGG RAS, with Maria Sukhanova involved, develop methods to address such problems. One example is the "discrete chemical abrasion" technique, which enables chemical separation of baddeleyite and zircon within aggregates and dating of each. Having studied individual monazite grains, Maria has acquired new evidence that the Belomorian Province underwent two stages of metamorphism, during which there formed the Belomorian (2.7 billion years) and the Lapland-Kola (1.9 billion years) orogens. This was the first instance of detecting monazite of two different ages preserved within the same rock. The results of these studies were published in the Doklady Earth Sciences and Petrology journals. The data obtained during these investigations form the basis of Maria's Master's thesis, which was honored with the RAS medal and prize.
A baddeleyite–zircon aggregate under a microscope: a complex case of intergrowth, where the minerals need to be separated before their age can be determined
Maria Sukhanova plans to continue her work on studying the formation time and the metamorphic history of the Lapland-Kola orogen, as well as to investigate how its evolution has affected the surrounding continental blocks.
Currently, Maria and her colleagues are working within a project supported by the Russian Science Foundation (No. 25-27-00675, Principal Investigator Oleg Maksimov), studying the Lapland-Kola orogen – an ancient mountain system that encompassed the ancient Karelian and Murmansk continental blocks (cratons). Maria's main task within the project is to determine the age of metamorphic processes based on the study of a suite of geochronometer minerals using the ID-TIMS method.
We congratulate Maria on being awarded the RAS medal and wish her new discoveries and success in her dissertation work!
Photos and images provided by Maria Sukhanova
