Süsiniku isotoopkoostis ja haruldaste muldmetallide kasutatavus paleokeskonna indikaatoritena Paleoproterosoikumi setetes pärast Lomagundi-Jatuli Isotoopsündmust

Väitekirja elektrooniline versioon ei sisalda publikatsiooneVaba hapniku ilmumine atmosfääri ~2,4 miljardit aastat tagasi tõi endaga kaasa põhimõttelised muudatused atmosfäär-ookean süsteemis ning (bio)-geokeemilistes aineringetes. Hapniku kontsentratsiooni kasvuga käis kaasas teadaolevalt suurim häiring Maa süsinikuringes (Lomagundi-Jatuli Isotoopsündmus – LJE), mille jooksul moodustusid ebaharilikult raske süsiniku isotoopkoostisega merelised karbonaadid. Täna enimlevinud arusaama järgi langes O2 sisaldus pärast LJE lõppu, 2,06 miljardit aastat tagasi 0,1% tänapäevasest tasemest, mis kasvas uuesti alles Neoproterosoikumi lõpus. Antud doktoritöös uuriti kahte LJE-järgset läbilõiget Loode Venemaal – 1,98 Ga vanuselist Zaonega kihistut ning 1,92 Ga vanuselist Pilgujärvi settekivimite kihistut. Neid läbilõikeid on varasemalt kasutatud globaalsete keskkonnatingimuste kirjeldamiseks pärast LJE-d, kuid saadud tulemused on jõudnud vasturääkivate järeldusteni. Doktoritöös uuriti nendes kihistustes esineva karbonaatide ja apatiitide petrograafiat, mineraloogiat, süsiniku isotoopkoostist ning haruldaste muldmetallide käitumist. Doktoritööst järeldub, et Zaonega kihistus esinev negatiivne süsinikuisotoopide ekskursioon on ennekõike seotud settebasseinile iseäralike protsessidega (nt metaani oksüdeerimisel moodustunud kerge süsiniku isotoopkoostisega karbonaadid), mida ei saa kasutada avaookeani kirjeldamiseks. Lisaks näitas haruldaste muldmetallide käitumine, ennekõike redoksensitiivse Ce, et Zaonega ja Pilgujärvi settekivimite kihistu moodustumisel pidi atmosfäär-ookean süsteemis olema piisavalt vaba hapnikku, et Ce(III) oksüdeeritaks Ce(IV), põhjustades nii teiste haruldaste muldmetallidega võrreldes Ce vaesustunud geokeemilise signaali (negatiivse Ce-anomaalia). See seab kahtluse alla globaalse hapnikutaseme languse pärast Lomagundi-Jatuli Isotoopsündmust ning viitab kõrgenenud hapnikutaseme püsimisele.The first appearance of free atmospheric oxygen ~2.4 billion years ago brought about fundamental changes in the atmospheric-ocean system and biogeochemical elemental cycles. The increase in oxygen concentration was accompanied by the largest perturbation in global carbon cycle called the Lomagundi-Jatuli Event (LJE), during which marine carbonates of anomalously enriched in heavy carbon isotope were precipitated. According to the most widely held notion, the O2 levels dropped to no more than 0.1% from present atmospheric levels after the termination of LJE 2.06 billion years ago and only increased again at the end of the Neoproterozoic. This thesis focuses on two post-LJE successions in north-western Russia – the 1.98 Ga Zaonega Formation and the 1.92 Ga Pilgujärvi Sedimentary Formation. These successions have previously been used to describe the global post-LJE environmental conditions, however, with contradicting results. This thesis characterises the petrography, mineralogy, carbon isotope composition and behaviour of rare earth elements of carbonates and apatites in these Formations. The thesis concludes that the negative carbon isotope excursion in the Zaonega Formation is primarily due to basin-specific processes (e.g., carbonates enriched in light carbon isotope were influenced by methane oxidation) that cannot be directly used to describe the global ocean. In addition, the behaviour of rare earth elements, particularly redox-sensitive Ce, showed that during the formation of the post-LJE Zaonega and Pilgujärvi sedimentary rocks, sufficient oxygen concentration was required in the atmosphere-ocean system in order to decouple Ce from other rare earth elements (negative Ce-anomaly). This calls into question the global decline in oxygen levels following the Lomagundi-Jatul Isotope Event and suggests prolonged elevated oxygen levels at the time.https://www.ester.ee/record=b528141

Saaremaa õpilaste hinnangud autentsete materjalide kasutamisele põhikooli 7.–9. klasside inglise keele tundides

http://tartu.ester.ee/record=b2693902~S1*es

Euroopa Liidu energiajulgeoleku ja ühise energiaturu teemaline inglise-eesti valiksõnastik

Antud magistritöö eesmärk oli koostada energiajulgeolekut ja ühist energiaturgu käsitlev inglise-eesti valiksõnastik, seda just Euroopa Liidu kontekstis. Peamisteks terminite allikateks olid kolm Euroopa Liidu ametlikku dokumenti, mis mainitud teemat käsitlevad: „Euroopa energiajulgeoleku strateegia 2014“, „Energia 2020: Säästva, konkurentsivõimelise ja kindla energia strateegia“ ja „Energiavarustuse kindluse parandamine energia siseturu arendamise kaudu: tuleb teha täiendavaid jõupingutusi“

Löögimoonde mineraloogilised indikaatorid Sääksjärvi ja Lappajärvi impaktkivimeis

http://tartu.ester.ee/record=b2655101~S1*es

Petrography and the REE-composition of apatite in the Paleoproterozoic Pilgujärvi Sedimentary Formation, Pechenga Greenstone Belt, Russia

The first globally significant phosphorous-rich deposits appear in the Paleoproterozoic at around 2 Ga, however, the specific triggers leading to apatite precipitation are debated. We examine phosphorous-rich rocks (up to 8 wt% P2O5) in 1.98–1.92 Ga old Pilgujärvi Sedimentary Formation, Pechenga Greenstone Belt, Russia. Phosphates in these rocks occur as locally derived and resedimented sand-to-gravel/pebble sized grains consisting of apatite-cemented muddy sediments. Phosphatic grains can be subdivided into four petrographic types (A–D), each has a distinct REE signature reflecting different early-to-late diagenetic conditions and/or metamorphic overprint. Pyrite containing petrographic type D, which typically has a flat REE pattern, negative Ce anomaly and positive Eu anomaly, is the best preserved of the four types and best records conditions present during apatite precipitation. Type D phosphatic grains precipitated under (sub)oxic basinal conditions with a significant hydrothermal influence. These characteristics are similar to Zaonega Formation phosphates of NW Russia’s Onega Basin, and consistent with phosphogenesis triggered by the development of anoxic(sulfidic)–(sub)oxic redoxclines at shallow sediment depth during the Paleoproterozoic

Hydrothermal dedolomitisation of carbonate rocks of the Paleoproterozoic Zaonega Formation, NW Russia — Implications for the preservation of primary C isotope signals

This study was supported by Estonian Science Agency project PUT696 and PRG447, and Estonian Centre of Analytical Chemistry. K.P. and A.L. were supported by the Research Council of Norway through its Centres of Excellence funding scheme grant No. 223259.The Paleoproterozoic Zaonega Formation in Karelia, NW Russia, has played a key role in understanding the environmental conditions postdating the Great Oxidation and Lomagundi-Jatuli Events. Its carbonate- and organic-rich rocks (shungite) define the postulated Shunga Event representing an accumulation of very organic-rich sediments at c. 2 Ga and are central in ideas about changing ocean-atmosphere composition in the wake of those worldwide biogeochemical phenomena. Our work focussed on a key interval of carbonate rocks in the upper part of the Formation to: (i) obtain new high-resolution carbon, oxygen and strontium isotope data complemented by detailed petrography and mineralogical characterisation and (ii) expand upon previous studies by using our data to constrain geochemical modelling and show in greater detail how magmatic hydrothermal fluids induced dedolomitisation and altered geochemical signals. Our findings show that the δ13Ccarb of calcite-rich intervals are the most altered, with values between −16.9 to 0.6‰, whereas the dolomite-dominated parts retain the best-preserved (i.e. most original) values. Those define a trend of steadily increasing δ13Ccarb, from −6 to +0.5‰, which we interpret as a return to normal marine conditions and carbonate‑carbon values following the Lomagundi-Jatuli Event.PostprintPeer reviewe

Oxygenated conditions in the aftermath of the Lomagundi-Jatuli Event : the carbon isotope and rare earth element signatures of the Paleoproterozoic Zaonega Formation, Russia

This study was supported by Estonian Research Council project PRG447, and the Estonian Centre of Analytical Chemistry. K.P. and A.L. were supported by the Research Council of Norway through its Centres of Excellence funding scheme grant No. 223259. K.P. acknowledges the Estonian Research Council grant MOBJD542 and T.M. PUT611.The c. 2.0 Ga Zaonega Formation of the Onega Basin (NW Russia) has been central in efforts to understand what led to the initial rise (Great Oxidation Event, GOE) and postulated fall in free atmospheric oxygen and associated high-amplitude carbon cycle excursions, the Lomagundi-Jatuli Event (LJE) and subsequent Shunga Event during Paleoproterozoic time. The Formation accumulated shortly after the LJE and encompasses both the recovery in the carbon cycle and hypothesised contraction of the oceanic oxidant pool. However, interpreting the correct environmental context recorded by geochemical signatures in the Zaonega rocks is difficult due to a complex depositional and diagenetic history. In order to robustly constrain that history, we undertook a multiproxy study (mineralogy, petrography, carbon isotope and rare earth element composition) of carbonate beds in the upper part of the Zaonega Formation recovered in the 102-m composite section of the OnZap drill-cores. Our findings differentiate primary environmental signatures from secondary overprinting and show that: (i) the best-preserved carbonate beds define an upwards increasing δ13Ccarb trend from c. -5.4‰ to near 0‰; and that (ii) large intra-bed δ13Ccarb variations reflect varying contributions of methanotrophic dissolved inorganic carbon (DIC) to the basinal DIC pool. Rare earth element and yttrium (REYSN) patterns confirm a marine origin of the carbonate beds whereas a consistent positive EuSN anomaly suggests a strong high temperature hydrothermal input during accumulation of the Zaonega Formation. Importantly, the presence of a negative CeSN anomaly in the REYSN pattern indicates an oxygenated atmosphere-ocean system shortly after the LJE and indicates that models invoking a fall in oxygen at that time require reassessment.PostprintPeer reviewe

The grandest of them all : the Lomagundi-Jatuli Event and Earth's oxygenation

Funding: K.K., A.L. and T.K. received funding from Estonian Science Agency Project PRG447 and Yu.D., A.R., D.R. and P.M. were supported by the state assignment of the Institute of Geology, Karelian Research Centre of the Russian Academy of Sciences.The Paleoproterozoic Lomagundi–Jatuli Event (LJE) is generally considered the largest, in both amplitude and duration, positive carbonate C-isotope (δ13Ccarb) excursion in Earth history. Conventional thinking is that it represents a global perturbation of the carbon cycle between 2.3–2.1 Ga linked directly with, and in part causing, the postulated rise in atmospheric oxygen during the Great Oxidation Event. In addition to new high-resolution δ13Ccarb measurements from LJE-bearing successions of NW Russia, we compiled 14 943 δ13Ccarb values obtained from marine carbonate rocks 3.0–1.0 Ga in age and from selected Phanerozoic time intervals as a comparator of the LJE. Those data integrated with sedimentology show that, contra to consensus, the δ13Ccarb trend of the LJE is facies (i.e. palaeoenvironment) dependent. Throughout the LJE interval, the C-isotope composition of open and deeper marine settings maintained a mean δ13Ccarb value of +1.5 ± 2.4‰, comparable to those settings for most of Earth history. In contrast, the 13C-rich values that are the hallmark of the LJE are limited largely to nearshore-marine and coastal-evaporitic settings with mean δ13Ccarb values of +6.2 ± 2.0‰ and +8.1 ± 3.8‰, respectively. Our findings confirm that changes in δ13Ccarb are linked directly to facies changes and archive contemporaneous dissolved inorganic carbon pools having variable C-isotopic compositions in laterally adjacent depositional settings. The implications are that the LJE cannot be construed a priori as representative of the global carbon cycle or a planetary-scale disturbance to that cycle, nor as direct evidence for oxygenation of the ocean–atmosphere system. This requires rethinking models relying on those concepts and framing new ideas in the search for understanding the genesis of the grandest of all positive C-isotope excursions, its timing and its hypothesized linkage to oxygenation of the atmosphere.Publisher PDFPeer reviewe

A refined late-Cryogenian – Ediacaran Earth history of South China: : phosphorous-rich marbles of the Dabie and Sulu orogens

This research was supported by the National Natural Science Foundation of China Grant Numbers 41473039 and 4151101015, and by the Estonian Science Agency project PUT0696.The late-Cryogenian – Ediacaran geological framework for South China is constructed principally from sedimentary successions preserved in the central and western regions of the Yangtze Block. New stratigraphic and carbonate-carbon isotope data allow us to extend that framework into the exhumed HP-UHP subduction complexes of the eastern Dabie and Sulu orogens that separate the South and North China cratons. Those data show that marble and phosphorous-rich (P-rich) units in those complexes were originally part of an Ediacaran shallow-marine shelf-carbonate platform. The basal pebbly schist (metadiamictite) and lowermost P-rich marble of the Jinping Formation (Haizhou Group) in the Sulu Orogen matches in both facies character and C-isotope profile that of the Marinoan-equivalent glacial-cap carbonate couplet of the Nantuo and Doushantuo formations. The Daxinwu Formation (Susong Group) in the eastern Dabie Orogen contains a marble unit that has, for several hundreds of metres, a strikingly uniform C-isotope profile of low δ13C positive values and is overlain by a P-rich graphitic schist; these features match those of the late Ediacaran to early Cambrian Dengying Formation. These correlations establish that the HP-UHP metasedimentary rocks, many of which were once considered to be Palaeo- to Mesoproterozoic in age, are a Neoproterozoic-age cover sequence of the continental margin of the Yangtze Block. Further, their widespread development limits their utility as indicators of offset across the Tan-Lu fault zone and, instead, favours tectonic models that interpret that feature as a continental-scale tear fault formed during the Mesozoic collision and suturing of the North and South China cratons.PostprintPeer reviewe

Chromium evidence for protracted oxygenation during the Paleoproterozoic

Accepted manuscript version, licensed CC BY-NC-ND 4.0. It has commonly been proposed that the development of complex life is tied to increases in atmospheric oxygenation. However, there is a conspicuous gap in time between the oxygenation of the atmosphere 2.4 billion years ago (Ga) and the first widely-accepted fossil evidence for complex eukaryotic cells . At present the gap could either represent poor sampling, poor preservation, and/or difficulties in recognizing early eukaryote fossils, or it could be real and the evolution of complex cells was delayed due to relatively low and/or variable O2 levels in the Paleoproterozoic. To assess the extent and stability of Paleoproterozoic O2 levels, we measured chromium-based oxygen proxies in a core from the Onega Basin (NW-Russia), deposited billion years ago—a few hundred million years prior to the oldest definitive fossil evidence for eukaryotes. Fractionated chromium isotopes are documented throughout the section (max. ‰ ), suggesting a long interval (possibly >100 million years) during which oxygen levels were higher and more stable than in the billion years before or after. This suggests that, if it is the case that complex cells did not evolve until after 1.7 Ga, then this delay was not due to O2-limitation. Instead, it could reflect other limiting factors—ecological or environmental—or could indicate that it simply takes a long time—more than the tens to >100 million years recorded in Onega Basin sediments—for such biological innovations to evolve