DETRITAL ZIRCON GEOCHRONOLOGY AND PROVENANCE OF THE PROTEROZOIC QUARTZ-RICH METASEDIMENTS OF THE MAZOWSZE DOMAIN: SOURCE AREAS AND REGIONAL CORRELATION

DETRITAL ZIRCON GEOCHRONOLOGY AND PROVENANCE OF THE PROTEROZOIC QUARTZ-RICH METASEDIMENTS OF THE MAZOWSZE DOMAIN:

SOURCE AREAS AND REGIONAL CORRELATION

GEOCHRONOLOGIA DETRYTYCZNEGO CYRKONU I PROWENIENCJA PROTEROZOICZNYCH BOGATYCH W KWARC SKAŁ METAOSADOWYCH W DOMENIE MAZOWIECKIEJ:

OBSZARY ŹRÓDŁOWE I REGIONALNA KORELACJA L^eszek k^{rzemiński 1}, e^wa k^{rzemińska 1}, J^anina W^{isznieWska 1}

Abstract. Drilling at Mońki IG 2 and Zabiele IG 1 in the Mazowsze domain has intersected mature quartz-rich metasedimentary rocks belonging to the basement of NE Poland, described so far as a Biebrza complex. The geochemical composition of these rocks is charac- teristic of a passive margin. The subarkose–quartz arenite underwent low-T metamorphism, but preserved textures typical for the fluvial sediments. The detrital material in range 1.68–2.11 Ga was provided from surrounding late Paleoproterozoic margins of the Fennoscandia and Sarmatia. The maximum depositional age probably did not exceed 1.6 Ga. A previously suggested correlation with Mesoproterozoic molasse-type deposits of the Jotnian formation has not been confirmed. It seems more likely that the sediments formed after Fennoscandia- Sarmatia collision (i.e. termination of Svecofennian orogeny) but before denudation of the Mesoproterozoic Mazury AMCG intrusions.

Key words: mature metasandstones, zircon U-Pb age, maximum depositional age, Paleoproterozoic, Late Svecofennian, Fennoscandia, Sarmatia.

Abstrakt. W otworach wiertniczych Mońki IG 2 i Zabiele IG 1 na obszarze domeny mazowieckiej rozpoznano dojrzałe, bogate w kwarc skały metaosadowe. Należą one do podłoża krystalicznego północno-wschodniej Polski i były opisywane dotychczas jako kom- pleks biebrzański. Skład geochemiczny tych skał jest charakterystyczny dla krawędzi pasywnej. Skały sklasyfikowane jako arenity kwar- cowe i subarkozy uległy metamorfizmowi niskotemperaturowemu, zachowując jednak struktury typowe dla osadów rzecznych. Materiał detrytyczny o wieku 1,68–2,11 mld lat pochodził z erozji paleoproterozoicznych skał na krawędziach Fennoskandii i Sarmacji. Maksy- malny wiek depozycji materiału okruchowego prawdopodobnie nie przekraczał 1,6 mld lat. Sugerowana wcześniej korelacja z osadami molasowymi mezoproterozoicznej formacji jotnickiej nie została potwierdzona. Bardziej prawdopodobne wydaje się, że osady powstały po kolizji Fennoskandii z Sarmacją (wygasanie orogenezy swekofeńskiej), a przed denudacją mezoproterozoicznych intruzji AMCG ob- szaru Mazur.

Słowa kluczowe: dojrzałe metapiaskowce, wiek U-Pb cyrkonu, maksymalny wiek depozycji, paleoproterozoik, późnoswekofeński, Fen- noskandia, Sarmacja.

INTRODUCTION

During the last decades, the basement of northeastern Po- land located on the edge of Fennoscandia close to the Sarma- tia margin (Fig. 1), have been an object of investigation on

crustal evolution and paleogeography of the East European Craton (EEC) during Paleoproterozoic to Mesoproterozoic time (Bogdanova et al., 2006, 2015 and ref. therein). Recent- ly some of these studies have been focused on detrital zircon analyses, that provide important insights into the provenance

1 Polish Geological Institute – National Research Institute, 4 Rakowiecka Street, 00-975 Warsaw, Poland; e-mail: leszek.krzeminski@pgi.gov.pl.

of detritus (Sultan et al., 2005; Bergman et al., 2008; Wil- liams et al., 2009; Krzemińska et al., 2009). The wide range of information can be extracted from detrital zircon crys- tals, not only evidence of maximum depositional age of the host sediment, but also including the provenance of detrital material, paleogeography and tectonic setting of the source areas, and possible stratigraphic correlations between units (Cawood et al., 2012; Gehrels, 2014). In consequence the tectonic connection and proximity between multiple terranes over geologic time can be approximated. This type of analyt- ical works have been conducted in Precambrian basement of northeastern Poland, where the rocks are known exclusively from deep drill core samples.

The first reconnaissance study of detrital zircon from metasediments recognized by two deep boreholes (Mońki IG 2 and Jastrzębna IG 1), allows to document the maxi- mum depositional age of arc related sediments remarkably similar to that of Svecofennian metasediments known from exposed areas in Sweden and Finland. The Paleoprotero- zoic deposition of sediments in NE Poland, that was con- firmed by detrital zircon data and from the central parts of the Svecofennian orogen in Sweden and Finland, supports the idea of the Svecofennian marginal basin (Rutland et al., 2004; Williams et al., 2009; Krzemińska et al., 2009; Bog- danova et al., 2015).

The mature quartz-rich metasediments from the top of a Precambrian part of the Mońki IG 2 and Zabiele IG 1 core sections are spatially associated with a large Mesoprotero- zoic Mazury Complex dominated by rapakivi-type grani- toids (Fig. 2). Previously they were considered to be part of a “quasiplatform” group of sediments of EEC (Kubicki et al., 1996). The weakly metamorphosed quartz-rich rocks from Mońki and Zabiele were presumed as a Mesoprote- rozoic molasse to belong to the Jotnian formation or even Neoproterozoic cover that filled a grabens and depressions related to the “system of the Gothian dislocations” (Kubicki et al., 1996; Ryka, 1998). The Jotnian sediments were usu- ally assigned to the Riphean Stage of the Mesoproterozoic Era. They are younger than the rapakivi granites and older than post-Jotnian diabase dykes that intrude these sediments, thus were deposited approximately from 1600 to 1260 Ma (Paulamäki et al., 2002 and ref. therein). The Jotnian Meso- proterozoic sedimentary rocks lying on the Paleoproterozoic crystalline bedrock are preserved in a few places within the

Svecofennian domain in Muhos, Satakunta and at Lappa- järvi in Finland and Dalarna and Nordingrå in Sweden. All occurrences of the Jotnian sediments cannot be explained by one single tectonic event or process (Lundmark, Lam- minen, 2016), but many of the Jotnian sandstones are spa- tially closely related to the sites of 1.65–1.5 Ga rapakivi or AMCG magmatism. Here we present the first results of de- trital zircon Pb-Pb geochronology and geochemical study of the quartz-rich samples from two drillings (Mońki IG 2 and Zabiele IG 1), that constrain the age of upper level of meta- sediments and suggest a new chronostratigraphic position of these rocks.

GEOLOGICAL CONTEXT

Over the past two decades a large number of isotope studies in Lithuania, Latvia and Estonia (Claesson et al., 2001; Soesoo et al., 2004) and Poland (Claesson, Ryka, 1999; Krzemińska et al., 2005, 2017) resulted in develop- ing a modern view on geodynamic evolution of East Euro- pean Craton between Fennoscandian and Ukrainian shields.

All isotopic investigations, including U-Pb geochronology, document the Paleoproterozoic age of the crust in this re- gion (Fig. 1; Bogdanova et al., 2015 and ref. therein).

In the northern part of NE Poland, where crystalline base- ment is subdivided into the Mazowsze (MD), Dobrzyń and Pomorze- Blekinge domains, the crust formation were asso- ciated with orogenic activity at c. 1.84–1.80 Ga in the cen- tral part and at 1.79–1.75 Ga in the northwest, completed by anorogenic Mesoproterozoic intrusions of anorthosite-man- gerite-charnockite-granite (AMCG) suites of c. 1.54–1.49 and 1.48–1.45 Ga (Krzemińska et al., 2017). The AMCG suite with dominated A-type rapakivi granitoids forms a long distinctive belt from the southern Lithuania and Bela- rus to northeastern Poland including Mazury Complex. The drill core material in MD comprises various lithology, in- cluding calc-alkaline granitoids (Wiszniewska et al., 2007), Late Paleoproterozoic mafic to intermediate metavolcanics, and metagreywackes (Krzemińska et al., 2005; Krzemińska, 2010). The bottom part of the drill core from the Łomża IG 2 and Mońki IG 2 boreholes is represented predominantly by orthoamphibolites and orthogneisses which crystallized at 1.80 Ga and 1.82 Ga, respectively. Their well-preserved

Fig. 1. Crustal age domains within the western part of the East European Craton (modified from Bogdanova et al., 2015).

Location of the main occurrences of Jotnian sandstone after Kohonen et al. (1993) and Lundmark and Lamminen (2016).

Three-segment subdivision of the East European Craton (left-corner inset) according to Gorbatschev and Bogdanova (1993) SFS – Sarmatia-Fennoscandia suture; TTZ – Teisseyre–Tornquist Zone; MD – Mazowsze domain; DD – Dobrzyń domain; PBB – Pomorze-Blekinge belt;

OJB – Oskarshamn-Jönköping belt; MC – Mazury Complex

Wiek głównych domen skorupowych w zachodniej części kratonu wschodnioeuropejskiego (wg Bogdanovej i in., 2015, zmienione).

Lokalizacja głównych wystąpień piaskowców jotnickich wg Kohonena i in. (1993) oraz Lundmarka i Lamminena (2016).

Podział kratonu wschodnioeuropejskiego na trzy segmenty (lewy narożnik) wg Gorbatscheva i Bogdanovej (1993)

SFS – szew Fennoskandia-Sarmacja; TTZ – strefa Teisseyre’a–Tornquista; MD – domena mazowiecka; DD – domena dobrzyńska; PBB – pasmo Pomorze- -Blekinge; OJB – pasmo Oskarshamn-Jönköping; MC – kompleks mazurski

0o 10^o 20^o 30^o

10o 20^o

o 60o 50

CALEDONIDES

Baltic Sea OJB

T TZ

100

0 200 km

Norwegian Sea

MC

VOLGO- URALIA SARMATIA FENNOSCANDIA

TIMAN

URAL

T TZ

Transscandinavian Igneous Belt (1.81–1.75 Ga) Transskandynawskie Pasmo Magmowe (1,81–1,75 mld lat)

Paleo- to Mesoproterozoic crust reworked during the Sveconorwegian orogeny (1.14–0.92 Ga) / paleo- i mezoproterozoiczna skorupa regenerowana w czasie orogenezy swekonorweskiej (1,14–0,92 mld lat)

AMCG suites and A-type granites (1.651.44 Ga) intruzje AMCG i granity typu A (1,65–1,44 mld lat)

Archean to Paleoproterozoic rocks (3.5–1.88 Ga) ska³y archaiczne i poleoproterozoiczne (3,5–1,88 mld lat)

1.95–1.85 Ga 1.85–1.74 Ga 1.69–1.65 Ga

Paleoproterozoic crust of Fennoscandia and Sarmatia:

Skorupa paleoproterozoiczna Fennoskandii i Sarmacji:

2.0–1.9 Ga 1.90–1.85 Ga Almesåkra

Dala Salmi

Jotnian sandstone occurrences wyst¹pienia piaskowców jotnickich

Fig. 2

KARELIAN DOMAIN

SVECONORWEGIAN

OROGEN

Mälaren Svart lvenä

Gävle

Satakunta Muhos Nordingrå

MD DD

PBB

SFS

Fig. 2. Geological map of crystalline basement of northern part of the Mazowsze domain and AMCG suite showing an inferred distribution of mature quartz-rich metasedimentary rocks (code 31) with a location of the sampling sites: Mońki IG 2 and Zabiele IG 1 boreholes (adapted from Krzemińska et al., 2017) Mapa geologiczna podłoża krystalicznego północnej części domeny mazowieckiej i skał intruzyjnych asocjacji AMCG. Pokazano rozprzestrzenienie dojrzałych, bogatych w kwarc skał metaosadowych i lokalizację opróbowanych otworów wiertniczych: Mońki IG 2 i Zabiele IG 1 (na podstawie mapy Krzemińskiej i in., 2017)

o22o23

o 54 _o 5320’

2 3 4 5

1PALEOZOIC / PALEOZOIK foid syenite / foidowe syenity syenite and quartz syenite / syenity i kwarcowe syenity monzogabbro / monzogabra gabbro / gabra pyroxenite and foid syenite / piroksenity i foidowe syenity

PLATFORM INTRUSIONS INTRUZJE PLATFORMOWE (338354 Ma)

ANOROGENIC INTRUSIONS OF

AMCG SUITE

ANOROGENICZNE INTRUZJE ASOCJACJI AMCG (1.491.54 Ga)

granite, granodiorite and quartz monzonite granity, granodioryty i kwarcowe monzonity quartz monzonite and monzonite kwarcowe monzonity i monzonity charnockitic rocks / charnockitoidy diorite / dioryty monzogabbro and monzodiorite / monzogabra i monzodioryty anorthosite, norite and gabbronorite anortozyty, noryty i gabronoryty

MESOPROTEROZOIC / MEZOPROTEROZOIK PALEOPROTEROZOIC / PALEOPROTEROZOIK granitoids (1.821.84 Ga) / granitoidy (1,82–1,84 mld lat) charnockitoids (1.821.85 Ga) / charnockitoidy (1,82–1,85 mld lat) tonalite, diorite, and gabbro-diorite (~1.83 Ga) tonality, dioryty i dioryty gabrowe (ok. 1,83 mld lat)

SUPRACRUSTAL ROCKS SKA£Y SUPRAKRUSTALNE

quartz metapsammites and mataarkoses, late-orogenic metapsamity kwarcowe i metaarkozy, póŸnoorogeniczne biotite- and garnet-sillimanite-biotite paragneisses, locally migmatized paragnejsy biotytowe i granatowo-sillimanitowo-biotytowe, miejscami zmigmatytyzowane paragneisses with intermediate to felsic metavolcanic intercalations paragnejsy z przewarstwieniami ska³ metawulkanicznych poœrednich i felzytowych intermediate to felsic metavolcanic rocks (~1.84 Ga) poœrednie i felzytowe ska³y metawulkaniczne (ok. 1,84 mld lat) mafic metavolcanic rocks with intermediate and felsic intercalations maficzne ska³y metawulkaniczne z przewarstwieniami ska³ poœrednich i felzytowych

SYNOROGENIC INTRUSIONS INTRUZJE SYNOROGENICZNE

24 2928 31 32 36 40 41

faults and fault zones uskoki i strefy uskokowe inferred faults uskoki przypuszczalne

Moñki IG 2

Zabiele IG 1

9

41 24

12 3231 50 km025

9 12 13 1410 11

volcanogenic features and trace element geochemistry point to a subduction signature and island arc tectonic setting.

These igneous rocks are accompanied by metasediments with increasing maturity recovered within the Mońki IG 1 and IG 2, Łomża IG 1, and Zabiele IG 1 core sections.

The first detrital zircon geochronology in MD area was conducted on metagraywacke from the Mońki IG 2 drilling, depth 819 m (Williams et al., 2009). The ages of youngest detrital zircon and the metamorphic overgrowths formed af- ter 1.83–1.82 Ga constrain the maximum deposition age (pe- riod 1.86–1.82 Ga), similar to that of some sediments from the exposed part of Fennoscandia, e.g. from the Västervik area in SE Sweden (Sultan et al., 2005) and Tiirismaa, Py- häntaka and Luukkola areas in southeastern Finland (Berg- man et al., 2008). The geochemical signatures of the arc magmatism at 1.83–1.80 Ga (Krzemińska et al., 2005) and similar characteristics of the accompanied metasedimentary unit provide convincing evidence for the existence of an ac- tive continental margin in the area of Fennoscandia which is now overlain by Neoproterozoic to Phanerozoic cover (Wil- liams et al., 2009). This margin was coeval with the juvenile volcanic arc of the Oskarshamn-Jönköping belt formed at 1.83–1.82 Ga and exposed in SE Sweden (Mansfeld et al., 2005).

QUARTZ-RICH SAMPLES

Further investigation of metasediments including detrital zircon and geochemical provenance study were performed on the upper part of sedimentary succession of Mońki IG 2 and Zabiele IG 1 drill sections (Fig. 2), that is represented by weakly metamorphosed quartz-rich rocks (quartzites). These quartzites were previously interpreted as a quasi- platform cover probably Neoproterozoic or Late Mesoproterozoic in age, formed during post-Gothian peneplenisation as a mo- lasse-type deposit (Kubicki et al., 1996) after emplacement of Mesoproterozoic Mazury Complex. Correlation with the Jotnian sediments exposed in the Central Fennoscandia (Baltic Shield) was suggested. This metasedimentary for- mation composed of a quartz arenites and subarkoses was described as the Biebrza complex (Ryka, 1998) occurred in Mońki IG 2 (N: 53°26'10" and E: 22°44'45") at a depth of 626 to 745.7 m and in Zabiele IG 1 (N: 53°32'42" and E:

22°57'55") at a depth of 557.5 to 619 m. Horizontally bed- ded or slightly deformed siliciclastic sediments were weakly metamorphosed in the range from zeolite to greenstone fa- cies. All primary features observed are typical for the fluvial sandstone (Fig. 3).

ANALYTICAL METHODS

Chemical analyses of 22 whole-rock samples were per- formed at the Central Chemical Laboratory of the Polish Geological Institute – NRI, Warsaw. The major element compositions were analysed by X-ray fluorescence (XRF)

on glass beads formed by fusing a sample with lithium me- taborate LiBO₂, and the Zr concentrations were determined on pressed powder pellets, using a Philips PW2400 sequen- tial spectrometer in both cases. The concentrations of Th and Sc were determined by inductively coupled plasma mass spectrometry (ICP-MS) using a Perkin Elmer ELAN DRC II system. The samples were air-dried and ground, and then were decomposed with multi-acid digestion including hy- drofluoric acid. The analytical accuracy and precision were found to be better than 1% for major elements, 5% for Zr and Th, and 10% for Sc, as checked by international stand- ards and analysis of replicate samples.

Three samples for geochronology were processed by standard methods for separating zircon grains, i.e. crushing, sieving, heavy liquids as well as a Frantz isodynamic sepa- rator and final hand-picking at the University of Wrocław.

The zircon concentrates together with chips of the reference zircons Temora-2 and SL13 were mounted in epoxy and pol- ished until quasi-central sections were reached. The U-Pb detrital zircon analyses were conducted by SHRIMP II at the Research School of Earth Sciences, Australian Nation- al University in Canberra, according to the procedure and strategy described in more detail by Williams et al. (2009).

The random selection of grains has been applied during this study of detrital zircon (cf. Fedo et al., 2003) and only grains with strong surface imperfections were avoided. Cathodo- luminescence (CL) technique was used to identify distinct zircon domains. The U, Th and Pb isotope ratios were an- alyzed using Duoplasmatron that produced primary ion beam from a high-purity oxygen. The sputtered secondary ions were extracted at 10 kV collected on a single electron multiplier by cycling the magnet through five scans across the nine mass: ¹⁹⁶Zr₂O, ²⁰⁴Pb, 204.1 as a background, ²⁰⁶Pb,

Fig. 3. Typical lithofacies in drill core samples from Mońki IG 2 (depth 742 m) and Zabiele IG 1 (depth 610 m) showing

quartz-rich layers alternating with chlorite-sericite rich fine-grained lamellae. Scale in centimetres Typowa litofacja w próbkach rdzenia wiertniczego z otworów

Mońki IG 2 (głęb. 742 m) i Zabiele IG 1 (głęb. 610 m).

Warstwy bogate w kwarc przewarstwione drobnoziarnistymi laminami bogatymi w chloryt i serycyt. Skala w cm

Zabiele IG 1 610 m Moñki IG 2

742 m

207Pb, ²⁰⁸Pb, ²³⁸U, ²⁴⁸ThO, and ²⁵⁴UO). The measurements were carried out with a mass resolution of approximately 5000 (at 1% peak height). Analyses were conducted using a beam diameter of ~20×24 μm, generating a pit depth of c. 4–5μm. The ²⁰⁶Pb/²³⁸U ratios were calibrated using the Te- mora-2 with ²³⁸U/²⁰⁶Pb age 416.78 ±0.33 Ma (Black et al., 2004), but U concentration on standard SL13 (U = 238 ppm, U-Pb 572 Ma; Claoué-Long et al., 1995). The analyses were conducted in a sequence consisting of one analysis of a Te- mora-2 reference zircon measurement after every fourth un-

known sample analysis. Raw data were reduced using the SQUID2 Excel Macro software and the diagrams were gen- erated by Isoplot (Ludwig, 2003).

GEOCHEMISTRY

The metasediments from Mońki and Zabiele contain about 92–97 wt.% and 89–97 wt.% of SiO₂ respectively, thus their high SiO₂/Al₂O₃ ratio indicates high maturity of the sediments. Geochemically, these rocks are classified mainly as subarkose to quartz arenite in contrast to the original shale or wacke composition of previously analyzed paragneisses in the Mońki section from depth 819 to 1020 m (Fig. 4A).

The values of Chemical Index of Alteration (CIA) of these mature rocks vary from 69 to 83, indicating moderate to high degree of weathering in the source areas. The K₂O/Na₂O ra- tio, that specify of the potassium feldspar and mica versus plagioclase content in the rock, allows to determine the tec- tonic setting of terrigenous sedimentary rocks i.e. volcanic arc (Arc), active continental margin (ACM) to passive mar- gin (PM) settings (Roser, Korsch,1986). The K₂O/Na₂O vs.

SiO₂ plot for the rocks from Zabiele and Mońki quartz–rich part of the section, along with data from the bottom part of metasedimentary succession (Mońki), document the transi- tion from an active continental margin to passive margin set- ting (Fig. 4B). This ACM to PM shift can be confirmed using the trace element contents on Sc-Th-Zr diagram (Fig. 4C).

DETRITAL ZIRCON GEOCHRONOLOGY Isotopic U-Th-Pb data and ages of a single spot SHRIMP analyses of zircon grains from the Mońki (740 m) and Za- biele (610 m) metasandstones are reported in full as Table 1.

Final ages quoted in the text are at 2σ error, whereas those (single spot) in the Table 1 are reported at 1σ error. The

Fig. 4. Geochemical classification and tectonic setting discrimination diagrams for Mońki and Zabiele quartz-rich

metasedimentary rocks (this study) and paragneisses from Late Paleoproterozoic part of the Mońki section

(data from Williams et al., 2009)

A – Log (Fe₂O₃*/K₂O) vs Log (SiO₂/Al₂O₃) after Herron (1988); B – K₂O/

Na₂O vs SiO₂ after Roser and Korsch (1986); C – Sc–Th–Zr/10 diagram after Bhatia and Crook (1986); PM – passive margin; ACM – active conti- nental margin; CIA – continental island arc; OIA – oceanic island arc

Klasyfikacja geochemiczna i diagramy dyskryminacyjne środowiska tektonicznego dla bogatych w kwarc skał metaosadowych z Moniek i Zabieli (niniejsza praca) oraz późnopaleoproterozoicznych paragnejsów z profilu Mońki

(dane z pracy Williamsa i in., 2009)

A – Log (Fe₂O₃*/K2O) vs Log (SiO₂/Al₂O₃) wg Herrona (1988); B – K₂O/

Na₂O vs SiO₂ wg Rosera i Korscha (1986); C – Sc–Th–Zr/10 wg Bhatii i Crooka (1986); PM – krawędź pasywna; ACM – aktywna krawędź konty- nentalna; CIA – kontynentalny łuk wysp; OIA – oceaniczny łuk wysp Log (SiO /Al O )

0.3 0.8 1.3 1.8

–1 0

1 Fe-shale

¿elazisty

³upek ilasty Shale

³upek ilasty

Fe-sand piasek ¿elazisty

Litharenite arenit lityczny

Sublitharenite arenit sublityczny

Arkose arkoza

Subarkose subarkoza Wacke /

waka

Quartz arenite arenit kwarcowy

Log (Fe O */K O)

SiO (wt.%) PM

ACM Arc³uk

100 10 1

0.1 0.01

K O/Na O

60 70 80 90

A

Metamud- stone metamu³owiec

Zabiele IG 1

Moñki IG 2, quartz-rich Moñki IG 2, bogate w kwarc Moñki IG 2, paragneisses Moñki IG 2, paragnejsy Metamud-

stone metamu³owiec

Th

Sc Zr/10

ACM

CIA

OIA PM

Metamud- stone metamu³owiec 22

2

2 2 3

322

B

C

Table 1 U-Th-Pb analytical results for zircons from Mońki and Zabiele metasandstones Wyniki analityczne U-Th-Pb dla cyrkonu z metapiaskowców w profilach Mońki i Zabiele Pb*UThTh/U208Pb*/206Pb±206Pb*/238U±207Pb*/235U±207Pb*/206Pb±Apparent ages (Ma)% Grain.spotppmppmppm206/238±207/235±207/206±concordant Mońki 740 Cores M-1.1561471100.750.21890.00350.33280.00525.180.120.11280.0017185225184920184527100 M-2.157141970.690.19810.00270.35370.00335.910.070.12110.000919521619621119731399 M-3.1601491040.700.19890.00240.35100.00396.090.100.12590.001519391819891520412195 M-4.156154400.260.07240.00170.35330.00395.890.090.12100.001119511919611319711699 M-5.1922422571.060.23960.00410.32220.00435.540.120.12470.002018012119071920252989 M-6.1411021101.080.30550.00630.32910.00465.080.100.11210.0012183423183416183320100 M-7.1832011140.570.16370.00180.37170.00486.420.120.12520.0014203823203516203220100 M-8.181199850.430.11820.00150.37860.00696.620.140.12680.0012207032206219205417101 M-9.1621431210.840.23580.00350.36760.00426.300.100.12430.0012201820201814201817100 M-10.138101460.460.12840.00390.35070.00515.740.120.11870.0015193824193718193623100 M-11.1521421100.780.22120.00250.31920.00454.980.090.11320.001117862218161518511797 M-12.12872430.590.16380.00530.35530.00985.790.200.11820.0022196047194531193034102 M-13.1701911600.840.22030.00320.31900.00384.850.080.11020.001117851917931418031899 M-14.154150410.270.07730.00160.34810.00665.810.140.12110.001619263219482119722398 M-15.166180630.350.09450.00170.35380.00395.840.080.11980.0010195319195313195315100 M-16.161168490.290.07660.00170.35210.00415.860.110.12070.001719451919551719662699 M-17.149127610.480.13900.00330.35710.00775.880.160.11940.0018196937195824194727101 M-18.1954003050.760.07490.00730.23350.00303.630.120.11280.003213531515562618455273 M-20.148132790.600.17110.00310.32590.00445.050.090.11250.001218182118281618401999 M-21.141107950.890.25850.00430.32720.00465.110.090.11330.001118252218381518531799 M-22.1962621460.560.13840.00220.33770.00495.570.110.11960.001318762419121719512096 M-23.111771810051.400.16350.00440.14690.00112.480.040.12230.0018884612651319902744 M-24.162161780.480.14000.00290.35500.00365.770.080.11790.0009195817194212192514102 M-25.139101540.540.15110.00260.35570.00475.960.110.12160.001419622219711619802099 M-26.11001711801.050.25520.00340.46950.006311.900.200.18380.001724822825961626871592 M-27.13186610.710.20120.00460.32340.00555.010.110.11230.001218062718211818382098 M-28.1641891310.690.10700.00440.31860.00495.240.150.11930.002717832418592519454092 M-29.143125830.660.18680.00410.31070.00424.600.090.10750.001417442117501717572499 M-30.162173450.260.07210.00190.35180.00545.790.110.11940.0011194326194517194717100 M-31.1902272261.000.28370.00220.32980.00515.280.100.11610.001118372518661718981797 M-32.1832492941.180.28200.00360.27800.00274.350.070.11340.001315811417031418552285 M-33.1642001660.830.16040.00370.28960.00424.840.100.12110.001716402117911819732683 M-34.172187610.330.08970.00140.36610.00676.410.130.12690.000920113220331820561298 M-35.146134560.420.11690.00230.32260.00554.960.110.11150.001518022718131918242499 M-36.141110870.790.22260.00280.32410.00434.950.090.11070.0013181021181016181021100 Mońki 742 Overgrowths MO-1.118025452940.120.31520.02620.05870.00130.6990.1010.08640.01213688538621346297discordant MO-2.18611652930.250.22130.01250.06520.00070.8670.0530.09660.00564074634291559114discordant MO-3.181257780.300.07160.00210.31050.00414.7390.1010.11070.0017174320177418181128discordant MO-4.1959703940.410.24490.01280.08480.00081.1410.0600.09760.0049525577329157898discordant MO-5.1404465021.130.31350.02250.07330.00111.1540.0970.11410.00924567779471866153discordant MO-6.1102242310540.440.43080.01890.03160.00050.4700.0380.10790.00832013391261764147discordant

Table 1 cont. Pb*UThTh/U208Pb*/206Pb±206Pb*/238U±207Pb*/235U±207Pb*/206Pb±Apparent ages (Ma)% Grain.spotppmppmppm206/238±207/235±207/206±concordant Zabiele 610 Cores Z-1.186223860.390.11000.00130.36310.00356.170.080.12330.0009199716200111200514100 Z-2.1671941710.880.18890.00410.31060.00354.790.110.11180.002217441717832018293695 Z-3.152141590.420.11560.00210.35080.00455.610.110.11600.0015193922191817189623102 Z-4.1581361130.830.23510.00250.36570.00416.070.120.12040.0017200920198617196225102 Z-5.14193780.830.24010.00290.37570.00806.460.160.12470.0013205638204022202419102 Z-6.158158490.310.08700.00200.35550.00415.830.090.11890.0011196120195014193917101 Z-7.1743843881.010.19130.00400.17340.00132.480.050.10380.00211031712671616943761 Z-8.11006438361.300.19220.00580.13930.00101.980.050.10320.0024841611101716834350 Z-9.16593850.920.24380.00320.56400.012515.870.390.20410.0017288352286924286014101 Z-10.11132251650.730.15140.00250.44260.004810.040.140.16450.001123622224381325021294 Z-11.1661881280.680.19130.00180.31540.00304.640.080.10680.0014176715175715174525101 Z-12.174201730.370.09340.00120.35390.00485.920.110.12130.001319532319641619761999 Z-13.157190870.460.10380.00300.28700.00314.570.080.11540.001516261617431518862386 Z-14.1732242110.940.20380.00270.29000.00294.350.060.10890.001016421417041217811792 Z-15.11053321820.550.12040.00170.29740.00324.650.070.11330.000916781617581218541491 Z-16.163180640.360.09830.00220.33320.00495.370.110.11700.001318542418811719102197 Z-17.146129820.630.17800.00320.31930.00364.900.080.11130.001017861818021318211798 Z-18.1731971140.580.16060.00210.33630.00385.470.080.11800.000918691818971319271497 Z-19.1791721941.130.31640.00310.36970.00446.630.100.13020.001120282120641421001597 Z-20.13797520.530.15170.00210.34550.00735.710.160.11990.001919133519332419552898 Z-21.11132891760.610.17420.00220.35030.00315.810.070.12030.000919361519481119611399 Z-22.13190320.350.09890.00260.32900.00545.250.110.11570.001418342618611918912297 Z-23.12568540.800.15080.00350.33960.00755.560.160.11880.001718853619112419392697 Z-24.178138610.440.11710.00140.50600.007012.800.210.18340.001326403026651526841298 Z-25.12877380.500.13580.00360.34110.00705.450.140.11590.0014189234189322189422100 Z-26.11154204921.170.20200.00230.24050.00183.920.050.11830.00101389916181019301572 Z-27.1101290950.330.08870.00110.33680.00435.530.100.11900.001418712119051619412196 Z-28.155152630.410.11790.00250.33880.00375.490.080.11750.000918811818991219181498 Z-29.168190920.480.09790.00180.34290.00515.700.100.12060.001019012519321619661597 Z-30.173215880.410.11400.00170.32080.00544.810.090.10870.0008179426178616177813101 Z-31.1802411340.550.15620.00160.30510.00314.540.070.10810.001017161517391217671697 Z-32.165179560.310.08770.00140.35110.00485.800.100.11990.001119402319471519551699 Z-33.1641891190.630.15820.00190.31060.00294.790.060.11180.000917441417821118281595 Z-34.1692071150.560.15630.00170.30830.00284.630.060.10890.001017321417541217801797 Z-35.167185520.280.07970.00180.35150.00385.810.090.11980.001119421819471319531799 Z-36.179223680.300.08410.00140.34320.00465.730.090.12100.000919022219361419721397 Z-37.151119590.500.13250.00190.39220.00507.080.110.13090.0011213323212115211015101 Z-38.165178540.300.08460.00160.35310.00445.930.090.12180.000919492119661419831498 Z-39.161172810.470.10010.00180.33650.00525.530.110.11910.001218702519051719431996 Z-40.1631751320.760.22410.00220.30980.00344.940.080.11570.001317401718091418902192

results are plotted on concordia diagrams (Fig. 5) and shown on probability density plots (Fig. 6A, B). A total of 35 and 40 randomly selected cores of detrital zircon grains from both samples were analyzed. Individual zircon grain ages were evaluated using ²⁰⁷Pb/²⁰⁶Pb ratios (all grains are older than 1.0 Ga). The Pb-Pb age distributions demonstrate (Fig. 5) that detrital material was derived mainly from Paleoprotero- zoic sources with ages in the range of 1.76–2.06 Ga in Mońki (740 m) and 1.68–2.11 Ga in Zabiele (610 m), and Archean grains (older than 2.5 Ga) are rare. Within dominated Paleo- proterozoic population the ages are grouped in two clusters (Fig. 6A, B): older with the major peak age at 1959 Ma (Za- biele) and 1966 Ma (Mońki), and a minor younger cluster peaked at c. 1779 Ma (Zabiele) and 1847 Ma (Mońki). The similar prevailing population peaked at 1969 Ma (Fig. 6C) was previously recognized in Mońki metagreywacke at depth 819 m (Williams et al., 2009). The comparison of all three samples (Fig. 6A–C) shows that most prominent group of detritus are the same with peak at 1.96 Ga, but the young- er populations are slightly different from those recognized

in Mońki at depth 819 m. The youngest concordant grains were dated at 1816 ±22 Ma (Mońki 819 m), 1757 ±24 Ma (Mońki 740 m), and 1685 ±43 Ma (Zabiele 610 m). Usually, the youngest detritus should define maximum depositional age, but only within orogenic setting. The lack of interlay- ered volcanics or crosscutting intrusive rocks make impossi- ble precise delimitation of deposition time. The recognizable differences associated with the youngest age group derived from a proximal source, demonstrate a delivery of increas- ingly younger detritus, according to the stratification from the bottom to the top.

Despite a short distance (<100 km) between quartz-rich succession and AMCG suite as the potential source area, the Mesoproterozoic component was not detected in the clastic material whose deposition has finished before denudation of the AMCG suite with emplacement age of 1.54–1.49 Ga (Fig. 2). Most of the regional studies in central Fennoscandia show, that distribution of Jotnian sediments (Fig. 1) has to be spatially associated with the occurrence of Mesoprotero- zoic rapakivi granite and their deposition has been continued

Zabiele 610 m n=40

2600

2200

1800

1400

1000 0.10

0.14 0.18 0.22

data-point error ellipses are 2 sigma A

Moñki 740 m n=35

2600

2200

1800

1400

1000 0.10

0.14 0.18 0.22

1.5 2.5 3.5 4.5 5.5

data-point error ellipses are 2 sigma C

Pb/ PbPb/ Pb

U/ Pb

207207206206

238 206

B

D

Fig. 5. U-Pb concordia diagrams and CL images showing the results of single-grain detrital zircon analyses from metasedimentary rocks: (A–B) Zabiele IG 1 (depth 610 m); (C–D) Mońki IG 2 (depth 740 m)

Diagramy zgodności wieku U-Pb i obrazy CL detrytycznego cyrkonu ze skał metaosadowych: (A–B) Zabiele IG 1 (głęb. 610 m);

(C–D) Mońki IG 2 (głęb. 740 m)

long after the 1.55 Ga anorogenic magmatism up to 1.26 Ga (Amantov et al., 1996; Pokki et al., 2013; Lundmark, Lam- minen, 2016). The K-Ar datings of the Jotnian sandstone in Finland documented a diagenesis time at approximately 1300 Ma (Kohonen et al., 1993).

Both types of sediments from the Mońki, i.e. quartz-rich sandstones (e.g. interval 740 and 742 m) and greywacke to shale (e.g. depth 819 m) were affected by low- temperature metamorphism, forming subtle low-luminescent over- growths (Figs. 5 and 7). Only a few zircon rims from these metasedimentary rocks (Mońki sample) were analyzed, giving however an uncertain results (Fig. 7). The analyses which have experienced isotopic disturbance plot off the concordia line. It is a visual record of Pb exchange with the external environment by intra-grain Pb mobility (Pb-loss) and diffusion in metamict zircon. Such problem of open U-Pb system is one of the most important limiting factors in the reliable interpretation of isotope ratios. Sometimes how- ever Pb-loss is caused by geological events, thus discord- ant ages may provide geochronologically useful information (e.g. Gehrels, 2014; Reimink et al., 2016 and ref. therein).

As a consequence, a discordia-line with a lower intercept on concordia diagram may be considered as a diagnostic tool to interpret single zircon age data. The lower intercept on concordia diagrams at 1833 ±67 Ma (depth 819 m) and 1813

±57 (depth 742 m) is probably the combined result of Pb- loss and/or new zircon growth during a low-T metamorphic event. This time of Pb-loss event together with deficiency of grains younger than 1.6 Ga may suggest that the effective deposition time was probably completed before 1600 Ma.

SOURCE AREAS

The seismic and geological data indicate that, about 2.0 billion years ago, the Fennoscandian and Sarmatian lith- ospheric plates were separated by the Belarus oceanic plate (Garetsky, Karatayev, 2011). The period of about 1.82–

1.80 Ga was interfered with the first oblique collision of the Fennoscandia and Sarmatia (Volga–Sarmatia), that was com- pleted before 1.70 Ga (Lubnina et al., 2016). The Mońki and Zabiele sediments deposited north of Fennoscandia–Sarma- tia suture during final collision have to contain detritus from the both blocks. It is very likely that westernmost Sarmatia with Andean-type Osnitsk–Mikashevichi igneous belt (OMI) at 2.10–1.96 Ga has become the most significant source of detritus older than 1.96 Ga. The complementary isotope in- formation e.g. O and Hf signatures of dated zircon from the Mońki metagreywacke supports this hypothesis. The average δ¹⁸O_zrn of 5.95 ±0.26‰ suggests a significant amount of juve- nile “mantle-derived material” mixed with crustal slightly el- evated oxygen isotope composition (Krzemińska et al., 2016).

Moreover the comparison of new ¹⁷⁶Hf/¹⁷⁷Hf and ¹⁷⁶Lu/¹⁷⁷Hf zircon data (Wiszniewska et al., 2018) showed a similarity of age and Hf isotope signatures of Mońki detritus versus zircon from felsic juvenile igneous rocks from north-west region of the Sarmatia (Shumlyanskyy et al., 2015).

Fig. 6. Relative probability plots of concordant and nearly concordant ²⁰⁷Pb/²⁰⁶Pb detrital zircon ages representing the main clusters of detritus from (A) Zabiele IG 1 (depth 610 m) and (B) Mońki IG 2 (depth 740 m) metasediments (this study),

and (C) Mońki IG 2 (depth 819 m) paragneisses (data from Williams et al., 2009)

Krzywe względnego prawdopodobieństwa zgodnego i prawie zgodnego wieku ²⁰⁷Pb/²⁰⁶Pb detrytycznego cyrkonu reprezentujące

główne grupy materiału okruchowego w skałach metaosado- wych (A) z profilu Zabiele IG 1 (głęb. 610 m) i (B) Mońki IG 2 (głęb. 740 m) (niniejsza praca) oraz (C) w paragnejsach z profilu

Mońki IG 2 (głęb. 819 m) (dane z pracy Williamsa i in., 2009) Zabiele 610 m

1 2 3 4 5 6 7 8 9 10

1959

1779

2100

Moñki 740 m

1 2 3 4 5 6 7 8 9 10

1966 1847

2052

1 2 3 4 5 6 7 8 9 10 11 12 13 14

1500 1700 1900 2100 2300 2500 2700 2900

Moñki 819 m

2700 1969

2043 1869

Paleoproterozoic paleoproterozoik Meso-

mezo- Archean

archaik

Relative probability Prawdopodobieñstwo wzglêneRelative probability Prawdopodobieñstwo wzglêneRelative probability Prawdopodobieñstwo wzglêne

Number / LiczebnoϾNumber / LiczebnoϾNumber / LiczebnoϾ

A

B

C

Pb-Pb age [Ma]

Wiek Pb-Pb [mln lat]