A synthesis of available detrital zircon data from Turkey, Cyprus and Greek peninsula

This paper describes the assembly of an updated dataset of detrital zircon geochronology and Lu–Hf isotopes for Turkey, Cyprus and Greek peninsula. This first version of the dataset documented 286 samples with detrital zircon U–Pb data and 70 samples with zircon Lu–Hf isotopes from 42 published articles. These samples are mainly distributed in seven geologic‐tectonic units in the Eastern Mediterranean Tethyan region. The compilation of dataset will be periodically accessed in the Deep‐Time Digital Earth repository, containing more updated raw data of (un)published scientific research. We believe that the construction of such a dataset is fundamental to studies of clastic strata and also to understanding of crustal evolution in the Eastern Mediterranean region.


| INTRODUCTION
Detrital zircons of sedimentary rocks have been widely used in sedimentary provenance analysis and crustal evolution studies (e.g.Cawood et al., 2012;Gehrels, 2014).The advancement of in-situ analytical techniques, for example Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS), enables a rapid acquisition of large amount of detrital zircon data, which not only presents challenges to data visualization/comparison (e.g.Saylor & Sundell, 2016;Sundell & Saylor, 2017) but also highlights the need for accessibility of these large, systematic databases from any geographic region.
This study compiles a new detrital zircon database for Turkey, Cyprus and Greek peninsula (Figure 1) from the current pool of published research articles, including zircon U-Pb ages and Lu-Hf isotope data, which provides a means for statistically constraining the timing of geological events and tectonic processes, for understanding related sediment-transport pathways and for unravelling the record of crustal-mantle evolution concerning the Tethyan geology in the Eastern Mediterranean.These coincide with the aim of the Deep-Time Digital Earth (DDE) programme, which means to share global geoscience knowledge, and facilitate data-driven discovery in the understanding of Earth's evolution (Wang et al., 2021).

| Present databank and category of the dataset
We compile a new detrital zircon database that includes details from all labs, in published articles and/or repositories.The new database includes categories of data source (literature information), sample information, laboratory analysis details (e.g.laboratory names, type of mass spectrometer, etc.), U-Pb-Th isotopic data (e.g.U-Pb ratios, ages, uncertainties for the three primary U-Pb chronometers) and also Lu-Hf isotopic data (Table 1).
An extensive search for U-Pb detrital zircon samples yields an independent database of 29,272 age records.Previous zircon analysis of 10 research articles yields a total of 4,982 (70 samples) Lu-Hf isotope analyses.The Eastern Mediterranean region, situated between the North African, Arabian and Anatolian plates, is characterized by documenting important geological records of the tectonically emplaced remnants of Neotethys and a larger preceding Tethys Ocean, Paleotethys (e.g.Robertson & Dixon, 1984;Şengör & Yılmaz, 1981;Stampfli & Borel, 2002;van Hinsbergen et al., 2020).The tectonic mosaic of microcontinents and oceanic basins was related to a series of tectonic processes, including continental rifting, subduction-accretion, continent-continent collision, post-collisional exhumation and strike-slip (e.g.Robertson & Dixon, 1984).Detailed consideration of the evolution of the Mediterranean Tethys is beyond the scope of this paper.Although different tectonic divisions were adopted previously (e.g.Çetinkaplan et al., 2020;Göncüoğlu et al., 1997;Okay & Tüysüz, 1999;Zulauf et al., 2019), these data are distributed in seven major units by their geologic-tectonic characteristics, including Southeast Anatolian Autochthon Belt, Taurides, Anatolides, Pontides, Cycladic Complex, External Hellenides and Cyprus Island (Figure 1).

| Data visualization methods
Original age data as well as common lead corrections were preferentially adopted from the related references without further recalculation.Toolbox IsoplotR (Vermeesch, 2018)   a <30% discordance for zircons analysed.It should be noted that U-Pb isotope data of single grain evaporation analyses of zircons (e.g.Chen et al., 2002) were adopted without discordance calculation in this study.In addition, the best ages of Abbo et al. (2015), Zlatkin et al. (2013) etc. were filtered by suggested depositional ages in the related paper; for example Neoproterozoic.
A python-based toolset of detritalPy (Sharman et al., 2018) was used to visualize the age spectra.Cumulative distribution function (CDF) and Kernel density estimates (KDE) were plotted to illustrate the zircon age distributions.CDF was binned at 1 Ma increments.For the KDEs, bandwidths were set at 5 and 20 Ma, with fixed bin widths of 10 and 30 Ma for the time windows of 0-541 and 0-4,000 Ma, respectively.Programme DZmds is used for multidimensional scaling (MDS) of detrital zircon U-Pb age distributions (Saylor et al., 2018).

| RESULTS
Below, we summarize the U-Pb, Lu-Hf isotopes for the detrital zircons compiled.Related raw data are presented by the seven major geographic-geological units (Table 2; Figure 2).It should be noted that some samples were exposed in the tectonically complex units, for example suture zones, melanges and multiple terranes (e.g.Pontides, Cyprus) and are assembly shown here as exemplification.
Meticulous tectonic affinity discrimination of samples should be carried out for any further study.

Belt
There are only three samples (n = 470 grains) from the Early Cambrian to the Late Ordovician (Figure 2) compiled for the Southeast Anatolian Autochthon Belt from the literature.These grains are nearly all Precambrian zircons, with Ediacaran (peak at 641 Ma), Tonian (peak at 762, 856 and 990 Ma), Middle Paleoproterozoic (peak at 1974 Ma) and Neoarchean (peak at 2599 Ma) maximum probabilities (Figure 3).Two samples, 256 Lu-Hf isotope analyses in total, were compiled for the Southeast Anatolian Autochthon Belt.The predominant Neoproterozoic zircon age groups of the Southeast Anatolian Autochthon Belt were extensively derived from juvenile to evolved sources based on their εHf(t) values (Figure 4a).The positive εHf(t) values make ca.54% of the data and therefore, indicating juvenile sources.Subsidiary zircon age groups of the older age groups (>900 Ma) in the Southeast Anatolian Autochthon Belt were mainly derived from evolved sources, with characteristic negative εHf(t).

| Anatolides
The Anatolides consists of two main regional metamorphic complexes: the Tavşanlı Zone to the north and the Afyon Zone to the south.The Carboniferous to Triassic-Jurassic samples were compiled for the Konya Complex, Anatolides (n = 9; 825 grains; Figure 2), which are characterized by significant zircon populations of Middle Ordovician (468 Ma), Early Devonian (406 Ma) and Middle Triassic (242 Ma), together with subordinate Neoproterozoic grains (peaks at 590 Ma, 643 and 887 Ma; Figure 3).There are also minor Paleoproterozoic (1980 and 2039 Ma) and Neoarchean (2638-2689 Ma) fractions.
Zircon analysis of 17 samples yielded a total of 1,397 Lu-Hf isotope analyses.The εHf(t) values of the zircon grains from Pontides samples range between −30 to +14 (Figure 4c), whereby the negative εHf(t) values make 73%.Paleoproterozoic and Archean zircons show mostly negative εHf(t) values, occupying about 68% of the data analysed.The negative εHf(t) values are found in 62% of the Neoproterozoic zircons.Detrital zircons of Cambrian to Triassic ages display εHf(t) values ranging between −29 and +9.Late Mesozoic and younger zircons are rare, and the εHf(t) values of these zircon grains vary between −15 and + 2. The negative values occupy 75% of the data.

| Cycladic Complex
There are 3,806 grains (37 samples in total) compiled for the Cycladic Complex, with an age range from Late Neoproterozoic to Cretaceous (Figure 2).Concordant ages of significant zircon populations dominantly group at Ediacaran (peak at 601 Ma), Tonian (peak at 987 and 762 Ma), Middle Paleoproterozoic (peak at 2023 and 1885 Ma) and Neoarchean (peak at 2611 Ma; Figure 3).Palaeozoic zircons mainly cluster in the Cambrian (peak at 447 Ma) and late Carboniferous (peak at 305 Ma).There is also a significant Mesozoic zircon population of Late Triassic (peak at 235 Ma).Late Cretaceous grains rarely occur, mainly peak at 80 Ma.

| External Hellenides
Twenty-samples containing 1837 U-Pb data records collected from the published articles, which are from the Precambrian to the Triassic strata (Figure 2).Concordant zircons are characterized by prominent Precambrian populations, with mainly Ediacaran (peak at 601 Ma), Tonian (973 Ma) zircons, together with minor fractions of Middle to Late Paleoproterozoic and Neoarchean ages (Figure 3).Palaeozoic zircons mainly cluster in the Cambrian and early Carboniferous.

| Cyprus Island
There are three main tectonic terranes making up Cyprus: the Troodos Massif, Mamonia Complex and Kyrenia Range (Figure 1).Zircons in samples (n = 43; 4,791 grains) from different tectonic terranes (i.e. the Mamonia Complex and the Kyrenia Range) of Cyprus are mainly Neoproterozoic; that is Ediacaran (peak at 615 Ma), Tonian (796 and 963 Ma), together with minor fractions of Paleoproterozoic (2,495 and 2046 Ma) and Archean (peak at 2627 Ma) ages (Figures 2  and 3).Palaeozoic zircons mainly cluster in the Cambrian, late Carboniferous (peak at 309 Ma), Late Triassic (234 Ma) and Late Cretaceous (peak at 77 Ma).

| Brief summary of characteristic provenance
The Precambrian zircon age spectra, especially Neoproterozoic zircon populations, can be correlated to detritus of north Gondwana origin (i.e.NE Africa/Arabian-Nubian Shield), although both primary and secondary (recycled) materials are possible (e.g.Chen et al., 2019Chen et al., , 2022;;Shaanan et al., 2021).The involved juvenile materials have relatively positive εHf(t) values, while the recycled crustal additions have negative εHf(t) values (Figure 4).Subordinate to prominent Palaeozoic zircon fractions occur in the Taurides, Anatolides, Pontides, Cycladic Complex and Cyprus Island.The provenance of Upper Palaeozoic zircons in some units (e.g. the Kyrenia Range of Cyprus) is preferentially explained by multiple recycling of siliciclastic sediments that are ultimately derived from the Paleotethyan suture zone to the west of Turkey (see Chen et al., 2022 for detailed discussion).Middle to Late Triassic zircons, yielded both super-and sub-chondritic εHf(t), forming significant age peaks in the Anatolides and Cycladic Complex units.A mixed derivation of continental margin arc to intra-plate (e.g.rift-related) settings are inferred previously (e.g.Chen et al., 2019Chen et al., , 2022;;Seman et al., 2017;Zlatkin et al., 2018).There are also pronounced Late Cretaceous zircon ages in the Pontides and Cyprus, which yielded both positive and negative εHf(t) (Figure 4).Volumetrically significant, penecontemporaneous magmatic arc units that are widely exposed in regions of southeastern Turkey and central Pontides have possibly supplied most of the related zircon grains (e.g.Akdoğan et al., 2019;Chen et al., 2022).The younger grains were mainly reported from the Pontides and Cyprus (Figures 3  and 4).These zircons were probably derived from evolved, post-collisional volcanic products (e.g.Chen et al., 2022).

| Possible use of related metadata
U-Pb ages of detrital zircons can be used to infer maximum depositional ages of strata based on the youngest single grain age (YSG) or the youngest 1 grain cluster [YC1σ(2+)] etc, which is independent of biostratigraphy (Dickinson & Gehrels, 2009).These data can be compared with the magmatic, metamorphic and/or hydrothermal history of possible source regions and aid the interpretation of magmatic volumes, zircon fertility, erosional history and sediment source-to-sink relationships in provenance analysis in the Eastern Mediterranean Tethyan region.In addition, related metadata can be quantitatively compared by using multidimensional scaling (MDS; Vermeesch, 2013) or K-S D values, Kuiper V values (e.g.Saylor & Sundell, 2016) to visually display inter-sample dissimilarity and, therefore, helps the interpretation of related tectonics in continental-scale or high-resolution correlation.Figure 5a shows the array of Triassic lithologies of tectonic units considered in this study.The associated Shepard plot (Figure 5b), a scatterplot of distances between points in the MDS plotted against the observed dissimilarities, shows a relatively good correlation, implying that the MDS plot is meaningful.

| CONCLUSIONS
This explanatory paper belongs to part of the One Sediment section of the DDE programme, with a focus on the detrital zircon database compilation for Turkey, Cyprus and Greek peninsula regions.This study presents a detailed, systematic description of the information about the raw data of detrital zircon U-Pb geochronological age populations and related in-situ Lu-Hf isotopes, together with their possible use in the fields of sedimentary provenance interpretation and inter-sample 'bigdata' comparisons etc.All of these data are expected to be helpful for those studying the provenance and evolution of different crustal blocks in this tectonically complex region.

F
Locations of detrital zircon samples in the Turkey, Cyprus and Greek peninsula regions.
Example of a detrital zircon data file containing a header followed by the standard of Deep-Time Digital Earth (DDE); see https://doi.org/10.12297/dpr.dde.202210.3 for a full description of the format.

F
Cumulative distribution function and Kernel density estimation plots and pie diagrams for detrital zircon U-Pb ages compiled from Turkey, Cyprus and Greek peninsula (concordant ages only).
The scatter of compositions in is significant.It is noteworthy that zircons from the Cycladic Complex, Taurides, Cyprus and External Hellenides samples plot on one side of the diagram, while the Pontides and Anatolides plot on the other side of the diagram, indicating a real difference between their sources.A possible explanation is that the Triassic detritus were preferentially related to the development of Paleotethys to the north or Neotethys to the south (e.g.Robertson et al., 2012).Triassic sediments from Cyprus are slightly similar to those of the Taurides sediments but are most similar to the External Hellenides sediments.Triassic zircon populations from the Cycladic Complex are close to those from the Taurides as well as samples from the Pontides.Sediments from Pontides are not far distant from the Anatolides samples.Samples from the Anatolides bear no resemblance to sediments from the Taurides, Cyprus and External Hellenides.The variations of Triassic zircon populations of these units are probably related to the scarcity of dataset (e.g.Anatolides), or the microcontinent puzzle during the geological evolution of Tethys (Robertson & Dixon, 1984).
This work was financially supported by the National Natural Science Foundation of China (42002126, 42050102 and 41888101) and the Deep-Time Digital Earth (DDE) Big Science Program.We are very grateful to Alastair H. F. Robertson, Osman Parlak, Xiumian Hu and Jianghai Yang for helpful discussion.The manuscript benefitted from comments by Timur Ustaömer and an anonymous reviewer.

F
I G U R E 5 (a) Three-dimension MDS diagram of the Triassic sedimentary rocks compiled in this work.Solid and dashed lines represent the closest and second closest neighbours, respectively.MDS based on the K-S test D value (Saylor et al., 2018).(b) Associated Shepherd plot, showing a relatively good correlation of the samples compiled.

Major geographic-geologic units U-Pb sample no. U-Pb data Lu-Hf sample no. Lu-Hf data
T A B L E 2 Statistical data of detrital zircon dataset of Turkey, Cyprus and Greek peninsula.