Diagenetic history of the proterozoic carbonates and its role in the oil field development in the Baikit Anteclise, Southwestern Siberia

Kseniia Y. Vasileva, Victoria B. Ershova, Andrey K. Khudoley, Rustam R. Khusnitdinov, Anton B. Kuznetsov, Vsevolod Y. Prokofiev, Andrey Bekker

Journal «Elsevier»

Abstract

The Meso- to Neoproterozoic Kamo Group and Ediacaran carbonate rocks of the Baikit Anteclise, southwestern Siberian platform, Russia, were studied to reconstruct the history of development of the reservoir rocks and oil field. The Kamo Group is composed of 3.5 to 4 km thick dolostone and, rarely, limestone succession that was deformed before the Ediacaran time. Post-depositional processes played the key role in forming the reservoir properties of the Kamo Group. During the stage of deposition and subsidence (1500–720 Ma) silicification, cementation, and recrystallization caused development of a dense and low-permeability matrix. Pronounced recrystallization led to changes in isotopic and geochemical characteristics of the primary sediments, including increase in Mn (up to 0.093%) and Fe (up to 3.11%) contents and 87Sr/86Sr ratios (up to 0.7239), decrease in Sr concentrations (down to 11 ppm), and the development of flat REE-normalized patterns. Folding and uplift in the Baikit basin began about 720 Ma ago and caused fracturing and subsequent healing with vein dolomite and calcite precipitated from hot (70–130 °C) and highly saline (up to 28.7 wt%) fluids.

Geochemical (e.g. PAAS-normalized patterns of REE) and isotopic (87Sr/86Sr, δ18O, and δ13C) signatures of host dolostones and crosscutting dolomite veins are very similar suggesting that dolomites within the veins formed through dissolution of the host rocks. Uplift caused subaerial erosion, intense dissolution, and kar-stification, which penetrated down to 200–300 m below the surface. Folding, uplift, and peneplenization were important for porosity and permeability development in the dolostones of the Kamo Group. The cap rocks were subsequently formed during the Ediacaran and Paleozoic sedimentation cycle.

The oil field developed in the Paleozoic. Oil produced from the source rocks of the Madra, Vedreshev, and Iremeken formations of the Kamo Group was dissipated during the uplift and erosion before the Ediacaran sedimentation. After deposition of the Ediacaran and Cambrian strata, source rocks of the Iremeken Formation might have released oil when they passed the oil window, but most of oil in the Kuyumba field was derived from younger Ediacaran source rocks and migrated through fault network from the flanks (the Kureika and Cis-Sayan-Yenisey syneclises) into the reservoir of the Baikit Anteclise that was a topographic high at that time.

Keywords:

Siberian platform, Baikit Anteclise, Precambrian, Diagenetic history, Post-depositional alterations, Petroleum systems

1. Introduction

Proterozoic petroleum systems attracted growing interest in the past decade as they have been recognized as potentially large and untapped resources of oil and gas all over the world. Proterozoic oil and gas fields are now described from China (Wang et al., 2017; Feng et al., 2017), Russia (Frolov et al., 2015), Oman (Grantham, 1986), West Africa, North America, and Australia (Craig et al., 2013). In Russia, geological studies in Western Siberia highlighted petroleum potential of the Pro- terozoic sedimentary basin and stimulated detailed investigation of reservoir rocks and oil and gas potential (Frolov et al., 2015). The Kuyumba oil field within the Baikit Anteclise, located in the southwestern part of the Siberian platform, is thought to be the largest oil- and gas-bearing reservoir hosted in the Proterozoic strata of southern Siberia (Khabarov and Varaksina, 2011). Carbonate reservoir rocks of the Meso- to Neoproterozoic Kamo Group are characterized by highly heterogeneous and laterally variable porosity and permeability (Kontorovich et al., 1996).

Many previous studies of the Kuyumba area focused on the strati-graphy of the Meso- to Neoproterozoic oil-bearing strata (e.g., Shenfil and Primachok, 1996; Khabarov et al., 2002b; Melnikov, 2005), de- positional environments (Kraevsky et al., 1997; Khabarov et al., 2002b; Varaksina and Khabarov, 2000; Postnikova et al., 2008), stromatolite buildups (Varaksina and Khabarov, 2000), or broader questions re- garding oil and gas generation and migration (Kontorovich et al., 1996; Bazhenova et al., 2011; Kharahinov et al., 2011). However, very few studies discussed diagenesis (Varaksina, 2006; Korobov and Korobova, 2008; Bagrintzeva et al., 2015) and geochemistry (Vinogradov et al., 1998) of the Precambrian strata of the Baikit Anteclise. The lack of thorough understanding of the diagenetic history led to misinterpreta- tion of processes that controlled porosity and permeability in the stu- died area. The aim of this study is thus to reconstruct processes involved in the oil field development, specifically the diagenetic history of the carbonate rocks of the Kamo Group and Ediacaran succession and its connection to the tectonic evolution of the Baikit Anteclise basin and the timing of oil and gas generation and migration into the reservoir.

2. Geological setting

The study area is located within the Baikit Anteclise, along the southwestern margin of the Siberian platform (Fig. 1). The Baikit Anteclise is slightly elongated towards the northwest. The studied stratigraphic interval is divided into two major successions: i) the Kamo Group of the Mesoproterozoic to Neoproterozoic age that overlies the Archean-Proterozoic basement with an angular unconformity, and ii) the Ediacaran-Paleozoic sedimentary cover, which overlies the Kamo Group with an angular unconformity (Fig. 2).

The Kamo Group contains carbonate and terrigenous (argillite and sandstone) sedimentary rocks up to 4 km in thickness, and is divided into 12 formations based on abundance of carbonate and shale (Melnikov, 2005; Fig. 3). The age of and relationships among strati- graphic units are problematic, due to structural complications and the absence of a full stratigraphic section in any single well. Our study uses the Kamo Group stratigraphic scheme proposed by Khabarov and Varaksina (2011) and Kharahinov and Shlenkin (2011). Stratigraphic units and their boundaries are largely based on lithostratigraphy and petrophysical properties of the studied strata. For key wells, C and Sr isotope chemostratigraphy was also studied (Khabarov et al., 2002a,b), providing indirect age constraints for the formations of the Kamo Group. Correlation with other wells was carried out based on traceable seismic horizons R2, R3, and R4 (Supplementary material Fig. 1). Fur- ther details on the tectonic structure and evolution are discussed in Moskalenko and Khusnitdinov (2017).

The stratigraphic sequence (Fig. 3) of the Kamo Group begins with the Zelendukon Formation, composed of quartz and arkose sandstones, conglomerates, and siltstones. The overlying Vedreshev and Madra formations are represented by argillites, siltstones, clay-rich dolostones, and limestones. Carbonate rocks of the Jurubchen Formation include stromatolitic and peloidal dolostones interbedded with quartz sand- stones and sandy dolostones. The overlying Dolgokta Formation records a pulse of terrigenous material into the basin and is represented by argillites and siltstones, with layers of dolostone at the top and silici- clastic sandstone at the base. The overlying Kuyumba Formation re- presents a return to carbonate deposition, comprising stromatolitic, pisolitic, and peloidal dolostones, with occasional limestones and rare layers of siltstones and argillites, while the Kopchera Formation in- cludes argillites and dolostones. The Jukten, Rassolka, and Vingold formations are composed mainly of stromatolitic, pisolitic, peloidal, and oolitic dolostones, with layers of siliciclastic rocks. The youngest formations of the Kamo Group, the Tokura and Iremeken formations, are composed of argillites interbedded with stromatolitic and clay-rich dolostones.

The Mesoproterozoic to Neoproterozoic strata of the Kamo Group were predominantly deposited in shallow-marine environments. The oldest Zelendukon Formation represents sedimentation in alluvial to coastal-marine environments during initiation of the sedimentary basin over the Archean to Proterozoic basement rocks (Khabarov et al., 2002b), later succeeded by deposition in a broad epicontinental sea, where predominantly carbonate sediments were deposited, interspersed with brief terrigenous pulses during marine regressions within the basin leading to exposure (Postnikova et al., 2008; Khabarov and Varaksina, 2011; Bagrintzeva et al., 2015). Carbonate sedimentation occurred during several sedimentary cycles. The beginning of each cycle is marked by sandy dolostones or sandstones deposited during marine transgression in the basin, while the cycles are occasionally capped by karstification, beds with desiccation cracks, and unconformities, marking periods of subaerial exposure and erosion between sedimen- tary cycles.

Age constraints for the Kamo Group and its correlation with sedi- mentary successions in other basins are debatable. Subalkaline dolerite sills hosted in the Zelendukon Formation yielded 40Ar-39Ar date of 1499 ± 43 Ma suggesting that deposition of the Kamo Group com- menced earlier than 1500–1550 Ma (Khabarov et al., 2002b). Based on C and Sr isotope chemostratigraphy of carbonate rocks from the Baikit Anteclise, Khabarov and Varaksina (2011) inferred that the Zelendukon to Vingolda formations are Mesoproterozoic in age, while the Tokura and Iremeken formations are probably Mesoproterozoic to Neoproter- ozoic in age. These age constraints are broadly consistent with recent Rb-Sr dates for glauconite from the Dolgokta Formation which evi- denced the age of the Dolgokta sediments is older than 1340–1400 Ma (Zaitseva et al., 2019) and diverse microfossil assemblage (including Tappania, restricted to ca. 1.4–1.6 Ga time interval) from the Jurubchen Formation (Nagovitsin, 2009). The Kamo Group is generally gently folded, although locally dip angles abruptly increase up to 40–50°. Deformation marks cessation in deposition of the Kamo Group; folding was likely related to the late Neoproterozoic tectonic events in the adjacent Yenisey Ridge fold-and-thrust belt that occurred over 800–630 Ma time interval (Vernikovsky et al., 2004; Vernikovsky et al., 2009). Therefore, available age constraints can only bracket the max- imum duration for deposition of the Kamo Group to a period of 600–900 million years, which is obviously unrealistically long. De- position of the Kamo Group was however punctuated by multiple per- iods of subaerial exposure, non-deposition, and erosion in the basin, resulting in angular unconformities and hiatuses, the duration of which is not possible to estimate.

Ediacaran sediments unconformably overlie various stratigraphic units of the Kamo Group, ranging from the Iremeken to Madra forma- tions (Fig. 2). The well-studied Ediacaran succession is undeformed and flat-lying, and includes the following five formations (Melnikov, 2005) from the base to the top:

• Vanavara Formation: conglomerates, breccia, sandstones, siltstones, and rarely argillites;

• Oskoba Formation: anhydrites, dolostones, argillites, siltstones, and sandstones;

• Katanga Formation: dolostones, anhydrites, argillites, and marls;

• Sobin Formation: anhydrite and silty dolostones with pyrite and chert pebbles;

• Tetera Formation: dolostones with anhydrite.

The Ediacaran succession forms a transgressive sequence, starting with coarse continental siliciclastic deposits of the Vanavara Formation that underlie a shallow-marine, carbonate and sulfate evaporite de- posits of evaporite lagoon (Postnikova et al., 2008). The Ediacaran succession is overlain by the Cambrian to Triassic sediments that are up to 3.5 km in total thickness (Alekseenko et al., 2010). The thickness of the Paleozoic to Mesozoic succession increases gradually from the central part of the Baikit Anteclise towards its flanks, suggesting that the center of the anteclise formed a topographic high during deposition of these sedimentary units.

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3. Materials and methods

Petrographic and cathodoluminescence studies were carried out on 180 Mesoproterozoic to Ediacaran samples (see Supplementary mate- rial Fig. 1) collected from 14 wells drilled in the Baikit Anteclise area; core descriptions with the total length of 2600 m were used to provide the geologic framework. The studied samples represent all carbonate formations of the Kamo Group with the exception of the Vedreshev, Tokura, and Iremeken formations, and all Ediacaran formations.

Standard petrographic study (optical microscopy with transmitted light) was carried out on an Olympus BX-53 microscope. A cold cath- odoluminescence (CL) apparatus CITL model Mk5-2 (Cambridge Instrument Technology Ltd., Cambridge, UK) was used in automatic regime at 6 to 14 kV, 354 µA, and residual vacuum of 0.003 mBar.

To evaluate the chemical and isotopic difference between dolomite infilling fractures (vein dolomite) and dolomite forming the strata hosting the fractures (dolostone), 16 bulk-rock powders from vein do- lomites and dolostones were microdrilled. These bulk-rock powders were subjected to geochemical and isotopic analyses to measure con- centrations of major, trace, and rare-earth elements, along with carbon, oxygen, and strontium isotope ratios. In the tables and diagrams for the dolostone samples we used sample number, and for vein dolomites sample numbers are augmented with the letter “c.”

Major, trace, and rare-earth element concentrations were de- termined in carbonate component. After sample dissolution in 1 N HCl, concentrations of Ca, Mg, Mn, Sr, and Fe were measured by the atomic emission spectroscopy using Thermo Electron Iris Intrepid II ICP-AES; trace and rare-earth elements were measured by ELAN-DRC-6100 ICP- MS at the A.P. Karpinsky Russian Geological Research Institute in St. Petersburg. REE concentrations were normalized to Post-Archean Australian Shale (PAAS, Taylor and McLennan, 1985).

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Carbon and oxygen isotope analyses on carbonates were performed at the Stable Isotopes for Innovative Research (SIFIR) Laboratory in the University of Manitoba, according to the method described by Partin et al. (2014) and Ossa Ossa et al. (2018). Carbonates were microdrilled with 1 mm in diameter diamond drill bits from the dolomite veins and the least altered (i.e., lacking veins, discoloration, weathering rinds, and silicification) and fine-grained portions of polished thick sections. Carbonate powders were reacted at 70 °C with anhydrous phosphoric acid using a GasBenchII carbonate device and delivered in a stream of high-purity He to a Thermo Finnigan™ Delta V Plus Isotope-Ratio Mass- Spectrometer via an open-split interface (ConFlo IV, Thermo Fin- nigan™).

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For microthermometric measurements, cleavage fragments were studied using a Lincam THMSG-600 heating–cooling stage connected with Olympus microscope, video camera, and computer (Laboratory of Ore Field Geology, IGEM RAS, Moscow). This equipment allows de- tection of phase transformations in the −196° to 600 °C temperature range. Salinity of liquids was estimated using temperature of ice melting according to Kogan et al. (1961) and Bodnar and Vityk (1994). Salt concentration, liquid density, and pressure correction for tem- perature were obtained using the “FLINCOR” program (Brown, 1989). Salt composition of aqueous solution in fluid inclusions was estimated from the eutectic temperature (Teut; Borisenko, 1977).

4. Results

4.1. Petrographic and cathodoluminescence data

4.1.1. Carbonate lithologies of the Kamo Group

Several types of carbonates were observed within the studied suc- cession:

– Crystalline dolostones (Fig. 4a, b) without observable sedimentary structures are the most common lithology within the studied samples. This lithology was found in all investigated formations, except for the Zelendukon Formation. Dolostones are composed of idiotopic, sub- hedral, non-equigranular dolomite crystals 10 to 100 µm in size. Cathodoluminescence microscopy reveals that dolomite crystals show azonal, slightly heterogeneous red to dark-red cathodoluminescence;

– Stromatolitic dolostones (Fig. 4c, d, 5c) are found in the Jurubchen, Dolgokta, and Vingold formations. Individual dolostone layers consist of cryptocrystalline dolomite that shows dark-red cath- odoluminescence;

– Peloidal dolostones rarely occur (Fig. 4e, f); they are found in the Jurubchen, Dolgokta, Vingold, and Jukten formations. Typically, up to 80% (by volume) of this lithology consists of carbonate micritic peloids larger than 200 µm in size, characterized by bright to dark- red CL-colors (Pel on Fig. 5b) and by zonation. The space between peloids has been subsequently filled by dolomite cement, displaying zoned red to dark-red CL colors (Cem on Fig. 5b);

– Partially dolomitized limestones (Fig. 4g, h) occur in the Madra, Jurubchen, and Dolgokta formations. They are composed of micritic to microsparitic calcite matrix with up to 30% of silty to sandy quartz grains and up to 20% of dolomite. Some dolomitized lime- stones contain peloids or intraclasts up to 0.3 mm in diameter.

– Sandstones with dolomite cement or sandy (silty) dolostones (Fig. 4i, j), having > 5% of quartz grains by volume, are found in the Jurubchen, Dolgokta, Kuyumba, Kopchera, and Jukten forma- tions. Quartz grains are often corroded.

4.1.2. Diagenetic features of the Kamo Group

Petrographic and CL study revealed that the Meso- to Neoproterozoic carbonates have undergone a complex diagenetic his- tory. Diagenetic processes include recrystallization, dolomitization, compaction, stylolitization, cementation, silicification, fracturing, and fracture infilling. The detailed description of each of these processes is given in the following sections.

4.1.2.1. Recrystallization.

Crystalline dolostones are composed of crystals up to 200 μm in size, but on average they are 50 to 70 μm in size and larger than the maximum size of early diagenetic, sabkha- related dolomite (20 μm) and consistent with crystal size of deeply buried dolomite (< 10 to 100 μm; cf. Al-Alasm and Packard, 2000); size of dolomite crystals does not correlate with depth. Crystals of crystalline dolostones have irregular shape with curvy boundaries forming compacted mosaic fabric and showing homogeneous luminescence (Fig. 4a, b).

4.1.2.2. Cementation.

Cementation is most pronounced in the peloidal dolomite grainstones and sandy dolostones (Fig. 5a, b). Space between peloids is filled with subhedral dolomite crystals having straight boundaries (50–100 µm in size) and showing zoned red and dark-red CL colors. Cemented dolostones did not undergo advanced recrystallization since peloids are still micritic and zonation in dolomitic cement is not disturbed.

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4.1.2.3. Dolomitization.

The Kamo Group is mostly composed of dolostones, but rarely, in the Madra, Jurubchen, and Dolgokta formations, limestones can be found (e.g., in the borehole N1). Limestones have undergone partial dolomitization. Dolomite crystals up to 100 µm in size are idiotopic, porphyrotopic, or euhedral, displaying zonal or azonal bright (red to orange) CL colors (Fig. 5c).

4.1.2.4. Stylolitization.

Stylolites include horse-tail (wispy seams), wavy, and rectangular types (cf. Alsharhan and Sadd, 2000). These types of stylolites are irregularly distributed throughout the strata. The wavy and rectangular stylolites usually show amplitude up to 1 cm; increase in stylolite amplitude with depth was not observed. Stylolites are most abundant in the Jurubchen, Kuyumba, and Vingold formations. Stylolites are usually parallel to the bedding (Fig. 5d).

4.1.2.5. Silicification.

Silicification affected different rock types. In stromatolitic dolostones, chert replaced stromatolitic lamina with retention of primary sedimentary textures (Fig. 5e). In other cases, chert (sometimes fibrous) and quartz filled pores and fractures within different rock types (Fig. 5f, g). Chert is non-luminescent.

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4.1.2.6. Fracturing and fracture infilling.

The Meso- to Neoproterozoic carbonates of the Kamo Group are frequently fractured. Fractures are 2–7 mm in width with smooth borders; bulges up to 1–2 cm in width are common. Fractures are filled with calcite and dolomite. Several carbonate generations infilling fractures are recognized:

– D1 is xenotopic, anhedral (“saddle”) dolomite (Fig. 6a and b), having crystals up to several mm in size with undulose extinction and curved boundaries;

– D2 is the main fracture-filling phase, forming the bulk of vein dolomite; crystal size ranges from 200 µm to few mm. Under cath- odoluminoscope, crystals are bright to dull and include multiple thin zones with red to almost black colors. The boundaries between zones might be planar or non-planar (Fig. 6a and b) due to corro- sion. In some cases, hematite crystals are observed on cleavage surfaces;

– D3 is idiotopic to subhedral dolomite, occasionally with cloudy crystals up to 1–2 mm in size; dolomite is dull dark-red to black and green under cathodoluminescence (Fig. 6c and d).

– D4 makes rhombohedral to subhedral dolomite crystals larger than 100 µm in size that fill fractures; it is invisible in transmitted light, but apparent under cathodoluminescence (Fig. 6e and f). Crystals are transparent and up to 100 µm in size; they are characterized by yellow and dark-red CL colors with few thin zones;

– vein calcite was observed only in dolomitized limestones. Calcite crystals are slightly elongated, up to 0.5 mm in size, and have azonal or heterogeneous CL colors from orange to brown-orange (Fig. 6g and h).

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4.1.2.7. Dissolution and karstification.

Dissolution resulted in a series of vugs and voids within all carbonate units below the unconformity between the Kamo Group and the Ediacaran strata (Fig. 5h). Vugs are up to several centimeters in size; they usually have an irregular shape and are occasionally filled with greenish-grey clay, chert, or anhydrite.

4.1.3. Brief lithologic description of the Ediacaran strata

Carbonate rocks of the Ediacaran succession (Fig. 7) are composed of crypto- to fine-crystalline, idiotopic dolomite crystals up to 30 µm in size. Rarely, closely spaced laminations were observed; laminae are up to 1 mm in thickness and marked by clay seams. Strata contain up to 50% of gypsum or anhydrite with crystals size up to few mm and up to 5% of quartz grains with silt size. Dolomite is either zoned (dark-red cores with orange rims) or lacks zonation and has red to orange color under cathodoluminescence, while gypsum and anhydrite are non-lu- minescent (Fig. 7b, d).

4.1.4. Diagenetic features of the Ediacaran succession

Post-depositional alteration of the Ediacaran carbonates includes:

a) Infilling of pores (up to 200 µm in size) with secondary dolomite (Fig. 8a). Crystals of secondary dolomite are up to 100 µm in size and show yellow to dark-red CL colors similar to those of matrix.

b) Compaction resulting in stylolitization (stylolites with amplitude up to 1 cm; Fig. 8b) and transition of gypsum to anhydrite.

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4.1.5. Distribution of post-depositional alteration in stratigraphic units

Detailed petrographic and cathodoluminescence studies constrained how post-depositional alteration distributed across stratigraphical units and among lithologies (Table 1).Table 1 shows difference in post-de- positional alteration between strata of the Kamo Group and Ediacaran complex: the dolostones and limestones of the Kamo Group have un- dergone complex, post-depositional alteration including recrystalliza- tion, silicification, cementation, dolomitization, fracturing, healing fractures with vein minerals, and stylolitization, while the Ediacaran rocks were affected only by cementation and stylolitization.

For the carbonate rocks of the Kamo Group, Table 1 reveals that all units and lithologies were affected by some type of alteration – stylo- litization, fracturing, fluid circulation with precipitation in fractures, and karstification; other types of alteration are restricted to specific lithologies: e.g., early silicification (commonly observed in stromato- litic dolostones), cementation (observed in peloidal dolostones and sandstones), and partial dolomitization (observed in limestones). Vein calcite is restricted to limestones, while vein dolomite appears only in dolostones, saddle dolomite D1 develops in the Kuyumba and Jur- ubchen formations, while dolomites with idiotopic crystals (D1-D3) were observed in all studied dolostones of the Kamo Group regardless of their lithologies and stratigraphical position.

4.1.6. Paragenetic sequence

In all studied sections, the earliest post-sedimentary alteration is silicification in stromatolitic dolostones, cementation in peloidal do- lostones, dolomitization in limestones as well as stylolitization and re- crystallization. The relative timing of these alteration processes is un- known as they appear in different lithologies and formations. But it is clear that all these changes occurred before fracturing and healing of the fractures. Silica bands in stromatolitic dolostones, dolomite crystals in dolomitized limestones, cemented areas, and stylolites are crosscut by fracture-filling carbonates (Fig. 9a–d). Vein dolomite often encloses recrystallized host dolostone (Fig. 9e); therefore recrystallization clearly predated fracturing and infilling.

There are 4 types of dolomites infilling fractures; most common are D2, D3, and D4 (e.g., Fig. 9). These dolomites infilling fractures were developed in all carbonate formations after their deposition. Further- more, the veins are truncated by the overlying Ediacaran sedimentary rocks and do not pass into the Ediacaran strata, indicating that the fractures and vein carbonates had been formed before the Ediacaran sediments were deposited. The temporal relationship of the D1 to D3 vein carbonates was determined based on their spatial distribution and cross-cutting relationships. The D1 vein carbonates precipitated before the D2 carbonates, as the D2 carbonates have restricted distribution and only fill voids left after the D1 dolomite partially infilled fractures (Fig. 6a). The D4 carbonates fill fractures, which crosscut other sets of fractures infilled with the D2 and D3 dolomites, and, therefore, must be younger (Fig. 9f). It is not possible to constrain the relative timing of precipitation of the D2 and D3 carbonates with respect to each other. The second phase of silicification took place after pores and fractures were infilled with the D2 dolomite (Fig. 5g). Karst is developed in dolostones of different stratigraphic units di- rectly below the pre-Ediacaran unconformity. Vugs are developed only in the Kamo Group carbonates and are not found in carbonates of the overlying Ediacaran succession, implying that they were formed by dissolution related to subaerial exposure before the overlying Ediacaran sediments were deposited. Some of the vugs were subsequently filled with clay minerals, chert, and anhydrite. Paragenetic sequence among diagenetic phases in the overlying Ediacaran succession is unclear.

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4.2. Geochemistry

4.2.1. Major and trace elements

Major element concentration data (Supplementary materials Table 2) show that most of the host and vein carbonates, except for N1- 18 and N1-18c, are dolomites with Ca/Mg molar ratio of 1.0 to 1.1 (all samples are crystalline dolostones). Sample N1-18 is a partially dolo- mitized limestone and N1-18c vein carbonate is a high-Mg calcite. In- soluble residue of dolostones varies from 0.9 to 10.8%. One dolostone (sample N9a-2) and one limestone (sample N1-18) contain up to 62.3 and 46.1% of clay and sand admixture, respectively. Vein carbonates have less than 2.4% of siliciclastic material, and only one dolomite vein (sample N2-36c) contains 12.7% of quartz.

Six analyzed dolostone samples have low Sr concentrations of 11 to 51 ppm, with one clay-rich dolostone having higher value of 190 ppm. Partially dolomitized limestone (sample N1-18) and high-Mg calcite (sample N2-36c) have higher Sr contents, 291 and 436 ppm, respec- tively. Mn and Fe contents are typically higher in vein dolomites than in host dolostones, and Mn content correlates positively with Fe content (r2 = 0.99 for host dolostone; Fig. 10a). Mn and Fe concentrations in the dolostones also positively correlate with insoluble residue (r2 = 0.96 and 0.97, respectively, for host dolostones; Fig. 10b and c).

4.2.2. Rare earth elements

Almost all REE patterns normalized to PAAS (Fig. 11) show a slight depletion in Heavy Rare Earth Elements (HREE). To calculate Eu (EuSN/ EuSN*), Pr (PrSN/PrSN*), and Ce (CeSN/CeSN*) anomalies we used equations given in Bau and Dulski (1997). Concentration of REE cor- relates with insoluble residue content (r2 = 0.99 for host dolostones, r2 = 0.3 for vein dolomites; Fig. 10d).

Dolomitized limestone (sample N1-18, Fig. 11) shows slightly po- sitive Eu anomaly. Two samples of silty dolostone (N4-37 and N4-40) have negative Ce anomalies. Sample of silty dolostone (N9a-12) and several dolostone samples (e.g., N4-40) show MREE-bulge. Other do- lostone samples show almost flat REE patterns. Shape of the PAAS-normalized REE patterns of vein dolomites and high-Mg calcite is

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similar to that of the patterns of host carbonates except for one sample of dolomite (N4-37; Fig. 11) that shows a bell shape. Y/Ho ratios for host dolostones range from 30 to 50 and for vein dolomites from 31 to 48; for dolomitic limestone Y/Ho ratio is 38 and for vein calcite it is 33.

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4.3. Isotopic data

4.3.1. Oxygen and carbon isotope values

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4.3.2. Strontium isotopes

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4.4. Fluid inclusion data

Petrographic study of fluid inclusions in dolomite (Fig. 13) allowed to classify them as (1) two-phase gas–liquid inclusions of brine (Fig. 13a), and (2) two-phase gas–liquid inclusions of hydrocarbons. Fluid inclusions often have shapes of a negative crystal or a rectangular (Fig. 13 a); irregular shapes are also observed. Size of fluid inclusions varies from 1 to 18 μm. Seven samples of vein dolomites were selected for thermometric and cryometric study. All examined fluid inclusions are primary or pseudosecondary (fluid inclusions types are after Bodnar, 2003). Results are given in Table 3 and Fig. 13b. The fluid inclusions fall into two groups:

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1. Most of the two-phase inclusions are highly saline Ca- and Na- chloride brines with teut from −56 to −65 °C. Temperature of homogenization of these fluid inclusions ranges from 70 to 121 °C, while ice-melting temperature varies from −14.3 to −49.9 °C. Estimated salt concentration for the system H2O – CaCl2 is from 17.3 to 28.7 wt% CaCl2 equivalent, and the estimated density of the fluid is 1.08 to 1.18 g/cm3. Temperature of fluid capture estimated after correction for 270 bar pressure is 82 to 123 °C.

2. Two carbonate samples contain two-phase fluid inclusions of hy- drocarbons with large gas bubbles; these fluid inclusions homo- genize at 79 to 94 °C into a liquid phase.

Almost all studied fluid inclusions were in the D4 vein dolomite and only few fluid inclusions were found in the D2 vein dolomites. Frequency distribution of homogenization temperature (Fig. 13b) re- veals that the majority of the two-phase inclusions formed at a tem- perature of 95 to 110 °C.

5. Discussion

5.1. Seawater signals and burial history of the Kamo Group

According to Khabarov and Varaksina (2011), deposition of the Kamo Group began at about 1500 Ma. Our geochemical data (Mn/Sr and 87Sr/86Sr ratios) show that none of the studied samples from the Kamo Group pass geochemical screens to be a proxy for seawater Sr isotope signal. All samples of crystalline dolostones are characterized by Mn/Sr ratios exceeding 2 (only one sample of dolomitic limestone shows Mn/Sr = 0.3) that reflect some degree of diagenetic alteration

(Brand and Veiser, 1980; Banner and Hanson, 1992; Barnaby and Read, 1992). Only one dolostone sample (N8-13) from the Vingold Formation with the lowest content of siliciclastic component (0.9%) shows 87Sr/86Sr ratio (0.7056) that could reflect Sr isotope composition of the Mesoproterozoic to early Neoproterozoic seawater. The inferred sea- water Sr isotope ratios for the early to middle Mesoproterozoic (1600–1200 Ma) have a narrow range of 0.70456–0.70502, whereas those for the late Mesoproterozoic (1200–1000 Ma) and early Neoproterozoic (900–820 Ma) are higher, 0.70519–0.70611 (Kuznetsov et al., 2013, 2014, 2017; Khabarov and Varaksina, 2011).

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Two samples of dolostones (N4-37 and N4-40) show a true negative Ce anomaly ((Ce/Ce*)SN < 1 and (Pr/Pr*)SN > 1; cf. Bau and Dulski, 1997; Fig. 11), which reflects precipitation from oxic seawater with a pronounced negative Ce anomaly (Tlig and M’Rabet, 1985; Bekker et al., 2010; see Supplementary material Table 1). Although it is gen- erally accepted that mid-depth seawater of the Proterozoic oceans was anoxic or had low-oxygen content (Slack et al., 2007, 2009; Planavsky et al., 2011), negative Ce anomaly in Paleoproterozoic authigenic apatite (Joosu et al., 2015) and Mesoproterozoic and Neoproterozoic marine carbonates (e.g., Ling et al., 2013; Tostevin et al., 2016; Tang et al., 2016; Zhang et al., 2018), iodine content of marine carbonates (e.g., Hardisty et al., 2017), and nitrogen isotope values of shales (Kipp et al., 2018) point to the oxic state of shallow-marine coastal environ- ments since the late Paleoproterozoic. Our data supports this emerging view. The studied rocks of the Kamo Group have undergone insults by a range of diagenetic processes that obliterated primary geochemical properties although two samples seem to preserve primary signals (87Sr/86Sr value and true negative Ce anomaly).

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Previous studies have shown that the lowermost formations (Zelendukon, Vedreshev, and Madra formations) were buried more than 7 km below the surface (Vasileva et al., 2016). Subsidence of the Kamo Group had ceased with folding, uplift, and erosion. The late Neoproterozoic tectonic activity in the area of the Baikit Anteclise se- dimentary basin is linked to the orogenic event in the Yenisey Ridge area (Shein, 2006) that occurred between 800 and 630 myr (Vernikovsky et al., 2004; Vernikovsky et al., 2009). After a period of peneplenation, a broad, shallow-marine epicontinental basin developed in the study area during the Ediacaran, and the Kamo Group was buried beneath 2.5 to 3.5 km of the Ediacaran sediments. A detailed descrip- tion of diagenetic events and their relationship with regional tectonic events is given below.

5.1.1. Diagenetic processes related to deposition and subsidence of the Kamo Group

During the subsidence in the basin, silicification, dolomitization, cementation, recrystallization, and stylolitization affected the Kamo Group. All these processes proceeded fracturing and healing of fractures during folding and uplift. Diagenetic alteration related to deposition and subsidence affected different formations at different times, but produced similar diagenetic products (silicification of stromatolitic dolostones in the Vingold and Kuyumba formations; recrystallization and stylolitization in the Jurubchen, Kuyumba, Kopchera, Jukten, and Vingold formations).

Silicification affected stromatolitic dolostones during early diagen- esis, immediately after deposition. In the modern environments, de- position of protodolomite followed by silicification has been observed in ephemeral lakes associated with the Coorong Lagoon in southern Australia (Peterson and von der Borch, 1965). Previous studies have shown that solubility of amorphous silica and quartz is high under al- kaline conditions (pH > 8.2–9; Peterson and von der Borch, 1965; Bartholomé, 1966; Knauss and Wolery, 1988), whereas silica pre- cipitation occurs under neutral or acidic conditions (Peterson and von der Borch, 1965; Keheila and El-Ayyat, 1992). Dissolved silica con- centration in Proterozoic seawater is thought to have been high due to the absence of silica-secreting plankton (Siever, 1992).

Dolomite cementation and limestone dolomitization formed dolo- mite cement in dolostones and partially dolomitized limestones re- sulting in similar CL characteristics, which suggests similar chemical composition of dolomitizing fluids. The source of dolomitizing fluids was likely seawater circulating through the limestones, but the specific model (e.g., Machel, 2004; Flugel, 2010) applicable to the Kamo Group carbonates is not clear. Lithostatic pressure of the overlying sediments caused compaction, recrystallization, and stylolitization in the Kamo Group carbonates.

Stylolites are thought to start forming at burial depths ranging from 90 to 300 m (Alsharhan and Sadd, 2000). Within the studied succession, wispy seams and rectangular stylolites are found in drill cores within several decimeters of each other without any compositional contrast among host dolostones. It thus remains unclear what controlled dis- tribution of different stylolite types.

According to geochemical data, recrystallization greatly altered the primary carbonate rocks. Unrecrystallized dolostones maintained their

initial geochemical and isotopic characteristics reflecting the sedimentary environment in which they precipitated. There are several indicators of significant and, probably, multiple-stage recrystallization:

– size of dolomite crystals up to 200 µm (70–80 µm in average);

– low concentration of Sr (< 100 ppm in dolostones of the Kamo Group) with respect to high concentrations in modern and ancient well-preserved dolostones (500 to 800 ppm; Veizer, 1983; Land, 1985; Mazzullo, 1992; Montanez and Read, 1992; Machel, 1997; Kuznetsov et al., 2005, 2013, 2017);

– enrichment in radiogenic Sr that might be related to interaction of basinal fluids with siliciclastic material along their pathway (Banner, 1995; Vinogradov et al., 1998) or incorporation of radio- genic Sr locally derived from clay minerals into carbonate lattice when carbonates were recrystallized (Kuznetsov et al., 2005, 2017). The 87Sr/86Sr ratio in “rejuvenated” glauconites of the Dolgokta Formation is 0.7359 ± 0.0005 which finger out the Sr isotope ratio in late diagenetic fluid (Zaitseva et al., 2019). The basinal fluid potentially supplied the radiogenic 87Sr into late diagenetic dolo- mite generations during glauconite recrystallization. This connec- tion could support the temporal link to the late Mesoproterozoic regional stage of “rejuvenation” of Riphean glauconites in North Siberia (Olenek and Anabar Uplifts) about 1300–1250 Ma (Zaitseva et al., 2016, 2018).

– nearly stoichiometric for dolomite Ca/Mg ratios (1.0 to 1.1) that indicate multiple recrystallization events (Coniglio, 2003);

– Fe and Mn contents of the Kamo Group dolostones are similar to those of recrystallized dolostones in general (Veizer, 1983). These elements were added to the dolomite crystal lattice during re- crystallization in the presence of basinal fluids that have interacted at high temperature with sedimentary, terrigenous or igneous rocks along their pathway. This alteration style is common to diagenetic carbonates, where Fe and Mn are derived from pore fluids, silici- clastic material, diagenetic minerals, Fe-Mn oxides or oxyhydr- oxides, pyrite, or clay minerals (Veizer, 1983; Kuznetsov et al., 2005, 2017);

– PAAS-normalized REE patterns of the host rocks that are almost flat might reflect contamination with a siliciclastic component during recrystallization (Banner, 1995);

– Y/Ho ratios (30 to 50; Ave. = 38.1 for host dolostones and dolo- mitic limestone): although superhondritic, the lower end of this range is too low with respect to other Precambrian carbonates and iron formations (Nothdurft et al., 2004; Planavsky et al., 2010; Bekker et al., 2013; Ling et al., 2013; Tostevin et al., 2016; Tang et al., 2016; Zhang et al., 2018) and modern seawater ratio of 44–74 (Bau, 1996). Two samples with low insoluble residue content (N8- 13 and N2-21) show Y/Ho ratios close to that for the modern sea- water (50 and 48, respectively). Similarly low superchondritic ratios have been explained by deep basinal brines removing Y in associa- tion with dolomitization (Nothdurft et al., 2004; Franchi, 2018) or by terrigenous input to the depositional setting of sediments (Northdurft et al., 2004). In our case, the dolomitic limestone shows intermediate Y/Ho ratio, but lower than one of the analyzed crys- talline dolostones. We therefore infer that terrigenous input and contamination of the studied carbonate rocks during recrystalliza-tion is likely the most plausible explanation for low Y/Ho ratios in our study, consistent with high insoluble residue in our samples.

5.1.2. Post-depositional alteration related to folding, fracturing, and erosion in the Baikit Anteclise area

During the pre-Ediacaran period of folding, uplift, and peneplana- tion, Meso- to Neoproterozoic carbonate rocks of the Kamo Group were fractured and some of the fractures were healed with dolomite or cal- cite. Petrographic and CL characteristics of vein dolomite show that there are only four types of vein dolomite, suggesting that fracturing and healing affected all the studied formations of the Kamo Group on a regional scale, when folding and uplift happened. Additional petrographic data (abundant thin zones in dolomite crystals with irre- gular, corrosion-related boundaries and inclusions of hematite) provide evidence for tectonics-related fracturing when hot (70–121 °C), high- salinity brines (with salinity up to 28.7 wt% eq. based on cryometric data) circulated through the strata. Consistent with this interpretation, vein dolomites at Navan, Ireland and in the Central and Southern Appalachians were formed at temperature of 80 to 200 °C due to folding (Braithwaite and Rizzi, 1997; Moore, 2001).

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According to our petrographic data, the second stage of silicification took place after veins were filled with dolomite. Pustylnikov and Vakulenko (1997) reported temperature of homogenization 70 to 80 °C for two-phase inclusions in authigenic quartz and proposed that silica was released via corrosion of quartz grains, stylolitization, and dis- solution of clay minerals in the strata.

Uplift of the basin led to significant erosion, when intense near- surface karstification produced vugs and voids, which enhanced hy- drocarbon reservoir potential along with unhealed fractures (Kharahinov and Shlenkin, 2011). Karstified carbonate strata extend 200 to 300 m below the pre-Ediacaran unconformity, and the most karstified areas are associated with the highest density of fracture zones in the recrystallized Meso- to Neoproterozoic carbonate rocks that otherwise have low porosity (Postnikova et al., 2008).

5.1.3. Diagenesis related to deposition of the Ediacaran succession and subsidence

Post-depositional diagenesis of the Ediacaran succession includes healing fractures with dolomite, compaction, stylolitization, and transformation of gypsum to anhydrite. These post-depositional changes resulted in development of non-porous cap rocks. At the same time, some vugs within the upper part of the Kamo Group were filled with anhydrite and clay.

5.2. Development of the oil field

For the studied dolostones and dolomitized limestones of the Kamo Group, silicification, recrystallization, cementation, and stylolitization contributed to considerably reduce primary porosity and permeability (see the generalized schematic diagram for the oil field development on Fig. 14). Post-depositional alteration that led to the development of secondary porosity and permeability in the reservoir rocks was syn- chronous for all the studied stratigraphic units. The alteration includes fracturing and karstification that developed during the Baikit basin inversion and subsequent erosion before the Ediacaran strata were deposited. Deposition of the Ediacaran succession was accompanied by partial filling of vugs with clay and anhydrite that reduced pore space in the reservoir rocks. Accordingly, the reservoir and cap rocks were formed by the beginning of the Cambrian. By that time the Madra and Vedreshev formations that are composed of carbonaceous argillites were already overmatured (Vasileva et al., 2016) and thus could not have been the source rocks for oil. Carbonaceous claystones of the Ir- emeken Formation reached the oil window at that time and could have provided oil for the Kuyumba oil field as Frolov et al. (2015) proposed. However, organic geochemistry data of Kelly et al. (2011) suggest that oil in the Baikit Anteclise was derived from the Neoproterozoic strata (substantially younger than ca. 1050 Ma), while the minimum age of the Iremeken Formation is inferred to be ca. 1100 Ma (Kharahinov and Shlenkin, 2011). This indicates that the oil of the Kuyumba oil field most likely migrated through fault network from the adjacent Edia- caran basins (Cis-Sayan-Yenisey and Kureika syneclise), which by the end of the Ediacaran were at a lower elevation than the Baikit Anteclise (for details see Fig. 10 in Frolov et al., 2015) (Fig. 15).

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5.3. Conclusions

Post-depositional alteration played the key role during the devel- opment of the reservoir rocks of the Kuyumba oil field. The Meso- to Neoproterozoic dolostones and partially dolomitized limestones of the Kamo Group in the Baikit Anteclise sedimentary basin have undergone a complex diagenetic history due to both early, shallow and late, burial diagenesis, followed by folding and uplift. During deposition and sub- sidence of the Kamo Group, silicification, dolomitization, re- crystallization, and stylolitization resulted in development of non- porous matrix. Significant recrystallization led to changes in the pri- mary isotopic and geochemical characteristics of the carbonate rocks at the late Meso- to Neoproterozoic stage of regional alteration. Compression ended subsidence in the basin in the middle of the Neoproterozoic. In association with folding, fractures formed and some of them were healed with vein dolomite and calcite. Following folding and fracture generation and healing, the studied area experienced a period of peneplanation and weathering that resulted in extensive karstification and formation of vugs and voids in the subaerially ex- posed Meso- to Neoproterozoic Kamo Group carbonates. This stage of the Kamo Group diagenesis is important in the context of secondary porosity generation by fracturing, but all hydrocarbons generated at that time were lost due to the subsequent pre-Ediacaran erosion of impermeable cap rocks. Renewed subsidence and deposition then commenced during the Ediacaran, filling some of the open vugs and voids in the underlying karstified Kamo Group carbonates with anhy- drite and clay.

Oil formation and migration occurred on all stages in the Baikit Anteclise basin evolution, but oil generated from the Kamo Group was lost before the Ediacaran succession was deposited. The Madra, Vedreshev, and Iremeken formations of the Kamo Group were the source rocks at that time, but the all the oil generated during the Meso- to Neoproterozoic subsidence was lost during the subsequent uplift and erosion. Renewed oil generation from the Iremeken Formation pro- ceeded in the Paleozoic, although oil generated from the Iremeken Formation did not contribute much as most oil in the Kuyumba oil field likely migrated from the Ediacaran strata on the flanks of the Baikit Anteclise.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influ- ence the work reported in this paper.

Acknowledgments

Results of this investigation are published with the permission of Scientific-Technical Centre “Gazpromneft.” The project was partly sponsored by SPSU grant 3.38.137.2014. Participation of Andrey Bekker was funded by Natural Sciences and Engineering Research Council of Canada Discovery and Accelerations grants. The Sr isotope investigation was supported by RSF grant 18-17-00247 (A.B. Kuznetsov). We greatly appreciate careful edits and useful suggestions from our reviewers, Zunli Lu and anonymous reviewer, Associate Editor, Elson Oliveira, and Editor, Professor Wilson Teixeira.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.precamres.2020.105690.

References

Al-Alasm, I.S., Packard, J.J., 2000. Stabilization of early-formed dolomite: a tale of di- vergence from two Mississippian dolomites. Sed. Geol. 131, 97–108.

Alekseenko, V.D., Alyasev, V.A., Barmin, V.A., Belolipetskaya, L.I., Bozhko, V.V., Varganov, A.S., Egorov, V.N., Kazhaeva, O.D., Kachevskiy, L.K., Moskalev, V.A., Pevzner, V.S., Radyukevich, N.M., Rumyantsev, N.N., Suslova, S.V., Shor, G.M., 2010. In: State geological map of Russian Federation. Scale 1: 1000000 (third generation). Sheet R-46, Explanatory Notes. VSEGEI Publishing House, Saint Petersburg, pp. 470.

Alsharhan, A.S., Sadd, J.S., 2000. Stylolites in Lower Cretaceous carbonate reservoirs. U.A.E. SEPM Spec. Publ. 69, 185–207.

Bailey, T.R., McArthur, J.M., Prince, H., Thirlwall, M.F., 2000. Dissolution methods for strontium isotope stratigraphy: whole rock analysis. Chem. Geol. 167, 313–319.

Bagrintzeva, K.I., Krasilnikova, N.B., Sautkin, R.S., 2015. Conditions of formation and characteristics of Riphean carbonate reservoir rocks of Yurubcheno-Tokhoma de- posit. Geol. Oil Gas 1, 24–40 [in Russian].

Banner, J.L., 1995. Application of the trace element and isotope geochemistry of stron- tium to studies of carbonate diagenesis. Sedimentology 42, 805–824.

Banner, J.L., Hanson, G.N., 1992. Calculation of simultaneous isotopic and trace element variations during water-rock interaction with applications to carbonate diagenesis. Geochem. Cosmochim. Acta 54 (11), 3123–3137.

Barnaby, R.J., Read, J.F., 1992. Dolomitization of a carbonate platform during late burial: lower to Middle Cambrian Shady Dolomite, Virginia Appalachians. J. Sedim. Petrol. 62 (6), 1023–1043.

Bau, M., 1996. Controls on the fractionation of isovalent trace elements in magmatic and aqueous systems: evidence from Y/Ho, Zr/Hf, and lanthanide tetrad effect. Contrib. Mineral. Petrol. 123, 323–333.

Bau, M., Dulski, P., 1997. Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa. Precambr. Res. 79, 37–55.

Bartholomé, P., 1966. Corroded quartz grains in sedimentary ores of iron and manganese. Econ. Geol. 61, 886–896.

Bazhenova, T.K., Dakhnova, M.V., Mozhegova, S.V., 2011. Upper Proterozoic of Siberian platform – main source of oil-and-gas content of its pre-Mesosoic basin. Oil Gas Geol [In Russian].

Bekker, A., Slack, J.F., Planavsky, N., Krapez, B., Hofmann, A., Konhauser, K., Rouxel, O., 2010. Iron Formation: the sedimentary product of a Complex interplay among mantle, tectonic, oceanic, and biospheric processes. Econ. Geol. 105 (3), 467–508.

Bekker, A., Planavsky, N., Krapez, B., Rasmussen, B., Hofmann, A., Slack, J.F., Rouxel, O.J., Konhauser, K.O., 2013. Iron formations: their origins and implications for an- cient seawater chemistry. Treatise Geochem. Elsevier 9, 561–628.

Bodnar R.J., Vityk, M.O., 1994. Interpretation of microthermometric data for H2O–NaCl fluid inclusions. Fluid inclusions in minerals: methods and applications. Pontignano: Siena, 117–130.

Bodnar R.J., 2003. Introduction to fluid inclusions. In: Samson, I., Anderson, A., Marshall, D., (Eds.). Fluid Inclusions: Analysis and Interpretation. Mineral. Assoc. Canada, Short Course 32, 1–8.

Borisenko, A.S., 1977. Cryometric investigations of salt composition of gas-and-liquid inclusions. Geol. Geophys. 8, 16–27 [in Russian].

Braithwaite, C.J.R., Rizzi, G., 1997. The geometry and petrogenesis of hydrothermal dolomites at Navan, Ireland. Sedimentology 44, 421–440.

Brand, U., Veiser, J., 1980. Chemical diagenesis of a multicomponent system – 1: trace elements. J. Sediment. Petrol. 50, 4, 1219–1236.

Brown, P., 1989. FLINCOR: a computer program for the reduction and investigation of fluid inclusion data. Am. Mineral. 74, 1390–1393.

Coniglio, M., 2003. Dolomitization and recrystallization of middle Silurian reefs and platformal carbonates of the Guelph Formation, Michigan Basin, Southwestern Ontario. Bull. Can. Petrol. Geol. 51 (2), 177–199.

Craig, J., Biffi, U., Galimberti, R.F., Ghori, K.A.R., Gorter, J.D., Hakhoo, N., Le Heron, D.P., Thurow, J., Vecoli, M., 2013. The palaeobiology and geochemistry of Precambrian hydrocarbon source rocks. Mar. Pet. Geol. 40, 1–47.

Feng, M., Wu, P., Qiang, Z., Liu, X., Duan, Y., Xia, M., 2017. Hydrothermal dolomite reservoir in the Precambrian Dengying Formation of central Sichuan Basin, Southwestern China. Mar. Petrol. Geol. 82, 206–219.

Flugel, E., 2010. In: Microfacies of Carbonate Rocks. Analysis, Interpretation and Application, second ed. Springer-Verlag, Berlin Heiderberg, pp. 984.

Franchi, F., 2018. Petrographic and geochemical characterization of the Lower Transvaal Supergroup stromatolitic dolostones (Kanye Basin, Botswana). Precambr. Res. 310, 93–113.

Frolov, S.V., Akhmanov, G.G., Bakay, E.A., Lubnina, N.V., Korobova, N.I., Karnushina, E.E., Kozlova, E.V., 2015. Meso-Neoproterozoic petroleum systems of the Eastern Siberian sedimentary basins. Precambr. Res. 259, 95–113.

Grantham, P.J., 1986. The occurence of unusual C27 and C29 sterane predominance in two types of Oman crude oil. Org Geochem. 9, 1, 1–10.

Hardisty, D.S., Lu, Z., Bekker, A., Diamond, C.W., Gill, B.C., Jiang, G., Kah, L., Knoll, A.H., Loyd, S.J., Osburn, M.R., Planavsky, N.J., Wang, C., Zhou, X., Lyons, T.W., 2017. Perspectives on Proterozoic surface ocean redox from iodine contents in ancient and recent carbonate. Earth Planet. Sci. Lett. 463, 159–170.

Joosu, L., Lepland, A., Kirsimäe, K., Romashkin, A.E., Roberts, N.M.W., Martin, A.P., Črne, A.E., 2015. The REE-composition and petrography of apatite in 2 Ga Zaonega Formation, Russia: the environmental setting for phosphogenesis. Chem. Geol. 395, 88–107.

Keheila, E.A., El-Ayyat, A., 1992. Silicification and dolomitization of the Lower Eocene carbonates in the Eastern Desert between Sohag and Qena, Egypt. J. Afr. Earth Sci. 14 (3), 341–349.

Kelly, A.E., Love, G.D., Zumberge, J.E., Summons, R.E., 2011. Hydrocarbon biomarkers of Neoproterozoic to Lower Cambrian oils from eastern Siberia. Org Geochem. 42, 640–654.

Khabarov, E.M., Ponomarchuk, V.A., Morozova, I.P., 2002a. Strontium isotopic evidence for supercontinental breakup and formation in the Riphean: Western margin of the Siberian craton. Russ. J. Earth Sci. 4 (4), 259–269.

Khabarov E.M., Ponomarchuk V.A., Morozova I.P., Varaksina I.V., Saraev S.V., 2002. Sea Level Changes and δ13C trends in Riphean Petroliferous Deposits on the western Margin of the Siberian Craton (Baikit uplift). Geologia I Geophisica 43, 3, 211–239 [in Russian].

Khabarov, E.M., Varaksina, I.V., 2011. The structure and depositional environments of Mesoproterozoic petroliferous carbonate complexes in the western Siberian craton. Russ. Geol. Geophys. 52, 923–944.

Kharahinov, V.V., Shlenkin, S.I., 2011. Hydrocarbon Potential of Precambrian Strata of West Siberia in Terms of Kuyumba-Yurubchen-Tohomsk Area of Oil and Gas Depositing. Nauchnyi mir, Moskow [in Russian].

Kharahinov, V.V., Shlenkin, S.I., Zereninov, V.A., Ryabchenko, V.N., Zochshenko, N.A., 2011. Hydrocarbon potential of Precambrian strata of Kuyumba-Yurubcheno- Tokhomsk area of oil and gas depositing. Oil and gas geology. Theory and practice, 6, 1. http:.www.ngtp.ru/rub/4/12_2011.pdf [in Russian].

Kipp, M.A., Stukeen, E., Yun, M., Bekker, A., Buick, R., 2018. Pervasive aerobic nitrogen cycling in the surface ocean across the Paleoproterozoic Era. Earth Planet. Sci. Lett. 500, 117–126.

Knauss, K.G., Wolery, T.J., 1988. The dissolution kinetics of quartz as a function of pH and time at 70°C. Geochim. Cosmochim. Acta 52, 43–53.

Kogan, V.B., Friedman, V.M., Kafarov, V.V., 1961. Manual of solubility. Vol 1: Binary systems. Moscow-Leningrad, AS USSR Publishing, 970.

Kontorovich A.E., Izosimova A.N., Kontorovich A.A., Khabarov E.M., Timoshina I.D., 1996. Geological structure and conditions of the formation of the giant Yurubcheno- Tokhoma zone of oil and gas accumulation in the Upper Proterozoic of the Siberian Platform. Geologia I Geophisica, vol. 30, no. 11, 193–195 [in Russian].

Korobov, A.D., Korobova, A.A., 2008. Epigenetic changes of the Riphean-Vendian car- bonate formations and Permo-Triassic intrusions of Baikit Anteclise in connection with formation of fracture-cavernous reservoir. Geol. Oil Gas 1, 16–24 [in Russian].

Kraevsky B.G., Pustylnikov A.M., Kraevskaya M.K., 1997. Precambrian Formation of Reef Origin in the central Part of the Baikit Anteclise. Geologia I Geophisica, 10, 38, 193–195 [in Russian].

Kuznetsov, A.B., Krupenin, M.T., Ovchinnikova, G.V., Gorokhov, I.M., Maslov, A.V.,

Kaurova, O.K., Ellmies, R., 2005. Diagenesis of carbonate and siderite deposits of the Lower Riphean Bakal Formation, the Southern Urals: Sr isotopic characteristics and Pb–Pb age. Lithol. Min. Resour. 40, 195–215.

Kuznetsov, A.B., Melezhik, V.A., Gorokhov, I.M., Melnikov, N.N., Konstantinova, G.V.,

Kutyavin, E.P., Turchenko, T.L., 2010. Sr isotopic composition of Paleoproterozoic 13C-rich carbonate rocks: the Tulomozero Formation, SE Fennoscandian Shield. Precambr. Res. 182, 300–312.

Kuznetsov, A.B., Ovchinnikova, G.V., Gorokhov, I.M., Letnikova, E.F., Kaurova, O.K.,

Konstantinova, G.V., 2013. Age constraints on the Neoproterozoic Baikal Group from combined Sr isotopes and Pb-Pb dating of carbonates from the Baikal type section, southeastern Siberia. J. Asian Earth Sci. 62, 51–66.

Kuznetsov, A.B., Semikhatov, M.A., Gorokhov, I.M., 2014. The Sr isotopic chemostrati- graphy as a tool for solving stratigraphic problems of Upper Proterozoic (Riphean and Vendian). Stratigr. Geol. Correl. 22, 6, 553–575.

Kuznetsov, A.B., Bekker, A., Ovchinnikova, G.V., Gorokhov, I.M., Vasilyeva, I.M., 2017. Unradiogenic strontium and moderate-amplitude carbon isotope variations in early Tonian seawater after the assembly of Rodinia and before the Bitter Springs Excursion. Precambr. Res. 298, 157–173.

Land, L.S., 1985. The origin of massive dolomite. J. Geol. Educ. 33, 112–125.

Ling, H.-F., Chen, X., Li, D., Wang, D., Shields-Zhou, G.A., Zhu, M., 2013. Cerium anomaly variations in Ediacaran-earliest Cambrian carbonates from the Yangtze Gorges area, South China: implifications for oxygenation of coeval shallow seawater. Precambr. Res. 225, 110–127.

Machel, H.G., 1997. Recrystallization versus neomorphism, and the concept of ‘significant recrystallization’ in dolomite research. Sed. Geol. 113, 161–168.

Machel, H.G., 2004. Concepts and models of dolomitization: a critical reappraisal. In: Braithwaite C.J., Rizzi G., Darke G. (eds). The Geometry and Petrogenesis of Dolomite Hydrocarbon Reservoirs. Geological Society, London, Special Publications, 235, 7–63.

Mazzullo, S.J., 1992. Geochemical and neomorphic alteration of dolomite: a review. Carbonates Evaporites 7 (1), 21–37.

Melnikov, N.V. (Ed.), 2005. Stratigraphy of Oil and Gas Basins of Siberia. Riphean and Vendian of Siberian Platform and Its Plated Border. Academic Publishing “Geo”,  Novosibirsk, pp. 423 [in Russian].

Montanez, I.P., Read, J.R., 1992. Fluid-rock interaction history during stabilization of early dolomites, Upper Knox Group (Lower Ordovician), U.S. Appalachians. J. Sedim. Petrol. 62, 753–778.

Moore C.H., 2001. Carbonate Reservoirs. Porosity Evolution and Diagenesis in A Sequence Stratigraphy Framework. Elsevier. 461pp.

Moskalenko, A.N., Khusnitdinov, R.R., 2017. Prediction of fracture intensity of carbonates based on the results of paleostress estimation by fault kinematic analysis based on the 3d seismic data (kuyumba oil field)Vestnik of Saint Petersburg University. Earth Sci. 62 (3), 311–322. Nagovitsin, K., 2009. Tappania-bearing association of the Siberian platform: biodiversity, stratigraphic position and geochronological constraints. Precambr. Res. 173, 137–145.

Nothdurft, L., Webb, G.E., Kamber, B.S., 2004. Rare earth elements geochemistry of Late Devonian reefal carbonates, Canning Basin, Western Australia: confirmation of a seewater REE proxy in ancient limestones. Geochem. Cosmochim. Acta 67, 263–283.

Ossa Ossa, F., Eickmann, B., Hofmann, A., Planavsky, N.J., Asael, D., Pambo, F., Bekker, A., 2018. Two-step deoxygenation at the end of the Paleoproterozoic Lomagundi event. EPSL 486, 70–83.

Partin, C.A., Bekker, A., Corrigan, D., Modeland, S., Francis, D., Davis, D.W., 2014. Sedimenological and geochemical basin analysis of the Paleoproterozoic Penrhyn and

Piling groups of Arctic Canada. Precambr. Res. 251, 80–101.

Peterson, M.N.A., von der Borch, C.C., 1965. Chert: modern inorganic deposition in a carbonate-precipitating locality. Science 149, 1501–1503.

Planavsky, N.J., McGoldrick, P., Scott, C., Li, C., Reinhard, C.T., Kelly, A., Bekker, A., Love, G., Lyons, T.W., 2011. Widespread iron-rich conditions in the mid-proterozoic ocean. Nature 477, 448–451.

Planavsky, N., Bekker, A., Rouxel, O.J., Kamber, B., Hofmann, A., Knudsen, A., Lyons, T. W., 2010. Rare earth elements and yttrium compositions of Archean and paleopro-terozoic Fe formations revisited: new perspectives on the significance and mechan- isms of deposition. Geochim. Cosmochim. Acta 74, 6387–6405.

Postnikova, O.V., Fomicheva, L.N., Soloveva, L.V., 2008. Paleogeographic and paleodi- namic conditions of development of Riphean-Vendian sedimentary basin in the south of Siberia nd its connection with hydrocarbon potential. Geol. Oil Gas 1, 8–15 [in Russian].

Pustylnikov A.M., Vakulenko L.G., 1997. Origin and forms of occurrence of silica in

Riphean deposits of the Baikit Anteclise (Siberian platform) in connection with the problem of formation of fracture-cavrnous collectors. Geologia I Geophisica, 38, 12, 1962–1967 [in Russian].

Shein V.S., 2006. Geology and Oil and Gas Occurrence in Russia. Moscow, VNIGNI, 776p. [in Russian].

Shenfil V.Yu., Primachok A.N., 1996. Stratigraphy of Riphean Deposits in the Yurubcheno-Tokhoma Zone of Oil Accumulation in the Baikit Anteclise. Geologia I Geophisica, 37, 10, 65-75 [in Russian].

Siever, R., 1992. The silica cycle in the Precambrian. Geochim. Cosmochim. Acta 56, 3265–3272.

Slack, J.F., Grenne, T., Bekker, A., Rouxel, O.J., Lindberg, P.A., 2007. Suboxic deep seawater in the late Paleoproterozoic: Evidence from hematitic chert and iron for- mation related to seafloor-hydrothermal sulfide deposits, central Arizona, USA. Earth Planet. Sci. Lett. 255, 243–256.

Slack, J.F., Grenne, T., Bekker, A., 2009. Seafloor-hydrothermal Si-Fe-Mn exhalites in the Pecos greenstone belt, New Mexico, and the redox state of ca. 1720 Ma deep sea- water. Geosphere, 5, 302–314.

Tang, D., Shi, X., Wang, X., Jiang, G., 2016. Extremely low oxygen concentration in mid- Proterozoic shallow waters. Precambr. Res. 276, 145–157.

Taylor, S.R., McLennan, S.M., 1985. The Continental Crust; Its composition and evolution; an examination of the geochemical record preserved in sedimentary rocks. Blackwell, Oxford, pp. 312.

Tlig, S., M’Rabet, A., 1985. A comparative study of the Rare Earth Element (REE) dis- tributions within Lower Cretaceous dolomites and limestones of Central Tunisia. Sedimentology 32, 897–907.

Tostevin, R., Shields, G.A., Tarbuck, G.M., He, T., Clarkson, M.O., Wood, R.A., 2016. Effective use of cerium anomalies as a redox proxy in carbonate-dominated marine settings. Chem. Geol. 438, 146–162. 

Varaksina I.V., 2006. Silicification role in formation of cavernous-fracture reservoir rocks of Yurubcheno-Tokhoma oil-and-gas depositing. Materials of the 4th All-Russian li- thological meeting, 1, Moscow, GEOS, 241–243 [in Russian].

Varaksina, I.V., Khabarov, E.M., 2000. Sedimentation environments and post-sedi- mentation changes of Riphean carbonate deposits of Kuyumbinskoye field. Geol. Oil Gas 1 [in Russian].

Vasileva, K.Y., Bakay, E.A., Ershova, V.B., Khusnitdinav, R.R., Khudoley, A.K., Kozlova, E.V., Soloveva, S.A., 2016. Subsidence and thermal history of the Baikit Anteclise sedimentary basin. Mosc. Univ. Geol. Bull. 71 (6), 445–450.

Veizer, J., 1983. Chemical diagenesis of carbonates: theory and application of trace ele- ment technique. In: Arthur, M.A., Anderson, T.F., Kaplan, I.R., Veizer, J., Land, L.S. (Eds.). Stable Isotopes in Sedimentary Petrology. Society of Economic Paleontologists and Mineralogists, Short Course 10, p. 3-1 to 3-100.

Vernikovsky, V.A., Kazansky, A.Yu, 2009. The geodynamic evolution of the folded framing and the western margin of the Siberian craton in the Neoproterozoic: geo- logical, structural, sedimentological, geochronological, and paleomagnetic data. Russ. Geol. Geophys. 50, 380–393.

Vernikovsky, V.A., Vernikovskaya, A.E., Pease, V.L., Gee, D.G., 2004. Neoproterozoic orogeny along the margins of Siberia. In: Gee, D.G., Pease, V., (Eds.). The Neoproterozoic Timanide Orogen of eastern Baltica. London, Geological Society, London, Memoirs, 30, 233–247.

Vinogradov, V.I., Korzh, M.V., Sorokina, I.E., Buyakaite, M.I., Kuleshov, V.N., Postelnikov, E.S., Pustylnikov, A.M., 1998. Isotopic features of epigenetic changes of pre-Vendian sediments of sedimentary cover in Baikit uplift, Siberian platform. Lithol. Mineral Resour. 3, 268–279 [in Russian].

Wang, G., Wang, T.-G., Han, K., Wang, L., Shi, S., 2017. Recognition of a novel Precambrian petroleum system based on isotopic and biomarker evidence in Yangtze platform, South China. Mar. Petrol. Geol. 68, 414–426.

Zaitseva, T.S., Semikhatov, M.A., Gorokhov, I.M., Sergeev, V.N., Kuznetsov, A.B., Ivanovskaya, T.A., Melnikov, N.N., Konstantinova, G.V., 2016. Isotopic geochro- nology and biostratigraphy of Riphean deposits of the Anabar Massif, North Siberia. Stratigr. Geo. Correl. 24 (6), 549–574.

Zaitseva, T.S., Gorokhov, I.M., Semikhatov, M.A., Kuznetsov, A.B., Ivanovskaya, T.A., Konstantinova, G.V., Dorzhieva, O.V., 2018. “Rejuvenated” Globular Phyllosilicates in the Riphean deposits of the Olenek Uplift (North Siberia): Structural identification and geological Significance of Rb–Sr and K–Ar Age data. Stratigr. Geo. Correl. 26 (6), 611–633.

Zaitseva, T.S., Kuznetsov, A.B., Ivanova, N.A., Maslennikov, M.A., Pustylnikova, V.V., Turchenko, T.L., Nagovitsin, K.E., 2019. Rb-Sr Age of Riphean Glauconites of the Kamo Group (Baikit Anteclise, Siberian Craton) Doklady. Earth Sci. 488 (Part 1), 1013–1017.

Zhang, K., Zhu, X., Wood, R., Shi, Y., Gao, Z., Poulton, S.W., 2018. Oxygenation of the Mesoproterozoic ocean and the evolution of complex eukaryotes. Nat. Geosci. 11, 345–350.

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