Research Paper
GEOSPHERE Tectonic evolution of the Mesozoic South Anyui suture zone, GEOSPHERE; v. 11, no. 5 eastern Russia: A critical component of paleogeographic doi:10.1130/GES01165.1 reconstructions of the Arctic region 18 figures; 5 tables; 2 supplemental files; 1 animation Jeffrey M. Amato1, Jaime Toro2, Vyacheslav V. Akinin3, Brian A. Hampton1, Alexander S. Salnikov4, and Marianna I. Tuchkova5 1Department of Geological Sciences, New Mexico State University, MSC 3AB, P.O. Box 30001, Las Cruces, New Mexico 88003, USA CORRESPONDENCE: [email protected] 2Department of Geology and Geography, West Virginia University, 330 Brooks Hall, P.O. Box 6300, Morgantown, West Virginia 26506, USA 3North-East Interdisciplinary Scientific Research Institute, Far East Branch, Russian Academy of Sciences, Magadan, Portovaya Street, 16, 685000, Russia CITATION: Amato, J.M., Toro, J., Akinin, V.V., Hamp- 4Siberian Research Institute of Geology, Geophysics, and Mineral Resources, 67 Krasny Prospekt, Novosibirsk, 630091, Russia ton, B.A., Salnikov, A.S., and Tuchkova, M.I., 2015, 5Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia Tectonic evolution of the Mesozoic South Anyui su- ture zone, eastern Russia: A critical component of paleogeographic reconstructions of the Arctic region: ABSTRACT INTRODUCTION Geosphere, v. 11 no. 5, p. 1530–1564, doi:10.1130 /GES01165.1. The South Anyui suture zone consists of late Paleozoic–Jurassic ultra- The South Anyui suture zone (Fig. 1) is a remnant of a Mesozoic ocean Received 19 December 2014 mafic rocks and Jurassic–Cretaceous pre-, syn-, and postcollisional sedimen- basin that separated the Arctic Alaska–Chukotka microplate from Siberia Revision received 2 July 2015 tary rocks. It represents the closure of a Mesozoic ocean basin that separated and from the arcs and continental blocks that eventually formed the Kolyma- Accepted 22 July 2015 two microcontinents in northeastern Russia, the Kolyma-Omolon block and Omolon block of northeastern Russia (Seslavinsky, 1979; Parfenov, 1984). It is a Published online 27 August 2015 the Chukotka block. In order to understand the geologic history and improve key tectonic boundary for paleogeographic reconstructions of the Arctic region our understanding of Mesozoic paleogeography of the Arctic region, we ob- prior to the opening of the Amerasia Basin. Although its western termination is tained U-Pb ages on pre- and postcollisional igneous rocks and detrital zircons not clear (Franke et al., 2008; Kuzmichev, 2009), it can be traced eastward using from sandstone in the suture zone. We identified four groups of sedimentary outcrops of accretionary complexes, ophiolitic rocks, and magnetic anomalies rocks: (1) Triassic sandstone deposited on the southern margin of Chukotka; from the New Siberian Islands (Fig. 1) in the west to at least as far as central (2) Middle Jurassic volcanogenic sandstone that was derived from the Oloy Chukotka and, more speculatively, to northern Alaska, where it has been cor- arc, a continental margin arc, along the Kolyma-Omolon block, south of the related with the Angayucham suture zone (Churkin and Trexler, 1981; Nokle- Anyui Ocean, a sample of which yielded no pre-Jurassic zircons and a single berg et al., 2000; Amato et al., 2004). peak at 164 Ma; (3) suture zone sandstone that yielded Late Jurassic maximum The South Anyui–Angayucham suture has been used to define the pres- depositional ages and likely predated the collision; and (4) a Mid-Cretaceous ent-day southern boundary of the Arctic Alaska–Chukotka microplate (e.g., syncollisional sandstone that had a maximum depositional age of 125 Ma. Fujita, 1978; Silberling et al., 1994), a continental block with an area compara These rocks were intruded by postkinematic plutons and dikes with ages of ble to that of Greenland. It was displaced by the initial opening of the Arctic 109 Ma and 101 Ma that postdate the collision. We present a seismic-reflection basin in Early Cretaceous time (Grantz et al., 1990). Although Arctic Alaska– line through the South Anyui suture zone that indicates south-vergence of Chukotka translated across the Arctic to its present location, its initial geom thrusting of the Chukotka block over the Kolyma-Omolon block, opposite etry, initial position, and the kinematics of its trajectory remain elusive. A host of most existing models and opposite of the vergence in the Angayucham of competing models have been proposed through the years (e.g., Lane, 1997; suture zone, the postulated along-strike equivalent in Alaska. This suggests Lawver et al., 2002; Miller et al., 2006; Kuzmichev, 2009; Shephard et al., 2013). that Chukotka and Arctic Alaska may have different pre-Cretaceous histories, The Mississippian to Triassic stratigraphy of the North Slope basin of Alaska which could solve space problems with existing reconstructions of the Arctic matches that of the Canadian Arctic Islands, so that restoring Arctic Alaska region. We combine our detrital zircon data and interpretations of the seismic to the Canadian Arctic creates an alignment of the basin’s depocenters and line to construct a new GPlates model for the Mesozoic evolution of the region produces a reasonable alignment of facies belts (Toro et al., 2004). Also, both that decouples Chukotka and Arctic Alaska to solve space problems with pre- margins experienced a simultaneous rift event in the Early Cretaceous Period vious Arctic reconstructions. (Grantz et al., 1990), but it is not clear where to restore Chukotka. A signifi- For permission to copy, contact Copyright Permissions, GSA, or [email protected].
© 2015 Geological Society of America
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1530 by guest on 28 September 2021 Research Paper
120°E 160°E 160°W 120°W 100°W 6 Siberia SvB
NSI ge Ran Amerasia Basin 1 sk n 3 CAA Figure 1. Tectonic map of northern Pacific a y o and eastern Arctic regions (after Akinin,
h
k
r 2013; compiled using data from Klemperer e
V et al., 2002; Nokleberg et al., 1994). DZ—de- 2 trital zircon; NSI—New Siberian Islands; 70°N WI—Wrangel Island; OCVB—Okhotsk-Chu- Fig. 3 kotka volcanic belt; SP—Seward Peninsula; WI NSB—North Slope of the Brooks Range; BR—Brooks Range; ASZ—Angayucham 4 NSB suture zone; CAA—Canadian Arctic Islands; BR SvB—Sverdrup Basin. Red inset box shows OCVB Chukotka 5 Laurentia location of Figure 3. Regional detrital zircon ASZ (DZ) data sets are: (1) West Verkhoyansk SP (Prokopiev et al., 2008); (2) Indigirka River, Moma Basin; (3) New Siberian Islands Omolon (Miller et al., 2008); (4) Rauchua Basin Terrane TypesPost Accretionary Rocks (Miller et al., 2008); (5) Brooks Range fore- Craton Cenozoic land (Moore et al., 2015); (6) Sverdrup Basin (Omma et al., 2011). Craton Margin OCVB Arctic Alaska- 50°N Accretionary Prism Cretaceous deposits Chukotka microplate Seismic lines Jurassic deposits Oceanic Kolyma-Omolon 2DV Island Arc Mesozoic plutons South Anyui Zone Franke et al. 2008 500 km Metamorphic Cenozoic plutons 1 Regional DZ data sets
cant problem is that the Arctic Alaska–Chukotka microplate is too long to fit in the context of the Mesozoic evolution of the Arctic region, and we use them comforta bly in the Arctic reentrant without considerable overlap of continental to create a new plate-tectonic model developed using the GPlates program of crust. Thus, it is likely that Arctic Alaska–Chukotka underwent considerable in- Williams et al. (2012). ternal deforma tion during translation (e.g., Miller et al., 2006; Shephard et al., 2013). Miller et al. (2006) used detrital zircon data from Triassic sandstone of the circum-Arctic to show that the samples from Chukotka and Wrangel Island REGIONAL GEOLOGY have provenance signatures from Taimyr, Siberian Traps, and/or the Polar Urals, all regions of current Siberia. Because these detrital zircon data are in Crustal Blocks sharp contrast with samples from the Canadian Arctic and from northeastern Alaska, which have clear Laurentian affinities, Miller et al. (2006) concluded The geologic framework of northeastern Russia (Fig. 1) is the result of that Chukotka should be restored adjacent to the Taimyr and North Verk multistage accretion of arcs and continental fragments to the ancient Siberian hoyansk, east of the Polar Urals of Russia. craton. Relevant reviews of the regional geology include Zonenshain et al. We obtained detrital zircon ages from nine samples of Triassic through (1990), Nokleberg et al. (2000), and Shephard et al. (2013). The Siberian (or Cretaceous sedimentary rocks of the South Anyui suture zone. In these sam- North Asian) craton (Fig. 2) is made of several large Archean (ca. 3.2–2.7 Ga) ples, we observe a change in the detrital zircon signature from Triassic to Late granite-greenstone blocks assembled during an orogenic event at 2.1–1.8 Ga Jurassic rocks that coincides temporally with convergence along the margin (Rosen et al., 1994; Gladkochub et al., 2006). Most of the Siberian craton is blan- of the South Anyui Ocean. We also interpret the crustal-scale structure of the keted by a thick and largely flat-lying Neoproterozoic cover succession (Fig. 2), region visible in the 2DV deep-crustal seismic line. The seismic data show, con- with the exception of the southern part, where there was a long-lived active trary to previous models, that the South Anyui suture zone is a south-vergent margin with abundant Neoproterozoic (1.8 Ga), early Paleozoic (494–482 Ma), structural wedge, i.e., the opposite of the coeval Angayucham–Brooks Range and late Paleozoic (315–290 Ma) granite batholiths (Prokopiev et al., 2008) that orogen of Alaska. Our data from the South Anyui suture zone are interpreted characterize the detrital zircon populations of sediment derived from Siberia.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1531 by guest on 28 September 2021 Research Paper
Siberia Kolyma-Omolon Block Arctic Alaska-Chukotka Microplate Verkhoyansk Margin Omolon Oloy Arc South Anyui Chukotka Alaska North Slope Age Accretionary Complex (Ma) Period Stratified Intrusive Stratified Intrusive Stratified Intrusive Stratified Intrusive StratifiedSIntrusive tratified Intrusive 0 Rocks Rocks Rocks Rocks Rocks Rocks Rocks Rocks Rocks Rocks Rocks Rocks 2.6 Q T Brooks Range 66 Foreland Basin Okhotsk-Chukotka Okhotsk-Chukotka Okhotsk-Chukotka Okhotsk-Chukotka K Volcanic Belt Volcanic Belt Volcanic Belt Volcanic Belt Pri-Verkhoyansk Tytylveem arc Foreland Basin Oloy Arc 145 Nutesyn Rauchua Foreland Extensional Uyandina- Granitoids Yasachnaya arc Arc Basin Jr Main Batholith Main Batholith Egdegkich Beaufortian Belt Belt syenites Rift Sequence 201
Tr ? ? ? ? ? ? Triassic Continental Margin Turbidites 252 Verkhoyansk Passive Margin Perm Sequence Permo-Carb. Passive Margin 299 Delta Complexes Chert, Limestone Ellesmerian Seq. and Volcanics ? ? ? Pen Passive Margin Sequence 323
Mis ? ? ? ? ? ? 359 Rift Sequence Rift Aluchin Uyamkanda, Dev Sequence Ophiolite Vurguveem Andean Type Arc? Ophiolites Devonian 419 Granitoids
Sil Passive Margin Deformed 445 Devonian and Carbonate older rocks Ord Platform
485
Cam 541 Rodinia Rift Neo Sequence? Prot Wrangel 1000 Cratonal Platform Metamorphic Meso Cover Basement Prot ? ? ? 1600 Paleo Prot 2500 Arch Craton Craton ArcheanBasement Basement Basement
Gneiss Granitoids Gabbro/basalt Ophiolites Sandstone/ Siltstone Shale Limestone Volcanic/ conglomerate Volcaniclastic
Figure 2. Stratigraphic columns for areas referred to in the text, based on data in Nokleberg et al. (1994), with some minor changes based on this study. Q—Quaternary, T—Tertiary, K—Cretaceous, Jr—Jurassic, Tr—Triassic.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1532 by guest on 28 September 2021 Research Paper
A Devonian rifting event created the eastern passive margin of Siberia (Fig. 2), were interpreted to represent passive-margin shelf to deep-margin turbidite along which the immense Verkhoyansk clastic prism accumulated from Devo- sedimentation along the continental margin, sourced from a metamorphic nian to Jurassic time (Parfenov, 1991). complex (Tuchkova et al., 2009). The distribution of facies was used to infer The Omolon block (Fig. 1) consists of Precambrian metamorphic and ig- a source to the northeast, possibly in the Canadian Arctic or on the Chukotka neous basement ranging in age from 3.4 to 2.0 Ga covered by Neoprotero- Peninsula. Miller et al. (2006) instead showed that the detrital zircon U-Pb ages zoic low-grade metasediments and Paleozoic platformal rocks (Fig. 2; Zonen from these Triassic units point to source areas in the Taymyr Peninsula, the shain et al., 1990). Together, the Omolon block and its adjacent magmatic arcs Polar Urals, and Baltica, not the Canadian Arctic or Alaska (Miller et al., 2006). and collapsed oceanic basins are referred to as the Kolyma-Omolon block Above the angular unconformity that caps the Triassic turbidite succes- (Fig. 1), and it collided with Siberia to form the Verkhoyansk fold-and-thrust- sion (Fig. 2), there are Upper Jurassic and Lower Cretaceous arkosic sand- belt (Parfenov, 1991). Along the boundary between the Kolyma-Omolon and stone and conglomerate of the Rauchua foreland basin that signal the onset the Verkhoyansk prism (Fig. 1), there are two major belts of granitoid plutons of convergent deformation in the Chukotka fold belt and a switch in sediment emplaced prior to and during the collision: the Main belt, with ages of 152– provenance to a southerly source (Miller at al., 2008). The Chukotka fold belt 145 Ma, and the Northern belt, which is 135–127 Ma and strikes east-west, is a broad zone of tightly folded Triassic turbidites that locally have multiple
approximately parallel to the South Anyui suture zone (Parfenov, 1991; Layer slatey cleavages. The S1 cleavage, attributed to shortening during closure et al., 2001; Akinin et al., 2009). of the South Anyui suture, is typically subvertical in the area adjacent to the The Chukotka block (Fig. 1) of northeastern Russia includes the Chukotka South Anyui zone (Katkov et al., 2005) and south- or southwest-dipping near Peninsula, western Chukotka extending perhaps as far west as the New the north coast (Miller and Verzhbitsky, 2009; Miller et al., 2009). A subhori
Siberian Islands, and a large section of the East Siberian shelf, including zontal cleavage (S2) overprints the older fabrics in the vicinity of the Alar- Wrangel Island. It has been traditionally considered a component of the larger maut metamorphic massif (Fig. 3) and has been attributed to Mid-Cretaceous Arctic Alaska–Chukotka microplate, which also includes parts of northern (109–103 Ma) high-strain extensional deformation that was accompanied by Alaska such as the North Slope, Brooks Range, and Seward Peninsula (Moore widespread granitic magmatism (Miller et al., 2009). It appears that the overall et al., 1994). Most of Chukotka is covered by a thick succession of deformed structure of the Chukotka–South Anyui orogen is that of a bivergent conver- Triassic turbidites (Fig. 2) that obscure its older history. Based on a few ex- gent system, with south-directed thrusting in the South Anyui zone, as will be posures on the mainland and on Wrangel Island, it appears that basement is demonstrated later in this paper, and north-vergent tectonic transport in the composed of late Neoproterozoic crystalline rocks overlain by an early Paleo northern part of the Chukotka fold belt. zoic platformal succession (Kos’ko et al., 1993; Natal’in et al., 1999; Amato et al., 2014). Along the north coast of Chukotka, exposures of mid-Devonian granitoid plutons and metavolcanic rocks are interpreted as an arc–back-arc South Anyui Suture Zone system (Natal’in et al., 1999). The late Paleozoic rocks of Chukotka (Fig. 2) are represented by poorly exposed shallow-water carbonate and clastic rocks that The South Anyui suture zone (Figs. 1, 2, and 3) is a belt of intensely de- are found either in fault contact or are unconformably overlain by the Triassic formed Jurassic and Early Cretaceous lithic sandstone imbricated with vol succession (Chasovitin and Shpetnyi, 1964; Tuchkova et al., 2009). canic, volcaniclastic, and oceanic rocks, including basalt, chert, and ultramafic Triassic strata on Chukotka (Fig. 2) consist of thick successions (up to rocks, that separates Chukotka from the Kolyma-Omolon block to the south 3000 m) of rhythmically alternating mudstone, siltstone, and fine- to coarse- and the Siberian platform to the west (Seslavinsky, 1970, 1979; Natal’in, 1984; grained sandstone. Lithology is monotonous over large areas, fossils are rare, Parfenov, 1991; Natal’in et al., 1999; Sokolov et al., 2002, 2009). The South and the rocks are typically folded and slightly metamorphosed, making their Anyui suture zone was originally recognized by Seslavinsky (1979) based on stratigraphic study challenging. Available fossil data, supported by detrital the geologic maps of Dovgal (1964), which revealed ultramafic rocks between zircon studies, indicate that this sedimentary succession spanned the entire the Bolshoi Anyui and Maly Anyui Rivers (Fig. 3). Strong aeromagnetic anom- Triassic period from Induan to Norian time, and continued into Lower Jurassic alies outline the exposed part of the South Anyui suture zone and continue time, where it is cut by a major unconformity (Tibilov et al., 1982; Tynankergav to the west across a broad area covered by Neogene deposits and onto the and Bychkov, 1987; Bychkov and Solov’yov, 1992; Bychkov, 1994a, 1994b; Tuch shelf as far as the New Siberian Islands, where ophiolite fragments are also ex- kova et al., 2009). Lower Triassic deposits are intruded by abundant gabbro posed (Kuzmichev, 2009). To the east, the South Anyui suture zone is obscured sills (Gelman, 1970). These sills, dated at ca. 252 Ma in eastern Chukotka, have by extensive Late Cretaceous deposits of the Okhotsk-Chukotka volcanic belt been interpreted to be part of the large igneous province that produced the (Fig. 3). The magnetic anomalies are not clear, but on the Chukotka Peninsula, Siberian Traps (Ledneva et al., 2011). Tuchkova et al. (2009) recognized deep there are small exposures of mafic rocks that have been proposed to belong shelf, slope, rise, and deep basin lithofacies at different stages of the Triassic of to the suture (Sokolov et al., 2002). The South Anyui suture zone has also central Chukotka and mapped their distribution in time and space. These strata been correlated to the Angayucham suture zone of northern Alaska (Patton
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1533 by guest on 28 September 2021 Research Paper
160°E 165°E 170°E East Siberian Sea 70°N 70°N 0 50 100 150 km Pevek
Chauna Bay
Alarmaut Kolyma Rive South An r Chuk Bolshoi An
yui Suture Zone otk yui River 68°N 68°N a
Bilibino Figure 3. Geologic map of central Chu- kotka modified from Gorodinski (1980). An The South Anyui suture zone (SASZ) g boundaries are mapped under Cenozoic a and Cretaceous cover on the basis of rka Alazeya- F Uyamkanda aeromagnetic data in Klemperer et al. au (2002). The box shows location of Figure 4. l t OCVB—Okhotsk-Chukotka volcanic belt; Jr—Jurassic. Oloy
Vurguveem
Aluchin
66°N 66°N
160°E 165°E 170°E
Cenozoic Cretaceous L. Cretaceous Jurassic Jr Nutesyn Jr Oloy M-U Triassic M-U Triassic Sed Perm-Carb Devonian Sed. OCVB Sed. Arc Arc Sed. + gabbro sills Sed. Sed.
Cretaceous OphioliteSASZ Boundary 2DV Seismic Line Pluton
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1534 by guest on 28 September 2021 Research Paper
and Tailleur, 1977; Churkin and Trexler, 1981; Nokleberg et al., 2000), and it Merzlyui ophiolites (Figs. 3 and 4; see Sokolov et al., 2002, 2009). These com- may also be present on Saint Lawrence Island on the Bering Shelf (Patton and plexes consist of various faulted stacks of serpentinized peridotite and other Csejtey, 1980; Till and Dumoulin, 1994). Thus, in many tectonic models, the mafic and ultramafic rocks, including pyroxenite, gabbro, sheeted dikes, South Anyui–Angayucham suture is one of the unifying features of the Arctic basalt-chert successions, and plagiogranites. The Aluchin complex (Fig. 3) Alaska–Chukotka microplate (e.g., Nokleberg et al., 2000). also includes blueschist-facies metamorphic rocks (Dovgal et al., 1975). The The South Anyui suture zone is a critical component of Mesozoic Arctic 40Ar/39Ar analyses from ultramafic rocks in the upper Uyamkanda River (Fig. 4) paleogeographic reconstructions, but there are persistent uncertainties about yielded dates of 257–229 Ma, which are consistent with a Permian or Early Tri- the geology of this area. The controversial aspects of the South Anyui suture assic age, although it is not clear whether some of these argon dates provide zone are the following: (1) There are multiple exposures of mafic/ultramafic the age of the protolith or its subsequent metamorphism (Sokolov et al., 2009). rocks with different compositions, apparent ages, and relationships with host Carboniferous 40Ar/39Ar dates were obtained from the Vurguveem ultramafic rocks. Some of these mafic/ultramafic complexes may be remnants of the complex, east of our study area (Fig. 3; Sokolov et al., 2009). Ganelin et al. South Anyui Ocean (e.g., Aluchin), others may represent arc basement (Vurgu- (2013) obtained a 280 Ma U-Pb zircon date from a cumulate gabbro in the Alu- veem complex; Ganelin and Silantyev, 2008), and still others appear to be lay- chin complex (Fig. 3). Sheeted dikes in the Aluchin ultramafic complex yielded ered mafic intrusions with ultramafic cumulates (Uyamkanda massif; Lychagin mainly Triassic 40Ar/39Ar dates (Sokolov et al., 2009; Ganelin et al., 2013). Over- et al., 1992). (2) The ages of these mafic/ultramafic complexes are not well all, ultramafic and gabbroic rocks in the region have 40Ar/39Ar dates ranging constrained. The majority of the published ages appear to indicate that they from ca. 320 Ma to ca. 220 Ma (Sokolov et al., 2015), with a few gabbros at ca. are Triassic or even late Paleozoic (Sokolov et al., 2009, 2015), which contra 150 Ma that are likely related to Jurassic arc magmatism, as discussed later dicts models in which they are associated with Jurassic arc complexes or oce- herein (Sokolov et al., 2015). anic crust. (3) The orientation of the exposed mafic/ultramafic complexes is The ultramafic bodies were initially interpreted as ophiolite successions not parallel to the inferred suture zone. The South Anyui suture zone trends representing the Jurassic South Anyui Ocean that formerly separated Chu- mainly northwest-southeast, parallel to structural grain of the Chukotka fold kotka from the Kolyma-Omolon block or the Siberian craton (e.g., Zonenshain belt, but the largest ultramafic complex, the Aluchin complex, has exposures et al., 1990; Parfenov, 1991), and this model has been used in the tectonic mod- with north-south contacts. There has been some speculation that these orien- els for northeastern Russia (Parfenov, 1991; Nokleberg et al., 2000; Shephard tations result from postaccretionary strike-slip motions parallel to the South et al., 2013). However, the available geochronology points toward crystalliza- Anyui suture zone (Sokolov et al., 2002, 2009). (3) Previous structural models tion, and possibly also initial metamorphism of the ophiolites, having taken of the South Anyui suture zone emphasize northward emplacement of oceanic place in the Permian–Triassic. Furthermore, it has been suggested that some of rocks onto the Chukotka passive margin (Bondarenko, 2004; Sokolov et al., these rocks crystallized in a suprasubduction setting and represent island-arc 2002, 2009), but field observations and seismic data clearly show that some of lower crust (Ganelin and Silantyev, 2008; Sokolov et al., 2009) or back-arc basin the structures in the South Anyui suture zone are south-vergent (see fig. 4 in magmatism (Ganelin, 2011); therefore, little direct evidence for the Jurassic Sokolov et al., 2002; fig. 13 in Sokolov et al., 2009). (4) Late Jurassic volcanic seafloor of the South Anyui Ocean has been found so far. arc rocks are found both in the South Anyui suture zone (Nutesyn arc) and on Another issue is that the outcrops of the ultramafic rocks are not every- the northern margin of the Kolyma-Omolon terrane (Oloy arc), yet geochrono- where parallel to the suture. In particular, the Aluchin complex (Fig. 3) has a logical data on these rocks are sparse, and there is disagreement as to whether NNE trend, nearly orthogonal to the suture. On the basis of its orientation and these were intra-oceanic or Andean-type arcs. late Paleozoic age, Sokolov et al. (2009) assigned the Aluchin ophiolites to the Fundamentally, there is agreement that the South Anyui suture zone is the Yarakvaam island-arc terrane, which is distinct from their South Anyui terrane. manifestation of the collision between two blocks with different ages, sepa- rated by an ocean basin that closed as the result of subduction ending with accretion between the Kolyma-Omolon and Chukotka blocks in the Early Cre- Mesozoic Rocks of the South Anyui Zone taceous Period. The following provides a general overview on some of the key Mesozoic clastic strata that are exposed across the South Anyui suture zone (Fig. 4). A South Anyui Ocean and Ultramafic Complexes simplified version of the geologic map is included that shows the major fea- tures of the region (Fig. 5). Mafic-ultramafic complexes are found at several separate localities in, and Jurassic rocks are exposed throughout the South Anyui suture zone in near, the South Anyui suture zone, and they have been interpreted as ophio- northeast-southwest–trending belts (Figs. 4 and 5). Upper Jurassic rocks have lites or ophiolite fragments. These include the large Aluchin and Vurguveem been reported along the northern margin of the suture zone and consist pri- (or Gromadnesky) complexes, and the smaller Uyamkanda (or Polyarny) and marily of calc-alkaline to subalkaline volcanic rocks that are interbedded with
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1535 by guest on 28 September 2021 on 28 September 2021 by guest Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf Research Paper Sedimentar Pr Pr Units of the South An Arc-related and Syn- P Quaternar Chukotka microplate. Figure 4. Geologic map of South Anyui scale Russian maps (e.g., Yegorov, zone based on 1:200,000 1962; Dovgal, 1964; Gulevitch, 1968) and this study. AACM—Arctic Alaska– ost e-c e-c -c 1 4 3 2 ollisional Units ollisional Units-AA ollisional Units y Units (P (P Aluchin ophiolit (P Merzly ultr Vu and v Upper P Tr Tr Chukotk Tr sedimentar M (J of the Uyamk Gabbro and ultramafic rocks v Jurassic v Late Jurassic sedimentar rocks Cretaceous sedimentar intrusiv Cretaceous intermediate Cretaceous granites unconsolidated sedimen Undiff Basalt flow of the Ainak v Cretaceous sedimentar y Units of the Oloy Ar olcaniclastic rocks: olcanic rocks urassic?) iassic gabbr iassic granitic rocks iassic sedimentar ermian?) ermian-T ermian-T id-Jurassic v rguv Seismic line location Thrust faults Geologic contac olcanic rocks erentiated eem ultramafic comple e rocks aleo a F olcanic and amafic comple s riassic?) riassic?) old Belt y rocks collisional zoic (?) sedimentar hkurgen basin yui Z anda massif o olcaniclastic CM e one y rocks of the (Nutesyn Arc) ts y y and y rocks
t x c x y 66°20 ′ 66°40 ′ 67°00 ′ 67°20 ′ 67°40 ′ N 68°00 ′ N N N N N 100 = AN100 336 = Z33 6 321 = Z32 1 02An-01 to 02An-3 All sample numbers 1–32 re Geochr 60 65 25 2 60 35 Rive r Uyamkanda onology Sample 32 1 33 6 33 60 2 70 1500 20 52 85 70 65 35 2 1550 165°00 ′ 31 4 85 1 32 Ke E 4 80 fe O y rlovka Rive r to samples 30 25
54 16 Anyu Maly Ot Detrital zircon samples To Shotpoints on seismic lin Dated igneous rocks
r 30
wn s her sed sample s
r 30 Rive i 17,1 8 10 0 60 12
15 60 1600 (ELMCH2.6) Kepe 35 65 166°00 ′ E 73 35 4 10 2 rv 1 49 eem 7 14 13 , 45 15 11 80 5
Bolshoi An 60 70 30 30 40 Rive r Ustieva
33 40
A 25
n
e g
yui a 20
25 km r
1650 34
k 60
25 50
a 45 (ELMCH3.1b )
R Bilibino
iv F
e a 60
50
r
u 65 l t 30 30 N 3 167°00 ′ 45 30 25 E
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia 1536 Research Paper
composed of tuffaceous turbidites, tectonic mélange, and volcanic and sedi mentary olistostrome blocks has been noted along the southern boundary of the Nutesyn (or Kulpolney) arc in the southeastern part of the suture zone Triassic passive margin strata (Sokolov et al., 2009). These strata range in age from Late Jurassic (Oxfordian– of the Arctic-Alaska-Chukotka microplate Kimmeridgian) to Early Cretaceous (Berriasian–Valanginian) based on occur- comprising part of the Chukotka Fold Belt rences of radiolarian and other faunal occurrences (Radziwill and Radziwill, 1975; Shekhovtsov and Glotov, 2001; Sokolov et al., 2009). Uyamkanda ma c-ultrama c Jurassic rocks in the central part of the suture zone consist primarily of massif (Late Jurassic) Upper Jurassic siliciclastic strata (interbedded sandstone and siltstone) that were likely deposited in shallow- to deep-marine fan systems (Sokolov et al., Merzly 2009). Depositional ages are thought to be Late Jurassic (late Kimmeridgian– ultrama c early Tithonian) based on faunal remains (Shekhovtsov and Glotov, 2001). SAZ complex Jurassic volcanic rocks (Permo-Triassic) of the Nutesyn arc Turbidite deposits are Late Jurassic–Early Cretaceous (Tithonian–Valanginian) in age based on fossils (Sokolov et al., 2002; Bondarenko, 2004). Cretaceous rocks are exposed both in the main parts of the South Anyui Jurassic-Early Cretaceous sedimentary rocks of the suture zone as well as overlying Triassic rocks on the Chukotka block and parts South Anyui Suture Zone Vurguveem of the Oloy arc rocks (Fig. 4; Dovgal, 1964). A succession of Upper Jurassic– ma c-ultrama c Lower Cretaceous tuffaceous turbidites, tectonic mélange, and volcanic and massif (Permian?) sedimentary olistostrome blocks occurs in the southeastern part of the suture Jurassic A n SAZ sedimentary g a zone. These strata are as young as Early Cretaceous (Berriasian–Valanginian), and volcanic rk a F based on faunal occurrences (Radziwill and Radziwill, 1975; Shekhovtsov and Aluchin rocks of the Oloy au ultrama c arc (Yarakvaam Terrane) lt Glotov, 2001), and overlap in part with volcanism and sedimentation associ- complex Paleozoic ated with the Nutesyn arc. (Permo - sedimentary/ Triassic?) volcanic rocks Lower Cretaceous rocks in the central part of the suture zone consist pri- marily of siliciclastic strata that were likely deposited in shallow- to deep- marine fan systems (Sokolov et al., 2009). These strata have been reported from the upper parts of an Upper Jurassic–Lower Cretaceous flysch unit and Post-collisional Jurassic Aptian to Late Campanian were interpreted to reflect sedimentation in a forearc basin setting and rem- sedimentary sedimentary and and volcanic volcanic rocks of nant ocean basin (Sokolov et al., 2009). The flysch unit consists primarily of rocks of the the Ainakhkurgen basin tabular deposits of interbedded sandstone and siltstone and is thought to be Oloy arc (Yarakvaam as young as Early Cretaceous (Tithonian–Valanginian; Sokolov et al., 2002; Terrane) Jurassic Bondarenko, 2004). sedimentary Early Cretaceous (Aptian–Albian) volcanic and sedimentary rocks in the and volcanic N rocks of the Oloy Ainakhkurgen basin (Fig. 5; Shekhovtsov and Glotov, 2001) are thought to arc represent postcollisional overlap assemblages (Nokleberg et al., 1994). 25 km Roughly age-equivalent strata are exposed along the southern margin of the suture zone (Dovgal, 1964) and may also represent postcollisional sedi mentation. Figure 5. Simplified map based on Figure 4 showing the main tectonic elements of the study area. SAZ—South Anyui suture zone. Jurassic Volcanic Arcs
tuffaceous sandstone and volcaniclastic and siliciclastic turbidite succes- Two Jurassic volcanic arcs existed within the South Anyui Ocean or near its sions (Natal’in, 1984; Lychagin et al., 1991; Sokolov et al., 2002; Bondarenko, northern and southern margins: the Nutesyn arc of the Chukotka margin and 2004; Sokolov et al., 2009). A Late Jurassic age has been assigned to clas- the Oloy arc of the Kolyma-Omolon margin (e.g., Parfenov, 1984; Nokleberg tic strata based on isolated occurrences of Oxfordian–Kimmeridgian marine et al., 2000). They initiated at ca. 160 Ma and ceased during collisional clo- fossils (Shekhovtsov and Glotov, 2001). A roughly age-equivalent succession sure of the South Anyui Ocean in Mid-Cretaceous time (e.g., Nokleberg et al.,
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1537 by guest on 28 September 2021 Research Paper
2000; Shephard et al., 2013). Both are poorly exposed and include a mixture of kotka fold belt (Miller et al., 2009). One granite in the South Anyui suture zone, volcanic rocks and volcanigenic sedimentary rocks. According to Zonenshain west of the Orlovka River, yielded a date of 109 ± 3 Ma (Fig. 4; sample AN-100 et al. (1990), both were oceanic arcs, although other authors disagree (e.g., of Miller et al., 2009). This magmatic event has been attributed to the onset of Natal’in, 1984; Parfenov, 1997; Nokleberg et al., 2000). extensional deformation linked to rifting in the Arctic basin (Miller et al., 2009). The Nutesyn arc of Natal’in (1984) has also been referred to as the Kulpol- Mid-Cretaceous magmatism was followed by regional exhumation, develop- ney arc by Sokolov et al. (2002, 2009). We use the original term, Nutesyn arc, ment of an angular unconformity, and eruption of the Okhotsk-Chukotka vol- as did Nokleberg et al. (2000) and Shephard et al. (2013), to avoid confusion. canic belt from 106 to 77 Ma, driven by subduction of the paleo–Pacific Ocean This arc system has been correlated to the Koyukuk island arc in Alaska (e.g., (Akinin and Miller, 2011). The Okhotsk-Chukotka volcanic belt is typically flat- Nokleberg et al., 2000). It was originally interpreted as a continental-margin lying and clearly overlaps the South Anyui suture zone and the structures of arc (Natal’in, 1984; Parfenov, 1997), but Sokolov (2009, 2015) suggested that it the Chukotka fold belt. was more likely an island arc. Some workers have proposed that mafic/ultra mafic rocks of the Vurguveem complex represent basement to this island arc (Ganelin and Silantyev, 2008). Shephard et al. (2013) showed it as an island Timing of Collision arc near Chukotka at 160–150 Ma, which matches our preferred model. Re- gardless of whether it was oceanic or continental, the arc was likely close to The timing of the collision between the Arctic Alaska–Chukotka microplate the northern margin of the South Anyui Ocean basin during Late Jurassic time and the Kolyma-Omolon block is constrained by crosscutting relationships (Zonenshain et al., 1990; Ti’lman and Bogdanov, 1992; Nokleberg et al., 2000). and 40Ar/39Ar cooling ages. Most plutons that cut folded Jurassic–Cretaceous In our field area, Nutesyn arc rocks crop out as a narrow belt of andesitic vol- rocks are 117–109 Ma in age (Miller et al., 2009). Sokolov et al. (2009) reported canic rocks that are inferred to be Jurassic age based on associated fossils 40Ar/39Ar dates on greenschists of 119–106 Ma that are inferred to be related to (Radzivill, 1964; Natal’in, 1984). Associated Jurassic–Cretaceous rocks include the late stages of the collision. The Okhotsk-Chukotka volcanic belt is largely volcaniclastic sandstone, flysch deposits, and dismembered ophiolite (Sokolov flat lying and clearly overlapped the South Anyui suture zone and the struc- et al., 2002, 2009; Bondarenko et al., 2003). tures of the Chukotka fold belt after 106 Ma (Akinin and Miller, 2011). Thus, it The Oloy arc is Jurassic–Early Cretaceous in age (160–140 Ma; Layer et al., appears that the collision occurred in Early Cretaceous time prior to 117 Ma. 2001; Shephard et al., 2013) and consists of mafic–siliceous volcanic and sedi Shephard et al. (2013) used the opening of the Amerasia Basin and the sub- mentary rocks (e.g., Nokleberg et al., 1994). Lower–Middle Jurassic strata sequent rotation of the Arctic Alaska–Chukotka microplate as evidence of the that may predate the Oloy arc are overlain by Late Jurassic–Early Cretaceous closing of the South Anyui Ocean, with a final collision around 126–120 Ma, (Oxfordian–Valanginian) pyroclastic and volcaniclastic strata associated with which matches the existing geochronological data. the arc (Afizkiy, 1970; Ti’lman et al., 1977; Parfenov, 1984; Shekhovtsov, 1991; Parfenov et al., 1993; Nokleberg et al., 1994). Nokleberg et al. (2000) referred to the Oloy arc as a continental margin arc that formed under a south-dipping METHODS subduction zone at the southern edge of the South Anyui Ocean, but in their tectonic models, they show it as an island arc near the Kolyma-Omolon block. U-Pb Geochronology Shephard et al. (2013) showed it as a continental margin arc at 160–150 Ma, which matches our preferred model. U-Pb geochronology was carried out using two methods. Sensitive high- resolution ion microprobe–reverse geometry (SHRIMP-RG) dating of igneous rocks was conducted at the Stanford–U.S. Geological Survey Ion Probe Facil- Cretaceous Magmatism ity. The primary beam excavated an area of ~25–30 µm across to a depth of ~1 µm. The analytical routine followed Williams (1998) and Strickland et al. The rocks of the South Anyui suture zone and the Chukotka fold belt were (2011). The SQUID program (Ludwig, 2005) was used for data reduction. Iso- intruded by numerous Cretaceous plutons and dikes, predominantly of granitic topic compositions were calibrated by replicate analyses of zircon standard composition. The oldest known is a syenite adjacent to the Aluchin ophiolite R33, which has an age of 419 Ma (Black et al., 2004). The 206Pb/238U ages were with a U-Pb zircon date of 142 Ma (Moll-Stalcup et al., 1995; see also our data corrected for common Pb using 207Pb. Common Pb compositions were es- herein) that intrudes Jurassic sedimentary rocks (Dovgal, 1964). Most of the timated from Stacey and Kramers (1975). We used the SHRIMP-RG to date intrusive rocks though, dated by the U-Pb method, range from 117 to 109 Ma two crosscutting dikes and to obtain additional ages on detrital zircons from and are clearly posttectonic with respect to shortening in the South Anyui-Chu- four samples.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1538 by guest on 28 September 2021 Research Paper
Laser ablation–multicollector inductively coupled plasma–mass spec- IGNEOUS LITHOLOGY AND GEOCHRONOLOGY RESULTS trometry (LA-MC-ICP-MS) dating was conducted on sedimentary rocks at the Arizona LaserChron Laboratory at the University of Arizona. Beam diameter Jurassic Volcanic Rocks was generally 35 µm. Errors on spot ages of individual zircons grains are re- ported in the text and tables at 1s, and we report weighted mean ages in the Late Jurassic volcanic and volcaniclastic rocks crop out over an area of text and figures at the s2 level. Data are presented on concordia diagrams 25 km × 100 km in the study area. Rock types range from rhyolite tuffs to mafic and relative probability distribution diagrams using Isoplot (Ludwig, 2003). lavas. This unit was included in the Nutesyn arc complex by Natal’in (1984) “Peak” ages refer to the peaks on relative probability distribution diagrams. and is overlain by Early Cretaceous sedimentary rocks that are folded about Each of our data sets is a sampling distribution from a larger population. Lim- NW-SE–trending fold axes and intruded by Mid-Cretaceous granitoid plutons. itations from sample size, lithology, and analytical cost reduced our overall n We sampled a highly altered andesite (02An-7) from this unit for geo- values in some samples. Maximum depositional ages were calculated using chronology, but it was barren of zircon. The rock is gray color, is mostly the weighted mean of the grains that make up the youngest peak consisting equicrystalline, and is dominated by altered plagioclase and amphibole of n > 2 ages. We used a discordance filter of 10% normal discordance and 5% crystals. The presence of relict clinopyroxene suggests that the amphiboles reverse discordance. We do not report the 207Pb/206Pb ages unless the 206Pb/238U have replaced pyroxenes. A whole-rock XRF analysis from this sample
age is older than 500 Ma. We also applied an uncertainty filter where ages (Table 1) indicates a SiO2 concentration of 52 wt% with no detectable K2O
with a 1s uncertainty of >5% were discarded. We obtained additional data on and low TiO2. The classification using the total alkalis versus SiO2 diagram
three samples at the University of Santa Barbara, Laser-Ablation Split-Stream places this rock in the basaltic andesite field. The lack of K2O may result from Dual ICPMS Facility (LASS) using the techniques described by Kylander-Clark hydrothermal alteration. et al. (2013). For samples with data from different laboratories, we report the results of each analytical session separately as well as a combined data set for the purposes of evaluating the maximum depositional age. Sample 02An-34 Cretaceous Intrusions was sampled from near the same locality as sample ELMCH2.6 of Miller et al. (2006), and sample 02An-33 was sampled from near the same locality as sam- Numerous stocks and dikes are present in the South Anyui zone. We dated ple ELMCH3.1b of Miller et al. (2006), so we combined these data sets for some a syenite pluton as well as two dikes that cut deformed Jurassic–Cretaceous of our interpretations. Sample 02An-31 was collected at the same locality as sedimentary rocks in order to constrain the timing of deformation and cleavage sample GB9986 of Bondarenko et al. (2003) and Miller et al. (2008). development in the host rocks. The syenite, known as the Egdegkich pluton (Fig. 4), is from a southern tributary of the Bolshoi Anyui River, to the west of the Aluchin ophiolite Geochemical Analyses (Fig. 3). This pluton cuts Late Jurassic sedimentary rocks. We analyzed zircons from two samples of this pluton using LA-MC-ICP-MS (Table 2). Sample Z321 Geochemical analyses were performed using a Rigaku X-ray fluorescence yielded a weighted mean 238U/206Pb age of 135 ± 4 Ma (Fig. 6A). The other (sam- (XRF) mass spectrometer (major and trace elements) at New Mexico State Uni- ple Z336) yielded a weighted mean age of 144 ± 3 Ma (Fig. 6B). Despite some versity. Samples were crushed with a tungsten carbide shatterbox. Reference overlap on a concordia diagram (Fig. 6C), these mean ages are sufficiently materials (BHVO-1 and BHVO-1P) were measured before and after all unknown different as to indicate they were likely sampled from two separate intrusions, Amato, J.M., Toro, J., Akinin, V.V., Hampton, B.A., Salnikov, A.S., and Tuchkova, M.I., 2015, Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia: A critical component of paleogeographic reconstructions of the Arctic region: Geosphere, v. 11, doi:10.1130/GES01165.1. analyses. Accuracy on major-element concentrations is within 1.1% of estab- even though they were originally mapped as one. A whole-rock XRF analysis lished values. and petrography from one of these samples (Table 1) indicate monzonite to quartz-syenite porphyry composition with Rb, Y, and Nb trace elements, classi- fying it as a volcanic-arc granitoid (Pearce et al., 1984). Point Counts One dike (02An-05) is a fine-grained biotite hornblende granodiorite. It cuts Triassic (Carnian) slates east of the Ustieva River and is located ~5 km east of Point counts were obtained from standard petrographic thin sections that sedimentary sample 02An-04. It has xenoliths of granite that are 5 mm in diam- were cut and stained for plagioclase and potassium feldspar. In total, 14 thin eter. The dike strikes WNW and dips 30° south. It has zircons that are 100–200 sections were analyzed according to the modified Gazzi-Dickinson point-count- by 50 mm with oscillatory zonation and no observed xenocrystic cores. U con- 1Supplemental File. Tables DR1–DR5, with sample ing method (Dickinson, 1970; Ingersoll et al., 1984). Modal composition trends centrations are generally high (1000–2000 ppm), and Th/U ranges from ~0.1 localities, U-Pb data, point-count parameters, and were determined by identifying 400 grains from each thin section. to 0.4 (Table 3). All U-Pb data (n = 10) are concordant, with a weighted mean raw point-count data. Please visit http://dx .doi.org 1 238 206 /10.1130/GES01165 .S1 or the full-text article on The Supplemental File contains sample localities, U-Pb data, point-count U/ Pb age of 100.9 ± 0.8 Ma (mean square of weighted deviates [MSWD] = www.gsapubs.org to view the Supplemental File. parameters, and raw point-count data. 0.5), which excluded two younger outliers (Fig. 6D).
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1539 by guest on 28 September 2021 Research Paper
TABLE 1. WHOLE-ROCK CHEMISTRY AS DETERMINED BY XRF range from euhedral to rounded, with the rounded zircons yielding much older Sample 02An-7 Z336 Z321 ages than the youngest zircons; distinct cores were not observed in any of the youngest crystals. U concentrations of the igneous zircons (n = 7) were Major oxides (wt%) generally low (<200 ppm), resulting in larger uncertainties in 207Pb/235U, though SiO 52.2 58.1 63.7 2 two grains had U concentrations in the ~700–1000 ppm range (Table 3). The TiO2 0.5 0.5 0.5 238U/206Pb ages range from 111 ± 2 Ma to 107 ± 4 Ma, with one outlying grain at Al2O3 16.1 18.0 18.3 115 ± 1 Ma. Discarding the oldest grain yields a weighted mean 238U/206Pb age Fe2O3* 8.9 6.0 3.5 MnO 0.1 0.3 0.1 of 109.3 ± 1.2 Ma with a MSWD of 0.8 (Fig. 6E). There were 10 analyses that MgO 8.0 2.3 1.6 yielded older ages (Table DR4 [see footnote 1]). These include two Middle– CaO 10.8 4.9 1.2 Late Jurassic ages, two Triassic ages, two late Paleozoic ages (Permian and Na2O 3.9 4.5 5.9 Carboniferous), one Cambrian age at 506 Ma, two Proterozoic ages at 1.72 Ga K2Obd 2.7 3.2 and 1.95 Ga, and one Archean age at 2.68 Ga. Xenocryst ages match well with P O 0.1 0.3 0.2 2 5 detrital zircon ages from sample 02An-02 from the host Cretaceous sandstone LOI† 2.7 2.3 1.7 (see following). Total 100.7 99.9 99.9 Trace elements (ppm) Rb bd 56 88 SANDSTONE MODAL COMPOSITION AND DETRITAL Th bd Nb bd 911 ZIRCON GEOCHRONOLOGY RESULTS Sr 182 1196 693 Zr 18 132 194 Compositional trends were determined for sandstone samples collected Y151919 from four Mesozoic stratigraphic units (Fig. 4). Stratigraphic intervals include Pb 11 (1) Middle–Late Triassic, (2) Jurassic, (3) Late Jurassic, and (4) Mid-Cretaceous. Ubd Recalculated data (Table 4) are based on procedures defined by Ingersoll et al. V 210 (1984) and Dickinson (1985). The following provides a summary of modal com- Cr 507 20 30 position trends for each stratigraphic interval; the maximum depositional ages Co 47 of the samples are listed in Table 5. Ni 99 Cu 54 Zn 106 Ga 16 Chukotka Passive Margin Strata (Middle–Late Triassic) Ba 13501090 Note: Whole-rock major element concentrations were determined by The Triassic samples were collected from the region north of the South X-ray fluorescence (XRF) spectroscopy. Sample 02An-7 was processed at Anyui suture zone that has been previously interpreted as the southern pas- New Mexico State University, using a Rigaku ZSX wavelength-dispersive sive margin of Chukotka (e.g., Tuchkova et al., 2009). They are generally spectrograph equipped with an end-window Rh target X-ray tube. Samples fine-grained sandstone and siltstone. Triassic strata (Fig. 7A) are dominated Z336 and Z321 were processed at North-East Interdisciplinary Scientific Research Institute (NEISRI) (Magadan, Russia) using XRF SRM-25 and by quartz with subordinate occurrences of lithic fragments and rare feldspar VRA-30 spectrometers; bd—below detection limits; blanks—not analyzed. (Q 73%, F 7%, L 20%; Fig. 8). The total quartz composition consists primarily *All Fe was calculated as Fe O . 2 3 of monocrystalline quartz (Qm), with subordinate polycrystalline quartz (Qp) †Loss on ignition (LOI) determined by weight loss after heating at 1000 °C for 20 min. and relatively minor amounts of chert (C) (Fig. 7). Feldspar grains are rare, with plagioclase (P) being dominant and potassium feldspar (K) relatively less abundant (Qm 90%, P 8%, K 2%; Fig. 8). Lithic fragments consist primarily of metamorphic (Lm) and sedimentary (Ls) grains, with lithic volcanic fragments The other dike (02An-11) cuts Early Cretaceous sandstone east of the (Lv) making up a relatively smaller overall percentage (Lv 16%, Lm 54%, Ls Ustieva River, and it is located ~3 km from detrital sample 02An-10. The dike 30%; Fig. 8). Lithic metamorphic components are characterized primarily by is vertical, strikes E-W, and is 8 m wide. It has an andesite composition and is phyllite and schist fragments with lesser occurrences of quartzite and gneiss dominated by fine-grained plagioclase and brown hornblende phenocrysts. fragments. Lithic sedimentary fragments consist primarily of mudstone, and The dike has xenoliths 5–10 cm in diameter of a coarser-grained hornblende lithic volcanic fragments are characterized almost entirely by fine-grained vol- diorite. Granite xenoliths were also observed. Sample 02An-11 has zircons that canic groundmass.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1540 by guest on 28 September 2021 Research Paper
TABLE 2. IGNEOUS U/Pb ZIRCON FROM SYENITES USING LA-MC-ICPMS Isotope ratios Apparent ages (Ma) U 206Pb/ 206Pb*/ ±2σ 207Pb*/ ±2σ 206Pb*/ ±2σ Error 206Pb*/ ±2σ 207Pb*/ ±2σ 206Pb*/ ±2σ Best age ±2σ Conc Analysis (ppm) 204Pb U/Th 207Pb* (%) 235U* (%) 238U (%) corr. 238U (Ma) 235U (Ma) 207Pb* (Ma) (Ma) (Ma) (%) Z331 Egdegkich Syenite Pluton Z321_9 135 604 2.2 0.0506 9.49 0.1420 9.86 0.0204 5.39 0.14 130 7 134 12 220 200 130 797 Z321_12 124 650 2.8 0.0540 9.63 0.1550 9.68 0.0208 5.77 0.07 133 7 146 13 350 200 133 791 Z321_11 330 1611 1.7 0.0483 9.32 0.1410 9.93 0.0209 5.26 0.18 133 7 134 12 120 190 133 799 Z321_13 565 3501 1.2 0.0494 9.31 0.1440 9.72 0.0209 5.26 0.15 133 7 136 12 170 200 133 798 Z321_7 159 868 1.7 0.0484 9.50 0.1400 10.00 0.0213 5.63 0.16 136 8 133 12 120 190 136 8 102 Z321_2 157 637 2.0 0.0496 9.68 0.1480 10.14 0.0215 5.58 0.08 1378140 13 180 190 137 898 Z321_8 306 1119 1.2 0.0513 9.36 0.1570 9.55 0.0225 5.33 0.24 144 8 148 13 240 200 144 897 Z336 Egdegkich Syenite Pluton Z336_8 210 1352 1.3 0.0478 9.41 0.1410 9.93 0.0214 5.61 0.15 136 8 134 12 110 190 136 8 102 Z336_19 446 2451 0.9 0.0488 9.43 0.1420 9.86 0.0214 5.61 0.14 136 8 135 12 140 200 136 8 101 Z336_1 191 419 1.3 0.0481 9.36 0.1460 9.59 0.0218 5.50 0.13 139 8 138 13 110 190 139 8 101 Z336_22 362 6618 1.2 0.0493 9.33 0.1500 10.00 0.0222 5.41 0.18 142 8 142 13 160 190 142 8 100 Z336_3 276 1047 1.2 0.0500 9.40 0.1540 9.74 0.0222 5.41 0.27 142 8 146 13 190 200 142 897 Z336_5 163 902 1.5 0.0487 9.45 0.1510 9.93 0.0223 5.38 0.08 142 8 143 13 130 190 142 899 Z336_23 270 2665 1.3 0.0493 9.33 0.1500 10.00 0.0223 5.38 0.15 142 8 142 13 160 190 142 8 100 Z336_17 381 2918 1.3 0.0482 9.34 0.1500 10.00 0.0226 5.75 0.15 144 8 142 13 120 190 144 8 101 Z336_4 345 1381 1.3 0.0481 9.36 0.1510 9.93 0.0226 5.31 0.23 144 8 143 13 100 190 144 8 101 Z336_10 195 810 1.4 0.0479 9.39 0.1520 9.87 0.0230 5.65 0.12 147 8 144 13 100 190 147 8 102 Z336_14 228 1276 1.3 0.0490 9.39 0.1570 9.55 0.0232 5.60 0.10 148 8 148 13 150 190 148 8 100 Z336_11 145 661 1.2 0.0528 9.47 0.1710 9.94 0.0234 5.56 0.25 149 8 160 15 320 200 149 893 Z336_12 100 810 1.8 0.0485 9.90 0.1590 10.06 0.0237 5.49 0.06 151 8 150 14 150 190 151 8 101 Z336_6 150 642 1.7 0.0521 9.60 0.1720 9.88 0.0237 5.49 0.24 151 8 161 15 270 200 151 894 Z336_24 164 1142 1.4 0.0530 10.19 0.1710 10.53 0.0238 5.46 0.32 152 9 159 16 290 200 152 995 Note: Analyses obtained by LA-MC-ICPMS at University of California, Santa Cruz (supervised by Jeremy Hourigan). All uncertainties are 2σ (include errors of measurements only).
Four samples from Triassic sedimentary rocks were analyzed for U-Pb ages Middle Triassic and a relative probability distribution curve with a main peak (Fig. 9A). Sample 02An-34 is a siltstone with slatey cleavage previously mapped at 266 Ma (Fig. 9B), encompassing ages from 290 to 258 Ma, several Paleozoic as Late Triassic–Carnian in age (Dovgal, 1964). The sample is a poorly sorted, peaks including a prominent Silurian peak, and the tallest Precambrian peak at slatey siltstone with angular quartz fragments and detrital muscovite. Our geo- 1890 Ma. When combined with the data from Miller et al. (2006) from a sample chronology data (Table 5; Tables DR2 and DR3 [see footnote 1]) revealed only at the same locality (adding their data [n = 62 after applying our discordance one Triassic grain at 246 Ma (Middle Triassic). When combined with the data and uncertainty filters] for a totaln = 135), the results are similar, yielding a from Miller et al. (2006) from a sample at the same locality (adding their data combined maximum depositional age of 244 ± 3 Ma. [n = 61 after applying our discordance and uncertainty filters] for a total n = Sample 02An-32 was collected from a Late Triassic unit. It is a siltstone with 152), a total of four Triassic grains are present, and these provide a maximum less cleavage than the previous two samples (Fig. 9A). Although the data set depositional age of 248 ± 11 Ma (Fig. 9B). The main peak (Fig. 9B) is at 299 Ma is small (n = 43), sufficient numbers of young zircons (n = 6) were analyzed (Early Permian) and encompasses ages from 310 to 280 Ma. Other prominent to define a maximum depositional age of 225 Ma, which is the same as the peaks are at 381 Ma (Devonian), 442 Ma (Silurian), and 535 Ma (Cambrian). mapped depositional age (Norian), though the uncertainty is high (Fig. 9B). Precambrian grains make up more than half of the total analyses from the The age range of this peak is 230–210 Ma. Other peaks are at 348 Ma (early combined data set, with peaks at 568 Ma, 612 Ma, 832 Ma, and 1.84 Ga. Four Carboniferous), 415 Ma (Early Devonian), and several Proterozoic peaks. There grains are Archean, with the oldest at 3.23 Ga (Fig. 10). are 17 Proterozoic ages and two in the late Archean. Sample 02An-33 was mapped as Late Triassic–Carnian in age, and it has The final Triassic sample (02An-10) was collected from a unit previously detrital zircon ages (n = 69; Fig. 9A) that yield a maximum depositional age of mapped as Lower Cretaceous in the upper Ustieva Valley. It is a fine-grained
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1541 by guest on 28 September 2021 on 28 September 2021 by guest Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf Research Paper plot was not used to calculate the age. MSWD—means square of weighted deviates. represent zircons likely affected by Pb loss. (E) Tera-Wasserburg concordia plot for dike sample 02An-11 with inset showing weighted mean plot; unfilled bar in weighted mean plot for both syenite samples, Z321 in red, Z336 in blue. (D) Tera-Wasserburg concordia plot for dike sample 02An-05 with inset showing weighted mean plot. Dashed ellipses Figure 6. U-Pb zircon dates for intrusive rocks. (A) Weighted mean age for syenite sample Z321. (B) Weighted mean age for syenite sample Z336. (C) Tera-Wasserburg concordia 207Pb/206Pb 0.04 0 0.04 4 0.04 8 0.05 2 0.05 6 D 11 58 0 Granodiorite dike 02An-05: 238U/206Pb Age (Ma) 120 124 128 132 136 140 144 148 152 A 60 10 6 MSWD = 1.3 Mean: 135 ± 4 Ma 62 10 2 23 8 64
U/ 207 206
0.040 0.044 0.048 Pb0.052 / 0.056 Pb 0.060 20 6 98
238 206 C
U/ Pb10 1 Ag10 3 e 10 5 10 7 93 95 97 99 40 Z321: Syenit Pb 66 Z336: Syenit Z321: Syenit MSWD = 0.5 Mean = 100.9 ± 0.8 42 68 94 150 e 44 70 e e 90 23 8 140 46 72 U/ 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 206 E 52 122 48 Pb Andesite dike 02An-11: 238U/206Pb Age 130 B 125 135 145 155 11 54 50 8 MSWD = 1.7 Mean: 144 ± 3 Ma 11 56 4 52 120 11 238 58 0 54 U/
20 6 238 206 10 0 10 4 10 8 12 0
U/ Pb Ag11 e 11 60 106 Z336: Syenit 2 6 Pb MSWD = 0.83 Mean = 109.3 ± 1. 62 102 e 64 2 98 66
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia 1542 Research Paper
TABLE 3. COMPLETE IGNEOUS U/Pb ZIRCON SHRIMP DATA % comm U Th 206Pb/238U age ± 1s 207Pb/206Pb age ± 1s Samplea 206Pbb (ppm) (ppm) Th/U 207Pbc/235U% err 206Pbc/238U% errerr corr.d 207Pbc/206Pbe % err (Ma) (Ma) (Ma) (Ma) Granite Dike, Finish Creek 02AN5-3 <0.01 1127 162 0.14 0.09 3.2 0.0147 1.40.440.0465 2.9941 02AN5-4 0.17 2287 292 0.13 0.10 1.7 0.0148 0.90.520.0490 1.5941 02AN5-2 0.08 1809 218 0.12 0.10 2.5 0.0154 1.80.730.0484 1.7992 02AN5-6 <0.01 672 216 0.32 0.09 7.6 0.0154 2.40.320.0401 7.2 100 2 02AN5-5 <0.01 840 352 0.42 0.10 3.8 0.0156 1.40.350.0442 3.6 100 1 02AN5-7 0.23 1093 202 0.19 0.11 3.8 0.0158 1.10.280.0490 3.6 101 1 02AN5-10 <0.01 1062 417 0.39 0.10 3.2 0.0158 0.70.220.0456 3.1 101 1 02AN5-8 0.31 1067 367 0.34 0.10 4.0 0.0158 1.20.300.0467 3.8 101 1 02AN5-9 <0.01 2216 298 0.13 0.10 2.7 0.0159 0.50.200.0473 2.6 102 1 02AN5-1 0.12 1582 142 0.09 0.11 2.6 0.0160 1.80.710.0484 1.9 102 2 Alkalic Dike, Upper Ustieva River 02AN11-3 3.06 90 24 0.27 0.17 39.0 0.0173 1.00.030.0725 39.0 107 4 02AN11-17 0.56 75 22 0.29 0.06 60.2 0.0164 2.90.050.0248 60.1 108 3 02AN11-16 0.51 11125 0.22 0.1111.6 0.0169 1.10.100.0477 11.5 108 1 02AN11-2 0.36 770 300 0.39 0.12 3.5 0.0173 1.30.370.0491 3.3110 1 02AN11-8 0.97 175 55 0.32 0.11 12.2 0.0173 1.50.120.0473 12.1111 2 02AN11-7 0.27 1030 404 0.39 0.12 4.1 0.0174 1.70.410.0494 3.7111 2 02AN11-13 0.40 127 34 0.27 0.12 10.6 0.0179 1.00.090.0474 10.6115 1 02AN11-15 0.54 275 179 0.65 0.17 4.5 0.0239 1.80.400.0521 4.1 152 3 02AN11-11 <0.01 498 38 0.08 0.16 3.8 0.0263 0.70.170.0452 3.7 169 1 02AN11-9 0.32 104 134 1.29 0.25 8.5 0.0366 1.00.120.0486 8.4 232 2 02AN11-14 0.01 125 103 0.82 0.30 6.7 0.0381 2.00.300.0564 6.4 239 5 02AN11-1 <0.01 263 225 0.85 0.34 3.2 0.0467 0.70.220.0531 3.1 294 2 02AN11-6 0.17 663 361 0.54 0.37 2.2 0.0515 1.00.470.0524 1.9 324 3 02AN11-10 0.44 156 95 0.61 0.62 4.5 0.0814 1.30.290.0554 4.3 506 6 02AN11-12 0.49 175 84 0.48 4.31 1.2 0.2962 0.80.680.1054 0.9 1668 13 1721 16 02AN11-4 0.44 103 34 0.32 5.66 1.3 0.3428 0.90.690.1197 1.0 1893 17 1952 17 02AN11-5 1.71 444 249 0.56 12.37 0.9 0.4904 0.90.940.1829 0.3 2537 24 2679 5 Note: Analyses conducted by sensitive high-resolution ion microprobe (SHRIMP) at the Stanford/U.S. Geological Survey facility. aSee Figure 4 and Table DR1 for sample locations. bCommon Pb component (%) of total 206Pb, determined using measured 204Pb. cRatios corrected for 204Pb. dError Correlation coefficient. e207Pb/206Pb ages only reported for Proterozoic zircons.
sandstone with quartz, plagioclase, microcrystalline chert clasts, and musco- ages ranging from 248 ± 11 Ma to 216 ± 11 Ma, consistent with published paleon- vite. It has a maximum depositional age of 216 Ma (Late Triassic) and a main tological ages for these units (Carnian to Norian). The relatively large uncertain- peak at 307 Ma (late Carboniferous), encompassing ages from 315 to 290 Ma ties arise from the scant number of Triassic zircons in each sample. Out of 528 (Fig. 9A). Other peaks are at 360 Ma (Late Devonian), and 429 Ma (Silurian). Out analyses, only 35 are Triassic or within error of the Permian-Triassic boundary, of all of the analyses (n = 102), there were 28 Proterozoic ages and one Archean with a peak at 247 Ma. The main peaks in the entire data set are at 298 Ma (Early age at 2.58 Ga (Fig. 9A). Because of the lack of Jurassic zircons and the simi- Permian, 33% of the zircons), 440 Ma (Early Silurian, 29%), 808 Ma (Neoprotero- larity in the relative probability plot to the other Triassic samples, we interpret zoic, 10%), 1.15 Ga (Mesoproterozoic, 5%), and 1.85 Ga (Paleoproterozoic, 19%), this rock as having been deposited in Late Triassic time. and a few 2.22 Ga to 3.23 Ga ages (Paleoproterozoic to Archean, 5%). The Pre- Together, our new detrital zircon data combined with those of Miller et al. cambrian-aged zircons from all of the Triassic samples, when plotted together (2006) (Table 5; Fig. 10) indicate that Triassic rocks have maximum depositional (Fig. 11), show a wide range of ages, including grains younger than 1700 Ma.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1543 by guest on 28 September 2021 Research Paper
TABLE 4. RECALCULATED POINT-COUNT DATA Q-F-L % Qm-F-Lt % Qm-P-K %Lv-Lm-Ls % Sample no. and lithology QFLQmF Lt Qm PK Lv Lm Ls Early–Late Cretaceous (South Anyui suture zone) 02An-02 (Medium-grained sandstone) 19 97213107759410 64 27 9 Late Jurassic–Early Cretaceous (South Anyui suture zone) 02An-01 (Medium-grained sandstone) 62 15 23 49 15 36 77 20 3 50 17 33 02An-04 (Medium-grained sandstone) 55 21 24 45 21 34 68 29 3 48 26 26 02An-12 (Very fine-grained sandstone)69922 51 9 40 85 13 2 41 35 24 02An-31 (Medium-grained sandstone) 64 21 15 38 21 41 65 33 2 47 14 39 Jurassic (Oloy Arc) 02An-13 (Medium-grained sandstone) 16 20 64 720 73 26 73 1 73 14 13 02An-14 (Very coarse-grained sandstone) 17 15 68 415 81 22 76 2 77 617 02An-15 (Very coarse-grained sandstone) 19 6 75 5689 45 48 7 81 514 02An-17a (Coarse-grained sandstone) 933 58 333 64 890 2 73 17 10 02An-18 (Very coarse-grained sandstone) 20 21 59 12 21 67 35 64 1 77 7 16 Middle–Late Triassic (Chukotka) 02An-10 (Medium-grained sandstone) 77 7 16 62 7 31 90 8 2 18 38 44 02An-32 (Fine-grained sandstone) 75 9 16 59 9 32 87 11 2 19 44 37 02An-33a (Fine-grained sandstone) 67 6 27 59 6 35 91 8 1 8839 02An-34 (Fine-grained sandstone) 73 5 22 70 5 25 94 5 1 21 50 29
TABLE 5. MAXIMUM DEPOSITIONAL AGES OF SOUTH ANYUI SANDSTONES Maximum depositional age Youngest Age Age N (±2σ) N zircon Sample Locality (previous) (revised) (total) (Ma) MSWD (mean) (Ma)Reference Chukotka: Mid–Late Triassic 02An-34/ELMCH2.6 Bilibino T3 T2 152248 ± 11 1.35 240This study and Miller et al. (2006) 02An-33/ELMCH3.1b Keperveem T3 T2 135244 ± 31.4 11 229This study and Miller et al. (2006) 02An-32 Upper UyamkandaT3T349225 ± 36 9.74 219This study 02An-10 Upper Ustieva K1 T2 132216 ± 11 3.73 212This study Oloy: Mid-Jurassic 02An-18 Upper Orlovka J2 J3 85 164± 11.0 32 163This study South Anyui suture zone: Late Jurassic 02An-01 Upper Ustieva J2–J3 J3 93 156± 31.6 12 150This study 02An-12 Orlovka T3 J3 65 154± 95.5 3150 This study 02An-04 Lower Ustieva T3 J3 132150 ± 41.4 5146 This study 02An-31/GB9986 Upper UyamkandaT3K1160 147± 21.0 6145 This study and Miller et al. (2008) South Anyui suture zone: Mid-Cretaceous 02An-02 Upper Ustieva K1 K1 92 124± 32.0 8118 This study Note: MSWD—mean square of weighted deviates. T2—Middle Triassic; T3—Late Triassic; J2—Middle Jurassic; J3—Late Jurassic; K1—Early Cretaceous.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1544 by guest on 28 September 2021 Research Paper
PPL Chukotka (Middle - Late Triassic) Polarized A H Qm Qm Qm Qm C Qm Qm Lm Qm Qm Qm Qp Qp
Qm Lm 0.2mm Qm Qm Qm C Figure 7. Photomicrographs of Triassic– PPL Oloy ArcJurassi (Middlec Jurassic) Polarized Cretaceous strata from the South Anyui BC P F Qm suture zone (note that photos to the left Lv are in plane-polarized light [PPL] while Lv Qm photos to the right are in polarized light; C Lv scale bar is in the lower right corner P of each plane-polarized light photo). Ag Qm (A) Middle–Late Triassic rocks of the Chu- P Qp kotka margin: Monocrystalline quartz Lv (Qm) together with lithic metamorphic P Lv (Lm) and lithic sedimentary (Ls) frag- C ments are the main constituents of Trias- Lv sic strata; also present is polycrystalline quartz (Qp) and chert (C); (B) Jurassic 0.2mm strata of the Oloy arc: strata consist pri- Lv marily of plagioclase (P) and lithic volcanic PPL South Anyui SutureLate Jurassic Zone (Late - Early Jurassic Cretaceous - Early Cretaceous) Polarized fragments (Lv) with subordinate amounts of monocrystalline quartz (Qm); Also pres- CE Qm ent is augite (Ag). (C) Late Jurassic South C Qp Ls Qp Qm Qp Anyui suture zone (SAZ) strata: Monocrys- Qm talline quartz (Qm) along with subordinate Ls Qm occurrences of plagioclase (P), polycrystal- line quartz (Qp), lithic volcanic (Lv), lithic Qm sedimentary (Ls), and lithic metamorphic Qm fragments (Lm) are the primary constitu- Qm Qm Qp ents of these strata. (D) Mid-Cretaceous Ls SAZ strata: these consist primarily of lithic Qm volcanic fragments (Lv) with subordinate Qm P Qm amounts of monocrystalline quartz (Qm), 0.2mm chert (C), plagioclase (P), serpentine (Sp), Qp and augite (Ag). PPL South AnyuiEarly Suture - Late Zone Cretaceous (mid-Cretaceous) PolarizePolarizedd B Qm Sp DG Lv Lv P P Sp Sp P Ag Qm Lv Qm P C Ag Lv 0.2mm Sp
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1545 by guest on 28 September 2021 Research Paper
Q Qm
Figure 8. Ternary diagrams showing the modal composition of Mesozoic strata Recycled from the South Anyui suture zone. Note orogen Mixed lock - basement the up-section compositional changes b Recycled from Triassic to Cretaceous strata. Middle– orogen Late Triassic and Late Jurassic strata have Dissected Dissected a relative increase in quartz and decrease arc arc Continental in lithic fragments compared to Jurassic Continental block - basement and Mid-Cretaceous strata. Jurassic and Transitional Transitional Mid-Cretaceous strata contain a rela- arc arc Undissected tive increase in lithic volcanic fragments arc compared to Middle–Late Triassic and Late Jurassic strata. Provenance fields of F L FLt Dickinson et al. (1983) suggest mixed-arc Qm Lm and recycled orogen sources for Mesozoic strata of the South Anyui suture zone. Up-section changes in composition sug- gest that precollisional Triassic basins along the northern margin of the suture zone were receiving a larger amount of detritus from recycled orogen sources, whereas precollisional Jurassic basins along the southern margin of the suture zone were receiving detritus primarily from arc source areas. Late Jurassic basins were likely receiving detritus from both recycled orogen and arc source areas, whereas syn- and postcollisional Mid-Cre- taceous basins received contributions from more arc-dominated source areas. Ternary diagram labels: Q—quartz, F— feldspar, L—lithics, Qm—monocrystalline quartz, Lt—total lithics, P—plagioclase, P K Lv Ls K—potassium feldspar, Lm—metamorphic lithics, Lv—volcanic lithics, Ls—sedimen- Mid- Cretaceous South Anyui Suture Zone (n=1) tary lithics. Late Jurassic-Early Cretaceous South Anyui Collisional Suture Zone (n=4) Middle Jurassic Oloy Arc (n=5) Middle-Late Triassic Chukotka Passive Margin (n=4)
Oloy Arc Strata (Middle Jurassic) quartz (Q 16%, F 19%, L 65%; Fig. 8). The total quartz composition consists primarily of chert (C) and monocrystalline quartz (Qm), with rare polycrys- Several samples were collected from the region south of the South Anyui talline quartz (Qp). Feldspar grains are common, with plagioclase (P) being suture zone previously mapped as being from the Alazeya-Oloy fold belt, con- the dominant component (Qm 27%, P 70%, K 3%; Fig. 8). Lithic fragments sisting of volcanic arc and volcanigenic sandstone related to the Oloy arc (e.g., consist primarily of volcanic types (Lv), with lithic sedimentary (Ls) and meta- Sokolov et al., 2009). These Middle Jurassic strata contain elevated abun- morphic (Lm) fragments making up a relatively smaller overall proportion (Lv dances of lithic fragments (Fig. 7B), with subordinate amounts of feldspar and 76%, Lm 10%, Ls 14%; Fig. 8). A majority of lithic volcanic fragments (>75%)
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1546 by guest on 28 September 2021 Research Paper
SAZ: Mid K 02An-02
02An-04 02An-31 SAZ- Late Jurassic/ Figure 9 (on this and following page). Rela Early Cretaceous tive probability spectra for South Anyui 02An-01 sedimentary rocks. Sample 02An-18 is not shown because it does not have any zir- cons older than 200 Ma (see Fig. 9). SAZ— 02An-12 South Anyui suture zone; K—Cretaceous. 02An-10 02An-32 Chukotka: Triassic 02An-33
02An-34 0500 1000 1500 2000 2500 3000
Age (Ma)
are characterized by lathwork volcanic textures (Fig. 7B). Lithic metamorphic fragments and rare occurrences of feldspar (Q 60%, F 19%, L 21%; Fig. 8). The components consist primarily of serpentinite, metachert, and metavolcanic total quartz composition consists primarily of monocrystalline quartz (Qm), fragments. Lithic sedimentary fragments consist primarily of siltstone and with subordinate polycrystalline quartz (Qp) and chert (C; Fig. 8). Feldspar is sandstone. dominated by plagioclase (P) grains, whereas potassium feldspar (K) is rare One sample was dated from the Oloy arc unit. Sample 02An-18 is from a (Qm 70%, P 27%, K 3%; Fig. 8). Lithic fragments consist primarily of lithic vol-
J2-J3 map unit along the Orlovka River that lies in fault contact with Permian ig- canic (Lv) and sedimentary (Ls) grains, with lithic metamorphic fragments neous rocks. It is a quartz-poor volcanic litharenite dominated by intermediate (Lm) making up a relatively smaller overall percentage (Lv 48%, Lm 19%, Ls volcanic (andesite) clasts. Unlike our other samples, there are no pre-Jurassic 33%; Fig. 8). Lithic volcanic fragments are characterized almost entirely by fine- ages. The ages (n = 85; Fig. 9B) form a cluster of three partly overlapping age grained volcanic groundmass. Lithic metamorphic components are character- distributions on a relative probability distribution diagram: one at 164 Ma, a ized primarily by phyllite and schist fragments with lesser quartzite and gneiss second one at 171 Ma, and a smaller peak at 183 Ma. The maximum depo- fragments. Lithic sedimentary fragments consist primarily of mudstone and sitional age is 164 ± 1 Ma, calculated from the 32 youngest zircons. The age sandstone grains. range of the individual analyses is 200–159 Ma. Two samples from units mapped as Jurassic were dated, and three were from a unit previously mapped as Triassic, but all yielded Jurassic maximum depositional ages (Fig. 9B). South Anyui Suture Zone Strata Sample 02An-01 is a fine-grained sandstone from a Middle to Late Jurassic
unit (J2-J3) that overlies Triassic sedimentary rocks in the Ustieva River, a trib- Late Jurassic–Early Cretaceous utary of the upper Orlovka River. It has abundant quartz and plagioclase along with volcanic lithic and chert clasts. Sample 02An-01 has a maximum deposi- This group of samples was collected from the region previously mapped tional age of 156 ± 3 Ma (Late Jurassic, based on a total n = 77; peak ranges as the South Anyui suture zone (e.g., Sokolov et al., 2002). The Late Jurassic from ca. 165 to 145 Ma; Fig. 9B). Prominent peaks are at 282 Ma and 247 Ma strata may also include rocks deposited in the earliest Cretaceous. They have (Fig. 10). There are no ages between ca. 500 Ma and 1.75 Ga (Fig. 9A), and the elevated occurrences of quartz (Fig. 7C), with subordinate occurrences of lithic main Precambrian peaks are at 1.86 Ga and 2.67 Ga.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1547 by guest on 28 September 2021 Research Paper
124
SAZ: Mid K 147 02An-02
150 02An-04 02An-31 154 SAZ- Late Jurassic/ Early Cretaceous 156 02An-01
02An-12 164
Oloy Arc: Middle Jurassic
02An-18 216 02An-10 225 02An-32 244 Chukotka: Triassic 02An-33
248 02An-34 100 200 300 400500 600
Age (Ma)
Figure 9 (continued).
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1548 by guest on 28 September 2021 Research Paper
SAZ-Jurassic-Cretaceous was analyzed multiple times. Although in the original data set (n = 55), there were three Cretaceous zircons, the youngest peak (n = 5) yields a maximum depositional age of 150 Ma (Late Jurassic, with an age range from 163 to 147 Ma; Figs. 9A and 9B). Redating this sample (n = 66) did not yield any zir- cons younger than 150 Ma. Other peaks are at 265 Ma, 291 Ma, and 485 Ma. Proterozoic peaks are at 1.91 Ga and 1.74 Ga (Fig. 9B). A prominent Archean SAZ-Triassic peak is at 2.7 Ga. Sample 02An-31 is from the same locality as sample 9986 of Bondarenko 0500 1000 1500 2000 2500 3000 et al. (2003). It is a fine-grained lithic sandstone with abundant angular quartz, Age (Ma) plagioclase grains, and volcanic lithic clasts. This unit was originally mapped
Figure 10. Relative probability spectra for South Anyui sedimentary rocks highlighting the as T3n (Triassic; Norian) but was remapped as Upper Jurassic–Lower Creta- Phanerozoic ages. SAZ—South Anyui suture zone. ceous turbidites by Bondarenko et al. (2003). Sample 02An-31 has a maxi- mum depositional age, based on 68 detrital zircon U-Pb ages, of 147 Ma, or latest Jurassic, with the peak including ages from 154 to 135 Ma (Figs. 9A and Sample 02An-12 is a fine-grained black siltstone with trace fossils on the 9B). Other peaks are at 164 Ma, 236 Ma, several Paleozoic peaks, a prominent bedding plane that appear to be Planolites. Although this sample was previ- Proterozoic peak at 1.92 Ma, and an Archean peak at 2.73 Ga (Fig. 9A).
ously mapped as Late Triassic (T3k, Carnian), the youngest zircon is 150 Ma, Together, the samples all have maximum depositional ages close to the and five zircons are Jurassic in age, yielding a maximum depositional age Jurassic-Cretaceous boundary, but the actual depositional age could be of 154 ± 9 Ma (Fig. 9B). The main peak of the n = 66 data set is at 265 Ma younger than the maximum depositional age (i.e., in Early Cretaceous time). (Permian, with a range from 275 to 255 Ma), a Triassic peak is present, and Samples 02An-01, 02An-04, 02An-12, and 02An-31 all have Late Jurassic maxi- other prominent peaks are at 609 Ma, 1.07 Ga, and 1.92 Ga (Fig. 9A). Nine mum depositional ages ranging from 156 ± 3 Ma to 147 ± 2 Ma. The main peaks grains are Archean, with the oldest at 2.83 Ga. in the combined data set (Fig. 10) are Late Jurassic (154 Ma), Middle Permian Sample 02An-04 was collected from a unit also mapped as Late Triassic (266 Ma), middle Paleoproterozoic (1.92 Ga), and Neoarchean (2.67 Ga). There (Carnian) west of the Ustieva River (Dovgal, 1964). It is a fine-grained sand- are also minor peaks at 488 Ma and 1.74 Ga. There are few zircons (4 out of 266) stone with quartz, plagioclase, and volcanic lithic fragments. Sample 02An-04 between the 500 Ma and 1.70 Ga range (Fig. 11).
SAZ: Mid-Cretaceous SAZ: Late Jurassic/ Early Cretaceous
Chukotka: Triassic
Figure 11. Relative probability spectra for South Anyui sedimentary rocks combin- ing the data from each age group of sam- ples and highlighting the differences in the Precambrian ages. SAZ—South Anyui suture zone.
8001000120014001600 18002000 2200 2400 26002800 3000 320034003600
Age (Ma)
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1549 by guest on 28 September 2021 Research Paper
Mid-Cretaceous with sandstone that plots in mixed recycled orogen and arc sources (Fig. 8), but they are clearly distinguished from the Middle–Late Triassic strata by their Cretaceous strata of the South Anyui suture zone contain elevated abun- higher content of lithic volcanic fragments. Mid-Cretaceous strata of the South dances of lithic fragments (Fig. 7D) ,with subordinate amounts of feldspar and Anyui suture zone plot with sandstone that overlaps primarily with arc source quartz (Q 19%, F 9%, L 72%; Fig. 8). The total quartz composition consists pri- areas (transitional to undissected; Fig. 8). marily of monocrystalline quartz (Qm) and relatively lower occurrence of poly- crystalline quartz (Qp) and chert (C). Feldspar grains are mostly plagioclase (P), with no occurrences of potassium feldspar (Qm 59%, P 41%, K 0%; Fig. 8). STRUCTURAL GEOLOGY RESULTS Lithic fragments consist primarily of volcanic types (Lv), with lithic metamor- phic (Lm) and lithic sedimentary fragments (Ls) making up a relatively smaller Structural analysis of the South Anyui suture zone is challenging because overall occurrence (Lv 64%, Lm 27%, Ls 9%; Fig. 8). A majority of lithic volcanic of locally intense deformation and the poor outcrop conditions typical of Arc- fragments (>75%) are characterized by lathwork volcanic textures (Fig. 7D). tic regions that escaped Pleistocene glaciations, as is the case in Chukotka, Lithic metamorphic components consist primarily of serpentinite and meta where most outcrops are tundra-covered piles of frost-heaved rock. The faults volcanic fragments, with fewer occurrences of phyllite, schist, quartzite, and postulated to separate the major units from each other are not exposed and metachert. Lithic sedimentary fragments consist primarily of sandstone and generally run through wide valleys with no outcrop. Their presence on geo- mudstone. logic maps is inferred based on changes in lithology, and, as such, details Sample 02An-02 is a lithic sandstone dominated by mafic-intermediate vol- about kinematics on these structures are not available. In this section, we de- canic clasts from a unit previously mapped as Lower Cretaceous (Valanginian: scribe our structural observations from north to south across the South Anyui
Cr1-v) located south of the Jurassic arc rocks. Based on dating of 74 zircons suture zone. (Fig. 9A), it has a maximum depositional age of 124 ± 3 Ma (Aptian; Fig. 9B). The northernmost part of the area (Fig. 4) is dominated by a thick section The main peak from the analyses at 124 Ma is the youngest peak and ranges of Triassic turbidites in the Chukotka fold belt. They are generally metamor- from 132 to 114 Ma, and other peaks are at 150 Ma and 247 Ma. There is a gap phosed to lower-greenschist grade, so that shaley units have well-developed, between 650 Ma and 1.85 Ga. The main Precambrian peak is at 1.93 Ga (Fig. 11). and typically steeply dipping, slatey cleavage, whereas sandstone units pre- serve primary bedding (Tuchkova et al., 2009). These are intruded by numer- ous granitoid plutons of Albian–Aptian age that have been attributed to a Summary of Mesozoic Sedimentary Provenance Trends postcollisional extensional phase (Miller et al., 2009). Intensity of shortening strain generally increases to the south, toward the South Anyui suture, and it Compositional data from Mesozoic strata from along the South Anyui su- is manifest by stronger cleavage development and tighter folding. ture zone indicate some variations in provenance between each of the four Our northernmost detailed structural observations are from Late Jurassic stratigraphic units (Fig. 8). The relative abundance of quartz and lithic frag- and Early Cretaceous rocks in the South Anyui suture zone along the north- ments is similar in Middle–Late Triassic strata of the Chukotka margin (Q 73%, ern Uyamkanda and Ustieva River valleys (sample localities 1–10 and 31–32; F 7%, L 20%) and Late Jurassic strata of the South Anyui suture (Q 60%, F 19%, Fig. 4). In these areas, bedding is predominantly steeply dipping, with an av- L 21%), but these samples are in sharp contrast to Middle Jurassic strata of erage fold axis of 110/03, approximately parallel to the margins of the South the Oloy arc (Q 16%, F 19%, L 65%) and Mid-Cretaceous strata (Q 19%, F 9%, Anyui suture zone (Fig. 12A). Cleavage is steeply south-dipping, suggesting L 72%). It is also noteworthy that the relative abundance of lithic volcanic frag- shortening perpendicular to the suture with a slight component of north-ver- ments is much lower in Middle–Late Triassic strata (Lv 16%) than in the Late gent tectonic transport at the surface (Fig. 12A). The Mid-Cretaceous plutonic Jurassic (Lv 48%) and Middle Jurassic strata (Lv 76%). Lithic metamorphic rocks do not appear to have been involved in the deformation, and thus this fragments in Middle–Late Triassic and Late Jurassic strata consist exclusively shortening predates 117–109 Ma (e.g., Miller et al., 2009). of phyllite, schist, quartzite, and gneiss, whereas Middle Jurassic strata primar- Farther south along the Orlovka and Bolshoi Anyui Rivers (Fig. 4), there ily contain serpentinite, metachert, and metavolcanic fragments. is a separate structural domain in the Oloy terrane where bedding dips more The compositional differences from these strata suggest sediment con- gently, and cleavage, on average, dips to the north (Fig. 12B). It is clear from tributions from at least two distinct source areas. A comparison of our com- the cleavage orientations and fold geometries that the predominant vergence positional data with provenance fields of Dickinson et al. (1983) shows that in this area is to the south. The scatter in the cleavage and bedding data may Middle–Late Triassic Chukotka strata plot with sandstone derived from quartz- be the result of a superimposed folding event about a SW-trending fold axis. rich, recycled orogen source areas, whereas Middle Jurassic Oloy arc strata This axis is not parallel to the regional trend of structures, defined by the unit plot with sandstone that was derived primarily from arc sources (transitional contacts in the central Orlovka River region, but it may have been affected by a to undissected; Fig. 8). Late Jurassic South Anyui suture zone strata overlap late-stage component of right-lateral strike-slip deformation.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1550 by guest on 28 September 2021 Research Paper
A Northern Ustieva and Uyamkanda River Domain 2007). Deep-crustal seismic-reflection, common-depth-point (CDP) data down to 26 s two-way traveltime (TWT), and refraction data were collected. The CDP Bedding Cleavage N= 20 N= 29 data were acquired with a 10 km spread, 50 m geophone spacing, and shots every 100 m. The seismic source was a group of Rusich SV-20-150 MTK-type vi- brators. Observations were carried out by a telemetry system. Data processing included construction of a velocity model for migration and conversion of the time section to depth; various options for the velocity model were tested and in order to reduce the boundary effects of the migration, the amplitude at the edges of the time sections gradually decreases. Despite migration, some dif- fraction effects may still remain. Here, we reinterpret and discuss the segment 1 1 of the CDP line between kilometers 1400 and 1705, which crosses our study area along the valleys of the Pezhenka, Bolshoi Anyui, Angarka, Uyamkanda, and Maly Anyui Rivers (Figs. 3, 4, and 13). The southern part of this line-segment traverses part of the Oloy fold belt (Fig. 3). Between kilometers 1505 and 1570, the line crosses the South Anyui Fold Axis =110/03 Fold Axis= 118/48 Best fit great circle = 200/ 87 W Best fit great circle = 208/ 42W suture zone almost orthogonal to the structural grain, thus offering an excel- lent view of the large-scale structure. From kilometer 1570 to 1705, it traverses B Orlovka and Bolshoi Anyui Domain the Chukotka fold belt, but, because of a bend in the line, it does so obliquely Bedding Cleavage to the trend of the main structures. N= 24 N= 26 Most of this part of the 2DV line (Fig. 13) is characterized by strong re- flectivity in the lower crust, a relatively transparent middle crust, and variable imaging in the upper crust, depending on location. The reflection Moho is visible at ~50 km depth at the southern end, under the Oloy terrane, shallow-
1 ing to ~42 km under Chukotka. The Moho is relatively deep (~46 km) directly south of the South Anyui suture zone and is accompanied by a panel of strong north-dipping reflections at 45–60 km that may represent a fragment of a sub- ducted slab. The most remarkable aspect of the seismic line (Fig. 13) is that the entire South Anyui suture zone, and even some of the area to the south, has strong
1 north-dipping reflections that we interpret as a system of major south-ver- gent thrust faults. North-dipping reflections project to the surface starting at about kilometer 1475 in rocks that have been previously mapped as part of the Fold Axis = 219/04 Fold Axis= 032/62 Best fit great circle = 309/86 Best fit great circle = 122/29 Yarakvaam terrane (Sokolov et al., 2002), which is associated with the Oloy arc and includes the Aluchin ophiolite complex. However, it appears that at least from the structural point of view, this panel of rocks, including the Aluchin Figure 12. Stereonets showing structural data from the South Anyui suture zone. (A) Bedding and cleavage from the northern Ustieva and Uyamkanda River regions. The bedding is folded complex, belongs to the South Anyui accretionary system. Thus, it appears about a shallow ESE-trending axis. Cleavage shows much less scatter but may have also been that the Aluchin complex did not originate within the SAZ, but it was likely folded about a SE-plunging axis. (B) Bedding and cleavage from the Orlovka and Bolshoi Anyui faulted away from the lower plate (i.e., the Kolyma-Omolon–Oloy–Yarakvaam regions. The bedding is folder about a shallow SE-trending axis. Cleavage has been folded about a N-plunging axis. terranes) and incorporated into the upper plate (i.e., SAZ and Chukotka). The bounding fault on the southwest side of the Yarakvaam terrane strikes to the northwest (Figs. 4 and 5) and can be traced on the seismic line 2DV SEISMIC REFLECTION LINE DATA to ~20 km depth, where it is lost in the low-reflectivity middle crust. At ~15 km depth, there is a clear truncation of flat reflectors to the south. The fault that In a major geophysical effort, the 2DV deep geotransect (Fig. 13) was ac- bounds the southern edge of the South Anyui suture zone, which we will quired by the Federal State Unitary Enterprise of the Siberian Science Research call the Angarka fault (Fig. 4), is particularly clearly imaged at kilometer 1505 Institute of Geology, Geophysics, and Mineral Resources across northeastern (Fig. 13). In its upper 8 km, it has a ramp with an apparent dip of 35°N on the Russia from Magadan to the Arctic coast, near Pevek (Fig. 1; Surkov et al., seismic line. Its true dip should be ~50°NW, because the fault is cut by the
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1551 by guest on 28 September 2021 Research Paper
Angarka Fault Aluchin Block South Anyui Zone A (Yarakvaam terrane) Nutesyn Block Distance (km) 1400 1450 1500 1550 1600 1650 1700 K2 Jr3 Ksy Jr2 Jr3 K1 Jr3 Kgd Kgd Tr3 Tr1-2 Tr1-2 Tr3
10 Oloy Terrane Chukotka Microcontinent 10
20 Mid-Crustal Domes 20 Transparent middle crust
Noisy domal 30 30 structure Depth (km) 40 40 Moho Moho 50 50 Slab fragment?
60 60
70 70 Bend Bend Bend Distance (km) B 1400 1450 1500 1550 1600 1650 1700
10 10
20 20
30 30 Depth (km) 40 40
50 50
60 60
70 70
Figure 13. (A) Interpreted and (B) uninterpreted seismic-reflection data from the 2DV seismic line that passes through the South Anyui suture zone. The location of the line is shown on Figures 1, 3, and 4. Along the top of the line, we show the geological units exposed at the surface (Fig. 4). Main structural vergence is to the south in the South Anyui suture zone, based on dominance of north-dipping reflectors. The line is shown with a vertical exaggeration of 4:3. For a high-resolution version of this figure, please visit http://dx.doi.org/10.1130/GES01165.S2 or the full-text article on www.gsapubs.org.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1552 by guest on 28 September 2021 Research Paper
seismic line at an oblique angle (Fig. 4). At a depth of 8–10 km, the Angarka boundary of the South Anyui suture zone. This geometry is best explained if fault flattens along a detachment but has a second ramp that continues to the Triassic South Anyui Ocean (Fig. 14D) was subducted with final closure of perhaps 35 km depth under Chukotka. In spite of the tight folding observed the suture taking place over a north-dipping subduction zone (Fig. 14C); there- at the surface, gently north-dipping reflections underlie much of the South fore, a double-dipping subduction system must have existed in Late Jurassic Anyui suture zone, indicating that the shallow folds are detached. We inter- time (Fig. 14C) to produce the Oloy arc on the Kolyma-Omolon side and Nute- pret a second major fault bounding the block that contains the Nutesyn arc syn arc on the Chukotka side. Sokolov et al. (2002), Nokleberg et al. (2000), rocks (Fig. 4), but this structure is not evident in the seismic data. Instead, the and Shephard et al. (2013) all indicated opposite-dipping subduction zones on upper crust of this part of the South Anyui suture zone is relatively transpar- either side of the South Anyui Ocean. ent, which is not surprising given the tight folding observed at the surface. We agree with previous workers that the Oloy arc is likely a continental The fault that separates the Triassic turbidites of the Chukotka microconti- margin arc, based on its composition and location, but there are uncertain- nent from the South Anyui suture zone rocks is not well imaged either. Gently ties regarding the age, polarity, and exact setting of the Nutesyn arc. Natal’in, north-dipping reflectors in the upper 10 km of the crust are observed in the (1984) and Sokolov et al. (2002) suggested that the Nutesyn arc was built Chukotka block, at least as far north as kilometer 1630, where the line takes directly on Chukotka basement as a continental arc resulting from north-dip- a sharp bend to the east, along the Maly Anyui River. This is evidence that ping subduction. The exposed volcanic rocks in our study area are basaltic north-vergent structures, like those of the South Anyui suture zone, also exist andesite in composition and do not contain any zircon. This is more con- along the southern Chukotka fold belt. The northern end of the line lacks sistent with an island-arc origin, and the lack of any xenocrystic zircon also continuous reflectors in the upper crust but has several prominent domal argues against the arc magmas passing up through Chukotka crust. If it were structures at 15–20 km depth. We are not sure how to interpret them. They an island arc, there must have been a back-arc oceanic basin adjacent to could be thrust-cored anticlines, or perhaps igneous-metamorphic domes re- Chukotka. Along the 2DV seismic line, the Moho lies consistently at ~45 km lated to the numerous Mid-Cretaceous granitic plutons that are found in this depth under Chukotka, but subtracting the underthrusted accreted material area. Alternatively, they could be diffractions from underlying dense struc- leaves a relatively thin southern margin of Chukotka prior to the closure of tures. The lower crust, below the downdip continuation of the Angarka fault, the South Anyui suture, more typical of a passive continental margin than is strongly reflective and has folds with 30 km wavelengths that are out of of an active one. phase with the domal structures observed above them. We interpret this as The final closure of the South Anyui suture zone in Early Cretaceous time further evidence that the upper crust and lower crust of Chukotka are struc- (Fig. 14B) was likely preceded by a collision between the Nutesyn arc and the turally detached from each other. Chukotka margin. During this collision, the back-arc basin was closed. Then, If this interpretation is correct, rocks of the South Anyui suture zone and the Oloy arc and Kolyma-Omolon blocks were accreted, resulting in the preser the Yarakvaam terrane form a wedge ~100 km wide and a maximum of ~20 km vation of some of the ultramafic rocks in the South Anyui suture zone. We thick, which underthrusts Chukotka down to ~25 km depth. The rest of the recognize that some of these mafic-ultramafic rocks may instead represent lower crust, down to the Moho, is likely Oloy arc material, and the true Chu- island-arc basement, but, given their Carboniferous to Triassic radiometric kotka crust is relatively thin (between 35 km and 0) along its southern margin. ages, they would predate both the Nutesyn and Oloy arcs. Because the packages of north-dipping reflectors in the seismic line sole out under the middle crust of Chukotka (Fig. 13), we suggest that the South DISCUSSION Anyui suture zone is actually a relatively low-angle south-vergent thrust sys- tem. This is contrary to previous studies that concluded that the South Anyui Tectonic Model suture zone rocks overthrust Chukotka, based on field observations of these poorly exposed and complexly deformed rocks (Sokolov et al., 2002, 2009). Constraints on the Mesozoic evolution of the South Anyui suture zone in- In a marine seismic-reflection profile of the East Siberian Shelf, located east clude the depositional ages of sedimentary rocks, source rock ages, prove- of the New Siberian Islands and north of the South Anyui suture zone (Fig. 1), nance trends, structural patterns, the position of ophiolitic and arc rocks, and Franke et al. (2008) recognized sets of south-dipping reflectors at 6–10 s TWT, data obtained from the deep crustal 2DV seismic-reflection line (Fig. 13). We which they interpreted as part of a north-vergent thrust wedge associated with combine these data to create a tectonic model (Figs. 14A–14D). closure of the South Anyui suture. This interpretation is consistent with ours: The 2DV deep crustal seismic data suggest that the Chukotka block was The structures observed in the 2DV line are the retrowedge of the collision thrust over the terranes that lie to the south (Fig. 13). The predominant ver- zone, while the structures imaged by Franke et al. (2008) are the prowedge. gence of the orogen is top-to-the-south, as shown by the north dip of the seis- The structures imaged by Franke et al. (2008) are along strike of north-vergent mic reflections across the South Anyui suture zone and into Chukotka. This structures observed on land in the northern part of the Chukotka fold belt (Fig. vergence is consistent with our structural observations close to the southern 14; Katkov et al., 2005; Miller and Verzhbitsky, 2009).
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1553 by guest on 28 September 2021 Research Paper
South North
A. Late Cretaceous Chukchi Okhotsk-Chukotsk Volcanism Regional Extension Borderlands
0
Omolon-Oloy block Chukotka
50
paleo-Pacific slab (subduction into the page)
B. Early Cretaceous Chukotka fold belt Active transform margin Raucha Basin 0
Chukotka Northern Omolon-Oloy block Alaska 50 Figure 14. Tectonic model for the Mesozoic evolution of the South Anyui suture zone. Fig. 13 See text for details. Red—intrusions; Jr— Late Jr Jurassic. C. Late Jurassic Nutesyn Arc South Anyui Ocean Thinned Continental Crust Oloy arc and forearc Jr Volcaniclastics Triassic-Early Jurassic turbidite basin
Omolon basement Chukotka
Thinned Continental Crust D. Late Triassic South Anyui Ocean Turbidite basin
Oloy arc Chukotka
The exact timing of final South Anyui suture zone closure is constrained Depositional Ages and Provenance only broadly. Early Cretaceous sedimentary rocks are deformed within the suture zone, but the main structures are overlapped by relatively un- A comparison between the detrital zircon ages of precollisional Triassic deformed Albian–Cenomanian deposits of the Okhotsk-Chukotka volcanic strata of the Chukotka continental margin and Jurassic–Cretaceous syncolli- belt (Fig. 3). Structures of the Chukotka fold belt, north of the South Anyui sional and postcollisional strata reveals a significant change in the provenance suture zone, are cut by postkinematic plutons that range in age from 117 to record (Figs. 9 and 10). This is not surprising in light of the compositional data 109 Ma (Miller et al., 2009). Two intrusions that we dated within the South discussed here. The Triassic rocks have a broad distribution of Paleozoic zir- Anyui suture zone, at 110 Ma and 101 Ma, likely belong to this category cons with peaks characteristic of the Uralian (late Paleozoic) and Timanian (Fig. 14A). (late Neoproterozoic) orogens of Siberia and Baltica (Fig. 15). They also have Previous workers (Sokolov et al., 2002) have emphasized the role of strike- a lower, but significant, number of Neoproterozoic zircons with ages that are slip deformation during the late stages of the South Anyui suture zone. This common in the Barents region of Baltica, but not in Siberia as strictly defined. interpretation is entirely possible given the oblique plate motions involved in In contrast, the Jurassic–Cretaceous sandstone is distinguished by a major Tri- the closure, but our data do not address this question. assic peak that overlaps with the age of Siberian Trap magmatism, and there
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1554 by guest on 28 September 2021 Research Paper
&
n villian imanian Siberianans-Hudson JurassicUralia ArcsCaledonianT Gren Tr
Indigirka, Moma Basin: L. Jurassic/E. Cretaceous (Toro, unpublished data)
Western Brooks Range: Early Cretaceous (Moore et al., 2015) Jurassic/Cretaceous Samples SASZ-Late Jurassic (this study)
Canada-Sverdrup Basin: Triassic (Omma et al., 2011)
Baltica-Svalbard: Triassic-Lower Jurassic (Pozer Bue and Andresen, 2013)
West Verhoyansk-Triassic (Prokopiev et al., 2008) iassic Samples Tr
Taimyr Peninsula: Triassic (Zhang et al., 2015)
SASZ: Triassic (this study)
0 500 1000 1500 2000 2500 3000 Age (Ma)
Figure 15. Relative probability curves for areas in the Arctic region showing the time spans of significant orogenic events as gray bars. SASZ—South Anyui suture zone.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1555 by guest on 28 September 2021 Research Paper
is a remarkable lack of zircons in the 550–1700 Ma range. We suggest that this sequently, it has become apparent that the gabbro sills that are abundant in gap in the detrital zircon record is one of the fingerprints of Siberian prove- the Lower Triassic strata of Chukotka are also coeval with the Siberian Traps nance. Therefore, closure of the South Anyui suture zone brought about a shift (Ledneva et al., 2011). In addition, Ivanov et al. (2013) noted the presence of from provenance from the west along the axis of Chukotka to provenance from coeval granitic magmatism in Siberia ca. 250 Ma and extending to Late Tri- the south or southwest. We explore these provenance trends in more detail in assic time. Therefore, the Siberian Triassic large igneous province may have the following, compare our data to published data sets from adjacent Arctic encompassed Chukotka and provided local sources for zircons of this age (Fig. regions (Fig. 15), and indicate on paleogeographic maps the likely sources for 16). The 298 Ma peak coincides with the main period of magmatism in the the sediment in the South Anyui suture zone region (Figs. 16–18). Uralian-Taymyr orogen, which formed during the late Paleozoic collision of Si- beria and Baltica (Bea et al., 2002). This peak is dominant in Triassic sandstone Chukotka Triassic Passive-Margin Strata from the Taimyr Peninsula (Zhang et al., 2015) and even in the zircon record of modern river sands from drainages on the east flank of the Urals (Safonova Miller et al. (2006) suggested that the 247 Ma zircon peak in detrital zircon et al., 2010). Devonian zircons, which form a secondary peak in the Triassic ages from Triassic rocks in Chukotka is related to silicic magmatism associated sandstone of Chukotka, could have been derived either from proximal sources, with the Siberian Trap basalts or to silicic stocks on the Taimyr Peninsula. Sub- Devonian plutons exposed along the north coast of Chukotka (Kos’ko et al., 1993; Amato et al., 2014), or more distally from the Urals.
70N Siberian Siberia Traps 180E 140E 100E
rc A Siberia
gal Verk Omolon hoyansk Margin
Uda-Mur
140W Siberian Ver SouthAnyui Ocean khoyansk Ma Traps AZ Uyandina Arc rgin imyr-Uralian Ta 70N Chukotka Omolon imyr Baltica South Anyui Z. Ta Oloy Arc Nutesyn Paleo Pacific Ocean Arc Chukotka n Baltica cea Paleo Pacific Ocean O 100 W KY 50 N ayucham g N Alaska An Sverdrup Basin KY KY North Slope KY Basin Sverdrup Basin Slide Mt. Laurentia Ocean WR 60W 40W 20W Slide Mt. WR Ocean Laurentia Figure 16. Late Triassic (200 Ma) paleogeographic map of the Arctic region based on a GPlates 60W 20W plate tectonic model by J. Toro. (For movie of the model, see Animation 1.). Modern coastlines 1000 km are shown for reference. Stippled areas are major sedimentary basins with black arrows show- ing the provenance directions deduced from the detrital zircon record. Numbered stars are de- Figure 17. Late Jurassic (160 Ma) paleogeographic map of the Arctic region. The oceanic Angayu- trital zircon localities discussed in the text. Volcanoes denote active arcs. KY—Koyukuk terrane, cham and South Anyui terranes are highlighted in purple. See Figure 16 caption for other details WR—Wrangellia terrane, AZ—Alazeya-Oloy arc. and the text for discussion. KY—Koyukuk terrane, WR—Wrangellia terrane.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1556 by guest on 28 September 2021 Research Paper
Animation 1. Arctic plate model from 180 Ma to Present, shown holding North America fixed, created by J. Toro in GPlates by modifying the global model of Seton et al. (2012). The yellow star tracks the location of the Iceland hotspot. Yellow lines are the mid-ocean ridges relevant to the Arctic and some shelf edges. Magnetic anomalies and subduction zones are shown as lines of the color of the plate to which they are attached in the model. Color key: Dark Blue—Kamchatka, Rocky Mountains, Canadian Arctic Islands; Dark Green—Laurentia, Central Ellesmere, South Anyui zone; Dark Grey—Eurasia, Yukon-Tanana, Chukchi Cap; Light Blue—Lower Yukon, Svalbard, Western Europe, Sakhalin; Light Green—Brooks Range; Orange—Prikolyma, North Slope, Seward Peninsula, Baffin Island, Peninsular terrane, Alexander terrane; Pink—Greenland, Lomonosov Ridge, Western Ellesmere, Northwind Ridge; Red—Kolyma-Omolon terrane, Kokukuk arc; Yellow—Chukotka, Eastern Ellesmere. Some of the light grey area are continental shelves. To view the animation, click above in the PDF, or visit http://dx.doi.org/10.1130/GES01165.S3 or the full-text article on www.gsapubs.org.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1557 by guest on 28 September 2021 Research Paper
180E 100E of zircon ages in the 700–1700 Ma range. The first is a peak at ca. 808 Ma, composed of grains with ages from 669 to 914 Ma. We have not identified an Pri-Verkhoyansk obvious source in the Arctic, but these ages are also found in modern sands of Basin Siberia the Ob and Yenisey Rivers of western Siberia (Safonova et al., 2010). The next Verkho yan sk F peak is centered at 1153 Ma, and, although small (5% of the distribution), it is & T important because zircons of this age are common in the Grenville orogen of B e l t Laurentia and Baltica (Rainbird et al., 1992; Mosher, 1998; Tollo et al., 2004; Li 140 W Omolon et al., 2007; Gasser and Andresen, 2013; Pózer Bue and Andresen, 2013), Sever- naya Zemlya (Lorenz et al., 2008), and Novaya Zemlya (Lorenz et al., 2013) but SouthS Anyui Z. 60E Paleo Pacific Ocean are rare in Siberia and are absent from our Late Jurassic samples from the South Anyui suture zone (Fig. 15).
70N Chukotka The last major peak is a broad one at 1850 Ma, composed of zircons rang- ing from 1354 to 2143 Ma. Such a long time span likely represents multiple Baltica magmatic events. Zircons in this range are common in the detrital records of northern Baltica (Fig. 15; Pózer Bue and Andresen, 2013), Siberia (Prokopiev
et al., 2008), and in the Trans-Hudson orogen of Laurentia (Voice et al., 2011). B
ChB 20E
r o Therefore, it is not a particularly diagnostic provenance signature.
o Colville k s Basin In summary, we suggest that the zircon populations in the Triassic rocks R 100W a Amerasia Basin n were derived from a combination of Siberian, Baltica, and perhaps Lauren-
g e tian sources. The Uralian-Taimyr orogen provides the best match (Fig. 15), but there was also a contribution from a Grenville-age source that could have been in Laurentia, or in the Barents region, as was suggested by Lorenz et al. (2013). Our conclusions are consistent with the interpretation of Miller et al. (2006) for Triassic deposits in northern Chukotka (Fig. 15). Laurentia One of the important differences between the detrital zircon ages in our Trias- 60W 20W sic and Late Jurassic samples is that the combined Late Jurassic samples have
Figure 18. Early Cretaceous (120 Ma) paleogeographic map of the Arctic region. ChB—Chukchi few grains between 500 Ma and 1740 Ma. Out of 550 analyses, only nine zircon borderlands. A major transform fault is required to separate Chukotka and Alaska prior to their grains fall in this range (Figs. 8B and 10). Three of those grains are at ca. 650 Ma, juxtaposition shortly after this time period. See Figure 16 caption for other details and the text and all of the others are isolated single grains that do not form a peak. Siberian for discussion. F&T—fold-and-thrust. basement ages are typically either 2100–1850 Ma or >2300 Ma (Frost et al., 1998). The main Paleoproterozoic peak in Triassic rocks is at 1850 Ma, whereas in Late The 440 Ma peak, which is the second most prominent one in the Triassic Jurassic rocks, it is at 1920 Ma. The older Paleoproterozoic peaks are at 2485 Ma sandstone, is made up of zircons ranging from 404 to 662 Ma, and it includes in Triassic rocks and 2690 Ma in the Late Jurassic rocks (Fig. 11). These Paleo several secondary peaks (Fig. 9). This range of ages corresponds to early Paleo proterozoic peaks are sufficiently different in Triassic and Late Jurassic samples zoic magmatism in the Uralian and the Caledonian orogens (Fig. 15) and to the to conclude that they do not represent the same source region. late Neoproterozoic Timanian orogen of northeastern Baltica and the Barents Shelf (Gee and Pease, 2004). The Caledonian-age peak is more prominent in Oloy Arc Strata the Triassic of Chukotka than in samples from the Taimyr Peninsula, indicating a more significant input of detritus from the Barents Shelf region (Fig. 15). Late The detrital zircon age pattern of sample 02An-18 contrasts with the rest Neoproterozoic zircons are important because magmatism of this age is rare of our data set in that it yielded only Jurassic 238U/206Pb ages (Fig. 10). This in Laurentia. For example, Timanian-age zircons are almost absent in samples sample was collected south of the South Anyui suture zone in rocks that are from the Sverdrup Basin of the Canadian Arctic (Fig. 15; Omma et al., 2011) and considered to be part of the Yarakvaam terrane overlapped by volcanic and are only a minor component of the detrital record from Svalbard (Pózer Bue volcaniclastic rocks of the Oloy arc (e.g., Parfenov et al., 1993; Nokleberg et al., and Andresen, 2013), but they are prominent in the Taimyr Peninsula (Zhang 1994). The narrow range of detrital zircon ages in the Jurassic sandstone, com- et al., 2015). bined with evidence for volcanic clasts, strongly suggests a local provenance Unlike typical detrital zircon populations from eastern Siberia and the Verk- for this sandstone from the Oloy arc region, and that significant magmatism in hoyansk orogen, the Chukotka Triassic sandstone has several significant peaks the Oloy arc spanned the period 190–160 Ma.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1558 by guest on 28 September 2021 Research Paper
South Anyui Suture Zone Strata (Late Jurassic–Early Cretaceous) were progressively cut off from Chukotka. On the other hand, the Cretaceous sample has three grains at 517 Ma to 651 Ma, a time period that is not repre- We interpret the youngest peak in the Late Jurassic sandstone (154 Ma) sented in the Jurassic samples, but both the Cretaceous and Jurassic samples as the product of the Late Jurassic Nutesyn arc (Natal’in, 1984), which devel- share broad peaks typical of Siberian basement at ca. 1.92 Ga and 2.5–2.7 Ga. oped close to the Chukotka margin prior to closure of the South Anyui suture We suggest that by Mid-Cretaceous time, the collision of Chukotka with the (Nokleberg et al., 2000; Shephard et al., 2013). If this is correct, this peak on Kolyma-Omolon block was complete, and subsequent precursors to the the age distribution provides a good estimate of the age of Nutesyn arc mag- Okhotsk-Chukotka volcanic belt (120 Ma Tytylveem unit; Akinin and Miller, matism. Alternative, more distal, sources for these Late Jurassic zircons are 2011) could have contributed the Aptian or later sandstone unit represented the extensive Main plutonic belt and Uyandina-Yasachnaya arc of the western by sample 02An-02. Kolyma-Omolon block, which developed prior to its collision with the Verk It is also worth mentioning that the Jurassic–Cretaceous detrital zircon hoyansk margin of Siberia (Fig. 1; Akinin et al., 2009). signature of the South Anyui suture zone sandstone is remarkably similar to There is a significant group of Permian–Triassic zircons in the Late Ju- that of Late Jurassic sandstone from the Indigirka River, in the Moma Basin, rassic sandstone of the South Anyui suture zone, which may have been located 1000 km west within the Kolyma-Omolon terrane (Fig. 15), to that of sourced either directly from the Siberian Traps large igneous province, or Jurassic–Cretaceous sandstone of the Rauch foreland basin on the north side indirectly by recycling of the Triassic rocks of Chukotka. If recycling of the of the Chukotka fold belt, and to the Stolbovoskaya Formation of the New Sibe- Triassic were a significant source, we would expect to see some contribution rian Islands (Miller et al., 2008). Thus, it appears that the Jurassic–Cretaceous of early Paleozoic and Neoproterozoic grains, but these are either not prom- depositional system associated with the South Anyui–Chukotka orogen was inent, or are entirely absent from Late Jurassic sandstone. Instead, the age extensive. In contrast, the provenance signature for Early Cretaceous sand- gap in the zircon ages between 500 and 1700 Ma is characteristic of Mesozoic stone from the foreland basin associated with the Brooks Range orogen of sedimentary rocks from the Verkhoyansk margin of Siberia (Prokopiev et al., Alaska has greater similarity with the Triassic of Chukotka and is inferred to 2008) and along the western edge of the Kolyma-Omolon block (Harris et al., have been sourced by recycling of Triassic deposits uplifted in the Chukotka 2013) and in the Jurassic of the Indigirka River, in the Moma Basin (Fig. 15). fold belt (Moore et al., 2015). This leads us to believe that a southern source from the Kolyma-Omolon block is likely for the South Anyui Late Jurassic sandstone. These rocks were Summary of Provenance deposited when the Jurassic arcs were active and thus probably before the collision between the Kolyma-Omolon and Chukotka blocks, and this colli- During the earliest stage of Middle–Late Triassic basin development on sion would have shut off arc magmatism. However, the two blocks may have Chukotka, strata were most likely derived from quartz-rich, recycled orogen been relatively close to each other before the collision, and thus either block sources from the Uralian-Taimyr region, with a contribution from the Siberian could have been a sediment source for the sandstone. The Omolon block Trap large igneous province and a Grenville-age source, likely on what today has Precambrian sources with ages similar to the main peaks in this unit, is the Barents Shelf (Fig. 15). By Jurassic time, oceanic arc source areas to the namely 3.2 Ga (minor), 2.6 Ga, and 2.0–1.8 Ga (Akinin and Zhulanova, 2015). south of Chukotka were being exhumed and were contributing arc detritus as Thus, a Kolyma-Omolon source for the Late Jurassic–Early Cretaceous strata well as serpentinite and chert/metachert. The Late Jurassic–Early Cretaceous is possible. Period marked a transition in which detrital contributions most likely involved both recycled orogen sources of the emerging South Anyui–Chukotka conver- South Anyui Suture Zone Strata (Early Cretaceous) gent orogen and Jurassic arc components. The detrital zircon spectra are typ- ical of Jurassic–Cretaceous deposits in the Kolyma-Omolon and Verkhoyansk Sample (02An-02), with a Mid-Cretaceous maximum depositional age of areas. Strata of this age likely record exhumation and synorogenic sedimen- 124 ± 3 Ma, defined by six zircons (8% of the sample), has a similar rela- tation associated with arc-continent collision along the southern margin of tive probability age spectrum as the samples with Late Jurassic maximum Chukotka. Mid-Cretaceous sedimentation likely records regional exhumation depositional ages, although with only 74 zircon ages in this sample, it is dif- across the South Anyui suture zone, resulting in a combination of arc, oceanic, ficult to evaluate the significance of small peaks present in the larger Late and continental sources. Jurassic data set (Fig. 10). Aside from the Cretaceous ages, they have nearly identical peaks to the Late Jurassic samples at 164 Ma, 247 Ma, and 267 Ma. Paleogeographic Reconstructions The Jurassic samples, though, have 45 grains with ages between 300 and 500 Ma (~10%), and these ages are lacking in the Cretaceous sample. It ap- We have created an animated plate model for the Mesozoic–Cenozoic evo- pears that from Triassic to Cretaceous time, the sources contributing early lution of the Arctic using GPlates software and incorporating the ideas outlined Paleozoic zircons, which we attributed to the Uralian and Caledonian orogens, herein together with further data from the Arctic region. The maps shown in
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1559 by guest on 28 September 2021 Research Paper
Figures 16–18 are stills from Animation 1. The new Arctic plate model was built through the Jurassic. Early Cretaceous (144 Ma and 136 Ma) monzonites and a on the global model of Seton et al. (2012). Some of the goals of our model quartz syenite porphyry, collected west of the Aluchin complex, which intruded were to solve the space problem associated with restoring Chukotka and Arctic rocks attributed to the Oloy arc, might be related to the latest stages of the Oloy Alaska to their pre-Cretaceous positions, allow for accretion of arcs along the arc magmatism, the age range of which is not well constrained. In our tectonic current southern margins of both blocks, achieve a kinematically viable open- model (Figs. 16 and 17), the closure of the South Anyui Ocean is primarily ing of the Amerasia Basin by rifting, and honor the available geological and driven by the accretion of the Kolyma-Omolon block, including the arc terranes geophysical data. We treated the Kolyma-Omolon block in a manner similar to that surrounded it, to the Siberia and Chukotka margin. This is in contrast to that proposed by Nokleberg et al. (2000). most other models (Zonenshain et al., 1990; Nokleberg et al., 2000; Lawver The provenance signatures place Chukotka in the Triassic adjacent to the et al., 2002; Shephard et al., 2013), which use the opening of the Amerasian Taimyr Peninsula (Fig. 16). At that time, southern Chukotka was blanketed by a Basin to drive the closure of the South Anyui Ocean. passive-margin succession that resulted in widespread deposition of Middle– The South Anyui suture zone has long been assumed to be the western Late Triassic turbidites. Their petrology indicates a source rich in quartz, meta- extension of the Angayucham suture in Alaska (e.g., Churkin and Trexler, 1981; morphic lithics including phyllite, schist, quartzite, gneiss, and lesser volcanic Nokleberg et al., 2000; Amato et al., 2004). However, the seismic data (Fig. lithic fragments. The Siberian Traps large igneous province is the most likely 13) indicate that the closure of the South Anyui Ocean and collision between candidate for Triassic ages. The abundance of Paleozoic and late Neoprotero- Chukotka and the Kolyma-Omolon blocks to the south were south vergent, zoic zircons points to the Uralian-Taimyr orogen as a likely source. Thus, Chu- likely above a north-dipping subduction zone on the Chukotka side, whereas kotka was likely part of Baltica, and the South Anyui Ocean can be viewed as a the closure of the Angayucham Ocean in Alaska was north vergent above a remnant of the Uralian Ocean. In our plate model (Fig. 16), we locate Chukotka south-dipping subduction zone. This raises questions about not only the cor- in a position relative to Eurasia similar to where it is today. This allows enough relation between the Angayucham terrane and the South Anyui suture zone, space for accretion of the Kolyma-Omolon block to Siberia and permits a sim- but also between the Koyukuk arc of Alaska and the Nutesyn arc of Russia. Fur- ple rotation of northern Alaska during opening of the Arctic. This is in con- thermore, in our model, we also challenge the assumption that Arctic Alaska trast to models that call for a large-magnitude clockwise rotation of Chukotka and Chukotka had a shared history throughout the Mesozoic. We believe that during Arctic opening, all of which have the problem of restoring Chukotka it is only in Early Cretaceous time, during the opening of the Amerasia Basin, outboard of the Verkhoyansk margin, making it difficult for the accretion of that Arctic Alaska came in contact with Chukotka (Fig. 18). As Arctic Alaska the Kolyma-Omolon block to take place, and requiring complicated “double rifted away from the Canadian Arctic margin and rotated in a counterclock- windshield-wiper” kinematics for Arctic opening (e.g., Miller et al., 2006). Our wise direction, the present-day northern margin of Chukotka was reactivated model is also different from that of Shephard et al. (2013), who attempted to as a dextral transform. Discussion of the details of Amerasia Basin opening solve the space problem by placing Chukotka outboard of northern Alaska are beyond the scope of the present paper, but they can be seen in Animation prior to Arctic opening. That position of Chukotka conflicts with the history of 1. The proximity of Arctic Alaska to Chukotka starting in the Early Cretaceous high-pressure metamorphism and emplacement of ophiolites in the Brooks is required by the detrital zircon provenance signature of Colville Basin sand- Range and Seward Peninsula of Alaska. stone, which is clearly derived from the west and has strong similarities to the One of the implications of our model is that prior to the late Mesozoic ac- Triassic of Chukotka (Moore et al., 2015). cretion and rifting episode, Chukotka was a peninsula located along-strike of the Uralian-Taimyr orogen with marine basins on both sides (the Angayucham Ocean to the north, and the South Anyui Ocean to the south, in modern coor- CONCLUSIONS dinates). This configuration has similarities with the modern Malay Peninsula and the adjacent Sunda Shelf, where rapid sedimentation, sourced from the The South Anyui suture zone exposes multiple mafic/ultramafic complexes Himalayan orogen and fed through the Mekong Delta (Wang et al., 2014), is within a zone of accretion separating the Kolyma-Omolon block and the asso taking place much like the Triassic basins of Chukotka. Our model predicts that ciated Oloy arc from the Chukotka block and associated Nutesyn arc. The during Triassic through Early Cretaceous time, the northern margin of Chu- mafic/ultramafic complexes may represent island-arc basement or oceanic kotka (in modern coordinates) was a sinistral transform margin that allowed crust from the South Anyui Ocean. This ocean basin initiated as early as the for accretion of the Koyukuk arc to northern Alaska (Figs. 16 and 17). There is late Paleozoic, based on dates from subduction-related island-arc ultramafic little direct geological information about the nature of this margin in the Meso rocks (Ganelin et al., 2013; Sokolov et al., 2015), and prior to 164 Ma, based on zoic, as it is now buried under an immense thickness of Late Cretaceous and U-Pb ages of zircons from Jurassic arcs that indicate subduction of oceanic Cenozoic sediments (Lineva et al., 2015). lithosphere was occurring. The collision formed the Chukotka and Oloy-Ala- Our detrital zircon data from Oloy volcanogenic sandstone provide evi zeya fold belts, deformed rocks in the suture zone, and possibly exhumed dence for volcanism along the southern margin of the South Anyui Ocean some of the mafic/ultramafic complexes.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1560 by guest on 28 September 2021 Research Paper
We used U-Pb ages of detrital zircons from Mesozoic sandstone to help tion, we propose that Chukotka may have been a separate block from Arctic constrain the main phases of deposition in the South Anyui suture zone. These Alaska until the opening of the Canada Basin and counterclockwise rotation of include four groups: (1) quartz-rich, passive continental margin Triassic sand- Alaska in Early Cretaceous time. stone of Chukotka with sparse Triassic zircons yielding maximum depositional ages ranging from 240 to 212 Ma; (2) volcanogenic sandstone likely derived only from the Oloy arc with a narrow zircon age range with peaks at 164 Ma, ACKNOWLEDGMENTS 171 Ma, and 184 Ma; (3) sandstone within the South Anyui suture zone with Samples were collected by Amato, Akinin, and Tuchkova during 3 weeks of field work during the Late Jurassic maximum depositional ages and abundant volcanic lithic frag- summer of 2002 in an expedition organized and led by Sergey Sokolov (Geological Institute, Rus- ments; and (4) potentially post- or syncollisional sandstone with maximum sian Academy of Sciences, Moscow). Funding for field work was provided by Stanford University Gift Funds to Elizabeth Miller, and she is gratefully acknowledged for this project, as without her depositional ages of 124 Ma. The Triassic rocks have provenance signatures initiative and financial assistance, this study would not have been possible. Detrital zircon analy that link them to the Uralian-Taimyr orogen and the Barents Shelf, whereas the ses were subsidized by BP through a grant to Jaime Toro, who constructed the GPlates model Late Jurassic and Cretaceous sandstone has characteristic signatures of the presented here. We particularly thank Steve Mathews and Alexey Guryanov of BP. Geochronology research of Akinin was supported in part by grant DVO RAN 15-I-1-008. Marianna Tuchkova wishes Siberian Verkhoyansk margin or the Kolyma-Omolon block. to state that she did not participate in the creation of the tectonic models presented here. Field Point-count compositional data indicate that Triassic sedimentary rocks assistance was provided by Sergei Katkov and Dmitri Gribkov. Alex Kozhevnikov collected the are much more quartz-rich compared to Jurassic–Cretaceous sandstone (73% samples from the Egdegkich pluton. Peter Druschke identified the trace fossil. George Gehrels and the staff at the Arizona LaserChron Center helped acquire detrital zircon data, and the labora- vs. 16%) and have more lithic metamorphic and sedimentary fragments. The tory was supported by National Science Foundation grant EAR-1338583. Brad Hacker and Andrew metamorphic lithic fragments are dominantly quartzite phyllite, schist, and Kylander-Clark graciously provided some of the zircon U-Pb ages. Sensitive high-resolution ion gneiss. This is consistent with the Triassic sedimentary rocks having a recycled microprobe (SHRIMP) analyses were facilitated by Joe Wooden and the staff at the Stanford–U.S. Geological Survey facility. Matt Coble and Eric Gottlieb at Stanford re-reduced the SHRIMP data orogen source. The Late Jurassic–Early Cretaceous strata have dominantly using Squid 2.0. Constructive reviews by Tom Moore, an anonymous reviewer, and Associate arc sources mixed with a recycled orogen source. The youngest unit dated, Editor Todd LaMaskin greatly improved the manuscript. the <124 Ma late Early Cretaceous sandstone, has a dominantly arc source. The metamorphic fragments in the Jurassic and Cretaceous units include ser- pentinite, metachert, and metavolcanic clasts. REFERENCES CITED Structural analysis indicates bedding in Jurassic and Cretaceous rocks near Afizkiy, A.I., 1970, Biostratigraphy of Triassic and Jurassic sediments of Bolshoi Anyui River Basin the South Anyui suture zone is folded about a gently plunging axis trending (Western Chukotka): Moscow, Nauka, 146 p. [in Russian]. ESE (110°), approximately parallel to the trend of the suture. Cleavage dips Akinin, V.V., and Miller, E.L., 2011, Evolution of calc-alkaline magmas of the Okhotsk–Chukotka volcanic belt: Petrology, v. 19, p. 237–277, doi:10.1134 /S0869591111020020 . steeply to the south, indicating shortening perpendicular to the suture with Akinin, V.V., and Zhulanova, I.L., 2015, Age and geochemistry of zircons from oldest metamorphic a component of north vergence, but farther south in the South Anyui suture rocks of Omolon massif (north-east Russia): Geochemistry International (in press). zone, the primary vergence is to the south. Scatter in structural data may be Akinin, V.V., Prokopiev, A.V., Toro, J., Miller, E.L., Wooden, J., Goryachev, N.A., Alshevsky, A.V., Bakharev, A.G., and Trunilina, V.A., 2009, U-Pb SHRIMP ages of granitoids from the main related to postcollisional, dextral strike-slip deformation, consistent with the batholith belt (north east Asia): Doklady Earth Sciences, v. 426, p. 605–610, doi:10 .1134 model of Sokolov et al. (2002) to explain the trends of mafic/ultramafic com- /S1028334X09040217. plexes that are not parallel to the suture. Akinin, V.V., Andronikov, A.V., Mukasa, S.B., and Miller, E.L., 2013, Cretaceous lower crust of the continental margins of the northern Pacific: Petrological and geochronological data on lower We have interpreted a portion of the 2DV seismic-reflection line that runs to middle crustal xenoliths: Petrology, v. 21, p. 28–65. through the South Anyui suture zone in the field area (Surkov et al., 2007; Amato, J.M., Toro, J., and Moore, T.E., 2004, Origin of the Bering Sea salient, in Sussman, A., and Goryachev et al., 2008) to establish the crustal-scale architecture of the system Weil, A., eds., Orogenic Curvature: Integrating Paleomagnetic and Structural Analyses: Geo- logical Society of America Special Paper 383, p. 131–144. and use it to support a new tectonic model. We infer that the Kolyma-Omolon- Amato, J.M., Aleinikoff, J.N., Akinin, V.V., McClelland, W.C., and Toro, J., 2014, Age, chemistry, Oloy block was subducted beneath the Chukotka block during the collision that and correlations of Neoproterozoic–Devonian igneous rocks of the Arctic Alaska–Chukotka ter- formed the South Anyui suture zone, in agreement with the interpretation of rane: An overview with new U-Pb ages, in Till, A.B., and Dumoulin, J.A., eds., Reconstruction Goryachev et al. (2008). In this model, the South Anyui zone consists mainly of a Late Proterozoic to Devonian Continental Margin Succession, Northern Alaska, its Paleo- geographic Significance, and Contained Base-Metal Sulfide Deposits: Geological Society of of deformed sedimentary rocks with minor volumes of exposed mafic/ultra- America Special Paper 506, p. 29–58, doi:10 .1130 /2014 .2506 . mafic complexes that relate to either arc basement (of the Oloy and/or Nutesyn Bea, F., Fershtater, G.B., and Montero, P., 2002, Granitoids of the Uralides: Implications for the arcs) or oceanic crust from the South Anyui Ocean. Prior to the collision, the evolution of the orogen, in Brown, D., Juhlin, C., and Puchkov, V., eds., Mountain Building in the Uralides: Pangea to the Present: American Geophysical Union Geophysical Monograph South Anyui Ocean had subduction zones on both sides, creating the Oloy arc 132, p. 211–232. adjacent to the Omolon block and the Nutesyn arc offshore of the Chukotka Black, L.P., Kamo, S.L., Allen, C.M., Davis, D.W., Aleinikoff, J.N., Valley, J.W., Mundil, R., Camp- 206 238 margin. The south vergence of the South Anyui suture zone is the opposite of bell, I.H., Korsch, R.J., Williams, I.S., and Foudoulis, C., 2004, Improved Pb/ U microprobe geochronology by the monitoring of a trace-element related matrix effect; SHRIMP, ID-TIMS, the Brooks Range fold-and-thrust belt, and thus the South Anyui suture zone ELA-ICP-MS and oxygen isotope documentation for a series of zircon standards: Chemical should not be directly correlated to the Angayucham suture of Alaska. In addi Geology, v. 205, p. 115–140, doi:10 .1016 /j .chemgeo .2004 .01 .003 .
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1561 by guest on 28 September 2021 Research Paper
Bondarenko, G.E., 2004, Tectonics and Geodynamic Evolution of the Mesozoides of Northern Cir- Gorodinski, M.E., 1980, Geologic Map of Northeastern Russia: Ministry of Geology USSR: Lenin- cum-Pacific [Ph.D. dissertation]: Moscow, Moscow State University, 400 p. [in Russian]. grad, VSEGEI, scale 1:1,500,000. Bondarenko, G.E., Soloviev, A.V., Tuchkova, M.I., Garver, J.I., and Podgornyi, I.I., 2003, Age of de- Goryachev, N.A., Byalobzhesky, S.G., Salnikov, A.S., Akinin, V.V., and Miller, E.L., 2008, Crustal trital zircons from sandstones of the Mesozoic flysch formation in the South Anyui suture structure of Cretaceous accretionary orogenic belts of north-eastern Asia based on data from zone (western Chukotka): Lithology and Mineral Resources, v. 38, p. 162–176, doi:10 .1023 /A: the 2DV geophysical transect: Eos (Transactions of the American Geophysical Union), v. 89, 1023456126348. Fall Meeting supplement, abstract T13B–1945. Bychkov, Yu.M., 1994a, Structure-Facies Zonation and Biostratigraphy of the Triassic Deposits of Grantz, A., May, S.D., and Hart, P.E., 1990, Geology of the Arctic continental margin of Alaska, in Chukotka: Magadan, Russia, SVKNII DVO RAN [in Russian]. Grantz, A., Johnson, L., and Sweeney, J.F., eds., The Arctic Ocean Region: Boulder, Colorado, Bychkov, Yu.M., 1994b, Triassic Deposits of Northeast Russia: Magadan, Russia, SVKNII DVO RAS Geological Society of America, Geology of North America, v. L, p. 257–288. [in Russian]. Gulevitch, V.V., 1968, Geological Map of USSR, Eropol Series, Sheet Q-58-XV, XVI: Magadan, Rus- Bychkov, Yu.M., and Solov’yov, G.I., 1992, New Data on the Stratigraphy and Lithology of Triassic sia, MINGEO USSR, scale 1:200,000 [in Russian]. Sediments in the Upper Reaches of the Bol’shoi Anyui River, Lower Mesozoic Deposits of Harris, D.B., Toro, J., and Prokopiev, A.V., 2013, Detrital zircon U-Pb geochronology of Mesozoic the Right Side of the Kolyma River and Northwestern Kamchatka: Magadan, Russia, Severo- sandstones from the Lower Yana River, northern Russia: Lithosphere, v. 5, p. 98–108. Vostochnyi Kompleksnyi Nauchno-Issledovatel’skyi Institut Rossiyiskoi Akademii Nauk, Ingersoll, R.V., Ballard, T.F., Ford, R.L., Grimm, J.P., Pickle, J.D., and Sares, S.W., 1984, The effect of p. 3–24 [in Russian]. grain size on detrital modes: A test of the Gazzi-Dickinson point-counting method: Journal Chasovitin, M.D., and Shpetnyi, A.P., 1964, Geological Map of USSR, Anyuisko-Chaunskaya Series, of Sedimentary Petrology, v. 54, p. 103–116. Sheet R-58-XXXIII, XXXIV: Magadan, Russia, MINGEO USSR, scale 1:200,000 [in Russian]. Ivanov, A.V., He, H., Yan, L., Ryabov, V., Shevko, A., Palesskii, S.V., and Nikolaeva, I.V., 2013, Siberian Churkin, M., Jr., and Trexler, J.H., Jr., 1981, Continental plates and accreted oceanic terranes in the Traps large igneous province: Evidence for two flood basalt pulses around the Permo-Triassic Arctic, in Nairn, A.E.M., Churkin, M., Jr., and Stehli, F.G., eds., The Arctic Ocean: New York, boundary and in the Middle Triassic, and contemporaneous granitic magmatism: Earth-Sci- Springer Verlag, p. 1–20. ence Reviews, v. 122, p. 58–76, doi:10 .1016 /j .earscirev .2013 .04 .001 . Dickinson, W.R., 1970, Interpreting provenance relations from detrital modes of greywacke and Katkov, S.M., Strickland, A., Miller, E.L. Podgorny, I.I., and Toro, J., 2005, Dating deformation in the arkose: Journal of Sedimentary Petrology, v. 40, p. 695–707. Anyui-Chukotka fold belt, northeastern Arctic Russia: Eos (Transactions, American Geophysi- Dickinson, W.R., 1985, Intepreting provenance relations from detrital modes of sandstones, in cal Union), v. 86, no. 52, abstract T11B-0378. Zuffa, G.G., ed., Provenance of Arenites: Dordrecht, The Netherlands, D. Reidel Publishing Klemperer, S.L., Greninger, M.L., and Nokleberg, W.J., 2002, Geographic information systems Co., p. 333–361. compilation of geophysical, geologic, and tectonic data for the Bering Shelf, Chukchi Sea, Dickinson, W.R., Beard, L.S., Brakenridge, G.R., Erjavec, J.L., Ferguson, R.C., Inman, K.F., Knepp, Arctic margin, and adjacent landmasses, in Miller, E.L., Grantz, A., and Klemperer, S.L., eds., R.A., Lindberg, F.A., and Ryberg, P.T., 1983, Provenance of North American Phanerozoic sand- Tectonic Evolution of the Bering Shelf–Chukchi Sea–Arctic Margin and Adjacent Landmasses: stones in relation to tectonic setting: Geological Society of America Bulletin, v. 94, p. 222–235, Geological Society of America Special Paper 360, p. 359–374. doi:10 .1130 /0016 -7606 (1983)94 <222: PONAPS>2 .0 .CO;2 . Kos’ko, M.K., Cecile, M.P., Harrison, J.C., Ganelin, V.G., Khandoshko, N.V., and Lopatin, B.G., 1993, Dovgal, Yu.M., 1964. Geological Map of USSR, Anyuisko-Chaunskaya Series, Sheet Q-58-IX, X: Geology of Wrangel Island, between Chukchi and East Siberian Seas, Northeastern Russia: Magadan, Russia, MINGEO USSR, scale 1:200,000 [in Russian]. Geological Survey of Canada Bulletin, v. 461, p. 1–107. Dovgal, Yu.M., Gorodinsky, M.Ye., and Sterligova, M.Ye., 1975, The Aluchinskyi ultrabasite com- Kuzmichev, A.B., 2009, Where does the South Anyui suture go in the New Siberian Islands and plex, in Magmatism of Northeast Asia: Magadan, Russia, Knizhnoe Izdatel’stvo, v. 2, p. 59–70 Laptev Sea?: Implications for the Amerasia Basin origin: Tectonophysics, v. 463, p. 86–108, doi: [in Russian]. 10.1016 /j .tecto .2008 .09 .017 . Franke, D., Reichert, C., Damm, V., and Piepjohn, K., 2008, The South Anyui suture, northeast Arctic Kylander-Clark, A.R.C., Hacker, B.R., and Cottle, J.M., 2013, Laser-ablation split-stream ICP petro- Russia, revealed by offshore seismic data: Norwegian Journal of Geology, v. 88, p. 189–200. chronology: Chemical Geology, v. 345, p. 99–112, doi:10 .1016 /j .chemgeo .2013 .02 .019 . Frost, B.R., Avchenko, O.V., Chamberlain, K.R., and Frost, C.D., 1998, Evidence for extensive Lane, L.S., 1997, Canada Basin, Arctic Ocean: Evidence against a rotational origin: Tectonics, v. 16, Proterozoic remobilization of the Aldan shield and implications for Proterozoic plate tectonic no. 3, p. 363–387, doi:10 .1029 /97TC00432 . reconstructions of Siberia and Laurentia: Precambrian Research, v. 89, p. 1–23, doi:10.1016 Lawver, L.A., Grantz, A., and Gahagan, L.M., 2002, Plate kinematic evolution of the present Arctic /S0301-9268 (97)00074 -0 . region since the Ordovician, in Miller, E.L., Grantz, A., and Klemperer, S.L., eds., Tectonic Evo- Fujita, K., 1978, Pre-Cenozoic tectonic evolution of northeast Siberia: The Journal of Geology, v. 86, lution of the Bering Shelf–Chukchi Sea–Arctic Margin and Adjacent Landmasses: Geological p. 159–172, doi:10 .1086 /649672 . Society of America Special Paper 360, p. 333–358. Ganelin, A.V., 2011, Geochemistry and geodynamic significance of the dike series of the Aluchin Layer, P.W., Newberry, R., Fujita, K., Parfenov, L.M., Trunilina, V.A., and Bakharev, A.G., 2001, Tec- ophiolite complex, Verkhoyansk Chukotka fold zone, northeast Russia: Geochemistry Inter tonic setting of the plutonic belts of Yakutia, northeast Russia, based on 40Ar/39Ar and trace national, v. 49, p. 654–675, doi:10 .1134 /S0016702911070044 . element geochemistry: Geology, v. 29, p. 167–170, doi:10.1130 /0091 -7613(2001)029 <0167: Ganelin, A.V., and Silantyev, S.A., 2008, Composition and geodynamic conditions of formation of TSOTPB>2.0 .CO;2 . the intrusive rocks of the Gromadnen–Vurguveem peridotite–gabbro massif, western Chu- Ledneva, G.V., Pease, L.P., and Sokolov, S.D., 2011, Permo-Triassic hypabyssal mafic intrusions kotka: Petrology, v. 16, p. 565–583, doi:10 .1134 /S0869591108060039 . and associated tholeiitic basalts of the Kolyuchinskaya Bay, Chukotka (NE Russia): Links to Ganelin, A.V., Sokolov, S.D., Layer, P., and Simonov, V.A., 2013, New isotopic age data on ophiolite the Siberian LIP: Journal of Asian Earth Sciences, v. 40, p. 737–745, doi:10.1016 /j .jseaes .2010 complexes of western Chukotka (northeast Russia): Doklady Earth Sciences, v. 451, p. 679– .11.007 . 683, doi:10 .1134 /S1028334X13070027 . Li, Y., Barnes, M.A., Barnes, C.G., and Frost, C.D., 2007, Grenville-age A-type and related magma- Gasser, D., and Andresen, A., 2013, Caledonian terrane amalgamation of Svalbard: Detrital zircon tism in southern Laurentia, Texas and New Mexico, U.S.A.: Lithos, v. 97, p. 58–87, doi:10.1016 provenance of Mesoproterozoic to Carboniferous strata from Oscar II Land, western Spits- /j.lithos .2006 .12 .010 . bergen: Geological Magazine, v. 150, no. 06, p. 1103–1126, doi:10 .1017 /S0016756813000174 . Lineva, M.D., Malyshev, N.A., and Nikishin, A.M., 2015, The structure and seismostratigraphy of Gee, D.G., and Pease, V., 2004, The Neoproterozoic Timanide orogen of eastern Baltica: An intro- the sedimentary basins of the East Siberian Sea: Moscow University Geology Bulletin, v. 70, duction, in Gee, D.G., and Pease, V., eds., The Neoproterozoic Timanide Orogen of Eastern p. 1–17, doi:10 .3103 /S0145875215010032 . Baltica: Geological Society of London Memoir 30, p. 1–3. Lorenz, H., Mannik, P., Gee, D., and Proskurnin, V., 2008, Geology of the Severnaya Zemlya Archi- Gelman, M.L., 1970, Chukotka fold area, in Drabkin I.E, ed., Geology of USSR, Volume XXX, North- pelago and the North Kara terrane in the Russian High Arctic: International Journal of Earth East USSR. Geological Description. Book 2: Moscow, Nedra, p. 126–141 [in Russian]. Sciences, v. 97, no. 3, p. 519–547, doi:10 .1007 /s00531 -007 -0182 -2 . Gladkochub, D., Pisarevsky, S., Donskaya, T., Natapov, L., Mazukabzov, A., Stanevich, A., and Lorenz, H., Gee, D.G., Korago, E., Kovaleva, G., McClelland, W.C., Gilotti, J.A., and Frei, D., 2013, Sklyarov, E., 2006, The Siberian craton and its evolution in terms of the Rodinia hypothesis: Detrital zircon geochronology of Palaeozoic Novaya Zemlya—A key to understanding the Episodes, v. 29, no. 3, p. 169–174. basement of the Barents Shelf: Terra Nova, v. 25, no. 6, p. 496–503, doi:10 .1111 /ter.12064.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1562 by guest on 28 September 2021 Research Paper
Lychagin, P.P., Byalobzheskii, S.G., Kolyasnikov, Yu.A., and Likman, V.B., 1991, Magmatic history of Parfenov, L.M., 1997, Geological structure and geological history of Yakutia, in Parfenov, L.M., and the South Anyui fold zone, in Byalobzhessky, S.G., ed., Geology of the Continent–Ocean Tran- Spektor, V.B., eds., Geological Monuments of the Sakha Republic (Yakutia): Novosibirsk, Rus- sition Zone in Northeast Asia (Review of Results of the Most Important Studies of 1985–1990s): sia, Nauka, p. 60–77. Magadan, Russia, p. 140–157 [in Russian]. Parfenov, L.M., Natapov, L.M., Sokolov, S.D., and Tsukanov, N.V., 1993, Terrane analysis and ac- Lychagin, P.P., Kolyasnikov, Yu.A., Korago, E.A., and Likman, V.B., 1992, Petrology of Uyamkanda cretion in northeast Asia: The Island Arc, v. 2, p. 35–54, doi:10 .1111 /j.1440 -1738 .1993 .tb00073 .x. Layered Mafic-Ultramafic Massif (South-Anyui Fold Zone): Magadan, Russia, NEISRI FEB RAS, Patton, W.W., Jr., and Csejtey, B., Jr., 1980, Geologic Map of St. Lawrence Island, Alaska: U.S. Geo- 51 p. logical Survey Miscellaneous Investigations Map I-1203, scale 1:250,000. Ludwig, K.R., 2003, Isoplot/Ex 3.00: A Geochronological Toolkit for Microsoft Excel: Berkeley Geo- Patton, W.W., Jr., and Tailleur, I.L., 1977, Evidence in the Bering Strait region for differential move- chronology Center Special Publication 4, 70 p. ment between North America and Eurasia: Geological Society of America Bulletin, v. 88, Ludwig, K.R., 2005, Squid Version 1.13b: A User’s Manual: Berkeley Geochronology Center Special p. 1298–1304, doi:10 .1130 /0016 -7606 (1977)88 <1298: EITBSR>2 .0 .CO;2 . Publication 1, 70 p. Pearce, J.A., Harris, B.W., and Tindle, A.G., 1984, Trace element discrimination diagrams for the Miller, E.L., and Verzhbitsky, V.E., 2009, Structural studies near Pevek, Russia: Implications for for- tectonic interpretation of granitic rocks: Journal of Petrology, v. 25, p. 956–983, doi:10 .1093 mation of the East Siberian Shelf and Makarov Basin of the Arctic Ocean, in Stone, D.B., Fujita, /petrology/25 .4 .956 . K., Layer, P.W., Miller, E.L., Prokopiev, A.V., and Toro, J., eds., Geology, Geophysics and Tec- Pózer Bue, E., and Andresen, A., 2013, Constraining depositional models in the Barents Sea region tonics of Northeastern Russia: A Tribute to Leonid Parfenov: Copernicus Publications, Stephan using detrital zircon U-Pb data from Mesozoic sediments in Svalbard, in Spencer, A.M., Embry, Mueller Special Publication 4, p. 223–241. A.F., Gautier, D.L., Stoupakova, A.V., and Sørensen, K., eds., Arctic Petroleum Geology: Geo- Miller, E.L., Toro, J., Gehrels, G., Amato, J.M., Prokopiev, A., Tuchkova, M.I., Akinin, V.V., Dumitru, logical Society of London Special Publication 386, p. 261–279, doi:10.1144 /SP386 .14 . T.A., Moore, T.E., and Cecile, M.P., 2006, New insights into Arctic paleogeography and tectonics Prokopiev, A.V., Toro, J., Miller, E.L., and Gehrels, G.E., 2008, The paleo–Lena River—200 m.y. of from U-Pb detrital zircon geochronology: Tectonics, v. 25, doi:10 .1029 /2005TC001830 . transcontinental zircon transport in Siberia: Geology, v. 36, p. 699–702, doi:10.1130 /G24924A .1 . Miller, E.L., Soloviev, A., Kuzmichev, A., Gehrels, G., Toro, J., and Tuchkova, M., 2008, Jurassic and Radzivill, A.Ya., 1964, New data on geology of south-eastern part of South-Anyui range, in Mate- Cretaceous foreland basin deposits of the Russian Arctic: Separated by birth of the Makarov rials on Geology and Ore Deposits of North-Eastern USSR: Magadan, NE Geol Department, Basin?: Norwegian Journal of Geology, v. 88, p. 201–226. p. 57–62 [in Russian]. Miller, E.L., Katkov, S.M., Strickland, A., Toro, J., Akinin, V.V., and Dumitru, T.A., 2009, Geochro- Radziwill, A.Ya., and Radziwill, V.Ya., 1975, Late Jurassic magmatic associations of the South nology and thermochronology of Cretaceous plutons and metamorphic country rocks, Anyui Depression, magmatism of northeastern Asia: Knizhnoe Izdatel’stvo, Magadan, v. 2, Anyui-Chukotka fold belt, north east Arctic Russia, in Stone, D.B., Fujita, K., Layer, P.W., Miller, p. 71–80. E.L., Prokopiev, A.V., and Toro, J., eds., Geology, Geophysics and Tectonics of Northeastern Rainbird, R.H., Heaman, L.M., and Young, G., 1992, Sampling Laurentia; detrital zircon geochronol- Russia: A Tribute to Leonid Parfenov: Copernicus Publications, Stephan Mueller Special Pub- ogy offers evidence for an extensive Neoproterozoic river system originating from the Gren- lication 4, p. 157–175. ville orogen: Geology, v. 20, p. 351–354, doi:10 .1130 /0091 -7613 (1992)020 <0351: SLDZGO>2 .3 Moll-Stalcup, E.J., Krogh, T.E., Kamo, S., Lane, L., Cecile, M.P., and Gorodinsky, M.E., 1995, Geo- .CO;2. chemistry and U-Pb geochronology of arc-related magmatic rocks, northeastern Russia: Geo- Rosen, O.M., Condie, K.C., Natapov, L.M., and Nozhkin, A.D., 1994, Archean and Early Proterozoic logical Society of America Abstracts with Programs, v. 27, no. 5, p. 65. evolution of the Siberian craton: A preliminary assessment: Developments in Precambrian Moore, T.E., Wallace, W.K., Bird, K.J., Karl, S.M., Mull, C.G., and Dillon, J.T., 1994, Geology of north- Geology, v. 11, p. 411–459, doi:10 .1016 /S0166 -2635 (08)70228 -7 . ern Alaska, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Boulder, Colorado, Safonova, I., Maruyama, S., Hirata, T., Kon, Y., and Rino, S., 2010, LA ICP MS U-Pb ages of detrital Geological Society of America, The Geology of North America, v. G-1, p. 49–140. zircons from Russia’s largest rivers: Implications for major granitoid events in Eurasia and Moore, T.E., O’Sullivan, P.B., Potter, C.J., and Donelick, R.A., 2015, Provenance and detrital zircon global episodes of supercontinent formation: Journal of Geodynamics, v. 50, no. 3, p. 134–153, evolution of early Brookian foreland basin deposits of the western Brooks Range, Alaska, and doi:10 .1016 /j .jog .2010 .02 .008 . implications for early Brookian tectonism: Geosphere, v. 11, p. 93–122, doi:10 .1130 /GES01043 .1 . Seslavinsky, K.B., 1970, Formation and development of South-Anyui suture depression (western Mosher, S., 1998, Tectonic evolution of the southern Laurentian Grenville orogenic belt: Geologi Chukotka): Geotectonics, v. 5, p. 56–68. cal Society of America Bulletin, v. 110, p. 1357–1375, doi:10.1130 /0016 -7606(1998)110 <1357: Seslavinsky, K.B., 1979, South-Anyui suture (western Chukotka): Transactions (Doklady) of the Rus- TEOTSL>2.3 .CO;2 . sian Academy of Sciences, v. 249, p. 1181–1185. Natal’in, B.A., 1984, Early Mesozoic Folded Belts in the North Part of the Pacific Rim: Moscow, Seton, M., Müller, R.D., Zahirovic, S., Gaina, C., Torsvik, T.H., Shephard, G., Talsma, A., Gurnis, M., Nauka, 125 p. Turner, M., Maus, S., and Chandler, M., 2012, Global continental and ocean basin reconstruc- Natal’in, B.A., Amato, J.M., and Toro, J., 1999, Paleozoic rocks of northern Chukotka Peninsula: tions since 200 Ma: Earth-Science Reviews, v. 113, p. 212–270, doi:10 .1016 /j .earscirev .2012.03 Implications for the tectonics of the Arctic region: Tectonics, v. 18, p. 977–1003, doi:10.1029 .002. /1999TC900044. Shekhovtsov, V.A., 1991, A Report on the Geological Mapping and General Exploration, Quad- Nokleberg, W.J., Parfenov, L.M., Monger, J.W.H., Baranov, B.V., Byalobzhesky, S.G., Bundtzen, T.K., rangle Q-58, Gremuchaya-Ainakhkurgen Rivers, between 1986–1991: Bilibino, Russia, Feeney, N.D., Fujita, K., Gordey, S.P., Grantz, A., Khanchuk, A.I., Natalin, B.A., Natapov, L.M., Anuyuiskoe Gosudarstvennoe Gorno-Geologicheskoe Predprivatie Press, scale 1:50,000, 312 p. Norton, I.O., Patton, W.W., Plafker, G., Scholl, D.W., Sokolov, S.D., Sosunov, G.M., Stone, D.B., [in Russian]. Tabor, R.W., Tzukanov, N.V., Vallier, T.L., and Wakita, K., 1994, Circum–North Pacific Tectono Shekhovtsov, V.A., and Glotov, S.P., 2001, State Geological Map of the Russian Federation, Oloy stratigraphic Terrane Map: U.S. Geological Survey Open-File Report 94-714, scale 1:5,000,000, Series, Quadrangle Q-58-XI, XII, Explanatory Note (edited by S.D. Sokolov): Moscow, Anyuiskoe 1 sheet. Gosudarstvennoe Gorno-Geologicheskoe Predpriyatie, Ministerstvo Prirodnykh Resursov, scale Nokleberg, W.J., Parfenov, L.M., Monger, J.W.H., Norton, I.O., Khanchuk, A.I., Stone, D.B., Scotese, 1:200,000 [in Russian]. C.R., Scholl, D.W., and Fujita, K., 2000, Phanerozoic Tectonic Evolution of the Circum–North Shephard, G.E., Müller, R.D., and Seton, M., 2013, The tectonic evolution of the Arctic since Pangea Pacific: U.S. Geological Survey Professional Paper 1626, 122 p. breakup: Integrating constraints from surface geology and geophysics with mantle structure: Omma, J.E., Pease, V., and Scott, R.A., 2011, U-Pb SIMS zircon geochronology of Triassic and Juras- Earth-Science Reviews, v. 124, p. 148–183, doi:10 .1016 /j .earscirev .2013 .05 .012 . sic sandstones on northwestern Axel Heiberg Island, northern Sverdrup Basin, Arctic Canada, Silberling, N.L., Jones, D.L., Monger, J.W.H., Coney, P.J., Berg, H.C., and Plafker, G., 1994, Lithotec- in Spencer, A.M., Embry, A.F., Gautier, D.L., Stoupakova, A.V., and Sorensen, K., eds., Arctic tonic terrane map of Alaska and adjacent parts of Canada, in Plafker, G., and Berg, H.C., eds., Petroleum Geology: Geological Society of London Memoir 35, p. 559–566, doi:10 .1144 /M35 .37 . The Geology of Alaska: Boulder, Colorado, Geological Society of America, The Geology of Parfenov, L.M., 1984, Continental Margins and Island Arcs in the Mesozoides of Northeastern Asia: North America, v. G-1, scale 1:2,500,000. Novosibirsk, Russia, Nauka, 192 p. [in Russian]. Sokolov, S.D., and Bondarenko, G.Ye., Morozov, O.L., Shekhovtsov, V.A., Glotov, S.P., Ganelin, A.V., Parfenov, L.M., 1991, Tectonics of the Verkhoyansk-Kolyma Mesozoids in the context of plate tec- and Kravchenko-Berezhnoy, I.R., 2002, The South Anyui suture, NE Arctic Russia: Facts and tonics: Tectonophysics, v. 199, p. 319–342, doi:10 .1016 /0040 -1951 (91)90177 -T . problems to solve, in Miller, E.L., Grantz, A., and Klemperer, S.L., eds., Tectonic Evolution of
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1563 by guest on 28 September 2021 Research Paper
the Bering Shelf–Chukchi Sea-Arctic Margin and Adjacent Landmasses: Geological Society of McLelland, J., and Bartholomew, M.J., eds., Proterozoic Tectonic Evolution of the Grenville America Special Paper 360, p. 209–224. Orogen in North America: Geological Society of America Memoir 197, p. 1–18. Sokolov, S.D., Bondarenko, G.Y., Layer, P.W., and Kravchenko-Berezhnoy, I.R., 2009, South Anyui Toro, J., Toro, F.C., Bird, K.J., and Harrison, C., 2004, The Arctic Alaska–Canada connection revis- suture: Tectono-stratigraphy, deformations, and principal tectonic events, in Stone, D.B., ited: Geological Society of America Abstracts with Programs, v. 36, no. 5, p. 22. Fujita, K., Layer, P.W., Miller, E.L., Prokopiev, A.V., and Toro, J., eds., Geology, Geophysics Tuchkova, M.I., Sokolov, S., and Kravchenko-Berezhnoy, I.R., 2009, Provenance analysis and tec- and Tectonics of Northeastern Russia: A Tribute to Leonid Parfenov: Copernicus Publications, tonic setting of the Triassic clastic deposits in western Chukotka, northeast Russia, in Stone, Stephan Mueller Special Publication 4, p. 201–221. D.B., Fujita, K., Layer, P.W., Miller, E.L., Prokopiev, A.V., and Toro, J., eds., Geology, Geophysics Sokolov, S.D., Tuchkova, M.I., Ganelin, A.V., Bondarenko, G.E., and Layer, P., 2015, Tectonics and Tectonics of Northeastern Russia: A Tribute to Leonid Parfenov: Copernicus Publications, of the South Anyui suture, northeastern Asia: Geotectonics, v. 49, p. 3–26, doi:10 .1134 Stephan Mueller Special Publication 4, p. 177–200. /S0016852115010057. Tynankergav, G.A., and Bychkov, J.M., 1987, Upper Triassic chert-volcanic-terrigenous assem- Stacey, J.S., and Kramers, J.D., 1975, Approximation of terrestrial lead isotope evolution by a two- blages of western Chukotka: Transactions (Doklady) of the Russian Academy of Sciences/Earth stage model: Earth and Planetary Science Letters, v. 26, p. 207–221, doi:10.1016 /0012 -821X Science Section, v. 296, p. 698–700 [in Russian]. (75)90088-6 . Voice, P.J., Kowalewski, M., and Eriksson, K.A., 2011, Quantifying the timing and rate of crustal Strickland, A., Miller, E.L., Wooden, J.L., Kozdon, R., and Valley, J.W., 2011, Syn-extensional plu- evolution: Global compilation of radiometrically dated detrital zircon grains: The Journal of tonism and peak metamorphism in the Albion–Raft River–Grouse Creek metamorphic core Geology, v. 119, p. 109–126, doi:10.1086 /658295 . complex: American Journal of Science, v. 311, p. 261–314, doi:10.2475 /04 .2011 .01. Wang, P., Li, Q., and Li, C.F., 2014, Geology of the China Seas, in Stein, R., ed., Developments in Surkov, V.S., Salnikov, A.S., Kuznetsov, V.L., Lipilin, A.V., Seleznev, V.S., Emanov, A.F., and Solov’ev, Marine Geology, Volume 6: Oxford, U.K., Elsevier, 702 p. V.M., 2007, Structure of the Earth’s crust in the Magadan sector of north-eastern Russia on Williams, I.S., 1998, U-Pb by ion microprobe, in McKibben, M.A., Shanks, W.C., and Ridley, W.I., deep seismic sounding data, in Structure and Compositions of Earth’s Crust in Magadan Sec- eds., Applications of Microanalytical Techniques to Understanding Mineralizing Processes: tor of Russia from Geological-Geophysical Data: Novosibirsk, Nauka, p. 13–21 [in Russian]. Littleton, Colorado, Society of Economic Geologists, Reviews in Economic Geology, p. 1–35. Tibilov, I.V., Begunov, S.F., Larionov, Ya.C., and Piankov, A.Ya., 1982, On the stratigraphy of the Tri- Williams, S., Müller, R.D., Landgrebe, T.C.W., and Whittaker, J.M., 2012, An open-source software assic of the Chukchi structural-facies region: Materialy po Geologiya i Poleznym Iskopaemym environment for visualizing and refining plate tectonic reconstructions using high resolution Severo-Vostoka SSSR, v. 26, p. 15–22 [in Russian]. geological and geophysical data sets: GSA Today, v. 22, no. 4–5, doi:10.1130 /GSATG139A .1 . Till, A.B., and Dumoulin, J.A., 1994, Geology of Seward Peninsula and Saint Lawrence Island, in Yegorov, D.F., 1962, Report on Geological Mapping and General Exploration, Quadrangle Q-58- Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Boulder, Colorado, Geological Society V-VI, between the Anyui and Chaun Rivers: Leningrad, Ministerstvo Geologii SSSR, Anyuiskoe of America, The Geology of North America, v. G-1, p. 141–152. Gosudarstvennoe Gorno-Geologicheskoe Predpriyatie, VSEGEI, scale 1:200,000 [in Russian]. Ti’lman, S.M., and Bogdanov, N.A., 1992, Tectonic Map of Northeast Asia (edited by Yu.M. Push- Zhang, X., Pease, V., Skogseid, J., and Wohlgemuth-Ueberwasser, C., 2015, Reconstruction of tec- charovsky): Moscow, Institute of the Lithosphere, scale 1:500,000 [in Russian]. tonic events on the northern Eurasia margin of the Arctic, from U-Pb detrital zircon provenance Ti’lman, S.M., Afizky, A.I., and Chekhov, A.D., 1977, Comparative tectonics of the Alazeya and Oloy investigations of late Paleozoic to Mesozoic sandstones in southern Taimyr Peninsula: Geologi zones (north-east of the USSR) and the Kolyma massif problem: Geotektonika, v. 4, p. 6–17 cal Society of America Bulletin, doi:10 .1130 /B31241 .1. [in Russian]. Zonenshain, L.P., Kuzmin, M.I., and Natapov, L.M., and Page, B.M., eds., 1990, Geology of the Tollo, R.P., Corriveau, L., McLelland, J., and Bartholomew, M.J., 2004, Proterozoic tectonic evolu- USSR: A Plate-Tectonic Synthesis: American Geophysical Union Geodynamics Monograph tion of the Grenville orogen in North America: An introduction, in Tollo, R.P., Corriveau, L., 21, 242 p.
GEOSPHERE | Volume 11 | Number 5 Amato et al. | Tectonic evolution of the Mesozoic South Anyui suture zone, eastern Russia Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/11/5/1530/3336239/1530.pdf 1564 by guest on 28 September 2021