Research Article the Carboniferous Arc of the North Pamir

GeoScienceWorld Lithosphere Volume 2021, Article ID 6697858, 26 pages https://doi.org/10.2113/2021/6697858

Research Article The Carboniferous Arc of the North Pamir

1 1 2 3 4 Johannes Rembe , Edward R. Sobel , Jonas Kley , Renjie Zhou , Rasmus Thiede , 5 and Jie Chen 1Institute of Geosciences, University of Potsdam, 14476 Golm Potsdam, Germany 2Department of Structural Geology and Geodynamics, Georg-August-Universität Göttingen, 37077 Göttingen, Germany 3School of Earth and Environmental Sciences, The University of Queensland, St. Lucia QLD 4072, Australia 4Institute for Geosciences, Christian-Albrechts-Universität Kiel, 24118 Kiel, Germany 5State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, X9GJ+RV Chaoyang, Beijing, China

Correspondence should be addressed to Johannes Rembe; [email protected]

Received 28 October 2020; Accepted 7 January 2021; Published 8 February 2021

Academic Editor: Pierre Valla

In this study, we investigate the age and geochemical variability of volcanic arc rocks found in the Chinese, Kyrgyz, and Tajik North Pamir in Central Asia. New geochemical and geochronological data together with compiled data from the literature give a holistic view of an early to mid-Carboniferous intraoceanic arc preserved in the northeastern Pamir. This North Pamir volcanic arc complex involves continental slivers in its western reaches and transforms into a Cordilleran-style collision zone with arc- magmatic rocks. These are hosted in part by Devonian to Carboniferous oceanic crust and the metamorphic Kurguvad basement block of Ediacaran age (maximum deposition age) in Tajikistan. We discuss whether a sliver of Carboniferous subduction-related basalts and intruded tonalites close to the Chinese town of Mazar was part of the same arc. LA-ICP-MS U- Pb dating of zircons, together with whole rock geochemistry derived from tonalitic to granodioritic intrusions, reveals a major Visean to Bashkirian intrusive phase between 340 and 320 Ma ago. This clearly postdates Paleozoic arc-magmatic activity in the West Kunlun by ~100 Ma. This observation, along with geochemical evidence for a more pronounced mantle component in the Carboniferous arc-magmatic rocks of the North Pamir, disagrees with the common model of a continuous Kunlun belt from the West Kunlun into the North Pamir. Moreover, Paleozoic oceanic units younger than and west of the Tarim cratonic crust challenge the idea of a continuous cratonic Tarim-Tajik continent beneath the Pamir.

1. Introduction late phase of the India-Asia collision, pushing the Pamir several hundred kilometers toward the north with respect A common model for plate tectonic reconstructions of to Tibet (e.g., Burtman and Molnar [1] and Schwab et al. northern Tibet and the Pamir has been the assumption of a [3]). The Pamir and Tibet formed during the Phanerozoic continuous magmatic belt extending from the West Kunlun as a result of successive accretions of Gondwana-derived into the northern Pamir [1, 2]. However, comparisons crustal blocks. Today, the Pamir and Tibet are part of the between the Paleozoic-early Mesozoic evolution of the poorly India-Asia collision zone—the largest active continental studied North Pamir and the adjacent, well-documented collision. At the longitude of the Pamir, the highest modern West Kunlun belt in northern Tibet reveal significant differ- strain rates are found far to the north, along the Main Pamir ences; these likely explain the different Cenozoic deformation Thrust (MPT) [4, 5]. In contrast, to the east, N-S shortening styles of the adjacent regions. The Pamir orogen is the west- rates within northern Tibet are much smaller [6, 7]; the bulk ward extension of the Tibetan Plateau. A common hypothe- of the convergence is accommodated, along the southern sis is that the Pamir indented into the Tajik-Tarim basin in a margin of Tibet, within the Himalaya. To understand the

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Cenozoic MPT and hence the difference between Pamir and into the northern reaches of the Hindu Kush/Badakhshan Tibetan deformation styles, it is crucial to understand the region in Afghanistan [32–35]. Oceanic rocks were assigned pre-Cenozoic geologic evolution. to the Kalai Khumb-Oytag basin (KOB), a marginal basin The Pamir has traditionally been subdivided into the of the Paleo-Asian ocean [36]; this has also been named the North, Central, and South Pamir terranes (Figure 1(a)). Kunlun arc [3] or the Pamir arc [33, 37]. Leucocratic granit- The North Pamir terrane was subdivided into the North oids, including tonalites and trondhjemites, are found as Pamir Kunlun, which includes middle Paleozoic basalt, gab- large intrusions within mafic volcanic rocks and are dated bro, and felsic plutons, and the North Pamir Karakul-Mazar as Visean to Bashkirian (338–314 Ma [28–31]). These units terrane, which represents a late Paleozoic-early Mesozoic are inferred to represent the remnants of an intraoceanic arc accretionary wedge intruded by felsic plutons [3, 8]. Despite that marks a phase of intraoceanic subduction and the initial strong deformation and fault dissection, the Chinese Gez closure of an ocean basin [29]. Granitoids in NW Afghanistan valley is today the best-studied locality in the North Pamir. also intrude lower Carboniferous marine strata and yield K- The Karakul-Mazar terrane was correlated with the Ar ages between 335 and 360 Ma ([38] cited in [32]).Whether Songpan-Ganzi-Hoh Xil complex of northern Tibet [9], the small occurrence of mafic volcaniclastic rocks and associ- while the North Pamir Kunlun was correlated with the South ated leucogranites of similar age, found in the Mazar tectonic Kunlun terrane of the West Kunlun in Tibet (e.g., [10, 11]). mélange zone [39] east of the town of Mazar (Figure 1(a), The West Kunlun is subdivided into the North and South “East Mazar”), is part of the KOB must be discussed; this Kunlun terranes, divided by the early Paleozoic Kudi suture. would increase the eastward extension of the basin. The North Kunlun corresponds to the margin of the Protero- In this paper, our new geochemical and geochronological zoic Tarim block [12, 13]. This was described from the Kudi data combined with our literature compilation demonstrates section, the best-studied section crossing the North and that the term North Pamir Kunlun is misleading. There is no South Kunlun south of the town of Kargilik [11, 14, 15]. evidence for a lateral continuation of the North Pamir Devo- However, there is little similarity between the North Pamir nian to Carboniferous arc-magmatic sequence into the South Kunlun and the South Kunlun terrane of the West Kunlun. Kunlun. Therefore, herein, we use the term North Pamir arc There is an ongoing debate about how and which units of as previously used by Bazhenov and Burtman [33], rather the Tibetan Plateau/West Kunlun are the along-strike equiva- than the North Pamir Kunlun. lent of units within the Pamir plateau. Two of those seemingly Rock units of the North Pamir arc experienced variable laterally contiguous structures—the Kudi-Oytag ophiolites degrees of greenschist to lower amphibolite facies metamor- and ophiolites along the Tanymas-Jinsha structure—were phic overprint; higher metamorphic units potentially associ- interpreted as the remnants of former suture zones related to ated with Pennsylvanian to Permian subduction processes the closure of the Proto- and Paleo-Tethys [1, 2, 3, 10, 11, might have been identified by Li et al. [40] in the Tajik 16]. Based on this interpreted lateral continuity, estimates of North Pamir arc (see Discussion). Moreover, a nonmeta- the amount of largely Cenozoic northward indentation of morphic sedimentary succession of upper Permian to the Pamir orogen, with respect to the Tibetan Plateau, were Eocene ages overlies Carboniferous rocks in the Chinese made (e.g., more than 300 km by Burtman and Molnar [1], Qimgan valley (Figure 2) and shows no sign of a major 300–400 km by Burtman [17]). Well-documented early Paleo- post-Carboniferous collisional event affecting the NE Pamir. zoic magmatism, of either syn- or postcollisional nature, is Therefore, the Permo-Triassic Qimgan basin [41] formed thought to be related to the closure of the Proto-Tethys along on a fragment of Carboniferous oceanic crust that is now the Kudi suture zone [18–20], which finally closed between situated in the External Pamir and was affected by thin- 440 Ma (monazite U-Pb age of biotite schist from the Saitula skinned deformation in Cenozoic time. group [13]) and 405 Ma (zircon U-Pb age of the A-type North Following the initial observation that the North Pamir Kudi Pluton [14]). This was followed by a Late Permian to arc of the NE Pamir has many similarities with units further Triassic intense magmatic phase related to the subduction west [42] and little in common with the West Kunlun to the of the Paleo-Tethys and the collision of the Central Pamir- east, the aim of this study is to better constrain the age and Qiangtang block with Asia [14, 19, 21–23], culminating in tectonic affinity of the Carboniferous arc-related rocks. the formation of the Tanymas-Jinsha suture zone (Figure 1) Within this contribution, we present new and compiled geo- between 243 Ma (zircon U-Pb age of anatectic Yuqikapa chemical and geochronological data from locations in the pluton [21]) and 190 Ma (metamorphic zircon U-Pb age Tajik, Kyrgyz, and Chinese North Pamir and document that population in amphibolite facies metasediments from they have a common temporal evolution. We compare this Karakul-Mazar accretionary complex [8]). A phase of volca- data with the well-known tectonothermal events recorded nic quiescence has been proposed between the Silurian and in the West Kunlun. Thereby, we can test existing models Triassic in the NE Pamir and the West Kunlun [19, 24]. of the northernmost suture zone in the Pamir and its relation In the North Pamir Kunlun, however, oceanic maficto to units in the West Kunlun to the east and the Hindu Kush/- intermediate volcanic rocks and marine cherts of Upper Badakhshan to the west. Devonian to Bashkirian age [2, 3, 25–27] can be found. This narrow, ca. 400 km long zone (Figure 1(a)) spans from the 2. Geology Chinese Gez and Oytag (also called Wuyitake or Aoyitake) valleys [28–31] along the strike of the frontal Pamir moun- 2.1. Overview. Within this study, we compare outcrops, liter- tain chain to the Tajik town of Kalai Khumb and continues ature data, and new field observations from the following

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71.00 75.00 77.00 79.00 Geology (Figures 1(b)-1(d)) Age Data Altyn Darya Karakul Taergelake Alai Granite External Tarim Igneous zircon U/Pb Kalai Khumb C MPT Pamir D PFT Triassic sedimentary rocks data, this study Shala Tala We Pamir frontal thrust i Main pamir thrust Tadjik m r s Nappe Oytag/Gez t Ku n lu n 00.93 Permian sedimentary rocks Kurgu- basin a Igneous zircon U/Pb Karakul- P vad Yuqikapa Carboniferous data, literature Tanymas suture North Pamir-Kunlum Mazar Bulunkou sedimentary units KYTS Detrital zircon U/Pb B Muztagh Carboniferous Central Pamir Major thrust data, this study Datong volcaniclastics and Kusilafu lava ﬂows KBB Major normal Calcite U/Pb Taer fault Pre-Carboniferous Rushan-pshart-zone Beileki data, this study Sutures ? Qiukesu Kurguvad gneiss Yirba Buya Hornblende Ar-Ar South Pamir Karakoram fault Karakax fault North Kudi Glacier data, literature Fayzabad Tiekelike fault

00.73 Major thrust Kudi suture Monazite U/Pb Fakhar Major strike-slip fault North data, literature South Kunlun Fault contact Jiajiwaxi Kunlun 0 50 100 km 200 Karakoram Arkaz Age Data in Ma East Mazar (a) Geochemistry

70.5 71.0 71.5 72.20 72.30 74.5 75.0 75.5 39.40 MPT 17NP439 17NP438 39.5 MPT 250.0±0.3 347.0±7.6 RT13.111 RT13-108 339.1±1.2 333.6±0.4 Taergelake valley Qimgan valley 16NP341 15NP247 RT13-109 337.4±0.4 17NP472 KL027 (5)

329.3±0.6 Altyn Darya MPT 15NP233-1 260.5±2.2 331.1±14.5 16NP342 39.0 15NP245 15NP233-2 340.0±0.5 2011T49 AD6b (2) 360.5±0.4 15NP234 Bostantielieke 10X01 (6) 354.7±2.2 39.30 15NP235 village Khingob/Obikhingou 322.8±1.6 RT13-115 15NP236 334.3±0.5 RT13-111 RT13-108 AD6c (2) Oytag village 39.0 RT13-109 329.0±5.0 01-09-13-01 Obikhingou valley 16NP341 17NP426 WYT-5 (3) 16NP342 Vanj 31-08-13-01 328.4±3.3 RT15-11 AD2e (2) Kalai Khumb GZ-1 (3) P09T32 576.2±1.3 357.1±2.5 RT13-115 RT13-146 38.5 338.0±2.1 D03-6 (4) P09T33 314.2±1.0 39.20 RT13-149 RT13-146 Gez 322.1±0.7 AD2a (2) 329.0±5.0 Panj RT13-148 4717A2 (1) 010203040 km 0 10203040 km 589.8±1.0 204.9±8.8 024 68 km

(b) (c) (d)

Figure 1: (a) Simpliﬁed map of the major tectonic units in the Pamir (after [22]) showing positions of outcrop areas in the Tajik (b), Kyrgyz (c), and Chinese (d) North Pamir. Outcrop areas of Carboniferous granitoids (bold label, purple polygon) and early Paleozoic (green polygon) and Triassic (red polygon) granitoids mapped from literature are labelled. Sampling points for whole rock geochemistry samples processed for this study are marked with green boxes. Boxes with age data contain original and literature data. LA-ICP-MS Zircon U-Pb data is according to Table 2, column 5 in Ma ± 1σ. Further literature according to italic numbers in brackets: (1) Schmidt et al. [52], (2) Schwab et al. [3], (3) Jiang et al. [29], (4) Ji et al. [28], (5) Zhang et al. [30], and (6) Kang et al. [31]. (b) Map of the Tajik North Pamir between Panj and Obikhingou river valleys after Lyoskind et al. [34], Vlasov et al. [49], Burmakin et al. [35], and Kafarsky and Pyjanov [51]. (c) Map of the Kyrgyz Alai Valley after Vlasov et al. [49]. (d) Map of the Chinese North Pamir between Gez and Taergelake river valleys by own mapping and Lu et al. [25], Wang and Peng [26], and HIGS [27]. Glacier polygons from GLIMS database [117]. PFT: Pamir Frontal Thrust; MPT: Main Pamir Thrust; KBB: Kurguvad basement block; KYTS: Kashgar-Yesheng Transfer System.

sites (maps in Figure 1(a) and profiles in Figure 2): (1) the unconformity are nonmetamorphic Visean limestones [32]. Badakhshan region in Afghanistan, (2) the Kalai Khumb These are separated by a second angular unconformity from and Obikhingou area in Tajikistan (Figure 1(b)), (3) the Kyr- upper Pennsylvanian to Permian units dominated by littoral gyz Altyn Darya valley (Figure 1(c)), (4) the Chinese NE to sublittoral clastics and regional marls and platform lime- Pamir (Taergelake valley to Oytag valley, Figure 1(d)), and stones (Figure 2 [32, 44]). The age of the dioritic intrusive (5) the East Mazar area. Our study area is focused on loca- rocks in the Badakhshan region is inferred from relative geo- tions (2)–(4). However, from excellent, detailed field descrip- logic relationship with disconformably overlying Permian tions, geological observations, and maps made during the last sedimentary rocks [47] and from K-Ar ages of 335–360 Ma century [32, 33, 43, 44], significant similarities between the from diorite and granodiorite found in the Surkhab river Carboniferous units exposed in Badakhshan and the Tajik valley ([38] cited in [32]). Diorites, granodiorites, and Pamir can be inferred. This was proposed and discussed by granites intruded the sequence in the Fakhar area in the previous studies [37, 44–46]. Khanabad river valley during the Mississippian [48].

2.2. Badakhshan. From northwestern Afghanistan, the 2.3. Kalai Khumb and Obikhingou. A Silurian to Permian Badakhshan and the southeastern Takhar regions, Lower succession was described along the Panj and Khingob/Obi- Mississippian calc-alkaline lavas, volcaniclastics [32, 43], khingou river valleys and tributaries located in the northwest and coral bearing limestones [44] are known (Figure 2). In Tajik Pamir (Figure 2 [49]). Silurian to Devonian sediments the Surkhab (aka Kunduz river) valley, Lower Mississippian are the oldest exposed low-grade metamorphic units in the units are composed of low-grade metamorphosed amygda- region [34, 35, 49]. A low-grade metamorphosed ophiolitic loid-basalts, andesites, and tuﬀs [33]. Above an angular sequence described as Carboniferous [50] is part of a nappe

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12 345 6 7

J T? T3 C2-P T C2-P P T1-2 P P2-T C2 C-P? C2 C2 P T C1? C2 C1 C1 C1 P C2 C2 D-C1? ~C D-C1? D-C1 C1 D3-C1 C? D-C1? D3

S-D D-C1?

C1 D-C1?

Marine sandstone, greywackes, Continental, Floodplain, green siltstones, shales sandstones and siltstones Acidic small intrusions Devonian/Silurian shallow Continental, alluvial red Ophiolite related marine sandstones and sandstones and siltstones coarse crystalline rock siltstones Continental, alluvial red (gabbro, dunite, peridotite) Marine conglomerates sandstones and Metavolcanics conglomerates

Plattform carbonates Acidic tuﬀaceous rocks Metaclastics

Clastic carbonates Tonalite, granodiorite Unconformity plagiogranite Angular unconformity Lacustrine, cherty Basic to intermediate volcanics, in brackets: locally carbonates pillow-lava and volcaniclastics rust Basic to intermediate tuﬀaceous rocks

Figure 2: Schematic stratigraphic columns of the Kalai Khumb-Oytag basin, from west to east: (1) synthesis of sections from Fakhar and Surkhab river valley after Wolfart and Wittekindt [32], (2) Kalai Khumb after Leven [53], (3) Kurguvad after Schwab et al. [3], (4) Altyn Darya after Schwab et al. [3] and Leven [55], (5) synthesis of sections in Qimgan/Akqi and Gez valleys, (6) synthesis of sections near Bostantielieke and Kawuke villages, and (6) East Mazar after Li et al. [39]. Thickness of stratigraphic units is not to scale. Abbreviations of geological periods: Ꞓ: Cambrian; O: Ordovician; S: Silurian; D: Devonian; D3: Upper Devonian; C: Carboniferous; C1: Mississippian; C2: Pennsylvanian; P: Permian; T: Triassic; T3: Upper Triassic; J—Jurassic.

sheet overlying the metamorphosed Kurguvad basement top of the volcanic sequence [53]. Our observations (below) block. The Kurguvad basement block was mapped as Prote- show that the section has been metamorphosed to greens- rozoic in age [51]. Peak metamorphic conditions of the Kur- chist or lower amphibolite facies. A granitic intrusion cover- guvad metamorphic suite were 540–650°C and 5.5–7.6 kbar; ing more than 50 km2 is also known from the Kurguvad concordant monazite 206Pb/238U and 208Pb/232Th ages basement block. are between 210 and 195 Ma [52]. All of the pre- Carboniferous units are covered by andesitic and basaltic 2.4. Altyn Darya. In the Altyn Darya valley of the Trans-Alai pillow lavas, volcaniclastics, and marly interbeds dated as range, basic to acidic volcanic rocks were described (Figure 2 upper Serpukhovian [53]. Gabbros and leucogranites [3]). 40Ar/39Ar hornblende dating of two andesite samples intruded this sequence. The Carboniferous gabbros and yielded ages of ~356 Ma; zircons from two rhyolite samples plagiogranites were grouped into the Obikhumbou complex yielded a Serpukhovian U-Pb ID-TIMS age of 329 Ma [3]. [54]. This lower succession was previously interpreted as an This volcanic section is overlain by an upper Pennsylvanian oceanic island arc [36]. Above an erosional unconformity, to Permian sedimentary sequence consisting of carbonates an amagmatic Bashkirian carbonate sequence covers the with intercalated tuﬀ and shales, as previously described

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from the Sauksai and Beleuli river sections. No unconformity rocks for petrology, geochemistry, and geochronology. The between the lower and upper Carboniferous is reported [55]. samples are from Carboniferous units in the Chinese and Our petrographic observations show that the section reached Tajik North Pamir as well as two Carboniferous volcanic greenschist facies metamorphic conditions. samples from the Kyrgyz Altyn Darya valley. One sample is from a large granodiorite intruded into the Tajik Kurguvad 2.5. Chinese NE Pamir: Taergelake, Qimgan/Akqi, Gez, and block. To constrain the paleogeographic affinity of this Oytag. Large volumes of Devonian to Mississippian volcani- poorly described basement block, two garnet bearing para- clastic rocks are mapped in the Chinese Taergelake, Qimga- gneiss samples were analyzed. Petrographic thin sections n/Akqi, Gez, and Oytag valleys (Figure 2 [27]). Large were made from all samples. Zircons were separated from 8 leucogranite intrusions are mapped in these locations. In granitoid samples, two paragneiss samples, and one aplitic Gez and Oytag, these provided ages between 338 and dike sample using a jaw crusher, disc grinder, water table, 314 Ma by zircon U-Pb dating [28–31] and are interpreted magnetic separation, and heavy liquids (SPT, DI). The as island arc derived [29]. The Qimgan/Akqi section exposes zircons were poured onto a glass plate and arranged in lines a rather complete, unmetamorphosed sequence. We found on double-sided sticky tape under a binocular microscope. upper Permian greenish-grey fine clastics and rare conglom- In-line mounting in epoxy helps for better single-grain rec- erates and cross-bedded sandstones disconformably overly- ognition. Mounted grains were polished to expose an internal ing the Carboniferous volcaniclastics (see Figure 2 and ages surface and imaged with cathodoluminescence (CL) using in Figure 1). The occurrence of mafic to intermediate volca- the electron microprobe facility at the University of Potsdam niclastic rocks and lava flows in the Permian succession (UP), Germany. decreases upsection. We interpret the lower, fine-grained Two carbonate samples, collected from the Chinese Qim- part of the sequence as floodplain deposits. Dark, silicified gan basin, were cleaned, cut, and polished. Both zircon and carbonates with monotonous ostracod fauna and remnants calcite were dated with U-Pb geochronology using a laser of charophytes are interpreted to represent a lacustrine envi- ablation inductively coupled plasma mass spectrometer ronment. Plant detritus is abundant in siltstones. They are (LA-ICP-MS) at the School of Earth and Environmental overlain by red, often cross-bedded coarse-grained clastic Sciences, the University of Queensland. rocks, interpreted as alluvial deposits of a terrestrial environ- A portion of the granitoid samples and all volcanic sam- ment. Apparently, parts of the Pennsylvanian and the lower ples from the Chinese and Kyrgyz Pamir were also processed Permian sequence are missing in this section or are extremely for whole-rock geochemistry (Table 2). They were cleaned, condensed compared to the Altyn Darya section. crushed, and milled in an agate mill to a particle size New field observations from the Bostantielieke valley, <62 μm. Melt tablets for X-ray fluorescence spectroscopy between Qimgan/Akqi and Gez, show that the Permian (XRF) analysis to measure major and trace elements were sequence there was overthrusted by a sedimentary sequence prepared at UP using fluxing agent FX-X65-2 (lithium tetra- containing thick greywackes, shales, phyllites, and prominent borate : lithium metaborate, 66 : 34). Samples for rare earth layer of dark marls, containing unidentified goniatites, cri- elements (REE) and yttrium and scandium measurements noid fragments, brachiopods, and mollusks. We interpret were sintered with sodium peroxide at 480°C and dissolved these deposits as fully marine sediments. They are in turn in hydrochloric acid. REE plus scandium and yttrium were overthrusted by greenschists, amphibolites, and marbles of then separated in ion exchange columns. Powder tablets were the Karakul-Mazar derived Shala Tala nappe [56, 57]. Folia- prepared from seven granite samples to determine the min- tion in the greenschist pervasively continues into the under- eral composition by X-ray powder diffraction (see Table 1). lying dark marls. Therefore, we interpret both nappes to have been emplaced in the same episode. Lineation and micro- 3.2. LA-ICP-MS Zircon U-Pb Geochronology. 262 zircon structures indicate nappe transport to the NNE to NW under grains from 8 granitoid samples were dated (Appendix 1(a) ductile conditions (Appendix 6). and Appendix 7). Additionally, we dated 109 zircons from two paragneiss samples RT15-11-and RT13-148 and 56 2.6. East Mazar. A tectonic horse, to the north east of the zircons from an aplitic dike (17NP439). Paragneiss sample town of Mazar, was described as a Mississippian maficto RT15-11 was mislabeled during processing as a granite; intermediate volcanic sequence (Figure 2 [39]). The section therefore, only 51 zircons were mounted. Zircon 91500, with comprises altered basaltic to andesitic lava flows, intermedi- a 206Pb/238U age of 1062:4±0:4Maand 206Pb/207Pb age ate to acidic tuffs, and volcanic breccias which were of 1065:4±0:3Ma [58] was used as a primary reference intruded by granitoids. The outcrop is crosscut by multiple material. Temora 2 zircons, with a 206Pb/238U age of faults. It is disconformably overlain by a thick Triassic 416:78 ± 0:33 Ma [59], was used as secondary reference conglomerate layer. material. Laser ablation was carried out with an ASI RESOlu- tion 193 nm ArF excimer laser system in the Radiogenic Iso- 3. Methodology tope Laboratory (RIF) at the University of Queensland. After air evacuation, He carrier gas was introduced into the laser 3.1. Fieldwork and Sample Preparation. Data from 27 rock chamber at a flow rate of 0.35 l/min. A flow of 0.005 l/min samples collected from the Tajik, Kyrgyz, and Chinese North N2 gas was also introduced into the laser chamber to enhance Pamir (Table 1) are presented in this study. We analyzed 12 the sensitivity of the measurements. The gas mixture was granitoid samples and 8 mafic and intermediate volcanic then transferred into the plasma torch of a Thermo iCAP

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Table 1: Location and characteristics of all samples used for this study.

Latitude Longitude Sample Location Rock Purpose Mineralogy in TS Mineralogy (N) (E) Chinese North Pamir P09T32 Gez Granitoid GC, TS qz-plg-ser-ep-chl 38.81628 75.45713 P09T33 Gez Granitoid GC, TS, XRD qz-plg-ser-ep-chl qz-ab-ep-chl 38.83728 75.47825 17NP426 Oytag Granite gneiss GC, TS qz-plg-ser-ep 38.94553 75.35925 17NP439 Qimgan Aplitic dike ZrU/Pb, TS gm-qz-chl 39.30928 74.86459 15NP233-1 Qimgan Basalt GC, TS plg-gm-chl-vesc 39.30451 74.86297 15NP233-2 Qimgan Basalt GC, TS plg-gm-chl-vesc 39.30451 74.86297 15NP235 Qimgan Basalt GC, TS plg-ol-chl-gm-amp 39.30113 74.85742 15NP234 Qimgan Basalt GC, TS plg-gm 39.30451 74.86297 2011T49 Qimgan Basalt GC, TS plg-gm-chl-ep 39.2881 74.8889 Carbonate 17NP438 Qimgan CalU/Pb, TS cal 39.30856 74.85677 pebble Lacustrine 17NP472 Qimgan CalU/Pb, TS cal 39.31515 74.87224 carbonate 15NP236 Qimgan Pillow basalt GC, TS plg-gm 39.30488 74.8583 15NP245 Taergelake Granitoid ZrU/Pb cf. 15NP247 39.31775 74.59724 15NP247 Taergelake Granitoid GC, TS, XRD qz-plg-ser-ep-chl qz-ab-chl-mc-ms 39.31775 74.59724 Kyrgyz North Pamir Altyn 01-09-13-01 Metabasalt GC, TS plg-gm-amp-chl 39.25958 72.25892 Darya Altyn 31-08-13-01 Metabasalt GC, TS plg-qz-amp-ep-chl-opk-gm 39.23586 72.255 Darya Tajik North Pamir ZrU/Pb, GC, TS, 16NP341 Obikhingou Granitoid qz-plg-bt-ser-ep-chl-amp qz-ab-chl-ms-cal 38.66072 70.90212 XRD ZrU/Pb, GC, TS, 16NP342 Obikhingou Cumulate chl-zo-qz-plg-opk chl-zo-czo-ab-qz-bt 38.65702 70.89395 XRD RT13-108 Khingob Granitoid ZrU/Pb, GC, TS qz-plg-stp-amp-ep-chl-ser 38.75177 71.23224 RT13-109 Khingob Granitoid ZrU/Pb, GC, TS qz-plg-bt-chl-ep 38.74758 71.23323 ZrU/Pb, GC, TS, RT13-111 Khingob Granitoid qz-ser-chl-plg-amp-ep qz-ms-chl-ab-act-ep 38.78572 71.21192 XRD Kalai RT13-115 Granitoid ZrU/Pb, GC, TS qz-plg-ser-chl-ep-stp 38.52496 70.81857 Khumb ZrU/Pb, GC, TS, RT13-146 Kurguvad Granitoid qz-bt-ms-plg-kfsp-ep qz-bt-ab-mc-ep 38.45605 71.11402 XRD RT13-148 Kurguvad Paragneiss ZrU/Pb, TS qz-bt-plg-grt-kfsp 38.3997 71.06168 RT13-149 Kurguvad Granitoid GC, TS, XRD qz-bt-ep-kfsp-plg-ms qz-bt-ep-ab-mc-chl 38.42699 71.04066 RT13-185 Kurguvad Paragneiss TS qz-bt-grt-chl 38.4074 71.05962 RT15-11 Khingob Paragneiss ZrU/Pb cf. RT13-148 and RT13-185 38.69131 71.38139 TS: thin section; GC: geochemistry; ZrU/Pb: zircon U-Pb age measurement; CalU/Pb: calcite U-Pb age measurement; XRD: X-ray diﬀraction; gm: groundmass. Mineral abbreviations according to IUGS [124].

RQ quadruple ICP-MS with 0.85 l/min Ar nebulizer gas. No for 206Pb/238U when measuring NIST612 glass using a line reaction gas was employed. The laser spot size was 30 μm scan of 3 μm/s, 10 Hz, 50 μm round laser pit, and 3 J/sm2. in diameter. Laser frequency was set to 10 Hz, with a mea- Laser spot locations on the sample zircons were carefully sured instrument laser ﬂuence of 2.9 J/cm2. For each ablation chosen using CL images. Fractures and zones with strongly spot, 3 s of blank was collected, followed by 20 s of ablation diﬀering Th/U values were avoided. and 5 s of wash out. Before starting data acquisition, the The following isotopes were counted (dwell time in ICP-MS signals were optimized by signal tuning. The zircons brackets): 88Sr (0.005 s), 91Zr (0.001 s), 200Hg (0.01 s), were measured during two analytical sessions, in October 204Pb (0.01 s), 206Pb (0.045 s), 207Pb (0.055 s), 208Pb 2018 and in October 2019. Typically, we achieved over (0.01 s), 232Th (0.01 s), and 238U (0.01 s). As a single cycle 300 cps for 238U counts, ~1 for 238U/232Th, and 0.22–0.25 takes 0.155 s, during a 20 s ablation, approximately 120

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Table 2: Age data of all samples used for this study.

Age1 of youngest coherent Age2 of youngest coherent Age1 of youngest group of concordant grains group of concordant grains Number Sample Outcrop area concordant single-grain (TuffZirc, Ludwig (2003)) (peakfit, Vermeesch [68]) of grains ½Ma ±1σ ½Ma ±2σ ½Ma ±1σ Granitoids ∗ 15NP245 Taergelake valley 334:7±1:95 361:80 + 1:90/−3:50 360:52 ± 0:35 38 ∗ RT13-109 Khingob valley 219:0±1:55 329:00 + 5:20/−2:80 329:34 ± 0:59 25 RT13-108 Khingob valley 318:0±3:3 328:80 + 4:30/−1:30 333:55 ± 0:44 33 RT13-111 Khingob valley 325:6±2:25 334:10 + 2:00/−2:50 339:11 ± 1:23 34 RT13-115 Panj valley 326:4±2:4 329:75 + 5:35/−0:55 334:29 ± 0:52 29 16NP342 Kalai Khumb 337:9±1:2 340:10 + 1:70/−1:70 339:96 ± 0:46 30 16NP341 Kalai Khumb 324:6±1:2 338:90 + 1:20/−1:10 337:43 ± 0:38 46 ∗ RT13-146 Kurguvad 297:2±2:7 326:95 + 5:05/−2:65 322:14 ± 0:66 25 KL027 (Z06) Oytag valley 323:6±9:7 — 331:07 ± 14:47 16 ∗ GZ-1 (J08) Gez valley 248:1±4:62 — 338:03 ± 2:09 13 WYT-5 (J08) Oytag valley 449:4±8:7 — 328:43 ± 3:26 16 10X01 (K15) Oytag valley 321:8±2:3 — 322:76 ± 1:57 19 ∗ D03-6 (J18) Oytag valley 293 ± 1:85 — 314:19 ± 1:04 20 2RZ (L06) East Mazar ——338:52 ± 8:31 13 AD2a (S04) Altyn Darya — 329 ± 5 ID-TIMS age 329 ± 5 ID-TIMS age AD6c (S04) Altyn Darya — 329 ± 5 ID-TIMS age 329 ± 5 ID-TIMS age Kurguvad paragneiss ∗ RT15-11 Khingob valley 200:8±1:8 — 576:19 ± 1:34 25 RT13-148 Panj valley 557:6±5:5 — 589:75 ± 1:01 82 Aplitic dike 17NP439 Qimgan 242:3±1:0 250:70 + 0:90/−2:30 250:04 ± 0:28 31 Carbonate 260:49 ± 2:20 34∗∗ 17NP472 Qimgan ½ Discordia lower intercept age Ma ±1s ∗∗ 17NP438 Qimgan 347:02 ± 7:56 56 Data compiled from (Z06) Zhang et al. [30], (J08) Jiang et al. [29], (K15) Kang et al. [31], (J18) Ji et al. [28], (L06) Li et al. [39], and (S04) Schwab et al. [3].1Discordance cut-off for igneous zircons −10 ≤ d½% ≤ 10 and for detrital −10 ≤ d½% ≤ 30; d =1− ð206/238Þ/ð207/206Þ. 2Discordance cut-off for igneous and detrital zircons −10 ≤ d½% ≤ 10;ifage < 1000 Ma, d=1− ð206/238Þ/ð207/235Þ;ifage > 1000d =1− ð206/238Þ/ð207/206Þ; ∗lead loss presumed; ∗∗calcite ablation spots. measurements are taken for each mass. Reduction of the raw section examination of the samples. In situ calcite U-Pb anal- data was done in the program Iolite v2.5, which runs within ysis was also performed using the RIF LA-ICP-MS system. the Igor Pro environment [60, 61] using the VizualAge [62] An ASI Resolution 193 nm excimer UV ArF laser ablation data reduction scheme. The primary standard zircon 91500 system equipped with a dual-volume Laurin Technic ablation was used to bracket each five unknown analyses to correct cell was employed with an on-sample fluence of ~3 J/cm2 and for machine drift. 91500 data were not corrected for common a spot size of 100 μm. All samples were measured using a lead. Temora 2 zircons were treated as unknowns. The age of Thermo iCAP RQ quadruple ICP MS. Analyses consisted the primary standard was reproduced as a 206Pb/238U age of of 250 pulses at a repetition rate of 10 Hz. Each analysis 1062:7±0:2Ma, and Temora 2 gave a 206Pb/238U age of consists of 20 s background acquisition followed by 30 s of 420:70 ± 0:21 Ma and 417:80 ± 0:69 Ma in the 2018 and sample ablation and 7 s washout. We used NIST 614 to cor- 2019 measurement sessions, respectively. All unknowns were rect for 207Pb/206Pb fractionation and for instrument drift filtered for concordance and strontium content. LA-ICP-MS in the 206Pb/238U ratio [64]. Data reduction and production U-Pb dating and data processing were similar to these of carbonate U-Pb isotopic ratios were undertaken with the described in Zhou et al. [63]. software Iolite v2.5 [60, 61]. An in-house carbonate reference material (AHX-1a) of known age (209:80 ± 0:48 Ma[65, 66]) 3.3. LA-ICP-MS Calcite U-Pb Geochronology. Two limestone is used for normalization of 206Pb/238U ratios. Corrected samples were chosen for calcite U-Pb age determination data were regressed on Tera-Wasserburg plots using IsoplotR (Appendix 7). Suitable ablation spots were identified by thin [67] software to calculate the lower intercept ages. Our

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protocol is similar to recent carbonate in situ U-Pb LA-MC- dikes [29]. Those dikes can be found in the Oytag plagiogra- ICP-MS dating reported elsewhere [68–70], with the excep- nites as well as in the granitic intrusion in the Taergelake tion of using a different calcite reference material for the valley. Our field data and U-Pb data from the Chinese 206Pb/238U mass-bias correction. Qimgan basin, northwest of Oytag, show that the basaltic to andesitic Carboniferous lava flows are overlain by an upper 3.4. XRF and ICP-AES Whole Rock Geochemistry. XRF anal- Permian to Triassic continental sequence (Figure 2 [41]). ysis (X-ray fluorescence spectroscopy) was done at the The lower part of the sequence is characterized by fine- GeoForschungsZentrum Potsdam (GFZ) on a PANalytical grained greenish clastics; subordinate cross-bedded, red AXIOS Advances XRF system. Calibrations were validated alluvial sandstones; and up to two-meter-thick lacustrine car- by analysis of international reference materials. “Monitor” bonate layers. The entire lower part of the Permo-Triassic samples and 130 certified reference materials were used for continental basin hosts a large number of mafic to intermedi- the correction procedures. The detection limit of the XRF ate lava flows. We have obtained a new maximum age system is generally 10 ppm. The rare earth elements plus constraint for the continental basin by dating upper Permian yttrium and scandium were measured by inductively coupled sedimentary carbonate and an aplitic dike in the lower part of plasma atomic emission spectroscopy (ICP-AES) at UP on the section. an Agilent ICP5100 machine following the procedure of [71]. Long-term precision for ICP-AES at UP is generally 4.1.1. Granitoids. Several large leucocratic granitoid bodies <5%. High field strength elements were measured at the are mapped along the length of the North Pamir arc GFZ using standard ICP-MS procedures [72, 73]. The detec- (Figure 1). They are all dominated by quartz and plagioclase; tion limit is generally ±5% [74]. Concentrations of H2O and some show minor amounts of K-feldspar. Twelve granitoid ff CO2 were determined from 20 mg of sample powder, samples from di erent intrusions in the North Pamir arc weighed in tin foil. A Euro EA 3000 Elemental Analyser at were analyzed in this study (thin section photographs in UP was used for analysis. Figure 3 and Appendix 3 and modal mineral content in Appendix 10). They are medium to coarse grained and of 3.5. XRD Mineral Phase Analysis from Powder Samples and light grey to pale green color (Figure 3). They are generally EDX Mineral Phase Analysis from Thin Sections. Mineral composed of 25–45 vol% of quartz and 35–55 vol% of plagio- analysis of 7 granitoid samples were obtained at UP using a clase. Sample 17NP426 from the Oytag plagiogranite with a PANalytical Empyrean powder X-ray diffractometer (XRD) gneissic fabric yields higher amounts of quartz (60 vol%), with a Bragg-Brentano geometry. The XRD is equipped with while the plagioclase cumulate sample 16NP342 (Appendix a PIXcel1D detector using Cu K_α radiation (λ =1:5419 Å) 3(g) and (h)) from an outcrop close to the Tajik town of Kalai operating at 40 kV and 40 mA. θ/θ scans were run in a 2θ Khumb shows almost no quartz. Sample RT13-146 of a range of 4–70° with step size of 0.0131° and a sample rotation granite gneiss, found in the Kurguvad block in Tajikistan, is time of 1 s. It was equipped with a programmable divergence composed of 50 vol% quartz and just 10 vol% plagioclase. and antiscatter slit and a large Ni-beta filter. The detector was Plagioclases show common polysynthetic twinning and saus- set to continuous mode with an active length of 3.0061°. The suritization up to complete replacement of the primary crys- total detection time was 21 min. tals (Figure 3(d)). In several samples, plagioclase starts to be Double-polished thin sections of garnet bearing para- replaced by epidote from its center (Figure 3(e)). Gez plagio- gneiss from the Kurguvad basement block were analyzed with granites have strongly zoned plagioclase (Figure 3(f)). Ortho- the scanning electron microscope (SEM: JEOL JSM-6510 clase is largely absent and was only found in larger amounts SEM) at UP. Samples were carbon coated prior to analysis. (≤10 vol%) in samples 15NP247, RT13-146, and RT13-149. The SEM is equipped with an Inca-Xact Energy Dispersive Tajik plagiogranites have a significant amount of primary X-ray detector (EDX) from Oxford Instruments. INCA anal- biotite. The biotite grains show green to brown colors under ysis software [75] was used to distinguish the element distri- plane light. Coarse, greenish grains are interpreted as mag- bution in the minerals. Analyses were performed with a matic biotite that is in part replaced by brown, metamorphic measurement time of 60 s using a tungsten cathode at 20 kV. biotite. In the Chinese samples, biotite and other mafic minerals are rare. Samples from the Tajik Pamir (RT13-108, 4. Results RT13-115) host euhedral, unoriented aggregates of metamorphic stilpnomelane (Appendix 3(f)). In three Tajik plagi- 4.1. New and Previous Findings from Field Geology and ogranite samples (RT13-108, RT13-115, and 16NP341), we Petrology. Field investigations show that the North Pamir found minor amounts (≤10 vol%) of altered amphiboles arc experienced three phases of volcanism and related igne- (Appendix 3(a) and (b)). Amphiboles have light brown pleo- ous intrusions. The first phase featured the emplacement of chroic colors and are often replaced by epidote. Samples basaltic to andesitic lava flows, containing pillow lavas, mafic RT13-146 and RT13-149 have a two-mica mineralogy with to intermediate tuff layers, and cherts [3, 28]. These volumi- brown biotite and light grey to colorless muscovite nous volcanic deposits can be found along the strike from (Figure 3(c)). All samples contain minor amounts of primary Oytag in China into North Afghanistan [33]. As previously and secondary opaque minerals. Sample RT13-109 contains described, the first period of volcanism was followed by the secondary calcite. Samples RT13-146 and 17NP426 plot in intrusion of voluminous plagiogranites [30]. In a third phase, the quartz-rich granitoid field of the Streckeisen diagram the plagiogranites were crosscut by mafic to intermediate [76]. The Kurguvad granitoid samples RT13-146 and

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(a) (b)

1m 1m

RT13-146 1mm RT13-111 1mm

(e) (f)

qz bt plg plg

15NP247 1mm P09T33 1mm

Figure 3: (a) Field photograph of Kurguvad granite. (b) Field photograph of leucocratic granite in Gez. Maﬁc enclaves are well-visible. (c) Microphotograph of Kurguvad granodiorite with quartz, muscovite (bright purple and orange interference colors), and biotite (mute brown and green interference colors). Feldspars are very ﬁne-grained (Appendix 3(c)). (d) Microphotograph of a tonalite from Tajik Khingob valley shows intense alteration of feldspar and ductile straining of quartz. Secondary minerals are epidote, chlorite, and sericite. (e) Microphotograph of a granite sample from Chinese Taergelake valley showing epidote growth in the centers of feldspars and pale blue chlorite that replaced biotite. (f) Microphotograph of a trondhjemite sample from Chinese Gez valley with ductile quartz straining and brittle fracturing of plagioclase crystals. Note the zonation in plagioclase crystals. (c–f) All microphotographs are taken under cross polarized light.

RT13-149 and the Taergelake sample 15NP247 are classified Kurguvad granite. Due to the abundant epidote and chlorite, as granodiorites; all other samples are classified as tonalites we presume a greenschist facies metamorphic overprint of all when plotted in the Streckeisen diagram. All samples show granitoids of the North Pamir arc. Peak metamorphic evidence for ductile straining, as quartz grains show undu- conditions of the Kurguvad samples are estimated as lower lous extinction accompanied by various degrees of subgrain amphibolite facies. rotation recrystallization. Feldspars show idiomorphic habit and only gentle fracturing in the strained samples. Excep- 4.1.2. Volcanic Rocks. The North Pamir arc hosts a wide tions are the samples RT13-146 and RT13-149 from the variety of volcanic and volcaniclastic rocks (thin section pho- Kurguvad intrusion. Their feldspars are fine-grained and tographs in Appendix 2). We examined 8 samples from show recrystallisation patterns (Appendix 3(c)). In the mylo- basaltic to andesitic lava flows from Altyn Darya and the nitic sample 17NP426, feldspar formed an augen gneiss Qimgan valley. The lava flows are fine-grained and dark fabric and started to recrystallize to epidote and chlorite in brown to green. Abundant vesicles are filled with secondary the pressure shadows. From deformation patterns, we minerals, such as calcite. The greenish color and the abun- estimate a maximum temperature of clearly above 300°C dance of calcite in all samples suggest metasomatism and and below 500°C for most samples and maximum tempera- spilitization. The samples from Altyn Darya show a clear tures above 500°C for RT13-146 and RT13-149 from the greenschist facies metamorphic overprint and ductile

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straining. The lava flow samples show similar microscopic conservative discordance criteria d =1− ð206/238Þ/ð207/ features: plagioclase, as phenocrysts or microliths, is abun- 206Þ; this is recommended as both isotope ratios are mea- dant, with hornblende and rare olivine as phenocrysts. The sured directly in LA-ICP-MS dating and the lead isotope samples show hyalopilitic textures, sometimes trachytic ratio is more sensitive to lead loss. Method (3) uses an age- textures. dependent discordance criterion, i.e., for grains < 1000 Ma, d =1− ð206/238Þ/ð207/235Þ, and for grains > 1000, d =1− 4.1.3. Paragneiss. We made thin sections from two Kurguvad ð206/238Þ/ð207/206Þ. For the detrital zircon samples, we paragneiss samples, RT13-148 and RT13-185 from the Panj report ages (1) and (3). The two carbonate samples gave valley. Quartz and biotite are the dominant mineral phases lower intercept ages in the Tera-Wasserburg diagram. Gener- (thin section photographs in Appendix 4), accompanied by ally, peakfit ages were preferred for interpretations. There- garnet and minor amounts of feldspar and muscovite. Quartz fore, we take into account that single young discordant and feldspar show dynamic recrystallisation structures. The grains may have experienced lead loss but still are mathemat- ~150 μm garnets in sample RT13-148 have an inclusion- ically concordant due to their large age error [78] or due to rich core and a clear rim. Garnets in sample RT13-185 are the very narrow space between concordia and the discordia remnants of larger garnets (up to 500 μm) that were replaced line for young metamorphic events. Zircons from the gran- partially by chlorite and biotite (Appendix 4(a) and (b)). The ites and the aplitic dike show clear magmatic zoning in CL remaining garnet fragments have a dark core, packed with imaging. The zircons of paragneiss samples RT13-148 and small inclusions and a clear rim. The complex structure of RT15-11 are in part metamict. They do not show metamor- the garnets in RT13-185 hints at a multistage metamorphic phic overgrowths. history of the Kurguvad paragneiss. 4.2.1. Granitoids. We compiled zircon U-Pb ages from the 4.1.4. Qimgan Aplitic Dike and Carbonates. Carboniferous Chinese [28–31, 39] and Kyrgyz North Pamir [3] and reinter- pillow basalts are disconformably overlain by a predomi- preted these ages based on the criteria described above (see nantly clastic sequence in the Chinese Qimgan valley. A light Table 1). The Chinese studies focus on the tonalite outcrops grey, aplitic dike was sampled in the stratigraphically lower in the Gez and Oytag (Aoyitake) valleys 80 km SW of Kash- part of the Qimgan basin (Figure 2). It crosscuts upper Perm- gar. Of the published age data from the Oytag and Gez plagi- ian fine-grained clastic strata. The primary mineral phases ogranites in the Chinese Pamir, we extracted those ages have been substantially replaced by secondary minerals. A which fall into a range of ±10% of discordance. Those grains primary porphyritic texture can be inferred from the matrix reveal two age populations: a younger one around 330 Ma replaced by fine-grained, dirty secondary minerals and phe- and an inherited component of Ordovician to Silurian age nocrysts replaced by brownish-colored secondary minerals. [29]. The younger age population is often left skewed, In the lower part of the Qimgan basin, we collected two suggesting lead loss [78]. Therefore, we do not use the youn- carbonate samples for in situ U-Pb dating (Figure 4). Sample gest concordant zircon age for our interpretation. Previously 17NP438 is a sparry, light grey carbonate pebble from a red, published data of samples from the Oytag tonalite gave ages conglomeratic, clay-rich debris flow deposit. The conglomer- between 314 Ma and 331 Ma, the published data from ate contained clasts of serpentinites and sparry carbonates. samples in the Gez valley yielded an age of 338 Ma. The sampled carbonate clast contains planktonic foraminif- Our zircon U-Pb analyses of samples from the Tadjik era (Figure 4(a)) and unidentified shell fragments. Therefore, plagiogranites gave ages between 322 Ma and 340 Ma. we interpret the carbonate pebbles to be derived from marine Samples from the westernmost, most extensive intrusion carbonate deposits. The primary fabric of carbonate sample (~370 km2), spanning from Darvaz in the south to the Khin- 17NP472 is overprinted by sparry calcite. However, ostracod gob valley in the north, gave ages between 334 Ma to 339 Ma. shells and remnants of lacustrine algae can be discerned The samples taken from intrusions further to the east—two (charophytes, Figure 4(c)). The carbonate strata, interpreted from an intrusion cropping out in the Khingob valley and as lacustrine based on their fossil content, are interbedded one from the Kurguvad granite—gave slightly younger ages by fine-grained greenish siltstones and mudstones and occa- between 322 Ma and 334 Ma. Contrasting to those large sional cross-bedded sandstones. Most carbonate layers show intrusions, sample 15NP245 from a seemingly smaller intru- silicification and chert nodules. sion in the Chinese Taergelake valley, 120 km southwest of Kashgar, gave an age population of about 360 Ma. Zircons 4.2. New and Published Radiometric Age Data. An overview younger than 360 Ma from that sample do not form a coher- of the LA-ICP-MS U-Pb age data from all thirteen samples ent age group and are interpreted to be affected by lead loss. measured for this study as well as a compilation of literature data is provided in Table 2 (Figure 5). Detailed single-grain information from our own data is available in 1(a) and 4.2.2. Volcanic Rocks. There is almost no geochronologic data Appendix 7. available in the literature concerning the volcanic sequence of We report three ages for the igneous samples: (1) the age the North Pamir arc. Two andesites from the Kyrgyz Altyn of the youngest grain, (2) the median age of the largest age Darya valley yielded lower Mississippian ages of 355 Ma cluster calculated using the TuffZirc function of [77], and and 357 Ma (hornblende 40Ar/39Ar). Rhyolites dated in the (3) the peakfit function of [67]. (2) and (3) give largely similar same study with ID-TIMS on zircon gave a U-Pb age of results for our data sets. For (1) and (2), we used the more 329 Ma [3].

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200 �m

0.8

0.6

U 238

4000 Pb/

0.4 17NP438 (60 points) 206 347.0±7.6 Ma 3000 MSWD = 2.2

0.2 2000 1000

(a) 0 2 4 6 8 207Pb/235U (b)

� 17NP472 (34 points) 100 m 1.4 260.5±2.2 Ma

1.2 MSWD = 3.4

1.0

U 5000 238

0.8

Pb/ 206

0.6 4000

0.4 3000 0.2 2000 1000 500

0.0 (c) 0 5 10 15 207Pb/235U (d)

Figure 4: Microscopic images of carbonate sample 17NP438 ((a, b) carbonate pebble from a red conglomerate) and sample 17NP472 ((c, d) lacustrine carbonate) both from the lower part of the Qimgan basin, Chinese North Pamir. (a) Foraminifera in plane polarized light. (b) U-Pb Tera-Wasserburg concordia plot of calcite age data from sample 17NP438; 1σ-age-error is used. (c) Charophyte oogonium (white arrow) in a micritic carbonate overgrown by sparry calcite. (d) U-Pb Tera-Wasserburg concordia plot of calcite age data from sample 17NP472; 1σ-age- error is used. Data points not used for regression are in white.

450 450 450 0.070 RT13-108 0.070 RT13-109 450 0.070 RT13-111 0.070 RT13-115 333.55±0.44 Ma 329.34±0.59 Ma 339.11±1.23 Ma 334.92±0.52 Ma 400 400 400 400 n = 33 n = 25 n = 34 n = 28 0.060 0.060 0.060 0.060

0.050 0.050 0.050 0.050 300 300 300 300

0.040 0.040 0.040 0.040 U

238 0.30 0.40 0.50 0.30 0.40 0.50 0.30 0.40 0.50 0.30 0.40 0.50

Pb/ 450 450 450 450 206 0.070 RT13-146 0.070 16NP341 0.070 16NP342 0.070 15NP245 322.14±0.66 Ma 337.43±0.38 Ma 339.96±0.46 Ma 360.52±0.35 Ma 400 400 400 400 n = 25 n = 47 n = 32 n = 38 0.060 0.060 0.060 0.060 3500 3500 0.050 0.050 0.050 0.050 300 300 300

0.040 0.040 0.040 0.040 0.30 0.40 0.50 0.30 0.40 0.50 0.30 0.40 0.50 0.30 0.40 0.50 207Pb/235U

Figure 5: U-Pb Wetherill concordia plots of zircon U-Pb data from granitoid samples. All data points were plotted; however, for age calculation, only those with −10% < discð6 38/7 6Þ <10% were used. Displayed ages are calculated using the peakﬁt algorithm [67]. Error ellipses are shown semitransparent; overlapping error ellipses cause darker colors.

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4.2.3. Paragneiss. Two samples were taken from the meta- and the Altyn Darya valley [3] in Kyrgyzstan (Figure 8). morphic Kurguvad basement complex in Tajikistan. RT15- There is a large similarity amongst the volcanic rocks from 11 is from a unit mapped as granite. It was identified as a the Chinese North Pamir and the Altyn Darya valley. There- metasediment from the hand specimen; zircon ages show a fore, we present and plot our whole rock geochemical data similar distribution as detrital grains from paragneiss sample from the volcanic rocks together with literature data from RT13-148 (Figure 6(a)). Both samples, RT15-11 and RT13- the Chinese volcanic rocks in Oytag and Gez and Altyn 148 have age peaks at around 580 Ma, 722 Ma, and 943 Ma Darya, as they complement each other. The new geochemical and two minor age peaks at 2.0 Ga and 2.6 Ga (Figure 6, data from this study are presented in Appendix 8. Appendix 1(b) and (c)). Age peaks were calculated for both samples together, using the discrete mixture modelling algo- 4.3.1. Granitoids. The granitoids of the North Pamir arc show fi rithm [79] implemented in the peak t function of IsoplotR SiO2 content between 63 and 78 wt%, MgO values between [67]. We show that the Kurguvad complex was intruded by 0.3 wt% and 3.1 wt%, and Al2O3 content between 12 and a tonalite (RT13-146) at around 322 Ma. Therefore, a concor- 16 wt%. They show relatively high Na2O values between 4 : : dant grain in RT15-11 which yielded an age of 200 8±18 and 6 wt% and low K2O values between 0.1 and 4.2 wt%. Ma was classified as metamorphic and not included in the They can be classified as peraluminous to metaluminous age peak calculation. The limited number of measured detri- using the A/NK versus A/CNK plot of Shand (Figure 9 tal zircon grains (RT15-11: 51 mounted, 25 measured; RT13- [80]). CIPW normed samples from the Oytag/Gez plot in 148: 120 mounted, 82 measured) allows for identification of the trondhjemite field of the albite-anorthite-orthoclase major age peaks. diagram (Figure 7(b) [81]). Samples from the Tajik plagiogranites show a larger variability and higher normative 4.2.4. Qimgan Aplitic Dike and Carbonates. To constrain the anorthite (Ca) content (RT13-149, RT13-111) or higher nor- minimum age limit of the activity of the North Pamir arc, we mative orthoclase (K) content (RT13-108, RT13-115, and dated two carbonates and a crosscutting aplitic dike from the 15NP247). Samples RT13-146 and RT13-149, which show lower part of the Qimgan basin, 50 km to the northwest of the orthoclase and plagioclase in the thin section, plot along the Oytag valley. The aplitic dike (sample 17NP439) yields two tonalite-granodiorite border. The plagioclase cumulate sam- zircon age populations: 250 Ma and 417 Ma (Appendix 1(d) ple 16NP342 from the Tajik Kalai Khumb intrusion is an and (e)). It crosscuts the lower part of the Qimgan basin. exception, with a low SiO2 content of 43 wt% and high The inherited, older age peak is younger than inherited grains Al2O3 (27 wt%), MgO (5 wt%), and CaO (15 wt%) content. reported from the Gez plagiogranite (448 Ma and 468 Ma All samples can be classified as calc-alkaline. Rare earth ele- [29]). Carbonate samples were collected from a red con- ment (REE) data normalized to chondrite [82] from the glomerate containing serpentinite and limestone pebbles Oytag tonalites plot parallel to the N-MORB composition (17NP438) and a dark lacustrine limestone (17NP472). Sam- (Figure 7(c)) and show no to slightly negative Eu anomalies. ple 17NP438 gave an age of roughly 347 Ma from 60 single The Tajik granitoids show enriched light REE compared to ablation spots; sample 17NP472 yielded an age of 260 Ma chondrite, more pronounced depleted Eu, and lower from 34 single ablation spots (Figures 4(b) and 4(d)). These amounts of heavy REE compared to the Oytag tonalites. are lower intercept ages from the Tera-Wasserburg diagram. Plagioclase cumulate sample 16NP342 shows very low REE Outliers were carefully excluded in order to optimize the amounts and a strong positive Eu anomaly. C1 chondrite goodness of fit (weighted MSWD value). [83] normalized La/Lu ratios fall between 0.6 and 1.6 in the Chinese tonalites and between 4 and 10.5 in the Tajik granit- 4.3. New and Published Whole Rock Geochemistry. We com- oids. The Taergelake granite has a normalized La/Lu ratio of piled published whole rock geochemistry data for granitoids 10.8. The granite and two monzonite samples from East from the Oytag [28, 29, 31] and Gez sections [29] in the Mazar have the highest normalized La/Lu ratios of 11.8, Chinese North Pamir and a tectonic sliver near Mazar [39] 14.2, and 17.6 [39]. Trace element data reveals Rb content along the Karakax fault system in the Chinese West Kunlun. between 0.6 and 14 ppm in the Gez and Oytag tonalites [28, There is an extensive database of major element whole rock 29, 31] and between 26 (16NP341) and 131 ppm (RT13-115) geochemical data from intrusive rocks from the North Pamir in the Tajik granitoids. Ni content generally ranges between arc in Tajikistan by Mamadjanov et al. [54] with which we 0.34 and 3.20 ppm with enrichment in RT13-111 (15.73 ppm) compare our data and the data from the Chinese granitoids and 16NP342 (48.51 ppm). Th content is between 1.03 ppm (Figures 7(a) and 7(b)). They interpret the occurrence of gab- (17NP426) and 23.37 ppm (RT13-108). U concentrations are bro and tonalites/plagiogranites as a continuous series of five between 0.29 ppm (17NP426) and 4.67 ppm (RT13-108). Pla- major phases: emplacement of (1) gabbro, (2) quartz diorites, gioclase cumulate sample 16NP342 shows a very primitive sig- (3) tonalites, (4) plagiogranites, and (5) leucoplagiogranites. nature with Th content of 0.04 ppm and U content of 0.01 ppm. Mamadjanov et al. [54] report trace elements as bulk analy- Plotting the granitoids in the Rb versus Y and Nb classification sis; those data were not used in our comparison. The granit- scheme [84], most samples fall in the field of volcanic arc gran- oids intruded in most places into a thick pile of basic to ites (Figure 10). The granitoids show a typical arc signature; intermediate volcanic and volcaniclastic rocks. however, this signature is not homogenous along the strike of We also compiled whole rock geochemical data from the North Pamir arc. The tonalites in Oytag are depleted and volcanic rocks from the Oytag section [28] in the Chinese show a strong mantle influence, while the Tajik and East Mazar North Pamir, East Mazar [39] in the Chinese West Kunlun, granites are more enriched.

Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/doi/10.2113/2021/6697858/5292906/6697858.pdf by guest on 30 September 2021 on 30 September 2021 by guest Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/doi/10.2113/2021/6697858/5292906/6697858.pdf Lithosphere ot inSa.Smlsfo h ugvdBdksa ope rsne yL ta.[0 r lte sadse ie a )Nt that the Note of c) of block (a, ages line. basement (b). dashed U-Pb Garm KDE a the detrital the as plot in plotted of to are found plot used [40] gneisses not al. KDE are from was et peaks (e) which Li [110] Age component, by paragneiss. al. [110]. metamorphic presented Kurguvad et a al. complex show the Konopelko Kurguvad-Badakhshan et samples the from Konopelko of both from data from protolith Samples (e) detrital Shan. the in Tien and for South used RT15-11 age were and that depositional RT13-148 samples maximum samples the Ediacaran 1σ from an including ages 1σ below, indicate U-Pb listed including concordant are all below, peaks of Age listed plot complex. Radial Kurguvad-Badakhshan the (c) in brackets. collected rocks metamorphic for 1σ including below, Figure :Dtia icnUP aa a ailpo 18 hw -baedsrbto fsmlsR1-4 n T51.Aepasaelisted are peaks Age RT15-11. and RT13-148 samples of distribution age U-Pb shows [118] plot radial (a) data: U-Pb zircon Detrital 6: erradpoaiiyi rces b ailpo falcnodn -bae rmtesmlspeetdi ie l [40] al. et Li in presented samples the from ages U-Pb concordant all of plot Radial (b) brackets. in probability and -error 0 ⁎⁎ ⁎ samples 11,12,and 17from Konopelko etal. [111] samples from etal. Li [41] erradpoaiiyi rces d ehrl ocri lto ape T318adR1-1 They RT15-11. and RT13-148 samples of plot concordia Wetherill (d) brackets. in probability and -error 2660.4±7.4 (0.05) 942.8±2.2 (0.16)|2012.4±5.8(0.12) 579.8±0.8 (0.36)|721.5±1.1(0.31) 3370.3±8.6 (0.05) 1821.0±12.0 (0.08)|2545.5±6.0(0.20) 615.0±2.1 (0.20)|801.9±2.1(0.48)

| Standardised estimate Standardised estimate –2 –2 2 2 ± 2 0 0 400 200 0 100 0 7.4 .2 (0.16 .8 (0.36) Metamorphic Det M Detrita Metamorphic Detrital Metamorphic Detrital n n n =94/107 n =48/51 = 48 = 94 etamor ( 500 0.05 rit al / / )|2 l 51 107 100 | ( (a) (c) ) 721.5±1.1 (0.31) t/� a) 012.4±5.8 (0.12) p hic t/� t/ � 2 200 0 0 1000 3500 3 200 300 500 2800 2000 2000 2000200 500 500 1000 100 500 1000100 0 0 0

206Pb/238U Age (Ma) 0.1 0.2 0.3 0.4 0.5 0.3 0. 0 0.2 .5 1500 4 02468 1 6 3 1890.3±4.1 (0.11) 631.7±0.7 (0.39)|891.0±1.2(0.26) 341.2±0.8 (0.07)|483.7±1.0(0.14) 890.3±4.1 31.7±0.7 (0.39 41.2±0.8 (0.07)

(e) StandardisedStandardised estimateestimate –2 500 2 2 0 0 n n =399/747 =399 ( 0.11 2000 )|8 2000 2000 | / 200 ) 483.7±1.0 (0.1 747 91.0±1.2 (0.2 ( (b) b)

0.00 0.05 0.10

207

0.0 400 400 Kurguvad-Badakhshan

Pb/ 0 200 RT13-148 (n=74/82) (d)

235 6 4 RT15-11 (n=20/25) 400 2500

U Garm 2500

0.5 3300 600 10 2000 300 500 1000 (n =399/747) ⁎ (n=37/51)

1.0 12 800 1000 ⁎⁎ 14

1.5 3000 erradpoaiiyin probability and -error 13 14 Lithosphere

An Tawite/Urtite/Italite 1000

Foid 100

syenite Foidolite Foid

2 monzo- Syenite 10 syenite Foid 10 O+K Quartz

2 monzo- gabbro Monzonite monzonite Grano- Na Monzo Granite Foid diorite diorite

Sample/REE chondrite gabbroMonzo- Tonalite gabbro 5 V 1 Quartz IV

monzonite

Granodiorite

Gabbro Diorite diorite I Gabbroic III Quartzolite La Pr Pm Eu Tb Ho Tm Lu gabbro II Peridot Granite 0 Trondhjemite 40 50 60 70 80 90 Ab Or Ce Nd Sm Gd Dy Er Yb SiO2

Plutonic series of the Tajik Tajik granitoids Oytag gabbro indrusives of the KOB (Kalai Khumb, Khingob, (Ji et al. [29]) according to Mazar granitoids Panj, Kurguvad) Mamadjanov et al., 2017 (Li et al. [40]) Gez/Qytag plagiogranites Gabbro phase (I) Taergelake granitoid (open rectangles: Ji et al. [29]; Diorite and quartz Kang et al. [32]; Jiang et al. [30]; ) diorite phase (II) Tonalite phase (III)

Plagiogranite phase (IV)

Leuco-plagiogranite phase (V)

Figure 7: Geochemical characteristics of the North Pamir arc intrusive rocks. (a) General calc-alkaline trend of the North Pamir arc intrusive rocks. Our data supplements the extensive database of Mamadjanov et al. [54] collected from the Carboniferous intrusive rocks in the Tajik part of the North Pamir arc. (b) Ab-An-Or diagram [81] for all granitoids of the North Pamir arc. (c) REE pattern for intrusive rocks cluster densely according to their outcrop region.

6 10 1000 5 oleiite series 5 4 100 3 2 Calc-alkaline 2 series 10 FeOt/MgO 1

1 (La/0.237)/(Lu/0.0246)

Sample/ REE chondrite Sample/ La Pr Pm Eu Tb Ho Tm Lu 1 0 Ce Nd Sm Gd Dy Er Yb 45 50 55 60 65 70 75 30 40 50 60 70 80 SiO2 SiO2 Ocean island basalt Oytag Altyn Darya (Ji et al. [29]) (rectangle: Schwab et al. [3]) N-MORB Qimgan/Akqi Mazar (Li et al. [40])

(a) (b) (c)

Figure 8: (a) Volcanic rocks from the North Pamir arc generally plot along a tholeiitic trend [88]. It is unclear whether the volcanic rocks from East Mazar also follow this trend. (b) C1 chondrite normalized La/Lu ratios are low for all basalt and andesite samples from the North Pamir arc. Samples from East Mazar show the highest values. (c) Volcanic rocks from Oytag and Qimgan show a ﬂat REE pattern; those from Altyn Darya show a ﬂat to slightly LREE enriched pattern. East Mazar rocks are most enriched in LREE.

4.3.2. Volcanic Rocks. The SiO2 content in volcanic rocks hand specimens and thin section observations, all volcanic from the North Pamir arc ranges from 38 wt% in the Qimgan samples were altered. Ocean floor metasomatism caused spil- fl valley to 54 wt% in Altyn Darya. These samples show Al2O3 litization of the basaltic to andesitic lava ows. The volcanic content between 13 and 17 wt% and MgO content between rocks in the Altyn Darya valley have been strongly affected ff 3.7 and 9.3 wt%. K2O content is relatively low (0.05 to by greenschist facies metamorphism. General e ects of low- 1.59 wt%) while Na2O values are high (1.8 to 5.4 wt%). They T/low-P overprints on geochemistry are described elsewhere can be classified as metaluminous using the A/NK versus [85–87]. In all samples, we presume that mobile elemental A/CNK plot of Shand (Figure 9 [80]). As is evident from abundances have been disturbed. Therefore, classification

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7 7

6 Metaluminous Peraluminous 6 Metaluminous Peraluminous

5 5

4 4 A/NK A/NK 3 3

2 2

1 1 Peralkaline Peralkaline 0 0 0.6 0.8 0.0 1.2 1.4 0.6 0.8 0.0 1.2 1.4 A/CNK A/CNK Volcanic rocks Plutonic rocks

Altyn Darya Qimgan/Akqi Tajik granitoids Qytag gabbro (rectangle Oytag (Kalai Khumb, Khingob, (Ji et al. [29]) Schwab et al. [3]) (Ji et al. [29]) Panj, Kurguvad) Mazar (Li et al. [40]) Taergelake granitoid Mazar granitoids (Li et al. [40]) Gez/Qytag plagiogranites (open rectangles: Ji et al. [29]; Kang et al. (32) ; Jiang et al. [30])

(a) (b)

Figure 9: Classiﬁcation plots after Shand [80] for volcanic (a) and plutonic (b) rocks of the North Pamir arc. Gray symbols in (b) are plutonic rock analysis presented by Mamadjanov et al. [54] (for the explanation, see Figure 7).

FeOt/MgO ratios than the samples from the Gez and Oytag 1000 valleys but are similar to those from Qimgan. The K2O versus syn-COLG silica plot does not show such a trend, as potassium, similar WPG to sodium, rubidium, and strontium, is highly mobile even during low temperature alteration [89, 90]. To get a robust geotectonic classiﬁcation, we use the multiple major element 100 classiﬁcation scheme of Verma et al. [91]. The scheme is only % applied to samples with SiO2 <52wt . Most samples plot in

Rb the island arc basalt field (Figure 11(a)). Likewise, in the Zr/Y versus Y plot [92, 93], most samples plot in the island arc fi 10 basalt eld (Figure 11(b)). Rare earth element (REE) data normalized to chondrite [82] show variable patterns, varying from flat to slightly depleted light REE to moderately enriched light REE pattern (Figure 8(c)). C1 chondrite [83] VAG ORG normalized La/Lu ratios fall between 1 and 2 for most sam- 1 ples (Figure 8(b)). A basalt from Oytag shows the lowest ratio 1 10 100 1000 of 0.5, similar to N-MORB [94]. Most andesites from Altyn Darya (e.g., AD1a, AD7c, and AD6e [3]) have values above Y+Nb 2; samples from East Mazar (D534/6, D1029/1-4, and Figure 10: Y+Nb versus Rb classification [84]. For explanation of D1029/1-3 [39]) have the highest values between 6.9 and symbols, see Figure 5. syn-COLG: syn-collisional granites; WPG: 8.5. Enrichment of light REE (Figure 8(c)) may be connected within plate granites; VAG: volcanic arc granites; ORG: orogenic to contamination with continental material. Cr values range granites. between 178 ppm (15NP233-1) and 431 ppm (15NP234); two samples yield Cr < 10 ppm (2011T49 and 01-09-13-01). schemes based on mobile components should be handled with care. All samples fall within a tholeiitic series based on 4.4. Results of XRD Analysis of Selected Granite Samples. the FeOt/MgO versus silica diagram (Figure 8(a) [88]). How- Powder XRD analysis was performed on seven granitoid ever, samples from the Altyn Darya valley show higher samples to determine the generally very fine-grained

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8 20

CRB

4 10 IAB OIB Within plate basalt

–4 5

Zr/Y DF2

Island arc Midocean ridge basalts –4 2 basalts MORB

–8 1 –8 –4 0 4 8 10 20 50 100 200 500 1000 DF1 Zr (a) (b) Figure ﬁ % ﬁ 11: Geotectonic classi cation of basaltoid samples with SiO2 <52wt . (a) Multielement classi cation after Verma et al. [91]. OIB: ocean island basalt; MORB: midocean ridge basalt; CRB: continental rift basalt; IAB: island arc basalt. (b) Zr vs. Zr/Y by Pearce and Norry [93]. For explanation of symbols, see Figure 6.

secondary and alteration mineral phases. When the abun- low normalized La/Lu ratios. Granitoids with tonalitic to dance of mica in the sample is low, white and dark mica can- granodioritic composition intruded the volcanic sequence. not be distinguished by their X-ray diffraction spectra. A minimum age for arc volcanism initiation in the North Therefore, data must be cross-checked with results from pet- Pamir is given by the 360 Ma Taergelake granodiorite (sam- rographic thin section examination. Results are summarized ple 15NP245, Figure 5) and 40Ar/39Ar hbl ages of ~357 Ma in Table 1. The XRD measurements confirm the presence of from andesites in the Altyn Darya valley [3]. The 360 Ma typical greenschist facies mineral assemblages. Chlorite and Taergelake intrusion has the oldest U-Pb age and the highest epidote are common. The spectra of sample 16NP342 show REE enrichment of all Chinese granites in this study. This is evidence of clinozoisite and zoisite. The spectra of sample remarkable, as it represents a more evolved granitoid com- RT13-111 suggest the presence of actinolite. All plagioclases pared with the later-intruded Oytag tonalite, for example. are identified as albite and in some samples as oligoclase. So far, there is no good explanation for this. The younger Potassium feldspars are of microclinic composition. XRD age limit is presently defined by the youngest plutons in the results agree well with whole rock CIPW normed feldspar Oytag valley, Chinese North Pamir [28], by the onset of classification (Figure 7(b)). upper Permian continental deposition in the Chinese Qim- gan basin (Figure 2), and by the overlying, amagmatic, and 4.5. Results of EDX Analysis of Garnets from Kurguvad Bashkirian carbonate sedimentation in the Tajik North Basement Block. We used EDX to analyze polished thin Pamir [53]. The major preserved intrusive phase happened sections of two biotite-garnet gneiss samples from the Kurgu- between 340 and 320 Ma, coevally in the Chinese and the vad basement block. They yielded two types of garnet. Semi- Tajik North Pamir. Despite differences in geochemical com- quantitative EDX analysis on a scanning electron microscope position, all granitoids from that time interval show similar reveals gentle zoning for the large, multistage garnets of petrographic properties and a relatively primitive composi- sample RT13-185 and stronger zoning for the small, clearer tion. The granitoids of the Tajik North Pamir exhibit a garnets from sample RT13-146. Garnets show high alman- generally more enriched REE pattern and a more pro- dine (XFe2+) values around 80 mol% in sample RT13-185 nounced negative Eu anomaly compared with those from and around 70 mol% in sample RT13-146. The pyrope the Oytag and Gez tonalites (Figure 7 and Appendix 8 (XMg) values are generally highest in the core, and spessar- [28, 29, 31]). The more enriched nature of the Tajik granit- tine (XMn) values increase toward the rim (Appendix 5). oids might reflect a higher grade of continental contamination within the mantle wedge due to the presence of the 5. Discussion Kurguvad continental basement block. The same can be stated for the East Mazar granites, which probably intruded 5.1. Ages and Tectonic Setting. Our new geochemical results in the vicinity of the Tianshuihai complex as a result of a and compiled data confirm the existence of a volcanic North Carboniferous reactivation of the Proto-Tethys subduction Pamir arc, which was active from the latest Devonian to zone [24]. However, interpretation of the East Mazar gran- Bashkirian—for at least 50 Ma. Basaltic to andesitic rocks ites is hindered by their incorporation into the Karakax are characterized by typical arc tholeiitic compositions and fault zone.

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The vergence of the subduction zone cannot be con- 5.3. Comparison between the West Kunlun and the North strained by our data. The southern margin of the North Pamir. The North Pamir arc is clearly distinguishable from Pamir arc is largely overprinted by the late Triassic-early the two major volcanic arcs recorded in the West Kunlun, Jurassic Cimmerian orogeny. The northern margin is defined where volcanism occurred during the closure of the Proto- by the Cenozoic Main Pamir thrust, which has a larger offset Tethys and collision of the Tianshuihai, South Kunlun, and in the western portion of the North Pamir arc. To the east of North Kunlun/Tarim blocks in the Silurian and Ordovician Taergelake, the position of the Main Pamir thrust is not well- times [14, 19, 20, 98, 102], as well as during the closure of constrained. Our field data from Qimgan valley (Figure 2 the Paleo-Tethys and accretion of the Cimmerian blocks [41]) shows that the northern margin of the North Pamir [13, 21, 23, 103]. Volcanic rocks overlapping in age with Arc is covered by Permo-Triassic to Eocene sedimentary the two major tectonothermal events of the West Kunlun rocks. have not been discovered in the North Pamir arc. Similarly, there are no arc volcanic rocks of Carboniferous age 5.2. The West Kunlun and the Kudi Suture. The Kudi section, described from the West Kunlun. Instead, West Kunlun Car- situated along the Xinjiang-Tibet highway south of Kargilik, boniferous deposits represent amagmatic, shallow marine is the type locality for the West Kunlun. The North and siliciclastic and platform carbonate successions [104]. South Kunlun terranes are separated by the mid-Paleozoic Although pillow basalts, lava flows, and related clastic rocks Kudi suture [10, 11, 18, 95, 96]. The South Kunlun block is from the Yixiekekhgou area, north of the town of Kudi, were an accretionary complex formed between the colliding North previously interpreted as Carboniferous (Wang, 1996), a Kunlun (the southern margin of Tarim) and Tianshuihai dacite from that section yielded a zircon U-Pb age of 492 ± blocks [13, 24]. The South Kunlun terrane is characterized 9Ma[19]. by an early Paleozoic accretionary sequence, pre-Cambrian The Oytag (or Wuyitake) suture—namely, a small out- sedimentary sequences, Cambrian ophiolites, and Silurian crop of ultramafic rocks—is only found in the Gez valley to Ordovician arc volcanic rocks [13, 19, 97]; none of these [105]; no definitively correlative outcrops are known from are found in the northeastern Pamir. Closure of the Kudi the North Pamir arc to the west. A connection between Kudi suture is dated as lower Silurian by a 440 Ma monazite age and Oytag ultramafic rocks has long been proposed [3, 11, of the Saitula group of the South Kunlun [13], reflecting 106–108]. This led to the interpretation that the Kudi- initiation of large scale obduction of metamorphic units Oytag suture zone, separating the North and South Kunlun due to collision of South and North Kunlun. terranes, stretches from the West Kunlun all around the The West Kunlun experienced two major intrusive phases: North Pamir. This terminology has been applied despite mis- between 530 Ma and 400 Ma and between 240 Ma and 200 Ma matching geochemical and especially geochronological data (Figure 12). The older intrusive phase in the West Kunlun from the granitoids in the Gez/Oytag section [29, 30]. The domain extends as far north as the shoshonitic Datong pluton arc volcanic rocks of the Gez/Oytag section were related to (~450 Ma [98, 99]). The Yirba granodiorite (Figure 12(a)), an intraoceanic subduction zone [29, 106] and have an island cropping out in the Kudi section, intruded between 460 and arc tholeiitic character. Volcanic rocks from the Kudi ophio- 471 Ma during the mature phase of the Andean-type mag- lite show a wide range of geochemical characteristics; they are matic arc in the West Kunlun [19]. The Datong pluton interpreted as N- and E-MORB ridge basalts [19], back-arc (Figure 12(a)), emplaced between 448 and 473 Ma [100], like- basin tholeiites, low-Ti island arc tholeiites, and island arc wise belongs to the mature phase. It marks the present, north- tholeiites [18, 20]. As geochronological information on the westernmost extent of the early Paleozoic plutons preserved in volcanic sequences is sparse, discrimination was difficult. the West Kunlun. The Andean-type arc developed on top of a However, amphibole and biotite 40Ar/39Ar ages from the north (e.g., [19]) or south (e.g., [13, 24]) dipping subduction Kudi ophiolite suggest a formation age prior to 460 Ma zone with Proto-Tethyan oceanic crust being subducted [18]. Hornblende 40Ar/39Ar ages from andesites of the between the North Kunlun, regarded as Tarim crust, and the Kyrgyz Altyn Darya valley yield ages of roughly 350 Ma [3], Tianshuihai block. An accretionary complex—the South so 100 Ma younger than Kudi. Kunlun terrane—formed along the subduction zone. By that The difference between the North Pamir and the West time, the South Kunlun accretionary complex experienced Kunlun is even more obvious when comparing granitic amphibolite facies metamorphism due to crustal thickening, intrusion history and metamorphism. Granites of the North subduction of the Proto-Tethys, and later collision of the con- Pamir arc show relatively uniform tonalitic to granodioritic tinental block related to the Tianshuihai complex [13, 19]. composition and are not older than 360 Ma, with the main Proto-Tethys subduction terminated in a late Silurian to early intrusive phase between 340 and 320 Ma. No postcollisional Devonian postorogenic stage with emplacement of highly granitoids have been identified. In contrast, the granitoids evolved A-type granites [14, 101]. Since at least the emplace- of the West Kunlun are much older and show a higher com- ment of the A-type North Kudi pluton at around 405 Ma positional variability, including postcollisional A-type granit- [14], the postorogenic extensional phase marks the termina- oids. Granitoids from all three volcanic phases (early tion of compressional, subduction-related tectonics in the Paleozoic, late Paleozoic, and Triassic) are related to subduc- West Kunlun. Plutons associated with the younger, Permo- tion processes. Thus, they show similar trace element Triassic phase can be found in the West Kunlun as well as in features. However, the Carboniferous granitoids are the least the Tianshuihai and in the Karakul-Mazar accretionary com- enriched ones (Figure 12), suggesting a higher mantle influ- plex, which forms the southern part of the North Pamir. ence during that phase. Metamorphism in the North Pamir

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Oytag/Gez 1000 Yuqikapa Bulunkou Tarim Muztagh Datong Kusilafu 100 Taer

Beileki 00.83 Qiukesu Tarim craton Karakorum fault Yirba North Kudi 10 North Kunlun terrane

Tiekelike South Kunlun fault Buya

terrane 76.63 1

Arkaz Jiajiwaxi East Mazar Tianshuihai Cs Ba U K Ce Pr P Zr Eu Dy Yb Karakorum terrane 0.1 76.00 terrane 78.00 80.00 Rb Nb La Pb Sr Nd Sm Ti Y Lu

West Kunlun S-D (a) West Kunlun O (b) 1000 10000

1000 100

100 10

1 1

Cs Ba U K Ce Pr P Zr Eu Dy Yb Cs Ba U K Ce Pr PZrEu Dy Yb 0.1 0.1 Rb Nb La Pb Sr Nd Sm Ti Y Lu Rb Nb La Pb Sr Nd Sm Ti Y Lu

Tajik N-Pamir uD-C West Kunlun T Mazar uD-C Chinese N-Pamir uD-C (c) (d)

Figure 12: (a) Map of West Kunlun (polygon outlines after Zhang et al. [116] and own interpretations). Granitic intrusions which were used for this comparison are labelled; early Paleozoic intrusions are shown in green, late Paleozoic are shown in purple, and Triassic intrusions are shown in red. Transition from South Kunlun terrane toward the North Pamir arc is unclear (red question mark). (b–d) Spider diagram with element concentrations normalized against primitive mantle [94]. Comparison between early Paleozoic granitoids (O: Ordovician; S-D: Silurian to Devonian), late Paleozoic granitoids (uD-C: Upper Devonian (only Taergelake granite) to Carboniferous), and Mesozoic granitoids (T: Triassic). Data compiled from (b) early Paleozoic plutons Datong [98], Kusilafu [98], Yirba [14], Qiukesu [119], Buya [120], and North Kudi [14]; (c) late Paleozoic plutons (see Figure 1) Taergelake, Kalai Khumb, Obikhingou, Kurguvad, Panj (own data), and East Mazar [39], Gez [29], and Oytag [28, 29, 31]; and (d) Mesozoic plutons Yuqikapa [21], Muztagh [21], Bulunkou [121], Beileki/Taer [23], Taer [119], Karakul (not shown in (a) [3]), Arkaz [14, 121, 122], and Jiajiwaxi [123].

arc reached a maximum of lower amphibolite facies post- that a remnant of the Proto-Tethys remained open in the 320 Ma, while the West Kunlun experienced amphibolite NE Pamir until the Cimmerian orogeny [24]. Therefore, we metamorphism between 440 and 430 Ma [13, 109]. speculate that collisional tectonics in the West Kunlun termi- If there is a continuation of the Oytag subduction zone nated westward, toward the North Pamir, during the early toward the east, it should be situated south of the South Paleozoic orogeny. Kunlun but not within the collision zone between the North Geochemical data compiled from previous studies of the Kunlun, the South Kunlun, and the Tianshuihai complex. early Paleozoic and early Mesozoic intrusive rocks show The East Mazar sliver might give a hint of a continuation of certain similarities with the geochemical signature of intru- the subduction zone between the Tianshuihai complex and sive rocks discussed in this study (Figure 12). All are related the South Kunlun in the westernmost part of the West to subduction processes. The magmatic suites show negative Kunlun. Based on sedimentary facies and the lack of evidence Nb, P, and Ti anomalies. The tonalites from the Oytag/Gez for Paleozoic orogenesis in the NE Pamir, it is also argued section show the least enrichment in large ion lithophile

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elements (LILE). Their enrichment is higher in the Tajik a youngest age peak at around 310–360 Ma. This age peak granitoids. Compared with the Triassic and early Paleozoic likely reflects magmatic activity of the North Pamir arc. All intrusive rocks, the Carboniferous magmatic suite is less other samples of that dataset together with our data from enriched in LILE. The enrichment in LILE and depletion of samples RT13-148 and RT15-11 lack that peak. We show high field strength elements (HFSE) such as Nb, P, and Ti that a granodiorite intruded into the metamorphic Kurguvad is typical for subduction-related environments. Therefore, basement in the Bashkirian. The new findings can be inte- the Carboniferous granitoids show a stronger mantle compo- grated to a sequence of processes affecting rock units of the nent than the Triassic and early Paleozoic granitoids. NW Pamir. (1) The lower metamorphic grade of the Early Carboniferous Kurguvad granodiorite, compared to the sur- 5.4. Relationship of the North Pamir Arc with Carboniferous rounding metasediments (e.g., garnet-biotite schist and Rocks in the Afghan Badakhshan. For the Carboniferous garnet-staurolite schist), strongly supports the existence of units of the Tajik North Pamir and their continuation into at least one preintrusion metamorphic phase in the Kurgu- Afghanistan, a simple division into two zones was proposed vad basement. (2) The presence of Carboniferous zircon in by Bazhenov and Burtman [33]. Zone 1 represents oceanic metasedimentary rocks, presented by Li et al. [40] just a few crust, characterized by early Paleozoic volcanics and interca- kilometers southeast of the Kurguvad intrusion, indicates lated open marine sediments. Carboniferous ultramafic units late- to post-Carboniferous metamorphism. Metasediments were also described from this zone [34, 50]. Zone 2 represents yielding Carboniferous age peaks might reflect nappes of a an active margin, characterized by arc volcanic rocks and Carboniferous accretionary wedge. accreted microcontinents (Kurguvad block, Fayzabad micro- Peaks similar to the ones found in the Kurguvad block are continent). Middle Paleozoic rocks sharing characteristics known from gneisses of the Garm block in the Tajik Tien with those zones can be found from the North Pamir into Shan [110–112] and the Kyzylkum segment of the South the Herat area and further west [33]. We do not follow this Tien Shan (Mirkamalov et al. [113] cited in [110] and Kono- bipartite division, as arc tonalites and granodiorites appear pelko et al. [42]). These ages indicate an Ediacaran maximum to intrude both units. Instead, we interpret the arc to have depositional age (Figure 6) and suggest a linkage of the Kur- formed on top of both pre- to early Carboniferous oceanic guvad basement block to the Tien Shan basement at that crust and continental slivers. It is likely that the Kurguvad time. A very pronounced 590 Ma age peak is also reported microcontinental block separated from other Tarim-related from NE Gondwana [114]. The 943 Ma age peak may be crustal blocks of the region (e.g., Garm) in the early Paleo- related to igneous activity in Tarim, as suggested for a simi- zoic, leaving behind a patchwork of oceanic and continental lar age peak between 1150 Ma and 800 Ma in the Garm crustal fragments—which later were accreted during subduc- gneisses [110]. The older age peaks at 2 Ga and 2.6 Ga are tion processes in the Carboniferous. Subduction zones may less pronounced in the Kurguvad gneiss. Similar peaks are have formed along the flanks of microcontinental blocks reported from samples taken in the Quruqtagh, Central Tien during the middle-late Carboniferous compressive phase. Shan, that represents the Precambrian Tarim basement Another feature that can be followed into the Badakh- [115]. Shu et al. [115] link the late Archean and early shan area is the sedimentary hiatus between the Mississip- Paleo-Proterozoic age peaks to two poorly defined Protero- pian and Pennsylvanian (Figure 2). This hiatus has been zoic tectonovolcanic events between 1.8 and 2.0 Ga and 2.4 recognized in many profiles, separating a magmatic phase and 2.6 Ga that could be related to the early formation of in the Mississippian from an amagmatic and predominantly the Tarim block. marine sedimentary phase in the Pennsylvanian. The dura- Metamorphism of the Kurguvad basement block has not tion of this hiatus seems to increase from west to east, when been thoroughly documented. Peak amphibolite facies meta- comparing the similar setting within the Chinese North morphism was suggested by petrographic analysis and Pamir. Sedimentary Pennsylvanian units are only found in garnet-biotite (GARB) and garnet-biotite-muscovite-plagio- the Chinese North Pamir as allochthonous units [25]. Hiati clase (GBMP) thermobarometry of seven gneiss samples within sedimentary sections from Afghanistan, Tajikistan, from the Kurguvad block [52]. These samples yielded tem- and Kyrgyzstan [3, 32, 33, 53, 55] are temporally variable. peratures and pressures of 540–650°C and 5.5–7.6 kbar They show a pattern of diachronous marine sedimentary without staurolite and 600–650°C and 6.5–8.2 kbar with stau- environments changing from platform carbonate sedimenta- rolite, respectively. A monazite age of around 200 Ma reflects tion to clastic shelf sedimentation and a more or less Cimmerian metamorphism. We obtained one zircon U-Pb erosional, terrestrial phase in the upper Carboniferous to age of 200:8±1:8Ma from sample RT15-11, which reflects Permian [44]. the Cimmerian metamorphic imprint on the zircon fraction. The Kurguvad basement block must have also experienced 5.5. The Kurguvad Block: Detrital Signal and Metamorphism. pre-Carboniferous metamorphism, based on relative age The two Kurguvad paragneiss samples investigated using relations. The complex garnets (Appendix 5) suggest a multi- detrital zircon, RT13-148, and RT15-11 (Figure 6) have age phase metamorphic event. However, Konopelko et al. [110] peaks at 580 Ma, 722 Ma, and 943 Ma. These are similar to report concordant zircon U-Pb ages between 303 Ma and newly published ages from metamorphic units of the 406 Ma (Figure 6(c)) from the Garm basement block; these Kurguvad-Badakhshan complex (Figure 6 and Li et al. were interpreted to be metamorphic. This hints at a different [40]). Two metasedimentary garnet-staurolite schists sam- metamorphic history in Garm compared to the Kurguvad pled by Li et al. (DV-7-27-15-1 and LY-7-18-17-2 [40]) gave basement block.

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5.6. Metamorphism of the North Pamir Arc. The metamor- Turkestan ocean phic grade of the North Pamir arc has been estimated by pet- Garm rological thin section analysis, supported by XRD mineral Gissar Alai Tarim phase analysis. Excepting the Kurguvad block, no indication back arc of metamorphic imprint higher than greenschist facies on the Karakum Carboniferous volcanic rocks and granitoids was found. The vad gu ur Kurguvad block experienced amphibolite facies metamor- K ad phism during the Cimmerian orogeny [52]. Our data cannot ab yz clarify whether the greenschist facies metamorphism of the Fa Paleo-Tethys North Pamir is related to the late Carboniferous to Permian TSHT arc obduction history or to a later, Cimmerian overprint. erian blocks Cimm

6. Summary and Implications Figure 13: Paleogeographic constellation at the end of the Carboniferous: the North Pamir arc (bold hachures) is situated New and published geochemical and geochronological data between the Tarim cratonic block and the Karakum block, whose provide a detailed view of the along-strike variations of the existence has not yet been proven. South of Tarim, a branch of the North Pamir Carboniferous granitoid intrusions and their Proto-Tethys remained open until the Carboniferous. The East host rocks. Geochemical data from the tholeiitic and mafic Mazar arc volcanic rocks formed during its subduction. The to intermediate rocks, cropping out in the Chinese Oytag Tianshuihai terrane (TSHT) together with the South Kunlun terrane accreted in the Silurian to the southern margin of the and Qimgan valley and in the Kyrgyz Altyn Darya valley, Tarim croton (fine hachures). Cratonic blocks are shown in red document the formation of an island arc complex in the and noncratonic crust is shown in light blue (reconstruction after Upper Devonian to Bashkirian [3, 28]. The North Pamir Zhang et al. [24] and Konopelko et al. [110]). arc is chronologically and geochemically distinct from the volcanic arcs known from the West Kunlun. Compiled literature data from the early Paleozoic and ment block is quite similar to the Garm block in the Tian Triassic magmatic arc successions of the West Kunlun are Shan, suggesting a joint Precambrian geologic evolution. compared with new and published data from the Carbonifer- Starting with the emplacement of the Taergelake granite ous magmatic arc rocks of the North Pamir. The early Paleo- at around 360 Ma, large granitoids were emplaced within zoic succession in the West Kunlun records major intrusive the arc until 314 Ma. Granitoids in the Chinese North activity of a mature arc between 470 Ma and 450 Ma. The Pamir have a more primitive composition and are classified major Carboniferous intrusive activity in the North Pamir as island arc granites within an intraoceanic subduction lasted from 340 Ma to 320 Ma. The Triassic arc-magmatic zone [29]. The coeval tonalites and granodiorites that activity previously described from the West Kunlun and intruded volcanic sequences and the Kurguvad basement Karakul-Mazar lasted from 240 Ma to 200 Ma. As all three block in the Tajik North Pamir show more enriched REE magmatic environments are subduction related, their granit- patterns and are classified as continental volcanic arc gran- oid rocks show similarities in geochemistry: enrichment in ites. Our samples from the Tajik North Pamir arc fit well in LILE and depletion of HFSE such as Nb, P, and Ti stages 3–5 (tonalites to leucoplagiogranites) established by (Figure 12). However, the North Pamir arc Carboniferous Mamadjanov et al. [54] for Late Paleozoic intrusives of that granites show less enrichment of LILE and a stronger mantle region. To date, there are no age constraints for the stage 1 influence than the West Kunlun early Paleozoic and the and 2 intrusive rocks (i.e., gabbro and quartz diorites). We Triassic granites. Collision and exhumation of metamorphic interpret the geochemical along-strike variance as the tran- rocks of the West Kunlun started in the Silurian. A-type sition from intraoceanic island arc subduction in the Chi- magmatism occurring in the lower Devonian marks a post- nese Pamir to Cordilleran-type subduction in the Tajik orogenic extensional phase [14]. No magmatic rocks of that North Pamir. age have been recognized in the North Pamir. Granitoids in the East Mazar sliver of the Chinese West Despite the loose stratigraphic control on the age of the Kunlun show similar geochemical patterns as the Tajik gran- volcanic sequence in the North Pamir, we show that all itoids, suggesting another Cordilleran-type subduction zone analyzed samples and complementary literature data share to the east (Figure 13). However, there is also a connection common geochemical characteristics. As the mafic and inter- to continental material in the Chinese Pamir, documented mediate volcanic complexes show an arc signature, the name by an inherited zircon population with an age of 448 Ma from Kalai Khumb-Oytag basin (KOB [36]) might be used for the the Oytag granite [29] and the 417 Ma age population from subbasin of the Paleoasian ocean which hosted the arc. The the Triassic aplitic dike in Qimgan. Both age populations arc itself should better be named the North Pamir arc, follow- might be derived from the West Kunlun, where lower Devo- ing Bazhenov and Burtman [33]. As we have shown, the term nian to Ordovician granitoids related to the closure of the Kunlun arc [3] is inappropriate. The Kurguvad basement Proto-Tethys are common [101, 116]. We infer a Carbonifer- block with Ediacaran maximum depositional age and com- ous sediment flux from the Proto-Tethys suture zone in the plex metamorphic history was part of the volcanic arc, at West Kunlun toward today’s Chinese North Pamir and recy- least for part of its history. This sliver of a continental base- cling of that detritus in the accretionary wedge.

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The preserved length of the segment between Fakhar in Tajikistan. For support with sample preparation and labo- (Afghanistan) and Oytag (China) is around 500 km. How- ratory work, we thank Christine Fischer, Antje Musiol, Baian- ever, it is likely that the geometry of the subduction system suluu Terbishalieva, and Christina Günther. We also thank was modified by post-Carboniferous deformation. A partial Martin Timmermann, Roland Oberhänsli, Patrick O’Brian, obduction and erosion of the North Pamir arc in Pennsylva- Robert Trumbull, and Romain Bousquet for helpful discus- nian to Permian time can be inferred from disconformities sions on geochemical data. This project was funded by and facies variations found in the Tajik and Chinese North Deutsche Forschungs Gesellschaft e.V. (DFG) grant SO Pamir. Facies distributions indicate a longer phase of crustal 436/12-1 to Edward R. Sobel and DFG grant KL 495/27-1 to uplift and erosion in the Chinese North Pamir, where the Jonas Kley. Sampling in Tajikistan and Kyrgyzstan by Edward Upper Devonian to Bashkirian arc volcanic units are R. Sobel was funded by the National Geographic Society grant followed by a continental Guadalupian to Triassic sequence. GEFNE105-14. Sampling of the granites and the Kurguvad Whether the widespread presence of greenschist metamor- basement in the Tajik Punj and Obikhingou valleys was phism in the North Pamir arc is related to this arc obduction funded by DFG grant TH 1317-5 to Rasmus Thiede. event is not clear. The existence of pre-Mesozoic oceanic crust to the north—in present day coordinates—of the advancing Cim- Supplementary Materials merian continents in the region of the todays North Pamir Supplementary 1. Appendix 1: Detailed U-Pb Concordia is in sharp contrast to the situation in the West Kunlun. Plots for All Zircon Age Data Produced for This Study; New and existing data indicate the existence of a major Includes Zircon U-Pb Data of All Dated Granitoid Samples, oceanic domain in the North Pamir in late Paleozoic time Zircon U-Pb Age Spectra of the Two Samples from the and argue against a continuous Tarim-Tajik cratonic con- Kurguvad Paragneiss with Th/U Ratios, U-Pb Age Data, tinent. This also challenges the hypothesis that the West and Exemplary Imaging of Zircons from the Aplitic Dyke Kunlun and North Pamir formed a continuous linear belt Sampled in the Qimgan Basin. Appendix 2: Thin Section prior to the India-Asia collision; this removes a key paleo- Photos Showing Mineralogy and Textures of Volcanic Rock geographic constraint on the magnitude of Cenozoic Samples from the North Pamir Arc. Appendix 3: Thin Sec- indentation of the Pamir. A Carboniferous compressive tion Photos Showing Detailed Mineralogy and Textures of phase partly closed the oceanic basin along an intraoceanic Plutonic Rock Samples from the North Pamir Arc. Appendix subduction zone that laterally continued into a Cordilleran- 4: Thin Section Photos Showing Mineralogy and Textures of style subduction zone. In the east, closure and exhumation Metamorphic Rock Samples from the Kurguvad Block. resulted in continental conditions, as shown by the Permo- Appendix 5: SEM-Backscattered Electron Composition Triassic volcanosedimentary sequence found in the Qimgan (BEC) Images and Semiquantitative EDX Profiles of Garnets valley. The lack of high-grade metamorphic units all along from the Kurguvad Basement Block. Appendix 6: Detailed the North Pamir arc and ongoing marine sedimentation in Map and Structural Data from an Outcrop of the Shala Tala the western parts of the basin, however, hint at a soft colli- Nappe Directly at the Recent Mountain Front near the sion or slowdown of Carboniferous compressive tectonics. Village of Bostantielieke. That left behind weaker crust to the west of Tarim compared to the well-amalgamated early Paleozoic terranes of the West Supplementary 2. Appendix 7: Txt Files that Contain Calcite Kunlun. The West Kunlun incorporated the Tarim base- (“Appendix 7 Calcite.txt”) and Zircon (“Appendix 7 Zir- ment, in the North Kunlun domain [12]. This E-W differ- con.txt”) U-Pb Data Produced for this Study. Note that ence in rheology facilitated the advance of the Central Isotope Errors Are Given as 2σ for Zircon Data and 1σ for Pamir further to the north compared to its eastward lateral Calcite Data. equivalents, which may have caused a bending of the Cim- Supplementary 3. Appendix 8: A Txt File that Contains all merian orogen. Geochemistry Data of Plutonic and Volcanic Rock Samples Investigated for This Study. Data Availability Supplementary 4. Appendix 9: A Txt File Containing Com- New geochronological and geochemical data used for this piled and Newly Presented Radiometric Ages Used for This study can be found in Appendixes 7 and 8. Sources of Study along with Location Name and Coordinates of the compiled data are cited in the text. Samples. Supplementary 5. Appendix 10: A Txt File Containing Conflicts of Interest Modal Content of Major Minerals (in Percent) of Thin Sec- tions from Samples Taken from Plutonic Rocks Presented in fl The authors declare that they have no con ict of interest. This Study.

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