High-pressure Tethyan Himalaya rocks along the India-Asia suture zone in southern Tibet

Laskowski, Andrew K.; Kapp, Paul; Vervoort, Jeff D.; Ding, Lin

doi:10.1130/l544.1

Cited by 39 publications

(42 citation statements)

References 45 publications

(58 reference statements)

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“…The geology of the Lazi region (this study), and possibly the Yarlung suture zone as a whole (e.g., Zhang et al, 2011;Laskowski et al, 2017), is characterized by alternating episodes of extension and contraction. The timing of tectonic mode switches appears to be consistent with changes in the behavior of the subducting Great Indian slab, characterized by contraction during episodes of shallow underthrusting, extension during rollback, and duplexing during slab breakoff and return to northward underthrusting (e.g., DeCelles et al, 2011;Laskowski et al, 2016Laskowski et al, , 2017Webb et al, 2017). The geology of the Yarlung suture zone in the Lazi region integrates well with these "subduction control" models.…”

Section: Lithospheric-scale Tectonics and The Gangdese Culmination Modelsupporting

confidence: 53%

Gangdese culmination model: Oligocene–Miocene duplexing along the India-Asia suture zone, Lazi region, southern Tibet

2018

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The mechanisms for crustal thickening and exhumation along the Yarlung (India-Asia) suture in southern Tibet are under debate, because the magnitudes, relative timing, and interaction between the two dominant structures-the Great Counter thrust and Gangdese thrust-are largely unconstrained. In this study, we present new geologic mapping results from the Yarlung suture zone in the Lazi region, located ~350 km west of the city of Lhasa, along with new igneous (5 samples) and detrital (5 samples, 474 ages) U-Pb geochronology data to constrain the crystallization ages of Jurassic-Paleocene Gangdese arc rocks, the provenance of Tethyan Himalayan and Oligocene-Miocene Kailas Formation strata, and the minimum age (ca. 10 Ma) of the Great Counter thrust system. We supplement these data with a compilation of 124 previously published thermochronologic ages from Gangdese batholith, Kailas Formation, and Liuqu Formation rocks, revealing a dominance of 23-15 Ma cooling contemporaneous with slip across the Great Counter thrust system and other potentially linked structures. These data are systematically younger than 98 additional compiled thermo chronologic ages from the northern Lhasa terrane, recording mainly Eocene cooling. Structural and thermochronologic data were combined with regional geological constraints, including International Deep Profiling of Tibet and the Himalaya ( INDEPTH) seismic reflection data, to develop a new structural model for the Oligocene-Miocene evolution of the Tethyan Himalaya, Yarlung suture zone, and southern Lhasa terrane. We propose that a hinterland-dipping duplex beneath the Gangdese mountains, of which the Gangdese thrust is a component, is kinematically linked with a foreland-dipping passive roof duplex along the Yarlung suture zone, the Great Counter thrust system. The spatial and temporal convergence between the proposed duplex structures along the Yarlung suture zone and the South Tibetan detachment system indicate that they may be kinematically linked, though this relationship is not directly addressed in this study. Our interpretation, referred to as the Gangdese culmination model, explains why the Gangdese thrust system is only locally exposed (at relatively deeper structural levels) and provides a structural explanation for early Miocene crustal thickening along the Yarlung suture zone, relief generation along the modern Gangdese Mountains, early Miocene Yarlung River establishment, and creation of the modern internal drainage boundary along the southern Tibetan Plateau. The progression of deformation along the suture zone is consistent with tectonic models that implicate subduction dynamics as the dominant control on crustal deformation.

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Section: Lithospheric-scale Tectonics and The Gangdese Culmination Modelsupporting

confidence: 53%

Gangdese culmination model: Oligocene–Miocene duplexing along the India-Asia suture zone, Lazi region, southern Tibet

2018

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“…In the north Himalayan gneiss domes, Cambrian–Ordovician gneiss in the Tso Morari dome also yields Eocene (ca. 53 Ma) white mica (Schlup et al, ), and Tethyan Himalayan sequence metasedimentary rocks in the Lopu Kangri Range yield white mica 40 Ar/ 39 Ar ages of circa 39 to 34 Ma (Laskowski et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Possible sources for Eocene white mica also include the Gangdese batholith and Eocene north Himalayan granitoids (Aikman et al, 2008), but these potential sources probably can be ruled out because of the absence of Eocene zircon U-Pb ages in the Dumri Formation. Thus, the most likely source of Eocene white mica is the Tethyan Himalayan sequence, which has produced scattered Eocene mica cooling ages and abundant evidence for pre-44 Ma deformation and 10.1029/2018TC005390 Tectonics metamorphism (Laskowski et al, 2016;Ratschbacher et al, 1994;Schlup et al, 2003;Wiesmayr & Grasemann, 2002). In the northeastern part of the Tethyan Himalaya, penetratively deformed Triassic rocks in the hanging wall of a major thrust fault were intruded by undeformed~44 Ma granite, which requires that deformation and heating in this part of the thrust belt must predate 44 Ma (Aikman et al, 2008).…”

Section: White Mica 40 Ar/ 39 Ar Provenance Signaturesmentioning

confidence: 99%

Tracking the Growth of the Himalayan Fold‐and‐Thrust Belt From Lower Miocene Foreland Basin Strata: Dumri Formation, Western Nepal

et al. 2019

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New data from the lower Miocene Dumri Formation of western Nepal document exhumation of the Himalayan fold‐thrust belt and provenance of the Neogene foreland basin system. We employ U‐Pb zircon, Th‐Pb monazite, 40Ar/39Ar white mica, and zircon fission track chronometers to detrital minerals to constrain provenance, timing, and rate of exhumation of Himalayan source regions. Clusters of Proterozoic–early Paleozoic (900–400 Ma) Th‐Pb monazite and 40Ar/39Ar white mica detrital ages provide evidence for erosion of a Greater Himalayan sequence protolith unaffected by high‐grade Eohimalayan metamorphism. A small population of ~40 Ma cooling ages in detrital white mica grains shows exhumation of low‐grade metamorphic Tethyan Himalayan sequence through the ~350 °C closure temperature along the Tethyan Frontal thrust (proto‐South Tibetan detachment) during the late Eocene. Dumri Formation detritus shows a ~12 Myr time difference between cooling of its source rocks through the ~350 and ~240 °C closure temperatures as recorded by ~40–38 Ma youngest peak cooling ages in 40Ar/39Ar detrital white mica and ~28–24 Ma youngest populations in detrital zircon fission track. Exhumation between circa 40 and 28 Ma is consistent with slip and exhumation along the Main Central Thrust. Combined with similar data from northwestern India, our study suggests west‐to‐east spatially variable exhumation rates along strike of the Main Central Thrust. Our data also show an increase in exhumation during middle Miocene–Pliocene time, which is consistent with growth of the Lesser Himalaya duplex.

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“…Primary Yarlung suture structures are obscured by the south dipping, north directed Great Counter Thrust system (GCT) [ Heim and Gansser , ], juxtaposing Tethyan Himalaya sequence rocks against suture zone mélange and ophiolite, mélange and ophiolite against fore‐arc strata, and fore‐arc strata against the Kailas Formation (Figures and ). The Great Counter Thrust system comprises one or more moderately to steeply south dipping reverse faults along strike in southern Tibet [e.g., Zhang et al ., ; Laskowski et al ., ], corresponding to the presence or absence of suture zone rock units between the Kailas Formation and the Tethyan Himalaya sequence. The Great Counter Thrust system was active during the early to mid‐Miocene based on crosscutting relationships, and its slip magnitude is poorly constrained because of a lack of hanging wall cutoffs [ Ratschbacher et al ., ; Quidelleur et al ., ; Yin et al ., ].…”

Section: Regional Geologic Backgroundmentioning

confidence: 99%

“…The Dajiling fault is a >2 km thick zone of protomylonite and mylonite folded across the Niuku Anticline (Figures and c) and exposed in the central and southern Lopu Range [ Laskowski et al ., ]. On the north limb of the anticline, it strikes E‐W, dips ~60°N, and juxtaposes low‐grade sedimentary‐matrix mélange in the hanging wall against footwall meta‐Tethyan calc‐paragneiss and mesoscale to macroscale quartzite and quartz‐rich paragneiss lenses (Figure c).…”

Section: Structural Geologymentioning

confidence: 99%

Tectonic evolution of the Yarlung suture zone, Lopu Range region, southern Tibet

et al. 2017

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The Lopu Range, located ~600 km west of Lhasa, exposes a continental high‐pressure metamorphic complex beneath India‐Asia (Yarlung) suture zone assemblages. Geologic mapping, 14 detrital U‐Pb zircon (n = 1895 ages), 11 igneous U‐Pb zircon, and nine zircon (U‐Th)/He samples reveal the structure, age, provenance, and time‐temperature histories of Lopu Range rocks. A hornblende‐plagioclase‐epidote paragneiss block in ophiolitic mélange, deposited during Middle Jurassic time, records Late Jurassic or Early Cretaceous subduction initiation followed by Early Cretaceous fore‐arc extension. A depositional contact between fore‐arc strata (maximum depositional age 97 ± 1 Ma) and ophiolitic mélange indicates that the ophiolites were in a suprasubduction zone position prior to Late Cretaceous time. Five Gangdese arc granitoids that intrude subduction‐accretion mélange yield U‐Pb ages between 49 and 37 Ma, recording Eocene southward trench migration after collision initiation. The south dipping Great Counter Thrust system cuts older suture zone structures, placing fore‐arc strata on the Kailas Formation, and sedimentary‐matrix mélange on fore‐arc strata during early Miocene time. The north‐south, range‐bounding Lopukangri and Rujiao faults comprise a horst that cuts the Great Counter Thrust system, recording the early Miocene (~16 Ma) transition from north‐south contraction to orogen‐parallel (E‐W) extension. Five early Miocene (17–15 Ma) U‐Pb ages from leucogranite dikes and plutons record crustal melting during extension onset. Seven zircon (U‐Th)/He ages from the horst block record 12–6 Ma tectonic exhumation. Jurassic—Eocene Yarlung suture zone tectonics, characterized by alternating episodes of contraction and extension, can be explained by cycles of slab rollback, breakoff, and shallow underthrusting—suggesting that subduction dynamics controlled deformation.

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High-pressure Tethyan Himalaya rocks along the India-Asia suture zone in southern Tibet

Cited by 39 publications

References 45 publications

Gangdese culmination model: Oligocene–Miocene duplexing along the India-Asia suture zone, Lazi region, southern Tibet

Gangdese culmination model: Oligocene–Miocene duplexing along the India-Asia suture zone, Lazi region, southern Tibet

Tracking the Growth of the Himalayan Fold‐and‐Thrust Belt From Lower Miocene Foreland Basin Strata: Dumri Formation, Western Nepal

Tectonic evolution of the Yarlung suture zone, Lopu Range region, southern Tibet

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