Rift‐related origin of the <scp>P</scp>aleoproterozoic <scp>K</scp>uncha <scp>F</scp>ormation, and cooling history of the <scp>K</scp>uncha nappe and <scp>T</scp>aplejung granites, eastern <scp>N</scp>epal <scp>L</scp>esser <scp>H</scp>imalaya: a multichronological approach

Sakai, Harutaka; Iwano, Hideki; Danhara, Tohru; Takigami, Yutaka; Man, Santa; Upreti, B. N.; Hirata, Takafumi

doi:10.1111/iar.12021

Cited by 50 publications

(94 citation statements)

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“…; Sakai et al . ), but they resemble those from the Higher Himalayan Crystallines and overlying Tibetan Tethys sediments, as pointed out by DeCelles et al . ().…”

Section: Discussionsupporting

confidence: 67%

“…These discordant ages are also apparent in other MCT zone samples (Sakai et al . ), suggesting younger thermal events.…”

Section: Results Of Multichronological Studiesmentioning

confidence: 99%

“…The Kuncha Formation represents the lower Kali Gandaki Group, and it is intruded by 1.9–1.8 Ga granites (Sakai et al . ). The lower part of the Paleoproterozoic low‐grade metasediments was thrust over the younger Lesser Himalayan sediments to form a nappe that is variously called the Chail nappe (Frank & Fuchs ), the Kuncha nappe (Sharma et al .…”

Section: Introductionmentioning

confidence: 99%

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Emplacement of hot Lesser Himalayan nappes from 15 to 10 Ma in the Jumla–Surkhet region, western Nepal, and their thermal imprint on the underlying Early Miocene fluvial Dumri Formation

Sakai

Iwano²,

Danhara³

et al. 2013

Island Arc

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A multichronological study of the weakly metamorphosed Early Miocene fluvial Dumri Formation and the overlying Kuncha and Lesser Himalayan Crystalline nappes has helped to clarify the timing and heat source of the metamorphism, as well as the history of emplacement and cooling of the nappes. U–Pb ages of detrital zircons from the Dumri Formation show peaks at ca 1 Ga and 500–600 Ma, and fission‐track dating indicates a thermal imprint on the formation at 11–10 Ma. In the Naudanda Quartzite, overlying the Kuncha Formation, reset fission‐track detrital zircon ages are 9.5 Ma, but the U–Pb ages are older than 1.7 Ga. The differences in the U–Pb ages for detrital zircons from the Dumri and Kuncha Formations indicate that the Kuncha nappe was never exposed at the surface during the Early Miocene when the Dumri Formation was deposited. Two‐mica garnet schists of the Main Central Thrust (MCT) zone have fission‐track detrital zircon ages of 7.8 Ma and 40Ar–39Ar muscovite ages of 19 Ma, though the zircons have U–Pb ages older than 600 Ma. Our interpretation is that the heat for the Dumri Formation metamorphism came from the overlying nappes. The timing of the thermal imprint on the Dumri Formation indicates that the metamorphic nappe reached its present position before ca 10 Ma. The Parajul Khola granite in the frontal zone of the Kuncha nappe yields U–Pb zircon ages of 1.89 Ga, and it underwent an Early Miocene thermal event, cooling below 240°C at 14.7 Ma and below 100°C at 10.3 Ma. These thermochronological data suggest that the frontal part of the Kuncha nappe was exposed at the surface around 15–14 Ma and cooled immediately, but inner parts of the nappe were still hot during its emplacement.

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“…; Sakai et al . ), but they resemble those from the Higher Himalayan Crystallines and overlying Tibetan Tethys sediments, as pointed out by DeCelles et al . ().…”

Section: Discussionsupporting

confidence: 67%

“…These discordant ages are also apparent in other MCT zone samples (Sakai et al . ), suggesting younger thermal events.…”

Section: Results Of Multichronological Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Emplacement of hot Lesser Himalayan nappes from 15 to 10 Ma in the Jumla–Surkhet region, western Nepal, and their thermal imprint on the underlying Early Miocene fluvial Dumri Formation

Sakai

Iwano²,

Danhara³

et al. 2013

Island Arc

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“…2) is underlain by rocks of the Himalayan metamorphic core and Lesser Himalayan Sequence (Shrestha et al, 1984;Schelling, 1992;Goscombe and Hand, 2000;Goscombe et al, 2006). The Lesser Himalayan Sequence is exposed in the Tamor window and consists of Chl + Bt + Ms (abbreviations throughout are after Whitney and Evans, 2010) phyllite and quartzite (Shrestha et al, 1984;Schelling, 1992), which have been intruded by Paleoproterozoic granite (now orthogneiss; Upreti et al, 2003;Sakai et al, 2013). The Himalayan metamorphic core, which has been thrust over the Lesser Himalayan Sequence along the Main Central thrust, is a dominantly metasedimentary assemblage of paragneiss and quartzite with subordinate calc-silicate, metabasite, and orthogneiss.…”

Section: Kanchenjunga Regionmentioning

confidence: 99%

“…First, the mapped trace marks the base of closely spaced, inverted, metamorphic isograds that overlie very lowmetamorphic-grade rock. Second, the mapped trace is located between rocks above, which record Himalayan-related metamorphism, and rocks below, which were relatively unaffected; a mylonitic orthogneiss unit, just up structural section from the garnet-in isograd, records Cenozoic cooling ages, whereas Paleoproterozoic granites, near the center of the Tamor window, record Paleoproterozoic cooling ages (Sakai et al, 2013).…”

Section: Himalayan Metamorphic Corementioning

confidence: 99%

Lateral extrusion, underplating, and out-of-sequence thrusting within the Himalayan metamorphic core, Kanchenjunga, Nepal

et al. 2015

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Integrated pseudosection modeling and monazite petrochronology of paragneiss from the Kanchenjunga region of northeastern Nepal reveal the presence of cryptic tectonometamorphic discontinuities within the Himalayan metamorphic core. These new data outline a series of thrust-sense structures that juxtapose rocks that generally record a protracted history of early Eocene to latest Oligocene-early Miocene (ca. 41-23 Ma) prograde metamorphism and lateral extrusion against others that typically record short prograde (between 2 and 7 m.y.) and retrograde (between 3 and 6 m.y.) histories variably spanning the middle Oligocene to the middle Miocene (ca. 31-12 Ma). Retrograde metamorphism in the hanging wall of the thrust faults is typically coeval with prograde metamorphism in the footwall, indicating that overthrusting/underthrusting accommodated crustal shortening and drove metamorphic processes. The structures and juxtaposed panels were cut by early Miocene (ca. 20-18 Ma) out-of-sequence thrusting coincident with the previously mapped High Himal thrust. The resulting kinematic model for the evolution of the Himalayan metamorphic core in the Kanchenjunga area demonstrates that the Himalayan metamorphic core was dominated by underplating from at least the Oligocene through to present, and that the internal structure of the exhumed metamorphic core is significantly more complex than has been documented previously.

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Reconstructing the Greater Indian margin: A balanced cross section in central Nepal focusing on the Lesser Himalayan duplex

Robinson

Martin

2014

Tectonics

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Across much of the Himalaya, rocks in the Lesser Himalayan duplex are covered by roof thrusts of other Paleoproterozoic Lesser Himalayan rocks or Greater Himalayan rocks. However, in central Nepal, between the Main Central thrust and the Main Boundary thrust, Lesser Himalayan rocks are exposed in structurally complex relationships within the Lesser Himalayan duplex. We present two balanced cross sections with different stratigraphy involved in the duplex, one with the basal Kuncha Formation and one without this unit, to test stratigraphic assumptions. Both cross sections have roof thrust sheets consisting of the Main Central thrust, Ramgarh-Munsiari thrust, and Trishuli thrust folded over the hinterland dipping Lesser Himalayan duplex dissected by late faults. Cross section 1 has a shortening estimate from the Main Central thrust to the Main Boundary thrust, including motion on the Main Central thrust, of 359 km or 78%. Cross section 2 has a shortening estimate of 349 km or 76% over the same region. Because the amount and percentage of shortening are not significantly different between the two cross sections, the different stratigraphic assumptions did not change the shortening results. This similarity suggests that many of the choices made when constructing a cross section may be less important than researchers previously thought.

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Rift‐related origin of the Paleoproterozoic Kuncha Formation, and cooling history of the Kuncha nappe and Taplejung granites, eastern Nepal Lesser Himalaya: a multichronological approach

Cited by 50 publications

References 56 publications

Emplacement of hot Lesser Himalayan nappes from 15 to 10 Ma in the Jumla–Surkhet region, western Nepal, and their thermal imprint on the underlying Early Miocene fluvial Dumri Formation

Emplacement of hot Lesser Himalayan nappes from 15 to 10 Ma in the Jumla–Surkhet region, western Nepal, and their thermal imprint on the underlying Early Miocene fluvial Dumri Formation

Lateral extrusion, underplating, and out-of-sequence thrusting within the Himalayan metamorphic core, Kanchenjunga, Nepal

Reconstructing the Greater Indian margin: A balanced cross section in central Nepal focusing on the Lesser Himalayan duplex

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