Yttrium-zoning in garnet and stability of allanite in metapelites from the Main Central Thrust Zone and adjacent higher Himalayan crystallines along the Alaknanda Valley, NW Himalaya

Thakur, S. S.; Madhavan, K.P.; Patel, Suresh C.; Rao, D. R. K.; Singh, Alka; Pandey, Shiv Jyoti; Nandini, P.

doi:10.1016/j.lithos.2018.09.002

Cited by 14 publications

(7 citation statements)

References 78 publications

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“…The baric conditions suggest a maximum erosional exhumation rate of ∼7 mm/year (3.7 kbar/km baric gradient, 20–22 km depths over 3 Myr). Samples that experienced these higher exhumation rates may be present in NW India, as evidenced by P‐T paths and conditions obtained from LHF rocks in the adjacent Alaknanda and Dhauli Ganga valleys that suggest exhumation from greater depths (6.3–7.5 kbar, Iaccarino et al., 2020; S. S. Thakur et al., 2015, 2018).…”

Section: Discussionmentioning

confidence: 97%

“…Samples that experienced these higher exhumation rates may be present in NW India, as evidenced by P-T paths and conditions obtained from LHF rocks in the adjacent Alaknanda and Dhauli Ganga valleys that suggest exhumation from greater depths (6.3-7.5 kbar, Iaccarino et al, 2020;S. S. Thakur et al, 2015S. S. Thakur et al, , 2018.…”

Section: Modeling Lhf P-t Paths and Monazite Agesmentioning

confidence: 97%

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High‐Resolution P‐T‐Time Paths Across Himalayan Faults Exposed Along the Bhagirathi Transect NW India: Implications for the Construction of the Himalayan Orogen and Ongoing Deformation

Catlos

Perez

Lovera

et al. 2020

Geochem Geophys Geosyst

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Pressure-temperature (P-T) conditions and high-resolution paths from 11 garnet-bearing rocks collected across Himalayan fault systems exposed along the Bhagirathi River (Uttarakhand, NW India) reveal the tectonic conditions responsible for their growth. A garnet from the Tethyan metasedimentary unit has a 50.3 ± 0.6 Ma (Th-Pb, ±1σ) monazite inclusion, suggesting that ductile midcrustal metamorphism occurred synchronously or soon after (<10 Myr) India-Asia collision, depending on timing. High-resolution garnet P-T paths from the same rock show ∼1 kbar fluctuations in P as T increases over a ∼20°C interval, consistent with a period of erosion. We report garnets from the Main Central Thrust (MCT) hanging wall that have Eocene to Miocene monazite ages, and one garnet yields paths consistent with motion along the Main Himalayan Thrust (MHT) décollement. Most high-resolution MCT footwall P-T paths fluctuate in P (±1 kbar) as T increases, consistent with imbrication and paths from equivalent structural assemblages in central Nepal. Like those rocks, MCT footwall (Lesser Himalayan Formation, LHF) monazite ages are Early Miocene (9.3 ± 0.6 Ma) to Pliocene (3.0 ± 0.2 Ma). The results demonstrate the consistency in timing and conditions across the MCT at locations ∼650 km apart. If the present-day Himalayan tectonic framework has not significantly changed since the Pliocene, the LHF duplex can be considered when attributing seismic events to particular faults. The MHT is undisputedly the significant factor in accommodating Himalayan seismic activity, but MCT footwall faults may explain some shallower hypocenters, without the need for unusual MHT geometries. Plain Language Summary The Mw 6.8 Uttarkashi earthquake occurred in the NW Indian Himalayas in 1991 and was located near a fault system termed the Main Central Thrust (MCT). Like the April 25, 2015, Mw7.8 Gorkha (Nepal) earthquake, the reported depth and fault system that triggered the earthquake is unclear. Despite being studied for decades, the geometry of the deeper portions of the Himalayan range is debated. New approaches in thermodynamic modeling allow us to obtain the highest resolution pressure-temperature (P-T) paths possible from garnets collected across Himalayan fault systems near the epicenters of the Uttarkashi earthquake and its aftershocks. We also date radioactive monazite in garnet-bearing rocks beneath the MCT, which crystallized only 1-3 million years ago. Monazite in garnet collected further north are older, consistent with timing India and Asia collision ∼50 million years ago. The MCT appears to be a broad shear zone with packages of rocks moving like a deck of cards at different times. If the present-day Himalayan framework has not significantly changed since the recent geological past, fault systems beneath the MCT may explain some of the shallower hypocenters reported for both the Gorkha and Uttarkashi earthquake and their aftershocks.

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Section: Discussionmentioning

confidence: 97%

Section: Modeling Lhf P-t Paths and Monazite Agesmentioning

confidence: 97%

High‐Resolution P‐T‐Time Paths Across Himalayan Faults Exposed Along the Bhagirathi Transect NW India: Implications for the Construction of the Himalayan Orogen and Ongoing Deformation

Catlos

Perez

Lovera

et al. 2020

Geochem Geophys Geosyst

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“…In the lower parts, the Munsiari Group (MCT zone representing base of the HHC) consists of low to medium grade highly mylonitized package of garnet mica schist/ gneiss, quartzite, amphibolite and biotiterich phyllonite, augen mylonite and gneiss. Garnet porphyroblasts from the garnet grade MCTZ metapelites commonly show chemical zoning with yttrium -rich core and Y-poor rim (Thakur et al, 2018).…”

Section: Alaknanda-dhauli Ganga Valleysmentioning

confidence: 99%

Tectonics of the Western, Sikkim and Arunachal Himalaya

Jain¹,

Thakur²,

Joshi³

et al. 2020

PINSA

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During the period 2016-2020, the Indian scientists undertook extensive research in the Himalayan Orogen, which incorporated extensive field mapping, structural analysis, geochemistry, metamorphic and igneous petrology, stratigraphy and palaeontology, Ar/Ar and U-Pb geochronology, besides low-temperature thermochronology. These activities were almost spread throughout the belt from western sector through Garhwal-Kumaon, Sikkim, Bhutan and Arunachal Pradesh. In addition, research was also undertaken using magnetotelluric methods for large-scale tectonics, seismology, paleoseismology and other disciplines, which are covered in other contributions. National laboratories have now started generating highresolution U-Pb dates, which have been providing impetus to model Himalayan tectonics, besides modelling its Paleoproterozoic and Neoproterozoic configuration.

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“…DOI: https://doi.org/10.2138/am-2021-7692. http://www.minsocam.org/ tends to concentrate these elements relative to associated rock-forming silicates (Kasowski and Hogarth 1968, Enami et al 1995, Lanzirotti 1995, Bea 1996, Pyle and Spear 1999, Vaggelli et al 2003, Katerinopoulou et al 2009, Hönig et al 2014, Gulbin 2016, Thakur et al 2018). In the composition of this garnet Y and HREE prevail, which in general is characteristic for metamorphic and magmatic garnets.…”

Section: Introductionmentioning

confidence: 99%

Priscillagrewite-(Y), (Ca2Y)Zr2Al3O12: A new garnet of the bitikleite group from the Daba-Siwaqa area, the Hatrurim Complex, Jordan

Galuskina

Galuskin

Vapnik

et al. 2021

American Mineralogist

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Priscillagrewite-(Y), ideally (Ca 2 Y)Zr 2 Al 3 O 12 (Ia-3d, a = 12.50 Å, V = 1953.13 Å 3 , Z = 8), a new member of the garnet supergroup and bitikleite group, was discovered in a fluorapatite layer (metaphosphorite) hosted by varicolored spurrite marble in the Daba-Siwaqa area of the Transjordan plateau south of Amman, central Jordan. The Daba-Siwaqa area is the largest field of the Hatrurim Complex pyrometamorphic rocks distributed along the rift of the Dead Sea. Priscillagrewite-(Y) as well as other accessory minerals such as members of the brownmillerite-srebrodolskite series, fluormayenite, lakargiite, baghdadite, hematite, This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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Yttrium-zoning in garnet and stability of allanite in metapelites from the Main Central Thrust Zone and adjacent higher Himalayan crystallines along the Alaknanda Valley, NW Himalaya

Cited by 14 publications

References 78 publications

High‐Resolution P‐T‐Time Paths Across Himalayan Faults Exposed Along the Bhagirathi Transect NW India: Implications for the Construction of the Himalayan Orogen and Ongoing Deformation

High‐Resolution P‐T‐Time Paths Across Himalayan Faults Exposed Along the Bhagirathi Transect NW India: Implications for the Construction of the Himalayan Orogen and Ongoing Deformation

Tectonics of the Western, Sikkim and Arunachal Himalaya

Priscillagrewite-(Y), (Ca2Y)Zr2Al3O12: A new garnet of the bitikleite group from the Daba-Siwaqa area, the Hatrurim Complex, Jordan

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