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Journal articles on the topic 'Himalaya leucogranite'

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Published: 4 June 2021

Last updated: 19 February 2022

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1

SEARLE, M. P., S. R. NOBLE, A. J. HURFORD, and D. C. REX. "Age of crustal melting, emplacement and exhumation history of the Shivling leucogranite, Garhwal Himalaya." Geological Magazine 136, no. 5 (September 1999): 513–25. http://dx.doi.org/10.1017/s0016756899002885.

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We report a U–Pb monazite age of 23.0±0.2 Ma for the Shivling leucogranite, a tourmaline+muscovite±biotite leucogranite at the top of the High Himalayan slab in the Garhwal Himalaya, north India. The Shivling–Bhagirathi leucogranite is a viscous near-minimum melt, emplaced as a foliation parallel laccolith via a dyke network not far from its source region. Prograde heating occurred soon after the India–Asia collision at c. 50 Ma up to melting at 23 Ma and high temperatures (>550 °C) were maintained for at least 15 Ma after garnet growth. The leucogranite was emplaced at mid-crustal depths along the footwall of the Jhala fault, a large-scale low-angle normal fault, part of the South Tibetan Detachment system, above kyanite and sillimanite grade gneisses. The geometry of the leucogranite laccolith shows biaxial extension and boudinage both perpendicular (north-northeast–south-southwest) and parallel to the strike (west-northwest–east-southeast) of the mountain range. Unroofing occurred by underthrusting beneath the High Himalayan slab along the Main Central Thrust zone, progressively ‘jacking up’ the leucogranites, removal of material above by low-angle normal faulting, and erosion. Very rapid cooling at rates of 200–350 °C/Ma between 23–21 Ma immediately followed crystallization, as tectonic unroofing and erosion removed 24–28 km of overburden during this time. K–Ar muscovite ages are 22±1.0 Ma and fission track ages of zircons from >5000 m on the North Ridge of Shivling are 14.2±2.1 and 8.8±1.2 Ma and apatites are 3.5±0.79 and 2.61±0.23 Ma. Slow steady state cooling at rates of 20–30 °C/Ma from 20–1 Ma shows that maximum erosion rates and unroofing of the leucogranite occurred during the early Miocene. This timing coincides with initiation of low-angle, north-dipping normal faulting along the South Tibetan Detachment system.

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2

Bikramaditya Singh, R. K., and A. Krishnakanta Singh. "Microstructural and geochemical studies of Higher Himalayan Leucogranite: implications for geodynamic evolution of Tertiary Leucogranite in the Eastern Himalaya." Geological Journal 49, no. 1 (January 22, 2013): 28–51. http://dx.doi.org/10.1002/gj.2480.

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3

Xie, Jiajia, Huaning Qiu, Xiujuan Bai, Wanfeng Zhang, Qiang Wang, and Xiaoping Xia. "Geochronological and geochemical constraints on the Cuonadong leucogranite, eastern Himalaya." Acta Geochimica 37, no. 3 (April 23, 2018): 347–59. http://dx.doi.org/10.1007/s11631-018-0273-8.

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4

INGER, S., and N. HARRIS. "Geochemical Constraints on Leucogranite Magmatism in the Langtang Valley, Nepal Himalaya." Journal of Petrology 34, no. 2 (April 1, 1993): 345–68. http://dx.doi.org/10.1093/petrology/34.2.345.

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5

Searle, M. P., R. P. Metcalfe, A. J. Rex, and M. J. Norry. "Field relations, petrogenesis and emplacement of the Bhagirathi leucogranite, Garhwal Himalaya." Geological Society, London, Special Publications 74, no. 1 (1993): 429–44. http://dx.doi.org/10.1144/gsl.sp.1993.074.01.29.

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6

Sachan, H. K., M. J. Kohn, A. Saxena, and S. L. Corrie. "The Malari leucogranite, Garhwal Himalaya, northern India: Chemistry, age, and tectonic implications." Geological Society of America Bulletin 122, no. 11-12 (August 11, 2010): 1865–76. http://dx.doi.org/10.1130/b30153.1.

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7

Villa, Igor M. "Geochronology and excess Ar geochemistry of the Lhotse Nup leucogranite, Nepal Himalaya." Journal of Volcanology and Geothermal Research 44, no. 1-2 (December 1990): 89–103. http://dx.doi.org/10.1016/0377-0273(90)90013-6.

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8

Crawford, Mark B., and Brian F. Windley. "Leucogranites of the Himalaya/Karakoram: implications for magmatic evolution within collisional belts and the study of collision-related leucogranite petrogenesis." Journal of Volcanology and Geothermal Research 44, no. 1-2 (December 1990): 1–19. http://dx.doi.org/10.1016/0377-0273(90)90008-4.

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9

Bikramaditya Singh, R. K. "Origin and emplacement of the Higher Himalayan Leucogranite in the eastern Himalaya: Constraints from geochemistry and mineral chemistry." Journal of the Geological Society of India 81, no. 6 (June 2013): 791–803. http://dx.doi.org/10.1007/s12594-013-0104-9.

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10

Treloar, Peter J., Richard M. Palin, and Michael P. Searle. "Towards resolving the metamorphic enigma of the Indian Plate in the NW Himalaya of Pakistan." Geological Society, London, Special Publications 483, no. 1 (2019): 255–79. http://dx.doi.org/10.1144/sp483-2019-22.

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AbstractThe Pakistan part of the Himalaya has major differences in tectonic evolution compared with the main Himalayan range to the east of the Nanga Parbat syntaxis. There is no equivalent of the Tethyan Himalaya sedimentary sequence south of the Indus–Tsangpo suture zone, no equivalent of the Main Central Thrust, and no Miocene metamorphism and leucogranite emplacement. The Kohistan Arc was thrust southward onto the leading edge of continental India. All rocks exposed to the south of the arc in the footwall of the Main Mantle Thrust preserve metamorphic histories. However, these do not all record Cenozoic metamorphism. Basement rocks record Paleo-Proterozoic metamorphism with no Cenozoic heating; Neo-Proterozoic through Cambrian sediments record Ordovician ages for peak kyanite and sillimanite grade metamorphism, although Ar–Ar data indicate a Cenozoic thermal imprint which did not reset the peak metamorphic assemblages. The only rocks that clearly record Cenozoic metamorphism are Upper Paleozoic through Mesozoic cover sediments. Thermobarometric data suggest burial of these rocks along a clockwise pressure–temperature path to pressure–temperature conditions of c. 10–11 kbar and c. 700°C. Resolving this enigma is challenging but implies downward heating into the Indian plate, coupled with later development of unconformity parallel shear zones that detach Upper Paleozoic–Cenozoic cover rocks from Neoproterozoic to Paleozoic basement rocks and also detach those rocks from the Paleoproterozoic basement.

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11

Searle, M. P., R. R. Parrish, K. V. Hodges, A. Hurford, M. W. Ayres, and M. J. Whitehouse. "Shisha Pangma Leucogranite, South Tibetan Himalaya: Field Relations, Geochemistry, Age, Origin, and Emplacement." Journal of Geology 105, no. 3 (May 1997): 295–318. http://dx.doi.org/10.1086/515924.

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12

Liu, Zhi-Chao, Fu-Yuan Wu, Zhi-Li Qiu, Jian-Gang Wang, Xiao-Chi Liu, Wei-Qiang Ji, and Chuan-Zhou Liu. "Leucogranite geochronological constraints on the termination of the South Tibetan Detachment in eastern Himalaya." Tectonophysics 721 (November 2017): 106–22. http://dx.doi.org/10.1016/j.tecto.2017.08.019.

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13

Liu, Zhi-Chao, Fu-Yuan Wu, Lin Ding, Xiao-Chi Liu, Jian-Gang Wang, and Wei-Qiang Ji. "Highly fractionated Late Eocene (~ 35 Ma) leucogranite in the Xiaru Dome, Tethyan Himalaya, South Tibet." Lithos 240-243 (January 2016): 337–54. http://dx.doi.org/10.1016/j.lithos.2015.11.026.

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14

Liu, Zhi-Chao, Fu-Yuan Wu, Wei-Qiang Ji, Jian-Gang Wang, and Chuan-Zhou Liu. "Petrogenesis of the Ramba leucogranite in the Tethyan Himalaya and constraints on the channel flow model." Lithos 208-209 (November 2014): 118–36. http://dx.doi.org/10.1016/j.lithos.2014.08.022.

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15

Visona', Dario, Rodolfo Carosi, Chiara Montomoli, Massimo Tiepolo, and Luca Peruzzo. "Miocene andalusite leucogranite in central-east Himalaya (Everest–Masang Kang area): Low-pressure melting during heating." Lithos 144-145 (July 2012): 194–208. http://dx.doi.org/10.1016/j.lithos.2012.04.012.

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16

ANNEN, C., B. SCAILLET, and R. S. J. SPARKS. "Thermal Constraints on the Emplacement Rate of a Large Intrusive Complex: The Manaslu Leucogranite, Nepal Himalaya." Journal of Petrology 47, no. 1 (August 16, 2005): 71–95. http://dx.doi.org/10.1093/petrology/egi068.

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17

Ji, Wei-Qiang, Fu-Yuan Wu, Xiao-Chi Liu, Zhi-Chao Liu, Chang Zhang, Tong Liu, Jian-Gang Wang, and Scott R. Paterson. "Pervasive Miocene melting of thickened crust from the Lhasa terrane to Himalaya, southern Tibet and its constraint on generation of Himalayan leucogranite." Geochimica et Cosmochimica Acta 278 (June 2020): 137–56. http://dx.doi.org/10.1016/j.gca.2019.07.048.

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18

France-Lanord, Christian, Simon M. F. Sheppard, and Patrick Le Fort. "Hydrogen and oxygen isotope variations in the high himalaya peraluminous Manaslu leucogranite: Evidence for heterogeneous sedimentary source." Geochimica et Cosmochimica Acta 52, no. 2 (February 1988): 513–26. http://dx.doi.org/10.1016/0016-7037(88)90107-x.

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19

Searle, Michael P., and Laurent Godin. "The South Tibetan Detachment and the Manaslu Leucogranite: A Structural Reinterpretation and Restoration of the Annapurna‐Manaslu Himalaya, Nepal." Journal of Geology 111, no. 5 (September 2003): 505–23. http://dx.doi.org/10.1086/376763.

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20

Liu, Chen, Ru-Cheng Wang, Fu-Yuan Wu, Lei Xie, Xiao-Chi Liu, Xing-Kui Li, Lei Yang, and Xue-Jiao Li. "Spodumene pegmatites from the Pusila pluton in the higher Himalaya, South Tibet: Lithium mineralization in a highly fractionated leucogranite batholith." Lithos 358-359 (April 2020): 105421. http://dx.doi.org/10.1016/j.lithos.2020.105421.

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21

Noble, S. R., and M. P. Searle. "Age of crustal melting and leucogranite formation from U-Pb zircon and monazite dating in the western Himalaya, Zanskar, India." Geology 23, no. 12 (1995): 1135. http://dx.doi.org/10.1130/0091-7613(1995)023<1135:aocmal>2.3.co;2.

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22

Harrison, T. Mark, Keith I. Mahon, Stéphane Guillot, Kip Hodges, Patrick Le Fort, and Arnaud Pêcher. "New constraints on the age of the Manaslu leucogranite: Evidence for episodic tectonic denudation in the central Himalaya: Comment and Reply." Geology 23, no. 5 (1995): 478. http://dx.doi.org/10.1130/0091-7613(1995)023<0478:ncotao>2.3.co;2.

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23

Pognante, U., D. Castelli, P. Benna, G. Genovese, F. Oberli, M. Meier, and S. Tonarini. "The crystalline units of the High Himalayas in the Lahul–Zanskar region (northwest India): metamorphic–tectonic history and geochronology of the collided and imbricated Indian plate." Geological Magazine 127, no. 2 (March 1990): 101–16. http://dx.doi.org/10.1017/s0016756800013807.

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AbstractIn the High Himalayan belt of northwest India, crustal thickening linked to Palaeogene collision between India and Eurasia has led to the formation of two main crystalline tectonic units separated by the syn-metamorphic Miyar Thrust: the High Himalayan Crystallines sensu stricto (HHC) at the bottom, and the Kade Unit at the top. These units are structurally interposed between the underlying Lesser Himalaya and the very low-grade sediments of the Tibetan nappes. They consist of paragneisses, orthogneisses, minor metabasics and, chiefly in the HHC, leucogranites. The HHC registers: a polyphase metamorphism with two main stages designated as M1 and M2; a metamorphic zonation with high-temperature recrystallization and migmatization at middle structural levels and medium-temperature assemblages at upper and lower levels. In contrast, the Kade Unit underwent a low-temperature metamorphism. Rb–Sr and U–Th–Pb isotope data point to derivation of the orthogneisses from early Palaeozoic granitoids, while the leucogranites formed by anatexis of the HHC rocks and were probably emplaced during Miocene time.Most of the complicated metamorphic setting is related to polyphase tectonic stacking of the HHC with the ‘cooler’ Kade Unit and Lesser Himalaya during the Himalayan history. However, a few inconsistencies exist for a purely Himalayan age of some Ml assemblages of the HHC. As regards the crustal-derived leucogranites, the formation of a first generation mixed with quartzo-feldspathic leucosomes was possibly linked to melt-lubricated shear zones which favoured rapid crustal displacements; at upper levels they intruded during stage M2 and the latest movements along the syn-metamorphic Miyar Thrust, but before juxtaposition of the Tibetan nappes along the late- metamorphic Zanskar Fault.

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24

Whittington, Alan, Pascal Richet, Harald Behrens, François Holtz, and Bruno Scaillet. "Experimental temperature–X(H2O)–viscosity relationship for leucogranites and comparison with synthetic silicic liquids." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, no. 1-2 (March 2004): 59–71. http://dx.doi.org/10.1017/s0263593300000924.

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ABSTRACTViscosities of liquid albite (NaAlSi3O8) and a Himalayan leucogranite were measured near the glass transition at a pressure of one atmosphere for water contents of 0, 2·8 and 3·4 wt.%. Measured viscosities range from 1013·8 Pa. s at 935 K to 109·0 Pa. s at 1119 K for anhydrous granite, and from 1010·2 Pa. s at 760 K to 1012·9 Pa. s at 658 K for granite containing 3·4 wt.% H2O. The leucogranite is the first naturally occurring liquid composition to be investigated over the wide range of T-X(H2O) conditions which may be encountered in both plutonic and volcanic settings. At typical magmatic temperatures of 750°C, the viscosity of the leucogranite is 1011·0 Pa. s for the anhydrous liquid, dropping to 106·5 Pa. s for a water content of 3 wt.% H2O. For the same temperature, the viscosity of liquid NaAlSi3O8 is reduced from 1012·2 to 106·3 Pa. s by the addition of 1·9 wt.% H2O. Combined with published high-temperature viscosity data, these results confirm that water reduces the viscosity of NaAlSi3O8 liquids to a much greater degree than that of natural leucogranitic liquids. Furthermore, the viscosity of NaAlSi3O8 liquid becomes substantially nonArrhenian at water contents as low as 1 wt.% H2O, while that of the leucogranite appears to remain close to Arrhenian to at least 3 wt.% H2O, and viscosity–temperature relationships for hydrous leucogranites must be nearly Arrhenian over a wide range of temperature and viscosity. Therefore, the viscosity of hydrous NaAlSi3O8 liquid does not provide a good model for natural granitic or rhyolitic liquids, especially at lower temperatures and water contents.Qualitatively, the differences can be explained in terms of configurational entropy theory because the addition of water should lead to higher entropies of mixing in simple model compositions than in complex natural compositions. This hypothesis also explains why the water reduces magma viscosity to a larger degree at low temperatures, and is consistent with published viscosity data for hydrous liquid compositions ranging from NaAlSi3O8 and synthetic haplogranites to natural samples. Therefore, predictive models of magma viscosity need to account for compositional variations in more detail than via simple approximations of the degree of polymerisation of the melt structure.

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25

Nabelek, Peter I., and Mian Liu. "Petrologic and thermal constraints on the origin of leucogranites in collisional orogens." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, no. 1-2 (March 2004): 73–85. http://dx.doi.org/10.1017/s0263593300000936.

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ABSTRACTLeucogranites are typical products of collisional orogenies. They are found in orogenic terranes of different ages, including the Proterozoic Trans-Hudson orogen, as exemplified in the Black Hills, South Dakota, and the Appalachian orogen in Maine, both in the USA, and the ongoing Himalayan orogen. Characteristics of these collisional leucogranites show that they were derived from predominantly pelitic sources at the veining stages of deformation and metamorphism in upper plates of thickened crusts. Once generated, the leucogranite magmas ascended as dykes and were emplaced within shallower parts of their source sequences. In these orogenic belts, there was a strong connection between deformation, metamorphism and granite generation. However, the heat sources needed for partial melting of the source rocks remain controversial. Lack of evidence for significant intrusion of mafic magmas necessary to cause melting of upper plate source rocks suggests that leucogranite generation in collisional orogens is mainly a crustal process.The present authors evaluate five types of thermal models which have previously been proposed for generating leucogranites in collisional orogens. The first, a thickened crust with exponentially decaying distribution of heat-producing radioactive isotopes with depth, has been shown to be insufficient for heating the upper crust to melting conditions. Four other models capable of raising the crustal temperatures sufficiently to initiate partial melting of metapelites in thickened crust include: (1) thick sequences of sedimentary rocks with high amounts of internal radioactive heat production; (2) decompression melting; (3) thinning of mantle lithosphere; and (4) shear-heating. The authors show that, for reasonable boundary conditions, shear-heating along crustal-scale shear zones is the most viable process to induce melting in upper plates of collisional orogens where pelitic source lithologies are usually located. The shear-heating model directly links partial melting to the deformation and metamorphism that typically precede leucogranite genera

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26

Hopkinson, Thomas, Nigel Harris, Nick M. W. Roberts, Clare J. Warren, Sam Hammond, Christopher J. Spencer, and Randall R. Parrish. "Evolution of the melt source during protracted crustal anatexis: An example from the Bhutan Himalaya." Geology 48, no. 1 (November 19, 2019): 87–91. http://dx.doi.org/10.1130/g47078.1.

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Abstract The chemical compositions of magmatic zircon growth zones provide powerful insight into evolving magma compositions due to their ability to record both time and the local chemical environment. In situ U-Pb and Hf isotope analyses of zircon rims from Oligocene–Miocene leucogranites of the Bhutan Himalaya reveal, for the first time, an evolution in melt composition between 32 and 12 Ma. The data indicate a uniform melt source from 32 Ma to 17 Ma, and the progressive addition of an older source component to the melt from at least ca. 17 Ma. Age-corrected ɛHf ratios decrease from between −10 and −15 down to values as low as −23 by 12 Ma. Complementary whole-rock Nd isotope data corroborate the Hf data, with a progressive decrease in ɛNd(t) from ca. 18 to 12 Ma. Published zircon and whole-rock Nd data from different lithotectonic units in the Himalaya suggest a chemical distinction between the younger Greater Himalayan Series (GHS) and the older Lesser Himalayan Series (LHS). The time-dependent isotopic evolution shown in the leucogranites demonstrates a progressive increase in melt contribution from older lithologies, suggestive of increasing LHS involvement in Himalayan melting over time. The time-resolved data are consistent with LHS material being progressively accreted to the base of the GHS from ca. 17 Ma, facilitated by deformation along the Main Central thrust. From 17 Ma, decompression, which had triggered anatexis in the GHS since the Paleogene, enabled melting in older sources from the accreted LHS, now forming the lowermost hanging wall of the thrust.

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27

Djerossem, Félix, Julien Berger, Olivier Vanderhaeghe, Moussa Isseini, Jérôme Ganne, and Armin Zeh. "Neoproterozoic magmatic evolution of the southern Ouaddaï Massif (Chad)." BSGF - Earth Sciences Bulletin 191 (2020): 34. http://dx.doi.org/10.1051/bsgf/2020032.

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This paper presents new petrological, geochemical, isotopic (Nd) and geochronological data on magmatic rocks from the poorly known southern Ouaddaï massif, located at the southern edge of the so-called Saharan metacraton. This area is made of greenschist to amphibolite facies metasediments intruded by large pre- to syn-tectonic batholiths of leucogranites and an association of monzonite, granodiorite and biotite granite forming a late tectonic high-K calc-alkaline suite. U-Pb zircon dating yields ages of 635 ± 3 Ma and 613 ± 8 Ma on a peraluminous biotite-leucogranite (containing numerous inherited Archean and Paleoproterozoic zircon cores) and a muscovite-leucogranite, respectively. Geochemical fingerprints are very similar to some evolved Himalayan leucogranites suggesting their parental magmas were formed after muscovite and biotite dehydration melting of metasedimentary rocks. A biotite-granite sample belonging to the late tectonic high-K to shoshonitic suite contains zircon rims that yield an age of 540 ± 5 Ma with concordant inherited cores crystallized around 1050 Ma. Given the high-Mg# (59) andesitic composition of the intermediate pyroxene-monzonite, the very similar trace-element signature between the different rock types and the unradiogenic isotopic signature for Nd, the late-kinematic high-K to shoshonitic rocks formed after melting of the enriched mantle and further differentiation in the crust. These data indicate that the southern Ouaddaï was part of the Pan-African belt. It is proposed that it represents a continental back-arc basin characterized by a high-geothermal gradient during Early Ediacaran leading to anatexis of middle to lower crustal levels. After tectonic inversion during the main Pan-African phase, late kinematic high-K to shoshonitic plutons emplaced during the final post-collisional stage.

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28

France-Lanord, Christian, and Patrick Le Fort. "Crustal melting and granite genesis during the Himalayan collision orogenesis." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 79, no. 2-3 (1988): 183–95. http://dx.doi.org/10.1017/s0263593300014206.

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ABSTRACTThis paper reviews the petrogenesis of Himalayan leucogranites (HHγ) on the basis of field, petrological and geochemical data collected over the last fifteen years. HHγ are intruded at the top of the 2 to 8km-thick High Himalayan Crystallines (HHC). These are metamorphosed (Ky to Sill) and present much evidence of partial melting. During the MCT thrusting, the already metamorphosed HHC were thrust on top of the weakly metamorphosed Midland Formations, inducing the main phase of Himalayan metamorphism. The genesis of HHγ and North Himalaya leucogranites (NHγ) associates thrusting along the MCT, propagation of inverted metamorphism, liberation of large quantities of fluid in the Midlands, and partial melting of the HHC.The restricted compositions of the granites are close to minimum melt compositions; variations in the alkali ratio probably relate to the variable amount of B, F and H2O. The HHγ were issued from the migmatitic zone around 700°C and 800 MPa., and still emplaced some 10 to 15 km below the surface. This syn- to late-tectonic emplacement of the leucogranites lasted for more than 10 Ma according to isotopic ages (25 to 14 Ma).O, Rb–Sr, Nd–Sm and Pb isotope studies corroborate the unambiguous filiation between the HHC and the leucogranites in central Nepal. They also imply that the plutons are generated as numerous poorly mixed batches of magma produced preferentially in specific zones of the source rock. δD values may be explained by infiltration of water from the Midlands in the melting zone, and/or by water degassing during crystallisation. The positive covariations between Sr-, Nd- and O-isotope ratios relate to the variations in the original sediment composition of the source gneisses. Whereas trace element characteristics often date back to the anatectic process, limited magmatic differentiation is recorded by the biotite. These granites are typical crustal products, keeping track of some of the pre-Himalayan evolution together with that of their own origin.

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29

Searle, M. P., J. M. Cottle, M. J. Streule, and D. J. Waters. "Crustal melt granites and migmatites along the Himalaya: melt source, segregation, transport and granite emplacement mechanisms." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 219–33. http://dx.doi.org/10.1017/s175569100901617x.

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ABSTRACTIndia–Asia collision resulted in crustal thickening and shortening, metamorphism and partial melting along the 2200 km-long Himalayan range. In the core of the Greater Himalaya, widespread in situ partial melting in sillimanite+K-feldspar gneisses resulted in formation of migmatites and Ms+Bt+Grt+Tur±Crd±Sil leucogranites, mainly by muscovite dehydration melting. Melting occurred at shallow depths (4–6 kbar; 15–20 km depth) in the middle crust, but not in the lower crust. 87Sr/86Sr ratios of leucogranites are very high (0·74–0·79) and heterogeneous, indicating a 100 crustal protolith. Melts were sourced from fertile muscovite-bearing pelites and quartzo-feldspathic gneisses of the Neo-Proterozoic Haimanta–Cheka Formations. Melting was induced through a combination of thermal relaxation due to crustal thickening and from high internal heat production rates within the Proterozoic source rocks in the middle crust. Himalayan granites have highly radiogenic Pb isotopes and extremely high uranium concentrations. Little or no heat was derived either from the mantle or from shear heating along thrust faults. Mid-crustal melting triggered southward ductile extrusion (channel flow) of a mid-crustal layer bounded by a crustal-scale thrust fault and shear zone (Main Central Thrust; MCT) along the base, and a low-angle ductile shear zone and normal fault (South Tibetan Detachment; STD) along the top. Multi-system thermochronology (U–Pb, Sm–Nd, 40Ar–39Ar and fission track dating) show that partial melting spanned ̃24–15 Ma and triggered mid-crustal flow between the simultaneously active shear zones of the MCT and STD. Granite melting was restricted in both time (Early Miocene) and space (middle crust) along the entire length of the Himalaya. Melts were channelled up via hydraulic fracturing into sheeted sill complexes from the underthrust Indian plate source beneath southern Tibet, and intruded for up to 100 km parallel to the foliation in the host sillimanite gneisses. Crystallisation of the leucogranites was immediately followed by rapid exhumation, cooling and enhanced erosion during the Early–Middle Miocene.

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30

Brunel, Maurice, and Jean-Robert Kienast. "Étude pétro-structurale des chevauchements ductiles himalayens sur la transversale de l'Everest–Makalu (Népal oriental)." Canadian Journal of Earth Sciences 23, no. 8 (August 1, 1986): 1117–37. http://dx.doi.org/10.1139/e86-111.

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Tectonic and microtectonic data in eastern Nepal indicate that the major observed thrusting (100 km) on the Main Central Thrust (MCT) postdates the Barrovian metamorphism of the High Himalaya gneisses. This result, at variance with the famous "reverse metamorphism model," better explains the abnormal metamorphic superpositions in the Himalayas and accounts for the lack of high-pressure assemblages under the thick, allochtonous High Himalaya Tibetan slab.Pressure and temperature estimates by microprobe analysis on plagioclase, biotite, garnet, kyanite, sillimanite, and cordierite assemblages are presented for samples collected along the MCT shear zone and across the gneiss slab in the Everest–Makalu area. Since there is very little difference in pressure at the front of the slab (Kathmandu Klippe) and its root, these estimates support the existence of important late metamorphic thrusting. The decrease of pressure towards the top of the gneiss pile, combined with a small temperature increase, explains the kyanite–sillimanite transition. The reverse metamorphism model, which implies refolded isograds, predicts heat loss by conduction throughout the sole of the thrust; pressure–temperature variations and kyanite–sillimanite transition phases more likely reflect a late heat supply in the upper part of the gneisses. Intrusion of leucogranitic bodies, confined to the interface with the Tethyan sediments, could account for this heat supply.A new tectonic evolution model of the Himalayan intracrustal thrusts is discussed. Without completely denying the existence of a reverse metamorphism synchronous with the phases of early shearing, it can be shown that the metamorphic zonation seen at present was governed by the structure of the later shearing.

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31

Visonà, D. "Two-mica and tourmaline leucogranites from the Everest–Makalu region (Nepal–Tibet). Himalayan leucogranite genesis by isobaric heating?" Lithos 62, no. 3-4 (June 2002): 125–50. http://dx.doi.org/10.1016/s0024-4937(02)00112-3.

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32

Searle, M. P. "Emplacement of Himalayan leucogranites by magma injection along giant sill complexes: examples from the Cho Oyu, Gyachung Kang and Everest leucogranites (Nepal Himalaya)." Journal of Asian Earth Sciences 17, no. 5-6 (October 1999): 773–83. http://dx.doi.org/10.1016/s1367-9120(99)00020-6.

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33

Pichavant, Michel, Tahar Hammouda, and Bruno Scaillet. "Control of redox state and Sr isotopic composition of granitic magmas: a critical evaluation of the role of source rocks." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 87, no. 1-2 (1996): 321–29. http://dx.doi.org/10.1017/s0263593300006714.

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ABSTRACT:The current underlying assumption in most geochemical studies of granitic rocks is that granitic magmas reflect their source regions. However, the mechanisms by which source rocks control the intensive and compositional parameters of the magmas remain poorly known. Recent experimental data are used to evaluate the ‘source rock model’ and to discuss controls of (1) redox states and (2) the Sr isotopic compositions of granitic magmas.Experimental studies have been performed in parallel on biotite-muscovite and tourmaline-muscovite leucogranites from the High Himalayas. Results under reducing conditions ( = FMQ – 0·5) at 4 kbar and variable suggest that the tourmaline-muscovite granite evolved under progressively more oxidising conditions during crystallisation, up to values more than four log units above the FMQ buffer. Leucogranite magmas thus provide an example of the control of redox conditions by post-segregation rather than by partial melting processes.Other experiments designed to test the mechanisms of isotopic equilibration of Sr during partial melting of a model crustal assemblage show that kinetic factors can dominate the isotopic signature in the case of source rocks not previously homogenised during an earlier metamorphic event. The possibility is therefore raised that partial melts may not necessarily reflect the Sr isotopic composition of their sources, weakening in a fundamental way the source rock model.

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34

Le Fort, P., M. Cuney, C. Deniel, C. France-Lanord, S. M. F. Sheppard, B. N. Upreti, and P. Vidal. "Crustal generation of the Himalayan leucogranites." Tectonophysics 134, no. 1-3 (March 1987): 39–57. http://dx.doi.org/10.1016/0040-1951(87)90248-4.

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35

Deniel, Catherine, Philippe Vidal, Angel Fernandez, Patrick Le Fort, and Jean-Jacques Peucat. "Isotopic study of the Manaslu granite (Himalaya, Nepal): inferences on the age and source of Himalayan leucogranites." Contributions to Mineralogy and Petrology 96, no. 1 (May 1987): 78–92. http://dx.doi.org/10.1007/bf00375529.

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36

Aikman, Amos B., T. Mark Harrison, and Ding Lin. "Preliminary Results from the Yala-Xiangbo Leucogranite Dome, SE Tibet." Himalayan Journal of Sciences 2, no. 4 (January 21, 2008): 91. http://dx.doi.org/10.3126/hjs.v2i4.809.

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37

Butler, Robert W. H., Nigel B. W. Harris, and Alan G. Whittington. "Interactions between deformation, magmatism and hydrothermal activity during active crustal thickening: a field example from Nanga Parbat, Pakistan Himalayas." Mineralogical Magazine 61, no. 404 (February 1997): 37–52. http://dx.doi.org/10.1180/minmag.1997.061.404.05.

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AbstractThe Nanga Parbat massif is a rapidly eroding, thrust-related antiform that is distinct from other regions of the Himalayan orogen in being both intruded by Late Miocene-Pliocene anatectic granites and permeated by a vigorous hydrothermal system. Exhumation is achieved by erosion during thrusting along the Liachar thrust in the apparent absence of extensional tectonics. At depths in excess of 20 km, small batches of leucogranitic melt have been generated by fluid-absent breakdown of muscovite from metapelitic lithologies. These melts ascend several kilometres prior to emplacement, aided by low geothermal gradients at depth and by interaction with meteoric water as they reach shallow levels. At intermediate depths (∼15 km) limited fluid infiltration is restricted to shear zones resulting in localised anatexis. Within the upper 8 km of crust, magmatic and meteoric fluid fluxes are channelised by active structures providing a feedback mechanism for focusing deformation. Leucogranite sheets show a range of pre-full crystallization and high-temperature crystal-plastic textures indicative of strain localisation onto these sheets and away from the country rocks. At subsolidus temperatures meteoric fluids promote strain localisation and may trigger cataclastic deformation. Since near-surface geothermal gradients are unusually steep, the macroscopic transition between distributed shearing and substantial, but localised, cataclastic deformation occurred at amphibolite-facies conditions (∼600°C). Even with the greatest topographic relief in the world, the meteoric system of Nanga Parbat is effectively restricted to the upper 8 km of the crust, strongly controlled by active structures.

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38

Han, Jinsheng, Pete Hollings, Fred Jourdan, Yunchuan Zeng, and Huayong Chen. "Inherited Eocene magmatic tourmaline captured by the Miocene Himalayan leucogranites." American Mineralogist 105, no. 9 (September 1, 2020): 1436–40. http://dx.doi.org/10.2138/am-2020-7608.

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Abstract The Miocene Cuonadong leucogranites in the easternmost section of the Tethyan Himalaya, Southern Tibet, are characterized by two types of tourmaline. Tourmaline occurs as needle-like crystals in the two-mica ± tourmaline granites (Tur G) and large patches in the pegmatites (Tur P). Both the granite and the pegmatites yield Miocene ages (ca. 20 Ma) based on monazite U(-Th)-Pb dating, whereas 40Ar/39Ar geochronology of the coarse-grained tourmalines (Tur P) crosscut by pegmatite veins yielded an Eocene mini-plateau age of 43 ± 6 Ma. Major element concentrations of tourmaline indicate that both Tur P and Tur G belong to the schorl group with a magmatic origin, but trace elements such as V indicate that they are not cogenetic. Boron isotopes suggest that Tur P (average –9.76‰) was derived from typical crustal sources, whereas Tur G (average –7.65‰) contains relatively more mafic input. The capture of Eocene tourmaline by the Miocene leucogranites at Cuonadong suggests that the crustally derived Eocene magmatism may have occurred in the southern Tethyan Himalaya. Identification of the inherited magmatic tourmaline (Tur P), although not common, challenges the current application of tourmaline chemistry to the investigation of magmatic-hydrothermal systems.

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39

Gou, Zhengbin, Zeming Zhang, Xin Dong, Hua Xiang, Huixia Ding, Zuolin Tian, and Hengcong Lei. "Petrogenesis and tectonic implications of the Yadong leucogranites, southern Himalaya." Lithos 256-257 (July 2016): 300–310. http://dx.doi.org/10.1016/j.lithos.2016.04.009.

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40

Gou, Zhengbin, Xin Dong, and Baodi Wang. "Petrogenesis and Tectonic Implications of the Paiku Leucogranites, Northern Himalaya." Journal of Earth Science 30, no. 3 (June 2019): 525–34. http://dx.doi.org/10.1007/s12583-019-1219-8.

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41

Wu, Fu-Yuan, Xiao-Chi Liu, Zhi-Chao Liu, Ru-Cheng Wang, Lei Xie, Jia-Min Wang, Wei-Qiang Ji, et al. "Highly fractionated Himalayan leucogranites and associated rare-metal mineralization." Lithos 352-353 (January 2020): 105319. http://dx.doi.org/10.1016/j.lithos.2019.105319.

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42

Rochette, Pierre, Bruno Scaillet, Stéphane Guillot, Patrick Le Fort, and Arnaud Pêcher. "Magnetic properties of the High Himalayan leucogranites: Structural implications." Earth and Planetary Science Letters 126, no. 4 (September 1994): 217–34. http://dx.doi.org/10.1016/0012-821x(94)90108-2.

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43

ZhiChao, LIU, WU FuYuan, LIU XiaoChi, and WANG JianGang. "The mechanisms of fractional crystallization for the Himalayan leucogranites." Acta Petrologica Sinica 36, no. 12 (2020): 3551–71. http://dx.doi.org/10.18654/1000-0569/2020.12.01.

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44

Villa, Igor M. "Excess Ar geochemistry and geochronology of a non-equilibrium himalayan leucogranite." Chemical Geology 70, no. 1-2 (August 1988): 74. http://dx.doi.org/10.1016/0009-2541(88)90409-3.

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45

Yang, Lei, Xiao-Chi Liu, Jia-Min Wang, and Fu-Yuan Wu. "Is Himalayan leucogranite a product by in situ partial melting of the Greater Himalayan Crystalline? A comparative study of leucosome and leucogranite from Nyalam, southern Tibet." Lithos 342-343 (October 2019): 542–56. http://dx.doi.org/10.1016/j.lithos.2019.06.007.

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46

Weinberg, R. F. "Himalayan leucogranites and migmatites: nature, timing and duration of anatexis." Journal of Metamorphic Geology 34, no. 8 (July 11, 2016): 821–43. http://dx.doi.org/10.1111/jmg.12204.

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47

Guillot, S., and P. Le Fort. "Geochemical constraints on the bimodal origin of High Himalayan leucogranites." Lithos 35, no. 3-4 (June 1995): 221–34. http://dx.doi.org/10.1016/0024-4937(94)00052-4.

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48

Ayres, Michael, Nigel Harris, and Derek Vance. "Possible constraints on anatectic melt residence times from accessory mineral dissolution rates: an example from Himalayan leucogranites." Mineralogical Magazine 61, no. 404 (February 1997): 29–36. http://dx.doi.org/10.1180/minmag.1997.061.404.04.

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AbstractThe concentrations of LREE and Zr in a granitic melt formed by anatexis of a metapelitic protolith will be buffered by the stability of monazite and zircon respectively. The rate at which equilibrium is reached between dissolving monazite and zircon and a static melt is limited by the rate at which Zr and LREE can diffuse away from dissolution sites. If melt extraction rates exceed the rates at which the LREE and Zr in the melt become homogenized by diffusion, extracted melts will be undersaturated with respect to these elements. Evidence from accessory phase thermometry suggests that for many Himalayan leucogranites generated by crustal anatexis, the melts equilibrated with restitic monazite and zircon prior to extraction. In contrast, discordant temperatures determined from accessory phase thermometry suggest that tourmaline leucogranites from the Zanskar region of NW India did not equilibrate prior to extraction. Quantitative interpretation of this discordance assumes that the melt was static prior to extraction, and that accessory phase inheritance was minimal. Modelling of the time-dependant homogenization process suggests that tourmaline leucogranites generated at 700°C probably remained in contact with restitic monazite in the protolith for less than 7 ka and certainly less than 50 ka. Such rapid extraction rates suggest that deformation-driven mechanisms were important in removing these melts from their source.

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49

Weinberg, Roberto F., and Mike P. Searle. "Volatile‐Assisted Intrusion and Autometasomatism of Leucogranites in the Khumbu Himalaya, Nepal." Journal of Geology 107, no. 1 (January 1999): 27–48. http://dx.doi.org/10.1086/314330.

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50

Zeitler, Peter K., and C. Page Chamberlain. "Petrogenetic and tectonic significance of young leucogranites from the northwestern Himalaya, Pakistan." Tectonics 10, no. 4 (August 1991): 729–41. http://dx.doi.org/10.1029/91tc00168.

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