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![Concordia diagrams for dated accessory phases for discrete porphyritic pluton bodies: (A) Donggong, (B) Gomdre, and (C) Mabja. Cathodoluminescence (CL) and digital photomicrograph images show accessory mineral grains yielding concordant analyses; numbered boxes and circles represent the analysis number (i.e., JK4/12az1–1 in Table DR1 [see text footnote 1]) and box-raster and spot dimensions , respectively. Errors are depicted at 1σ.](profile/Jess-King-6/publication/43642904/figure/fig6/AS:394245446881283@1471006847139/Concordia-diagrams-for-dated-accessory-phases-for-discrete-porphyritic-pluton-bodies-A.png)
Concordia diagrams for dated accessory phases for discrete porphyritic pluton bodies: (A) Donggong, (B) Gomdre, and (C) Mabja. Cathodoluminescence (CL) and digital photomicrograph images show accessory mineral grains yielding concordant analyses; numbered boxes and circles represent the analysis number (i.e., JK4/12az1–1 in Table DR1 [see text footnote 1]) and box-raster and spot dimensions , respectively. Errors are depicted at 1σ.
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This geochemical, geochronological and structural study of intrusive rocks in the Sakya Dome of southern Tibet has identified two distinct suites of anatectic granites that carry contrasting implications for the tectonic evolution of the India-Asia collision zone. The northern margin of the dome core was intruded by anastomosing, equigranular two-m...
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The North Qaidam Orogenic Belt (NQOB), lying at the northern margin of the Tibet Plateau, records two orogenic cycles: A Proterozoic cycle related to the amalgamation and breakup of the supercontinent Rodinia, and an Early Palaeozoic cycle including oceanic subduction and continental deep subduction. At present, the only information about the Prote...
The Higher Himalayan Crystalline Sequences in the core of the Himalayan orogenic belt was produced by the Cenozoic collision of Indian and Asian plates, and record the history of formation and evolution of the orogenic belt. Here we present a detailed petrological and zircon U-Pb geochronological study of the pelitic granulitesfrom the Yadong area,...
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Granulitized eclogite-facies rocks exposed in the Ama Drime Massif, south Tibet, were dated by Lu-Hf garnet geochronology. Garnet from the three samples analyzed yielded Lu-Hf ages of 37.5 +/- 0.8 Ma, 36.0 +/- 1.9 Ma, and 33.9 +/- 0.8 Ma. Eclogitic garnet growth is estimated at ca. 38 Ma, the oldest age for burial of the lower Indian crust beneath...
We report the occurrence, mineralogy, whole-rock geochemistry, and geochronology of two types of eclogites newly discovered in the western Bangong Meso–Tethyan suture zone (Gaize, central Tibet, western China). Type 1 eclogites contain a peak metamorphic mineral assemblage of garnet + clinopyroxene whereas Type 2 ones are characterized by a peak me...
Citations
... In addition to the crustal duplexing mechanism of gneiss dome exposure, it is necessary to consider the influence of the underthrust geometry of the Indian crust (King et al., 2011;Lee et al., 2004;Quigley et al., 2008). According to the electrical structure (Figures 5a and 5b), the top interface of the resistive body R2 in the western profile is approximately 20 km, while in the eastern profile it increases to 40 km. ...
Plain Language Summary
The Himalayan Orogenic Belt (HOB) is an ideal place to study the deep‐shallow coupling relationship of the continental collision system. Magnetotelluric sounding (MT) is a powerful tool for detecting the internal structure and state of collision zones. However, most of the previous results have been overprinted by north–south trending rifts. Therefore, a high‐resolution three‐dimensional electrical resistivity model was obtained across the central HOB through an MT profile between the Dingjie‐Shenzha and Yadong‐Gulu rifts, combined with the latest MT result from the Sikkim region. The electrical resistivity model revealed that the lower crust of the southern Lhasa Terrane is characterized by a moderate resistivity value of approximately 100 Ωm; this may have provided the magma source for the porphyry copper deposits in the eastern Gangdese metallogenic belt and the southward thermal migration in the northern Himalayas. The middle crust of the northern Himalayas is electrically discontinuous toward the south, mainly exhibiting high resistivity north of the north Himalayan gneiss domes (NHGD) belt. The middle crust of the northern Himalayas may have undergone partial melting and crystallization during southward uplift and migration. We found a strong coupling relationship between the surface NHGD belt and the underthrusting of the Indian crust.
... Previous studies indicated that the High Himalayan leucogranites were mainly formed in the early-middle Miocene from 26 Ma to 13 Ma (e.g., Carosi et al., 2013;Daniel et al., 2003;Guo and Wilson, 2012;Harrison et al., 1999;Hodges et al., 1996Hodges et al., , 1998Imayama et al., 2012;Schärer, 1984;Weinberg, 2016), with rare younger formation ages of ca. 12 Ma (e.g., Daniel et al., 2003;Schärer et al., 1986). The crystallization ages of granites in the core of the North Himalayan gneiss domes are mainly from 28 Ma to 14 Ma, nearly identical to those of the High Himalayan leucogranites (e.g., Aoya et al., 2005;Gao and Zeng, 2014;Gao et al., 2013;Guo et al., 2008;Kawakami et al., 2007;King et al., 2011;Lee et al., 2006;Lee and Whitehouse, 2007;Schärer et al., 1986). A minor amount of 9-6 Ma leucogranites were also documented in the North Himalayan gneiss domes (e.g., Guo et al., 2008;King et al., 2011;Liu et al., 2014;Schärer et al., 1986). ...
... The crystallization ages of granites in the core of the North Himalayan gneiss domes are mainly from 28 Ma to 14 Ma, nearly identical to those of the High Himalayan leucogranites (e.g., Aoya et al., 2005;Gao and Zeng, 2014;Gao et al., 2013;Guo et al., 2008;Kawakami et al., 2007;King et al., 2011;Lee et al., 2006;Lee and Whitehouse, 2007;Schärer et al., 1986). A minor amount of 9-6 Ma leucogranites were also documented in the North Himalayan gneiss domes (e.g., Guo et al., 2008;King et al., 2011;Liu et al., 2014;Schärer et al., 1986). In addition, a small volume of 48-35 Ma granites (Aikman et al., 2008;Ding et al., 2005;Hou et al., 2012;Larson et al., 2010;Li et al., 2020;Liu et al., 2014;Zeng et al., 2011) and 49-45 Ma mafic rocks (Ji et al., 2016;Ma et al., 2023), as well as very scarce early Paleozoic orthogneiss (ca. ...
... However, there is no evidence in the Tethyan Himalaya for extensive Eocene magmatism. In fact, it is less extensive than the Oligocene-Miocene magmatism (e.g., Harrison et al., 1999;King et al., 2011;Wu et al., 2015;Zhang et al., 2004). ...
Magmatism, structures, and metamorphism in the Ramba dome of the Tethyan Himalaya were investigated to shed light on orogenic processes during the early stages of the India-Asia collision. Deformed granite dikes in the dome envelope yield zircon U-Pb ages of ca. 45 Ma. These Eocene granites have adakitic, Na-rich compositions (K2O/Na2O = 0.20−0.61), weak to no Eu anomaly, enrichment in Sr, depletion in heavy rare earth elements and Y, and low MgO and Mg# contents. These characteristics contrast with the Miocene potassic granites in the core of the dome and suggest that the Eocene adakites were derived from the high-pressure melting of crustal amphibolites in a thick crust. The mica schists of the dome envelope have an early foliation (S1) that is overprinted by upright folds (F2). Phase-equilibria modeling of garnet and staurolite mica schists suggests a Barrovian-type, prograde P-T evolution in association with S1, with peak conditions of 6.7−7.2 kbar/590−605 °C and 7.3−7.8 kbar/650−670 °C, respectively, which are typical of crustal thickening metamorphism. Monazites from S1-dominated staurolite mica schists yield metamorphic ages of ca. 51−49 Ma, while those from the late foliation (S2) that transposed S1 give younger ages of ca. 10 Ma. The integration of geochemical, structural, metamorphic, and geochronological data suggests that peak Barrovian D1 metamorphism and adakitic magmatism occurred in the Eocene in response to crustal thickening. The results provide critical constraints for addressing the crustal shortening deficit of the region.
... The trends of fractional crystallization of Kfs + Pl in different proportions (25%, 50%, 75% Kfs) are calculated based on partition coefficients from Ewart and Griffin (1994). Data of the Himalayan leucogranites are compiled from: Guo and Wilson (2012), King et al. (2011);Liu et al. (2014Liu et al. ( , 2016, Singh et al. (2016), Visonà and Lombardo (2002), Yang et al. (2019); Zeng et al. (2011);Zhang et al. (2004); Zheng et al. (2016). Data of the Triassic granites are from Gao et al. (2017). ...
Several important processes in the petrogenesis of granite are still debated due to poor understanding of complex interactions between minerals during the melting and melt segregation processes. To promote improved understanding of the mineral-melt relationships, we present a systematic petrographic and geochemical analysis for melanosome and leucosome samples from the Triassic Jindong migmatite, South China. Petrographic observations and zircon U-Pb geochronology indicate that the Jindong migmatite was formed through water-fluxed melting of the Early Paleozoic gneissic granite (437±2 Ma) during the Triassic (238±1 Ma), with the production of melt dominated by the breakdown of K-feldspar, plagioclase and quartz. The Jindong leucosomes may be divided into lenticular and net-structured types. Muscovite, plagioclase and K-feldspar in the net-structured leucosome show higher Rb and much lower Ba and Sr contents than those in the lenticular leucosome. This may be attributed to elevation of Rb and decreasing Ba and Sr abundances in melts during the segregation process, due to early fractional crystallization of K-feldspar and plagioclase. These leucosomes show negative correlation between εNd(t) and P2O5, reflecting increasing dissolution of low εNd(t) apatite during melting process. The continuous dissolution of apatite caused saturation of monazite and xenotime in melt, resulting in the growth of monazite and xenotime around apatite in the melanosome. This process resulted in a sharp decrease of Th, Y and REE with increasing P2O5 in the leucosome samples. This complex interplay of accessory mineral reactions in the source impact REE geochemistry and Nd isotope ratios of granites. As the granites worldwide exhibit similar compositional and isotopic patterns with the Jindong leucosomes, we suggest that both the melting and melt segregation processes strongly control the granitic melt compositions.
... The leucogranites of the Himalayas include two-mica leucogranites, tourmaline leucogranites (Guillot and Le Fort, 1995), garnet leucogranites (Hopkinson et al., 2017) and cordierite leucogranites (Gou et al., 2019). Their emplacement define two sub-parallel belts (i) the northern belt known as the Tethyan Himalayan Leucogranites (THL), that intrude the THS and (ii) the southern belt referred to as Higher Himalayan Leucogranites (HHL) which intrudes into the high-grade metasedimentary rocks (King et al., 2011;Weinberg, 2016). ...
Himalayan leucogranites are important for understanding the tectonic evolution of collision zones in general and the causes of crustal melting in the Himalayan orogen in particular. This paper aims to understand the melt source and emplacement age of the leucogranites from Sikkim in order to decipher the deep geodynamic processes of the eastern Himalayas. Zircon U-Pb analysis of the Higher Himalayan Sequence (HHS) metamorphic core reveals a prolonged period of crustal melting between >33 to ca. 14 Ma. Major and trace element abundances are presented for 27 leucogranites from North Sikkim that are classified into two-mica and tourmaline leucogranite types. They are peraluminous in composition, characterized by high SiO2 (70.91–74.9 wt.%), Al2O3 (13.69–15.82 wt.%), and low MgO (0.13–0.74 wt.%). Elemental abundances suggest that Sikkim Himalayan leucogranites are derived from crustal melts. The two-mica leucogranites are derived from a metagreywacke source, whereas the tourmaline leucogranites are sourced from metapelitic sources, with inherited zircons indicating an HHS origin for both types. U-Pb zircon geochronology of the two mica leucogranites indicates ages of ca. 19–15 Ma, consistent with crustal melting recorded in HHS gneisses from Darjeeling. Monazites from both the two-mica and tourmaline granites yield a crystallization age of ca. 14 Ma, coeval with movement on the Main Central Thrust and South Tibetan Detachment System which further provides constraints on the timing and mechanism of petrogenesis of leucogranites in the Sikkim Himalayas.
... Beaumont et al., 2004). Other studies have been carried out to investigate the conditions and timing of metamorphism, partial melting, and the relationship with Cenozoic leucogranite in the gneiss domes of the NHGD, and the relationship with N-S-trending normal rifts, which have great implications on channel flow and/or tectonic exhumation (e.g., King et al., 2011;Zeng et al., 2011;Groppo et al., 2012;Liu et al., 2014;Cottle et al., 2015;Zhang et al., 2018;Ding et al., 2019;Yu et al., 2020;Chen et al., 2022;Xue et al., 2022). Additionally, Li et al. (2021) reported that a series of shear zones at depths of 10-15 km and two high-velocity bodies at depths of 3 km are located beneath Kangmar Gneiss Dome. ...
... It is reported that the multi-stage high-grade metamorphism and anatexis, which occurred from ~45 Ma to ~15 Ma during the Himalayan orogeny (King et al., 2011;Yu et al., 2011;Zhang et al., 2018), contributed to the formation of leucogranite and high-grade metamorphic rock in the Himalaya terrane Zhang et al., 2018). The presence of anatectic granites during the Oligocene-Miocene in the Mabja dome indicates southward extrusion of crustal materials (Nelson et al., 1996;Lee et al., 2006, Lee andWhitehouse, 2007;King et al., 2011), and the measured ages of dykes (12-9 Ma) constrain the time period for active southwards flow of crustal materials (King et al., 2007). ...
... It is reported that the multi-stage high-grade metamorphism and anatexis, which occurred from ~45 Ma to ~15 Ma during the Himalayan orogeny (King et al., 2011;Yu et al., 2011;Zhang et al., 2018), contributed to the formation of leucogranite and high-grade metamorphic rock in the Himalaya terrane Zhang et al., 2018). The presence of anatectic granites during the Oligocene-Miocene in the Mabja dome indicates southward extrusion of crustal materials (Nelson et al., 1996;Lee et al., 2006, Lee andWhitehouse, 2007;King et al., 2011), and the measured ages of dykes (12-9 Ma) constrain the time period for active southwards flow of crustal materials (King et al., 2007). However, thermochronology studies yield estimates of middle-Miocene cooling ages in the Mabja Dome (Lee et al., 2006), which may be a possible reason why a moderately-resistive zone is observed beneath the Mabja dome. ...
... 55 Ma (de Sigoyer et al., 2000;Garzanti, 2008) and associated crustal thickening, surface uplift, and magmatism. Cenozoic magmatism on the Tibetan plateau shows systematic variations in space and time that are related to Tibetan tectonic evolution (Zhang H. F. et al., 2004;Zhang P. et al., 2004;Zhang Y. et al., 2004;Chung et al., 2005;King et al., 2011;Wang et al., 2012). The magmatism resulting from deeper crustal partial melting is one of the key pieces of evidence for differentiating tectonic processes from central to eastern Tibet (Figure 1). ...
The eastern margin of the Tibetan Plateau has given rise to much debate about mechanisms of plateau uplift and evolution and, in particular, the role of the lower crust in crustal thickening. Knowledge of the middle to lower crust conditions is critical for evaluating various models of crustal deformation, but data on crustal evolution through time are lacking. Here, we turn to the Gongga Shan granite, an intrusion along the Xianshuihe fault in easternmost Tibet that directly records local Cenozoic crustal conditions. We present 124 U-Pb samples from the Gongga Shan granite (GSG) that prove that the crust has been stepwise producing partial melt from 56 Ma to 4 Ma. According to the age distribution, the GSG can be separated into four major groups with ages of 4–10 Ma, 12–20 Ma, 25–40 Ma, and 43–56 Ma. Combining the timing information with geophysics and low-temperature thermochronology data, we suggest that events younger than 10 Ma may indicate the onset of recent crustal channel flow in the middle to lower crust. In contrast, the youngest 4 Ma ages indicate the ongoing partial melting of the middle crust. The 12–20 Ma events could be related to an earlier stage of crustal channel flow, consistent with the regional large-scale crustal channel flow in central Tibet.
... The Himalayan leucogranites are the products of the partial melting of crustal rocks and offer an outstanding case to formulate and test petrogenetic models for granites and the linkage of melting modes with the tectonic transition of orogenic belts . Experimental results (Patiño Douce and Harris, 1998;Yang et al., 2001), theoretical calculations (Harris and Inger, 1992), and geochemical observations (Harris and Massey, 1994;Zhang et al., 2004;King et al., 2011;Gao et al., 2017;Zeng and Gao, 2017) suggested that most Himalayan Cenozoic leucogranites are derived from fluid-absent melting of muscovite in metasedimentary source rocks. In the past 10 years, an increasing number of studies have documented that granites with a characteristic signature of high CaO, Sr, and Ba but low Rb/Sr ratios are more widespread than previously thought and require fluid-fluxed melting of metasedimentary sources as a dominant melting mechanism (Prince et al., 2001;Zhang et al., 2004;King et al., 2011;Guo and Wilson, 2012;Zeng et al., 2012;Gao and Zeng, 2014;Gao et al., 2017;Huang et al., 2017;Bartoli et al., 2019;Fan et al., 2021;Meng et al., 2021;Liu et al., 2022aLiu et al., , 2022b. ...
... Experimental results (Patiño Douce and Harris, 1998;Yang et al., 2001), theoretical calculations (Harris and Inger, 1992), and geochemical observations (Harris and Massey, 1994;Zhang et al., 2004;King et al., 2011;Gao et al., 2017;Zeng and Gao, 2017) suggested that most Himalayan Cenozoic leucogranites are derived from fluid-absent melting of muscovite in metasedimentary source rocks. In the past 10 years, an increasing number of studies have documented that granites with a characteristic signature of high CaO, Sr, and Ba but low Rb/Sr ratios are more widespread than previously thought and require fluid-fluxed melting of metasedimentary sources as a dominant melting mechanism (Prince et al., 2001;Zhang et al., 2004;King et al., 2011;Guo and Wilson, 2012;Zeng et al., 2012;Gao and Zeng, 2014;Gao et al., 2017;Huang et al., 2017;Bartoli et al., 2019;Fan et al., 2021;Meng et al., 2021;Liu et al., 2022aLiu et al., , 2022b. In the Malashan-Gyirong area of southern Tibet, plutons, dikes, and veins of leucogranitic compositions are derived from fluidfluxed and fluid-absent melting of muscovite in metasedimentary sources (Gao and Zeng, 2014). ...
... The Eocene granites derived predominantly from melting of amphibolite could be generated under contraction and thickening tectonic setting (Hou et al., 2012;Liu et al., 2014;Zeng et al., 2011). The Miocene granites resulted from fluid-absent or fluid-fluxed melting of muscovite in metasedimentary sources during rapid exhumation (Harris and Massey, 1994;Patiño Douce and Harris, 1998;Knesel and Davidson, 2002;Yang et al., 2001;Aoya et al., 2005;Zhang et al., 2004;King et al., 2011). Furthermore, Gao and Zeng (2014) suggested that the fluid-fluxed melting of muscovite in metasedimentary sources was associated with tectonic transition from early N-S extension to latest E-W extension in the Himalayan orogen. ...
The geochemistry of granite is largely controlled by physical and chemical parameters that are closely linked to tectonic processes in evolving orogenic belts. Therefore, temporal changes in the geochemical compositions of granites could be used to infer critical shifts in tectonic processes. The Himalayan leucogranites are crustal anatexis products, providing a case to formulate petrogenetic models for granites and test tectonic models. From west to east, in the High Himalaya and the Tethyan Himalaya, two groups of leucogranites are derived from fluid-absent melting (Group A) and fluid-fluxed melting of muscovite (Group B), respectively. In the Cona and Mount Everest areas, Group B granites crystallized at 26−10 Ma, and Group A granites formed at 19−13 Ma. Group B granites have higher CaO, Sr, Ba, Zr, Hf, Th, Sr/Y, Zr/Hf, and Th/U, and lower Rb, Nb, Ta, U, Rb/Sr, and 87Sr/86Sr than those in Group A granites. These geochemical differences highlight the role of deep-origin fluids and the dissolution control of the accessory phases on the geochemical compositions in silicic magma systems. Field and microstructural observations show that E-W extension occurred synchronously with the granite intrusion derived from fluid-fluxed melting. Elevated heat flow accompanying the E-W extension could dehydrate hydrous minerals and release fluids from deep-seated crust (e.g., Lesser Himalayan Sequence). Such fluids could flux and melt the metasedimentary rocks within the High Himalaya and produce Group B granites. Together with literature data, from the Lhasa terrane to the Himalayan belt, E-W extensions in Tibet may have initiated as early as 26 Ma.
... Furthermore, the source nature can be constrained by U-Pb dating of relict zircon which is abundant in the Cenozoic Himalayan granites. A prominent age peak at ca. 490-460 Ma was found by large amounts of data from studies on Himalayan granites collected from a wide range of localities (e.g., King et al. 2011;Hopkinson et al. 2017;Gao et al. 2017Gao et al. , 2021Liu et al. 2022a). This is unexpected, since such a peak is absent in the HHS, the protoliths of which were suggested to mainly accumulate during Neoproterozoic to Cambrian time, and they are characterized by Proterozoic age peaks (e.g., Gehrels et al. 2011). ...
... This study focused on the Sakya gneiss dome in the central part of the Tethyan Himalaya (Fig. 1B), which is also called Mabja dome in the literature and covers an area of ca. 50 × 50 km (e.g., Zhang et al. 2004;Lee and Whitehouse 2007;King et al. 2011). Paleozoic granitic gneisses intruding Paleozoic schists and migmatites form the core of the dome, and occur in sheared contact with the Tethyan sediment cover, metamorphosed up to staurolite-kyanite grade. ...
... Both the core and cover are intruded by the Cenozoic granite bodies in several localities at Kuday, Wing, Kua, Lijun, Donggong, Gomdre, Kouwu, and Mabja. The Cenozoic granites are mainly two mica granites, and garnet is common in the Kuday granites but is absent in other intrusions while tourmaline is occasionally observed in the Mabja granites (Zhang et al. 2004;King et al. 2011). U-Pb dating on accessory minerals (zircon, monazite, and xenotime) yields emplacement ages of ca. ...
The Cenozoic Himalayan leucogranites are generally regarded as the representative S-type granites, derived from partial melting of (meta-)sedimentary rocks in the Higher Himalayan Sequences. This interpretation is challenged by the increasing finding of abundant relict zircons with Cambrian–Ordovician ages in the granites. These ages are lacking in the assumed (meta-)sedimentary sources but are close to the formation timing of early Paleozoic granites (presently as orthogneisses) in the Himalaya. Therefore, it is unclear how the early Paleozoic relict zircons were incorporated into the granites and what the real sources of the Cenozoic Himalayan leucogranites are. This study presents U–Pb ages, trace-element, and Lu–Hf isotope compositions of zircon from both the Cenozoic granites and their country rocks (Paleozoic orthogneisses) from Kuday in the Sakya dome, central Himalaya. Our results indicate that the autocryst zircons from the gneiss samples formed at 494–499 Ma and display obvious negative correlations in the Hf–Ti, Hf–Th/U, and Hf–Eu/Eu* binary plots. Their εHf(420 Ma) values have relatively restricted variations of −7.2 to −0.5. In contrast, the early Paleozoic relict zircons from granites form scattered and contrasting fields in these binary plots with largely varied U–Pb ages (ca. 410–520 Ma) and εHf(420 Ma) values of −35.4 to + 6.7. These observations suggest that the autocryst zircons from gneisses are a cogenetic population and their compositional variations are controlled by crystallization differentiation, whereas the relict zircons from granites were probably originated from sedimentary rocks in which detrital grains were weathered from a variety of protoliths. We argue that the early Paleozoic relict zircon population was not incorporated into the Cenozoic granites by assimilation of the orthogneissic country rocks. This is supported by whole-rock Nd–Hf isotope analyses, which yield εNd(t) and εHf(t) values of −12.6 ~ −12.5 and of −10.4, respectively, for granites and of −8.8 ~ −8.1 and of −5.9, respectively, for orthogneisses (all calculated at 20 Ma). Furthermore, our compiled whole-rock Sr–Nd isotope data indicate that the Cenozoic Himalayan granites differ from the Paleozoic orthogneisses but overlap with the Himalayan (meta-)sedimentary rocks. Phase equilibrium modeling demonstrates that the Paleozoic orthogneisses are relatively infertile due to their low fractions of hydrous minerals and thus low bulk water contents as compared with the metapelites assuming no free fluid is present. Therefore, although the contribution of the Paleozoic orthogneisses cannot be totally precluded, the observed evidence suggests that they are not the main source components of the Cenozoic Himalayan granites. It is speculated that Ordovician and later sediments which can receive the weathered clasts of the early Paleozoic granites can act as the unrecognized sources of the Cenozoic granites. However, more work is required to characterize these sediments before drawing firm conclusions on the sources of these granites.
... As such, these granites are ideal for investigating the origins of crustal anatectic melts using B and Mo isotopes. Cenozoic granites in the Himalaya exhibit marked heterogeneity in terms of their mineralogy and geochemistry, as well as Sr-Nd isotopes (Gao et al., 2017;Hou et al., 2012;King et al., 2011;Wu et al., 2020;Zeng et al., 2005Zeng et al., , 2011. The heterogeneity has been attributed to source variability, different types of crustal anatexis, variable degrees of partial melting, and extreme fractional crystallization (Deniel et al., 1987;Fan et al., 2021;Gao et al., 2017;Wu et al., 2020;Zeng et al., 2005). ...
The origins of Cenozoic granites in the Himalaya are key to understanding the evolution of the Himalayan orogen. However, it is unclear whether these granites represent primary melts, and the nature of their magma source is controversial. Here, we present a systematic element and Sr–Nd–B–Mo isotope study of Cenozoic granites from the Yardoi area in the eastern Tethyan Himalaya, China. These granites can be divided into two groups: mid‐Eocene porphyritic two‐mica granites with low SiO2 contents (65.9−69.6 wt.%) and adakitic geochemical signatures, and mid‐Eocene to Miocene equigranular granites with high SiO2 contents (71.6−75.5 wt.%). The high‐SiO2 granites (HSG) have similar Sr−Nd isotope compositions to the low‐SiO2 granites (LSG), but they have distinct δ¹¹B values of −19.4‰ to −11.4‰ and −10.6‰ to −6.89‰. This indicates that the two groups have different sources, with the LSG derived by partial melting dominantly of metamafic rocks at thickened lower crustal conditions, and the HSG generated by partial melting of the mid‐crust metasedimentary rocks with less enriched Nd isotope compositions. The δ98/95Mo of the LSG and HSG are highly variable with values of −0.68‰ to 0.12‰ and −1.13‰ to 0.46‰, respectively. δ¹¹B values of the HSG correlate positively with δ98/95Mo and Sr/Y values and correlate negatively with K2O, Rb, Zr, and Rb/Sr, reflecting the addition of external metamorphic fluids during anatexis of the metapelites. The B–Mo isotope data robustly suggest source‐controlled compositional diversity of the Himalayan granites, which could provide clues to the physical and geochemical responses during the evolution of a large orogen.
... Exhumation of the north Himalayan domes occurred mostly at 12 ± 4 Ma (e.g., King et al., 2011;) with a few a little older at 18-15 Ma . Coevally, grabens formed along the crest of the Himalaya that have eastwest directed extension and north-south striking normal faults. ...
