Neoproterozoic bimodal magmatism in the eastern Himalayan orogen: Tectonic implications for the Rodinia supercontinent evolution

doi:10.1016/j.gr.2021.01.016

Gondwana Research

Volume 94, June 2021, Pages 87-105

https://doi.org/10.1016/j.gr.2021.01.016 Get rights and content

Highlights

•
Extensive Neoproterozoic magmatic belt in the eastern Himalayan orogen.
•
Partial melting of ancient lower crust with minor input of mantle components.
•
Andean-type orogeny along the northwestern margin of the Rodinia at ca. 820 Ma.

Abstract

Neoproterozoic magmatism associated with the assembly and configuration of the Rodinia supercontinent is widely distributed in the India-Himalayan terrane. However, its petrogenesis and tectonic settings remain controversial. This study provides new geochronological and geochemical data on the Neoproterozoic bimodal magmatism from the eastern Himalayan orogen. In situ zircon U single bond Pb dating revealed that the protoliths of amphibolites were emplaced at ca. 826 Ma and the granitic gneisses have crystallization ages of 825–820 Ma. The granitic gneisses exhibit geochemical features of A-type granites, with high initial (⁸⁷Sr/⁸⁶Sr)_i ratio (0.7182–0.7394), low whole-rock ε_Nd(t) (−8.4 to −6.6), and variable zircon ε_Hf(t) (−7.4 to +1.0) values. They were probably generated by partial melting of the ancient lower crust with minor input of mantle components. The amphibolite samples are enriched in light rare earth elements (LREEs) and depleted in heavy rare earth elements (HREEs), suggesting an arc affinity. They have relatively high initial (⁸⁷Sr/⁸⁶Sr)_i ratios (0.7113–0.7136), low whole-rock ε_Nd(t) (−1.1 to 1.4) and a wide range of zircon ε_Hf(t) (−4.1 to 8.3) values, indicating that the protoliths of amphibolites were likely generated by partial melting of an enriched subduction-modified continental lithospheric mantle. Their geochemical signatures are similar to typical back-arc basin basalts. The presence of coeval A-type granites and arc-related mafic rocks is probably due to the existence of a back-arc system. We argue that the Neoproterozoic bimodal magmatism is a product of back-arc extension initiated at an early stage, resulting from the rollback of the Mozambique Oceanic slab. Combined with previous studies on Neoproterozoic magmas from India and the Himalayas, we suggest that an extensive Neoproterozoic back-arc system may have existed along the northwestern margin of the Rodinia supercontinent. This theory supports a scenario of an Andean-type continental margin for the India-Himalayan terrane during the middle Neoproterozoic.

Graphical abstract

Introduction

The global Neoproterozoic magmatism is commonly related to the assembly, configuration, and breakup of the Rodinia supercontinent and has evoked geoscientific attention regarding its petrogenesis and tectonic settings (Heaman et al., 1992; Li et al., 1999, Li et al., 2002, Li et al., 2006, Li et al., 2008, Li et al., 2013; Wang et al., 2009, Wang et al., 2018; Bybee et al., 2010; Spencer et al., 2013; Cawood et al., 2018). The evidences of Neoproterozoic magmatism have been reported from several continental fragments, such as South China (e.g., Li et al., 1999, Li et al., 2002, Li et al., 2003, Li et al., 2008, Li et al., 2010; Cawood et al., 2013; Zhao et al., 2013; Liu et al., 2020), India (e.g., Bhushan, 2000; Gyani et al., 2001; Gregory et al., 2009; Santosh et al., 2012, Santosh et al., 2014, Santosh et al., 2017; Ashwal et al., 2013; He et al., 2016; Wang et al., 2018; Zhao et al., 2018; Yang et al., 2020), Seychelles (e.g., Torsvik et al., 2001; Tucker et al., 2001; Ashwal et al., 2002; Hammond et al., 2013), Madagascar (e.g., Nédélec et al., 1995, Nédélec et al., 2016; Handke et al., 1999; Bybee et al., 2010; Boger et al., 2014; Zhou et al., 2015), Lhasa (e.g., Zhang et al., 2012a, Zhang et al., 2012b; Hu et al., 2018a, Hu et al., 2018b, Hu et al., 2018c; Dong et al., 2020), Tarim (e.g., Xu et al., 2005, Xu et al., 2013; He et al., 2012; Zhang et al., 2012c, 2016; Wu et al., 2017; Wen et al., 2019), Australia (e.g., Michael et al., 1998; Li et al., 2006; Huang et al., 2015), Pakistan (e.g., Khan et al., 2012; Ahmad et al., 2013; Qasim et al., 2018), and Laurentia (e.g., Goodge and Vervoort, 2006; Goodge et al., 2017; Cawood and Pisarevsky, 2017). However, the paleogeographic settings of diffenent terranes are still controversial. This caused long debates about the petrogenesis and tectonic settings of Neoproterozoic magmatism from diffenent terranes. As has been stated in previous studies, most of the Neoproterozoic magmatic events are attributed to mantle plumes or a mantle superplume that caused the rifting and fragmentation of the Neoproterozoic Rodinia supercontinent (e.g., Heaman et al., 1992; Park et al., 1995; Shellnutt et al., 2004; Maruyama et al., 2007; Li et al., 1999, Li et al., 2002, Li et al., 2006, Li et al., 2008, Li et al., 2013; Cui et al., 2015; Lyu et al., 2017; Zhang et al., 2017a; Zhu et al., 2018). However, a few other studies have suggested that the Neoproterozoic magmas from northwestern India, Madagascar, Seychelles, and Tarim were formed in a continental arc setting, pointing to active Andean-type orogeny on the northwestern margin of the Rodinia supercontinent (e.g., Torsvik et al., 1996; Tucker et al., 2001; Rino et al., 2008; Gregory et al., 2009; Bybee et al., 2010; He et al., 2012; Tang et al., 2016; Ding and Zhang, 2016; Liao et al., 2017; Wu et al., 2017; Wang et al., 2018; Zhao et al., 2018). Although this debate has not been well resolved so far, there is no doubt that studies on the origin and geodynamics of Neoproterozoic magmas will contribute to our understanding of the Rodinia supercontinent evolution.

Thus far, only a few studies have focused on the Neoproterozoic granitoids from the eastern Himalayan orogeny (Ding and Zhang, 2016; Wang et al., 2017a), and no coeval mafic rocks have been reported elsewhere. Moreover, the origin and geodynamics of these Neoproterozoic granitoids remain controversial. Ding and Zhang (2016) proposed that these granitoids display arc geochemical features, indicating that an Andean-type orogen may have existed along the northwestern margin of the Rodinia supercontinent. In contrast, Wang et al. (2017a) suggested that these Neoproterozoic granitoids are derived from the melting of ancient crustal rocks, possibly due to the breakup of the Rodinia supercontinent associated with episodic plume events. This contradiction is attributed to the lack of coeval mafic rock constraints, limiting the comprehensive understanding of the Neoproterozoic magmas in the eastern Himalayan orogen. Herein, we present new geochronological and geochemical data for the Neoproterozoic bimodal magmatism from the eastern Himalayan orogen (Fig. 1). In addition, we reanalyzed previously published results and revisited the petrogenesis of the Neoproterozoic bimodal magmatic rocks in the eastern Himalayan orogen to construct a new geodynamic model, propose the formation mechanism of these Neoproterozoic bimodal magmas, and correlate them with the geological evolution of the Rodinia supercontinent. We anticipate that this study can provide key clues for Neoproterozoic tectonothermal evolution of the India-Himalayan terrane in the northwestern Rodinia supercontinent.

Section snippets

Geological setting

As one of the largest collisional orogens in Earth history, the Himalayan orogenic belt consists of three parallel east-west-striking tectonic units, including the Lesser Himalayan Sequence (LHS), Greater Himalayan Crystalline Sequence (GHS), and Tethys Himalayan Sequence (THS), separated by the Main Boundary Thrust (MBT), Main Central Thrust (MCT), and South Tibetan Detachment System (STDS), respectively (Fig. 1A).

The THS zone extends in an east-west direction for more than 1300 km and is

Whole rock major and trace elements

Five fresh amphibolite samples and eleven fresh granitic gneiss samples were collected from outcrops. All the samples were analyzed for major and trace elements at the Analytical Laboratory Beijing Research Institute of Uranium Geology. Major element analyses were completed using a Philips PW2404 XRF with a precision of less than ±1%. Trace elements were determined using a Finnigan MAT Element XR ICP-MS. The uncertainties of the ICP-MS analyses are estimated to be better than ±5% for most trace

Zircon UPb ages

The results of zircon U single bond Pb testing are presented in Supplementary Table S1. The zircons from sample CNDXCJ (amphibolite) are euhedral to subhedral and approximately 40–150-μm long and 35–100-μm wide, with length to width ratios of 2:1 to 1:1 (Fig. 4A). Most of the Th/U ratios (0.46–1.94) are >0.1, indicating magmatic crystallization (Wu and Zheng, 2004). It is noteworthy that Most of these zircons have no clear oscillatory zoning and show core–rim structure in Cathodoluminescence (CL) images (

Rock metamorphism and alteration

Both the granitic gneiss and amphibolite samples reveal low loss-on-ignition (LOI) values (0.29–1.06). However, the petrographic investigations indicate that though these rocks have undergone various degrees of metamorphism and alteration, they still preserved igneous textures. Thus, the alkali elements and LILEs may have been modified by the metamorphic and alteration processes (Verma, 1981; Hart and Staudigel, 1982). However, REEs, HFSEs, V, Cr, and Ni are considered immobile and are likely

Conclusions

The new data presented herein and combined with previous studies allow for a better understanding of the petrogenesis of the Neoproterozoic bimodal magmatism in the eastern Himalayan orogen. Our key conclusions are as follows:

(1)
The in situ zircon UPb dating reveal that the protoliths of amphibolites were emplaced at Ca. 826 Ma and the granitoids have crystallization ages of 825–820 Ma. An extensive Neoproterozoic magmatic rock belt likely existed in the eastern Himalayan orogeny.
(2)
The granitic

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This research was supported by National Natural Science Foundation of China (grant 41702080, 91955208), the National Key R&D Program of China (grants 2018YFC0604103, 2016YFC0600308) and the China Geological Survey (grant DD20190147). We are deeply grateful to the anonymous reviewers for constructive suggestions.

References (164)

I. Ahmad et al.
Isotopic ages for alkaline igneous rocks, including a 26Ma ignimbrite, from the Peshawar plain of northern Pakistan and their tectonic implications
J. Asian Earth Sci.
(2013)
E. Aldanmaz et al.
Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey
J. Volcanol. Geotherm. Res.
(2000)
N.T. Arndt
Archean komatiites
L. Ashwal et al.
Geochronology and geochemistry of Neoproterozoic Mt. Abu granitoids, NW India: regional correlation and implications for Rodinia paleogeography
Precambrian Res.
(2013)
S.K. Bhushan
Malani rhyolites - a review
Gondwana Res.
(2000)
S.D. Boger et al.
From passive margin to volcano–sedimentary forearc: the Tonian to Cryogenian evolution of the Anosyen Domain of southeastern Madagascar
Precambrian Res.
(2014)
G.M. Bybee et al.
New evidence for a volcanic arc on the estern margin of a rifting Rodinia from the ultramafic intrusions in the ndriamena region, north-Central Madagascar
Earth Planet. Sci. Lett.
(2010)
P.A. Cawood et al.
Laurentia-Baltica-Amazonia relations during Rodinia assembly
Precambrian Res.
(2017)
P.A. Cawood et al.
Reconstructing South China in Phanerozoic and Precambrian supercontinents
Earth-Sci. Rev.
(2018)
X. Cui et al.
Mid-Neoproterozoic diabase dykes from Xide in the western Yangtze Block, South China: New evidence for continental rifting related to the breakup of Rodinia supercontinent
Precambrian Res.
(2015)

H. de Wall et al.

Cryogenian transpression and granite intrusion along the western margin of Rodinia (Mt. Abu region): magnetic fabric and geochemical inferences on Neoproterozoic geodynamics of the NW Indian block

Tectonophysics

(2012)

D.J. DePaolo

Trace element and isotopic effects of combined wallrock assimilation and fractional crystallization

Earth Planet. Sci. Lett.

(1981)

H.X. Ding et al.

Neoproterozoic granitoids in the eastern Himalayan orogen and their tectonic implications

Precambrian Res.

(2016)

H.X. Ding et al.

Cambrian ultrapotassic rhyolites from the Lhasa terrane, South Tibet: evidence for Andean-type magmatism along the northern active margin of Gondwana

Gondwana Res.

(2015)

H. Ding et al.

Early Eocene (c. 50 Ma) collision of the Indian and Asian continents: Constraints from the North Himalayan metamorphic rocks, southeastern Tibet

Earth Planet. Sci. Lett.

(2016)

X. Dong et al.

Late Neoproterozoic thermal events in the northern Lhasa terrane, South Tibet: Zircon chronology and tectonic implications

J. Geodyn.

(2011)

M. D'Orazio et al.

Slab window-related magmatism from southernmost South America: the late Miocene mafic volcanics from the Estancia Glencross area (~52°S, Argentina–Chile)

Lithos

(2001)

G.N. Eby

The A-type granitoids: a review of their occurrence and chemical characteristics and speculations on their petrogenesis

Lithos

(1990)

J.J. Fan et al.

Features, provenance, and tectonic significance of Carboniferous-Permian glacial marine diamictites in the Southern Qiangtang-Baoshan block, Tibetan Plateau

Gondwana Res.

(2015)

C.M. Fisher

Guidelines for reporting zircon Hf isotopic data by LA-MC-ICPMS and potential pitfalls in the interpretation of these data

Chem. Geol.

(2014)

J.W. Goodge et al.

Origin of Mesoproterozoic A-type granites in Laurentia: Hf isotope evidence

Earth Planet. Sci. Lett.

(2006)

J.W. Goodge et al.

Proterozoic crustal evolution of central East Antarctica: Age and isotopic evidence from glacial igneous clasts, and links with Australia and Laurentia

Precambrian Res.

(2017)

Z.B. Gou et al.

Petrogenesis and tectonic implications of the Yadong leucogranites, southern Himalaya

Lithos

(2016)

L.C. Gregory et al.

Paleomagnetism and geochronology of the Malani Igneous Suite, Northwest India: Implications for the configuration of Rodinia and the assembly of Gondwana

Precambrian Res.

(2009)

K.C. Gyani et al.

Neoproterozoic Magmatism and Metamorphism in Northwestern Indian Shield: Implications of Rodinia-Gondwana Tectonics

Gondwana Res.

(2001)

J.O.S. Hammond et al.

The extent of continental crust beneath the Seychelles

Earth Planet. Sci. Lett.

(2013)

S.R. Hart et al.

The control of alkalies and uranium in seawater by ocean crust alteration

Earth Planet. Sci. Lett.

(1982)

Z.Y. He et al.

Neoproterozoic granulites from the northeastern margin of the Tarim Craton: Petrology, zircon U–Pb ages and implications for the Rodinia assembly

Precambrian Res.

(2012)

X.F. He et al.

Early to late Neoproterozoic magmatism and magma mixing–mingling in Sri Lanka: Implications for convergent margin processes during Gondwana assembly

Gondwana Res.

(2016)

L.M. Heaman et al.

Nature and timing of Franklin igneous events, Canada: implications for a late Proterozoic mantle plume and the breakup of Laurentia

J. Geol.

(1992)

P.Y. Hu et al.

Precambrian origin of the North Lhasa terrane, Tibetan Plateau: Constraint from early Cryogenian back-arc magmatism

Precambrian Res.

(2018)

P.Y. Hu et al.

Middle Neoproterozoic (ca. 760 Ma) arc and back-arc system in the North Lhasa terrane, Tibet, inferred from coeval N-MORB- and arc-type gabbros

Precambrian Res.

(2018)

P.Y. Hu et al.

Early Neoproterozoic (ca. 900 Ma) rift sedimentation and mafic magmatism in the North Lhasa Terrane, Tibet: Paleogeographic and tectonic implications

Lithos

(2018)

Q. Huang et al.

Neoproterozoic (ca. 820–830 Ma) mafic dykes at Olympic Dam, South Australia: Links with the Gairdner large Igneous Province

Precambrian Res.

(2015)

K.P. Jochum et al.

Nb-Th-La in komatiites and basalts: constraints on komatiite petrogenesis andmantle evolution

Earth Planet. Sci. Lett.

(1991)

J. Just et al.

Monazite CHIME/EPMA dating of Erinpura granitoid deformation: implications for Neoproterozoic tectonothermal evolution of NW India

Gondwana Res.

(2011)

T. Khan et al.

Nagarparker granites showing Rodinia remnants in the southeastern part of Pakistan

J. Asian Earth Sci.

(2012)

Z.X. Li et al.

The breakup of Rodinia: did it start with a mantle plume beneath South China? Earth Planet

Sci. Lett.

(1999)

Z.X. Li et al.

Geochronology of Neoproterozoic syn-rift magmatism in the Yangtze Craton, South China and correlations with other continents: evidence for a mantle superplume that broke up Rodinia

Precambrian Res.

(2003)

X.H. Li et al.

Geochemistry of the 755 Ma Mundine well dyke swarm, northwestern Australia: part of a Neoproterozoic mantle superplume beneath Rodinia?

Precambrian Res.

(2006)

Z.X. Li et al.

Assembly, configuration, and break-up history of Rodinia: a synthesis

Precambrian Res.

(2008)

X.H. Li et al.

Petrogenesis and tectonic significance of the 850 ma Gangbian alkaline complex in South China: evidence from in situ zircon U-Pb dating, Hf-O isotopes and whole-rock geochemistry

Lithos

(2010)

Z.X. Li et al.

Neoproterozoic glaciations in a revised global alaeogeography from the breakup of Rodinia to the assembly of Gondwanaland

Sediment. Geol.

(2013)

J. Lin et al.

Calibration and correction of LA-ICP-MS and LA-MC-ICP-MS analyses for element contents and isotopic ratios

Solid Earth Sci.

(2016)

Y.S. Liu et al.

In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard

Chem. Geol.

(2008)

Z.C. Liu et al.

Petrogenesis of the Ramba leucogranite in the Tethyan Himalaya and constraints on the channel flow model

Lithos

(2014)

Z. Liu et al.

Petrogenesis of the early cretaceous Laguila bimodal intrusive rocks from the Tethyan Himalaya: Implications for the break-up of Eastern Gondwana

Lithos

(2015)

Z.C. Liu et al.

Highly fractionated late Eocene (~ 35 Ma) leucogranite in the Xiaru Dome, Tethyan Himalaya, South Tibet

Lithos

(2016)

Z.C. Liu et al.

Leucogranite geochronological constraints on the termination of the South Tibetan Detachment in eastern Himalaya

Tectonophysics

(2017)

Z.C. Liu et al.

Mineralogical evidence for fractionation processes in the Himalayan leucogranites of the Ramba Dome, southern Tibet

Lithos

(2019)

Cited by (9)

Neoproterozoic back-arc and arc-type magmatisms in the Rutong and Shiquanhe region, west of Tibet: Tectonic implications for the early-stage evolution of the Bangong-Nujiang suture zone and North Lhasa terrane
2024, Precambrian Research
Due to limited exposure of the Precambrian rocks in the Tibetan Plateau, their affinities and evolutions are inadequately studied. Here we report the newly identified Neoproterozoic metabasites (including metagabbros and metadolerites) at the western end of the Bangong-Nujiang suture zone (BNSZ) and the west part of the North Lhasa terrane. The Rutong Dong (RTD) metagabbros and Shiquanhe Nan (SQN) metadolerites yield zircon U-Pb ages of 838 Ma and 748 Ma, respectively. The RTD metagabbros are tholeiitic and exhibit both MORB- and arc-like geochemical characteristics, and we consider these to have formed in a back-arc basin setting. Combined with positive zircon ε_Hf(t) (+6.3 to +13.8) and whole-rock ε_Nd(t) (+4.4 to +5.3) values, the geochemical features of the RTD metagabbros indicate that they originated from a depleted mantle source enriched by subduction-related components (e.g., Th and U). The SQN metadolerites are mainly of transitional character (between tholeiitic and calc-alkaline), as well as representing typical calc-alkaline basalts. Their arc-like geochemical characteristics, as well as low positive whole-rock ε_Nd(t) (+1.7 to +3.4), and positive zircon ε_Hf(t) (+4.3 to +5.9) values, indicate generation by partial melting of an enriched subduction components modified mantle in an arc-type setting. Based on previous research, we propose that the North Lhasa terrane likely separated from India at ca. 925–860 Ma by the opening of the Mozambique Ocean. As the subduction zones were active at ca. 838–730 Ma in this ocean, a series of subduction-related magmatic events occurred, that is recorded in this study of the Rutong-Shiquanhe region, and other parts of the BNSZ and North Lhasa terrane. Consequently, we suggest that the BNSZ not only preserves information of the Meso-Tethys but also retains geological records of the Neoproterozoic Mozambique Ocean.
Multi-episodes of pre-Cenozoic bimodal magmatism in the Himalaya in response to arc-back-arc settings
2023, Lithos
The Himalayan orogen preserves multi-episodes of pre-Cenozoic magmatic history, but remains a subject of debate for their tectonic settings, limiting a better understanding of the Himalaya litho-tectonic structure. This study demonstrates the protolith nature of granitic gneisses and garnet amphibolites collected from three areas (Kangmar, Cona, and Arun Valley) in the east-central Himalaya. Then we investigated the bulk-rock major and trace elements, Sr-Nd isotopes, zircon U-Pb ages, and Hf isotopes. The garnet amphibolites are classified into sub-alkaline basalt and show tholeiite affinity. Garnet amphibolites from the Kangmar and Cona areas show Paleozoic (512–450 Ma) and Neoproterozoic (803 ± 8 Ma) protolith ages, respectively. Geochemically, they display similar MORB-like trace element features and enrich in large ion lithophile elements (LILEs: Rb, Th, U, Sr, Pb) and Ta, Ti, and mantle-like Sr-Nd isotopes with initial ⁸⁷Sr/⁸⁶Sr of 0.667787–0.705088 and ε_Nd(t) of 2.9–5.0. The high Th/Yb and Ba/Th ratios and varied ε_Hf(t) (−22.3–11.0) indicate subduction-related material contributions. The geochemical affinity to MORB and slab contributions is associated with a back-arc basin setting. Besides, garnet amphibolites from Arun Valley yield a protolith age of 1869 ± 10 Ma and are divided into two groups. Group I exhibits enriched LREE patterns [(La/Yb)_N = 5.99–6.44] and shows wide ε_Nd(t) of −1.3 to 7.1, variable Th/Ta and Nb/La, and high Zr/Y ratios. These features suggest the protolith of Group I might be continental flood basalts. In comparison, Group II exhibits MORB-like REE patterns, enrichments of LILEs, and depletions of high field strength elements (HFSEs) similar to island arc basalt. Thus, the geochemical affinity to MORB and arc-like features indicates they are metamorphosed from back-arc basalts. As for the granitic gneisses, the Kangmar and Cona samples give a Paleozoic age range of 552–438 Ma, due to a protracted (∼110 Myr) magmatism. The Kangmar granitic gneisses were metamorphosed from arc-related I-type granites, by contrast, the Cona granitic gneisses belong to A-type granites formed in a back-arc setting. These Paleozoic granitic gneisses show similar ε_Hf(t) of −7.1–−2.5 and T_DM2 of 1229–1923 Ma, indicating they were derived from partial melting of Meso- to Paleoproterozoic crust. Furthermore, the Arun Valley granitic gneisses give an 1819 ± 6 Ma protolith age and show arc features with enriched LILEs and depleted HFSEs. The wide ε_Hf(t) of −5.3–13.2 indicates the varying degree of mantle contributions resulting from slab break-off or roll-back. Therefore, the Himalaya witnessed bimodal magmatism during Paleoproterozoic, Neoproterozoic, and Paleozoic related to Andean-type orogeny. The multi-episodes of Andean-type magmatism contribute to the formation of the Cenozoic Himalayan architecture.
The evolution of Kerguelen mantle plume and breakup of eastern Gondwana: New insights from multistage Cretaceous magmatism in the Tethyan Himalaya
2023, Gondwana Research
The relationship between the breakup of eastern Gondwana and Kerguelen mantle plume remains extremely controversial. The crucial conundrum is that when and where the Kerguelen mantle plume initially formed and its evolutionary history are unclear. In this paper, we report the oldest Cretaceous bimodal magmatism (144–140 Ma) associated with the Kerguelen mantle plume from the Comei large igneous province in the Tethyan Himalaya. The mafic rocks are dominated by oceanic island basalt (OIB)-like dykes with occasional normal mid-ocean ridge basalt (N-MORB)-like intrusions, while the felsic rocks show A-type granites affinities. Our results suggest that the > 140 Ma bimodal magmatism was clearly a response to early Kerguelen plume activity, and the Kerguelen plume initially formed underneath the Tethyan Himalaya but not the triple junction between Australia, Antarctica, and Greater India. We argue that the Cretaceous magmatism associated with the Kerguelen plume in the Tethyan Himalaya can be divided into three pulses of ca.141 Ma, ca.132 Ma, and ca.117 Ma, which correspond to vertical underplating, continuous ascent, and a southward migration process, respectively. Moreover, we propose that the multistage OIB-like magmas in the Tethyan Himalaya are mainly the products of interactions between the lower crust and mantle plume, while the contribution of the lithospheric mantle is negligible. This proposal implies that the lithosphere was significantly thinned before ca.141 Ma, and the Kerguelen plume had been incubating underneath the Tethyan Himalaya prior to this. Our findings suggest that the Kerguelen plume may not have been the trigger for the initial breakup of eastern Gondwana, but was complementary to the later complete breakup process. We also innovatively consider that the northward dragging and slab-pull forces caused by the Cretaceous intra-oceanic subduction of the Neo-Tethys Ocean may have played an active role in the evolution of the Kerguelen plume and the breakup of eastern Gondwana.
Long-lived magmatic evolution and mineralization resulted in formation of the giant Cuonadong Sn-W-Be polymetallic deposit, southern Tibet
2023, Ore Geology Reviews
The Cuonadong Sn-W-Be polymetallic deposit is the first Cenozoic leucogranite-related rare-metal deposit with giant metallogenic potential in the Himalayan orogen. However, the controlling factors for the supernormal enrichment of beryllium, tin and tungsten in this deposit remain vague. In this study, we carried out systematic geochronological, whole-rock geochemical, and Sr-Nd isotopic analysis for the Cuonadong leucogranites, as well as detailed ore-forming geochronological study for the rare-metal mineralization. The monazite U-Th-Pb, cassiterite U-Pb and muscovite Ar-Ar dating results, together with previously reported geochronological data, indicate that the major Cuonadong leucogranites (including, from old to young, the weakly-oriented two-mica granite, two-mica granite and the muscovite granite) were formed during ∼ 21–15 Ma, whereas the Sn-W-Be mineralization mainly occurred at ∼ 18–14 Ma. The Cuonadong leucogranites show strong peraluminous (A/CNK = 1.09–1.22) features, and have high SiO₂ (71.62–75.97 wt%) and Al₂O₃ (14.04–16.09 wt%) and low MgO (0.07–0.33 wt%), MnO (0.01–0.15 wt%) and total iron (Fe₂O₃^T = 0.36–1.01 wt%) contents, and are enriched in large ion lithophile elements (e.g., Rb, U, K, and Pb). These geochemical features, together with enriched Sr-Nd isotopes (εNd(t) = -15.7 to −11.7; (⁸⁷Sr/⁸⁶Sr)_i = 0.71957–0.76313), indicate that the Cuonadong leucogranites belong to S-type granite and were derived from muscovite-induced dehydration melting of metapelites of the Higher Himalayan Crystalline Sequence. Perceptible linear variations of some major elements (e.g., Na₂O, K₂O, MnO, Fe₂O₃^T, TiO₂ and A/CNK) with increasing Rb/Sr ratios suggest that these leucogranites experienced different degrees of evolution. Quantitative simulation calculations based on the whole-rock Rb, Sr, and Ba contents imply that the Cuonadong leucogranites experienced increasingly-strong fractional crystallization of plagioclase, K-feldspar and biotite from the weakly-oriented two-mica granite through the two-mica granite to the muscovite granite. Importantly, intense fractional crystallization leaded to notable enrichment of Sn, W and Be, although these elements are not obviously high in the relatively primitive magma for the Cuonadong leucogranites. Significantly, evident REE tetrad effects and deviation of twin-element pair ratios (e.g. K/Rb, K/Ba, Zr/Hf, Nb/Ta, and Y/Ho) from the chondritic values demonstrate that intense interaction between melts and volatile-rich aqueous fluids occurred during magmatic evolution. This implies that the Cuonadong leucogranites were derived from a volatile-rich magmatic system. The abundant volatiles probably facilitated occurrence of fractional crystallization and extended duration of this process through lowering the solidus and viscosity of the magma. Thus, we propose that the long-lived fractional crystallization (21–15 Ma) and rare-metal mineralization (18–14 Ma) collectively leaded to supernormal enrichment of Sn, W, and Be in the Cuonadong Sn-W-Be polymetallic deposit. In contrast, the enrichment of these rare-metal elements was insignificant during partial melting.
The long-lived partial melting of the Greater Himalayas in southern Tibet, constraints from the Miocene Gyirong anatectic pegmatite and its prospecting potential for rare element minerals
2023, China Geology
The Cenozoic Himalayan leucogranite-pegmatite belt has been a hotspot for rare metal exploration in recent years. To determine the genesis of the pegmatite in the Himalayan region and its relationship with the Greater Himalayan Crystalline Complex (GHC), the Gyirong pegmatite in southern Tibet was chosen for geochronological and geochemical studies. The dating analyses indicate that the U-Th-Pb ages of zircon, monazite, and xenotime exhibit large variations (38.6–16.1 Ma), with the weighted average value of the four youngest points is 16.5 ± 0.3 Ma, which indicates that the final stage of crystallization of the melt occurred in the Miocene. The age of the muscovite Ar-Ar inverse isochron is 15.2 ± 0.4 Ma, which is slightly later than the intrusion age, showing that a cooling process associated with rapid denudation occurred at 16–15 Ma. The ε_Hf(t) values of the Cenozoic anatectic zircons cluster between −12 and −9 with an average of −11.4. The Gyirong pegmatite shows high contents of Si, Al, and K, a high Al saturation index, and low contents of Na, Ca, Fe, Mn, P, Mg, and Ti. Overall, the Gyirong pegmatite is enriched in Rb, Cs, U, K, Th and Pb and depleted in Nb, Ta, Zr, Ti, Eu, Sr, and Ba. The samples show a high ⁸⁷Sr/⁸⁶Sr_{(16 Ma)} ratio of ca. 0.762 and a low ε_{Nd(16 Ma)} value of −16.0. The calculated average initial values of ²⁰⁸Pb/²⁰⁴Pb_{(16 Ma)}, ²⁰⁷Pb/²⁰⁴Pb_{(16 Ma)} and ²⁰⁶Pb/²⁰⁴Pb_{(16 Ma)} of the whole rock are 39.72, 15.79 and 19.56, respectively. The Sr-Nd-Pb-Hf isotopic characteristics of the Gyirong pegmatite are consistent with those of the GHC. This study concludes that the Gyirong pegmatite represents a typical crustal–derived anatectic pegmatite with low metallogenic potential for rare metals. The Gyirong pegmatite records the long–term metamorphism and partial melting process of the GHC, and reflects the crustal thickening caused by thrust compression at 39–29 Ma and the crustal thinning induced by extensional decompression during 28–15 Ma.
©2023 China Geology Editorial Office.
Himalayan leucogranites: A review of geochemical and isotopic characteristics, timing of formation, genesis, and rare metal mineralization
2022, Earth-Science Reviews
Citation Excerpt :
The Himalayas are bordered from east to west by the syntaxial massifs—the Namche Barwa massif in the east (Eastern Himalayan Syntaxis) and the Nanga Parbat massif in the west (Western Himalayan Syntaxis) (Guevara et al., 2022). Multiple stages of magmatism are recognized from the available data in the Himalayan orogenic belt: Paleoproterozoic (1900–1700 Ma; Imayama et al., 2019), Neoproterozoic (1000–800 Ma; Zhang et al., 2021), early Paleozoic (520–460 Ma; Zhang et al., 2019a), Permian (290–260 Ma; Tian et al., 2021), late Triassic (240–210 Ma; Huang et al., 2018), late Jurassic–early Cretaceous (150–120 Ma; Chen et al., 2021a) and Cenozoic (45–1 Ma; Burg and Bouilhol, 2019). Among these, the magmatic rocks emplaced during the Proterozoic and early Paleozoic underwent Cenozoic intermediate- to high-grade metamorphism to form orthogneiss and are mainly exposed in the LHS and GHC.
As prototypes of crust-derived remelted S-type granite, Himalayan leucogranites have considerable relevance in crustal evolution and associated metallogeny. However, given their highly differentiated character, the petrogenesis of these rocks has remained controversial. This study reviews the geochemical and isotopic data from >2000 samples of Himalayan Cenozoic granitoids to evaluate their genesis. The Himalayan leucogranites include two major belts: the northern zone occurs in the Tethyan Himalayas and gneiss domes, and the southern zone is exposed mainly at the top of the Higher Himalayas. The ages of these rocks show a southward younging trend from 49 Ma to 1 Ma. The main rock types are two-mica granites and garnet-tourmaline-bearing muscovite granites, whereas Eocene and Miocene intermediate-mafic and adakitic rocks are developed mainly in the northern belt. The leucogranites originated from incongruent disequilibrium partial melting of the Greater Himalayan Crystalline Complex and underwent a high degree of differentiation and fractional crystallization. The rocks are strongly peraluminous and characterized by high Si, K, and Na; low Ca, Fe, Mg, Ti, and Mn; and low rare earth elements with obvious tetrad effects and negative Eu anomalies. A more striking feature of these granites is their high Rb/Sr and Y/Ho values and low Th/U, Nb/Ta, Zr/Hf, and K/Rb values. The Sr–Nd–Pb–Hf isotopes indicate that the proportion of older crustal material in the magmatic source area gradually increased from the Eocene to the Pliocene. The Cenozoic magmatic activity can be divided into five stages—49-40 Ma, 39–29 Ma, 28–15 Ma, 14–7 Ma, and 6–0.7 Ma—and their geotectonic settings are related to the break-off of the Neo-Tethyan oceanic plate, low-angle underthrusting of the Indian continental lithosphere, break-off or rollback of the Indian plate, tearing of the Indian lithospheric slab or delamination of the lithospheric mantle, and rapid extrusion and uplift of the Eastern and Western Himalayan Syntaxis resulting from flat subduction of the Indian continent, respectively. Stream sediment geochemical data from previous work show high positive anomalies for some rare metals in the Himalayas. The average contents of Li, Be, Sn, Ta and Cs in pegmatite are 2466 ppm, 93 ppm, 29 ppm, 14 ppm and 61 ppm, respectively. All these elements have enrichment coefficients higher than 10 compared to the upper continental crust. Recent progress in ore prospecting shows that the Himalayan Cenozoic leucogranite is emerging as a new world-class rare metal metallogenic belt.

View all citing articles on Scopus

View full text

Neoproterozoic bimodal magmatism in the eastern Himalayan orogen: Tectonic implications for the Rodinia supercontinent evolution

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Geological setting

Whole rock major and trace elements

Zircon UPb ages

Rock metamorphism and alteration

Conclusions

Declaration of Competing Interest

Acknowledgements

J. Asian Earth Sci.

J. Volcanol. Geotherm. Res.

Precambrian Res.

Gondwana Res.

Precambrian Res.

Earth Planet. Sci. Lett.

Precambrian Res.

Earth-Sci. Rev.

Precambrian Res.

Tectonophysics

Earth Planet. Sci. Lett.

Precambrian Res.

Gondwana Res.

Earth Planet. Sci. Lett.

J. Geodyn.

Lithos

Lithos

Gondwana Res.

Chem. Geol.

Earth Planet. Sci. Lett.

Precambrian Res.

Lithos

Precambrian Res.

Gondwana Res.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Precambrian Res.

Gondwana Res.

J. Geol.

Precambrian Res.

Precambrian Res.

Lithos

Precambrian Res.

Earth Planet. Sci. Lett.

Gondwana Res.

J. Asian Earth Sci.

Sci. Lett.

Precambrian Res.

Precambrian Res.

Precambrian Res.

Lithos

Sediment. Geol.

Solid Earth Sci.

Chem. Geol.

Lithos

Lithos

Lithos

Tectonophysics

Lithos