Tectono-metamorphic evolution of the far-Eastern Nepal Himalaya

Rai, Santa M; Sakai, Harutaka; Upreti, B. N.; Takigami, Yutaka; Ghimire, Suresh Kumar; Koirala, Dibya Raj; Gautam, Tej P; Sonyok, Desh R; Poudel, Chandra P

doi:10.3126/hjs.v2i4.914

Cited by 1 publication

(6 citation statements)

References 1 publication

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“…The gneisses of the upper horizon of the Barun Gneiss and all gneisses of the Namche Migmatites show granulite-high amphibolite facies mineral assemblages of sillimanite-garnet-biotite-potash feldspar-plagioclase-quartz, without muscovite and kyanite. Mineral assemblages of the Rongbuk Formation are generally similar to those found in the Namche Migmatites, but sillimanite is fibrolite and muscovite becomes common in gneisses occurring in the upper horizon (Rai et al, 2010). Thus, the metamorphic grade of the HHCS seems to decrease both towards the bottom and the top of the rock units.…”

Section: Metamorphism Migmatization and Granitic Intrusionsmentioning

confidence: 62%

“…In the Everest region including the study area, the North Col Formation (NCF) and Yellow Band had undergone upper greenschist facies to greenschist facies metamorphism, but the overlying Jolmo Lungma Formation (JLF) reached only to a lower greenschist facies (Sakai et al, 2005;Goscombe et al, 2006;Rai et al, 2010). The metamorphism of the Yellow Band could either be related to the thrust movement which caused of the Eo-Himalayan metamorphism mentioned below, and /or that of the Miocene STDS movement.…”

Section: Metamorphism Migmatization and Granitic Intrusionsmentioning

confidence: 98%

“…2), the Higher Himalayan Zone occupies most of the area whereas only a small part is covered by the Lesser Himalayan Zone to the south, and just a small area to the north is occupied by the Tibetan-Tethys Zone (Lombardo et al, 1993;Schelling, 1999;Searle et al, 2003;Rai et al, 2010;. The nomenclature of geologic units, general geology, petrography and metamorphism of the present area are given in Rai et al (2010), to which the description below generally follows.…”

Section: Geology Of the Everest Areamentioning

confidence: 99%

“…In the study area, The HHCS is represented by three rock units (from bottom to top) -the Barun Gneiss, the Namche Migmatites, and the Rongbuk Formation. Rai et al (2010) pointed out that the Barun Gneiss could be correlated with the Formation I of the central Nepal, a part of the Namche Migmatites with the Formation II, and the augen gneiss unit occurring in the upper part of the Rongbuk Formation with the Formation III of Le Fort (1975).…”

Section: The Higher Himalayan Crystalline Sequence (Hhcs)mentioning

confidence: 99%

“…Rocks of the LHS below the MCT suffered greenschist to lower amphibolite facies metamorphism with the increasing temperature conditions towards north (Rai et al, 2010), i.e., structurally and stratigraphically upward. The rocks of the LHS are mainly composed of garnet-chlorite-muscovite phyllite and chlorite-muscovite phyllite in the lowest horizon (Kuncha Formation), highly sheared chlorite biotite orthogneiss in the middle (Melung-Salleri Augen Gneiss), and two mica garnet schist, two mica staurolite garnet schist and two mica garnet gneiss in the uppermost horizon (Gudel Phyllite).…”

Section: Metamorphism Migmatization and Granitic Intrusionsmentioning

confidence: 99%

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Early Paleozoic zircon ages of the Higher Himalayan Gneisses of the Everest region and their Pan-African/Proto-Himalayan orogenic signature

Yoshida

Gehrels

Upreti

et al. 2019

Journal of Nepal Geological Society

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The U-Pb analysis of zircons from two independent leucosome bodies belonging to the paragneiss of the Higher Himalayan Crystallines Sequence (HHCS) in the Everest region of eastern Nepal Himalaya was carried out using laser ablation-multi collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) at the University of Arizona, Tucson, USA. The analysis of zircons from sample 07EVT3 forms a discordia with upper and lower intercepts at 478±25 and 21.5±4.1 Ma with concordant ages of 488.5±9.2 and 20.9±0.9 Ma for cores and rims, respectively. Similarly, the analysis of zircons from sample U1206 forms a discordia with upper and lower intercepts at 515±20 and 34.8±2.7 Ma, and provides concordant ages of 463.9±10.9 and 24.6±0.6 Ma for cores and rims, respectively. No inherited zircon grains with older ages were found indicating that almost all these zircons must have formed along with the leucotomies during the ca. 500 Ma metamorphism of the protoliths. The high U/Th ratio, i.e. average 11.0 for zircons from sample 07EVT3 and 253.6 for sample U1206 also support a metamorphic origin of the zircons. The occurrences of zircons in the ca. 500Ma leucosomes in the HHCS strongly points that rocks in the Himalayan area had undergone to a high-grade metamorphism during the late Pan-African time. We call this metamorphism as the Proto himalayan metamorphism. More studies along this line will help to better understand and constrain the Pan-African orogenic history of the Proto-Himalayan Orogen within the Peri-Gondwana Orogenicterrains.

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Section: Metamorphism Migmatization and Granitic Intrusionsmentioning

confidence: 62%

Section: Metamorphism Migmatization and Granitic Intrusionsmentioning

confidence: 98%