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PALEOMAGNETIC STUDY OF IGNEOUS ROCKS OF GUPIS—SHAMRAN AREA,KOHISTAN ARC, PAKISTAN,NW HIMALAYA

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地学前缘 2000年第S1期7卷 120-121页

作者： Mirza Naseer Ahmad, Yoshiki Fujiwara, lalu Prasad paudel[WT5,5”BX](Department of Earth and Planetary Sciences, Graduate School of Sciences, Hokkaido University Sapporo, Japan)

Kohistan Sequence has been considered as island arc formed during the subduction of oceanic lithosphere at the leading edge of northward moving Indian continent.. Sedimentary sequences indicate that formation of the intra\|oceanic Kohistan arc began in early Cretaceous time. The isotopic data demonstrate the involvement of enriched, DUPAL type mantle, suggesting that Kohistan arc was formed at or south of the present equator (Khan et al., 1997). The Intra oceanic phase of Kohistan lasted until sometime between 102 and 85 Ma, when Kohistan collided with Asia. From this time until collision with India about 50 Ma ago, Kohistan existed as Andean\|type margin. This paleomagnetic study is from the volcanic and plutonic rocks exposed in Gupis\|Shamran area (west of Gilgit) in northern part of the Kohistan arc. According to geochronological data these rocks were formed 61～55Ma ago (Treloar et al., 1989), when Kohistan was existing as Andean\|type margin. Seven to nine samples were collected from nine sites of Shamran volcanics (58±1)Ma and from five sites of Pingal, Gupis, and Yasin plutons (Ar\|Ar hornblende ages ranges from 61～52Ma). On the basis of one Rb\|Sr age of (59±2)Ma from these plutons, the above\|mentioned Ar/Ar ages may be regarded as reasonable intrusion ages of these plutons (Searle, 1991).

关键词： Kohistan paleomagnetism tectonics igneous rock Pakis tan

POLYPHASE METAMORPHISM AND INVERTED THERMAL GRADIENT IN THE LESSER HIMALAYA OF CENTRAL NEPAL: CONSTRAINTS FROM WHITE MICA COMPOSITIONS

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地学前缘 2000年第S1期7卷 51-52页

作者： lalu Prasad paudel 1,2 , Kazunori Arita 1[WT5,5”BX](1 Department of Earth and Planetary Sciences, Graduate School of Science, Hokkaido University, Kita 10, Nishi 8, Sapporo 060\|0810, Japan 2 Central Department of Geology, Tribhuvan University

The Lesser Himalaya in central Nepal consists of greenschist\|facies metasedimentary rocks, which are overthrust by the amphibolite\|facies rocks of the Higher Himalaya along the Upper Main Central Thrust (UMCT). Despite a number of works on metamorphism of the MCT zone and the Higher Himalaya, the low\|grade metamorphic rocks to the south of the MCT zone have not been studied *** the present study, an attempt was made to constrain the metamorphic events and thermal structure of the whole Lesser Himalaya by means of white mica (Ms) compositions. About 600Ms grains in 48 metapelitic samples from the Lesser Himalaya were analysed by the EPMA. Compositional zoning in individual Ms grains was checked by means of X\|ray compositional mapping. There exist wide intersample, intrasample and within grain compositional variations in Ms in the samples from the Lesser Himalaya. Sheared Ms phenocrysts in pegmatites and gneisses have compositions very close to that of the ideal muscovite. Detrital Ms show wide variation in phengite content, most of which are poor in phengite content, and are most probably derived from older higher\|grade metamorphic rocks.

关键词： Lesser Himalaya polymetamorphism inverted metamorphism white mica composition

Landslide susceptibility assessment at Kathmandu Kyirong Highway Corridor in pre-quake, co-seismic and post-quake situations

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Journal of Mountain Science 2020年第11期17卷 3162-3162页

作者： Susmita Dhakal Peng Cui Li-jun Su Qiang Zou Jian-qiang Zhang Susmita Dhakal Peng Cui Li-jun Su Susmita Dhakal Peng Cui Li-jun Su Li-jun Su Olga Mavrouli lalu paudel Nirusha Shrestha Institute of Mountain Hazard and Environment Chinese Academy of Sciences Chengdu 610041 China University of Chinese Academy of Sciences Beijing 100049 China Central Department of Environmental Science Tribhuvan University Kathmandu 44613 Nepal CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101 China China-Pakistan joint Research Center on Earth Sciences Islamabad 45320 Pakistan Faculty of Geo-information Science and Earth Observation University of Twente Enschede 7500 AE The Netherlands Central Department of Geology Tribhuvan University Kathmandu 44613 Nepal

Susmita DHAKAL1,2,3 http://***/oooo-o002-3o25-55o1;e-mail:***@*** CUI Peng1,2,4*http://0rcid.0rg/0000-0002-3973-5966;-e-mail:pengcui@*** S U L i-ju n 1,2,4,5 http://0rcid.0rg/0000-0001-9972-4698;e-mail:sulijun1976@*** Olga MAVROULI6 http://0rcid.0rg/0000-0003-1909-6113;e-mail:***@*** ZOU Qiang1 http://0rcid.0rg/0000-0003-0029-8532;e-mail:zouqiang@*** ZHANG Jian-qiang1 https://0rcid.0rg/0000-0003-3908-1082;e-mail:zhangjq@*** lalu paudel7^https://0rcid.0rg/0000-0003-4615-055X;e-mail:lalupaudel67@*** Nirusha SHRESTHA^11 http://0rcid.0rg/0000-0001-6959-3076;e-mail:shresthanirusha2@***.

关键词： quake seismic Corridor

MAIN CENTRAL THRUST ZONE IN THE KATHMANDU AREA, CENTRAL NEPAL, AND ITS TECTONIC SIGNIFICANCE

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地学前缘 2000年第S1期7卷 46-47页

作者： Kazunori Arita 1, Akira Takasu 2, Megh Raj Dhital 3, Kamal Raj Regmi 1,3 , lalu Prasad paudel 3[WT5,5”BX](1 Division of Earth and Planetary Sciences, Graduate School of Science, Hokkaido University, Kita 10 Nishi 8, Kita\|ku, Sapporo 060\|08

The Himalaya, a fold\|and\|thrust belt in the northern margin of the Indian continent, is characterized by thrust tectoncis (Schelling and Arita, 1991). It consists mainly of three thrust\|bounded lithotectonic units: from south to north the Sub\|Himalayan imbricate zone, the Lesser Himalayan thrust package (LH) and the Higher Himalayan thrust sheet (HH) with the overlying Tethys Himalayan sequence. These units are separated by a series of propagated thrusts, i.e. from south to north the Himalayan Frontal Fault (HFF), Main Boundary Thrust (MBT) and Main Central Thrust (MCT). These thrusts are splays off of an underlying mid\|crustal subhorizontal d$B;D(Jollement (Main Detachmen Trust or Main Himalayan Thrust), and were propagated southward with time. Among these thrusts the MCT is most important intracrustal thrust in considering the geological evolution of the Himalaya, and is controversial regarding its location and nature. In western and eastern Nepal the Higher Himalayan Crystalline sheet is thrust over the Lesser Himalayan rocks along the MCT. In the Kathmandu area of central Nepal also the high\|grade rocks of the HH with the overlying Tethyan sediments covers southward the Lesser Himalayan rocks, and form the Kathmandu nappe. In the north of the Kathmandu nappe the Higher Himalayan crystallines are skirted by the Main Central Thrust zone (MCT zone) which consists of green and black phyllites with sporadic garnet snow\|ball garnet and calcareous schist associated with characteristic mylonitic augen gneiss. The southern margin of the nappe is bounded by the Mahabharat Thrust (MT: Stoecklin, 1990) with a narrow zone of the LH which is cut by the MBT. But the relationship of the MCT in the north and the MT in the south is disputable and important (Arita et al., 1997: Rai et al., 1998: Upreti and Le Fort, 1999), and in the margin of the Kathmandu nappe the MCT zone has not been confirmed.

关键词： main central thrust zone central Nepal tectonic significance