Query: himalayan magmatism

title: THE NEW ADVANCE IN THE STUDY ON HIMALAYAN MAGMATISM AND METALLOGENESIS IN CENTRAL WESTERN YUNNAN
abstract: The Himalayan in the central western part of Yunnan can be divided into 4 tectonic episodes. The magmatic intrusion of them indicates 2 thermal cycles and the high tide of volcanic eruption takes place after the magmatic intrusion. We first divided the Cenozoic endogenetic metallogenesis into 6 time series. The alkali rich porphyry is first divided into 6 superunits and 18 units according to rock assemblage, emplacement time and metallogenetic specialization and their characteristics are summarized in 7 aspects. The evolution las of alkali rich porphyry is correlated with those of other 4 magmatic rocks. In order to study the genetic relation of Jinding super large Pb Zn deposit to various magmatic rocks, the newest data of Pb isotope and inert gas are discussed and correlated in detail. We tentatively think that there is an important innate connection in the deep material source and formation process of them. The hydro thermal deposits in Jinding and Lanping basin are formed by a set of independent metallogenesis with a certain connection to the mantle and mantle crust mixture.

title: Source and mode of the Permian Panjal Trap magmatism: Evidence from zircon U Pb and Hf isotopes and trace element data from the Himalayan ultrahigh pressure rocks
abstract: We present an integrated study of LA ICP MS U Pb age, Hf isotopes, and trace element geochemistry of zircons from the Himalayan eclogites (mafic rocks) and their host gneisses (felsic rocks) from the Kaghan Valley in Pakistan in order to understand the source and mode of their magmatic protoliths and the effect of metamorphism. Zircons from the so called Group I (high pressure) eclogites yielded U Pb mean ages of 259 10 Ma (MSWD 0.74) whereas those of Group II (ultrahigh pressure) eclogites yielded 48 3 Ma (MSWD 0.71) In felsic gneisses the central or core domains of zircons yielded ages similar to those from Group I eclogites but zircon overgrowth domains yielded 47 1 Ma (MSWD 1.9) Trace element data suggest a magmatic origin for Group I derived (having Th/U ratios: 0.5) and metamorphic origin for Group II derived (Th/U 176 Hf/ 177 Hf isotopic ratios referred to as "E Hf (t)" of around 10 in Group I eclogites; 7 in Group II eclogites; and 8 in felsic gneisses zircons, respectively, thus indicate a juvenile mantle source for the protolith rocks (Panjal Traps) with almost no contribution from the ancient crustal material. The similar E Hf (t) values, identical protolith ages and trace element compositions of zircons in felsic (granites or rhyolites) and mafic (basalt and dolerite) rocks attest to a bimodal magmatism accounting for the Panjal Traps during the Permian. Later, during India Asia collision in Eocene times, both the felsic and mafic lithologies were subducted to mantle depths 90 km: coesite stable) and experienced ultrahigh pressure metamorphism before their final exhumation.

title: Early Paleozoic Magmatism in Himalayan Orogen: The Geochronological Study on Augen Gneisses from Gyirongand Nyalam Areas, Southern Tibet

title: The Research Progress of Magmatism and Mineralization of Himalayan in the Gandise Metallogenic Belt, Tibet

title: Reply to comment on "Interplay of deformation and magmatism in the Pangong Transpressional Zone, Eastern Ladakh, India: Implications for remobilization of the trans Himalayan magmatic arc and initiation of the Karakoram Fault"
abstract: In the eastern part of Ladakh, the right lateral Karakoram Fault Zone (KFZ) bifurcates into two strands called the Pangong Strand and the Tangtse Strand. These two strands bound a region called the Pangong Transpression Zone (PTZ) which consists of migmatitic dioritic gneiss, calc silicates and the Durbuk Pluton; a pluton of two mica leucogranite. Outcrop scale observations suggest pervasive migration of leucogranitic melt through the existing tectonic structures of the gneiss. Magnetic fabric from both the tectonized and undeformed parts of the Durbuk Pluton show parallelism with the tectonic fabric of the host gneiss, which, along with pervasive melt migration, indicates syn kinematic relationship between deformation along the KFZ, leucogranite magmatism and emplacement of the Durbuk Pluton. U Pb geochronology of zircons from the dioritic gneiss yields a crystallization age of 63.6 1.5 Ma and also shows younger zircon growth down to ~13 Ma, which suggest arc magmatism at ~65 Ma followed by partial melting and leucogranite magmatism in the KFZ till ~13 Ma. One two mica leucogranite sample from the Durbuk Pluton gives a crystallization age of 22.7 0.5 Ma. As the Durbuk Pluton is syn tectonic with deformation along KFZ, it is inferred that the KFZ initiated at least ~23 Ma ago.

title: Oligocene magmatism in the eastern margin of the east Himalayan syntaxis and its implication for the India Asia post collisional process
abstract: Post collisional high Sr/Y type magmatism in the southern Lhasa terrane extends 1500 km along the strike of the orogen. The origin and magma generation mechanism for these rocks remain controversial. We report a detailed study of such high Sr/Y type magmatism in the east Himalayan syntaxis, SE Tibet, and explain its significance for understanding post collisional geodynamical processes. The two mica granites from the Beibeng, Damu, Bolonggong and Bomi plutons emplaced along the eastern margin of the east Himalayan syntaxis represent a high K calc alkaline suite (SiO 2 67 75 wt. Al 2 O 3 13.3 15.8 wt. K 2 O/Na 2 O 0.7 1.9) An outstanding geochemical feature is that they have high Sr/Y ratios (19 88, mostly 30) coupled with low Y and HREE, indicating that they were derived from partial melting of thickened lower crustal materials. Sr Nd isotopic data show that the potential magma sources are the intermediate intrusive rocks related to the Jurassic Eocene Gangdese magmatism and basement metasedimentary rocks. The contribution of the latter source increases from south to north. The two mica granites from the Beibeng, Damu, Bolonggong and Bomi intrusions have magma crystallization ages of 29.9 27.5 Ma, 27.6 Ma, 27.1 26.5 Ma and 23.7 Ma, respectively. Our data show decreasing magma crystallization ages both from south to north along the eastern margin of the east Himalayan syntaxis and from east to west along the Gangdese belt. We suggest that such variations resulted from the diachronous breakoff of the subducted Indian continental slab. Beneath the east Himalayan syntaxis, the breakoff of the subducted Indian continental slab was initiated in the south and propagated towards north probably due to the thermal impact of a widening window opened by slab breakoff. Along the Gangdese belt, the breakoff of the subducted Indian continental slab commenced in east, and then propagated westwards.

title: Dextral transpression and late Eocene magmatism in the trans Himalayan Ladakh Batholith (North India) implications for tectono magmatic evolution of the Indo Eurasian collisional arc
abstract: The trans Himalayan Ladakh batholith is a result of arc magmatism caused by the northward subduction of the Tethyan oceanic lithosphere below the edge of the Eurasian plate. The batholith dominantly consists of calc alkaline I type granitoids which are ferromagnetic in nature with the presence of magnetite as the principal carrier of magnetic susceptibility. The mesoscopic and magnetic fabric are concordant and generally vary from WNW ESE to ENE WSW for different intrusions of ferromagnetic granites in different parts of the batholith. Strike of magnetic fabric is roughly parallel with the regional trend of the Ladakh batholith in the present study area and is orthogonal to the direction of India Eurasia collision. In Khardungla and Changla section, the magnetic fabric is distributed in a sigmoidal manner. It is inferred that this sigmoidal pattern is caused by shearing due to transpression induced by oblique convergence between the two plates. U Pb zircon geochronology of a rhyolite from the southern parts of the batholith gives a crystallization age of 71.7 0.6 Ma, coeval with ~68 Ma magmatism in the northern parts of the batholith. The central part of the batholith is characterized by S type two mica granites, which gives much younger age of magmatism at 35.5 0.5 Ma. The magnetic fabric of these two mica granites is at a high angle to the regional trend of the batholith. It is proposed that these two mica granites were emplaced well after the cessation of subduction and arc magmatism, along fractures that developed perpendicular to the regional strike of the batholith due to shearing.

title: Is the switch from I to S type magmatism in the Himalayan Orogen indicative of the collision of India and Eurasia?
abstract: The switch from I to S type magmatism in the Trans Himalayan Batholith is one of the criteria used to determine when India and Eurasia collided. We present new 238U/206Pb SHRIMP data from the Karakorum Batholith, NW India. Our results suggest that an I type hornblende biotite granodiorite was emplaced at 31.4 0.4 Ma and crosscut by S type granite dykes at 18.0 0.4 Ma. We interpret these data to indicate that volatile fluxed melting of a mantle wedge above an active subduction zone and/or decompression melting of sub arc asthenosphere was possible until at least 31 Ma. This interpretation uses the same rationale as previous workers have adopted to propose that the India Eurasia collision occurred between 57 Ma and 47 Ma. A review of published data provides further evidence of <50 Ma magmatism and Cu Au Mo porphyry deposit mineralisation north of the Himalayan range. These rocks would be interpreted to have formed in an arc setting in other parts of the world. However, most workers consider that <50 Ma magmatism and porphyry deposit formation in the Himalaya is unrelated to subduction of oceanic lithosphere and are instead considered to form owing to 'post collisional' processes. We argue that these interpretations have been based on an established model where the India Eurasia collision is deemed to occur at ca 50 Ma, instead of using the data to question and refine existing tectonic models.

title: "Dirty" subduction during the closure of Tethyan Ocean(s) evidence from K rich postcollisional magmatism within Alpine Himalayan belt

title: Late Permian mafic magmatism along the Tethyan Himalayan Belt,southern Tibet and tectonic implications
abstract: We report a new occurrence of Late Permian mafic magmatic rock near the Yardoi gneiss dome within the Tethyan Himalayan Belt,southern Tibet. This suite of diabase intruded into the fine grained sandstone and shale of the Tethyan sedimentary sequence and formed at 273. 0 2. 2 Ma SHRIMP zircon U Pb age) ,which indicates that the sedimentary rocks intruded by the diabase formed before Late Permian and not the Late Triassic as assigned by previous studies. This suite of diabase is characterized by (1) enrichment in LREE and depletion in HREE; 2) high contents of HFSE; 3) relatively high Sr 87 Sr 86 Sr( t) 0. 7063 0. 7078) and Nd( e Nd t) 1. 1 2. 4) isotope compositions,similar to those in the contemporaneous continental flood basalts and diabases in the western Tethyan Himalaya; and 4) positive e Hf t) +2. 5 +3. 9) values. Combined with literature data,out new results suggest that the Late Permian mafic magmatism,though distributed sporadically along the Tethyan Himalaya,is more widespread and signifies the rifting along the northern margin of the Gondwana continent and the initial opening of the Neo Tethyan Ocean.