scholarly journals Exhumation of the ultrahigh-pressure Tso Morari unit in eastern Ladakh (NW Himalaya): A case study

Tectonics ◽  
2004 ◽  
Vol 23 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Julia de Sigoyer ◽  
Stéphane Guillot ◽  
Pierre Dick
Keyword(s):  
Ultrahigh Pressure ◽  
Nw Himalaya ◽  
Tso Morari

Fluids in coesite-bearing rocks of the Tso Morari Complex, NW Himalaya: evidence for entrapment during peak metamorphism and subsequent uplift

2009 ◽  
Vol 146 (6) ◽  
pp. 876-889 ◽  
Author(s):  
BARUN K. MUKHERJEE ◽  
HIMANSHU K. SACHAN
Keyword(s):  
High Salinity ◽  
Granulite Facies ◽  
Ultrahigh Pressure ◽  
Nw Himalaya ◽  
Rock Interaction ◽  
Low Salinity ◽  
Ultrahigh Pressure Metamorphism ◽  
Indian Lithosphere ◽  
External Sources ◽  
Tso Morari

AbstractFluid inclusions trapped in coesite-bearing rocks provide important information on the fluid phases present during ultrahigh-pressure metamorphism. The subduction-related coesite-bearing eclogites of the Tso Morari Complex, Himalaya, contain five major types of fluids identified by microthermometry and Raman spectroscopy. These are: (1) high-salinity brine, (2) N2, (3) CH4, (4) CO2and (5) low-salinity aqueous fluids. These fluids were trapped during both deep subduction and exhumation processes. The coesite-bearing rocks are inferred to have been buried to a depth of >120 km, where they experienced ultrahigh-pressure metamorphism. The fluid–rock interaction provides direct evidence for fluid derivation during a deep subduction process as demonstrated by silica–carbonate assemblages in eclogite. High salinity brine, N2and CH4inclusions are remnants of prograde and peak metamorphic fluids, whereas CO2and low-salinity aqueous fluids appear to have been trapped late, during uplift. The high-salinity brine was possibly derived from subducted ancient metasedimentary rocks, whereas the N2and CH4fluids were likely generated through chemical breakdown of NH3-bearing K minerals and graphite. Alternatively, CH4might have been formed by a mixed fluid that was released from calcareous sediments during subduction or supplied through subducted oceanic metabasic rocks. High density CO2is associated with matrix minerals formed during granulite-facies overprinting of the ultrahigh-pressure eclogite. During retrogression to amphibolite-facies conditions, low-salinity fluids were introduced from external sources, probably the enclosing gneisses. This source enhances salinity differences as compared to primary saline inclusions. The subducting Indian lithosphere produced brines prior to achieving maximal depths of >120 km, where fluids were instead dominated by gaseous phases. Subsequently, the Indian lithosphere released CO2-rich fluids during fast exhumation and was then infiltrated by the low-salinity aqueous fluids near the surface through external sources. Elemental modelling may improve quantitative understanding of the complexity of fluids and their reactions.

scholarly journals Feasibility of the Sar Technique on Quartz Sand of Terraces of NW Himalaya: A Case Study from Devprayag

2008 ◽  
Vol 31 (-1) ◽  
pp. 45-52 ◽  
Author(s):  
Manoj Jaiswal ◽  
Pradeep Srivastava ◽  
Jayant Tripathi ◽  
Rafique Islam
Keyword(s):  
Luminescence Intensity ◽  
Quartz Sand ◽  
Late Quaternary ◽  
Active Tectonics ◽  
Nw Himalaya ◽  
North West ◽  
North East ◽  
The North ◽  
Quartz Grains

Feasibility of the Sar Technique on Quartz Sand of Terraces of NW Himalaya: A Case Study from DevprayagOptically Stimulated Luminescence (OSL) dating technique based on the Single Aliquot Regenerative dose (SAR) protocol is being used increasingly as a means of establishing sediment burial age in the late Quaternary studies. Thermal transfer, low and changing luminescence sensitivity of quartz grains of young sedimentary belts of the New Zealand Alps and the north-east Himalaya poses problems in using SAR protocol. Records of active tectonics and signatures of palaeo-climate are preserved in the Quaternary - Holocene terrace sediments. Therefore, to unfold the history of successive tectonic and palaeo-climate events, robust chronological technique is needed. Palaeoflood deposits in NW Lesser Himalayan region receive quartz from the weathering of various rock types such as quartzite and phyllite in the Alaknanda Basin. A series of tests e.g. dose recovery, preheat plateau, thermal recuperation and change in sensitivity, were performed to check the suitability of quartz grains collected from the terrace sediment of Devprayag of the NW Himalaya, for OSL studies. Inferences were drawn regarding the source of the quartz grains on the basis of the geochemistry and luminescence intensity of the terrace sediment. The study shows that though quartz from the North West Himalaya are low in luminescence intensity but the reproducibility of De value makes the quartz sand suitable for SAR dating technique. Relation between luminescence intensity with CIA values help to predict the provenance of quartz sand. Tests show that the quartz from NW Himalaya is suitable for SAR protocol in OSL.

scholarly journals Eclogites and other high-pressure rocks in the Himalaya: a review

2018 ◽  
Vol 483 (1) ◽  
pp. 183-213 ◽  
Author(s):  
Patrick J. O'Brien
Keyword(s):  
High Pressure ◽  
Granulite Facies ◽  
Suture Zone ◽  
Indian Plate ◽  
Accretionary Wedge ◽  
Nw Himalaya ◽  
Magmatic Rocks ◽  
Namche Barwa ◽  
Tso Morari ◽  
South Tibet

AbstractHimalayan high-pressure metamorphic rocks are restricted to three environments: the suture zone; close to the suture zone; and (mostly) far (>100 km) from the suture zone. In the NW Himalaya and South Tibet, Cretaceous-age blueschists (glaucophane-, lawsonite- or carpholite-bearing schists) formed in the accretionary wedge of the subducting Neo-Tethys. Microdiamond and associated phases from suture-zone ophiolites (Luobusa and Nidar) are, however, unrelated to Himalayan subduction–collision processes. Deeply subducted and rapidly exhumed Indian Plate basement and cover rocks directly adjacent to the suture zone enclose eclogites of Eocene age, some coesite-bearing (Kaghan/Neelum and Tso Morari), formed from Permian Panjal Trap, continental-type, basaltic magmatic rocks. Eclogites with a granulite-facies overprint, yielding Oligocene–Miocene ages, occur in the anatectic cordierite ± sillimanite-grade Indian Plate mostly significantly south of the suture zone (Kharta/Ama Drime/Arun, north Sikkim and NW Bhutan) but also directly at the suture zone at Namche Barwa. The sequence carpholite-, coesite-, kyanite- and cordierite-bearing rocks of these different units demonstrates the transition from oceanic subduction to continental collision via continental subduction. The granulitized eclogites in anatectic gneisses preserve evidence of former thick crust as in other wide hot orogens, such as the European Variscides.

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