A P–T–t–D discontinuity in east-central Nepal: Implications for the evolution of the Himalayan mid-crust

Larson, Kyle P.; Gervais, Félix; Kellett, Dawn A.

doi:10.1016/j.lithos.2013.08.012

Cited by 82 publications

(145 citation statements)

References 79 publications

Supporting

Mentioning

128

Contrasting

Order By: Relevance

“…Other studies have recorded monazite ages decreasing with depth below major thrust zones, both in the MCT zone, where monazite ages generally span between ∼21 and 11 Ma throughout the central to eastern Himalaya (Bollinger and Janots, 2006;Catlos et al, 2004Catlos et al, , 2001Harrison et al, 1997;Kohn et al, 2001;Larson and Cottle, 2014;Larson et al, 2013;McQuarrie et al, 2014), and the Canadian Cordillera (Crowley and Parrish, 1999;Gibson et al, 1999). Monazite ages collected from this study are therefore in agreement with the age range yielded from previous studies.…”

Section: Metamorphic Evolution Of the Mct Zonesupporting

confidence: 91%

Developing an inverted Barrovian sequence; insights from monazite petrochronology

Mottram

Warren

Regis

et al. 2014

Earth and Planetary Science Letters

146

141

View full text Add to dashboard Cite

Editor: T.M. Harrison Keywords: inverted metamorphism ductile thrusting petrochronology monazite geochronologyIn the Himalayan region of Sikkim, the well-developed inverted metamorphic sequence of the Main Central Thrust (MCT) zone is folded, thus exposing several transects through the structure that reached similar metamorphic grades at different times. In-situ LA-ICP-MS U-Th-Pb monazite ages, linked to pressure-temperature conditions via trace-element reaction fingerprints, allow key aspects of the evolution of the thrust zone to be understood for the first time. The ages show that peak metamorphic conditions were reached earliest in the structurally highest part of the inverted metamorphic sequence, in the Greater Himalayan Sequence (GHS) in the hanging wall of the MCT. Monazite in this unit grew over a prolonged period between ∼37 and 16 Ma in the southerly leading-edge of the thrust zone and between ∼37 and 14.5 Ma in the northern rear-edge of the thrust zone, at peak metamorphic conditions of ∼790 • C and 10 kbar. Monazite ages in Lesser Himalayan Sequence (LHS) footwall rocks show that identical metamorphic conditions were reached ∼4-6 Ma apart along the ∼60 km separating samples along the MCT transport direction. Upper LHS footwall rocks reached peak metamorphic conditions of ∼655 • C and 9 kbar between ∼21 and 16 Ma in the more southerly-exposed transect and ∼14.5-12 Ma in the northern transect. Similarly, lower LHS footwall rocks reached peak metamorphic conditions of ∼580 • C and 8.5 kbar at ∼16 Ma in the south, and 9-10 Ma in the north. In the southern transect, the timing of partial melting in the GHS hanging wall (∼23-19.5 Ma) overlaps with the timing of prograde metamorphism (∼21 Ma) in the LHS footwall, confirming that the hanging wall may have provided the heat necessary for the metamorphism of the footwall. Overall, the data provide robust evidence for progressively downwards-penetrating deformation and accretion of original LHS footwall material to the GHS hanging wall over a period of ∼5 Ma. These processes appear to have occurred several times during the prolonged ductile evolution of the thrust. The preserved inverted metamorphic sequence therefore documents the formation of sequential 'paleothrusts' through time, cutting down from the original locus of MCT movement at the LHS-GHS protolith boundary and forming at successively lower pressure and temperature conditions. The petrochronologic methods applied here constrain a complex temporal and thermal deformation history, and demonstrate that inverted metamorphic sequences can preserve a rich record of the duration of progressive ductile thrusting.

show abstract

Section: Metamorphic Evolution Of the Mct Zonesupporting

confidence: 91%

Developing an inverted Barrovian sequence; insights from monazite petrochronology

Mottram

Warren

Regis

et al. 2014

Earth and Planetary Science Letters

146

141

View full text Add to dashboard Cite

show abstract

“…c. 22-15 Ma in Larson et al, 2013;17-13 Ma in Montomoli et al, 2013). This means that kyanite in the MCT zone grew at different times.…”

Section: Tectonic Implicationsmentioning

confidence: 95%

“…Carosi et al, 2007Carosi et al, , 2010Corrie and Kohn, 2011;Imayama et al, 2012;Larson et al, 2013;Montomoli et al, 2013;see Montomoli et al, 2014 for a review) have shown that the GHS has a much more complex crustal architecture compared to simple models where a single coherent tectonic unit is bounded by only two tectonic discontinuities with opposite sense of shear. These recent findings are also compatible with diachronic melting within the GHS (Corrie and Kohn, 2011;Imayama et al, 2012;Kohn et al, 2005;Rubatto et al, 2013).…”

Section: Tectonic Implicationsmentioning

confidence: 99%

Pressure–temperature–time–deformation path of kyanite-bearing migmatitic paragneiss in the Kali Gandaki valley (Central Nepal): Investigation of Late Eocene–Early Oligocene melting processes

Iaccarino

Montomoli

Carosi

et al. 2015

Lithos

107

119

View full text Add to dashboard Cite

Kyanite-bearing migmatitic paragneiss of the lower Greater Himalayan Sequence (GHS) in the Kali Gandaki transect (Central Himalaya) was investigated. In spite of the intense shearing, it was still possible to obtain many fundamental information for understanding the processes active during orogenesis. Using a multidis- ciplinary approach, including careful meso- and microstructural observations, pseudosection modelling (with PERPLE_X), trace element thermobarometry and in situ monazite U–Th–Pb geochronology, we constrained the pressure–temperature–time–deformation path of the studied rock, located in a structural key position. The migmatitic gneiss has experienced protracted prograde metamorphism after the India–Asia colli- sion (50–55 Ma) from ~43 Ma to 28 Ma. During the late phase (36–28 Ma) of this metamorphism, the gneiss underwent high-pressure melting at “near peak” conditions (710–720 °C/1.0–1.1 GPa) leading to kyanite- bearing leucosome formation. In the time span of 25–18 Ma, the rock experienced decompression and cooling associated with pervasive shearing reaching P–T conditions of 650–670 °C and 0.7–0.8 GPa, near the sillimanite–kyanite transition. This time span is somewhat older than previously reported for this event in the study area. During this stage, additional, but very little melt was produced. Taking the migmatitic gneiss as representative of the GHS, these data demonstrate that this unit underwent crustal melting at about 1 GPa in the Eocene–Early Oligocene, well before the widely accepted Miocene decompressional melting related to its extrusion. In general, kyanite-bearing migmatite, as reported here, could be linked to the production of the high-Ca granitic melts found along the Himalayan belt

show abstract

“…While previous studies have focused on orogen-scale compatibility between deformational processes occurring within the midcrust in the deep orogenic hinterland and those processes occurring at higher structural levels in the orogenic shallower foreland (e.g., Price, 1972;Simony and Carr, 2011), more recent studies have documented similar kinematic compatibility at much smaller scales (e.g., Larson et al, 2010Larson et al, , 2011Larson et al, , 2013Yakymchuck and Godin, 2012). These types of studies, which integrate structural, metamorphic, and geochronologic data, provide a means by which to characterize the potentially distinct geologic histories of spatially adjacent rocks that may have evolved uniquely in initially separate regions of an orogen.…”

Section: Introductionmentioning

confidence: 99%

“…There has been much debate over which of the "end-member" models proposed for the evolution of the Himalaya, commonly considered to be wedge-taper processes or channel flow, best describes or explains available geologic data (see Beaumont and Jamieson, 2010;Larson et al, 2013). However, thermo-mechanical orogenic simulations (e.g., Jamieson et al, 2004) implicitly predict a change from lateral midcrustal flow in the orogenic hinterland to wedge-taper processes in the foreland of the orogen (Beaumont and Jamieson, 2010).…”

Section: Introductionmentioning

confidence: 99%

Metamorphism and geochronology of the exhumed Himalayan midcrust, Likhu Khola region, east-central Nepal: Recognition of a tectonometamorphic discontinuity

2014

View full text Add to dashboard Cite

The exhumed Himalayan midcrustal core exposed in the Likhu Khola region of east-central Nepal includes upper-greenschist-to upperamphibolite-grade metamorphic rocks that record pervasive, top-to-the-south sense deformation. Metamorphic temperature estimates are within error across the mapped area ranging from 772 ± 37 °C in the structurally lower, southern part of the study area to 853 ± 58 °C in the structurally higher, northern area. Estimated metamorphic pressures are relatively constant at lower structural levels, but they decrease from 11.8 ± 1.4 kbar to a minimum of 6.5 ± 1.3 kbar up structural section. The decrease in pressures coincides with an abrupt change in pressure estimates up structural section that is interpreted to mark a tectonometamorphic discontinuity that separates two domains with distinct structural, thermal, and metamorphic histories. In situ laser-ablation split-stream monazite U-Th/Pb and rare earth element (REE) petrochronology outlines dates ranging from ca. 27.8 Ma to 15.1 Ma in the hanging wall of the interpreted discontinuity; monazite REE data indicate the spread in ages is the result of a protracted metamorphic history and late-stage anatexis. Metamorphic and petrochronologic data from the Likhu Khola are consistent with a kinematic model in which material structurally above the discontinuity was metamorphosed in the deep hinterland of the orogen and was subsequently incorporated into the foreland of the orogen. The transition from hinterland-to foreland-style processes was marked by a shift to discrete deformation and the development of the discontinuity. Movement across the discontinuity is interpreted to have driven metamorphism and deformation of the rocks structurally below at or after 15 Ma. Discontinuities similar to that identified in this study are being identified and described across the orogen, indicating they are important, orogenwide features.

show abstract

A P–T–t–D discontinuity in east-central Nepal: Implications for the evolution of the Himalayan mid-crust

Cited by 82 publications

References 79 publications

Developing an inverted Barrovian sequence; insights from monazite petrochronology

Developing an inverted Barrovian sequence; insights from monazite petrochronology

Pressure–temperature–time–deformation path of kyanite-bearing migmatitic paragneiss in the Kali Gandaki valley (Central Nepal): Investigation of Late Eocene–Early Oligocene melting processes

Metamorphism and geochronology of the exhumed Himalayan midcrust, Likhu Khola region, east-central Nepal: Recognition of a tectonometamorphic discontinuity

Contact Info

Product

Resources

About