Tectonic interleaving along the Main Central Thrust, Sikkim Himalaya

Abstract

Geochemical and geochronological analyses provide quantitative evidence about the origin, development and motion along ductile faults, where kinematic structures have been overprinted. The Main Central Thrust is a key structure in the Himalaya that accommodated substantial amounts of the India-Asia convergence. This structure juxtaposes two isotopically distinct rock packages across a zone of ductile deformation. Structural analysis, whole-rock Nd isotopes, and u-Pb zircon geochronology reveal that the hanging wall is characterized by detrital zircon peaks at c.

Developing an inverted Barrovian sequence; insights from monazite petrochronology

“…10). This model is supported by evidence of tectonic interleaving of GHS and LHS protolith material in the Sikkim MCT zone (Mottram et al, 2014). We suggest that the thrust originally nucleated at the LHS-GHS protolith boundary.…”

“…The upper LHS samples (22, Takdah; 60, Mangan; and 30, Rongli), located near the GHS-LHS protolith boundary (Mottram et al, 2014), are kyanite-bearing schists. Sample 22 is described in detail; the other samples reached similar peak conditions and are described in supplementary material S2.…”

A review on out-of-sequence deformation in the Himalaya

“…The MCT zone in Sikkim, characterized by 'alternate shifts in epsilon Nd and zircon characters' suggests an out-of-sequence thrust (Mottram et al 2014), although again the timing of MCT activation is not clearly understood. On map view, one of the splays of the MCT cuts the latter and therefore defines an out-of-sequence thrust from the Darjeeling Himalaya (Searle & Szulc 2005).…”

Along-strike continuity of structure, stratigraphy, and kinematic history in the Himalayan thrust belt: The view from Northeastern India

“…As recently as the late 1990's the amounts of horizontal shortening, kinematic history, and fundamental chronostratigraphic aspects of Himalayan geology remained largely unknown, in part because of the ruggedness of the orogen but also because the rocks that constitute most of its southern half lack fossils and are thus difficult to date and correlate. Over the past 20 years two major breakthroughs have expanded the understanding of Himalayan geology: first, the application of detrital zircon U‐Pb geochronology and Sm/Nd and Lu/Hf isotope geochemistry allowed for orogen‐scale clarification of the ages and along‐strike correlations of Himalayan tectonostratigraphic units [ Parrish and Hodges , ; DeCelles et al ., , ; Whittington et al ., ; Ahmad et al ., ; Robinson et al ., ; Argles et al ., ; Richards et al ., , ; Martin et al ., ; Gehrels et al ., ; McQuarrie et al ., ; Mottram et al ., , and many other studies], and second, pursuing the path blazed by Coward and Butler [], geologists began to produce numerous regional‐scale balanced cross sections that allow estimation of crustal shortening and the kinematic history of major thrust faults along most of the strike length of the orogenic belt [ Schelling and Arita , ; Schelling , ; Srivastava and Mitra , ; Ratschbacher et al ., ; DeCelles et al ., , ; Corfield and Searle , ; Murphy and Yin , ; Pearson and DeCelles , ; Robinson et al ., ; Murphy , ; McQuarrie et al ., , ; Mitra et al ., ; Tobgay et al ., ; Yin et al ., ; Webb et al ., ; Long et al ., ; Khanal and Robinson , ; Webb , ; Robinson and Martin , ; Bhattacharyya et al ., ]. Together, these new approaches have catapulted our knowledge of Himalayan thrust belt shortening and kinematic history, with implications for crustal thickening throughout the Himalayan‐Tibetan orogenic system.…”

“…Together, these new approaches have catapulted our knowledge of Himalayan thrust belt shortening and kinematic history, with implications for crustal thickening throughout the Himalayan‐Tibetan orogenic system. As in all scientific endeavors, however, the new data raise new questions, and notable debates have emerged concerning along‐strike correlation of Himalayan stratigraphic units and tectonostratigraphic terranes [ DeCelles et al ., ; Myrow et al ., ; Richards et al ., ; Yin , ; McQuarrie et al ., ], the geometry and kinematics of the Main Central Thrust [ Yin , ; Webb et al ., , ; Searle et al ., ; Webb , ; Célérier et al ., ; He et al ., ; Larson et al ., ], the best way(s) to identify and map major Himalayan thrust faults (especially the Main Central Thrust [ Martin et al ., ; Richards et al ., ; Searle et al ., ; Webb et al ., ; Mottram et al ., ; Martin , ]), and the underlying geodynamic mechanisms driving deformation [ Burg et al ., ; Nelson et al ., ; Grujic et al ., ; Avouac , ; Beaumont et al ., , ; Jamieson et al ., ; Robinson and Pearson , ; Yin , ; Kellett et al ., ; He et al ., ].…”